Identification and antimicrobial susceptibility of Aeromonas spp. isolated from stool samples of Brazilian subjects with diarrhoea and healthy controls

Isolation and Molecular Identification of Aeromonas Wound Infection in Iranian Burn Patients

INTRODUCTION

Aeromonas have recently emerged as opportunistic pathogens and only a few studies are available regarding the isolation of these bacteria from burn wound infections. This study aimed at isolating Aeromonas as an infrequent cause of infection in this group of immunocompromised patients.

METHODS

A total of 300 samples were collected from the wounds of burn patients hospitalized in Gotbodin Shirazi Burn Center in 2013. The samples were cultured on Aeromonas specific media and then confirmed using standard biochemical tests and 16S rRNA gene amplification and sequencing. The antibiotic susceptibility of the isolates was determined using the disk diffusion and broth microdilution methods.

RESULTS

Biochemical tests demonstrated five presumptive samples of Aeromonas, while, molecular testing confirmed only three. All isolates were resistant to ampicillin-sulbactam, erythromycin, oxacillin, and vancomycin. However, they were susceptible to gentamicin, meropenem, nitrofurantoin, chloramphenicol, cephalexin, and cefotaxime. Two Aeromonas veronii isolates were resistant to sulfamethoxazole-trimethoprim and sensitive to nalidixic acid, while Aeromonas bestiarum was sensitive to the former and resistant to the latter antibiotics. Lastly, only one of the A. veronii isolates was found to be resistant to tetracycline.

CONCLUSION

This study is the first to report on the isolation of Aeromonas spp. from burn patients in Iran. Moreover, this is the first report of isolating A. bestiarum from burn wounds. The results of this study confirm earlier findings that the use of molecular methods is essential to accurately identify these bacteria.

Virulence characteristics and antimicrobial resistance of Aeromonas veronii biovar sobria 312M, a clinical isolate

Aeromonas are bacteria widely distributed in the environment, and some species are able to cause infections in humans, of which diarrhea is the most common. The objective of this study was to evaluate the presence of virulence and antimicrobial resistance associated characteristics in A. veronii biovar sobria strain 312M isolated from diarrheal stools. For this, the genome sequencing and phenotypical tests were performed. The draft genome annotation revealed several complete pathways associated with carbon metabolism and a mucin-desulfating sulfatase which may contribute to intestine colonization, and a large number of virulence-associated genes encoding structures associated with adhesion, toxins, and secretion systems. The strain exhibited swimming and swarming motility, biofilm formation, and hemolytic activity. It was resistant to ampicillin, ampicillin/sulbactam, and amoxicillin-clavulanic acid. Although a cphA gene encoding a narrow-spectrum carbapenase was identified in the strain genome, no carbapenemase activity was detected in the antimicrobial susceptibility test. When compared with other A. veronii with complete genomes, the main differences in virulence characteristics are related to lateral flagella and type III and VI secretion systems; the antimicrobial resistance spectrum also varied among strains. The results indicated that A. veronii biovar sobria 312M presents high virulence potential and resistance to limited classes of antimicrobials.

Antibiotic and heavy metal resistance genes in Aeromonas spp. isolated from marketed Manila Clam (Ruditapes philippinarum) in Korea

AIMS

Manila clam (Ruditapes philippinarum) is one of the most popular seafood in Korea, owing to their unique taste and nutritional value. This study aimed to disclose the antibiotic and heavy metal resistance characteristics of Aeromonas spp. isolated from marketed Manila clam in Korea.

METHODS AND RESULTS

A total of 36 Aeromonas spp. strains were isolated and subjected to two tests: an antibiotic disk diffusion test to determine their resistance to antibiotics, and a broth dilution test to determine their resistance to heavy metals. PCR-based amplification was performed to detect the resistance genes. A high level of resistance to ampicillin (100%) and cephalothin (89%) was observed, while 42, 39, 36 and 36% of the isolates were resistant to oxytetracycline, imipenem, nalidixic acid and tetracycline respectively. In addition, among the tested heavy metals, cadmium (Cd) recorded the highest resistance rate (61%), followed by chromium (Cr) (50%), lead (Pb) (47%) and copper (Cu) (37%). However, mercury (Hg) resistance was not observed. PCRs revealed the occurrence of bla_TEM , bla_SHV , bla_CTX-M , qnrS, tetB, tetE, aac(6')-Ib, strA-strB and intI1 genes among 100, 31, 31, 78, 78, 89, 25, 50 and 72% of the isolates respectively. Moreover, heavy metal resistance genes, copA, merA and czcA were detected in 25, 47 and 61% of the isolates respectively.

