271 - Management of blood cultures show institutional (basic) good quality: review and case records in the laboratory of Rovereto

Autor(s): M. Schinella, P. Gualdi, L. Collini, A. Smaniotto

Issue: RIMeL - IJLaM, Vol. 4, N. 4, 2008 (MAF Servizi srl ed.)

Page(s): 271-279

Background. Blood culture represents the basic test to detect blood infections as: bacteremia, sepsis and septic shock and cardiac infections as: endocarditis, myocarditis and pericarditis. Since blood culture is important for the diagnosis of infectious diseases, we thought it was useful to make a review of the test requests. Methods. In our laboratory is in use the automated system Bactec 9240 (Becton Dickinson, Milano, Italia). We evaluated the number of blood cultures requested in our hospital in the years 2004, 2005 and in the first six months of 2006 with the aim to make evidence, in addition to the total number of cultures processed, on the requests from singles wards, type of microorganisms often isolated, true positive samples, time of positivity detection and contaminations. We also described the time bands during which communications to the wards were made. Results. The number of culture requests has been continuously increasing: 2109 pair of bottles (positive 5.6%) were accepted in 2004, 3062 (positive 15.6%) in 2005 and 2081 (positive 7.9%) in the first six months of 2006. False positive samples were 4.3% in 2004, 3.5% in 2005, while in the first six months of 2006 were 1.1%. Samples defined as contaminated were 1.1% in 2004, 0.9% in 2005 and 0.7% in 2006. Most of the requests belonged to medical ward, corresponding to 42.2% of the total pairs of bottles accepted in 2004, 37.4% in 2005 and 40.4% in the first six months of 2006, followed by Geriatrics and Intensive Care unit. Cardiology unit showed the highest rate of positive samples (13%), followed by Surgery (12.8%). In 2004 the Neurology unit showed the highest number of false positive samples (2.7%), in 2005 Orthopedics (7.1%) and again Orthopedics in 2006 (2.7%). In 2004 Orthopedics showed the highest number of contaminated samples, in 2005 Neurology (2%) and in 2006 (six months) Medical ward (0.9%). The most frequently isolated microorganisms were coagulase negative staphylococci, representing the 41.3% of total isolated bacteria, followed by E. coli (18%) and Staphylococcus aureus (11.9%). Intensive Care and Surgery units showed a high incidence of Candida spp. Since in the Pediatrics personnel doesn’t usually inoculate pair of bottles, the reported data concern single bottles and are discussed separately. The time band during which the positivity of the samples was communicated by telephone, was between 8:05 and 17:00. Conclusions. The positivity rate was mostly unchanged. Generally to increased number of requests did not correspond an increased number of positive samples, on the other hand in Pediatrics to an increased detection of positive samples corresponded an increased number of contaminations. Gram negative bacteria were detected mostly in Surgery (probably following abdominal surgery or catheters), Internal Medicine, Orthopedics, Intensive Care and Geriatrics. Gram positive bacteria were detected mostly in Neurology, Cardiology, Infectious Disease and Pediatric units. During the time of observation, in Pediatrics the number of blood culture requests and the number of contaminated samples basically didn’t change. The telephone communications of the results influence the therapeutic decision since they precede by 24-48 hours the laboratory results concerning bacterial identification and antibiotic assay.

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