International Journal of Current Microbiology and Applied Sciences (IJCMAS)
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Original Research Articles                      Volume : 6, Issue:12, December, 2017

PRINT ISSN : 2319-7692
Online ISSN : 2319-7706
Issues : 12 per year
Publisher : Excellent Publishers
Email : /
Editor-in-chief: Dr.M.Prakash
Index Copernicus ICV 2018: 95.39
NAAS RATING 2020: 5.38

Int.J.Curr.Microbiol.App.Sci.2017.6(12): 3606-3619

Vancomycin-Resistant MRSA Induced by β-Lactam Antibiotics in Mansoura University Hospitals, Egypt
Ahmed E.S. Taha*, Mohammad F. Badr, Fikry E.S. El-Morsy and Enas Hammad
Medical Microbiology and Immunology Department, Faculty of Medicine, Mansoura University, Egypt
*Corresponding author

A major problem in MRSA-infected patients is the co-infection with Gram-negative bacteria which are naturally resistant to Vancomycin (VA) and linezolide (LZD). In the past; the use of a combination of VA and ß-lactam antibiotics was one of the solutions for treating of such condition depending on synergism. In the recent years; a class of MRSA that becomes resistant to VA only in the presence of ß-lactam antibiotics (BIVR) has been emerged meaning that there is antagonism. This type of VA resistance is mainly due to stimulation of peptidoglycan metabolism and repair system, by ß-lactams, so rapidly depleting free VA to a level below its MIC. This means that ß-lactams should remain intact in BIVR culture, although most MRSA cells are known to produce ß-lactamase, meaning that the BIVRs either did not carry the ß-lactamase gene (blaZ) or this gene was suppressed. The present study aimed for screening for the tendency of VA sensitive MRSA to become VA resistant when exposed to β-lactams in vitro; as a result, MRSA possessing the capability to become BIVR in vivo can expected. Also, investigating the relation between the ×´ BIVR phenomenon×´ and the ß-lactamase activity. We studied 130 MRSA isolates, identified by the disc diffusion method and MecA gene amplification PCR. The isolates were selected to be VA susceptible with MIC ≤2 μg/mL. The isolates were subjected to the BIVR screening test, testing the ß-lactamase activity and conducting PCR amplification of blaZ gene. BIVR testing of the MRSA strains revealed that 13.8% of the MRSA strains were BIVR positive while 86.2 % were BIVR negative. All the BIVRs showed an undetectable ß-lactamase activity by nitrocefin test, most of them (83.3%) lacked the blaZ gene and the remaining (16.7%) carried the blaZ gene but showed an undetectable ß-lactamase either by nitrocefin test or spectro photometrically, indicating that this gene was down regulated or suppressed in them by certain mechanism. Most (94.6%) non-BIVRs carried the blaZ gene and most of them (79.2%) actively produced detectable ß-lactamase by nitrocefin test. BIVRs gain vancomycin resistance only in presence of ß-lactam antibiotics, so preserving ß-lactams in milieu, by preventing ß-lactamase production, either by lacking or suppressing the blaZ gene.

Keywords: Antibiotic resistance, ß-lactamase, ß-lactams, MRSA, Staphylococcus aureus, Vancomycin.

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How to cite this article:

Ahmed, E.S. Taha, Mohammad F. Badr, Fikry E.S. El-Morsy and Enas Hammad. 2017. Vancomycin-Resistant MRSA Induced by β-Lactam Antibiotics in Mansoura University Hospitals.Int.J.Curr.Microbiol.App.Sci. 6(12): 3606-3619. doi:
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