Objective: To determine the antibiotic susceptibility patterns of species isolated from water and stool samples in Mthata Region.

Materials and methods: A study was undertaken to determine the presence and susceptibility profiles of Aeromonas species isolated from water and stool samples submitted to Mthata Government hospital from January 2012- October 2012.A total of 500 water samples and 150 stool samples were analysed.

Results: Aeromonas species were found in 30% of the water samples and in 10% of the stool samples. 20% of the isolates from the water samples were β-lactamase positive and 100% of the stool isolates respectively, giving a total of 45 isolates which were ESBL positive. The isolates were susceptible to ciprofloxacin, imipenem and tazobactum and the ESBL strains presented with variable resistance to all the antibiotics and were mostly resistant to β-lactams. Table 1 shows the comparisons of the susceptibility profiles of Aeromonas species from water and stool samples. The results show a similar trend in susceptibility profile of Aeromonas isolated from water and stool samples implicating a likely hood of cross contamination due to contaminated water or the population contaminating the water sources.

Conclusion: There is need for laboratories to expand their screening methods and include routine checking of Aeromonas species in patients with diarrhea. While this research needs to further evaluate the Phylogenetic characteristics of the isolated strains in order to link the sources of contamination.

Keywords: Aeromonas species, kirby bauer disc diffusion method, diarrhea, ESBL, septiceamia, endocarditis, peritonitis, osteomylitis

Aeromonas species are motile gram negative rods of the family Aeromonadaceae. They are emerging human pathogens suspected to cause gastroenteritis ranging from mild enteritis to cholera -like diarrhea, known as travelers diarrhea. Aeromonas species have been reported to cause infections such as septiceamia, endocarditis, peritonitis, osteomylitis, myonecrosis, haemolytic uraemic syndrome, meningitis, respiratory tract diseases and ocular infection.¹ In addition to humans, they are also important pathogens in amphibians, repitiles and fish causing major problems in fish farming. Aeromonas species have also been isolated from a variety of foods such as vegetables, raw milk, icecream, meat and seafood.^2,3 They are known to form biofilms in chlorinated water pipes and this also serves as a source of human contamination. Its pathogenicity is due to the production of exotoxins (heamolysins and enterotoxins). Aeromonas spp are becoming increasingly resistant to multiple antibiotics. Such resistance could lead to serious clinical sequelae. Rate of faecal carriage in asymptomatic persons ranges from 0%-4%, while the isolation rate from individuals with diarrhea ranges from 0.8-7.4%.^1,4 It is commonly isolated from drinking water and seasonal relationship between presence in drinking water and in stools of patients with gastroenteritis have been reported.^5,6

500 Water samples and 150 stool samples were analysed between January -October 2012. Unformed stools submitted to NHLS M that was used.

Microbiological tests

Water samples were first inoculated onto selenite F broth and then inoculated onto blood agar supplemented with Ampicillin and a selective media cefsulodin-irgason-novobiocin agar (CIN). Stool samples were inoculated directly onto CIN and ampicillin blood agar. The cultures were incubated for 24-48hours aerobically at 37˚C. An oxidase test was done on all bacilli colonies and hippurate hydrolysis test was done to differentiate the Aeromonas species. β-lactamase test was done on all isolates using a calorimetric test strip.

Susceptibility testing

Kirby bauer disc diffusion Method was used for susceptibility testing. The following antibiotics were used, Ampicillin, Gentamicin, Ciprofloxacin, Imipenem, Cotrimoxazole, piperacillin/tazobactum, chloramphinicol, ciphalothin and erythromycin. NCCLS 2012 Standards were used.

Aeromonas species were isolated in 30% of the water samples and in 10% of the stool samples. A hydrophilia of the isolates from water samples, 20% were ESBL strains and 100% of the stool isolates respectively. All strains were resistant to Ampicillin but susceptible to Ciprofloxacin, imipenem, piperacillin/tazobactum. Their susceptibility varied on erythromycin, chloramphinicol, gentamicin and ciphalothin as shown in Table 1.

The results were as expected as all the strains were resistant to Ampicillin due to the production of β-lactamases and were sensitive to third -generation Cephalothins and were in accordance to results from findings from other researchers.¹ He justifies the need to include laboratory isolation techniques for Aeromonas species in unformed stool samples and also to screen for species in water sources. More work needs to be done in order to compare the Phylogenetic characteristics of isolates from water and stool samples so that we can be able to link the relationship between environment and human diseases due to Aeromonas in patients presenting with diarrhea/gastroenteritis.

None.

The author declares no conflict of interest.

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