The consequences of a sudden demographic change on the seroprevalence pattern, virulence genes, identification and characterisation of integron-mediated antibiotic resistance in the Salmonella enterica isolated from clinically diarrhoeic humans in Egypt

Virulence genes and antimicrobial susceptibility in Salmonellaenterica serotypes isolated from swine production in Argentina

Salmonella is a worldwide-distributed pathogen that affects both humans and animals and is usually associated with intensive animal production such as poultry and swine. This bacterium carries different virulence genes, whose expression favors its interaction with the host and may influence the course of the infection. Extended usage of antibiotics for metaphylaxis or prophylaxis and as growth promoters favors the emergence of multiresistant Salmonella strains. The aim of this work was to assess the association between the presence of virulence-associated genes and the antimicrobial resistance phenotype in Salmonella isolates obtained from swine intensive and backyard farms in Argentina during 2012-2018. A total of 59 Salmonella strains belonging to several serotypes were studied. All the strains carried the sopB and ssaQ genes, whereas more than 90% of the isolates carried the mgtC, avrA, and siiD genes. Some isolates also carried the bcfC, sodC1, gipA, sopE1 and spvC genes; however, their presence varied among them. Susceptibility to the antibiotics tested was diverse. Isolates from intensive farms were resistant to a larger number of antimicrobials than those from backyard farms and some of the strains showed high virulence potential and extensive antimicrobial resistance profiles. Continuous surveillance is essential to detect the emergence of strains that may represent a significant risk not only for animal production but also for the human population.

Serotypes, antibiotic resistance, and virulence genes of Salmonella in children with diarrhea

BACKGROUND

Salmonella is an important foodborne pathogen that causes acute diarrhea in humans worldwide. This study analyzed the relationships of serotypes and antibiotic resistance with virulence genes of Salmonella isolated from children with salmonellosis.

METHODS

Serological typing was performed using the slide-agglutination method. The Kirby-Bauer disk diffusion method was used to test antibiotic susceptibility. Twenty virulence genes were detected by PCR.

RESULTS

Salmonella Typhimurium (21 isolates, 34.43%) and S Enteritidis (12 isolates, 19.67%) were the predominant species among the 61 isolates. Ampicillin resistance was most common (63.93%), and among the cephalosporins, resistance was most often found to cefotaxime, a third-generation cephalosporin (19.67%). Among the 20 virulence genes, prgH, ssrB, and pagC were detected in all Salmonella isolates. In S Typhimurium, the detection rates of hilA, sipB, marT, mgtC, sopB, pagN, nlpI, bapA, oafA, and tolC were high. In S Enteritidis, the detection rates of icmF, spvB, spvR, and pefA were high. Nitrofurantoin resistance was negatively correlated with the virulence gene bapA (P = .005) and was positively correlated with icmF, spvB, spvR, and pefA (P = .012, .008, .002, and .005, respectively), The P values between all other virulence genes and antibiotic resistance were >.05.

CONCLUSION

Salmonella Typhimurium and S Enteritidis were the main serotypes in children with diarrhea in Hangzhou, China. Salmonella exhibited a high level of resistance to common antibiotics, and a high rate of bacteria carrying virulence genes was observed. However, no significant correlation was found between virulence genes and resistance to common antibiotics.

Epidemiology of common resistant bacterial pathogens in the countries of the Arab League

No uniformly organised collection of data regarding antimicrobial resistance has occurred in the countries of the Arab League. 19 countries of the Arab League have published data for antimicrobial susceptibility for the WHO priority organisms, and seven of 14 of these organisms are included in this Review (Escherichia coli, Klebsiella spp, Pseudomonas aeruginosa, Acinetobacter baumannii, Salmonella spp, Staphylococcus aureus, and Streptococcus pneumoniae). Although E coli and Klebsiella spp resistance to third-generation cephalosporins is common in all countries, with prevalence reaching more than 50% in Egypt and Syria, carbapenem resistance is emerging, albeit with a prevalence of less than 10%. Conversely, a large amount of carbapenem resistance has been reported for P aeruginosa and A baumannii across the Arab League, reaching 50% and 88% of isolates in some countries. As for Salmonella spp, the prevalence of fluoroquinolone resistance has exceeded 30% in several areas. With regards to the Gram-positive pathogens, the prevalence of meticillin resistance in S aureus is reported to be between 20% and 30% in most countries, but exceeds 60% in Egypt and Iraq. The prevalence of penicillin non-susceptibility among pneumococci has reached more than 20% in Algeria, Egypt, Morocco, Saudi Arabia, and Tunisia. These findings highlight the need for structured national plans in the region to target infection prevention and antimicrobial stewardship.

