Colonization of Methicillin Resistant Staphylococcus Aureus Among Nursing Staff at a Tertiary Care Hospital

OBJECTIVES: Nosocomial outbreaks of Methicillin Resistant Staphylococcus Aureus (MRSA) have become a major infection control problem. This cross sectional study was undertaken to investigate the prevalence of MRSA among nursing staff, the association between risk factors and colonization and to determine the antibiotic susceptibility pattern of the isolates. METHODS: Hundred Nursing staff from a Tertiary Care Hospital were included in the study, nasal swab and hand swabs were collected. RESULTS: Out of 100 , 21 individuals were found to be carriers of MRSA. The highest prevalence of MRSA carriage was found in NICU (35.7%). MRSA showed resistance to commonly used antibiotics like, Penicillin (48%), Erythromycin (76%), Clindamycin (76%), Ciprofloxacin (48%). CONCLUSION: The observed prevalence of MRSA colonization among Nursing Staff exceeds previously reported prevalence and showed more resistance to the commonly used antibiotics. INTRODUCTION: Staphylococcus aureus (S.aureus) has been recognized as an epidemiologically important pathogen. Despite antibiotic therapy, staphylococcal infections occur more frequently in hospitalized patients and have severe consequences ranging from benign, superficial skin eruptions to life-threatening infections with bacteraemia , endocarditis , pneumonia and toxic shock syndrome (1). Methicillin was introduced to treat these infections, but in 1961, S.aureus isolates that had acquired resistance to methicillin (methiciliin-resistant S.aureus) were reported (1). In recent years, nosocomial outbreaks of Methicillin Resistant Staphylococcus Aureus (MRSA) have become a major infection control problem. Although, MRSA strains have not been shown to be more virulent than S.aureus, very high mortality rates have been reported from several centres (2). Initially MRSA was limited to hospitals; however it is now increasingly recovered from nursing homes and the community. The emergence of MRSA which is also often multidrug-resistant renders the treatment of staphylococcal infections more challenging (1). Healthcare Workers (HCWs) constitute an important reservoir for S.aureus. Several studies have reported that the rate of nasal carriage of S.aureus among HCWs ranges from 16.8% to 56.1%. Transient colonization has been documented up to 50% among the HCWs. Colonized employees are generally asymptomatic, although they are a potential reservoir of infections acquired by patients. Colonized or infected personnel may serve as a reservoir and disseminator of MRSA in hospitals (2). The present study was undertaken to investigate the colonization and prevalence of MRSA among HCWs from clinical departments and to determine the antibiotic susceptibility pattern of the recovered isolates. MATERIAL AND METHODS: The cross-sectional study was carried out in the Department of Microbiology at a Tertiary Care Hospital, NKP-SIMS & RC, an 840 bedded hospital for two months as a part of Short term Studentship Research Program of the Institute. Samples were collected from 100 HCWs from anterior nares and dorsum of the hand. Any person with upper respiratory tract infection, current skin infections, currently on mupirocin or any other nasal medications, history of nasal bleed or signs of rhinitis and/or using antibiotics in the past 2 weeks were not included in the study. History regarding risk factors like nasal prick, history of previous hospitalization was taken from each participant. Samples were collected from each participant by twice rotating a sterile cotton swab pre-matted with sterile saline in the vestibule of both the anterior nares and from the dorsum of the hand. The collected samples were inoculated on the Robertson cooked meat medium containing 10% NaCl immediately and then transported to the Microbiology Laboratory. Subcultures were done after overnight incubation on Blood Agar and Mannitol Salt Agar. Staphylococcus Aureus was identified by colony morphology, Gram stain, Catalase Test, Slide Coagulase Test, Tube Coagulase Test and Mannitol Fermentation Test. Each isolate was screened for Methicillin resistance by cefoxitin disc diffusion method using 30μg cefoxitin disks (CLSI 2006). The Antimicrobial Susceptibility Test was performed according to the standardized disc diffusion method as recommended by CLSI guidelines (2006) by Modified Kirby Bauer Method. Statistical analysis was done by Epi info version 3.4.3. RESULTS: A total of 200 samples were taken from 100 Healthcare Workers. From these samples 100 were nasal swabs and 100 were swabs from hands. Nasal screening identified 53 S.aureus carriers. Of these 53 nasal carriers of S.aureus, 16 carried MRSA. Hand screening identified 33 S.aureus carriers, of these 33 hand carriers of S.aureus, 9 carried MRSA. Total 21 individuals were found to be carriers of MRSA (Table 1). Table 1: Distribution of Nursing Staff according to MRSA SITE MRSA (n) MRSA (%) Only Hands Carriage 5 5% Only Nasal Carriage 12 12% Both Hands and Nasal Carriage 4 4%


INTRODUCTION:
Staphylococcus aureus (S.aureus) has been recognized as an epidemiologically important pathogen. Despite antibiotic therapy, staphylococcal infections occur more frequently in hospitalized patients and have severe consequences ranging from benign, superficial skin eruptions to life-threatening infections with bacteraemia , endocarditis , pneumonia and toxic shock syndrome (1).
Methicillin was introduced to treat these infections, but in 1961, S.aureus isolates that had acquired resistance to methicillin (methiciliin-resistant S.aureus) were reported (1). In recent years, nosocomial outbreaks of Methicillin Resistant Staphylococcus Aureus (MRSA) have become a major infection control problem. Although, MRSA strains have not been shown to be more virulent than S.aureus, very high mortality rates have been reported from several centres (2). Initially MRSA was limited to hospitals; however it is now increasingly recovered from nursing homes and the community. The emergence of MRSA which is also often multidrug-resistant renders the treatment of staphylococcal infections more challenging (1).
Healthcare Workers (HCWs) constitute an important reservoir for S.aureus. Several studies have reported that the rate of nasal carriage of S.aureus among HCWs ranges from 16.8% to 56.1%. Transient colonization has been documented up to 50% among the HCWs. Colonized employees are generally asymptomatic, although they are a potential reservoir of infections acquired by patients. Colonized or infected personnel may serve as a reservoir and disseminator of MRSA in hospitals (2).
The present study was undertaken to investigate the colonization and prevalence of MRSA among HCWs from clinical departments and to determine the antibiotic susceptibility pattern of the recovered isolates.

