Pathogenic potential of Aeromonas hydrophila isolated from surface waters in Kolkata, India

Department of Biochemistry, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India.
Journal of Medical Microbiology (Impact Factor: 2.25). 09/2009; 58(Pt 12):1549-58. DOI: 10.1099/jmm.0.014316-0
Source: PubMed


Members of the genus Aeromonas (family Aeromonadaceae) are medically important, Gram-negative, rod-shaped micro-organisms and are ubiquitous in aquatic environments. Aeromonas species are increasingly recognized as enteric pathogens; they possess several virulence factors associated with human disease, and represent a serious public health concern. In the present study, putative virulence traits of Aeromonas hydrophila isolates collected from different natural surface waters of Kolkata, India, were compared with a group of clinical isolates from the same geographical area using tissue culture and PCR assays. Enteropathogenic potential was investigated in the mouse model. Of the 21 environmental isolates tested, the majority showed cytotoxicity to HeLa cells (81 %), haemolysin production (71 %) and serum resistance properties (90 %), and they all exhibited multi-drug resistance. Some of the isolates induced fluid accumulation (FA ratio>or=100), damage to the gut and an inflammatory reaction in the mouse intestine; these effects were comparable to those of clinical strains of A. hydrophila and toxigenic Vibrio cholerae. Interestingly, two of the isolates evoked a cell vacuolation effect in HeLa cells, and were also able to induce FA. These findings demonstrate the presence of potentially pathogenic and multi-drug-resistant A. hydrophila in the surface waters, thereby indicating a significant risk to public health. Continuous monitoring of surface waters is important to identify potential water-borne pathogens and to reduce the health risk caused by the genus Aeromonas.

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    • "The prevalence of motile aeromonads in the freshwater ecosystem indicates their role in causing epizootics (Bhowmik et al. 2009). A. hydrophila was found to be associated with several outbreaks in different parts of the world as well as in the Indian subcontinent. "
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    ABSTRACT: High incidence of mortality in carps was noticed in a polyculture fish farm situated in Orissa, India during March 2009 accounting for cumulative mortality of nearly 2% per day. The infected fish revealed gross ulcerative lesions on skin with erosion of scales and fin-and tail-rot. Acute tubular and diffused interstitial necrosis was observed in kidney tissue along with increased melanomacrophage reactions on histopathological examination. Hepatic and muscular necrosis was also noticed in most of the fish examined. The bacteria isolated from kidney, liver and blood samples were identified as Aeromonas hydrophila after biochemical characterization. This isolate was found to possess aerolysin, lipase, extracellular haemolysin and β-haemolysin genes contributing to its virulence. It was found sensitive to antibiotics amikacin, aztreonam, ceftazidime, ceftazidime, cefuroxime, cephotaxime, ciprofloxacin, co-trimoxazole, gentamicin, levofloxacin, nalidixic acid, netillin, nitrofurantoin, ofloxacin, streptomycin, tetracycline, tobramycin and trimethoprim. Experimental infection of Labeo rohita with this isolate resulted in similar clinical signs as those of collected from the farm. The LD50 dose was calculated to be 1.15 × 10 6 CFU/fish. This study suggests that A. hydrophila still remains an important bacterial pathogen from aquaculture point of view and regular examination of cultured fish is required to resist unexpected loss.
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    • "Various studies have been published on the incidence of antibiotic resistance in environmental bacterial isolates in the Hooghly river, Kolkata City. However, these studies basically concentrated on its incidence in bacteria of fecal origin or those resistant to heavy metals [5] [6] However, no studies were reported on the effects of seasonal variation on antibiotic resistance patterns in this region. Therefore, the primary objective of the work was to isolate, identify and assess the level of antibiotic-resistance in bacteria isolated from the surface waters of Hooghly River in Kolkata and also to monitor the effect of seasonal variation on the pattern of antibiotic resistance. "
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    ABSTRACT: Microbial resistance to antibiotics has now become a major public health issue. Various studies have been published on the incidence of antibiotic resistance in environmental bacterial isolates in the Hooghly river, Kolkata City. No studies were reported on the effects of seasonal variation on antibiotic resistance patterns in this region. Therefore, the objective of this study was to examine antibiotic resistance among bacterial isolates from river Hooghly in different seasons. Bacterial resistance patterns in two seasons - post monsoon (September 2012) and winter (January 2013) have been evaluated. Surface water samples were collected from nine sampling stations in Kolkata and a total of 90 Gram negative bacterial pathogens [44 and 46 from 1st and 2nd sampling respectively] were isolated. Antibiotic resistance pattern was determined by subjecting each isolate to 12 antibiotic discs. Depending on the zone of inhibition, isolates were characterized as resistant, sensitive and intermediate. Bacterial isolates that were resistant to three or more antibiotics are considered to be multiple antibiotic resistant (MAR) bacteria. In post monsoon (n=44) and winter (n=46) sampling, 30 (68.18%) and 31 (67.39%) isolates were found to be MAR. Highest resistance was observed against furazolidone (FR-50) in both samplings. However highest sensitivity was witnessed against the primitive antibiotics tetracycline (TE-30) and chloramphenicol (C-30). Antibiotic resistance index (ARI) values for all nine sampling stations were found to be greater than the threshold 0.2 value indicating greater exposure to antibiotics. However, a remarkable difference was observed in the resistance to individual antibiotics in both samplings. Resistance to 7 antibiotics was observed to be greater in post monsoon as compared to winter sampling. These results ascertain that seasonal variation may have an effect on antibiotic resistance patterns.
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