Egypt J. Med. Lab. Sci., April. 2008; 17(1):35-43 ISSN 1110-5593 METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS AS A NOSOCOMIAL PATHOGEN IN BURN WOUND INFECTION Original Nehal I. Draz, Mahmoud K. Elsayed1, and Hazem M. Aly2 Article 1Microbiology, immunology. and 2Plastic surgery departments, Faculty of medicine, Ain Shams University ABSTRACT Background: Methicillin resistant staphylococcus aureus (MRSA) is important as a nosocomial pathogen and MRSA colonization in the burn unit may lead to increased transmission of MRSA to non burn patients in other wards. Aim of the Work: was to determine the prevalence of MRSA among patients with burn wound infection in the Burn Unit in Ain Shams University Hospitals. Patients and Methods: The study involved fifty patients with infected burn wounds divided into two groups as twenty five outpatients and twenty five inpatients in the Burn Unit of Ain Shams University Hospital. Swabs were taken aseptically from infected wounds for bacteriological examination. Results: The most common bacterial isolate among outpatients group was S. aureus (44%), followed by Ps. aeurginosa (40%), coagulase negative Staphylococci (12%), Proteus mirabilis (4%) and Citrobacter freundii (8%). While in the inpatients group, Ps. Aeruginosa topped the list infecting 36% of patients, followed by S. aureus (24%), coagulase negative Staphylococci (16%), Klebsiella pneumoniae (12%), E.coli (12%), Proteus mirabilis (8%) and S. pyogenes (4%). Concerning MRSA, it was isolated from 20% of the inpatients, accounting for 83% of all isolated S.aureus and emerged as a significant nosocomial pathogen as it was not recovered from any outpatient. Conclusion: MRSA is a significant nosocomial pathogen in the Burn unit of Ain Shams University Hospital. Continuous surveillance of burn wound infection and developing strategies for antimicro- bial resistance control is recommended. Key Words: Nosocomial, MRSA, Burn, Staphylococci. Corresponding Author: Dr. Nehal Draz, Microbiology Department, Faculty of medicine, Ain Shams University, Cairo, Egypt, Mobile: 0105055598, e-mail: [email protected] INTRODUCTION Burn injury is a major public health prob- Methicillin resistant Staphylococcus aureus lem in many areas of the world. Burn wound (MRSA) was first reported in the United infection is one of the most common causes Kingdome soon after clinical introduction of death and serious problems after thermal of methicillin, a beta-lactamase resistant injury (Mason, et al. 1986). Burns predispose antibiotic. Its resistance to methicillin confers to infection by damaging the protective barrier cross-resistance to other broad spectrum beta function of the skin, thus facilitating the entry of lactam antibiotics including cephalosporins pathogenic microorganisms and by inducing (Prasanna and Thomas, 1998). The concern systemic immunosuppression (Rastegar Lari, about MRSA infection in "burns-units" et al. 1998). In spite of considerable advances has been increasing since the late 1980s in the treatment of burns, infection continues (Heggers, et al. 1988 ; Matsumura, et al. 1996). to pose the greatest danger to burn patients. Approximately 73 per cent of all death within MRSA is important as a nosocomial in- the first five days post-burn have been shown fection and MRSA colonization in the burn to be directly or indirectly caused by sep- unit may lead to increased transmission of tic processes (Ekrami and Kalantar, 2007). MRSA to non burn patients in other wards 35 METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS ... (Matsumura, et al. 1996 ; Ekrami and Ka- Statistical analysis was performed by lantar, 2007). The aim of this study was to using statistical software package (SPSS) determine the prevalence of MRSA among version10. Descriptive data of patients and patients with burn wound infection in the controls were expressed as mean ± SD, range Burn Unit in Ain Shams University Hospitals. and frequency. Analytic data by comparison between two independent mean samples was PATIENTS AND METHODS done using the Student "t" test. Quantitative data were compared by Pearson Chi-square This study was conducted from September test. P < 0.05 was considered significant. 2003 till March 2004 in the Burn Unit of Ain Shams University Hospitals. Fifty burn RESULTS patients with symptoms and signs indicative of wound infection were included in this Fifty patients (30 males and 20 females) study. They were divided into two groups: suffering from burn wound infection were in- cluded in this study. The most common cause Group A: Twenty five outpatients (19 males of burn was flame burn (27/50- 54%), followed and 6 females) with age ranging between 11 by scald burn (20/50-40%) and only 3 cases months-67 years (mean 21.5±20.34) with had flash burn (6%). Out of the50 patients; TBSA ranging between 1-10% (mean 4.2±2.8). 