Prophage Typing of Methicillin Resistant Staphylococcus aureus Isolated from a Tertiary Care Hospital in Tehran, Iran

Abstract

Background: Staphylococcus aureus is a common cause of infections among humans and animals and it is known as a community-acquired and nosocomial pathogen. Most of the isolates contain lysogenic phages which are responsible for production of various virulence factors such as enterotoxins, staphylokinase, β-lysin, lipase, exfoliative toxin A and Pantone-vlaentine leukociden (PVL). All staphylococcus isolates are classified in 6 groups according to their sensitivity to 27 known lysogenic phages. Objectives: This study was performed to detect the presence of bacteriophage types and determine antibiotic resistance pattern of methicillin resistant S. aureus (MRSA) isolates obtained from a tertiary care hospital in Tehran, Iran from 2008 to 2010. Materials and Methods: A total of 968 S. aureus isolates were collected from a tertiary care hospital in Tehran, Iran and identified at the species level by PCR and biochemical tests. Susceptibility to 17 antibiotics was determined. Then oxacillin and vancomycin minimum inhibitory concentration (MIC) of the resistant isolates were determined. Multiplex-PCR was used to detect 6 classes of prophages. Results: Out of the 968 isolates 247 isolates were resistant to methicillin. Highest antibiotic resistance was seen to penicillin (100%), erythromycin (89.8%), kanamycin (89.4%), ciprofloxacin (88.6%) and tobramycin (87.4) respectively. None of the MRSA isolates showed resistance to vancomycin, synercid and linezolid. MIC results indicated that 46.1 and 4.4% of isolates with high (MIC ≥ 128 μg/ml) and low level (MIC ≥ 4 μg/ml) showed resistance to oxacillin, respectively. Four different phage types and eight patterns of prophages were detected. All MRSA isolates contained at least one prophage. Totally, 2.8, 69.2 and 27.9% contained 5, 4 and 3 different prophage types, respectively. Conclusions: High prevalence of different classes of prophages indicating the potential to carry a broad spectrum of virulence factors and high oxacillin resistance were found in the MRSA isolates. Detection of SGF phage in 100% of the isolates indicates the ability of these isolates to produce virulence factors.