Multiplex PCR for the detection of tetracycline resistant genes

Biodiversity and antibiotic resistance profile provide new evidence for a different origin of enterococci in bovine raw milk and feces

Enterococci are widely distributed in dairy sector. They are commensals of the gastrointestinal tract of animals, thus, via fecal contamination, could reach raw milk and dairy products. The aims of this study were: 1) to investigate the enterococcal diversity in cow feces and milk samples and 2) to evaluate the antibiotic resistance (AR) of dairy-related enterococci and their ability to transfer resistance genes. E. faecalis (59.9%), E. faecium (18.6%) and E. lactis (12.4%) were prevalent in milk, while E. faecium (84.2%) and E. hirae (15.0%) were dominant in bovine feces. RAPD-PCR highlighted a high number of Enterococcus biotypes (45 from milk and 37 from feces) and none of the milk strains exhibited genetic profiles similar to those of feces biotypes. A high percentage of enterococci isolated from milk (71%) were identified as multidrug resistant and resistance against streptomycin and tetracycline were widespread among milk strains while enterococci from feces were commonly resistant to linezolid and quinupristin/dalfopristin. Only E. faecalis strains were able to transfer horizontally the tetM gene to Lb. delbrueckii subsp. lactis. Our results indicated that Enterococcus biotypes from milk and bovine feces belong to different community and the ability of these microorganisms to transfer AR genes is strain-dependent.

Serovar and sequence type distribution and phenotypic and genotypic antimicrobial resistance of Salmonella originating from pet animals in Chongqing, China

A total of 334 Salmonella isolates were recovered from 6,223 pet rectal samples collected at 50 pet clinics, 42 pet shops, 7 residential areas, and 4 plazas. Forty serovars were identified that included all strains except for one isolate that did not cluster via self-agglutination, with Salmonella Typhimurium monophasic variant, Salmonella Kentucky, Salmonella Enteritidis, Salmonella Pomona, and Salmonella Give being the predominant serovars. Fifty-one sequence types were identified among the isolates, and ST198, ST11, ST19, ST451, ST34, and ST155 were the most common. The top four dominant antimicrobials to which isolates were resistant were sulfisoxazole, ampicillin, doxycycline, and tetracycline, and 217 isolates exhibited multidrug resistance. The prevalence of β-lactamase genes in Salmonella isolates was 59.6%, and among these isolates, 185 harbored blaTEM, followed by blaCTX-M (66) and blaOXA (10). Moreover, six PMQR genes, namely, including qnrA (4.8%), qnrB (4.2%), qnrD (0.9%), qnrS (18.9%), aac(6')-Ib-cr (16.5%), and oqxB (1.5%), were detected. QRDR mutations (76.6%) were very common in Salmonella isolates, with the most frequent mutation in parC (T57S) (47.3%). Furthermore, we detected six tetracycline resistance genes in 176 isolates, namely, tet(A) (39.5%), tet(B) (8.1%), tet(M) (7.7%), tet(D) (5.4%), tet(J) (3.3%), and tet(C) (1.8%), and three sulfonamide resistance genes in 303 isolates, namely, sul1 (84.4%), sul2 (31.1%), and sul3 (4.2%). Finally, we found 86 isolates simultaneously harboring four types of resistance genes that cotransferred 2-7 resistance genes to recipient bacteria. The frequent occurrence of antimicrobial resistance, particularly in dogs and cats, suggests that antibiotic misuse may be driving multidrug-resistant Salmonella among pets.IMPORTANCEPet-associated human salmonellosis has been reported for many years, and antimicrobial resistance in pet-associated Salmonella has become a serious public health problem and has attracted increasing attention. There are no reports of Salmonella from pets and their antimicrobial resistance in Chongqing, China. In this study, we investigated the prevalence, serovar diversity, sequence types, and antimicrobial resistance of Salmonella strains isolated from pet fecal samples in Chongqing. In addition, β-lactamase, QRDR, PMQR, tetracycline and sulfonamide resistance genes, and mutations in QRDRs in Salmonella isolates were examined. Our findings demonstrated the diversity of serovars and sequence types of Salmonella isolates. The isolates were widely resistant to antimicrobials, notably with a high proportion of multidrug-resistant strains, which highlights the potential direct or indirect transmission of multidrug-resistant Salmonella from pets to humans. Furthermore, resistance genes were widely prevalent in the isolates, and most of the resistance genes were spread horizontally between strains.

Multidrug resistant Vibrio spp. identified from mussels farmed for human consumption in Central Italy

AIMS

This study investigated phenotypic and genotypic antimicrobial resistance profiles of Vibrio strains identified from Mytilus galloprovincialis farmed for human consumption in the Adriatic Sea Central Italy.

METHODS AND RESULTS

A total of 475 mussels (M. galloprovincialis) were involved in the present study, and culture-dependent microbiological methods permitted to identify a total of 50 Vibrio strains that were tested for antibiotic susceptibility followed by the genetic determinant detections. Antibiograms showed resistance against ampicillin (36.0%), amoxicillin-clavulanic acid (30.0%), gentamycin (14.0%), and imipenem (18.0%). Biomolecular assays amplified a total of 264 antibiotic resistance genes harbored by both susceptible and resistant Vibrio species. Among resistance genes, aacC2 (62.0%) and aadA (58.0%) for aminoglycosides, blaTEM (54.0%) for beta-lactams, qnrS (24.0%) for quinolones, tetD (66.0%) for tetracyclines, and vanB (60.0%) for glycopeptides were mainly amplified by PCR assays.

CONCLUSIONS

Vibrio genus is involved in the antibiotic resistance phenomenon diffusion in the aquatic environments, as demonstrated by the harboring of many genetic determinants representing a kind of genetic "dark world".

Antibiotic susceptibility and resistance genes profiles of Vagococcus salmoninarum in a rainbow trout (Oncorhyncus mykiss, Walbaum) farm

Disease outbreaks negatively affect fish production. Antimicrobial agents used in the treatment of diseases become ineffective over time because of antibiotic resistance developed by bacteria distributed in the aquaculture environment. This study was conducted for 4 months (cold period) in a fish farm to detect the fish disease, cold water streptococcosis. In the study, four brood stock showing disease signs were detected. Bacteria isolates were obtained and identified as Vagococcus salmoninarum. Antimicrobial susceptibility of V. salmoninarum was tested and antibiotic resistance gene profiles of V. salmoninarum isolates were screened. The phylogenetic relation of the isolates with the previously reported strains was evaluated. Antibiotic resistance developed by pathogenic bacteria is distributed in the aquaculture environment. The transfer of resistance genes from one bacterium to another is very common. This situation causes the antimicrobial agents used in the treatment of diseases to become ineffective over time. The disc diffusion test showed that all four isolates developed resistance to 13 (FFC30, AX25, C30, E15, CF30, L2, OX1, S10, T30, CRO30, CC2, PT15 and TY15) of the evaluated antibiotics and were about to develop resistance to six others (AM 10, FM 300, CFP75, SXT25, APR15 and TE30). Furthermore, antibiotic resistance genes tetA, sul1, sul2, sul3, dhfr1, ereB and floR were detected in the isolated strain. Moreover, the phylogenetic analysis showed that isolated V. salmoninarum strain (ESN1) was closely related to the bacterial strains isolated from USA and Jura.

Tracking antimicrobial resistance indicator genes in wild flatfish from the English Channel and the North Sea area: A one health concern

Antimicrobial resistance (AMR) is a burgeoning environmental concern demanding a comprehensive One Health investigation to thwart its transmission to animals and humans, ensuring food safety. Seafood, housing bacterial AMR, poses a direct threat to consumer health, amplifying the risk of hospitalization, invasive infections, and death due to compromised antimicrobial treatments. The associated antimicrobial resistance genes (ARGs) in diverse marine species can amass and transmit through various pathways, including surface contact, respiration, and feeding within food webs. Our research, focused on the English Channel and North Sea, pivotal economic areas, specifically explores the occurrence of four proposed AMR indicator genes (tet(A), blaTEM, sul1, and intI1) in a benthic food web. Analyzing 350 flatfish samples' skin, gills, and gut, our quantitative PCR (qPCR) results disclosed an overall prevalence of 71.4% for AMR indicator genes. Notably, sul1 and intI1 genes exhibited higher detection in fish skin, reaching a prevalence of 47.5%, compared to gills and gut samples. Proximity to major European ports (Le Havre, Dunkirk, Rotterdam) correlated with increased AMR gene frequencies in fish, suggesting these ports' potential role in AMR spread in marine environments. We observed a broad dispersion of indicator genes in the English Channel and the North Sea, influenced by sea currents, maritime traffic, and flatfish movements. In conclusion, sul1 and intI1 genes emerge as robust indicators of AMR contamination in the marine environment, evident in seawater and species representing a benthic food web. Further studies are imperative to delineate marine species' role in accumulating and transmitting AMR to humans via seafood consumption. This research sheds light on the urgent need for a concerted effort in comprehending and mitigating AMR risks in marine ecosystems within the context of One Health.

Virulence determinants and antibiotic resistance in staphylococci isolated from the skin of captive bred reptiles

Knowledge of the composition and properties of skin microbiota in healthy reptiles is essential for preservation strategies and thus the prevention of skin dysbiosis leading to dermatological diseases. Despite the greatly increasing popularity of reptiles as pets, only a few studies have dealt with this topic. Therefore, the aim of this work was to analyse species composition of bacteria isolated from skin swabs of 40 reptiles (17 species) using MALDI-TOF spectrometry and to characterise the virulence properties of identified staphylococci (n = 51). The most common species were Staphylococcus xylosus and S. sciuri. Bacilli, enterococci, Escherichia coli, Salmonella sp. and Acinetobacter sp. were also common. The most frequent antimicrobial resistance in staphylococcal isolates was observed for ampicillin (100.0%) and cefoxitin (98.0%) with the blaZ gene being most prevalent (58.8%). In contrast, all staphylococci were susceptible to gentamicin, kanamycin and imipenem. Slime and biofilm production was observed in 86.3% and 76.5% of isolates, respectively. Gelatinase, DNase, protease and lipase activity was found more rarely (41.2%; 25.5%; 27.5% and 21.6%). Since reptiles are a reservoir of bacteria for their owners, common multi-drug resistance (84.3%, MAR index average 0.29 ± 0.09) and biofilm formation must be kept in mind, especially in the case of injury when handling reptiles.