CONCLUSIONS

The results suggest the importance of multi-drug and heavy metal-resistant aeromonads in Manila clam to assess the consumer safety and public health.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first to elaborate on the importance of multi-drug and heavy metal-resistant aeromonads in Manila clam. Particularly, the presence of extended-spectrum-β-lactamase genes and other antibiotic resistance genes intensifies the possible health risks and may complicate therapeutic treatments upon infection, while heavy metal resistance suggests possible heavy metal exposure.

Multisite Evaluation of the BD Max Extended Enteric Bacterial Panel for Detection of Yersinia enterocolitica, Enterotoxigenic Escherichia coli, Vibrio, and Plesiomonas shigelloides from Stool Specimens

The purpose of this study was to perform a multisite evaluation to establish the performance characteristics of the BD Max extended enteric bacterial panel (xEBP) assay directly from unpreserved or Cary-Blair-preserved stool specimens for the detection of Yersinia enterocolitica, enterotoxigenic Escherichia coli (ETEC), Vibrio, and Plesiomonas shigelloides The study included prospective, retrospective, and prepared contrived specimens from 6 clinical sites. BD Max xEBP results were compared to the reference method, which included standard culture techniques coupled with alternate PCR and sequencing, except for ETEC, for which the reference method was two alternate PCRs and sequencing. Alternate PCR was also used to confirm the historical results for the retrospective specimens and for discrepant result analysis. A total of 2,410 unformed, deidentified stool specimens were collected. The prevalence in the prospective samples as defined by the reference method was 1.2% ETEC, 0.1% Vibrio, 0% Y. enterocolitica, and 0% P. shigelloides Compared to the reference method, the positive percent agreement (PPA) (95% confidence interval [CI]), negative percent agreement (NPA) (95% CI), and kappa coefficient (95% CI) for the BD Max xEBP assay for all specimens combined were as follows: ETEC, 97.6% (87.4 to 99.6), 99.8% (99.5 to 99.9), and 0.93 (0.87 to 0.99); Vibrio, 100% (96.4 to 100), 99.7% (99.4 to 99.8), and 0.96 (0.93 to 0.99); Y. enterocolitica, 99.0% (94.8 to 99.8), 99.9% (99.8 to 99.9), and 0.99 (0.98 to 1); P. shigelloides, 100% (96.4 to 100), 99.8% (99.5 to 99.9), and 0.98 (0.95 to 1), respectively. In this multicenter study, the BD Max xEBP showed a high correlation (kappa, 0.97; 95% CI, 0.95 to 0.98) with the conventional methods for the detection of ETEC, Vibrio, Y. enterocolitica, and P. shigelloides in stool specimens from patients suspected of acute gastroenteritis, enteritis, or colitis.

Utilization of carbon sources by clinical isolates of Aeromonas

Bacteria in the genus Aeromonas are primarily aquatic organisms; however, some species can cause diseases in humans, ranging from wound infections to septicemia, of which diarrhea is the most common condition. The ability to use a variety of carbon substrates is advantageous for pathogenic bacteria. Therefore, we used Biolog GN2 microplates to analyze the ability of 103 clinical, predominantly diarrheal, isolates of Aeromonas to use various carbon sources, and we verified whether, among the substrates metabolized by these strains, there were some endogenous to the human intestine. The results indicate that Aeromonas present great diversity in the utilization of carbon sources, and that they preferentially use carbohydrates and amino acids as carbon sources. Among the carbon sources metabolized by Aeromonas in vitro, some were found to be components of intestinal mucin, including aspartic acid, glutamic acid, l-serine, galactose, N-acetyl-glucosamine, and glucose, which were used by all strains tested. Additionally, mannose, d-serine, proline, threonine, and N-acetyl-galactosamine were used by several strains. The potential to metabolize substrates endogenous to the intestine may contribute to Aeromonas' capacity to grow in and colonize the intestine. We speculate that this may help explain the ability of Aeromonas to cause diarrhea.

Diarrheagenic pathogens in adults attending a hospital in Singapore

Background

Singapore’s diarrhoeal notification system is based on specific pathogens. Official data may thus be skewed towards notifiable diseases. Limited information is available on the profiles of aetiological agents responsible for acute gastroenteritis (AGE) cases, especially among the adult population. To understand the frequency and distribution of potential causative agents of diarrheal disease in Singapore, we screened adults’ stool samples collected from a large public hospital.

