Harboring Antibiotic and Heavy Metal Resistance Genes

Carbapenem resistance in the food supply chain

Carbapenems are critically important antibiotic agents because they are considered the "last-resort" antibiotics for treating serious infections. However, resistance to carbapenems is increasing throughout the world and has become an urgent problem. Some carbapenem-resistant bacteria are considered urgent threats by the United States Centers for Disease Control and Prevention. In this review, we searched and summarized studies published mostly in the recent five years related to carbapenem resistance in three main areas in the food supply chain: livestock, aquaculture, and fresh produce. We have found that many studies have shown a direct or indirect correlation between carbapenem resistance in the food supply chain and human infections. Our review also revealed the worrisome incidences of the cooccurrence of resistance to carbapenem and other "last-resort" antibiotics, such as colistin and/or tigecycline, in the food supply chain. Antibiotic resistance is a global public health challenge, and more effort related to carbapenem resistance in the food supply chain for different food commodities is still needed in some countries and regions, including the United States. In addition, antibiotic resistance in the food supply chain is a complicated issue. Based on the knowledge from current studies, only restricting the use of antibiotics in food animal production might not be enough. Additional research is needed to determine factors contributing to the introduction and persistence of carbapenem resistance in the food supply chain. Through this review, we hope to provide a better understanding of the current state of carbapenem resistance, and the niches of knowledge that are needed for developing strategies to mitigate antibiotic resistance, especially carbapenem resistance in the food supply chain.

Detection of virulence, antimicrobial resistance, and heavy metal resistance properties in Vibrio anguillarum isolated from mullet (Mugil cephalus) cultured in Korea

In the present study, we identified and characterized 22 strains of V. anguillarum from 145 samples of mullets (Mugill cephallus) cultured in several fish farms in South Korea. They were subjected to pathogenicity tests, antimicrobial susceptibility test, and broth dilution test to detect virulence markers, antimicrobial resistance, and heavy metal resistance properties. All the isolates showed amylase and caseinase activity, followed by gelatinase (90.9%), DNase (45.5%), and hemolysis activities (α = 81.1% and β = 18.2%). The PCR assay revealed that isolates were positive for VAC, ctxAB, AtoxR, tdh, tlh, trh, Vfh, hupO, VPI, and FtoxR virulence genes at different percentages. All the isolates showed multi-drug resistance properties (MAR index ≥ 0.2), while 100% of the isolates were resistant to oxacillin, ticarcillin, streptomycin, and ciprofloxacin. Antimicrobial resistance genes, qnrS (95.5%), qnrB (86.4%), and StrAB (27.3%), were reported. In addition, 40.9% of the isolates were cadmium-tolerant, with the presence of CzcA (86.4%) heavy metal resistance gene. The results revealed potential pathogenicity associated with V. anguillarum in aquaculture and potential health risk associated with consumer health.

Hiding in Plain Sight: Characterization of Aeromonas Species Isolated from a Recreational Estuary Reveals the Carriage and Putative Dissemination of Resistance Genes

Antimicrobial resistance (AMR) has become one of the greatest challenges worldwide, hampering the treatment of a plethora of infections. Indeed, the AMR crisis poses a threat to the achievement of the United Nations' Sustainable Development Goals and, due to its multisectoral character, a holistic approach is needed to tackle this issue. Thus, the investigation of environments beyond the clinic is of utmost importance. Here, we investigated thirteen strains of antimicrobial-resistant Aeromonas isolated from an urban estuary in Brazil. Most strains carried at least one antimicrobial resistance gene and 11 carried at least one heavy metal resistance gene. Noteworthy, four (30.7%) strains carried the bla_KPC gene, coding for a carbapenemase. In particular, the whole-genome sequence of Aeromonas hydrophila strain 34SFC-3 was determined, revealing not only the presence of antimicrobial and heavy metal resistance genes but also a versatile virulome repertoire. Mobile genetic elements, including insertion sequences, transposons, integrative conjugative elements, and an IncQ1 plasmid were also detected. Considering the ubiquity of Aeromonas species, their genetic promiscuity, pathogenicity, and intrinsic features to endure environmental stress, our findings reinforce the concept that A. hydrophila truly is a "Jack of all trades'' that should not be overlooked under the One Health perspective.

