Molecular characterization of virulence and antibiotic resistance genes among Salmonella serovars isolated from broilers in Egypt

Prevalence and serotype of poultry salmonellosis in Africa: a systematic review and meta-analysis

Salmonellosis represents a significant economic and public health concern for the poultry industry in Africa, leading to substantial economic losses due to mortality, reduced productivity, and food safety problems. However, comprehensive information on the burden of poultry salmonellosis at the continental level is scarce. To address this gap, a systematic review and meta-analysis were conducted to consolidate information on the prevalence and circulating serotypes of poultry salmonellosis in African countries. This involved the selection and review of 130 articles published between 1984 and 2021. A detailed systematic review protocol was structured according to Cochrane STROBE and PRISMA statement guideline. From the 130 selected articles from 23 different African countries, the overall pooled prevalence estimate (PPE) of poultry salmonellosis in Africa was found to be 14.4% (95% CI = 0.145-0.151). Cameroon reported the highest PPE at 71.9%. The PPE was notably high in meat and meat products at 23%. The number of research papers reporting poultry salmonellosis in Africa has shown a threefold increase from 1984 to 2021. Salmonella Enteritidis and Typhimurium were the two most prevalent serotypes reported in 18 African countries. Besides, Salmonella Kentucky, Virchow, Gallinarum, and Pullorum were also widely reported. Western Africa had the highest diversity of reported Salmonella serotypes (141), in contrast to southern Africa, which reported only 27 different serotypes. In conclusion, poultry salmonellosis is highly prevalent across Africa, with a variety of known serotypes circulating throughout the continent. Consequently, it is crucial to implement strategic plans for the prevention and control of Salmonella in Africa.RESEARCH HIGHLIGHTS The pooled sample prevalence of poultry salmonellosis in Africa is high (14.4%).The highest PPE was recorded in meat and meat products.Salmonella serotypes of zoonotic importance were found in all sample types.Salmonella Enteritidis and Typhimurium are common serotypes spreading in Africa.

Frequency, serotyping, antibiogram, and seasonality of Salmonella isolated from red meat markets

Bacterial pathogenic strains are as adaptable as Salmonella strains and cause diverse intestinal and extraintestinal diseases in humans and other mammals worldwide. Red meat and its products are important hosts for many zoonotic diseases. This work was designed to investigate the frequency, serotypes, and antimicrobial resistance profile of isolated Salmonella spp. in red meat (cattle, sheep, and goats) sold in Dhamar Governorate, Yemen. A total of 250 red meat samples were collected from the retail seller market between July and December 2022. All samples were transported immediately to the laboratory, subcultured on selective enrichment agar, and identified by serotyping and antimicrobial susceptibility tests via disk diffusion methods. The results indicated 26 positive samples of Salmonella out of the 250 samples (10.4%). Notably, isolates belong to ten various serotypes: S. Typhimurium 19.2%, S. Anatum 15.4%, S. Newport 11.5%, S. Enteritidis 11.5%, S. Muenchen 11.5%, S. Infantis 7.7%, S. Montevideo 7.7%, S. Dublin 7.7%, S. Senftenberg 3.9%, and S. Arizona 3.9%. The antibiotic resistance profile revealed that 57.5%, 53.9%, and 53.9% of isolates are resistant to erythromycin, tetracycline, and norfloxacin, respectively. This resistance among Salmonella spp. suggests a significant threat to health, which will in turn require an active safety measure and response. On the other hand, the seasonal variations "August and July" were found to be associated with an increased frequency of Salmonella isolation.

Unveiling the landscape of resistance against high priority critically important antimicrobials in food-producing animals across Africa: A scoping review

