Quinolone susceptibility and genetic characterization of Salmonella enterica subsp. enterica isolated from pet turtles

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.

Emergence and genomic characteristics of multi-drug-resistant Salmonella in pet turtles and children with diarrhoea

Pet turtles are a well-recognized source of human salmonellosis, posing a threat to human health, particularly children who commonly keep pet turtles. To date, the genomic characteristics of Salmonella among pet turtles and children has not been well described. We investigated the prevalence, antimicrobial resistance (AMR) and genomic characteristics of Salmonella from pet turtles in Beijing, China. In total, 9.6 % (46/480) of pet turtles were positive for Salmonella with S. Thompson being the dominant serovar (19/46) in 2019. Moreover, 80.4 % of Salmonella were multi-drug resistant (MDR) and 60.7 % were resistant to ampicillin, streptomycin, sulfonamides and tetracycline (ASSuT). We further compared the genomes of S. Thompson isolates from pet turtles (n=19) with those from children with diarrhoea (n=28) in the same region and year, most of which were sequence type (ST)26, with one novel ST7937 identified from a child-associated isolate. S. Thompson isolates from children with diarrhoea exhibited less resistance than isolates from pet turtles. Most MDR isolates possessed multiple AMR genes, including the AmpC β-lactamase-encoding genes bla DHA-15 and bla DHA-1 which co-occurred with the IncA/C and IncHI plasmid replicon types. To the best of our knowledge, this is the first time that the bla DHA-15 gene has been detected from Salmonella. Several pet turtle-associated S. Thompson isolates comprised phylogenetically close clusters with those from children with diarrhoea (<20 SNP differences). Bayesian analysis demonstrated that the Chinese ST26 S. Thompson strains had a recent evolutionary history and evolved into two major clades, with one clade acquiring various resistant plasmids. Our findings revealed the emergence of MDR Salmonella among pet turtles in China and provided evidence for the interspecies transmission of S. Thompson.

Epidemiological Study on Prevalence, Serovar Diversity, Multidrug Resistance, and CTX-M-Type Extended-Spectrum β-Lactamases of Salmonella spp. from Patients with Diarrhea, Food of Animal Origin, and Pets in Several Provinces of China

A total of 2,283 Salmonella isolates were recovered from 18,334 samples, including samples from patients with diarrhea, food of animal origin, and pets, across 5 provinces of China. The highest prevalence of Salmonella spp. was detected in chicken meats (39.3%, 486/1,237). Fifteen serogroups and 66 serovars were identified, with Salmonella enterica serovars Typhimurium and Enteritidis being the most dominant. Most (85.5%, 1,952/2,283) isolates exhibited resistance to ≥1 antimicrobial, and 56.4% were multidrug resistant (MDR). A total of 222 isolates harbored extended-spectrum β-lactamases (ESBLs), and 200 of these were of the CTX-M type and were mostly detected in isolates from chicken meat and turtle fecal samples. Overall, eight blaCTX-M genes were identified, with blaCTX-M-65, blaCTX-M-123, blaCTX-M-14, blaCTX-M-79, and blaCTX-M-130 being the most prevalent. In total, 166 of the 222 ESBL-producing isolates had amino acid substitutions in GyrA (S83Y, S83F, D87G, D87N, and D87Y) and ParC (S80I), while the plasmid-mediated quinolone resistance (PMQR)-encoding genes oqxA, oqxB, qepA, qnrB, and qnrS were detected in almost all isolates. Of the 15 sequence types (STs) identified in the 222 ESBLs, ST17, ST11, ST34, and ST26 ranked among the top 5 in number of isolates. Our study revealed considerable serovar diversity and a high prevalence of the co-occurrence of MDR determinants, including CTX-M-type ESBLs, quinolone resistance-determining region (QRDR) mutations, and PMQR genes. This is the first report of CTX-M-130 Salmonella spp. from patients with diarrhea and QRDR mutations from turtle fecal samples. Our study emphasizes the importance of actions, both in health care settings and in the veterinary medicine sector, to control the dissemination of MDR, especially the CTX-M-type ESBL-harboring Salmonella isolates.

A Review of the Public Health Challenges of Salmonella and Turtles

Non-typhoidal Salmonella serovars are recognized as zoonotic pathogens. Although human salmonellosis is frequently associated with ingestion of contaminated foods of animal origin, contact with animals may also be a significant source of Salmonella infection, especially contact with turtles, which have shown to be an important reservoir of Salmonella, specifically through their intestinal tracts. Turtles are among the most common reptiles kept as house pets that may pose a public health risk associated with Salmonella exposure, especially among infants and young children. This review discusses the literature reporting the link between turtles and Salmonella as well as turtle-associated human salmonellosis in the last ten years. In most outbreaks, a high proportion of patients are children under five years of age, which indicates that children are at the greatest risk of turtle-associated salmonellosis. Therefore, turtles should not be preferred as recommended pets for children under five years of age. Reducing turtle stress to minimise Salmonella shedding as well as providing client education handouts at the points of sale of these animals may reduce the risk of transmitting such significant pathogen to humans. Further studies are required to investigate the role of both direct contact with turtles as well as indirect contact through cross-contamination in the transmission of turtles-associated Salmonella to humans.

The genetic background of antibiotic resistance among clinical uropathogenic Escherichia coli strains

The spreading mechanisms of antibiotic resistance are related to many bacterial and environment factors. The overuse of antibiotics is leading to an unceasing emergence of new multidrug resistant strains. This problem also concerns uropathogenic Escherichia coli strains, which is the most common pathogen causing urinary tract infections. The aim of this study was the genetic analysis of antibiotic resistance in comparison to the phenotypic background of E. coli strains. The characterized collection of E. coli strains isolated 10 years ago from the urine samples of patients with urinary tract infections was used for antimicrobial susceptibility testing (the disc diffusion method) and analysis of antibiotic resistance genes (PCR reaction, sequencing). Additionally, the presence of ESBL strains was analyzed. Fourteen genes were associated with resistance to beta-lactams, aminoglycosides, sulfonamides and quinolones. The genetic analysis revealed that bla_TEM-1 and sul2 were present in almost all of the studied strains. Other drug-resistance genes were very rare or non-existent. Otherwise, the phenotypic resistance to fluoroquinolones was well correlated with the genotypic background of the studied bacteria. The presence of particular genes and specific mutations indicate a high bacterial potential to multidrug resistance. On the other hand, it needs to be emphasized that the standard disk diffusion test for the routine antimicrobial susceptibility analysis is still the best way to estimate the current situation of bacterial drug-resistance.