Jundishapur J Microbiol. 2013 November; 6(9): e7686. DOI: 10.5812/jjm.7686 Published online 2013 November 1. Research Article Comparison of Hypervariable Region (HVR) of mecA Gene in Staphylococcus aureus Isolated From Nasal Carriers and Clinical Samples Neda Zeinali Nia 1 , Mohammad Reza Pourmand 1,* , Parviz Afrough 1 1 Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, IR Iran *Corresponding author: Mohammad Reza Pourmand, School of Public Health and Biotechnology Research Center, Tehran University of Medical Sciences, Tehran, IR Iran. Tel: +98- 2188954910, Fax: +98-2188954910, E-mail: mpourmand@tums.ac.ir. Received: August 12, 2012; Revised: October 28, 2012; Accepted: January 12, 2013 Background: Methicillin Resistant Staphylococcus aureus (MRSA) is a common major human pathogen that causes hospital-acquired infections. Characterization and typing of the staphylococcal cassette chromosome has led to a better understanding of MRSA infection cycle in hospital. The mecA-associated hypervariable region size classifies MRSA isolates that colonized in nasal carriers. Objectives: The aim of this study was to compare the genetic background of hypervariable region (HVR) of mecA gene in S. aureus isolated from nasal carriers and clinical samples. Materials and Methods: A cross sectional study was performed on 261 nasal swabs collected from healthy health care workers (HCW) and 109 clinical samples from Tehran university hospitals. All the S. aureus isolates were identified by biochemical tests (Coagulase, Catalase, Manitol fermentation, and DNase tests). S. aureus isolates were investigated for the variability of HVR of mecA gene by PCR method. Results: Among 261 collected nasal swabs, 70 (27%) were S. aureus. Of these, 29(41%) isolates were resistant to Oxacillin and 32 (46%) of those had mec-HVR gene. The polymerase chain reaction (PCR) products showed five different patterns of HVR. Also among 109 clinical samples, 52 (48%) of them were S. aureus. Of these, 40 (77%) were resistant to Oxacillin and 45 (87%) of them carried the mec-HVR gene. The PCR products showed 11 different patterns of HVR. Conclusions: Molecular typing of MRSA isolates by HVR amplification has shown a high diversity among the strains and can be used as a basis for tracking the contaminations and the source of hospital infections from staff to patients and vice versa. Keywords: Staphylococcus aureus; Carrier State; Cross Infection Implication for health policy/practice/research/medical education: Staphylococcus aureus persists in nasal canal of hospital health workers and can be transferred to the hospitalized patients. Determination of nasal colo- nized MRSA and clinical isolates based on mecA gene variation might be useful to investigate the cycle of infections in patients and health care workers. Copyright © 2013, Ahvaz Jundishapur University of Medical Sciences; Published by Kowsar Corp. This is an open-access article distributed under the terms of the Cre- ative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Background Staphylococcus aureus is one of the most frequent hu- man pathogens that produces a wide range of infections (1). The pathogen is resistant to most of common antibi- otics and thus has caused many problems in treatment of diseases. A notable example in this regard is the emer- gence of Methicillin resistant S. aureus (MRSA), which was reported for the first time just one year after the in- troduction of Methicillin to the clinical practice. MRSA is an important hospital pathogen, and is responsible for development of various infections such as skin and soft tissue infections, pneumonia, bacteremia and catheter- related infections (2, 3). Resistance against Methicillin in S. aureus is due to a large mobile genetic element, called Staphylococcus cas- sette chromosome mec (SCCmec). The 20 - 50 kb region of mec DNA contains mecA gene, which encodes modified Penicillin binding protein (PBP2A) with lower affinity to beta-lactam antibiotics (4). The genomic distance of mecA and IS431 (insertion sequence 431) is very variable and is called the hypervariable region (HVR), which is consisted of exact repeated units of the 40 bp length. The variability of the region is due to the high polymorphism observed in isolates of S. aureus (4, 5). The adjunct IS sequences, transposones, and the mec DNA can be considered as the hot spots, which include the antibiotic resistance genes (6). It seems that the staphylococcal carriers play an impor- tant role in pathogenesis of the infections caused by S. aureus. The asymptomatic colonized patients and hospi- tal staff are the main sources of MRSA in hospital environ- ment. Health care workers (HCW) are considered as the link between patients. Screening of the carriers of MRSA is necessary for control of nosocomial infections (7). The risk of carrier colonization with this pathogen and infections in diabetic patients, IV drug abusers, hemodi- alysis and surgical patients, and those with immune sys- tem deficiency are noteworthy. Considering the genetic variation of MRSA and the high rate of mortality of the patients and the high costs of treatment of the infections, the control of these infections should be accompanied with molecular typing methods. An ideal molecular tech- nique should be rapid, easy to perform, and interpret. Moreover, the test should have a reasonable differentia-