Monitoring indicator genes to assess antimicrobial resistance contamination in phytoplankton and zooplankton communities from the English Channel and the North Sea

Phytoplankton and zooplankton play a crucial role in marine ecosystems as the basis of the food webs but are also vulnerable to environmental pollutants. Among emerging pollutants, antimicrobial resistance (AMR) is a major public health problem encountered in all environmental compartments. However, the role of planktonic communities in its dissemination within the marine environment remains largely unexplored. In this study, we monitored four genes proposed as AMR indicators (tetA, blaTEM, sul1, and intI1) in phytoplankton and zooplankton samples collected in the English Channel and the North Sea. The indicator gene abundance was mapped to identify the potential sources of contamination. Correlation was assessed with environmental parameters to explore the potential factors influencing the abundance of AMR in the plankton samples. The prevalence in phytoplankton and zooplankton of sul1 and intI1, the most quantified indicator genes, ranged from 63 to 88%. A higher level of phytoplankton and zooplankton carrying these genes was observed near the French and English coasts in areas subjected to anthropogenic discharges from the lands but also far from the coasts. Correlation analysis demonstrated that water temperature, pH, dissolved oxygen and turbidity were correlated to the abundance of indicator genes associated with phytoplankton and zooplankton samples. In conclusion, the sul1 and intI1 genes would be suitable indicators for monitoring AMR contamination of the marine environment, either in phytoplankton and zooplankton communities or in seawater. This study fills a part of the gaps in knowledge about the AMR transport by marine phytoplankton and zooplankton, which may play a role in the transmission of resistance to humans through the marine food webs.

Municipal wastewater treatment plant showing a potential reservoir for clinically relevant MDR bacterial strains co-occurrence of ESBL genes and integron-integrase genes

Municipal wastewater treatment plants (MWWTPs) are a milieu for co-occurrence of multiple antibiotic resistance genes (ARGs). This facilitates mixing and genetic exchange; and promotes dissemination of multidrug resistance (MDR) to wastewater bacterial communities which is hazardous for the effluent receiving environment. This study investigated the co-occurrence of extended-spectrum beta-lactamase (ESBL) genes (blaTEM, blaCTX-M, blaSHV, blaOXA), and integron-integrase genes (intI1, intI2, intI3) in MDR bacteria isolated from the Bharwara MWWTP in Lucknow, India. Thirty-one MDR bacterial colonies resistant to three or more antibiotics were isolated from three treatment stages of this MWWTP. Six of these: Staphylococcus aureus, Serratia marcescens, Salmonella enterica, Shigella sonnei, Escherichia coli, and Bacillus sp. Had co-occurrence of ESBL and integron-integrase genes. These six isolates were examined for the occurrence of MDR efflux genes (qacA, acrB) and ARGs (aac(3)-1, qnrA1, tetA, vanA) and tested for resistance against 12 different antibiotics. The highest resistance was against penicillin-G (100%) and lowest for chloramphenicol (16.66%). Bacillus sp. Isolate BWKRC6 had the highest co-occurrence of antibiotic resistance-determining genes and was resistant to all the 12 antibiotics tested. The co-occurrence of ESBL, integron-integrase, antibiotic resistance-determining and MDR efflux genes in bacteria isolated from the Bharwara MWWTP indicates that the wastewaters of this treatment plant may have become a hotspot for MDR bacteria and may present human and environmental health hazards. Therefore, there is need for a rapid action to limit the spread of this threat. Public regulatory authorities must urgently implement measures to prevent MWWTPs becoming reservoirs for evolution of antibiotic resistance genes and development of antibiotic resistance.

Microbiological Quality and Antimicrobial Resistance of Commercial Probiotic Products for Food-Producing Animals

Probiotics have been popularly used in livestock production as an alternative to antibiotics. This study aimed to investigate the microbiological quality and phenotypic and genotypic antimicrobial resistance of bacteria in probiotic products sold for food animals. A total of 45 probiotic products were examined for the number of viable cells, species, and antimicrobial susceptibility; the contamination of Escherichia coli and Salmonella; and the presence of 112 genes encoding resistance to clinically important antimicrobials and transferability of AMR determinants. The results showed that 29 of 45 products (64.4%) were incorrectly labeled in either number of viable cells or bacterial species. None of the tested products were contaminated with E. coli and Salmonella. A total of 33 out of 64 bacterial isolates (51.6%) exhibited resistance to at least one antimicrobial agent. Of the 45 products tested, 16 (35.5%) carried AMR genes. Almost all AMR genes detected in probiotic products were not correlated to the AMR phenotype of probiotic strains formulated in the products. Three streptomycin-resistant Lactobacillus isolates could horizontally transfer their AMR determinants. The findings demonstrated that the probiotic products could serve as reservoirs for the spread of AMR genes and may not yield benefits to animals as claimed. The need for the adequate quality control of probiotic products is highlighted.

Prevalence and antimicrobial resistance of Enterococcus spp. isolated from animal feed in Japan

The rising prevalence of antimicrobial resistance (AMR) of bacteria is a global health problem at the human, animal, and environmental interfaces, which necessitates the "One Health" approach. AMR of bacteria in animal feed are a potential cause of the prevalence in livestock; however, the role remains unclear. To date, there is limited research on AMR of bacteria in animal feed in Japan. In this study, a total of 57 complete feed samples and 275 feed ingredient samples were collected between 2018 and 2020. Enterococcus spp. were present in 82.5% of complete feed (47/57 samples), 76.5% of soybean meal (62/81), 49.6% of fish meal (55/111), 33.3% of poultry meal (22/66), and 47.1% of meat and bone meal (8/17) samples. Of 295 isolates, E. faecium (33.2% of total isolates) was the dominant Enterococcus spp., followed by E. faecalis (14.2%), E. hirae (6.4%), E. durans (2.7%), E. casseliflavus (2.4%), and E. gallinarum (1.0%). Of 134 isolates which were tested for antimicrobial susceptibility, resistance to kanamycin was the highest (26.1%), followed by erythromycin (24.6%), tetracycline (6.0%), lincomycin (2.2%), tylosin (1.5%), gentamicin (0.8%), and ciprofloxacin (0.8%). All Enterococcus spp. exhibited susceptibility to ampicillin, vancomycin, and chloramphenicol. Of 33 erythromycin-resistant isolates, only two showed a high minimum inhibitory concentration value (>128 μg/mL) and possessed ermB. These results revealed that overall resistance to antimicrobials is relatively low; however, animal feed is a source of Enterococcus spp. It is essential to elucidate the causative factors related to the prevalence of AMR in animal feed.

Diversity of antibiotic resistance gene variants at subsequent stages of the wastewater treatment process revealed by a metagenomic analysis of PCR amplicons

Wastewater treatment plants have been recognised as point sources of various antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG) which are considered recently emerging biological contaminants. So far, culture-based and molecular-based methods have been successfully applied to monitor antimicrobial resistance (AMR) in WWTPs. However, the methods applied do not permit the comprehensive identification of the true diversity of ARGs. In this study we applied next-generation sequencing for a metagenomic analysis of PCR amplicons of ARGs from the subsequent stages of the analysed WWTP. The presence of 14 genes conferring resistance to different antibiotic families was screened by PCR. In the next step, three genes were selected for detailed analysis of changes of the profile of ARG variants along the process. A relative abundance of 79 variants was analysed. The highest diversity was revealed in the ermF gene, with 52 variants. The relative abundance of some variants changed along the purification process, and some ARG variants might be present in novel hosts for which they were currently unassigned. Additionally, we identified a pool of novel ARG variants present in the studied WWTP. Overall, the results obtained indicated that the applied method is sufficient for analysing ARG variant diversity.

Concentrations, distribution, and key influencing factors of antibiotic resistance genes and bacterial community in water and reared fish tissues in a typical tilapia farm in South China

Although previous studies have investigated the occurrence of antibiotic resistance genes (ARGs) in aquaculture, few have monitored the concentrations and propagation of ARGs in biological tissues or investigated the key factors influencing their spread in aquaculture. This study investigated the concentration, propagation, and distribution of ARGs and bacterial communities in water sources, pond water, and tilapia tissues, and their key influencing factors, in a typical tilapia farm. ErmF, sul1, and sul2 were the dominant ARGs with high concentrations. The total concentrations of ARGs (TCAs) in tilapia tissues decreased in the following order: stomach > scales > intestine > gills (P < 0.05). Redundancy analysis and multiple linear regression revealed that suspended solids (SS) and chemical oxygen demand (COD) were positively correlated with the dominant ARGs ermF sul2, and the TCAs (P < 0.05); additionally, Chloroflexi and Bacteroidetes in tilapia aquaculture water were positively correlated with the dominant ARGs ermF and sul2, as well as the TCAs (P < 0.05). This study suggests that SS and COD were the key factors driving the distribution and spread of ARGs in tilapia aquaculture water. Additionally, Chloroflexi and Bacteroidetes were the key bacterial flora affecting the propagation of ARGs in tilapia aquaculture systems.

Antimicrobial resistance genes in a golden jackal (Canis aureus L. 1758) from Central Italy

In recent years an increasing interest has been focused on the contribution of wildlife in ecology and evolution of the antimicrobial resistance (AMR). The aim of this study was to molecularly investigate the presence of antimicrobial resistance genes (ARGs) in organ samples from a golden jackal (Canis aureus) found dead in the Marche region (Central Italy). Samples from lung, liver, spleen, kidney, and intestine were investigated by PCRs targeting the following genes: tet(A), tet(B), tet(C), tet(D), tet(E), tet(G), tet(K), tet(L), tet(M), tet(O), tet(S), tet(P), tet(Q), tet(X), sul1, sul2, sul3, blaCTX-M, blaSHV, blaTEM, and mcr-1 to mcr-10. One or more ARGs were detected in all organs tested, except the spleen. Specifically, the lung and liver were positive for tet(M) and tet(P), the kidney for mcr-1 and the intestine for tet(A), tet(L), tet(M), tet(O), tet(P), sul3 and blaTEM-1. These results, according to the opportunistic foraging strategy of the jackal, confirm its potential role as a good bioindicator of AMR environmental contamination.