22 had burn of the second degree (64%), 7 had third degree (14%) and 11 (22%) had Group B: Twenty five inpatients (11 males both second and third degree burn. They and 14 females) with age ranging between 8 were divided into two groups; twenty five months–72 years (mean 28.8±20.4) with TBSA outpatients and twenty five inpatients in the ranging between 10-90% (mean 30.9±18.9). Burn unit of Ain Shams University Hospitals. After all patients’ consent, swabs were As shown in table (1), the commonest taken from burn wounds at the 3rd day post isolate among inpatients was Ps. aerugino- burn. Swabs were cultured immediately sa (36%) followed by S.aureus (24%).The on nutrient agar, blood agar and Mac commonest isolate among outpatients was Conkey’s agar plates at 370C for 18-24 hours S.aureus (44%) followed by Ps. aeruginosa aerobically. Organisms were isolated and (40%). The isolation rate of S. aureus among identified according to standard methods studied cases was (34%). MRSA was iso- described by Collee and Marr (1996). lated from 5 out of the 25 inpatients (20%). Disk diffusion test was performed for all Table (2) shows that the commonest Staph.aureus isolates by the method recom- cause of burn among inpatients was flame mended by Clinical and Laboratory Standard burn (72%) while the commonest cause Institute (CLST). A suspension of each isolate of burn among outpatients was scald burn was made so that the turbidity was equal to (60%). The commonest bacterial isolates 0.5 McFarland standard and then plated onto were G-ve bacilli in flame as well as in Muller-Hinton agar (Difcos) plate. Oxacillin scald burned patients. No mixed infection disk (Oxoid) was applied to each plate. After was detected among flash burned patients. incubation at 350C for 24 hours, inhibition zone size was measured. Interpretation of the re- Table (3) and Fig.(1) show that MRSA sults was performed by comparing the size of emerges among in patients only as inhibition zone with that presented in NCCLS it represented 83% of the S.aureus (2003). Zones of inhibition around oxacillin strains isolated from them, while all disks were examined carefully for evidence of the isolated S.aureus strains from of growth inside the zone (Boyce, 1998). outpatients were sensitive to methicillin. 36 DRAZ et al. Non significant difference was detected As shown in table (5), there was no specific between incidence of MRSA infection and age significantly associated with MRSA the etiology of burn, MRSA emerged among infection. scald burn as well as flame burned patients accounting for 40% and 60% of S.aureus Table (6) indicates that the risk of developing isolated, respectively, while it was not de- MRSA infection increases significantly as tected among flash burned patients (table 4). total burn surface area (TBSA) increases. Table 1: Incidence of different organisms causing burn wound infection Inpatient Outpatient Total Isolated organisms No. % No. % No. % Ps. Aeruginosa 6 24 6 24 12 24 Klebsiella 28--2 4 E. coli 28--2 4 G-ve bacilli Prot. Mirabilis 28143 6 Citrobacter frundii 28284 8 Erwinia herbicola --1412 S. aureus* 2* 8 7 28 9 18 G. +ve cocci Coagulase –ve Staph 28312510 Coagulase (-ve) Staphylococci + P. G+ve cocci + aeruginosa 28143 6 G-ve bacilli S. pyogenes + Citrobacter 14--1 2 S. aureus* + p. aeruginosa 1431248 S. aureus* + Citrobacter 14--1 2 S. aureus + S. aureus* + Klebsiella 14--1 2 G-ve bacilli S. aureus + E. coli 14--1 2 S. aureus + Enterobacter --1412 Total 25 100 25 100 50 100 X2 = 14.6 P value > 0.05 = N. sig. *= MRSA ( 20% of burn wound infection in hospitalized patients was caused by MRSA as it was isolated from 5 out of the 25) 37 METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS ... Table 2: Correlation between burn etiology and different bacterial isolates causing burn wound infection Cause G-ve bacilli +G S. aureus + S. aureus G+ve cocci G-ve baccilli Total of burn +ve cocci G-ve bacilli .No % .No % .No % .No % .No % .No % Scald 1 50 1 50 - - 2 50 1 25 5 20 Flame 1 50 - - 12 92.3 2 50 3 75 18 72 Inpatient No = 25 Flash - - 1 50 1 7.7 - - - - 2 8 G-ve bacilli +G S. aureus + S. aureus G+ve cocci G-ve baccilli Total Cause +ve cocci G-ve bacilli of burn .No % .No % .No % .No % .No % .No % Scald 3 42.9 2 66.7 6 60 1 100 3 75 15 60 Flame 3 42.9 1 33.3 4 40 - - 1 25 9 36 Outpatient No = 25 Flash 1 14.3 - - - - - - - - 1 4 X2 = 14 P. value > 0.05 (NS), X2 = 3.9 P. value > 0.05 (NS) Table 3: Incidence of MRSA among isolated S. aureus. Suspcetibility of S. Inpatient Outpatient Total aureus to methicillin No. % No. % No. % Sensitive 1 17 11 100 12 70.6 MRSA 5 83 - - 5 29.4 Total 6 100 11 100 17 100 X2 = 14 P. value < 0.05 (Sig.) Fig. 1 : Incidence of MRSA among isolated S.aureus.