Coagulase Negative Staphylococci from Blood Cultures Contaminants or Pathogens? (original) (raw)
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West Indian Medical Journal, 2006
The prevalence and significance of coagulase negative staphylococci (CoNS) isolated from blood cultures at the University Hospital of the West Indies (UHWI) during a six-month period were investigated. Standard and automated microbiological procedures were used to process 3001 blood culture specimens received from 2363 patients and 658 (21.9%) of the blood cultures yielded 854 bacterial isolates. The highest prevalence of positive blood cultures (60%) and the lowest prevalence of blood isolates of CoNS (12%) were found in the intensive care unit (ICU). The blood isolates of CoNS were most frequent in the surgical wards (13%) and lowest in obstetrics and gynaecology (2%). High rates of resistance to methicillin, other anti-staphylococcal penicillins, and cephalosporins used in the treatment of CoNS were observed. All blood isolates of CoNS (100%) were susceptible to vancomycin. In conclusion, the results show that coagulase-negative staphylococci are the most prevalent bacterial isolates in blood cultures at the UHWI occurring mostly as contaminants. The practice of proper venepuncture and hand-washing techniques by medical staff are recommended to facilitate appropriate antibiotic usage.
Determination of clinical significance of coagulase-negative staphylococci in blood cultures
The aim of this study was to investigate the criteria used to distinguish coagulase-negative staphylococci (CoNS) bacteremia from contamination. We evaluated 162 adult patients with CoNS-positive blood cultures (BCs). Of the 162 patients, 35 (21.6%) had at least 2 positive BCs and 127 (78.4%) had a single positive BC. According to the Laboratory Confirmed Bloodstream Infection (LCBI) criteria, 24 (14.8%) patients with the same species of CoNS had true bacteremia, and 138 (85.2%) patients had contaminants. Despite the detection of the same CoNS species, 9 of the 24 patients had different CoNS genotypes. Using clinical assessments, only 20 patients were diagnosed with true bacteremia, 8 of them had a single positive BC. We concluded that only using the LCBI criteria or clinical evaluations of a patient were not sufficient to distinguish CoNS bacteremia from contamination. Molecular identification should also be performed as a diagnostic laboratory parameter for CoNS bacteremia.
1998
A blood culture cohort study investigating issues related to isolation of coagulase-negative staphylococci (CoNS) and other skin microflora is reported. Data were collected over 12 weeks to determine the incidence of significant CoNS bacteremia versus that of pseudobacteremia (contaminants) and to evaluate drug therapy in patients with cultures positive for CoNS. In addition, the effectiveness of 0.2% chlorine peroxide as a bactericidal disinfectant was compared to that of 10% providone iodine. A total of 3,276 cultures of blood from 1,433 patients were evaluated in the study. Eighty-nine cultures were positive for skin flora, with 81 of 89 (91%) involving CoNS. The incidence of significant CoNS bacteremia was 20 of 81 (24.7%), that of indeterminate bacteremia was 10 of 81 (12.3%), and that of contamination was 59 of 81 (72.8%). The incidence of significant bacteremia involving CoNS was double the 10 to 12% rate based on previous estimations at our institutions. In tests with the two bactericidal disinfectants, 22 of 1,639 cultures (1.3%) in the chlorine peroxide group versus 37 of 1,637 (2.3%) in the providone iodine group were considered contaminated (P ؍ 0.065). Rates of contamination for venipuncture versus catheter collection were not significantly different (P ؍ 0.46). The overall contamination rate was 59 of 3,276 (1.8%), which is consistent with the lower end of published quality assurance benchmark standards. The low rate was believed to be due to the professional phlebotomy staff in our institutions. There was excellent agreement between retrospective analysis by reviewers, when formal criteria were used, and the attending physicians' intuitive clinical impressions in the classification of significant bloodstream infections (100% agreement) or contamination (95% agreement). However, physicians still used antimicrobial agents to treat nearly one-half of the patients with contaminated blood cultures, with vancomycin being misused in 34% of patients. In addition, 10% of patients with significant bacteremia were treated with inappropriate agents. There were no significant adverse events or prolonged hospital stays due to the unnecessary use of vancomycin; however, the additional costs of treating patients whose cultures contained CoNS contaminants was estimated to be $1,000 per patient. Measures to limit the unnecessary use of vancomycin (and other agents) are important.
