Antimicrobial resistance, Extended-Spectrum β-Lactamase production and virulence genes in Salmonella enterica and Escherichia coli isolates from estuarine environment

Serovar distribution, virulence gene and antibiotic susceptibility profiling of Salmonella enterica isolated from seafood in Mumbai, India

Salmonella contamination of seafood and its environment is an important public health concern. In this study, Salmonella enterica isolated from seafood in Mumbai, India were seroptyped and further characterized with respect to the distribution of virulence genes associated with Salmonella Pathogenicity Islands (SPIs) and their antimicrobial susceptibilities. The study included 89 isolates which were screened for 11 genes associated with five pathogenicity islands (SPI-1 to SPI-5), two phage-encoded virulence genes, and an enterotoxin gene. The isolates were serotyped into 10 serovars namely S. Typhimurium, S. Bareilly, S. Weltevreden, S. Volta, S. Newport, S. Tennessee, S. Kentucky, S. Lindenburg, S. Paratyphi B and S. Alachua. S. Bareilly (33) was the predominant serovar, followed by S. Typhimurium (15), S. Newport (10), S. Kentucky (9), S. Paratyphi B (8), and S. Tennessee (7). Ten S. Typhimurium and one each of S. Kentucky and S. Paratyphi B isolates possessed all the virulence genes tested, while the remaining isolates lacked one or more virulence genes. The antibiotic susceptibility testing revealed that the isolates were resistant against third-generation cephalosporins, quinolones, fluoroquinolones and tetracycline antibiotics, but sensitive to ceftazidime, aztreonam, carbapenems, chloramphenicol, and aminoglycosides. The diverse serovars of Salmonella contaminating fresh seafood in this geographical region constitute a notable public health concern.

Emerging multi-drug resistant and extended-spectrum β-lactamase (ESBL)-positive enterotoxigenic E. coli (ETEC) clones circulating in aquatic environments and in patients

Diarrheal disease pathogens often spread through water-borne routes. Enterotoxigenic Escherichia coli (ETEC) is a major bacterial agent causing diarrheal disease in children, adults, and travelers in endemic areas. In addition, ETEC is responsible for outbreaks of water and food-borne gasteroenteritis globally, ETEC isolates also show robust survival capacity in various environmental settings, including aquatic environments. During the last decade, studies of ETEC isolates have indicated a rapid increase in multi-drug resistant and extended-spectrum β-lactamase (ESBL)-positive human-specific ETEC strains. These have been found in both environmental water sources and human patients, warranting the urgent need for focused monitoring of antibiotic resistance development in ETEC. Whole genome sequencing (WGS) of isolates from environmental, animal, and human sources enables in silico surveillance of emerging pathogenic and multi-drug resistant strains. This method allows for re-analysis of genomic data, aiding in identification of new variants of pathogenic clones. By integrating data from diverse sources inclusing sequenced isolates, we found that certain ETEC clonal lineages e.g., those expressing certain toxin-colonization factor profiles including STp/CS6, LT STh/CS2 + CS3, and LT STh/CFA/I are more at risk to develop multi-drug resistance than other ETEC lineages. Comparizon of multi-locus sequence types from papers with WGS data indicated ST182, ST4, ST2332 and new ST types to be emerging multi-drug resistant ETEC. We conclude that further studies on sequenced ETEC/E. coli genomes are needed to enhance our understanding of the dynamics of ETEC evolution, and the relation of virulence and resistance profiles in both environmental and clinical isolates.

Meat ducks as carriers of antimicrobial-resistant Escherichia coli harboring transferable R plasmids

IMPORTANCE

Antimicrobial resistance (AMR) is a serious public health threat. AMR bacteria and their resistance determinants in food can be transmitted to humans through the food chain and by direct contact and disseminate directly to the environment.

OBJECTIVE

This study examined the AMR characteristics and transferable R plasmids in Escherichia coli isolated from meat ducks raised in an open-house system.

METHODS

One hundred seventy-seven (n = 177) commensal E. coli were examined for their antimicrobial susceptibilities and horizontal resistance transfer. The plasmids were examined by PCR-based plasmid replicon typing (PBRT) and plasmid multi-locus sequence typing (pMLST).

RESULTS

The highest resistance rate was found against ampicillin (AMP, 83.0%) and tetracycline (TET, 81.9%), and most isolates exhibited multidrug resistance (MDR) (86.4%). The R plasmids were conjugally transferred when TET (n = 4), AMP (n = 3), and chloramphenicol (n = 3) were used as a selective pressure. The three isolates transferred resistance genes either in AMP or TET. The blaCTX-M1 gene resided on conjugative plasmids. Five replicon types were identified, of which Inc FrepB was most common in the donors (n = 13, 38.4%) and transconjugants (n = 16, 31.2%). Subtyping F plasmids revealed five distinct replicons combinations, including F47:A-:B- (n = 2), F29:A-:B23 (n = 1), F29:A-:B- (n = 1), F18:A-B:- (n = 1), and F4:A-:B- (n = 1). The chloramphenicol resistance was significantly correlated with the other AMR phenotypes (p < 0.05).

CONCLUSIONS AND RELEVANCE

The meat ducks harbored MDR E. coli and played an important role in the environmental dissemination of AMR bacteria and its determinants. This confirms AMR as a health issue, highlighting the need for routine AMR monitoring and surveillance of meat ducks.

