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    ABSTRACT: Multi drug resistant Shigellae pose a major threat in control of shigellosis with. Shigella dysenteriae being the most prevalent species at our centre before 1994. A gradual decrease in S. dysenteriae occurred over the years with a corresponding increase in S. flexneri which became the predominant serotype. From May to November 2003, an increase in number of patients admitted with clinical diagnosis of dysentery was noted in comparison to previous years, with a corresponding increase in the isolation of multi drug resistant S. dysenteriae. We report here the re-emergence of multi drug resistant S. dysenteriae at our tertiary care centre in north India after a gap of about 10 yr. Plasmid analysis of S. dysenteriae was also performed to study the origin and clonality of the isolates. Stool samples were collected in Cary-Blair medium and processed by standard methods. Shigellae were confirmed by serotyping. Minimum inhibitory concentration was done by agar dilution method and E-test. Plasmid profiling of 18 isolates (16 S. dysenteriae 1 and 2 S. dysenteriae 2) was performed by modified alkali lysis method. Clinical details of patients were noted. A total of 64 patients with dysentery were admitted during the study period. Patients presented with unusually severe symptoms and six developed complications. Treatment failure with ciprofloxacin occurred in six patients who received cefotaxime and amikacin. There were 38 children below 5 yr of age. S. dysenteriae (18 isolates of S. dysenteriae 1 and 2 isolates of S. dysenteriae 2) were isolated from 20 of the 64 (31.2%) stool samples. S. dysenteriae re-emerged as the commonest isolate after a gap of nearly 10 yr. Fourteen of the 20 S. dysenteriae isolates were multi drug resistant; 12 were resistant to ciprofloxacin with MIC of 8-32 mug/ml. Plasmid profile analysis revealed that 6 of 11 ciprofloxacin resistant S. dysenteriae 1 had similar profiles. Emergence of a clone of ciprofloxacin resistant S. dysenteriae 1 in north India is disturbing as treatment options in our geographic area are limited in view of already existing high drug resistance to nalidixic acid, co-trimoxazole and amoxycillin. A close monitoring of shifts in serogroup distribution and antibiotic resistance is required to guide clinicians for treatment of shigellosis.
    The Indian Journal of Medical Research 10/2005; 122(4):348-54. · 1.66 Impact Factor
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    ABSTRACT: The capture and spread of antibiotic resistance determinants by integrons underlies the rapid evolution of multiple antibiotic resistance among diverse Gram-negative clinical isolates. The association of multiple resistance integrons (MRIs) with mobile DNA elements facilitates their transit across phylogenetic boundaries and augments the potential impact of integrons on bacterial evolution. Recently, ancestral chromosomal versions, the super-integrons (SIs), were found to be genuine components of the genomes of diverse bacterial species. SIs possess evolutionary characteristics and stockpiles of adaptive functions, including cassettes related to antibiotic resistance determinants previously characterized in clinical isolates, which suggest that MRIs and their resistance genes were originally recruited from SIs and their pool of amassed genes. However, the recombination activity of integrons has never been demonstrated in a bacterium other than Escherichia coli. We introduced a naturally occurring MRI (TpR, SulR) on a conjugative plasmid into Vibrio cholerae, a species known to harbour a SI. We show that MRIs can randomly recruit genes directly from the cache of SI cassettes. By applying a selective constraint for the development of antibiotic resistance, we demonstrate bacterial resistance evolution through the recruitment a novel, but phenotypically silent, chloramphenicol acetyltransferase gene from the V. cholerae SI and its precise insertion into the MRI. The resulting resistance profile (CmR, TpR, SulR) could then be disseminated by conjugation to other clinically relevant pathogens at high frequency. These results demonstrate that otherwise phenotypically sensitive strains may still be a genetic source for the evolution of resistance to clinically relevant antibiotics through integron-mediated recombination events.
    Molecular Microbiology 04/2002; 43(6):1657-69. DOI:10.1046/j.1365-2958.2002.02861.x · 5.03 Impact Factor
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    ABSTRACT: Integrons were detected in 59 of 120 (49%) urinary isolates of Enterobacteriaceae by PCR using degenerate primers targeted to conserved regions of class 1, 2, and 3 integrase genes. PCR sequencing analysis of the cassette arrays revealed a predominance of cassettes that confer resistance to the aminoglycosides and trimethoprim.
    Antimicrobial Agents and Chemotherapy 10/2001; 45(9):2658-61. DOI:10.1128/AAC.45.9.2658-2661.2001 · 4.45 Impact Factor