Infectivity and Transmissibility of Acute Hepatopancreatic Necrosis Disease Associated Vibrio parahaemolyticus in Frozen Shrimp Archived at −80 °C

Acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus (VpAHPND) has been reported in commodity shrimp, but the potential risk of its global spread via frozen shrimp in the shrimp trade is yet to be fully explored. We hypothesized that frozen shrimp with AHPND could be a source of VpAHPND transmission; thus, the infectivity of frozen shrimp with AHPND was evaluated using a shrimp bioassay. To prepare infected frozen shrimp, 12 Penaeus vannamei (average weight, 2 g) were exposed to VpAHPND by immersion in water with a VpAHPND concentration of 1.55 × 107 CFU mL−1; once dead, the shrimp were stored at −80 °C for further analysis. After two weeks, a PCR assay was used to confirm AHPND positivity in frozen shrimp (n = 2), and VpAHPND was reisolated from the hepatopancreases of these shrimp. For the infectivity test, 10 P. vannamei (average weight, 4 g) were fed with the hepatopancreases of VpAHPND -infected frozen shrimp (n = 10). After feeding, 70% of the shrimp died within 118 h, and the presence of VpAHPND was confirmed using a PCR assay and histopathology examination; moreover, VpAHPND was successfully reisolated from the hepatopancreases of the dead shrimp. We are the first to evaluate the potential transmissibility of VpAHPND in frozen shrimp, and our results suggest that frozen shrimp with AHPND are a potential source of disease spreading between countries during international trade.

Virulence and antimicrobial resistance potential of Aeromonas spp. associated with shellfish

Aeromonas spp. are associated with seafood-related outbreaks worldwide. In seafood industry, shellfish play a major role in global seafood production. With this emerging trend of shellfish consumption, shellfish-related bacterial infections are being reported frequently. Aeromonas spp. are natural contaminants found in shellfish. Although 36 species have been identified, some species including Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii biotype sobria have dragged major attention as foodborne pathogenic bacteria. The ability to elaborate a variety of virulence factors of Aeromonas spp. contributes to the pathogenic activities. Also, emerging antimicrobial resistance in Aeromonas spp. has become a huge challenge in seafood industry. Furthermore, multidrug resistance increases the risk of consumer health. Studies have supplied pieces of evidence about the emerging health risk of Aeromonas spp. isolated from seafood. Therefore, the present review was intended to highlight the prevalence, virulence and antimicrobial resistance of Aeromonas spp. isolated from various types of shellfish.

Dietary supplementation with probiotic Rhodobacter sphaeroides SS15 extract to control acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio parahaemolyticus in cultivated white shrimp

Cultivation of Penaeus vannamei (Pacific white shrimp) is faced with the serious problem of acute hepatopancreatic necrosis disease (AHPND), caused by Vibrio parahaemolyticus that carries plasmids containing binary toxin genes. The disease is typically moderated by the use of antibiotics. To investigate the control of AHPND and maintenance of water quality without the use of antibiotics, the supplementation of shrimp feed with anti-vibrio compounds from a crude extract of probiotic Rhodobacter sphaeroides SS15 was evaluated. The experimental design comprised four treatments: two that were challenged with AHPND-causing V. parahaemolyticus SR2 at a density of 6.0 x 10⁵ cells mL^-1 and two that were not challenged. The unchallenged groups comprised a control group that received commercial feed only (CF) and a group that received CF supplemented with 0.27% (w/w) of the extract of R. sphaeroides SS15 (modified CF: MCF). The treatments challenged with V. parahaemolyticus SR2 comprised a challenge group that received CF only (challenge CF: CF-SR2) and a challenge group that received modified CF (challenge MCF: MCF-SR2). V. parahaemolyticus SR2 was inoculated at the start of cultivation and at day 48 at the same cell density. No significant difference in growth performance was found among all treatments. All water quality parameters were better in the two treatments that received modified CF but excess nitrite, due to overfeeding in low salinity (5-8 ppt), caused shrimp mortality in all treatments. Vibrio populations were much higher in the CF treatments than in the modified CF treatments. After the first challenge, the survival rate was about 67% in both the CF-SR2 and MCF-SR2 treatments, compared with approximately 83% in the unchallenged treatments. One day after the second challenge, mortality in the CF-SR2 treatment was 100%, whereas 16.67% survived in the MCF-SR2 treatment. The survival rate was roughly 27% higher in the MCF treatment than in the CF treatment. The hepatopancreas and gut of both modified CF treatments showed no sign of AHPND. Via better water quality and trained immunity, the anti-vibrio compounds in the modified CF have great potential to increase the survival of cultivated shrimp infected with AHPND-causing strain SR2.