Antibiotic resistance gene-free probiont administration to tilapia for growth performance and Streptococcus agalactiae resistance

Background and Aim

The rapid development of aquaculture as a major food sector is accompanied by challenges, including diseases that affect tilapia farming worldwide. One such infectious disease caused by Streptococcus agalactiae poses a serious threat to tilapia populations. Probiotics have emerged as a potentially safe preventive measure against S. agalactiae infection. However, antimicrobial resistance from antibiotic-resistant bacteria remains a concern because it can lead to the spread of resistant bacteria and serve as a reservoir of antibiotic-resistant genes in fishes and the surrounding environment. This study aimed to identify candidate probiotic bacteria capable of promoting tilapia growth, providing resistance to S. agalactiae infection, devoid of potential pathogenicity, and free from antibiotic resistance genes. Subsequently, the performance of these probiotic candidates in tilapia was evaluated.

Materials and Methods

Lactococcus garvieae, Priestia megaterium, Bacterium spp., Bacillus megaterium, Bacillus subtilis, and Bacillus pumilus were examined to assess their antibacterial properties, hemolytic patterns, and antibiotic resistance genes. We used the specific primers tetA, tetB, tetD, tetE, tetO, tetQ, ermB, and qnrS that were used for antibiotic resistance gene detection. In vivo probiotic efficacy was evaluated by administering probiotic candidates in tilapia feed at a concentration of 1 × 106 colonies/mL/50 g of feed over a 60-day maintenance period. Resistance to S. agalactiae infection was observed for 14 days after the challenge test.

Results

Lactococcus garvieae, P. megaterium, and Bacterium spp. were identified as promising probiotic candidates among the bacterial isolates. On the other hand, B. megaterium, B. subtilis, and B. pumilus carried resistance genes and exhibited a β hemolytic pattern, rendering them unsuitable as probiotic candidates. The selected probiotic candidates (L. garvieae, P. megaterium, and Bacterium spp.) demonstrated the potential to enhance tilapia growth, exhibited no pathogenic tendencies, and were free from antibiotic resistance genes. Supplementation with L. garvieae and Bacterium spp. enhanced tilapia resistance to S. agalactiae infection, whereas P. megaterium supplementation showed an insignificant survival rate compared with controls after the challenge test period.

Conclusion

Probiotics, particularly L. garvieae, P. megaterium, and Bacterium spp., enhance growth and resistance against S. agalactiae infection, without harboring antibiotic resistance genes. Selecting probiotic candidates based on antibiotic resistance genes is essential to ensure the safety of fish, the environment, and human health.

Impact of In-Feed versus In-Water Chlortetracycline and Tiamulin Administrations on Fecal Prevalence and Antimicrobial Susceptibilities of Campylobacter in a Population of Nursery Pigs

Antimicrobial resistance (AMR) in bacteria is a major public health concern in the US and around the world. Campylobacter is an important foodborne pathogen that resides in the gut of pigs and is shed in feces, with the potential to be transmitted to humans. In pigs, the oral route, either in-feed or in-water, is by far the most common route of administration of antimicrobials. Because the distribution of the antibiotic in the gut and the dosages are different, the impact of in-feed vs. in-water administration of antibiotics on the development of AMR is likely to be different. Therefore, a study was conducted to compare in-feed vs. in-water administrations of chlortetracycline (CTC) and/or tiamulin on fecal prevalence and AMR profiles of Campylobacter among weaned nursery piglets. A total of 1,296 weaned piglets, allocated into 48 pens (27 piglets per pen), were assigned randomly to six treatment groups: Control (no antibiotic), in-feed CTC, in-water CTC, in-feed tiamulin, in-water tiamulin, or in-feed CTC and tiamulin. Fecal samples were collected randomly from 5 piglets from each pen during the pre-treatment (days 0, 7), treatment (days 14, 21), and post-treatment (days 28, 35) phases. Bacterial isolations and species identifications were conducted by culture and PCR, respectively. The microbroth dilution method with SensititreTM plates was used to determine the antimicrobial susceptibility and resistance of Campylobacter isolates. The results on resistance were interpreted based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) epidemiological cutoff values for Campylobacter. The overall prevalence of Campylobacter was 18.2% (262/1440). Speciation of Campylobacter isolates by PCR indicated the prevalence of only two species: Campylobacter hyointestinalis (17.9%; 258/1440) and C. coli (0.3%; 4/1440). Campylobacter isolates were resistant to tetracycline (98.5%), ciprofloxacin (89.3%), and nalidixic acid (60.3%). Neither the antibiotic nor the route of administration had an effect (p > 0.05) on the prevalence of AMR Campylobacter in the feces of piglets.

Traditional marketed meats as a reservoir of multidrug-resistant Escherichia coli

This study aimed to analyze Escherichia coli from marketed meat samples in Peru. Sixty-six E. coli isolates were recovered from 21 meat samples (14 chicken, 7 beef), and antimicrobial resistance levels and the presence of mechanisms of antibiotic resistance, as well as clonal relationships and phylogeny of colistin-resistant isolates, were established. High levels of antimicrobial resistance were detected, with 93.9% of isolates being multi-drug resistant (MDR) and 76.2% of samples possessing colistin-resistant E. coli; of these, 6 samples from 6 chicken samples presenting mcr-1-producer E. coli. Colistin-resistant isolates were classified into 22 clonal groups, while phylogroup A (15 isolates) was the most common. Extended-spectrum β-lactamase- and pAmpC-producing E. coli were found in 18 and 8 samples respectively, with blaCTX-M-55 (28 isolates; 16 samples) and blaCIT (8 isolates; 7 samples) being the most common of each type. Additionally, blaCTX-M-15, blaCTX-M-65, blaSHV-27, blaOXA-5/10-like, blaDHA, blaEBC and narrow-spectrum blaTEM were detected. In addition, 5 blaCTX-M remained unidentified, and no sought ESBL-encoding gene was detected in other 6 ESBL-producer isolates. The tetA, tetE and tetX genes were found in tigecycline-resistant isolates. This study highlights the presence of MDR E. coli in Peruvian food-chain. The high relevance of CTX-M-55, the dissemination through the food-chain of pAmpC, as well as the high frequency of unrelated colistin-resistant isolates is reported.

Assessing the Effect of Oxytetracycline on the Selection of Resistant Escherichia coli in Treated and Untreated Broiler Chickens

Oxytetracycline (OTC) is administered in the poultry industry for the treatment of digestive and respiratory diseases. The use of OTC may contribute to the selection of resistant bacteria in the gastrointestinal tract of birds or in the environment. To determine the effect of OTC on the selection of resistant Escherichia coli strains post-treatment, bacteria were isolated from droppings and litter sampled from untreated and treated birds. Bacterial susceptibility to tetracyclines was determined by the Kirby-Bauer test. A total of 187 resistant isolates were analyzed for the presence of tet(A), (B), (C), (D), (E), and (M) genes by PCR. Fifty-four strains were analyzed by PFGE for subtyping. The proportion of tetracycline-resistant E. coli strains isolated was 42.88%. The susceptibility of the strains was treatment-dependent. A high clonal diversity was observed, with the tet(A) gene being the most prevalent, followed by tet(C). Even at therapeutic doses, there is selection pressure on resistant E. coli strains. The most prevalent resistance genes were tet(A) and tet(C), which could suggest that one of the main mechanisms of resistance of E. coli to tetracyclines is through active efflux pumps.

Genetic characterization of a multidrug-resistant Salmonella enterica serovar Agona isolated from a dietary supplement in Germany

Salmonella enterica subsp. enterica serovar Agona has a history of causing food-borne outbreaks and any emergence of multidrug-resistant (MDR) isolates in novel food products is of concern. Particularly, in food products frequently consumed without sufficient heating prior to consumption. Here, we report about the MDR isolate, 18-SA00377, which had been isolated from a dietary supplement in Germany in 2018 and submitted to the German National Reference Laboratory for Salmonella. WGS-based comparative genetic analyses were conducted to find a potential reservoir of the isolate itself or mobile genetic elements associated with MDR. As a phylogenetic analysis did not yield any closely related S. Agona isolates, either globally or from Germany, a detailed analysis of the largest plasmid (295,499 bp) was performed as it is the main carrier of resistances. A combined approach of long-read and short-read sequencing enabled the assembly of the isolate's chromosome and its four plasmids. Their characterization revealed the presence of 23 different antibiotic resistance genes (ARGs), conferring resistance to 12 different antibiotic drug classes, as well as genes conferring resistance to six different heavy metals. The largest plasmid, pSE18-SA00377-1, belongs to the IncHI2 plasmid family and carries 16 ARGs, that are organized as two distinct clusters, with each ARG associated with putative composite transposons. Through a two-pronged approach, highly similar plasmids to pSE18-SA00377-1 were identified in the NCBI database and a search for Salmonella isolates with a highly similar ARG resistance profile was conducted. Mapping and structural comparisons between pSE18-SA00377-1 and these plasmids and Salmonella isolates showed that both the plasmid backbone and identical or similar ARG clusters can be found not only in Salmonella isolates, originating mostly from a wide variety of livestock, but also in a diverse range of bacterial genera of varying geographical origins and isolation sources. Thus, it can be speculated that the host range of pSE18-SA00377-1 is not restricted to Salmonella and its spread already occurred in different bacterial populations. Overall, this hints at a complex history for pSE18-SA00377-1 and highlights the importance of surveilling multidrug-resistant S. enterica isolates, especially in novel food items that are not yet heavily regulated.

Virulence gene profiles and antimicrobial susceptibility of Salmonella Brancaster from chicken

BACKGROUND

The current conventional serotyping based on antigen-antisera agglutination could not provide a better understanding of the potential pathogenicity of Salmonella enterica subsp. enterica serovar Brancaster. Surveillance data from Malaysian poultry farms indicated an increase in its presence over the years.

OBJECTIVE

This study aims to investigate the virulence determinants and antimicrobial resistance in S. Brancaster isolated from chickens in Malaysia.

METHODS

One hundred strains of archived S. Brancaster isolated from chicken cloacal swabs and raw chicken meat from 2017 to 2022 were studied. Two sets of multiplex polymerase chain reaction (PCR) were conducted to identify eight virulence genes associated with pathogenicity in Salmonella (invasion protein gene [invA], Salmonella invasion protein gene [sipB], Salmonella-induced filament gene [sifA], cytolethal-distending toxin B gene [cdtB], Salmonella iron transporter gene [sitC], Salmonella pathogenicity islands gene [spiA], Salmonella plasmid virulence gene [spvB], and inositol phosphate phosphatase gene [sopB]). Antimicrobial susceptibility assessment was conducted by disc diffusion method on nine selected antibiotics for the S. Brancaster isolates. S. Brancaster, with the phenotypic ACSSuT-resistance pattern (ampicillin, chloramphenicol, streptomycin, sulphonamides, and tetracycline), was subjected to PCR to detect the corresponding resistance gene(s).

