Prevalence of Aeromonas spp. Infection in Pediatric Patients Hospitalized with Gastroenteritis in Latvia between 2020 and 2021

The Hanks-like serine/threonine protein kinase YihE is crucial for Aeromonas veronii virulence and adhesion

Aeromonas veronii is an important pathogen found in various aquatic environments and products, posing a threat to public health. The Hanks-like serine/threonine protein kinase is closely linked to the pathogenesis of pathogenic bacteria, but the exact role of YihE in A. veronii remains still unknown. To study the specific function of the YihE kinase, we constructed a knockout mutant of the yihE gene in A. veronii. The deletion of the yihE gene resulted in changes to the metabolism of L-arginine-AMC and acetic acid, as well as enhanced resistance to ampicillin and kanamycin in A. veronii. Additionally, the ΔyihE strain demonstrated a 1.4-fold increase in biofilm formation ability and a 1.8-fold decrease in adhesion and invasion to EPCs when compared to the wild-type strain. A significant decrease in cytotoxicity was observed at 2 and 3 h post-infection with EPCs compared to the wild-type strain. Additionally, the deletion of the yihE gene was associated with a significant decrease in motility of the strain. Furthermore, the deletion of the yihE gene resulted in a 1.44-fold increase in the LD50 of A. veronii in zebrafish. These findings offer valuable insights into the pathogenic mechanisms of A. veronii.

Phenotypic and genotypic analysis of antimicrobial resistance and population structure of gastroenteritis-related Aeromonas isolates

BACKGROUND

The population structure and the correlation between antimicrobial resistance (AMR) phenotypes and genotypes in Aeromonas species isolated from patients with gastroenteritis are not well understood. The aims of the study were to: (1) investigate the antimicrobial susceptibility profiles of Aeromonas species isolated from patients with gastroenteritis; (2) explore the relationship between AMR genes and resistance phenotypes; and (3) describe the population structure of these isolates and provide evidence of transmission events among them.

METHODS

This microbiological survey was performed at the Microbiology Laboratory of the Emek Medical Center in Afula, Israel. Cultivation of Aeromonas was attempted from stool samples that tested positive by PCR. Antimicrobial susceptibility testing (AST) was performed using the Sensititre GN3F microdilution panel. Whole genome sequencing (WGS) was done using the Illumina NextSeq500/550 system. Phylogenetic studies involved multi-locus sequence typing (MLST) and core genome (cg) MLST. Resistance mechanisms were identified using the Comprehensive Antibiotic Resistance Database and compared with the AST results.

RESULTS

The study included 67 patient-unique isolates. The species that were identified included A. caviae (n = 58), A. dhakensis (n = 3), A. media (n = 2), A. veronii (n = 2) and A. hydrophila (n = 2). Isolates were almost uniformly susceptible to amikacin, gentamicin, aztreonam, cefepime, ceftazidime, ciprofloxacin and meropenem. All isolates with the exception of 1-2 isolates were resistant to ampicillin, cefazolin and ampicillin-sulbactam which was compatible with the presence of the blaOXA genes. Variable resistance rates were observed to cefuroxime, cefoxitin, ceftriaxone, piperacillin-tazobactam that were not correlated with the presence of other β-lactamase genes. Resistance to tetracycline and trimethoprim-sulfamethoxazole correlated with the presence of tetA and sul1, respectively. The population structure of A. caviae was highly diverse with the minority of the isolates (16/57) clustering into six defined sequence types. A cgMLST-based distance of four genes was found in one pair of isolates, suggesting common source transmission.

CONCLUSIONS

A. caviae is the dominant species related to gastroenteritis and is characterized by a diverse population structure, with almost no evidence for common-source transmission. Resistance rates to most antimicrobial agents were low and partially matched with the presence of resistance genes.

Cross-sectional analysis of risk factors associated with Mugil cephalus in retail fish markets concerning methicillin-resistant Staphylococcus aureus and Aeromonas hydrophila

Introduction

Aeromonas hydrophila and methicillin-resistant Staphylococcus aureus (MRSA) are potent bacterial pathogens posing major hazards to human health via consuming fish harboring these pathogens or by cross-contamination beyond the contaminated environment. The aim of this study was to determine risk variables associated with the presence of certain pathogenic bacteria from Mugil cephalus fish in retail markets in Egypt. The virulence genes of A. hydrophila and S. aureus were also studied. Furthermore, the antibiotic sensitivity and multidrug resistance of the microorganisms were evaluated.