Comparative Study on Antibiotic Resistance and DNA Profiles of Salmonella enterica Serovar Typhimurium Isolated from Humans, Retail Foods, and the Environment in Shanghai, China

We characterized antibiotic resistance profiles, antibiotic resistance-associated genes, and pulsed-field gel electrophoresis (PFGE) patterns of 145 Salmonella enterica serotype Typhimurium isolates from human infections and retail foods that were possibly responsible for salmonellosis outbreaks from 2008 to 2012 in Shanghai, China. Resistance to at least three antibiotics was found in 66.7% of chicken isolates, 76.5% of duck isolates, 77.8% of pork isolates, and 80.5% of human isolates. Seven antibiotic resistance phenotypes were detected in chicken isolates, 16 in pork isolates, 17 in duck isolates, and 50 in human isolates. No significant difference (p > 0.05) was found between Salmonella isolates derived from human salmonellosis and from retail foods in terms of the percent resistance of ampicillin, amoxicillin/clavulanic acid, ceftiofur, ceftriaxone, nalidixic acid, chloramphenicol, gentamicin, kanamycin, streptomycin, tetracycline, sulfisoxazole, and sulfamethoxazole/trimethoprim. PFGE using XbaI and BlnI showed that some Salmonella isolates recovered from human infections and retail foods had same or highly similar genetic profile. Same or similar antibiotic resistance profiles, antibiotic resistance associated genes (i.e., qnrA, qnrB, qnrS, aac(6')-Ib, and oqxAB), gene cassettes (i.e., aadA2, dfrA12-aadA2, and aadA1), and mutations were detected in those isolates that exhibited high genetic similarities. These findings highlighted the frequent presence of Salmonella Typhimurium in retail chicken, pork, duck, and humans.

Prevalence of Virulence Genes in Extended-Spectrum β-lactamases (ESBLs)-Producing Salmonella in Retail Raw Chicken in China

Extended-spectrum β-lactamases (ESBLs)-producing Salmonella is a tremendous hazard to food safety and public health. The objective of this study was to determine the prevalence of 30 virulence genes (avrA, sipA, sseC, marT, rhuM, siiE, pipA, pipD, envR, gogB, gtgA, sodC1, sseI, irsA, sopE2, spvC, rck, spvR, fhuA, msgA, pagK, srfj, stkc, fimA, lpfD, pefA, stcC, steB, stjB, and tcfA) in 156 ESBLs-producing Salmonella isolates that belonged to 21 serotypes. These isolates were recovered from retail raw chicken samples collected from 5 provinces and 2 national cities in China between 2007 and 2012. The results indicated that 154 (98.7%) ESBLs-producing Salmonella isolates carried at least 1 virulence gene, 138 (88.5%) simultaneously carried at least 5 virulence genes, 107 (68.6%) carried 10 or more, and 20 (12.8%) carried 15 or more virulence genes. The most frequently detected virulence genes were marT (n = 127, 81.4%), siiE (n = 126, 80.8%), msgA (n = 121, 77.6%), and sipA (n = 121, 77.6%). Significant difference was identified between detection percentages of virulence genes of rhuM, pipD, envR, sopE2, pagK, lpfD, steB, and stjB in S. Indiana, S. Thompson, S. Enteritidis, S. Typhimurium, S. Shubra, S. Edinburg, and S. Agona isolates. Distribution of virulence genes were significantly influenced by sampling districts (P < 0.01), especially for sodC1 and pipD, and then were msgA and sopE2. The heatmap showed the frequencies of virulence genes in ESBLs-producing isolates from retail chickens in southern, central, and northern regions of China were completely different from each other. Based on our findings, ESBLs-producing Salmonella of retail chicken origin were common carriers of multiple virulence genes and were regionally distributed.

Serotype Distribution, Antimicrobial Resistance, and Class 1 Integrons Profiles of Salmonella from Animals in Slaughterhouses in Shandong Province, China