RESULTS

Virulence genes detected in S. Brancaster in this study were invA, sitC, spiA, sipB, sopB, sifA, cdtB, and spvB. A total of 36 antibiogram patterns of S. Brancaster with a high level of multidrug resistance were observed, with ampicillin exhibiting the highest resistance. Over a third of the isolates displayed ACSSuT-resistance, and seven resistance genes (β-lactamase temoneira [blaTEM], florfenicol/chloramphenicol resistance gene [floR], streptomycin resistance gene [strA], aminoglycoside nucleotidyltransferase gene [ant(3″)-Ia], sulfonamides resistance gene [sul-1, sul-2], and tetracycline resistance gene [tetA]) were detected.

CONCLUSION

Multidrug-resistant S. Brancaster from chickens harbored an array of virulence-associated genes similar to other clinically significant and invasive non-typhoidal Salmonella serovars, placing it as another significant foodborne zoonosis.

Antimicrobial resistance profiles of salmonella spp. and escherichia coli isolated from fresh nile tilapia (oreochromis niloticus) fish marketed for human consumption

BACKGROUND

Salmonella spp. and pathogenic strains of Escherichia coli are among the major foodborne zoonotic pathogens. These bacterial pathogens cause human illnesses characterized by hemorrhagic colitis, vomiting, nausea, and other agent-related symptoms. The increasing occurrence of antimicrobial resistance in these pathogens is also a serious public health concern globally. Regular surveillance of phenotypes and genotypes of Salmonella spp. and Escherichia coli from animal-derived foods is necessary for effective reduction and control of these foodborne pathogens. This study was conducted to assess the occurrence, antimicrobial resistance, virulence genes and genetic diversity of Salmonella spp. and E. coli isolates from fresh Nile tilapia obtained from retail markets in Nairobi, Kenya.

METHODS

A total of 68 fresh Nile tilapia fish samples were collected from retail markets and used for isolation of Salmonella spp. and E. coli. Antimicrobial susceptibilities of the isolates weretested by Kirby-Bauer agar disc diffusion method. According to the antimicrobial resistance profiles, the multi-drug resistant isolates were identified by 16 S rRNA sequencing and phylogenetic analysis using the Bayesian inference method. The MDR Salmonella spp. and E. coli isolates were subjected to PCR-based screening for the detection virulence and antibiotic resistance genes.

RESULTS

The prevalence of contamination of the fish samples with Salmonella spp. and E.coli was 26.47% and 35.29% respectively. Overall phenotypic resistance among the Salmonella spp. ranged from 5.5% for ceftazidime, chloramphenicol, meropenem, nitrofurantoin and streptomycin and 22.2% for penicillin-G. For E. coli phenotypic resistance ranged from 4.2% for ceftazidime and chloramphenicol and 25% for rifampicin. Multi-drug resistance was observed in three Salmonella spp. and two E. coli isolates. Results of 16 S rRNA sequences, sequence alignment and phylogenic trees confirmed the identified MDR isolates as S. typhymurium WES-09, S. typhymurium MAK-22, S. typhimurium EMB-32 and E. coli MAK-26 and E. coli LAN-35. The presence of antibiotic-resistance genes belonging to β-lactamases, tetracycline, sulfonamide, trimethoprim and aminoglycosides-resistant genes were detected in all the identified MDR isolates.

CONCLUSIONS

The findings from this study indicate that Nile tilapia (Oreochromis niloticus) sold in retail markets can acts as reservoirs of Salmonella spp. and E. coli pathogens linked to human disease, some of which were multidrug resistance to critically important antimicrobials. Both microorganisms are of zoonotic significance and represent a significant public health risk to the society.

Occurrence of Antibiotic-Resistant Bacteria in Fish and Seafood from Slovak Market

The consumption of sushi or poke has grown globally. However, this type of dish often contains raw fish or seafood; therefore, it can pose a microbial risk for consumers. This study deals with the occurrence of total and antibiotic-resistant coliform bacteria and enterococci in fish and seafood as well as sushi and poke bought from Slovak retail (restaurants and fast food). Total coliforms have ranged in sushi, poke samples and samples of fish and seafood from cooling counters from 0.6 to 5.1 log CFU/g. Ampicillin resistance has been predominantly observed in all types of samples. Tetracycline resistance was detected in 16% of all tested samples and gentamicin resistance in 13%. Total enterococci has been detected in 74% of sushi samples, 100% of poke samples and 62% of samples obtained from supermarkets. The majority of enterococci were resistant to ampicillin. Vancomycin resistance was observed in five samples. Forty-eight resistant coliforms were identified mainly as Enterobacter spp. and Klebsiella spp. Antibiotic-resistant isolates were predominantly resistant to gentamicin, chloramphenicol and tetracycline. In 13% of resistant isolates was detected efflux pumps overproduction, and in four isolates was detected the tetA resistance gene. Our results point to poor hygiene in some establishments. The prevention of the antibiotic-resistant bacteria spread would be in better stewardship and improved monitoring of sanitation.

Molecular Characterisation of Antimicrobial Resistance in E. coli Isolates from Piglets in the West Region of Romania

Antibiotics are widely used for prophylaxis and therapy, reducing morbidity and mortality produced by bacterial pathogensin pigs, including infections caused by Escherichia coli. The aim of this study was to characterise antibiotic resistance phenotypes and genotypes in E. coli isolates in pigs in West Romanian grower farms. Differential phenotypic susceptibility profiles and the contribution of resistance genes to phenotypic expression of susceptibility or resistance were evaluated. A total of 76 E. coli isolates were identified and confirmed by the MicroScan Walk Away System. The occurrence of four resistance genes, ampC, blaZ, blaTEM and tetK in strains resistant to 13 antibiotics was assessed. Of the E. coli isolates, 0% showed resistance to meropenem, 3.9% to tigecycline and 10.5% to piperacillin/tazobactam, whereas, in contrast, 100% were resistant to ampicillin and mezlocillin, 76.31% to piperacillin and 59.3% to tetracycline. The prevalence of resistance genes in resistant isolates detected by q-PCR analysis was 97.0% for ampC, 96% for blaZ, 32.9% for blaTEM and 58.8% for tetK. Penetrance (the proportion of individuals carrying a particular variant of a gene that also expresses an associated trait) was 50% for ampC (32% for amoxicillin/clavulanate, 62% for cefazolin, 32% for cefepime, 100% for cefotaxime, 56% for cefuroxime and 99% for ampicillin), 65% for blaZ (32% for amoxicillin/clavulanate and 99% for ampicillin), 51% for blaTEM (81% for piperacillin) and 44% for the tetK gene (83% for tetracycline). The result of phenotypic antibiotic resistance testing may indicate the presence of plasmid-borne resistance, with a diagnostic odds ratio of a positive phenotypic resistance for tetK being 4.52. As a management decision, the maximum penetrance admitted for using a specific antibiotic for E. coli infections in pigs is recommended to be less than 20%.

Unravelling the resilience of magnetite assisted granules to starvation and oxytetracycline stress

Starvation and antibiotics pollution are two frequent perturbations during breeding wastewater treatment process. Supplying magnetite into anaerobic system has been proved efficient to accelerate microbial aggregates and alleviate the adverse effect caused by process disturbance. Nevertheless, whether these magnetite-based granules are still superior over normal granules after a long-term starvation period remains unknown, the responsiveness of these granules to antibiotics stress is also ambiguous. In current study, we investigated the resilience of magnetite-based anaerobic granular sludge (AnGS) to starvation and oxytetracycline (OTC) stress, by unravelling the variations of reactor performance, sludge properties, ARGs dissemination and microbial community. Compared with the AnGS formed without magnetite, the magnetite assisted AnGS appeared more robust defense to starvation and OTC stress. With magnetite supplement, the average methane yield after starvation recovery, 50 mg/L and 200 mg/L OTC stress was enhanced by 48.95%, 115.87% and 488.41%, respectively, accompanied with less VFAs accumulation, improved tetracycline removal rate (76.3-86.6% vs. 51.0-53.5%) and higher ARGs reduction. Meanwhile, magnetite supplement effectively ameliorated the potential sludge breakage by triggering more large granules formation. Trichococcus was considered an important impetus in maintaining the stability of magnetite-based AnGS process. By inducing more syntrophic methanogenesis partnerships, especially for hydrogenotrophic methanogenesis, magnetite ensured the improved reactor performance and stronger resilience at stress conditions.

Exploring the complex role of gut microbiome in the development of precision medicine strategies for targeting microbial imbalance-induced colon cancer

The gut microbiome has been increasingly recognized as a key player in the development and progression of colon cancer. Alterations in the gut microbiota, known as dysbiosis, can lead to a variety of medical issues. Microbial adaptation through signals and small molecules can enhance pathogen colonization and modulate host immunity, significantly impacting disease progression. Quorum sensing peptides and molecules have been linked to the progression of colon cancer. Various interventions, such as fecal microbiota transplantation, probiotics, prebiotics, synbiotics, and antibiotics, have been used to reverse dysbiosis with mixed results and potential side effects. Thus, a personalized approach to treatment selection based on patient characteristics, such as individual gut microbiota manipulation, is necessary to prevent and treat diseases like colon cancer. With advances in metagenomic sequencing and other omics technologies, there has been a growing interest in developing precision medicine strategies for microbial imbalance-induced colon cancer. This review serves as a comprehensive synthesis of current knowledge on the gut microbiome involvement in colon cancer. By exploring the potential of utilizing the gut microbiome as a target for precision medicine, this review underscores the exciting opportunities that lie ahead. Although challenges exist, the integration of microbiome data into precision medicine approaches has the potential to revolutionize the management of colon cancer, providing patients with more personalized and effective treatment options.

