| ObjectiveAeromonas spp. was investigated among patients resenting with acute diarrhoeal disease from June to September 2010 in Zhejiang. We investigated aetiology, species distribution, virulence genes as well as the antimicrobial susceptibility of Aeromonas spp. The aim of all above was to provide update date for the control of this important disease in our region, clinical reasonable usage of antibiotic, and make some recommendations for future research.MethodStool samples were collected from different regions of Zhejiang province, and processed for bacterial, viral, and parasitologic studies. PCR assays for the amplification of haemolysin (hlyA), aerolysin (aerA), cytotoxic enterotoxin (act), heat-labile cytotonic enterotoxin (alt) and heat-stable cytotonic enterotoxin (ast) were performed with the template DNA of the isolates. These five virulence genes are closely associated with diarrhoea. Disc diffusion test was used to study the antimicrobial susceptibility of 20 kinds of antimicrobial agents.Result1. A total of 205 Aeromonas strains were isolated from 2392 diarrhoeal stool specimens with the isolation rate of 8.6% in Zhejiang. Of these 205 isolates, four different species were identified. A. caviae was the most prevalent species, accounting for 46.8% of all isolates, followed by A. veronii bv. sobria (31.2%) and A. hydrophila (21.0%). There were few isolates of A. veronii bv. veronii(1.0%).2. These strains isolated from 199 faecal specimens,6 patients infected with two Aeromonas isolates. Most isolates [152 (74.1%)] were found as the sole isolates from the specimens, while the remainder [41 (20.0%)] had mixed infections with other enteric pathogens.3. Of 205 strains examined, the hlyA, act and alt genes were respectively found in 21.0%,25.4%, and 28.3%. However, only 2.6% of strains had aerA gene, while 1.5% carried ast. The distribution of various virulence genes among Aeromonas species is different. Surprisingly A. caviae, as the predominant species causing diarrhoea, carried the least virulence genes.4. It is possible to observe 11 genotypes defined on the basis of PCR detection of various virulence genes.47.3% isolates had at least one virulence gene. Just 2(1.0%) A. hydrophila strains were positive for all genes. The dominant genotype was hlyA/alt detected in 27 (62.8%) of A. hydrophila, act in 32(48.5%) of A. veronii strains. The number of isolates with no virulence genes was common among the A. caviae.5. Data showed that 13.7%,16.6%,19.5%,45.4%and 56.6% of all strains were susceptible to the antibiotics ampicillin-sulbactam, amoxicillin-clavulanic acid, cefazolin, cefoxitin and tetracycline respectively. Besides, more than 80% of these isolates were susceptible to other antibiotics tested. Aeromonas spp. showed various Conclusion1. In this study we found a high prevalence of Aeromonas found in diarrhoeal patients, in most cases Aeromonas was the sole pathogen isolated, indicating the potential importance of Aeromonas as enteric pathogens in our geographical region.2. Presence of virulence genes showed different characteristics according to species grouping.3. The sensitive rate of most antibiotics to Aeromonas spp. strains was usually high. But efforts should be made to curb the spread of resistant strains all over the country. |
