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Egypt. J. Exp. Biol. (Bot.). 2013; 9(2): 219-231


MOLECULAR AND MICROBIOLOGICAL STUDIES ON VANCOMYCIN RESISTANT STAPHYLOCOCCUS AUREUS (VRSA) STRAINS ISOLATED FROM BURNED PATIENTS

Wesam A. Hassanein Yehia A. EL-Zawahry Fifi M. Reda Reham A. Abd El-Rahman.


Abstract

The present investigation covered a total of seventy burned patients, 40 from Sidnawy Hospital, Zagazig University, Egypt, and 30 patients from king Fahd Hospital, Al Qassim, Saudi Arabia. The incidence of total microorganisms isolated from swab, blood, urinary and sputum cultures indicated that Gram-positive bacteria were the most predominant microorganisms representing 72 out of 121 total isolates (59. 50%), while 49 isolates were Gram-negative (40.50%). The most common pathogenic bacterial group isolated from patients was Staphylococcus aureus, followed by K. pneumonia and P. aeruginosa, whereas, S. epidermidis and Micrococcus showed the lowest incidence. The antibiotics sensitivity against fifty seven S. aureus isolates indicated high resistance to ampicillin (63.15 %) and methicillin (71.92%), intermediate to amoxicillin, and high susceptibility to imipenem and vancomycin except that, the four isolates no. 12, 30, 50 and 95 were multiresistant .These isolates were resistant to 11 antibiotics which include imipenem and vancomycin . Identification of the four isolates was confirmed molecularly using 16S rDNA gene sequence. The determined minimum inhibitory concentrations (MICs) of vancomycin antibiotic indicated differences in antibiotic resistance among the four tested S. aureus strains. Multiplex PCR amplification of mecA and vanA genes in tested strains, using specific primers revealed that all tested strains were mecA gene negative, while two out of four tested strains had vanA gene. Also the tested VRSA strains were characterized by their production to virulence factors hemolysins, lecithinases and proteases. Out of nine tested essential plant oils, thyme and tea tree oils were the most potent against the tested VRSA strains. Synergetic effects were obtained in combination treatment between vancomycin with thyme oil or tea tree oil (50 %:50%) against VRSAS strains. Furthermore there was a significant decrease in production of protease, hemolysin and lethinase by the tested bacteria after incubation in the presence of 0.3 and 0.6% tea tree oil for 24 h.

Key words: Bacterial infections in burned patients, mecA and vanA genes of Vancomycin resistant S. aureus and Bactericidal effect of essential oils






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