Evaluation of Streptococcus species isolated from subclinical sheep mastitis by molecular methods and determination of virulence factors and antimicrobial resistance genes

Streptococcus (S.) species are important pathogens that cause mastitis in sheep. The study aimed to examine Streptococcus species in sheep milk with subclinical mastitis, assessing their prevalence, antimicrobial resistance, and virulence genes. A total of 200 milk samples were collected from sheep farms in İzmir's five districts. Out of 32 (28.6%) Streptococcus isolates identified by phenotypic methods, 25 were genotypically identified as S. uberis, 5 as S. agalactiae, and 2 as S. dysgalactiae. Disk diffusion was used to determine the antimicrobial resistance of the isolates. PCR was employed to identify antimicrobial resistance and virulence genes in the isolates. The highest resistance was found for cloxacillin (100%), and the highest sensitivity was found for florfenicol (84%). The most common resistance gene combination was tetM+tetS (3/32) for S. uberis in 9.4%. A total of five virulence genes were detected. GapC+sua (56.2%) constituted the most common gene pattern. The highest virulence gene gapC was detected in 78.1% (25/32) of the isolates. The cylE gene was not detected (0%) in the isolates. Streptococcus species may play a role in mastitis in sheep, emphasising the need for meticulous hygienic milking practices.

Detection of tetracycline resistance genes and their diversity in Escherichia coli isolated from pig farm waste in Banten province, Indonesia

Background and Aim

Livestock waste in the form of feces and liquid represents an important reservoir of antibiotic resistance genes (ARGs). Because many ARGs can be horizontally transferred to other pathogens, livestock waste plays an essential role in the emergence and transmission of various ARGs in the environment. Therefore, this study aimed to detect and assess the diversity of tet genes in Escherichia coli isolated from pig farm waste in Banten province, Indonesia.

Materials and Methods

Solid waste (feces) and wastewater were collected from 44 pig farms in Banten province. The isolation and identification of E. coli referred to the Global Tricycle Surveillance extended-spectrum beta-lactamase E. coli World Health Organization (2021) guidelines. tet genes were detected using quantitative real-time polymerase chain reaction after dividing pig farms in the province into four clusters based on their adjacent areas and characteristics.

Results

tetA, tetB, tetC, tetM, tetO, and tetX were detected in solid waste and wastewater from pig farms, whereas tetE was not detected in either sample type. tetX (100%) and tetO (75%) were the most dominant genes in solid waste, whereas wastewater samples were dominated by tetA, tetM, tetO, and tetX (prevalence of 50% each). Furthermore, eight tet gene patterns were found in pig farm waste (prevalence of 12.5% each).

Conclusion

The results showed a high prevalence of tetO and tetX in solid waste and wastewater from pig farms in Banten province. This significant prevalence and diversity indicated the transmission of tet genes from pigs to the environment, posing a serious threat to public health.

Biofilm formation, antimicrobial resistance genes, and genetic diversity of Salmonella enterica subspecies enterica serotype Enteritidis isolated from food and animal sources in Iran

OBJECTIVES

Salmonella enterica serovar Entritidis is an important pathogen in foodborne diseases and causes gastroenteritis. Several studies have investigated the genetic diversity of the strains of this bacterium. However, our knowledge of the discriminatory power of the molecular methods is limited.

METHODS

In total, 34 strains of S. enteritidis were isolated from food related to animals. Antibiotic resistance of the strains, antibiotic resistance genes, and biofilm formation capacity of the strains were evaluated. For the genetic analysis of the strains, PFGE was performed using AvrII restriction enzyme.

RESULTS

Among the tested antibiotics, cefuroxime, nalidixic acid, and ciprofloxacin showed the highest resistance rates (79.4%, 47%, and 44.2%, respectively). Only three antibiotic-resistance genes were identified in these strains (blaTEM: 67.6%, tetA: 9%, and sul2: 3%). In total, 91% of the strains were biofilm producers. Clustering of strains using AvrII for 26 samples with the same XbaI PFGE profile showed that these strains were in one clone and had high homogeneity.

CONCLUSIONS

In conclusion, it is better to use a combination of several typing methods for typing strains that are genetically very close so that the results are reliable.

The manganese carbonyl complex [Mn(CO)3(tqa-κ3N)]Br: A novel antimicrobial agent with the potential to treat avian pathogenic Escherichia coli (APEC) infections

The development of alternatives to antibiotics is essential for the treatment of animal infections and as a measure to reduce the selective pressure on antibiotics that are critical for human medicine. Metal complexes have been highlighted for their antimicrobial activity against several bacterial pathogens. In particular, manganese carbonyl complexes have shown efficacy against multidrug-resistant Gram-negative pathogens, and relatively low cytotoxicity against avian macrophages and in wax moth larval models. They are thus potential candidates for deployment against Avian Pathogenic Escherichia coli (APEC), the aetiological agent of avian colibacillosis, which results in severe animal welfare issues and financial losses worldwide. This study aimed to determine the efficacy of [Mn(CO)3(tqa-κ3N)]Br in Galleria mellonella and chick models of infection against APEC. The results demonstrated in vitro and in vivo antibacterial activity against all antibiotic-resistant APEC test isolates screened in the study.

Occurrence of antimicrobial-resistant Staphylococcus aureus in a Brazilian veterinary hospital environment

Antimicrobial resistance is a threat to public health. The emergence of antibiotic-resistant Staphylococcus aureus represents a priority for the implementation of preventive measures. The objective was to isolate S. aureus in humans, animals, and animal health care environment, and to characterize the genotypic and phenotypic profile of antimicrobial resistance in these isolates. We isolated S. aureus from staff, animals, and environment of a veterinary hospital, and identified their antimicrobial resistance profiles. Samples were collected from 20 humans, 13 animals, 14 surfaces, 8 mobile phones, and 7 veterinarians' stethoscopes by using sterile swabs. S. aureus was isolated by culturing on mannitol salt agar and preliminary identification was done by Gram staining and catalase test. Subsequently, a polymerase chain reaction was performed for species confirmation and investigating their antimicrobial-resistant genotypic profiles. Phenotypic profiles of resistant isolates were determined using the disk-diffusion technique. Ten S. aureus isolates were recovered from 5/20 humans (25%), it was also recovered from 2/13 animals (15.38%), including 1 dog and 1 cat, and from 1/14 of surfaces (7.14%). The oxacillin-susceptible mecA-positive Staphylococcus aureus phenotype was identified in a feline. Most of the isolates carried at least two resistance genes of different antimicrobial classes, with 90% (9/10) presenting the gene blaZ, with 10% (1/10) presenting the gene mecA, 20% (2/10) presenting tet38, 10% (1/10) presenting tetM, 90% (9/10) presenting norA, 50% (5/10) presenting norC, 10% (1/10) presenting ermA, and 60% (6/10) presenting ermB. In antibiograms, resistance to penicillin was identified in all the isolates, resistance to erythromycin was identified in 80% (8/10), and all the isolate's resistance to erythromycin presented erythromycin-induced resistance to clindamycin. Antimicrobial resistance in the veterinary hospital requires attention due to the risk of interspecies transmission, gene transfer between bacteria that colonize companion animals and humans and, can make antimicrobial therapy difficult.

Occurrence of Acinetobacter baumannii genomic resistance islands (AbGRIs) in Acinetobacter baumannii strains belonging to global clone 2 obtained from COVID-19 patients

AIM

The Acinetobacter baumannii genomic resistance islands (AbGRIs), which were characterized in the genome of the global clone 2 (GC2) A. baumannii contain resistance genes. Here, we aimed to determine the occurrence of AbGRIs in GC2 A. baumannii obtained from COVID-19 patients in a referral hospital in Tehran, Iran.

METHODS

A total of 19 carbapenem-resistant A. baumannii (CRAB) isolates belonging to GC2 and sequence type 2 (ST2), including 17 from COVID-19 patients and two from the devices used in the ICU that the COVID-19 patients were admitted, were examined in this study. Antibiotic susceptibility testing was performed by the disk diffusion method. PCR and PCR mapping, followed by sequencing, were performed to characterize the structure of AbGRI resistance islands in the isolates tested.

RESULTS

The AbGRI3 was the most frequent resistance island (RI) detected, present in all the 19 isolates, followed by AbGRI1 (15 isolates; 78.9%) and AbGRI2 (three isolates; 15.8%). Notably, AbGRIs were identified in one of the A. baumannii strains, which was isolated from a medical device used in the ICU where COVID-19 patients were admitted. Furthermore, new structures of AbGRI1 and AbGRI3 resistance islands were found in this study, which was the first report of these structures.

CONCLUSIONS

The present study provided evidence for the circulation of the GC2 A. baumannii strains harboring AbGRI resistance islands in a referral hospital in Tehran, Iran. It was found that resistance to several classes of antibiotics in the isolates collected from COVID-19 patients is associated with the resistance genes located within AbGRIs.

Serotype distribution and antibiogram of Streptococcus parauberis isolated from fish in South Korea

Streptococcus parauberis is the dominant etiological agent of streptococcosis, the most devastating bacterial disease in the olive flounder farming industry in South Korea. In this study, the distribution of serotypes, antimicrobial susceptibility, and presence of antimicrobial resistance genes (ARGs) in S. parauberis isolates obtained between 1999 and 2021 was thoroughly investigated to gain insight into the dynamics of their presence and the relationship between serotypes and antimicrobial resistance. Disk diffusion testing of 103 isolates against 10 antimicrobial agents was performed, and epidemiological cut-off values generated through normalized resistance interpretation analysis were used to classify wild-type (WT) and non-wild-type (NWT) populations. Principal component analysis and hierarchical clustering were implemented to achieve an understanding on the relationship between serotypes and antimicrobial resistance patterns. PCR-based serotyping showed that serotype Ia (67.1%) was the most prevalent in South Korea, followed by serotypes Ib/Ic (25.2%) and II (7.7%). The highest proportion of isolates was assigned to NWT against amoxicillin (80.6%), followed by oxytetracycline (77.7%) and erythromycin (48.5%). The time-scale data showed that recently obtained serotypes Ib/Ic and II isolates tended to be categorized as NWT populations resistant to more antibiotics, possibly due to microbial adaptation to antibiotic pressure. ARGs responsible for resistance to oxytetracycline and erythromycin were found only in NWT populations in serotype Ia [tet(S) and erm(B), respectively], and serotype II [tet(M) and mef(J)-msr(I), respectively]. We also found that the mef-msr gene pair in S. parauberis serotype II might be involved in low-level resistance to erythromycin. IMPORTANCE This study presents serotype distribution and antimicrobial susceptibility data along with the antimicrobial resistance genes (ARGs) of Streptococcus parauberis, which is an important bacterial fish pathogen worldwide. In particular, almost all oxytetracycline and erythromycin non-wild-type (NWT) populations harbored tet(S) or tet(M), and erm(B) or mef(J)-msr(I), respectively. Interestingly, these ARGs were distributed in a highly serotype-dependent manner, resulting in a clear correlation between the antibiogram and serotype distribution. Moreover, recent isolates belonging to serotypes Ib/Ic and II tended to be more frequently categorized as NWT against antimicrobials, including amoxicillin and cefalexin compared to old isolates, while a dramatic decrease in erythromycin and clindamycin NWT frequencies was observed in recent serotype Ia isolates, which lacked erm(B). These variations might be attributed to shifts in the antibiotics employed in South Korean aquaculture over time. The overall findings would provide important background knowledge for understanding the epidemiology of S. parauberis infection in aquaculture.

