CHARACTERIZATION OF DETERMINANT FOR TRANSFERABLE ANTIMICROBIAL DRUG RESISTANCE AND VIRULENCE ASSOCIATED FACTORS OF S. GALLINARUM
Loading...
Date
1999
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
AAU, Anand
Abstract
In the present study characterization of antimicrobial drug resistance and its transferable nature in S. gallinarum isolates was carried out. Further curing of R-determinants and the effect of curing on virulence on virulence associated factros viz., colicinogeny and serum resistance was ascertained. Virulence of isolates were assayed by lethality and invasiveness assay and attempts were also made to isolate plasmid from S. gallinarum isolates. In vitro antimicrobial drug resistance against 10 commonly used antibiotics were detected. All the S. gallinarum isolates showed resistance against one or more drug tested. All the isolates were resistant to sulfamethoxazole while higher number of isolates showed resistance to nalidixic acid, gentamicin and enrofloxacin. Moderate number of isolates showed resistance against furazolidone, streptomycin, tetracycline and cotrimoxazole while resistance against pefloxacin was shown by lesser number of isolates. Least resistance isolates were observed for chloramphenicol. In vitro transfer of drug resistance was also studied. Out of 12 S. gallinarum isolates tested all (100 per cent) were found to transfer resistance against tetracycline, nine (75 per cent) isolates transferred en bloc resistance against tetracycline, gentamicin and sulfamethoxazole while three (25 per cent) isolates transferred resistance against only tetracyc1ine. In vivo transfer of drug resistance was carried out from two donor strains of S. gallinarum to recipient E. coli strain. Out of two S. gallinarum strains tested both revealed transfer of drug resistance from donor to recipient. Total 20 (57.1 per cent) isolates out of 35 isolates tested were found to produce bacteriocin. Twelve isolates were tested for transfer of colicinogeny, out of which six (56 per cent) were able to transfer of colicinogeny to recipient E. coli strain along with multiple drug resistance. Elimination of drug resistance (curing) markers in six strains of S. gallinarum were studied using different chemical and physical method. The chemical agents used for curing were ethidium bromide (EtBr) and novobiocin (Novo) ethidium bromide and novobiocin combination and sodium dodecyl sulfate (SDS). In present study the elimination of drug resistance by chemical agents observed frequently. Use of EtBr and SDS resulted in curing of drug resistance in all six strains while five and four strains were cured by EtBr and Novo combination and novobiocin alone respectively. In physical method of curing, 3 out of six S. gallinarum strains were eliminated drug resistance on 1 day of incubation at 45°C and higher number of curing frequencies, was observed on subsequent days. Thus resistance markers were more readily eliminated by incubation at 45°C for prolonged periods of time rather than by chemical agents. Resistance of six strains of S. gallinarum wild and their cured derivatives to bactericidal effect of chicken serum was studied. The study revealed that all the wild and cured strains tested were resistant to chicken serum. To know the role of virulence associated factors like colicinogeny and serum resistance, virulence assay of six selected wild and their cured derivatives was carried out by determining their lethality as well as invasiveness ability in day old chicks. In lethality assay wild strains (S-21, S-4 and S-27) caused mortality 66.66, 60.00 and 46.66 per cent respectively, while their cured derivatives caused mortality of 46.66, 20.00 and 20.00 per cent respectively. At the 15th day post infection (PI) surviving birds revealed infection as per the CFU count method. In invasiveness assay there was no significant difference in the CFU count among S. gallinarum wild. isolates and their cured derivatives was observed upto 12 day CFU count, but by the 16th day none of the chicks survived in wild strains. Thus it indicates that wild strains were more invasive and lethal as compared to their cured derivatives. All the surviving birds in cured group revealed infection at 16th PI. There was no apparent difference found between lesions of wild and the cured derivatives during virulence assay. Isolation of plasmids from 10 wild and their eight cured derivatives of S. gallinarum were carried out. Majority of the strains showed a plasmid of molecular weight 56 Md. In addition other small plasmids found were of 2.8 Md and 1.79 Md molecular weight.
Description
Keywords
VETERINARY MICROBIOLOGY, CHARACTERIZATION