The rapid population growth in Africa is associated with an increasing demand for livestock products which in turn can lead to antimicrobial use. Antimicrobial usage in animals contributes to the emergence and selection of resistant bacteria which constitutes a serious public health threat. This study aims to review and summarize the available information on highest priority critically important antimicrobials (HPCIAs) resistance in livestock production in Africa. This work will help to inform future policies for controlling antimicrobial resistance (AMR) in the food production chain. A scoping review was conducted according to the Cochrane handbook and following PRISMA 2020 guidelines for reporting. Primary research studies published after 1999 and reporting resistance of Escherichia coli, Enterococcus spp, Staphylococcus aureus, Salmonella spp, and Campylobacter spp to HPCIAs in poultry, cattle, pigs, goats, and sheep in Africa were searched in four databases. A total of 312 articles were included in the review. The majority of the studies (40.7) were conducted in North African countries. More than 49.0% of included studies involved poultry and 26.2% cattle. Cephalosporins and quinolones were the most studied antimicrobial classes. Of the bacteria investigated in the current review, E. coli (41.7%) and Salmonella spp (24.9%) represented the most commonly studied. High levels of resistance against erythromycin in E. coli were found in poultry (MR 96.1%, IQR 83.3-100.0%), cattle (MR 85.7%, IQR 69.2-100.0%), and pigs (MR 94.0%, IQR 86.2-94.0%). In sheep, a high level of resistance was observed in E. coli against nalidixic acid (MR 87.5%, IQR 81.3-93.8%). In goats, the low level of sensibility was noted in S. aureus against streptomycin (MR 86.8%, IQR 19.4-99.0%). The study provides valuable information on HPCIAs resistance in livestock production in Africa and highlights the need for further research and policies to address the public health risk of AMR. This will likely require an investment in diagnostic infrastructure across the continent. Awareness on the harmful impact of AMR in African countries is a requirement to produce more effective and sustainable measures to curb AMR.

An Alternative Approach Using Nano-garlic Emulsion and its Synergy with Antibiotics for Controlling Biofilm-Producing Multidrug-Resistant Salmonella in Chicken

Surface-growing antibiotic-resistant pathogenic Salmonella is emerging as a global health challenge due to its high economic loss in the poultry industry. Their pathogenesis, increasing antimicrobial resistance, and biofilm formation make them challenging to treat with traditional therapy. The identification of antimicrobial herbal ingredients may provide valuable solutions to solve this problem. Therefore, our aim is to evaluate the potency of nano garlic as the  alternative of choice against multidrug-resistant (MDR) Salmonella isolates using disc diffusion and microdilution assays. Then, checkerboard titration in trays was applied, and FIC was measured to identify the type of interaction between the two antimicrobials. A disc diffusion assay revealed that neomycin was the drug of choice. The range of nano garlic MIC was 12.5-25 μg/ml, while the neomycin MIC range was 32-64 μg/ml. The FIC index established a synergistic association between the two tested drugs in 85% of isolates. An experimental model was used including nano garlic and neomycin alone and in combination against Salmonella infection. The combination therapy significantly improved body productivity and inhibited biofilm formation by more than 50% down regulating the CsgBAD, motB, and sipA operons, which are responsible for curli fimbriae production and biofilm formation in Salmonella serotypes.

Clinical Characteristics, Antimicrobial Resistance, Virulence Genes and Multi-Locus Sequence Typing of Non-Typhoidal Salmonella Serovar Typhimurium and Enteritidis Strains Isolated from Patients in Chiang Mai, Thailand

Non-typhoidal salmonellosis (NTS) caused by ingesting Salmonella enterica contaminated food or drink remains a major bacterial foodborne disease. Clinical outcomes of NTS range from self-limited gastroenteritis to life-threatening invasive NTS (iNTS). In this study, we isolated Salmonella spp. from the stool and blood of patients hospitalized at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand, between 2016-2021 (a total of 395 cases). Then, serovar Typhimurium and Enteritidis were identified and further characterized by multiplex PCR, and multi-locus sequence typing. Our data show that multidrug resistance (MDR) sequence type 34 (ST34) and ST11 are the predominant sequence types for serovars Typhimurium and Enteritidis, respectively. Most S. Typhimurium ST34 lacks spvB, and most S. Enteritidis ST11 harbor sseI, sodCI, rpoS and spvB genes. NTS can be found in a wide range of ages, and anemia could be a significant factor for S. Typhimurium infection (86.3%). Both S. Typhimurium (6.7%) and S. Enteritidis (25.0%) can cause iNTS in immunocompromised patients. S. Typhimurium conferred MDR phenotype higher than S. Enteritidis with multiple antibiotic resistance indexes of 0.22 and 0.04, respectively. Here, we characterized the important S. Typhimurium, S. Enteritidis, and human clinical factors of NTS within the region.

