Analysis of consecutive blood cultures performed in one year by an infectious team: were three haemocultures still necessary?

Abstract number: 1135_167

Ben Ali A., Males S., Kitzis M.D., Nguyen Van J.C., Sanz R., Carlet J., Goldstein F.W.

Introduction:  

Blood cultures for the purpose of isolating blood-borne pathogens have routinely included the use of media for detection of both aerobic and anaerobic organisms. Although methods for the detection of anaerobic bacteria from blood cultures have improved, the per cent recovery of anaerobes isolated from blood cultures has declined. This study analyses all blood culture isolates in view of clinical condition for one year.

Materials:  

During the year 2002 the infectious disease team (IDT), who help for the diagnosis and treatment of all infected patients in Saint-Joseph hospital, analysed all the positive bottles. The IDT determined the clinical significance of all blood positive culture. Contamination was determined if one bottle out of two or three sets (2 bottles) collected on the same day grew with coagulase negative staphylococci, corynebacterium species, bacillus species and if there is a habitual pathogen with no clinical signification and clinical improving without treatment. A beginning of antibiotherapy in case of false positive positive bacteraemia was reported.

Results:  

For the year 2002, 8094 sets were utilised. 931 were positives. 377 (40 %) bottles were considered as contamination with 207 (22 %) aerobic and 170 (18%) anaerobic, concerning 274 patients. 31 contaminations induced antibiotic therapy. 554 bottles were considered as a true bacteraemia for 487 patients. 48 (%) bacteriemic patients have positive anaerobic bottle only. Bacteria present only in anaerobic bottle were anaerobes (16 cases), Staphylococcus aureus (5 cases), Escherichia coli (14 cases), others enterobacteriacae (8 cases), 2 Streptococcus pneumoniae and others streptococci (5 cases). Infections concerned in these cases were intra-abdominal (27 cases), soft-tissue infections (3 cases), pyelonephritis (11 cases) and others (7 cases). 35 of 48 bacteriemic patients in only anaerobic bottle were positives since the first set, 12 since the second set with 8 patients treated with active antibiotherapy and one patient in the fourth set.

Conclusion:  

In view of these results, we think that only 2 sets of bottles are necessary for blood stream infection diagnostic.