Coagulase negative staphylococci - a fast emerging threat.
OBJECTIVE
To determine the frequency of isolation of coagulase-negative staphylococci and their resistance to methicillin over a period of time.


METHODS
The descriptive cross-sectional study was carried out at Army Medical College, Rawalpindi, from June 2009 to May 2012, and comprised clinical samples mostly from patients admitted to the intensive care unit. They were inoculated onto appropriate culture media depending upon the specimen. After 24-hour incubation at 35°C, coagulase-negative staphylococci were identified on the basis of colony morphology, gram staining, a positive catalase and a negative tube coagulase test.Methicillin resistance among the isolated staphylococci was determined using a 30µg Cefoxitin disc as per the Clinical and Laboratory Standards Institute protocol. Number of coagulase-negative staphylococci for each year and their methicillin resistance rates were calculated. A comparison was made with methicillin resistant staphylococcus aureus) isolated during the same period.


RESULTS
Of the total 1331 specimens studies over three years, 581(43.65%) were coagulase-negative staphylococci. The rate of coagulase-negative staphylococci and methicillin resistance was higher each year; 110(26.6%) in May 2009-Jun 2010, 134(36.5%) in 2011, and 337(61%) in 2012. Methicillin resistance rates also increased from 25(22.7%) to 46(34.3%) and then to 201(59.6%) in 2012.Maximum isolated specimens came from blood 311(53.5%), followed by pus/swabs 204(35.1%).


CONCLUSIONS
The frequency of isolation of coagulase-negative staphylococci and its methicillin resistance among hospitalised patients is on the rise.
Department of Microbiology, Army Medical College Rawalpindi, National University of Sciences and Technology Islamabad, Pakistan.
Mahwish
M
Latif
Department of Microbiology, Army Medical College Rawalpindi, National University of Sciences and Technology Islamabad, Pakistan.
Javaid
J
Usman
Department of Microbiology, Army Medical College Rawalpindi, National University of Sciences and Technology Islamabad, Pakistan.
Mehreen
M
Gilani
Department of Microbiology, Army Medical College Rawalpindi, National University of Sciences and Technology Islamabad, Pakistan.
Tehmina
T
Munir
Department of Microbiology, Army Medical College Rawalpindi, National University of Sciences and Technology Islamabad, Pakistan.
Maria
M
Mushtaq
Department of Microbiology, Army Medical College Rawalpindi, National University of Sciences and Technology Islamabad, Pakistan.
Rabia
R
Anjum
D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology*; D001437:Bacteriuria / Q000453:epidemiology / Q000382:microbiology*; D003430:Cross-Sectional Studies; D006772:Hospitals, Military; D006801:Humans; D007362:Intensive Care Units; D016106:Methicillin Resistance / Q000502:physiology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification / Q000502:physiology; D008826:Microbial Sensitivity Tests; D010154:Pakistan / Q000453:epidemiology; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013210:Staphylococcus / Q000302:isolation & purification / Q000502:physiology; D041162:Staphylococcus haemolyticus / Q000302:isolation & purification / Q000502:physiology*; D057787:Staphylococcus lugdunensis / Q000302:isolation & purification / Q000502:physiology*; D057790:Staphylococcus saprophyticus / Q000302:isolation & purification / Q000502:physiology*; D013492:Suppuration / Q000453:epidemiology / Q000382:microbiology; D062606:Tertiary Care Centers
CoNS, Methicillin, MRCoNS.