Abstract
The aim of this study is to determine the species distribution, slime activity, and methicillin resistance of coagulase-negative staphylococci (CoNS) isolated from blood cultures as either contaminants or true bacteremia agents. In this study, 13.268 blood culture samples sent to our laboratory from various clinics during a two-year period were examined in terms of the presence of CoNS to clarify whether the isolates are true bacteremia agents, as defined by Centers for Disease Control and Prevention (CDC) criteria. The slime activities of true bacteremia agents (58 CoNS strains) and contaminants (50 randomly selected CoNS strains) were investigated by the Christensen method. The methicillin susceptibilities of the strains were determined by the disk diffusion method. Although the frequency of slime production was 39.7% among the true bacteremia CoNS agents, it was 18% in CoNS that were judged to be contaminants (p<0.05). S. epidermidis was the most frequently isolated species for both the true bacteremia agent group (56.9%) and contaminant group (74%). Additionally, S. epidermidis was the bacterium most frequently characterized as slime producing in both groups. The methicillin resistance of slime-producing CoNS was determined to be 82.6% for the true bacteremia agent group and 77.8% for the contaminant group. The presence of slime activity in CoNS isolated from blood culture samples is supportive evidence that they are most likely the agents of true bacteremia cases.
Highlights
Coagulase-negative staphylococci (CoNS) typically reside on healthy human skin and mucous membranes, rarely cause disease, and are most frequently encountered by clinicians as contaminants of microbiological cultures [1]
The presence of slime activity in CoNS isolated from blood culture samples is supportive evidence that they are most likely the agents of true bacteremia cases
To clarify whether the CoNS isolated from these blood cultures are true bacteremia agents, laboratory-confirmed bloodstream infection criteria defined by the Centers for Disease Control and Prevention (CDC) were used [5]
Summary
Coagulase-negative staphylococci (CoNS) typically reside on healthy human skin and mucous membranes, rarely cause disease, and are most frequently encountered by clinicians as contaminants of microbiological cultures [1]. This situation has changed over the last decade, and CoNS are being recognized as important causes of nosocomial infections [2]. The predominant Staphylococcus species of humans, S. epidermidis, is widely distributed over the body surface. S. epidermidis is by far the most frequently recovered organism in bacteremia cases, accounting for 50% to over 80% of isolates. Other commonly implicated species include S. haemolyticus, S. lugdunensis, S. schleiferi, S. warneri, S. hominis, S. simulans, and S. saccharolyticus [4]
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