Methods

The stool samples were screened for 18 diarrheagenic pathogens using a combination of commercial multiplex polymerase chain reaction (PCR), in-house singleplex PCR and immunochromatographic assays. One hundred adult faecal samples that were collected from October 2013 to January 2014 for routine diagnostic purposes and submitted for culture at Tan Tock Seng Hospital, Singapore were used.

Results

Pathogens were detected in 32 % of the samples. The predominant organisms encountered were norovirus genogroup II (11 %), Aeromonas spp. (9 %) and Campylobacter spp. (5 %). One sample was positive for both verocytotoxigenic E. coli (VTEC) and E. coli O157:H7. Two other samples were positive for VTEC only, and one other sample was positive for E. coli O157:H7 only. Astrovirus, C. perfringens, Shigella spp. and toxigenic C. difficile were each detected in 2 % of the samples. Cryptosporidium parvum, Giardia lamblia, group A rotavirus, Salmonella spp. and Vibrio spp. were each detected in 1 % of the samples. No L. monocytogenes, Y. enterocolitica, enteric adenovirus, or norovirus genogroup I were detected.

Conclusion

Our preliminary findings suggest that pathogens causing non-notifiable diseases might have contributed considerably to the adult hospitalised AGE cases. However, as the samples were from an adult hospital, the data obtained may not be representative of the whole community. Thus, a larger study to collect clinical samples and risk exposure data from primary healthcare clinics and children hospital is planned for, to gain a more holistic perspective on the epidemiology of AGE in Singapore. A larger study may also offer valuable insights for improving the approach of microbiological surveillance of food, as well as strategizing inspection efforts along the food supply chain by public health authorities.

Draft Genome Sequence of Aeromonas caviae 8LM, Isolated from Stool Culture of a Child with Diarrhea

Aeromonas spp. are Gram-negative rods ubiquitous in aquatic environments; however, some species are able to cause a variety of infections in humans. Here, we report the draft genome sequence of Aeromonas caviae 8LM isolated from stool culture from a child with diarrhea in southern Brazil.

Bacterial enteropathogens and risk factors associated with childhood diarrhea

OBJECTIVE

To investigate the etiology of bacterial enteropathogens causing diarrhea among children; to elucidate the risk factors, sign and symptoms involved in developing of infection; and to identify the antimicrobial susceptibility pattern.

METHODS

Stool samples from diarrheal cases with clinical diagnosis of gastroenteritis compared to matched controls, were examined for detection of bacterial enteropathogens by conventional cultural method from February 2006 through January 2007.

RESULTS

Ninety three of diarrheal cases comprising enteropathogen isolates. A recognized bacterial enteric pathogen was identified in 31% of the cases and 8% of the control group. The frequency of isolated enteropathogens from faeces of diarrheal cases was recorded in the following order, Enterohemorrhagic E. coli 8.3%, Shigella spp. 6.7%, Campylobacter jejuni 5%, Salmonella spp. 4%, Yersinia enterocolitica 2.7%, Aeromonas spp. 4.7%, and Plesiomonas spp. 1.3%. E.H.E coli, Shigella and Salmonella had shown a significant statistical association with diarrhea (p<0.05). Compared to matched uninfected control, multivariate analysis revealed that malnutrition status (OR adjusted 8.37; p<0.001) was the only independent factor associated with infection. Antibiotic susceptibility profile indicated that enteropathogens were generally susceptible to meropenem, ceftriaxone, followed by amikacin and ciprofloxacin. Almost all enteropathogens were resistant to ampicillin and amoxicillin.

CONCLUSIONS

The results of this study emphasize the importance of bacterial enteropathogens in causing severe diarrhea in children. E.H.E. coli was the most predominant pathogen. Malnutrition was identified as the main independent risk factor associated with developing of infection. Ampicillin and amoxicillin should not be used as empirical treatment in acute diarrhea.

Aeromonas spp. clinical microbiology and disease

Members of the genus Aeromonas inhabit various aquatic environments and are responsible for, and are implicated in, a number of intestinal and extra-intestinal infections in humans as well as other animals. This review focuses on invasive human infection and disease and summarizes available findings regarding the microbiology and detection of Aeromonas spp., with emphasis on successful identification and diagnosis, and the control of disease in the population. Antimicrobial resistance and therapy of Aeromonas spp. is also discussed.