Multi-drug resistant mesophilic aeromonads isolated from marketed scallops (Patinopecten yessoensis) harboring resistance genes

Antimicrobial resistance properties of 32 Aeromonas strains isolated from fresh scallops (Patinopecten yessoensis (Jay)) marketed in Korea were assessed. All the Aeromonas spp., including A. salmonicida, were mesophilic and grew very well at 37°C. The isolates were tested for susceptibility to 19 antimicrobials belonging to eight antimicrobial classes. All isolates were multi-drug resistant, which means they were resistant to five or more antimicrobials. Higher resistance rates (≥ 50%) were observed for ampicillin, piperacillin, cephalothin, imipenem, meropenem, trimethoprim-sulfamethoxazole, tetracycline, oxytetracycline, and nalidixic acid while intermediate resistance was also determined. PCR assays revealed the presence of many antimicrobial resistance genes among the isolates in varying combinations. Among them, some isolates harbored higher numbers of resistant genes, e.g., A. veronii-V1 (aac(6’)-Ib, tetE, qnrS, IntI1), A. salmonicida–SL10 (IntI1, blaCTX, aac(3’)-Ib, aac(6’)-Ib, qnrS), A. hydrophila–H13 (IntI1, blaTEM, qnrS, aac(6’)-Ib, strA-strB). However, neither the blaSHV, blaIMP, tetB, qnrA, qnrB, and aphAI-IAB genes nor class1 integrons were detected in any of the isolates. Discrepancies between phenotypic and genetic resistance traits were observed in some isolates. With respect to outcomes, scallops are proposed as a source of multi-drug resistant Aeromonas spp. that harbor antimicrobial resistant genes.

Epidemiology of β-Lactamase-Producing Pathogens

β-Lactam antibiotics have been widely used as therapeutic agents for the past 70 years, resulting in emergence of an abundance of β-lactam-inactivating β-lactamases. Although penicillinases in Staphylococcus aureus challenged the initial uses of penicillin, β-lactamases are most important in Gram-negative bacteria, particularly in enteric and nonfermentative pathogens, where collectively they confer resistance to all β-lactam-containing antibiotics. Critical β-lactamases are those enzymes whose genes are encoded on mobile elements that are transferable among species. Major β-lactamase families include plasmid-mediated extended-spectrum β-lactamases (ESBLs), AmpC cephalosporinases, and carbapenemases now appearing globally, with geographic preferences for specific variants. CTX-M enzymes include the most common ESBLs that are prevalent in all areas of the world. In contrast, KPC serine carbapenemases are present more frequently in the Americas, the Mediterranean countries, and China, whereas NDM metallo-β-lactamases are more prevalent in the Indian subcontinent and Eastern Europe. As selective pressure from β-lactam use continues, multiple β-lactamases per organism are increasingly common, including pathogens carrying three different carbapenemase genes. These organisms may be spread throughout health care facilities as well as in the community, warranting close attention to increased infection control measures and stewardship of the β-lactam-containing drugs in an effort to control selection of even more deleterious pathogens.

Antibiotic and heavy metal resistance genes in Aeromonas spp. isolated from marketed Manila Clam (Ruditapes philippinarum) in Korea

AIMS

Manila clam (Ruditapes philippinarum) is one of the most popular seafood in Korea, owing to their unique taste and nutritional value. This study aimed to disclose the antibiotic and heavy metal resistance characteristics of Aeromonas spp. isolated from marketed Manila clam in Korea.

METHODS AND RESULTS

A total of 36 Aeromonas spp. strains were isolated and subjected to two tests: an antibiotic disk diffusion test to determine their resistance to antibiotics, and a broth dilution test to determine their resistance to heavy metals. PCR-based amplification was performed to detect the resistance genes. A high level of resistance to ampicillin (100%) and cephalothin (89%) was observed, while 42, 39, 36 and 36% of the isolates were resistant to oxytetracycline, imipenem, nalidixic acid and tetracycline respectively. In addition, among the tested heavy metals, cadmium (Cd) recorded the highest resistance rate (61%), followed by chromium (Cr) (50%), lead (Pb) (47%) and copper (Cu) (37%). However, mercury (Hg) resistance was not observed. PCRs revealed the occurrence of bla_TEM , bla_SHV , bla_CTX-M , qnrS, tetB, tetE, aac(6')-Ib, strA-strB and intI1 genes among 100, 31, 31, 78, 78, 89, 25, 50 and 72% of the isolates respectively. Moreover, heavy metal resistance genes, copA, merA and czcA were detected in 25, 47 and 61% of the isolates respectively.