Genomic typing and virulence gene profile analysis of Salmonella Derby from different sources

Salmonella enterica serovar Derby (S. Derby) is one of the most common Salmonella serovars which can infect poultry, swine, and humans. With the reduction of the sequencing cost and the improvement of sequencing technology, whole genome sequencing (WGS) has become an important method for bacterial determination, molecular investigation, and pathogenic tracing analysis. In this study, we investigated S. Derby isolates from different sources in China using in-silico multilocus sequence typing (MLST), core genome MLST (cgMLST) and whole genome MLST (wgMLST) analysis based on WGS. The results showed that 21 S. Derby strains were divided into 3 STs using MLST analysis, including ST40 (n = 19, accounting for 90.48%), ST71 (n = 1, accounting for 4.76%) and ST8016 (n = 1, accounting for 4.76%). cgMLST and wgMLST analysis categorized the tested strains into 13 cgSTs and 21 wgSTs, respectively. The minimum spanning trees of cgMLST and wgMLST both divided these strains into 3 clusters and 4 singletons. In addition, virulence gene profiles of S. Derby isolates were also analyzed, and a total of 174 virulence genes belonged to 8 categories were identified. In summary, we studied genomic typing, phylogenetic relationship and virulence gene profiles of S. Derby strains from different sources in China. These findings were beneficial for the epidemiology and pathogenesis of Salmonella.

Molecular and pathological investigation of avian reovirus (ARV) in Egypt with the assessment of the genetic variability of field strains compared to vaccine strains

Avian orthoreovirus (ARV) is among the important viruses that cause drastic economic losses in the Egyptian poultry industry. Despite regular vaccination of breeder birds, a high prevalence of ARV infection in broilers has been noted in recent years. However, no reports have revealed the genetic and antigenic characteristics of Egyptian field ARV and vaccines used against it. Thus, this study was conducted to detect the molecular nature of emerging ARV strains in broiler chickens suffering from arthritis and tenosynovitis in comparison to vaccine strains. Synovial fluid samples (n = 400) were collected from 40 commercial broiler flocks in the Gharbia governorate, Egypt, and then pooled to obtain 40 samples, which were then used to screen ARV using reverse transcriptase polymerase chain reaction (RT-PCR) with the partial amplification of ARV sigma C gene. The obtained RT-PCR products were then sequenced, and their nucleotide and deduced amino acid sequences were analyzed together with other ARV field and vaccine strains from GenBank. RT-PCR successfully amplified the predicted 940 bp PCR products from all tested samples. The phylogenetic tree revealed that the analyzed ARV strains were clustered into six genotypic clusters and six protein clusters, with high antigenic diversity between the genotypic clusters. Surprisingly, our isolates were genetically different from vaccine strains, which aligned in genotypic cluster I/protein cluster I, while our strains were aligned in genotypic cluster V/protein cluster V. More importantly, our strains were highly divergent from vaccine strains used in Egypt, with 55.09-56.23% diversity. Sequence analysis using BioEdit software revealed high genetic and protein diversity between our isolates and vaccine strains (397/797 nucleotide substitutions and 148-149/265 amino acid substitutions). This high genetic diversity explains the vaccination failure and recurrent circulation of ARV in Egypt. The present data highlight the need to formulate a new effective vaccine from locally isolated ARV strains after a thorough screening of the molecular nature of circulating ARV in Egypt.

Retail chicken giblets contaminated with extended-spectrum cephalosporin- and carbapenem-resistant Salmonella enterica carrying blaCMY-2

Background and Aim:

Chickens are considered as the main source of Salmonella, with infection potentially spreading to the public through outlets. The study aimed to investigate poultry shops for Salmonella enterica resistant to extended-spectrum cephalosporins-resistant (ESCR) and carbapenems-resistant (CR).

