BackgroundCholera, an infectious disease caused by Vibrio cholerae, is a major public health problem and is a particularly burden in developing countries including Nepal. Although the recent worldwide outbreaks of cholera have been due to V. cholerae El Tor, the classical biotypes are still predominant in Nepal. Serogroup O1 of the V. cholerae classical biotype was the primary cause of a cholera outbreak in Kathmandu in 2012. Thus, this study was designed to know serotypes and biotypes of V. cholerae strains causing recent outbreak with reference to drug resistant patterns. Moreover, we also report the toxigenic strains of V. cholerae from both environmental and clinical specimens by detecting the ctx gene.MethodsTwenty four V. cholerae (n = 22 from stool samples and n = 2 from water samples) isolated in this study were subjected to Serotyping and biotyping following the standard protocols as described previously. All of the isolates were tested for antimicrobial susceptibility patterns using the modified Kirby-Bauer disk diffusion method as recommended by CLSI guidelines. The screening of the ctx genes (ctxA2-B gene) were performed by PCR method using a pair of primers; C2F (5′-AGGTGTAAAATTCCTTGACGA-3′) and C2R (5′-TCCTCAGGGTATCCTTCATC-3′) to identify the toxigenic strains of V. cholerae.ResultsAmong twenty four V. cholerae isolates, 91.7% were clinical and 8.3% were from water samples. Higher rate of V. cholerae infection was found among adults of aged group 20–30 years. All isolates were serogroups O1 of the V. cholerae classical biotype and sub serotype, Ogawa. All isolates were resistant to ampicillin, nalidixic acid and cotrimoxazole. 90.9% were resistant to erythromycin however, tetracycline was found to be the most effective drug for the isolates. All isolates were multidrug resistant (MDR) and possessed a ctx gene of approximately 400 base pairs indicating the toxigenic strains.ConclusionHundred percent strains of V. cholerae were MDR possessing a ctx gene. It suggests that toxigenic strains be identified and proper antibiotic susceptibility testing be conducted. This will allow effective empirical therapy to be used to treat and control cholera.

Amylases are starch degrading enzymes which are produced by plants, animals and microorganisms. Amylases produced by microorganisms have a wide range of industrial applications such as in pharmaceutical, food, textile and paper industries. However, there are still limitations in the isolation of amylase producing microorganisms. The objective of this study was to isolate the potent amylase producing Bacillus sp. from soil samples and evaluate their abilities for inhibiting the aflatoxin producing Aspergillus flavus. In this study, 30 soil samples were used. For the screening and identification of Bacillus strain, morphological and biochemical tests were performed. Iodine assay was done to screen the potent amylase producers. Two parameters (pH and temperature) were used to optimize the cultural conditions for the production of amylase. To determine the total reducing sugar, dinitrosalicylic acid (DNS) assay was used. Altogether 29 colonies were selected and identified as Bacillus spp out of which 16 were selected to determine enzyme activity by cup plate method. Four isolates (DK9, DK10, IM4 and KD7) showing highest amylolytic activities (16 mm, 12 mm, 14 mm and 14 mm zone of hydrolysis) were subjected for further study. Isolate KD7 showed the highest amylolytic activity (0.19 U/mL) compared to other isolates. Maximum amylase production was found at pH 6 and temperature 50° C (0.19 U/mL). Among these 4 isolates, DK9 and KD9 showed strong antagonistic activity against Aspergillus flavus while DK10 and IM4 showed moderate antifungal activities. Thus, the bacterial isolate KD7 was identified as the most potent strain for maximum amylase production.