CONCLUSIONS

The results suggest the importance of multi-drug and heavy metal-resistant aeromonads in Manila clam to assess the consumer safety and public health.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first to elaborate on the importance of multi-drug and heavy metal-resistant aeromonads in Manila clam. Particularly, the presence of extended-spectrum-β-lactamase genes and other antibiotic resistance genes intensifies the possible health risks and may complicate therapeutic treatments upon infection, while heavy metal resistance suggests possible heavy metal exposure.

Graphene oxide as a tool for antibiotic-resistant gene removal: a review

Environmental pollutants, including antibiotics (ATBs), have become an increasingly common health hazard in the last several decades. Overdose and abuse of ATBs led to the emergence of antibiotic-resistant genes (ARGs), which represent a serious health threat. Moreover, water bodies and reservoirs are places where a wide range of bacterial species with ARGs originate, owing to the strong selective pressure from presence of ATB residues. In this regard, graphene oxide (GO) has been utilised in several fields including remediation of the environment. In this review, we present a brief overview of resistant genes of frequently used ATBs, their occurrence in the environment and their behaviour. Further, we discussed the factors influencing the binding of nucleic acids and the response of ARGs to GO, including the presence of salts in the water environment or water pH, because of intrinsic properties of GO of not only binding to nucleic acids but also catalysing their decomposition. This would be helpful in designing new types of water treatment facilities.

Incidence of antimicrobial resistance genes and class 1 integron gene cassettes in multidrug-resistant motile Aeromonas sp. isolated from ornamental guppy (Poecilia reticulata)

Aeromonas sp. are opportunistic pathogenic bacteria which are associated with various diseases in ornamental fish, aquaculture raised species and wild fisheries. In our study, antimicrobial resistance patterns, antimicrobial resistance genes and class 1 integron gene cassettes of 52 guppy-borne Aeromonas sp. were examined. The isolates were identified as A. veronii (n = 34), A. dhakensis (n = 10), A. hydrophila (n = 3), A. caviae (n = 3) and A. enteropelogenes (n = 2) by gyrB gene sequencing. Every isolate was resistant to at least four antimicrobials in disc diffusion test. The resistance to amoxicillin, nalidixic acid and oxytetracycline was 100% among the tested isolates. 92·30, 76·92, 71·15, 51·92, 51·92 and 50·00% of the isolates were resistant to ampicillin, rifampicin, imipenem, cephalothin, tetracycline and trimethoprim respectively. The multiple antibiotic resistance index values ranged from 0·28 to 0·67. PCR amplification of antimicrobial resistance genes implied the occurrence of tetracycline resistance (tetA (65·39%), tetE (25·00%) and tetB (15·38%)), plasmid-mediated quinolone resistance (qnrS (26·92%) and qnrB (17·31%)) and aminoglycoside resistance (aphaAI-IAB (7·69%) and aac (6')-Ib (3·84%)) genes in the isolates. The IntI gene was positive for 36·54% of the isolates and four class 1 integron gene cassette profiles (aadA2, qacE2-orfD, aadA2-catB2 and dfrA12-aadA2) were identified. These data suggest that ornamental guppy can be a reservoir of multidrug-resistant Aeromonas sp. which comprise different antimicrobial resistance genes and class 1 integrons. SIGNIFICANCE AND IMPACT OF THE STUDY: Antimicrobial resistance genes and integron gene cassettes of ornamental fish-borne aeromonads are poorly studied. The antimicrobial resistance patterns, antimicrobial resistance genes and class 1 integron gene cassettes of Aeromonas sp. isolated from ornamental guppy were characterized for the first time in Korea. The incidence of different antimicrobial resistance genes and class 1 integron gene cassettes were observed in multidrug-resistant Aeromonas isolates. This result suggests that better management practices are necessary to prevent and address the serious consequences of indiscriminate and inappropriate antimicrobial use, and the distribution of multidrug-resistant bacteria.