मेडिकल माइक्रोबायोलॉजी और निदान

Prevalence and Antimicrobial Susceptibility of Vancomycin Resistant Staphylococci in an Egyptian University Hospital

Abstract

Tarek El-Said El-Banna, Fatma Ibrahim Sonbo, Ahmed Ahmed Abd El-Aziz and Engy El-Ekhnawy

Staphylococci can cause many nosocomial and community acquired infections with high rates of morbidity and mortality. The large scale of spread of resistance to vancomycin and other antibiotics has been perceived as a fearsome threat to the already challenging therapy of Staphylococci. A total of 982 clinical samples were obtained from different departments of Tanta university hospital. Microscopical examination and standard biochemical tests revealed that 437 isolates were Staphylococci.

Resistance to vancomycin was determined using disk diffusion and agar dilution methods which revealed that 89 were vancomycin resistant Staphylococci (VRS). The susceptibility of VRS isolates to 15 different antimicrobial agents was performed using agar dilution method. All VRS isolates were multidrug resistant (MDR).

Polymerase chain reaction (PCR) studies were performed on selected Staphylococci isolates with different vancomycin MICs ranging from 2 to 512 μg/ml for detection of vancomycin resistance genes (van genes). The vanA gene was detected in VRS isolates only with vancomycin MICs from 32 to 512 μg/ml. Neither vanB nor vanC gene was detected.

β-Lactamase production by VRS isolates was investigated. A total of 88.7% of isolates produced β-lactamase enzyme. Disk approximation test was performed on all VRS isolates that were resistant to erythromycin and sensitive to clindamycin. Out of the 29 isolates on which the test was performed, 24 (82.8%) tested positive. Ciprofloxacin resistant VRS isolates were selected to study the presence of efflux mechanism of resistance. All the tested isolates were efflux positive.

The VRS isolates in hospitals as well as in community are alarming to the clinicians and multi drug resistance in these isolates is very dangerous. In this study we tried to investigate the prevalence of VRS isolates in Tanta and to determine their antibiotic susceptibility.