Materials and Methods:

Samples were collected from chicken giblets, water tanks, and workers at retail shops. Salmonella was isolated and serotyped; the presence of invA, stn, ompA, and ompF was determined using polymerase chain reaction (PCR). The isolates were tested for ESCR and CR by a disk-diffusion test; a confirmatory extended-spectrum β-lactamase (ESBL) test was performed by combinational disk-diffusion test with clavulanic acid. The resistant isolates were screened for ESBL (blaTEM, blaSHV, blaCTX-M, and blaOXA-1), AmpC blaCMY-2, and carbapenemase (blaKPC, blaNDM, and blaOXA-48) genes using PCR.

Results:

S. enterica was isolated from chicken giblets (13/129) and the 13 isolates were ESCR. Based on the confirmatory ESBL test and CR, the 13 isolates were classified into the following resistance phenotypes: ESBL-producing and CR (n=4), ESBL-producing (n=1), non-ESBL-producing and CR (n=6), and non-ESBL-producing (n=2). All the five isolates with ESBL-producing phenotype carried predominantly blaTEM, blaSHV, and blaCMY-2. Regardless of being phenotypically CR, none of these isolates carried any of the tested carbapenemase genes. Surprisingly, the isolates with non-ESBL phenotype were found to carry blaTEM, blaSHV, and blaCMY-2. The blaKPC was present mainly in the isolates with non-ESBL and CR phenotypes. Interestingly, two isolates of the non-ESBL and CR phenotype showed resistance to cefepime, the fourth generation cephalosporins. Salmonella was also recovered from the water tanks (2/7) and the workers (2/16). The four isolates were ESCR and showed a non-ESBL-producing and CR phenotype; they harbored blaTEM, blaSHV, blaOXA-1, and blaKPC. The blaCMY-2 was found in one isolate from water and one from humans. All Salmonella isolates carried invA, stn, ompA, and ompF.

Conclusion:

Virulent ESCR S. enterica were identified in retail shops. The isolates carried blaCMY-2 and ESBL-genes, with a high proportion showing CR. Transmission of such strains to humans through food leads us to recommend regular inspection of retail outlets for antibiotic-resistant bacteria.

Molecular Characterization of Salmonella Detected along the Broiler Production Chain in Trinidad and Tobago

This cross-sectional study determined the serovars, antimicrobial resistance genes, and virulence factors of Salmonella isolated from hatcheries, broiler farms, processing plants, and retail outlets in Trinidad and Tobago. Salmonella in silico serotyping detected 23 different serovars where Kentucky 20.5% (30/146), Javiana 19.2% (28/146), Infantis 13.7% (20/146), and Albany 8.9% (13/146) were the predominant serovars. There was a 76.0% (111/146) agreement between serotyping results using traditional conventional methods and whole-genome sequencing (WGS) in in silico analysis. In silico identification of antimicrobial resistance genes conferring resistance to aminoglycosides, cephalosporins, peptides, sulfonamides, and antiseptics were detected. Multidrug resistance (MDR) was detected in 6.8% (10/146) of the isolates of which 100% originated from broiler farms. Overall, virulence factors associated with secretion systems and fimbrial adherence determinants accounted for 69.3% (3091/4463), and 29.2% (1302/4463) counts, respectively. Ten of 20 isolates of serovar Infantis (50.0%) showed MDR and contained the bla_CTX-M-65 gene. This is the first molecular characterization of Salmonella isolates detected along the entire broiler production continuum in the Caribbean region using WGS. The availability of these genomes will help future source tracking during epidemiological investigations associated with Salmonella foodborne outbreaks in the region and worldwide.

Occurrence, Risk Factors, Serotypes, and Antimicrobial Resistance of Salmonella Strains Isolated from Imported Fertile Hatching Eggs, Hatcheries, and Broiler Farms in Trinidad and Tobago

