Plasmid-Encoded Multidrug Resistance of Salmonella typhi and some Enteric Bacteria in and around Kolkata, India: A Preliminary Study

The present study investigates the occurrence of R-plasmid in Salmonella typhi isolates from enteric fever cases in and around Kolkata (1991-2001), India following in vitro conjugation experiments, isolation of plasmid DNAs and agarose gel electrophoretic analysis. The multidrug resistant (MDR) S. typhi strains contained a transferable plasmid conferring resistance to ampicillin, chloramphenicol, cotrimoxazole and tetracycline. The plasmid encoding ACCoT-resistance of Escherichia coli, Klebsiella pneumoniae and Proteus vulgaris were conjugative and co-migrated with the plasmid of MDR S. typhi isolates. The antibiotic sensitive S. typhi isolates did not contain any plasmid. Thus the findings of the present study confirmed the instability of the R-plasmid in S. typhi, and that the antibiotic sensitive S. typhi strains acquired the R-plasmid from other enteric bacteria such as E. coli, K. pneumoniae and P.vulgaris to undergo a suitable adaptation for survival in the changing antibiotic environment

Enhancing chloramphenicol and trimethoprim in vitro activity by Ocimum sanctum Linn. (Lamiaceae) leaf extract against Salmonella enterica serovar Typhi

AbstractObjectiveTo evaluate the antibacterial activity of Ocimum sanctum (O. sanctum) leaf extract, alone, and in combination with chloramphenicol (C) and trimethoprim (Tm) against Salmonella enterica serovar Typhi (S. typhi).MethodsThe antibacterial activity of ethanolic extract of tulsi, O. sanctum, leaf (TLE; 500 μg) for 23 S. typhi isolates was determined following agar diffusion. The C (30 μg) and Tm (5 μg) activity alone and in combination with TLE (250 μg) was determined by disk diffusion. The zone diameter of inhibition (ZDI) for the agents was recorded, and growth inhibitory indices (GIIs) were calculated.ResultsThe S. typhi isolates (n=23), which were resistant to both C (ZDI 6 mm) and Tm (ZDI 6 mm), had TLE (500 μg) ZDIs 16-24 mm. The ZDIs of C and Tm were increased up to 15-21 mm and 17-23 mm, respectively, when TLE (250 μg) was added to the C and Tm discs. The GIIs ranged 0.789-1.235 and 0.894-1.352, due to combined activity against S. typhi isolates, of C and TLE and Tm and TLE, respectively.ConclusionsThe data suggest that TLE, in combination with C and Tm, had synergistic activity for S. typhi isolates, and hence O. sanctum is potential in combating S. typhi drug resistance, as well promising in the development of non-antibiotic drug for S. typhi infection

Plasmid-Mediated Dimethoate Degradation by Bacillus licheniformis Isolated From a Fresh Water Fish Labeo rohita

The Bacillus licheniformis strain isolated from the intestine of Labeo rohita by an enrichment technique showed capability of utilizing dimethoate as the sole source of carbon. The bacterium rapidly utilized dimethoate beyond 0.6 mg/mL and showed prolific growth in a mineral salts medium containing 0.45 mg/mL dimethoate. The isolated B licheniformis exhibited high level of tolerance of dimethoate (3.5 mg/mL) in nutrient broth, while its cured mutant did not tolerate dimethoate beyond 0.45 mg/mL and it was unable to utilize dimethoate. The wild B licheniformis strain transferred dimethoate degradation property to E coli C600 (Na(r), F(−)) strain. The transconjugant harbored a plasmid of the same molecular size (approximately 54 kb) as that of the donor plasmid; the cured strain was plasmid less. Thus a single plasmid of approximately 54 kb was involved in dimethoate degradation. Genes encoding resistance to antibiotic and heavy metal were also located on the plasmid

Plasmid-Encoded Multidrug Resistance of Salmonella typhi and some Enteric Bacteria in and around Kolkata, India: A Preliminary Study

The present study investigates the occurrence of R-plasmid in Salmonella typhi isolates from enteric fever cases in and around Kolkata (1991-2001), India following in vitro conjugation experiments, isolation of plasmid DNAs and agarose gel electrophoretic analysis. The multidrug resistant (MDR) S. typhi strains contained a transferable plasmid conferring resistance to ampicillin, chloramphenicol, cotrimoxazole and tetracycline. The plasmid encoding ACCoT-resistance of Escherichia coli, Klebsiella pneumoniae and Proteus vulgaris were conjugative and co-migrated with the plasmid of MDR S. typhi isolates. The antibiotic sensitive S. typhi isolates did not contain any plasmid. Thus the findings of the present study confirmed the instability of the R-plasmid in S. typhi, and that the antibiotic sensitive S. typhi strains acquired the R-plasmid from other enteric bacteria such as E. coli, K. pneumoniae and P.vulgaris to undergo a suitable adaptation for survival in the changing antibiotic environment

<i>In vitro </i>efficacy of ciprofloxacin alone and in combination with amoxicillin against <i>Salmonella typhi </i>isolates

360-362Combined effect of cipronoxacin (Ci) and amoxycillin (Ax) has been studied in vitro against 12 clinical isolates of S.typhi  that showed Ci minimum inhibitory concentration (MIC) of ≥1μg/ml. By agar dilution method, MIC values of Ax were 10-16 μg /ml for 11 isolates and 0.5μg/ml for the remaining one isolate. The isolates, when treated with Ci and Ax in combination, showed fractional inhibitory concentration (FIC) of 0.004-0.256 μg /ml for Ci. FIC of Ax ranged from 6- 10 μg /ml, except for a single isolate that showed Ax FIC of 0.25 μg /ml. Thus Ci was more efficacious in combination with Ax against S. typhi than Ci alone. The antibiotic combination exhibited an additive effect for all the isolates showing FIC index 0.504-0.832