Genomic and proteomic analysis of Salmonella Enteritidis isolated from a patient with foodborne diarrhea

Salmonella is a major cause of foodborne diseases and clinical infections worldwide. This study aimed to investigate the drug resistance, genomic characteristics, and protein expression of foodborne Salmonella in Shanxi Province. We isolated a strain of Salmonella Enteritidis from patient feces and designated it 31A. The drug resistance of 31A against 14 antibiotics was determined using an antimicrobial susceptibility test. Whole-genome sequencing and quantitative proteomic analysis were performed on the 31A strain. Functional annotation of drug resistance genes/proteins and virulence genes/proteins was conducted using various databases, such as VFDB, ARDB, CAZY, COG, KOG, CARD, GO, and KEGG. The focus of this study was understanding the mechanisms related to food poisoning, and the genetic evolution of 31A was analyzed through comparative genomics. The 31A strain belonged to ST11 Salmonella Enteritidis and showed resistance to β-lactam and quinolone antibiotics. The genome of 31A had 70 drug resistance genes, 321 virulence genes, 12 SPIs, and 3 plasmid replicons. Functional annotation of these drug resistance and virulence genes revealed that drug resistance genes were mainly involved in defense mechanisms to confer resistance to antibiotics, while virulence genes were mainly associated with cellular motility. There were extensive interactions among the virulence genes, which included SPI-1, SPI-2, flagella, fimbriae, capsules and so on. The 31A strain had a close relationship with ASM2413794v1 and ASM130523v1, which were also ST11 Salmonella Enteritidis strains from Asia and originated from clinical patients, animals, and food. These results suggested minimal genomic differences among strains from different sources and the potential for interhost transmission. Differential analysis of the virulence and drug resistance-related proteins revealed their involvement in pathways related to human diseases, indicating that these proteins mediated bacterial invasion and infection. The integration of genomic and proteomic information led to the discovery that Salmonella can survive in a strong acid environment through various acid resistance mechanisms after entering the intestine with food and then invade intestinal epithelial cells to exert its effects. In this study, we comprehensively analyzed the drug resistance and virulence characteristics of Salmonella Enteritidis 31A using a combination of genomic and proteomic approaches, focusing on the pathogenic mechanism of Salmonella Enteritidis in food poisoning. We found significant fluctuations in various virulence factors during the survival, invasion, and infection of Salmonella Enteritidis, which collectively contributed to its pathogenicity. These results provide important information for the source tracing, prevention, and treatment of clinical infections caused by Salmonella Enteritidis.

Relating Antimicrobial Resistance and Virulence in Surface-Water E. coli

The role of the environment in the emergence and spread of antimicrobial resistance (AMR) is being increasingly recognized, raising questions about the public health risks associated with environmental AMR. Yet, little is known about pathogenicity among resistant bacteria in environmental systems. Existing studies on the association between AMR and virulence are contradictory, as fitness costs and genetic co-occurrence can be opposing influences. Using Escherichia coli isolated from surface waters in eastern North Carolina, we compared virulence gene prevalence between isolates resistant and susceptible to antibiotics. We also compared the prevalence of isolates from sub-watersheds with or without commercial hog operations (CHOs). Isolates that had previously been evaluated for phenotypic AMR were paired by matching isolates resistant to any tested antibiotic with fully susceptible isolates from the same sample date and site, forming 87 pairs. These 174 isolates were evaluated by conventional PCR for seven virulence genes (bfp, fimH, cnf-1, STa (estA), EAST-1 (astA), eae, and hlyA). One gene, fimH, was found in 93.1% of isolates. Excluding fimH, at least one virulence gene was detected in 24.7% of isolates. Significant negative associations were found between resistance to at least one antibiotic and presence of at least one virulence gene, tetracycline resistance and presence of a virulence gene, resistance and STa presence, and tetracycline resistance and STa presence. No significant associations were found between CHO presence and virulence, though some sub-significant associations merit further study. This work builds our understanding of factors controlling AMR dissemination through the environment and potential health risks.

The Resistance and Virulence Characteristics of Salmonella Enteritidis Strain Isolated from Patients with Food Poisoning Based on the Whole-Genome Sequencing and Quantitative Proteomic Analysis

Objective

This paper explores the drug resistance, genome and proteome expression characteristics of Salmonella from a food poisoning event.

Methods

A multidrug-resistant Salmonella Enteritidis strain, labeled as 27A, was isolated and identified from a food poisoning patient. Antimicrobial susceptibility testing determined the resistance of 27A strain to 14 antibiotics. Then, WGS analysis and comparative genomics analysis were performed on 27A, and the functional annotation of resistance genes, virulence genes were performed based on VFDB, ARDB, COG, CARD, GO, KEGG, and CAZY databases. Meanwhile, based on iTRAQ technology, quantitative proteomic analysis was conducted on 27A to analyze the functions and interactions of differentially expressed proteins related to bacterial resistance and pathogenicity.

Results

Strain 27A belonged to ST11 S. Enteritidis and was resistant to levofloxacin, ciprofloxacin, ampicillin, piperacillin, and ampicillin/sulbactam. There were 33 drug resistance genes, 384 virulence genes and 2 plasmid replicon, IncFIB(S) and IncFII(S), annotated by WGS. Proteomic analysis revealed significant changes in virulence and drug proteins, which were mainly involved in bacterial pathogenicity and metabolic processes. PPI prediction showed the relationship between virulence proteins and T3SS proteins, and PagN cooperated with proteins related to T3SS to jointly mediate the invasion of 27A strain on the human body. Phylogenetic analysis indicated that S. Enteritidis has potential transmission in humans, food, and animals.

Conclusion

This study comprehensively analyzed the drug resistance and virulence phenotypes of S. Enteritidis 27A using genomic and proteomic approaches. These helps reveal the drug resistance and virulence mechanisms of S. Enteritidis, and provides important information for the source tracing and the prevention of related diseases, which lays a foundation for research on food safety, public health monitoring, and the drug resistance and pathogenicity of S. Enteritidis.