The current study aimed to analyze the prevalence and characterization of Salmonella enterica isolated from animals in slaughterhouses before slaughter. A total of 143 non-duplicate Salmonella were recovered from 1,000 fresh fecal swabs collected from four major pig slaughterhouses (49/600, 8.2%) and four major chicken slaughterhouses (94/400, 23.5%) between March and July 2016. Among Salmonella isolates from pigs, the predominant serovars were Salmonella Rissen (28/49, 57.1%) and Typhimurium (14/49, 28.6%), and high antimicrobial resistance rates were observed for tetracycline (44/49, 89.8%) and ampicillin (16/49, 32.7%). Class 1 integrons were detected in 10.2% (5/49) of these isolates and all contained gene cassettes aadA2 (0.65 kb). Two β-lactamase genes were detected among these isolates, and most of these isolates carried blaTEM-1 (46/49), followed by blaOXA-1(4/49). Seven STs (MLST/ST, multilocus sequence typing) were detected in these isolates, and the predominant type was ST469 (19.6%). Among Salmonella isolates from chickens, the predominant serovars were Salmonella Indiana (67/94, 71.3%) and Enteritidis (23/94, 24.5%), and high antimicrobial resistance rates were observed for nalidixic acid (89/94, 94.7%), ampicillin (88/94, 93.6%) and tetracycline (81/94, 86.2%). Class 1 integrons were detected in 23 isolates (23/94, 24.5%), which contained empty integrons (0.15 kb, n = 6) or gene cassettes drfA17-aadA5 (1.7 kb, n = 6), aadA2 (1.2 kb, n = 5), drfA16-blaPSE-1-aadA2-ereA2 (1.6 kb, n = 5) or drfA1-aadA1 (1.4 kb, n = 1). Three β-lactamase genes were detected, and all 94 isolates carried blaTEM-1, followed by blaCTX-M-55 (n = 19) and blaSPE-1 (n = 3). Five STs were found in these isolates, and the predominant type was ST17 (71.3%). Our findings indicated that Salmonella was widespread in animals at slaughter and may be transmitted from animal to fork.

Prevalence and molecular characterization of Salmonella enterica isolates throughout an integrated broiler supply chain in China

A total of 1145 samples were collected from chicken breeder farms, hatcheries, broiler farms, a slaughterhouse and retail refrigerated chicken stores in an integrated broiler supply chain in Guangdong Province, China, in 2013. One-hundred and two Salmonella enterica strains were isolated and subjected to serotyping, antimicrobial susceptibility testing, virulence profile determination and molecular subtyping by pulsed field gel electrophoresis (PFGE). The contamination rates in samples from breeder farms, hatcheries, broiler farms, the slaughterhouse and retail stores were 1·46%, 4·31%, 7·00%, 62·86% and 54·67%, respectively. The isolated strains of S. enterica belonged to 10 serotypes; most of them were S. Weltevreden (46·08%, 47/102) and S. Agona (18·63%, 19/102). Isolates were frequently resistant to streptomycin (38·2%), tetracycline (36·3%), sulfisoxazole (35·3%) and gentamicin (34·3%); 31·4% of isolates were multidrug resistant. The isolates were screened for 10 virulence factors. The Salmonella pathogenicity island genes avrA, ssaQ, mgtC, siiD, and sopB and the fimbrial gene bcfC were present in 100% of the strains. PFGE genotyping of the 102 S. enterica isolates yielded 24 PFGE types at an 85% similarity threshold. The PFGE patterns show that the genotypes of S. enterica in the production chain are very diverse, but some strains have 100% similarity in different parts of the production chain, which indicates that some S. enterica persist throughout the broiler supply chain.

Characterization of Virulence-Associated Genes, Antimicrobial Resistance Genes, and Class 1 Integrons in Salmonella enterica serovar Typhimurium Isolates from Chicken Meat and Humans in Egypt

Foodborne pathogens are leading causes of illness especially in developing countries. The current study aimed to characterize virulence-associated genes and antimicrobial resistance in 30 Salmonella Typhimurium isolates of chicken and human origin at Mansoura, Egypt. The results showed that invA, avrA, mgtC, stn, and bcfC genes were identified in all the examined isolates, while 96.7% and 6.7% were positive for sopB and pef genes, respectively. The highest resistance frequencies of the isolates were to chloramphenicol and trimethoprim-sulfamethoxazole (73.3%, each), followed by streptomycin (56.7%), tetracycline and ampicillin (53.3%, each), and gentamicin (30%). However, only 2.7% of the isolates were resistant to cefotaxime and ceftriaxone each. Different resistance-associated genes, including blaTEM, aadB, aadC, aadA1, aadA2, floR, tetA(A), tetA(B), and sul1, were identified in Salmonella Typhimurium isolates with the respective frequencies of 53.3%, 6.7%, 23.3%, 46.7%, 63.3%, 73.3%, 60%, 20%, and 96.7%. None of the isolates was positive for blaSHV, blaOXA, and blaCMY genes. The results showed that the intI1 gene was detected in 24 (80%) of the examined Salmonella Typhimurium isolates. Class 1 integrons were found in 19 (79.2%) isolates that were intI1 positive. Seven integron profiles (namely: P-I to P-VII) were identified with P-V (gene cassette dfrA15, aadA2), the most prevalent profile. To the best of our knowledge, this is the first study to characterize the unusual gene cassette array dfrA12-OrfF-aadA27 from Salmonella Typhimurium isolates in Egypt.