MATERIAL AND METHODS:
The cross-sectional study was carried out in the Department of Microbiology at a Tertiary Care Hospital, NKP-SIMS & RC, an 840 bedded hospital for two months as a part of Short term Studentship Research Program of the Institute. Samples were collected from 100 HCWs from anterior nares and dorsum of the hand. Any person with upper respiratory tract infection, current skin infections, currently on mupirocin or any other nasal medications, history of nasal bleed or signs of rhinitis and/or using antibiotics in the past 2 weeks were not included in the study.
History regarding risk factors like nasal prick, history of previous hospitalization was taken from each participant. Samples were collected from each participant by twice rotating a sterile cotton swab pre-matted with sterile saline in the vestibule of both the anterior nares and from the dorsum of the hand. The collected samples were inoculated on the Robertson cooked meat medium containing 10% NaCl immediately and then transported to the Microbiology Laboratory. Subcultures were done after overnight incubation on Blood Agar and Mannitol Salt Agar. Staphylococcus Aureus was identified by colony morphology, Gram stain, Catalase Test, Slide Coagulase Test, Tube Coagulase Test and Mannitol Fermentation Test. Each isolate was screened for Methicillin resistance by cefoxitin disc diffusion method using 30µg cefoxitin disks (CLSI 2006). The Antimicrobial Susceptibility Test was performed according to the standardized disc diffusion method as recommended by CLSI guidelines (2006)

RESULTS:
A total of 200 samples were taken from 100 Healthcare Workers. From these samples 100 were nasal swabs and 100 were swabs from hands. Nasal screening identified 53 S.aureus carriers. Of these 53 nasal carriers of S.aureus, 16 carried MRSA. Hand screening identified 33 S.aureus carriers, of these 33 hand carriers of S.aureus, 9 carried MRSA. Total 21 individuals were found to be carriers of MRSA (Table 1).  The highest prevalence of hand and nasal carriage of MRSA was in NICU (35.7%) which was followed by Dialysis unit (25%), Gynecology OT (21.4%), Orthopedics ward and Surgery OT with 20% each.
No significant association between the risk factors like previous hospitalization, nasal prick and MRSA carriage was found. Regarding carriage rate in relation to age, MRSA carriage rate was found to be higher in young individuals less than 30 years of age (25%) than those aged 30-50 years (19.6%) and above 50 years (0%). Figure 1 shows the in-vitro antibiotic sensitivity pattern of 25 isolates of methicillin-resistant S.aureus is shown below. Resistance to commonly used oral antibiotics Penicillin (48%), Erythromycin (76%), Clindamycin (76%), Ciprofloxacin (48%) and Gentamycin (28%) was noted in MRSA isolates. All isolates were sensitive to Vancomycin.

DISCUSSION:
The prevalence of nasal carriage of MRSA among HCWs at our Hospital has not been determined to date. It is necessary to detect the MRSA carriers among the apparently healthy hospital personnel, particularly those working in the critical care areas. These individuals act as a potential source of infection to their patients, resulting in their extended stay in the hospital (6).
The largest population of S.aureus is found in the regions of the skin and mucous membranes surrounding the openings of the body surface. These include anterior nares, inguinal and perineal areas.
In this study we found the nasal carriage of S.aureus to be 43% and that of MRSA 16% (12% only nasal carriage and 4% both hand and nasal carriage). Hand carriage among HCWs was found to be 9% (5% only hand carriage and 4% both hands and nasal carriage). In our study, the total carriage rate of MRSA was found to be 21%. Our figure is 21% which is high as compared to other studies. The prevalence of MRSA varies between institutions and geographic areas and from the previous studies an increase in the carrier rate is reported in the recent studies. The differences in the design of the study such as the sample size and the method of MRSA detection may account for the disparity in the carriage rate.
Multidrug resistance is a common feature of MRSA (13,14). In our study, 47.6% of the MRSA isolates were resistant to multiple drugs.
It is important to assess the prevalence of MRSA among the HCWs and to follow guidelines for preventive measures to reduce the hospital infections. There is a need for a greater awareness among the health professionals regarding the standard precautionary measures which are aimed at the prevention of acquisition of pathogens, especially when considering multi-drug resistance and the potential for the transmission of nosocomial infections from the HCWs who are colonized by MRSA to their patients. HCWs who acquire MRSA in hospital transmit the organism to their household eventually spreading such nosocomially acquired multidrug resistant bacteria in community. Therefore such carriage study should be conducted at regular basis in all health sectors followed by treatment of the identified carriers.
Although the use of Mupirocin may have a beneficial role in controlling the MRSA infection, the use of additional infection prevention practices is very important and it cannot be understated. The need is to educate the nursing staff regarding the Hospital infection control practices, as once introduced in hospital MRSA are very difficult to eradicate.