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GENETIC ANALYSIS OF MULTI DRUG RESISTANT STRAINS OF SALMONELLA TYPHI ISOLATED IN KARACHI, PAKISTAN

Farooqui, Bader Jehan (1994) GENETIC ANALYSIS OF MULTI DRUG RESISTANT STRAINS OF SALMONELLA TYPHI ISOLATED IN KARACHI, PAKISTAN. PhD thesis, University of Karachi, Karachi.

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Abstract

Over a period of seven years (1986-1992) 2,935 S. typhi were isolated from blood cultures collected from patients suspected of typhoid fever. During this study period S. typhi was observed to circulate in each month of every year, with the number of isolates increasing each year. MDR S. typhi causing typhoid fever has existed in Karachi since July 1986. The frequency of isolation, however, of MDR S. typhi causing typhoid fever has increased over a period of seven years. This increase is statistically significant when the numbers of MDR S. typhi isolated in 1992 are compared with those in 1986. There was a sharp increase in the frequency of isolation of MDR S. typhi in the year 1987, but the total number of resistant isolates were less than in 1992 Our results show that MDR S. typhi responsible for typhoid fever are still sensitive to cefotaxime, ceftriaxone, aztreonam and ofloxacin with a narrow range of MICs. Acridine orange and ethidium bromide failed to cure the antimicrobial resistance markers of MDR S. typhi. These MDR S. typhi isolates appear to share a single plasmid (named pBN1) of 20 Kb which confers resistance to chloramphenicol, ampicillin and trimethoprim sulfamethoxazole. Plasmid of all these MDR S. typhi when treated with EcoRl produced single band indicating that these plasmids have no restriction sites for EcoRl. These results confirm that the plasmid pBNl is responsible for the resistance to all the three antimicrobial drugs. The results also confirm that plasmid pBNl is conjugative in nature. The results have demonstrated that E. coli HB10l was successfully transformed with plasmid pBN1. Transformed E. coli HB10l showed same antimicrobial resistance pattern and MICs as donor cells. Transconjugants and transformed E. coli carried same resistance markers as that of the donor cells. Plasmid of transconjugants and transformed E. coli when treated with EcoRl produced single band indicating that these plasmids have no restriction sites for EcoRl. To conclude it is perhaps a single plasmid which is responsible for the cause of resistance in all the strains of S. typhi.

Item Type:Thesis (PhD)
Uncontrolled Keywords:salmonella typhi, genetic analysis, typhoid fever, cefotaxime, ceftriaxone, aztreonam, ofloxacin, plasmid pbnl
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Evolution & genetics (c1.6)
ID Code:1173
Deposited By:Mr. Muhammad Asif
Deposited On:03 Jan 2007
Last Modified:04 Oct 2007 21:04

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