ABSTRACT

This cross-sectional study was conducted to determine the occurrence, risk factors, and characteristics of Salmonella isolates recovered from imported fertile broiler hatching eggs, hatcheries, and broiler farms in Trinidad and Tobago. Standard methods were used to isolate and characterize Salmonella isolates from two broiler hatcheries and 27 broiler farms in the country. The frequency of isolation of Salmonella was 0.0% for imported fertile hatching eggs (0 of 45 pools of 10 eggs each, i.e., 450 eggs), 7.6% for hatcheries (12 of 158 samples), and 2.8% for broiler farms (24 of 866 samples) (P = 0.006). Stillborn chicks at hatcheries had the highest prevalence of Salmonella (7 of 28 samples, 28.0%), whereas on broiler farms the cloacal swabs had the highest prevalence of Salmonella (15 of 675 samples, 2.2%). None of the 15 farm management and production practices investigated were significantly associated (P > 0.05) with the isolation of Salmonella. The predominant Salmonella serotypes were Kentucky (83.3%) and Infantis (62.5%) among hatchery and farm isolates, respectively. The disk diffusion method revealed frequencies of antimicrobial resistance (i.e., resistance to one or more agents) of 44.0% (11 of 25 isolates) and 87.5% (35 of 40 isolates) at hatcheries and broiler farms, respectively (P = 0.0002). Antimicrobial resistance among hatchery isolates was highest (28.0%) to doxycycline and kanamycin and was very high (>65%) among farm isolates to sulfamethoxazole-trimethoprim, gentamicin, ceftriaxone, kanamycin, and doxycycline. Multidrug resistance (MDR; i.e., resistance to antimicrobial agents from three or more classes) was exhibited by 4.0 and 85.7% of Salmonella isolates recovered from several environmental and animal sources at the hatcheries and farms, respectively (P < 0.0001). The high level of antimicrobial resistance and the presence of MDR among Salmonella isolates from broiler farms highlight the therapeutic implications and the potential for MDR strains to enter the food chain.

HIGHLIGHTS

Highly prevalent multidrug resistance and QRDR mutations in Salmonella isolated from chicken, pork and duck meat in Southern China, 2018-2019

This study was undertaken to investigate the prevalence, serotype distribution and antimicrobial resistance in Salmonella isolated from retail meat in Southern China, and to characterize the major mechanisms that mediate the ciprofloxacin resistance of isolates. High levels of Salmonella contamination were detected in pork (67.0%), duck (50.5%) and chicken (46.2%). Thirty different serotypes were identified among 500 detected Salmonella isolates, as well as significant differences in serotypes between different retail meat samples. Notably, 405 (80.1%) isolates exhibited multidrug resistance (MDR). Meanwhile, we also found that 74 (14.8%) Salmonella isolates were resistant to ciprofloxacin and the major mechanisms underlying this resistance were investigated. The commonest mutations in gyrA S83F (40.5%) and D87N (35.1%), and in parC was T57S (71.6%) and S80I (35.1%). Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) analysis revealed that the S. Kentucky isolates that were resistant to ciprofloxacin mostly belonged to ST198 (21/23, 91.3%) and PFGE revealed the presence of various genotypes. This study identified a diversity of Salmonella serotypes and a high prevalence of multidrug resistance (MDR) among Salmonella isolated from retail meat in Southern China, which indicates that foodborne Salmonella potentially constitutes a potential food safety risk.

Extended-spectrum β-lactamase-producing Salmonella serovars among healthy and diseased chickens and their public health implication

OBJECTIVES

This study investigated the occurrence of extended-spectrum β-lactamase (ESBL)-producing Salmonella and the associated virulence genes among farmed chickens.

METHODS

Cloacal swab samples were collected from apparently healthy and diseased chickens and were cultured for Salmonella using conventional methods. The isolates were serotyped using slide agglutination tests and were examined by polymerase chain reaction (PCR) for the virulence genes invA, stn, svpC and pefA and the outer membrane protein-encoding genes ompA and ompF. Screening for ESBL resistance was performed using the disk-diffusion test, the combinational-disk test with clavulanic acid, and multiplex PCR for bla_TEM, bla_SHV, bla_CTX-M and bla_OXA. The presence of the AmpC bla_CMy-2 was tested among the ESBL-negative isolates by uniplex PCR. The resistant isolates were partially sequenced based on the stn gene.

