Abstract:
The objective of the present study was to detect methicillin and vancomycin resistance in
Staphylococcus aureus (S. aureus ) isolated from clinical specimens in Khartoum State.
A total of 219 of S. aureus isolates were collected from microbiology laboratory of
Khartoum Teaching Hospital and microbiology laboratory of Military Hospital. The
isolates were confirmed as S. aureus by phenotypic tests including Gram's stain and other
biochemical tests. Modified Kirbry-Bauer disk diffusion method and brain heart
vancomycin screen agar were used to detect methicillin and vancomycin resistance
strains. Then E-test was applied to confirm vancomycin resistance. DNA was extracted
from MRSA and VISA isolates using Muraflux kit. PCR was then performed to amplify
mecA, vanA and vanB genes.
Out of 219 S. aureus isolates, 155(70.7%) were found to be methicillin resistant (MRSA),
sixteen were vancomycin intermediate (VISA), five strains of them with MIC 8μg/ml and
nine strains with MIC 6μg/ml and two strains showed vancomycin MIC of 4μg/ml and
thirteen strains of them had shown growth on Brain Heart Infusion (BHI) vancomycin
screen agar (vancomycin 6 μg/ml).
Molecular characterization with PCR revealed that among total (155) isolates of MRSA
only 137(88.4%) possess mecA gene. However, none of VISA strains demonstrated the
presence of vanA and vanB genes.
In conclusion molecular characterization, confirmed the existence of methicillin
resistance gene among S. aureus isolates, but this finding failed to prove the occurrence
of van genes-mediated resistance among VISA isolates. Further studies are required to
validate this result.
