2017, Cilt 47, Sayı 2, Sayfa(lar) 089-093 |
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Comparison of Demographic and Some Clinical Features of Patients Whose Blood Cultures Revealed Growth of Coagulase Negative Staphylococci and Differentiation Between Infectious Agent and Contaminant was Performed According to the CDC Criteria |
Yasemin Derya GÜLSEREN1, Ayşe Esra KARAKOÇ1, Gamze TÜRKOĞLU1, Cemal BULUT2 |
1Ankara Eğitim ve Araştırma Hastanesi, Tıbbi Mikrobiyoloji Bölümü, Ankara 2Ankara Eğitim ve Araştırma Hastanesi, Enfeksiyon Hastalıkları ve Klinik Mikrobiyoloji Bölümü, Ankara |
Keywords: True bacteremia, blood stream infection, coagulasenegative staphylococcus, infecting pathogen, contamination |
Objective: Coagulase negative staphylococci (CoNS) cause health care
associated circulatory system infections. They are also the inhabitants of
normal skin flora. In this study we aimed to evaluate use of various
clinical and laboratory parameters of the patients whose blood cultures
revealed growth of CoNS so as to differentiate between infectious agent
and contaminant in the blood cultures of these patients.
Material and Methods: The classification of CoNS isolated from the
blood cultures as a real pathogen or a contaminant was based on the
evaluation of the infection control team that used the CDC criteria.
According to this evaluation the study group with CoNS as the infecting
agent consisted of 25 patients and the control group with CoNS as the
contaminant consisted of 50 patients. The clinical and laboratory
parameters were compared using the software of SPSS 21.0. Mann-
Whitney U test was used to compare means of the study parameters.
Pearsons khi-square test and Fishers exact khi-square test were used
to compare the categorical variables.
Results: Two groups were compared in terms of clinical and laboratory
parameters. The presence of central venous catheter (p=0.02) and
duration of stay in hospital prior to infection (p=0.001) was significantly
different between groups. Presence of one or more SIRS criteria
(temperature >38°C or <36°C, heart rate >90bpm, leucocyte count
>12000 or <4000/mm3, percentage of immature neutrophils >10%)
was also compared. There was no difference between two groups in
terms of presence of one or more SIRS criteria.
Conclusion: It is hard to differentiate between a pathogen/contaminant
CoNS isolated from blood culture set of a patient. The decision
becomes even harder if a second blood culture set has not been sent.
The laboratory tries to come to a conclusion by considering clinical
and laboratory parametres concerning the patient. In our study fever,
heart rate, white blood cell count, systolic and diastolic blood
pressures, presence of a dialysis catheter, surgery and resistance to
methicilline per se did not not help to arrive at a correct conclusion.
Differentiation between pathogen and contaminant CoNS grown in
blood cultures seems to continue to be one of the most problematic
issues in daily practice with respect to both routine microbiology
laboratories and clinicians.
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