First Report of Aeromonas veronii as an Emerging Bacterial Pathogen of Farmed Nile Tilapia (Oreochromis niloticus) in Brazil

Brazil is one of the world's leading producers of Nile tilapia, Oreochromis niloticus. However, the industry faces a major challenge in terms of infectious diseases, as at least five new pathogens have been formally described in the last five years. Aeromonas species are Gram-negative anaerobic bacteria that are often described as fish pathogens causing Motile Aeromonas Septicemia (MAS). In late December 2022, an epidemic outbreak was reported in farmed Nile tilapia in the state of São Paulo, Brazil, characterized by clinical signs and gross pathology suggestive of MAS. The objective of this study was to isolate, identify, and characterize in vitro and in vivo the causative agent of this epidemic outbreak. The bacterial isolates were identified as Aeromonas veronii based on the homology of 16S rRNA (99.9%), gyrB (98.9%), and the rpoB gene (99.1%). A. veronii showed susceptibility only to florfenicol, while it was resistant to the other three antimicrobials tested, oxytetracycline, enrofloxacin, and amoxicillin. The lowest florfenicol concentration capable of inhibiting bacterial growth was ≤0.5 µg/mL. The phenotypic resistance of the A. veronii isolate observed for quinolones and tetracycline was genetically confirmed by the presence of the qnrS2 (colE plasmid) and tetA antibiotic-resistant genes, respectively. A. veronii isolate was highly pathogenic in juvenile Nile tilapia tested in vivo, showing a mortality rate ranging from 3 to 100% in the lowest (1.2 × 104) and highest (1.2 × 108) bacterial dose groups, respectively. To our knowledge, this study would constitute the first report of highly pathogenic and multidrug-resistant A. veronii associated with outbreaks and high mortality rates in tilapia farmed in commercial net cages in Brazil.

Incidence and Genomic Background of Antibiotic Resistance in Food-Borne and Clinical Isolates of Salmonella enterica Serovar Derby from Spain

Salmonella enterica serovar Derby (S. Derby) ranks fifth among nontyphoidal Salmonella serovars causing human infections in the European Union. S. Derby isolates (36) collected between 2006 and 2018 in a Spanish region (Asturias) from human clinical samples (20) as well as from pig carcasses, pork- or pork and beef-derived products, or wild boar (16) were phenotypically characterized with regard to resistance, and 22 (12 derived from humans and 10 from food-related samples) were also subjected to whole genome sequence analysis. The sequenced isolates belonged to ST40, a common S. Derby sequence type, and were positive for SPI-23, a Salmonella pathogenicity island involved in adherence and invasion of the porcine jejune enterocytes. Isolates were either susceptible (30.6%), or resistant to one or more of the 19 antibiotics tested for (69.4%). Resistances to tetracycline [tet(A), tet(B) and tet(C)], streptomycin (aadA2), sulfonamides (sul1), nalidixic acid [gyrA (Asp87 to Asn)] and ampicillin (bla_TEM-1-like) were detected, with frequencies ranging from 8.3% to 66.7%, and were higher in clinical than in food-borne isolates. The fosA7.3 gene was present in all sequenced isolates. The most common phenotype was that conferred by the tet(A), aadA2 and sul1 genes, located within identical or closely related variants of Salmonella Genomic Island 1 (SGI1), where mercury resistance genes were also present. Diverse IncI1-I(α) plasmids belonging to distinct STs provided antibiotic [bla_TEM-1, tet(A) and/or tet(B)] and heavy metal resistance genes (copper and silver), while small pSC101-like plasmids carried tet(C). Regardless of their location, most resistance genes were associated with genetic elements involved in DNA mobility, including a class one integron, multiple insertion sequences and several intact or truncated transposons. By phylogenetic analysis, the isolates were distributed into two distinct clades, both including food-borne and clinical isolates. One of these clades included all SGI1-like positive isolates, which were found in both kinds of samples throughout the entire period of study. Although the frequency of S. Derby in Asturias was very low (0.5% and 3.1% of the total clinical and food isolates of S. enterica recovered along the period of study), it still represents a burden to human health linked to transmission across the food chain. The information generated in the present study can support further epidemiological surveillance aimed to control this zoonotic pathogen.

Evaluating the role of bacterial diversity in supporting soil ecosystem functions under anthropogenic stress

Ecosystem functions and services are under threat from anthropogenic global change at a planetary scale. Microorganisms are the dominant drivers of nearly all ecosystem functions and therefore ecosystem-scale responses are dependent on responses of resident microbial communities. However, the specific characteristics of microbial communities that contribute to ecosystem stability under anthropogenic stress are unknown. We evaluated bacterial drivers of ecosystem stability by generating wide experimental gradients of bacterial diversity in soils, applying stress to the soils, and measuring responses of several microbial-mediated ecosystem processes, including C and N cycling rates and soil enzyme activities. Some processes (e.g., C mineralization) exhibited positive correlations with bacterial diversity and losses of diversity resulted in reduced stability of nearly all processes. However, comprehensive evaluation of all potential bacterial drivers of the processes revealed that bacterial α diversity per se was never among the most important predictors of ecosystem functions. Instead, key predictors included total microbial biomass, 16S gene abundance, bacterial ASV membership, and abundances of specific prokaryotic taxa and functional groups (e.g., nitrifying taxa). These results suggest that bacterial α diversity may be a useful indicator of soil ecosystem function and stability, but that other characteristics of bacterial communities are stronger statistical predictors of ecosystem function and better reflect the biological mechanisms by which microbial communities influence ecosystems. Overall, our results provide insight into the role of microorganisms in supporting ecosystem function and stability by identifying specific characteristics of bacterial communities that are critical for understanding and predicting ecosystem responses to global change.

Molecular Characterization of Antibiotic Resistance Determinants in Klebsiella pneumoniae Isolates Recovered from Hospital Effluents in the Eastern Cape Province, South Africa

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic bacteria responsible for many nosocomial and community-acquired infections. The emergence and spread of antibiotic resistances have resulted in widespread epidemics and endemic dissemination of multidrug-resistant pathogens. A total of 145 K. pneumoniae isolates were recovered from hospital wastewater effluents and subjected to antibiogram profiling. Furthermore, the antibiotic resistance determinants were assessed among phenotypic resistant isolates using polymerase chain reaction (PCR). The isolates showed a wide range of antibiotic resistance against 21 selected antibiotics under 11 classes, with the most susceptible shown against imipenem (94.5%) and the most resistant shown against ampicillin (86.2%). The isolates also showed susceptibility to piperacillin/tazobactam (89.0%), ertapenem (87.6%), norfloxacin (86.2%), cefoxitin (86.2%), meropenem (76.6%), doripenem (76.6%), gentamicin (76.6%), chloramphenicol (73.1%), nitrofurantoin (71.7%), ciprofloxacin (79.3%), amikacin (60.7%), and amoxicillin/clavulanic acid (70.4%). Conversely, resistance was also recorded against tetracycline (69%), doxycycline (56.6%), cefuroxime (46.2%), cefotaxime (48.3%), ceftazidime (41.4%). Out of the 32 resistance genes tested, 28 were confirmed, with [tetA (58.8%), tetD (47.89%), tetM (25.2%), tetB (5.9%)], [sul1 (68.4%), sul1I (66.6%)], and [aadA (62.3%), strA (26%), aac(3)-IIa(aacC2)^a (14.4%)] genes having the highest occurrence. Strong significant associations exist among the resistance determinants screened. About 82.7% of the K. pneumoniae isolates were multidrug-resistant (MDR) with a multiple antibiotics resistance index (MARI) range of 0.24 to 1.0. A dual presence of the resistant genes among K. pneumoniae was also observed to occur more frequently than multiple presences. This study reveals a worrisome presence of multidrug-resistant K. pneumoniae isolates and resistance genes in hospital waste effluent, resulting in higher public health risks using untreated surface water for human consumption. As a result, adequate water treatment and monitoring initiatives designed to monitor antimicrobial resistance patterns in the aquatic ecosystem are required.

ARGs Detection in Listeria Monocytogenes Strains Isolated from the Atlantic Salmon (Salmo salar) Food Industry: A Retrospective Study

Among bacterial foodborne pathogens, Listeria monocytogenes represents one of the most important public health concerns in seafood industries. This study was designed as a retrospective study which aimed to investigate the trend of antibiotic resistance genes (ARGs) circulation in L. monocytogenes isolates identified (in the last 15 years) from Atlantic salmon (Salmo salar) fresh and smoked fillets and environmental samples. For these purposes, biomolecular assays were performed on 120 L. monocytogenes strains collected in certain years and compared to the contemporary scientific literature. A total of 52.50% (95% CI: 43.57-61.43%) of these samples were resistant to at least one antibiotic class, and 20.83% (95% CI: 13.57-28.09%) were classified as multidrug resistant. Concerning ARGs circulation, tetracycline (tetC, tetD, tetK, tetL, tetS), aminoglycoside (aadA, strA, aacC2, aphA1, aphA2), macrolide (cmlA1, catI, catII), and oxazolidinone (cfr, optrA, poxtA) gene determinants were majorly amplified. This study highlights the consistent ARGs circulation from fresh and processed finfish products and environmental samples, discovering resistance to the so-called critical important antimicrobials (CIA) since 2007. The obtained ARGs circulation data highlight the consistent increase in their diffusion when compared to similar contemporary investigations. This scenario emerges as the result of decades of improper antimicrobial administration in human and veterinary medicine.

Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolated from Food-Producing Animals in Tamaulipas, Mexico

Extended-spectrum β-lactamase (ESBL)-producing E. coli has become an important global problem for the public health sector. This study aims to investigate the E. coli antimicrobial resistance profile among living food-producing animals in Tamaulipas, Mexico. A total of 200 fecal samples were collected from bovines, pigs, chickens and sheep. A total of 5.0% of the strains were phenotypically confirmed as ESBL producers. A high percentage of phenotypic antimicrobial resistance was observed against gentamicin (93.3%), tetracycline (86.6%) and streptomycin (83.3%). The gentamicin-resistant strains showed MDR, distributed among 27 resistance patterns to different antimicrobials. The antimicrobial resistance gene tet(A) was detected in 73.3% of isolates, aadA1 in 60.0% and sul2 in 43.3% of strains. The bla_CTX-M gene was found in 23.3% of strains. The virulence gene hlyA was detected in 43.3% of isolates; stx1 and stx2 were not detected in any strain. The phylotyping indicated that the isolates belonged to groups A (33.3%), B1 (16.6%), B2 (40.0%) and D (10.0%). These results show that food-producing animals might be a reservoir of ESBL-producing bacteria and may play a role in their spread.

Antibiotic Resistance in Selected Emerging Bacterial Foodborne Pathogens-An Issue of Concern?

Antibiotic resistance (AR) and multidrug resistance (MDR) have been confirmed for all major foodborne pathogens: Campylobacter spp., Salmonella spp., Escherichia coli and Listeria monocytogenes. Of great concern to scientists and physicians are also reports of antibiotic-resistant emerging food pathogens-microorganisms that have not previously been linked to food contamination or were considered epidemiologically insignificant. Since the properties of foodborne pathogens are not always sufficiently recognized, the consequences of the infections are often not easily predictable, and the control of their activity is difficult. The bacteria most commonly identified as emerging foodborne pathogens include Aliarcobacter spp., Aeromonas spp., Cronobacter spp., Vibrio spp., Clostridioides difficile, Escherichia coli, Mycobacterium paratuberculosis, Salmonella enterica, Streptocccus suis, Campylobacter jejuni, Helicobacter pylori, Listeria monocytogenes and Yersinia enterocolitica. The results of our analysis confirm antibiotic resistance and multidrug resistance among the mentioned species. Among the antibiotics whose effectiveness is steadily declining due to expanding resistance among bacteria isolated from food are β-lactams, sulfonamides, tetracyclines and fluoroquinolones. Continuous and thorough monitoring of strains isolated from food is necessary to characterize the existing mechanisms of resistance. In our opinion, this review shows the scale of the problem of microbes related to health, which should not be underestimated.

Heightened variability observed in resistance and virulence genes across salmonella Kentucky isolates from poultry environments in British Columbia, Canada

Many niche-dependent barriers along the poultry production continuum favour the survival of certain Salmonella serovars over others. Historically, the presence of particular serovars has been determined by niche-specific genes which encode resistance to selective pressures such as host defenses and industrial antimicrobial practices. Over the past decade, Canada has witnessed unexplained shifts in the Salmonella landscape in the poultry sector. Several formerly minor Salmonella serovars, including S. Kentucky and S. Reading, have recently increased in prevalence in live chickens and turkeys, respectively, in British Columbia (BC). The purpose of this research was to investigate the genomic features of the top poultry-associated Salmonella spp. in BC, to probe for serovar-specific characteristics that could address the recently shifting balance of serovars along the poultry continuum. By examining the quantity and diversity of antimicrobial resistance (AMR) genes, virulence factors (VFs), Salmonella Pathogenicity Islands (SPIs), and plasmids across 50 poultry-associated S. enterica isolates using whole genome sequencing and antimicrobial resistance profiling, we have identified serovar-specific differences that likely influence niche survival. Specifically, isolates in our collection from predominantly human pathogenic serovars (S. I 4, [5], 12:i: , S. Typhimurium, and S. Enteritidis) were found to share the IncFIB(S) and IncFII(S) plasmids which carry important VFs known to aid in human host infection. Additionally, these strains held the lowest number of AMR genes, and the highest number of unique SPIs which also facilitate virulence. However, other serovars containing a greater diversity and abundance of resistance genes have been increasing across the poultry sector. S. Kentucky was found to carry unique AMR genes, VFs, SPIs, and plasmids that could bolster persistence in farm and processing environments. Overall, S. Kentucky also had comparatively high levels of intra-serovar genetic variability when compared to other prominent serovars from our collection. In addition, one of our two S. Reading isolates had high carriage of both AMR genes and VFs relative to other isolates in our collection. As the poultry-associated Salmonella landscape continues to evolve in Canada, future studies should monitor the genetic composition of prominent serovars across poultry production to maintain up-to-date risk assessments of these foodborne pathogens to consumers.

Antimicrobial resistance profiles and clonal diversity of Staphylococcus epidermidis isolates from pig farms, slaughterhouses, and retail pork

Livestock-associated coagulase-negative staphylococci (CoNS), such as Staphylococcus (S.) epidermidis, have emerged as a significant reservoir of antimicrobial resistance (AMR). In the current study, the AMR profiles and genetic diversity of S. epidermidis isolates obtained from pig farms, slaughterhouses, and retail pork were analyzed. A total of 89 S. epidermidis isolates, comprising 22 methicillin-resistant (MRSE) and 67 methicillin-susceptible S. epidermidis (MSSE) isolates, were assessed to determine (i) the clonal lineages of the isolates [multilocus sequence (MLST), agr, and staphylococcal cassette chromosome mec (SCCmec) types], (ii) the profiles of AMR phenotypes, and (iii) the carriage of genetic factors associated with major AMR phenotypes and zinc chloride resistance. Two dominant clonal lineages of S. epidermidis, ST100 and ST570, were observed on pig farms, especially in healthy pigs. In addition, potential transmission of pig-associated ST100 MRSE-SCCmec V and ST100 MSSE to farm workers was identified. The high prevalence of ST100 and ST570 isolates in pig farms was associated with high levels of AMR and zinc chloride resistance. In relation to resistance phenotypes, higher carriage rates of resistance genes, such as β-lactams (mecA), phenicols (fexA), and tetracyclines [tet(K), tet(L), tet(S), tet(M), and tet(O)], were identified in pig farm-associated isolates. Furthermore, cfr-mediated linezolid resistance was detected in 14 MSSE isolates from pig farms. This study is the first to provide important insights into the clonal structures and AMR profiles of S. epidermidis isolates collected from healthy pigs, carcass/pork samples, and human workers in Korea.

Determination of the Prevalence and Antimicrobial Resistance of Enterococcus faecalis and Enterococcus faecium Associated with Poultry in Four Districts in Zambia

The presence of antimicrobial-resistant Enterococci in poultry is a growing public health concern worldwide due to its potential for transmission to humans. The aim of this study was to determine the prevalence and patterns of antimicrobial resistance and to detect drug-resistant genes in Enterococcus faecalis and E. faecium in poultry from four districts in Zambia. Identification of Enterococci was conducted using phenotypic methods. Antimicrobial resistance was determined using the disc diffusion method and antimicrobial resistance genes were detected using polymerase chain reaction and gene-specific primers. The overall prevalence of Enterococci was 31.1% (153/492, 95% CI: 27.1–35.4). Enterococcus faecalis had a significantly higher prevalence at 37.9% (58/153, 95% CI: 30.3–46.1) compared with E. faecium, which had a prevalence of 10.5% (16/153, 95% CI: 6.3–16.7). Most of the E. faecalis and E. faecium isolates were resistant to tetracycline (66/74, 89.2%) and ampicillin and erythromycin (51/74, 68.9%). The majority of isolates were susceptible to vancomycin (72/74, 97.3%). The results show that poultry are a potential source of multidrug-resistant E. faecalis and E. faecium strains, which can be transmitted to humans. Resistance genes in the Enterococcus species can also be transmitted to pathogenic bacteria if they colonize the same poultry, thus threatening the safety of poultry production, leading to significant public health concerns.

Serotype Occurrence, Virulence Profiles, Antimicrobial Resistance and Molecular Characterization of Salmonella Isolated from Hospitalized Patients with Gastroenteritis in Great Tunisia between 2010 and 2020

Non-typhoid Salmonella is one of the major causes of food-borne infections worldwide. The aim of the current study is to determine the serotype occurrence, virulence factors and antimicrobial resistance patterns of Salmonella isolated from hospitalized patients. The identification of Salmonella strains was performed according to REMIC, 2018. The susceptibility of Salmonella isolates was assessed against 20 antimicrobials using the disk diffusion method. Some virulence and antimicrobial resistance genes were identified using PCR. Among the 61 isolated Salmonella strains, seven serotypes were identified and all were positive for the virulence genes invA, mgtC and sirA. Critical resistance rates (>40%) were detected for tetracycline, nalidixic acid, amoxicillin and fluoroquinolones. However, resistances to ertapenem, ceftazidim, aztreonam and colistin were null. In addition, 33% of the isolated strains were multidrug-resistant (MDR). Moreover, 80% and 60% of S. Kentucky isolates were identified as fluoroquinolone-resistant and MDR strains, respectively. The qnrB gene was amplified in 63.2% of fluoroquinolone-resistant strains. The dfrA1 gene was identified in 20% (4/20) of the trimethoprim-sulfamethoxazole resistant strains and the integrase Class 2 gene was amplified in only 8.2% (5/61) of the isolates. Our findings highlight the emergence of MDR Salmonella isolates. A rationalization of antimicrobial use is urgently recommended in both human and veterinary medicine.

Distribution analysis of tetracycline resistance genes in Escherichia coli isolated from floor surface and effluent of pig slaughterhouses in Banten Province, Indonesia

Background and Aim

Slaughterhouses and their effluents could serve as a "hotspot" for the occurrence and distribution of antibiotic-resistant bacteria in the environment. This study aimed to understand the distribution of tetracycline resistance genes in Escherichia coli isolated from the floor surface and effluent samples of pig slaughterhouses in Banten Province, Indonesia.

Materials and Methods

Ten samples, each from floor surface swabs and effluents, were collected from 10 pig slaughterhouses in Banten Province. Escherichia coli strains were isolated and identified by referring to the protocol of the Global Tricycle Surveillance extended-spectrum beta-lactamase E. coli from the WHO (2021). Quantitative real-time polymerase chain reaction (qPCR) was used to detect the tet genes.