Methods

In a cross-sectional investigation, 370 samples were collected from mullet skin and muscle samples, washing water, fish handlers, knives, and chopping boards. Furthermore, fish handlers' public health implications were assessed via their response to a descriptive questionnaire.

Results

S. aureus and Aeromonas species dominated the investigated samples with percentages of 26.76% and 30.81%, respectively. Furthermore, A. hydrophila and MRSA were the predominant recovered bacterial pathogens among washing water and knives (53.85% and 46.66%, respectively). The virulence markers aerA and hlyA were found in 90.7% and 46.5% of A. hydrophila isolates, respectively. Moreover, the virulence genes nuc and mec were prevalent in 80% and 60% of S. aureus isolates, respectively. Antimicrobial susceptibility results revealed that all A. hydrophila isolates were resistant to amoxicillin and all MRSA isolates were resistant to amoxicillin and ampicillin. Remarkably, multiple drug resistance (MDR) patterns were detected in high proportions in A. hydrophila (88.37%) and MRSA (100%) isolates. The prevalence of Aeromonas spp. and S. aureus had a positive significant correlation with the frequency of handwashing and use of sanitizer in cleaning of instruments. MRSA showed the highest significant prevalence rate in the oldest age category.

Conclusion

The pathogenic bacteria recovered in this study were virulent and had a significant correlation with risk factors associated with improper fish handling. Furthermore, a high frequency of MDR was detected in these pathogenic bacteria, posing a significant risk to food safety and public health.

Enteric Aeromonas Infection: a Common Enteric Bacterial Infection with a Novel Infection Pattern Detected in an Australian Population with Gastroenteritis

Aeromonas species are emerging human enteric pathogens. However, they are currently not routinely detected in many diagnostic laboratories, and information regarding Aeromonas enteric infections detected using molecular methods is lacking. Here, we investigated the detection of Aeromonas species and four other enteric bacterial pathogens in 341,330 fecal samples from patients with gastroenteritis processed in a large Australian diagnostic laboratory between 2015 and 2019. These enteric pathogens were detected using quantitative real-time PCR (qPCR) methods. Furthermore, we compared the qPCR cycle threshold (CT) values obtained from fecal samples that tested positive for Aeromonas only by molecular detection with those of samples that tested positive by both molecular detection and bacterial isolation methods. Aeromonas species were found to be the second most common bacterial enteric pathogens among patients with gastroenteritis. We observed a unique pattern of three infection peaks for Aeromonas, which correlated with the age of the patients. Aeromonas species were the most common enteric bacterial pathogens in children younger than 18 months. Fecal samples that tested positive for Aeromonas only by molecular detection had significantly higher CT values than fecal samples that tested positive by both molecular detection and bacterial culture. In conclusion, our findings reveal that Aeromonas enteric pathogens exhibit an age-related three-peak infection pattern, distinguishing them from other enteric bacterial pathogens. Moreover, the high rate of Aeromonas enteric infection discovered in this study suggests that Aeromonas species should be routinely tested in diagnostic laboratories. Our data also show that combining qPCR with bacterial culture can enhance the detection of enteric pathogens. IMPORTANCE Aeromonas species are emerging human enteric pathogens. However, these species are currently not routinely detected in many diagnostic laboratories, and no studies have reported the detection of Aeromonas enteric infection using molecular methods. We investigated the presence of Aeromonas species and four other enteric bacterial pathogens in 341,330 fecal samples from patients with gastroenteritis using quantitative real-time PCR (qPCR) methods. Interestingly, we discovered that Aeromonas species were the second most common bacterial enteric pathogens in patients with gastroenteritis, exhibiting a novel infection pattern compared to those of other enteric pathogens. Furthermore, we found that Aeromonas species were the most prevalent enteric bacterial pathogens in children aged 6 to 18 months. Our data also revealed that qPCR methods exhibit higher sensitivity in detecting enteric pathogens compared to that of bacterial culture alone. Moreover, combining qPCR with bacterial culture enhances the detection of enteric pathogens. These findings emphasize the importance of Aeromonas species in public health.