RESULTS

The Salmonella isolation rate was 3.4% (6/175) from healthy and 11.1% (14/126) from diseased chickens. The 20 isolates belong to serotypes with public health significance like Typhimurium, Kentucky and Infantis. All the isolates possess invA, stn, svpC and ompF genes; 16 isolates harboured ompA, and one carried pefA. Of the 20 isolates, 19 were resistant to more than one antibiotic. Of these 19 isolates, 16 were ESBL-producing with the majority carrying bla_TEM and bla_SHV genes. The four ESBL-negative isolates carried bla_CMY-2. Partial-stn-sequencing of the isolates revealed a high genetic relatedness to Salmonella strains from patients in Egypt and Asia.

CONCLUSIONS

Virulent ESBL-producing Salmonella was isolated from healthy and diseased chickens; the strains have a close relationship to human strains, posing a public health threat.

Molecular epidemiology of Salmonella Infantis in Europe: insights into the success of the bacterial host and its parasitic pESI-like megaplasmid

Salmonella Infantis is one of the five serovars most frequently causing human salmonellosis in Europe, mainly associated with poultry. A clone harbouring a conjugative plasmid of emerging S. Infantis (pESI)-like megaplasmid, carrying multidrug resistant (MDR) and extended-spectrum beta-lactamases (ESBL) genes, has spread in the Italian broiler chicken industry also causing human illness. This work is aimed at elucidating the molecular epidemiology of S. Infantis and pESI-like in Europe using whole-genome sequencing and bioinformatics analysis, and to investigate the genetic relatedness of S. Infantis clones and pESI-like from animals, meat, feed and humans provided by institutions of nine European countries. Two genotyping approaches were used: chromosome or plasmid SNP-based analysis and the minimum spanning tree (MST) algorithm based on core-genome multilocus sequence typing (cgMLST). The European S. Infantis population appeared heterogeneous, with different genetic clusters defined at core-genome level. However, pESI-like variants present in 64.1 % of the isolates were more genetically homogeneous and capable of infecting different clonal lineages in most of the countries. Two different pESI-like with ESBL genes (n=82) were observed: bla_CTX-M-1-positive in European isolates and bla_CTX-M-65-positive in American isolates (study outgroup). Both variants had toxin-antitoxin systems, resistance genes towards tetracyclines, trimethoprim, sulphonamides and aminoglycosides, heavy metals (merA) and disinfectants (qacEΔ). Worryingly, 66 % of the total isolates studied presented different gyrA chromosomal point mutations associated with (fluoro)quinolone resistance (MIC range 0.125–0.5 mg/L), while 18 % displayed transferable macrolide resistance mediated by mph, mef and erm(B) genes. Proper intervention strategies are needed to prevent further dissemination/transmission of MDR S. Infantis and pESI-like along the food chain in Europe.

Photothermal versus photodynamic treatment for the inactivation of the bacteria Escherichia coli and Bacillus cereus: An in vitro study

The widespread occurrence of microbial pathogens, including multidrug-resistant (MDR) bacteria, has ignited research efforts to discover alternative strategies to combat infections in patients. Recently, photodynamic therapy (PDT) and photothermal therapy (PTT) have been proposed for the inactivation of pathogens. Although PDT and PTT are very promising antipathogenic tools, further effort is needed to determine their real impact on pathogens apart from the effects of individual elements involved in the photodynamic/photothermal processes, i.e., light, photosensitizers (PSs), and nanoparticles. Accordingly, in the current study, toluidine blue O (TBO) and gold nanoparticles (GNP) were used as generators of reactive oxygen species (ROS) and hyperthermia in the presence of light, respectively. Escherichia coli (E. coli) and Bacillus cereus (B. cereus) bacteria were chosen as examples of gram-negative and gram-positive bacteria, respectively. Before the bactericidal activity of PDT was assessed, the aggregation of TBO and its effect on the growth of both strains of bacteria were studied. Additionally, E. coli and B. cereus were exposed to a range of doses of 633 nm helium-neon laser light to investigate its effect. In a separate set of experiments, the bactericidal activity of PTT was assessed after the effects of GNP and green light (530 nm) had been assessed. The results showed that PDT and PTT should be considered useful tools for bacterial eradication even when the light, PSs, and nanoparticles are each used at doses safe for bacterial growth. Moreover, different photodynamic responses were observed for E. coli and B. cereus, and light from a 633 nm laser and a 530 nm light-emitting diode (LED) showed disparate responses when applied alone to both bacteria.