A Study of Methicillin-resistant Staphylococcus aureus Infections

Abstract

Staphylococcus aureus is a major cause of nosocomial infections including pneumonia, postoperative wound
infection, bacteremia and other infections. A major cause of concern in the treatment of S. aureus infections is the emergence
of methicillin-resistant Staphylococcus aureus (MRSA), which was reported just 1 year after the launch of methicilin. The
current study was undertaken to determine the prevalence of infection caused by S. aureus in hospitalized and outdoor
patients and to determine the prevalence of MRSA isolated from different clinical samples as well as to characterize the
patients with MRSA on the basis of risk factors. Material and methods: The present study was conducted in the Dept. of
Microbiology of a tertiary care hospital, from August 2009 to August 2011. Various clinical specimens such as pus, blood,
urine cerebrospinal fluid (CSF), pleural fluid, peritoneal fluid, ascitic fluid, bile, cervical swab, semen, conjunctival swabs
and ear swabs received in the Microbiology laboratory were studied. Culture was done on 4% NaCI Mueller-Hinton agar.
Carriers showing MRSA were prescribed mupirocin/chlorhexidine for treatment. Further culture was done on 5-10%
sheep blood agar, Mc-Conkey Agar, Mannitol salt agar and Robertson cooked meat broth. Subcultures from cooked meat
broth were performed if there was no growth on primary culture plates. Results: The present study comprised of 262
S. aureus isolates from various clinical specimens. All isolates were identified as S. aureus on the basis of morphology, culture
and biochemical characteristics. The current study shows that nearly 80% of the isolates were from the patients up to the
age of 40 years and thereafter isolation rate decreased with age. Out of total 262 isolates included in the study, 154 (58.78%)
isolates were from male patients and 108 (41.22%) were from female patients. Out of the 262 isolates, 204 (77.87%) were
from pus. Isolates from urine samples comprised 22 (8.39%) followed by CSF 8 (3.05%), endocervical swab 7 (2.67%) and
ear swab 7 (2.67%). Other samples included were seminal fluid 4(1.53%), sputum and throat swab 3 (1.15%), conjunctival
swab 2 (0.76%). Foley's tip 1 (0.38%) and umbilical tip 1 (0.38%). It was observed that in 217 (82.83%) patients infection was
hospital-acquired and 45 (17.17%) patients had community-acquired infection. Conclusion: In the present study, MRSA
isolation rates from ICU and wards were higher than that seen among outpatients. The most common risk factor present in
most of the patients with MRSA was prolonged stay in the hospital.