Journal of Medical Microbiology, 2004
Coagulase-negative staphylococci (CNS) are frequently isolated from blood cultures, where they may be only a contaminant or the cause of bacteraemia. Determining whether an isolate of CNS represents a true CNS bacteraemia is difficult, and there is no single criterion with sufficient specificity. The aim of this study was to assess those clinical, microbiological, pathogenic and genotypic features that characterize true CNS bacteraemia. Twenty patients having two or more blood cultures positive for CNS and 20 patients with only one positive blood culture were studied. Significant bacteraemia was defined according to clinical and laboratory criteria. Incubation time for blood cultures to become positive, macroscopic appearance of colonies, species determination, biotype, susceptibility to antimicrobials, PFGE pattern and adherence capacity were all studied. Clinical bacteraemia was present in 16/20 patients with two or more positive blood cultures and in 2/ 20 patients with only one positive blood culture. A significant difference was seen in the median time to positivity between the 18 clinical bacteraemias and 22 contaminations (23 . 6 versus 29 . 2 h; P ¼ 0 . 04, Wilcoxon). There was also a significant difference between the two groups in the median absorbance of the slime test (1 . 36 versus 0 . 58; P ¼ 0 . 005). All significant bacteraemias with two or more positive blood cultures had the same species identified, the same antimicrobial susceptibility pattern and the same PFGE pattern. In two patients with true bacteraemia with only one positive blood culture, the incubation time for the culture to turn positive was ,24 h and the slime production absorbance was .2 . 5. The most useful parameters for the diagnosis of true CNS bacteraemia for patients with two positive blood cultures were incubation time until positive, species identification, antimicrobial susceptibility pattern, slime production and PFGE pattern. For patients with only one blood culture positive for CNS, the useful parameters for prediction of true bacteraemia were incubation time until positive and slime production, both of which are simple, low-cost tests.
The significance of coagulase-negative staphylococci bacteremia in a low resource setting
The Journal of Infection in Developing Countries, 2013
Introduction: Coagulase-negative staphylococci (CoNS) are a group of micro-organisms that are increasingly implicated as a cause of significant infection and the leading cause of bloodstream infection (BSI). One important predictor of true BSI is the isolation of CoNS from multiple blood cultures, presuming that the isolates represent the same species. Thus the objective of this study was to determine the significance of repeated CoNS isolated from blood cultures. Methodology: This was a prospective laboratory study which was initiated in June 2007 and lasted until July 2008. CoNS isolates were obtained from patients who had two positive blood cultures within a 14-day interval. CoNS were identified to the species level using an API-Staph, and antibiotics susceptibility testing was performed according to Clinical and Laboratory Standards Institute specifications. Strain relatedness was confirmed using pulsed-field gel electrophoresis. Results: During the study period, 202 CoNS-positi...
Journal of clinical microbiology, 1997
We applied pulsed-field gel electrophoresis (PFGE) after SmaI digestion and random amplification of polymorphic DNA (RAPD) analysis with nine oligonucleotide primers to 146 blood culture isolates of Staphylococcus epidermidis and 25 blood culture isolates of Staphylococcus haemolyticus. These were obtained over a 12-month period from patients on the neonatal and hematology units of the Central Manchester Health Care Trust. PFGE demonstrated two clusters of isolates of S. epidermidis (type A and type B) on the neonatal ward and a single cluster (type C) on the hematology unit. Type A was represented by 10 indistinguishable isolates from nine patients, type B was represented by 20 isolates from 14 patients, and type C was represented by 26 isolates from 10 patients. Type A isolates were resistant to chloramphenicol and type C isolates were resistant to ciprofloxacin, mirroring current antibiotic usage. There was no evidence of cross infection due to S. haemolyticus. RAPD analysis, on ...
Dirasat. Medical and biological sciences
Background: Coagulase-negative staphylococci (CoNS) are a major cause of nosocomial blood stream infection, especially in critically ill and haematology patients. CoNS are usually multidrugresistant and glycopeptide antibiotics have been to date considered the drugs of choice for treatment. The aim of this study was to characterize CoNS with reduced susceptibility to glycopeptides causing blood stream infection (BSI) in critically ill and haematology patients at the
Clinical and antimicrobial profile of Coagulase Negative staphylococci in a tertiary care hospital
International Journal of Research in Medical Sciences
Background: Coagulase negative staphylococci (CoNS) are gaining importance because of their role as pathogens in certain clinical conditions and their marked resistance to antibiotics. Their species distribution and slime production has important correlation with the antimicrobial susceptibility pattern. Aim of this study was to determine clinically significant CoNS, their species distribution, slime production and antimicrobial susceptibility pattern in a tertiary care hospital.Methods: Identification, speciation and antimicrobial sensitivity testing were performed using standard microbiological techniques. Slime production was also tested by microtiter plate. Antimicrobial susceptibility testing was performed by modified Kirby Bauer method as per the CLSI guidelines.Results: A total 204 (49.88%) CoNS were found to be clinically significant. Percentage of clinical significance was high in urine isolates (88.88%) followed by pus (47.78%) and blood (45.56%). The most common CoNS infe...
Journal of clinical microbiology, 1995
The frequency of strain relatedness was determined among randomly selected patients with coagulase-negative staphylococcal infections as determined in multiple blood cultures by plasmid typing, determination of species, and antibiotyping. Strain relatedness was demonstrated in 21 of 47 episodes of bacteremia (44.7%) among 34 patients, with a similar percentage among patients with two or one positive blood culture in 24 h (14 of 30 [46.7%] versus 7 of 17 [41.2%], respectively). Same-strain bacteremia was more frequent in cases of infection among patients with a corresponding fever (15 of 21 [71.4%]), among patients infected with organisms from an identifiable source (7 of 9 [77.8%]) and with non-Staphylococcus epidermidis species (9 of 11 [81.8%]), and among patients with nosocomially acquired infections (18 of 36 [50%]). Comparing episodes with or without strain relatedness, no difference was noted in the time to growth (2.1 +/- 1.4 versus 1.9 +/- 0.9 days, respectively), in bacteri...