Abstract
Introduction: Methicillin-resistant Staphylococcus aureus
(MRSA) plays an important role in causing many serious nosocomial
infections. In this study, the antimicrobial susceptibility and the
frequency of aminoglycoside modifying enzyme encoding genes among
clinical isolates of methicillin-resistant Staphylococcus aureus was investigated from two university hospitals of Zanjan province of Iran.
Methods:
In this study, the antimicrobial susceptibility of MRSA isolates to
various antibiotics was investigated by the disk diffusion method.
Multiplex PCR assays were used for the determination of aminoglycoside
modifying enzyme (AME) genes and staphylococcal cassette chromosome mec
(SCCmec) types in MRSA strains.
Results:
All 58 MRSA isolates were sensitive to vancomycin. Resistance to
penicillin G, oxacilin, gentamicin, erythromycin, clindamycin,
kanamycin, and tobramycin was found in 96.4%, 98.3%, 51.7%, 53.4%,
55.2%, 62% and 58.6% of the isolates, respectively. The most prevalent
AME genes were aac(6′)/aph(2′′) (48.3 %) followed by ant(4)-Ia (24%).
The aph(3′)-Ia gene was the least frequent AME gene among MRSA isolates
(19%). Of the 58 tested MRSA isolates, 5 (8.6%) were harboured SCCmec
type I, 11 (19%) SCCmec type II, 20 (34.5%) SCCmec type III, 17 (29.3%)
SCCmec type IVa, 1 (1.7%) SCCmec type IVb, 2 (3.4%) SCCmec type IVc, 11
(19%) SCCmec type IVd, and, 18 (31%) SCCmec type V. Nineteen isolates
were not typeable.
Conclusion:
In conclusion, the aac (6′)/aph (2′′) was the most common
aminoglycoside modifying enzyme gene and SCCmec type II and V were the
most frequent types detected in hospital isolates, respectively.