2017, Cilt 47, Sayı 1, Sayfa(lar) 039-046 |
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Investigation of Reduced Vancomycin Susceptibility in Methicillin-Resistant Staphylococcus aureus Strains |
Emine KORKUT TUNÇ, Çiğdem KUZUCU, Barış OTLU |
İnönü Üniversitesi, Turgut Özal Tıp Merkezi, Mikrobiyoloji ve Klinik Mikrobiyoloji Bölümü, Malatya |
Keywords: MRSA, vancomycin, VISA/hVISA |
Objective: Staphylococcus aureus is one of the most
important factors that leads to community-acquıired and
nosocomial infections in the whole world. Vancomycinresistant
S. aureus (VRSA) bacteria can be detected in
routine sensitivity tests because they have very high
minimal inhibitory concentration values aganist
vancomycin. Vancomycin-intermediate S. aureus (VISA)/
heterogenous VISA (hVISA) bacterial strains can not be
detected using routine sensitivity tests applied in
laboratories. In our study we aimed to search the frecuency
of VISA and hVISA strains isolated from various samples
sent to our hospital microbiology laboratory between
January 2008-August 2013. Fifty-two MRSA bacteriel
strains.samples isolated and stocked in microbiology
laboratory of our hospital at -80°C were used to investigate
the freguency of VISA and hVISA isolates.
Materials and Methods: These samples were first subjected to
molecular tests by multipleks polymerase chain reaction
(PCR) method for detecting mecA, nuc and 16S genes.
Vancomycin microdilution, gradient test, vancomycin screen
agar (BHIA-V6) were applied on these samples. Macrogradient
test and PAP-AUC method were runned on nine bacterial
strains which were reproduced in screen agar.
Results: mecA gene zone was displayed in 52 bacterial
strains by PCR. All bacterial strains are found to be
sensitive to vancomycin (MIK≤2 μg/ml) by using gradient
test and broth microdilution method. Bacterial growth was
observed within the first 24 (n=8), and 48 hours (n=1) in
indicated number of samples in brain heart infusion
(BHIV6) agar screen test which contained 6 μg/ml
vancomycin. In macrogradient test MIK values were found
to be ≥8 μg/ml in 5 strains, and ≤8 μg/ml in four bacterial
strains Nine bacterial strains (17.3%) were evaluated to be
hVISA according to the population analysis profile results.
Conclusion: According to these results we found that
MRSA strains which have decreased sensitivity aganist
vancomycin also present in our hospital. These bacterial
strains can not be detected with routine laboratory tests.
These bacterial strains should be identified to prevent
unsuccesful treatment because nowadays glycopeptide
antibiotics are the first choice in the treatment of MRSA.
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