Vibrio cholerae, Staphylococcus aureus and bacterial pathogenesis

Vibrio cholerae a human pathogen is primarily an inhabitant of the aquatic environment, and water plays a major role in transmission and epidemiology of cholera. Molecular epidemiologic studies showed clonal diversity among O1 and O139 strains and continuous emergence of new epidemic clones, reflected by changes in the structure, organization and location of the CTX prophase in the V. cholerae chromosome including SXT element encoding respectively for streptomycin, trimethoprim and sulfamethoxazole. Ecological studies have also demonstrated the presence of critical virulence genes in diverse environmental stains of V. cholerae. Our primary focus is to understand evolutionary mechanism and processes involved in the emergence of pathogenic V. choleare, SXT-related ICE and to characterize those pathogenic genes and their protein products that are expressed during various stages of infectious process/ preservation. For this, we will employ a number of molecular biology techniques. We are also interested to study pathogenic factors elaborated during infection, regulatory proteins that coordinate pathogenic events, host stimuli that effects expression of these genes. Our laboratory is also involved in purification and characterization of secretogenic toxin produced by candidate cholera vaccine strains/ non-cholera-producing V. cholerae strains.

Eye infections caused by Staphylococcus species includes angular blepharitis, hordeolum, chalazia, conjunctivitis, phlyctenulosis, ulcerative keratitis, endophthalmitis, preseptal and orbital cellulitis, and dacryocystitis. Staphylococci are the most common organisms isolated from ocular infections. Our primary aim is to determine the antibiotic susceptibility, virulence factors and genotypes of different species of Staphylococcus causing ocular infections and to characterize methicillin sensitive and resistant Staphylococcus species employing molecular biology techniques.

Selected Publications:

1. Mantri CK, Mohapatra SS, Colwell RR, Singh DV. Sequence analysis of Vibrio cholerae orfU and zot from pre-CTXΦ and CTXΦ reveals multiple origin of pre-CTXΦ and CTXΦ. Environmental Microbiology Reports 2010;2(1):67-75.
2. Mohapatra Harapriya, Mohapatra SS, Mantri CK, Colwell, RR, Singh DV. Vibrio cholerae non-O1, non-O139 strains isolated before 1992 from Varanasi, India are multiple drug resistant, contain intSXT, dfr18 and aadA5 genes. Environmental Microbiology 2008; 10(4):866-873
3. Mantri CK, Mohapatra SS, Ramamurthy T, Ghosh R, Colwell RR, Singh DV. Septaplex PCR assay for rapid identification of Vibrio cholerae including detection of virulence and intSXT genes. FEMS Microbiology Letters 2006; 265(2): 208-214.
4. Bhanumathi R, Isac SR, Shukla BN, Singh DV. Molecular characterization of Vibrio cholerae O139 Bengal isolated from water and aquatic plant Eichhornia crassipes in the River Ganga, Varanasi, India. Applied and Environmental Microbiology 2003; 69 (4): 2389-2394.
5. Singh DV, Isac SR, Colwell RR. Development of a hexaplex PCR assay for rapid detection of virulence and regulatory genes in Vibrio cholerae and V. mimicus. Journal of Clinical Microbiology 2002; 40 (11): 4321-4324.
6. Singh DV, Matte MH, Matte GR, Ziang S, Sabeena F, Shukla BN, Sanyal SC, Huq A, Colwell RR. Molecular analysis of Vibrio cholerae O1, O139, non-O1, and non-O139 strains: clonal relationships between clinical and environmental isolates. Applied and Environmental Microbiology 2001; 67(2): 910-921.
7. Singh DV, Sanyal SC. Enteropathogenicity of Aeromonas jandaei and A. trota. FEMS Immunology and Medical Microbiology 1997; 17: 243-250.
8. Singh DV, Tikoo Anjali, Sanyal SC. Candidate live oral cholera vaccine strains produce a new cholera toxin. Current Science 1996; 70: 237-238.
9. Shukla BN, Singh DV, Sanyal SC. Attachment of non-culturable toxigenic Vibrio cholerae O1 and non-O1 and Aeromonas spp. to the aquatic arthropod Gerris spinolae and plants in the River Ganga, Varanasi. FEMS Immunology and Medical Microbiology 1995; 12: 113-120.
10. Singh DV, Sanyal SC. Enterotoxicity of clinical and environmental isolates of Aeromonas spp. Journal of Medical Microbiology 1992; 36: 269-272.