Abstract
BackgroundCoagulase negative staphylococci were long regarded non-pathogenic as they are the commensals of human skin and mucosa but the recent changes in the medical practice and changes in underlying host populations, they are being considered significant pathogens associated with number of nosocomial infections. The objective of the study was to determine the species, antimicrobial susceptibility pattern, biofilm forming ability of the clinically significant CoNS isolates and to compare the different methods for the detection of biofilm formation.MethodsA total of 52 clinically significant CoNS isolates obtained from different units during a year period were studied. Characterization was done using standard microbiological guidelines and antimicrobial susceptibility was done following CLSI guidelines. Biofilm formation was detected by using three methods i.e. tissue culture plate method, congo red agar method and tube adherence method.ResultsAmong 52 isolates, S. epidermidis (52%) was the most common species which was followed by S. saprophyticus (18%) and S. haemolyticus (14%). Antimicrobial susceptibility pattern of CoNS documented resistance of 80% to ampicillin. Resistance to cefoxitin and ceftriaxone was observed in 58% of the isolates. Biofilm formation was observed in 65.38% of the isolates. The accuracy of Congo red agar and tube adherence method for the detection of biofilm formation was 82% and 76% respectively.ConclusionCoNS isolates obtained from clinical samples should be processed routinely and antimicrobial susceptibility testing should be performed. Multidrug-resistant CoNS are prevalent. All the three methods i.e. tissue culture plate, Congo red agar and tube adherence method can be used in detecting biofilm formation.
Highlights
Coagulase negative staphylococci were long regarded non-pathogenic as they are the commensals of human skin and mucosa but the recent changes in the medical practice and changes in underlying host populations, they are being considered significant pathogens associated with number of nosocomial infections
Methicillin resistance was confirmed by minimum inhibitory concentration (MIC) of oxacillin against these isolates
Susceptibility to vancomycin was confirmed by calculating MIC of vancomycin against these isolates (Fig. 2)
Summary
Coagulase negative staphylococci were long regarded non-pathogenic as they are the commensals of human skin and mucosa but the recent changes in the medical practice and changes in underlying host populations, they are being considered significant pathogens associated with number of nosocomial infections. CoNS is considered one of the most common causes of the device related infections in the recent two decades, especially in immunocompromised patients and the chronic debilitated patient who need the long-term central venous access [3]. They may adhere to medical devices and surfaces through slime layer which has a muco-polysaccharide structure, they may colonize and spread within the hospital environment. Studies suggest that selective advantage for CoNS in causing device associated infections is Shrestha et al Antimicrobial Resistance and Infection Control (2017) 6:89 achieved by its ability to adhere to plastic catheters more aggressively than any other organism [5]
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