Egyptian Journal of Medical Microbiology, October 2007 Vol. 16, No 4 731 Nosocomial Infection in Surgery Wards of Sohag University Hospital Sanaa M.I. Zaki 1 , Medhat Ismail 2 , Hydi Ahmed 2 , Hamdy Hussain 3 , Yaser M. Ismail 4 Departments of 1 Microbiology and Immunology, Faculty of Medicine, Ain Shams University, 2 Clinical Pathology, 3 Surgery, and 4 Orthopedics, Faculty of Medicine, Sohag University ABSTRACT Objective: A prospective study aimed at isolation, biochemical identification and determination of the antibiotic resistance pattern of the bacteriologic agents causing surgical site infection in surgical wards in Sohag University hospital and confirmation of isolated MRSA by detection of mecA gene by PCR assay. Patients And Methods: This study included 100 patients suffering from nosocomial SSI and recruited from different surgical wards in Sohag University hospital in the period from October 2005 to July 2006. SSI was identified using CDC definitions. The collected samples were cultured, the isolated organisms identified, tested for their antibiotic sensitivity and mecA gene detected in the isolated MRSA strains by PCR assay. Results: Gram-negative bacteria were involved in 62 (70.5%) and Gram-positive cocci in 26 (29.5%). Five species were isolated most frequently: Staphylococcus aureus (20), Escherichia coli (20), Pseudomonas aeruginosa (16), Proteus mirabilis (12) and Klebsiella pneumoniae (11). Resistance to most commonly available antibiotics was moderate to very high among Gram-positive and Gram-negative isolates. Almost all Gram-negative bacteria were sensitive to imipenem and amikacin. PCR assay revealed that all the isolated Staphylococcus aureus strains (100%) were positive for mecA gene. Conclusion: It is of utmost importance to estimate the frequency of surgical site infections and identify associated risk factors in order to undertake adequate measures for their prevention and control. INTRODUCTION Nosocomial infection or “hospital acquired infection” can be defined as an infection acquired in hospital by a patient who was admitted for a reason other than that infection (1). It also can be defined as an infection that occurs in a patient, in a hospital or other health care facility in whom the infection was not present or incubating at the time of admission. This includes infections acquired in the hospital but appearing after discharge, and also occupational infections among staff of the facility(2). Nosocomial infections have been recognized for over a century as a critical problem affecting the quality of health care and a principal source of adverse health care outcomes. Nowadays, nosocomial infections account for 50% of all major complications of hospitalization; the remainder are due to medication errors, patient falls and other non-infectious adverse events (3). Nosocomial infection constitutes a major problem globally, with major social, economical, moral and personal effects that increases the morbidity and mortality of hospitalized patients especially in intensive care units (ICUs) (4, 5). The important risk factors for acquisition of infection are invasive procedures, which include operative surgery, intravascular and urinary catheterization and mechanical ventilation of the respiratory tract (6). The most frequent nosocomial infections are infections of surgical wounds, urinary tract infections and lower respiratory tract infections. The incidence of surgical site infections varies from 0.5 to 15% depending on the type of operation and underlying patient status (7). Surgical site infection is a significant problem which limits the potential benefits of surgical interventions. The impact on hospital costs and postoperative length of stay (between 3 and 20 additional days) is considerable (8). According to data from the NNIS system, the distribution of pathogens isolated from SSIs has not changed markedly during the last decade (9). Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus spp., and Escherichia coli remain the most frequently isolated pathogens. An increasing proportion of SSI is caused by antimicrobial-resistant pathogens, such as methicillin-resistant S. aureus (MRSA) (10) or by Candida albicans (11). From 1991 to 1995, the incidence of fungal SSIs among patients at NNIS hospitals increased from 0.1 to 0.3 per 1,000 discharges (11). Methicillin resistance in S. aureus is caused by the acquisition of an exogenous gene, mecA, that encodes an additional β-lactam-resistant penicillin-binding protein (PBP), termed PBP 2a (or PBP2`) (12). The mecA gene is carried by a mobile genetic element, designated staphylococcal cassette chromosome mec (SCCmec), inserted near the chromosomal origin of replication (13). SCCmec is characterized by the presence of terminal inverted and direct repeats, a set of site- specific recombinase genes (ccrA and ccrB), and the mec gene complex (14). The SCCmec DNAs are integrated at a specific site (attBscc) in the methicillin-susceptible S. aureus (MSSA) chromosome which is located at the 3` end of an