Results

The tetA, tetB, tetC, tetM, tetO, and tetX genes were distributed in the isolates from the floor surface samples, and the tetA, tetC, tetE, tetM, tetO, and tetX genes were distributed in the isolates from the effluent samples. The tetO gene (60%) was the most dominant gene in the isolates from floor surface samples, while the tetA gene was the dominant one in the isolates from the effluent samples (50%). The tetA + tetO gene combination was the dominant pattern (15%) in the E. coli isolates.

Conclusion

The high prevalence and diversity of the tet genes in floor surface and effluent samples from pig slaughterhouses in Banten Province indicated that the transmission of the tet genes had occurred from pigs to the environment; thus, this situation should be considered a serious threat to public health.

Correlations among Antibiotic Resistance Genes, Mobile Genetic Elements and Microbial Communities in Municipal Sewage Treatment Plants Revealed by High-Throughput Sequencing

Municipal sewage treatment plants (MSTPs) are environmental pools for antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs), which is cause for growing environmental-health concerns. In this study, the effects of different wastewater treatment processes on microbial antibiotic resistance in four MSTPs were investigated. PCR, q-PCR, and molecular cloning integrally indicated that the tetracycline resistance (tet) genes significantly reduced after activated-sludge treatment. Illumina high-throughput sequencing revealed that the broad-spectrum profile of ARGs and mobile element genes (MGEs) were also greatly decreased by one order of magnitude via activated sludge treatment and were closely associated with each other. Correlations between ARGs and bacterial communities showed that potential ARB, such as Acinetobacter, Bacteroides, and Cloaibacterium, were removed by the activated-sludge process. Sedimentation processes cannot significantly affect the bacterial structure, resulting in the relative abundance of ARGs, MGEs, and ARB in second-clarifier effluent water being similar to activated sludge. A comprehensive study of ARGs associated with MGEs and bacterial structure might be technologically guided for activated sludge design and operation in the MSTPs, to purposefully control ARGs carried by pathogenic hosts and mobility.

Molecular characterization of carbapenem resistant E. coli of fish origin reveals the dissemination of NDM-5 in freshwater aquaculture environment by the high risk clone ST167 and ST361

Aquatic environment can act as reservoir and disseminator of antimicrobial resistance and resistant pathogens. Novel high-risk carbapenem resistant E. coli (CREC) are continuously emerging worldwide; however, the occurrence of CREC in freshwater aquaculture environment is largely unexplored. To fill this gap, large scale sampling of freshwater pond sites and retail fish markets was done between Oct 2020 and Oct 2021 to investigate the CREC contamination in fish. The frequency of CREC contamination in the freshwater fish was 6.99% (95% CI: 3.78-10.20%). All the isolates were MDR and harbored carbapenemase encoding gene, bla_NDM-5 along with other antimicrobial resistance genes (ARGs), bla_TEM (64.7%), bla_CTX-M-15 (35.3%), bla_OXA-1 (5.9%), tet(A) (100%), sul1 (94.1%), qnrS (82.3%), cat1 (35.3%), and cat2 (23.5%). The isolates belonged to phylogroup C and showed low virulence gene profile. ERIC-PCR grouped the isolates into five clusters (I-V). The isolates of clusters I, II, and III were identified as ST167 (76.4%) and of cluster IV as ST361 (17.6%). This is the first report documenting the contamination of NDM-5 producing E. coli ST167 and ST361 of clinical/livestock lineage in freshwater fish from India. The bla_NDM-5 was significantly associated with ARGs, tet(A), and sul1; and plasmid replicons, IncF, IncI1, and IncP, signifying the presence of bla_NDM-5 and associated ARGs on these transferable plasmids. These findings were validated by the successful conjugal transfer of bla_NDM-5 and associated ARGs into non-CREC strain (J53). Our study highlights the ability of CREC to disseminate antimicrobial resistance which has health implications and environmental concerns.

Molecular and Antimicrobial Susceptibility Characterization of Escherichia coli Isolates from Bovine Slaughterhouse Process

Antimicrobials are routinely used in human and veterinary medicine. With repeated exposure, antimicrobials promote antibiotic resistance, which poses a threat to public health. In this study, we aimed to determine the susceptibility patterns, virulence factors, and phylogroups of E. coli isolates during the killing process in a bovine slaughterhouse. We analyzed 336 samples (from water, surfaces, carcasses, and feces), and 83.3% (280/336) were positive for E. coli. The most common phenotypic resistances that we detected were 50.7% (142/280) for tetracycline, 44.2% (124/280) for cephalothin, 34.6% (97/280) for streptomycin, and 36.7% (103/280) for ampicillin. A total of 82.4% of the isolates had resistance for at least one antimicrobial, and 37.5% presented multiresistance. We detected a total of 69 different phenotypic resistance patterns. We detected six other resistance-related genes, the most prevalent being tetA (22.5%) and strB (15.7%). The prevalence values of the virulence genes were 5.4% in hlyA, 1.4% in stx1, and 0.7% in stx2. The frequencies of the pathogenic strains (B2 and D) were 32.8% (92/280) and 67.1% (188/280) as commensals A and B1, respectively. E. coli isolates with pathogenic potential and multiresistance may represent an important source of dissemination and a risk to consumers.

Microbiological Biodiversity of Regional Cow, Goat and Ewe Milk Cheeses Produced in Poland and Antibiotic Resistance of Lactic Acid Bacteria Isolated from Them

(1) Unique sensory values of traditional and regional dairy products made them more and more popular among consumers. Lactic acid bacteria naturally occurring in these products can express antibiotic resistance and be a reservoir of antibiotic resistance genes (ARG) in the environment. The aim of the study was to characterize the microbial diversity of twenty regional cheeses produced from non-pasteurized cow, goat and ewe milk, and investigate the phenotypic and genotypic antibiotic resistance (AR) of lactic acid bacteria isolated from these products. (2) Conventional microbiological methods were applied for the enumeration of lactic acid bacteria (lactobacilli and lactococci) and their isolation, and for the enumeration of Enterococcus, Staphylococcus, Enterobacteriaceae and spores. The disc diffusion method was applied for phenotypic AR. The PCR-based methods were used for strain identification, microbiological diversity of cheeses (PCR-DGGE), and for AR gene detection. (3) Among 79 LAB isolates the most frequent species were L. plantarum (n = 18), Leuc. lactis (n = 17), Lc. lactis (n = 11), Leuc. mesenteroides (n = 9) and L. pentosus (n = 8). Additionally, by using the PCR-DGGE method, DNA of L. casei was found in nine products. Lactobacilli (5.63-8.46 log cfu/g) and lactococci (6.15-8.41 log cfu/g) predominated over Enterococcus (max. 4.89 log cfu/g), Staphylococcus (max. 4.18 log cfu/g), and Enterobacteriaceae (mostly up to 4.88 log cfu/g). Analysis of phenotypic resistance to tetracycline (30 µg), erythromycin (15 µg), and chloramphenicol (30 µg) showed that 29% of LAB isolates were resistant to one antibiotic, 8%-to two, and 12%-to all tested antibiotics. Antibiotic resistance genes (AGR) for tetracycline (tet(M), tet(L), tet(W)), erythromycin (erm(B)) and chloramphenicol (cat-TC) were detected in 30 (38%), 29 (36.7%) and 33 (43.4%) LAB isolates, respectively. Among 31 LAB isolates phenotypically susceptible to all tested antibiotics, only 5 (16%) had no ARGs. (4) The results obtained in our work shed light on the potential threat posed by the widespread presence of ARGs in LAB present in regional cheeses.

Tetracycline Resistance Genes in Wild Birds from a Wildlife Recovery Centre in Central Italy

Wild animals are less likely to be exposed directly to clinical antimicrobial agents than domestic animals or humans, but they can acquire antimicrobial-resistant bacteria through contact with humans, animals, and the environment. In the present study, 254 dead free-living birds belonging to 23 bird species were examined by PCR for the presence of tetracycline resistance (tet) genes. A fragment of the spleen was collected from each bird carcass. A portion of the intestine was also taken from 73 of the 254 carcasses. Extracted DNA was subjected to PCR amplification targeting the tet(L), tet(M), and tet(X) genes. In total, 114 (45%) of the 254 birds sampled belonging to 17 (74%) of the 23 bird species tested were positive for one or more tet genes. The tet(M) gene showed a higher frequency than the other tested genes, both in the spleen and in the intestine samples. These results confirm the potential role of wild birds as reservoirs, dispersers, or bioindicators of antimicrobial resistance in the environment.

Antimicrobial Resistance and Virulence Genes of Streptococcus Agalactiae Isolated from Mastitis Milk Samples in China

Introduction

Streptococcus agalactiae is an important zoonotic pathogen that affects milk production and quality and poses a threat to public health. Treatment of infections with this bacterium exploits antimicrobials, to which the resistance of S. agalactiae is a growing problem. Addressing the possibility of a correlation between this pathogen's genetic factors for antimicrobial resistance and virulence, this study attempted to identify the relevant genes.

Material and Methods

Antimicrobial resistance of S. agalactiae isolated from 497 Chinese bovine mastitic milk samples was detected by the broth microdilution method. Eight drug resistance genes and eleven virulence genes were detected using PCR.

Results

Streptococcus agalactiae was 100% susceptible to rifampicin and vancomycin, 93.33% susceptible to sulfisoxazole and sulfamethoxazole, but 100% resistant to ≥3 of the 16 antimicrobial agents, thereby being multidrug resistant, with resistance to oxacillin, tetracycline, erythromycin, clindamycin, and gentamicin being common. The ermB, ermA and lnuA genes were carried by 73.33%, 66.67% and 60.00% of the strains, respectively. The carriage rates of the glnA, clyE, hylB, bibA, iagA, and fbsA virulence genes were greater than 40%, lmb and bac were not observed in any strain, and glnA+hylB+bibA+iagA+fbsA+clyE combined virulence gene patterns were the most commonly detected.

Conclusion

Antimicrobial resistance of S. agalactiae is still a great concern for cattle health in China, and multidrug resistance coupled with the high positive rates of this bacterium's strains for virulence genes indicates the importance of S. agalactiae surveillance and susceptibility tests.