Plasmid Analysis and Prevalence of Multidrug Resistant Staphylococcus aureus Reservoirs in Chennai City, India
S Jayaraman, M Manoharan, S Illanchezian, R Sekher, P Sathyamurthi
mar, mrsa, plasmid dna, prevalence, staphylococcus aureus
S Jayaraman, M Manoharan, S Illanchezian, R Sekher, P Sathyamurthi. Plasmid Analysis and Prevalence of Multidrug Resistant Staphylococcus aureus Reservoirs in Chennai City, India. The Internet Journal of Microbiology. 2008 Volume 7 Number 1.
The present study was designed to investigate the prevalence of multidrug resistant
Antimicrobial resistance has been noticed as one of the paramount microbial threats of the twenty first century (Smolinski et al., 2003).
The present study reports the prevalence, antimicrobial resistance and the plasmid profile of
Materials and Methods
A total of 40 clinical samples comprising of 20 urine and 20 serum samples, collected during a period of three months between December 2007 and February 2008 from healthy individuals of both sex (male & female) in Chennai city were screened for the presence of
All the samples were collected in sterile containers & processed aseptically. All the samples were examined individually for the existence of
The isolated strains were identified to their species level by Gram staining and standard biochemical tests such as catalase, urease, oxidase, citrate utilization, indole, methyl red and Voges Proskauer test. Identification of isolates was confirmed by direct-tube coagulase test with plasma.
The haemolytic activity of the
Antibiotic susceptibility testing
The antibiotic susceptibility of the
Multiple Antibiotic Resistance (MAR) index value of all the strains were calculated. The MAR index applied to a single isolate is defined as a / b, where 'a' represents the number of antibiotics to which the isolate was resistant and 'b' represents the number of antibiotics to which the isolate was subjected (Krumperman, 1985).
Plasmid DNA Isolation
All the isolates were subjected to plasmid DNA extraction by alkali lysis method as described by Bimboim, 1983. The extracted plasmid DNA was electrophoresed on 1.2% agarose gel stained with ethidium bromide. About 20 µL of plasmid DNA preparation were loaded into each well and electrophoresed at 50 volts for 1 hr. Plasmid DNA band was observed with UV transilluminator and photographed. Molecular weight of the DNA bands was calculated by comparing with Lambda DNA
Among the 40 samples analyzed, 57.5 % (23/40) of the samples were positive for fermentation of Mannitol Salt Agar. All the isolates were identified as Gram positive cocci in clusters under microscopic examination. The isolates were positive for methyl red, Voges Proskauer, catalase, and coagulase test. The biochemical characteristics of the isolates from clinical samples are indicated in Table 1. All the isolates showed -haemolytic pattern on blood agar.
The antibiotic resistance data of
All the isolates were multiple antibiotic resistant. The MAR index value ranged between 0.18 and 0.63. Notably, 39.13% of isolates were resistant to 4 / 11 (MAR index – 0.36) antibiotics tested. Among the isolates, 21.73% and 17.39 % of them were resistant to 3 / 11 (MAR index – 0.27) and 5 / 11 (MAR index – 0.45) antibiotics tested respectively.
Plasmid DNA analysis
The plasmid DNA analysis of the isolates showed the presence of one plasmid in all the isolates. A 23 kb plasmid DNA was observed in all the isolates when compared with the Lambda DNA
This study is the first report on the prevalence of multiple antibiotic resistant
Higher prevalence of
All the isolates were resistant against amoxicillin, methicillin, bacitracin and novobiocin. The isolates showed least antibiotic resistance against other antibiotics tested. Onanuga et al. (2005) reported 16 % and 89 % of the isolates from healthy woman were resistant to gentamicin and vancomycin respectively which is in contrary to the present study. Only one isolate from serum sample showed resistance to vancomycin. Rajaduraipandi et al. (2006) and Anbumani et al. (2006) reported none of the isolates were resistant to vancomycin. This variation in the drug resistance may be well related to the type of antimicrobial agents prescribed for treating various diseases in different geographical areas (Radu et al., 1997).
The MAR index value ranges between 0.18 and 0.63. All the isolates showed resistance to atleast 2 of 11 antibiotics tested. The incidence of
Several workers have reported the multiple antibiotic resistance patterns of
The plasmid analysis of the isolates revealed the presence of 23kb plasmid in all the isolates. Resistance in MRSA is also related to a chromosomal mecA gene that specifies the production of an abnormal penicillin binding protein called PBP2a. Multiple drug resistance of
The results of the present study are in agreement to the postulation that healthy members are the highest reservoir of multidrug resistant bacteria (Lamikanra et al., 1996). However, this study involves only a small number of isolates. So, a multi centre study should be well planned and done to determine the prevalence of multidrug resistant
We thank Life Teck Research Centre, Chennai for providing us the facilities and requisite support for completion of this work. We express our thanks to clinical laboratories which provided clinical samples for this study.