Evaluation of blood culture epidemiology and efficiency in a large European teaching hospital.

BACKGROUND: Blood cultures remain the gold standard for detecting bacteremia despite their limitations. The current practice of blood culture collection is still inefficient with low yields. Limited focus has been given to the association between timing of specimen collection at different time points during admission and their yield. METHODS: We carried out a retrospective observational study by analyzing all 3,890 sets of cultures collected from the 1,962 admitted patients over the seven-month period of this study. We compared the blood culture yield between the early group (≤24 hours after admission) and the late group (> 24 hours of admission). We also investigated the effect of prehospital oral antibiotics and pre-analytical time on the first cultures in the emergency department. Epidemiology and efficiency of blood cultures were studied for each medical specialty. RESULTS: In total, 3,349(86.1%) blood cultures were negative and 541(13.9%) were positive for one or more microorganisms. After correcting for contamination, the overall yield was 290 (7.5%). The early group (n = 1,490) yielded significantly more true-positive cultures (10.1% versus 5.8%, P<0.001) than the late group (n = 2,400). The emergency department had a significantly higher yield than general wards, 11.2% versus 5.7% (p<0.001). Prehospital oral antibiotic use and pre-analytical time did not affect the yield of first cultures at the emergency department (p = 0.735 and 0.816 respectively). The number of tests needed to obtain one true-positive culture varied between departments, ranging from 7 to 45. CONCLUSION: This study showed that blood cultures are inefficient in detecting bacteremia. Cultures collected during 24 hours after admission yielded more positive results than those collected later. Significant variations in blood culture epidemiology and efficiency per specialty suggest that guidelines should be reevaluated. Future studies should aim at improving blood culture yield, implementing educational programs to reduce contamination and cost-effective application of modern molecular diagnostic technologies.

Five-minute Giemsa stain for rapid detection of malaria parasites in blood smears.

The Giemsa stain is used as the gold standard for the diagnosis of malaria on blood smears. The classical staining procedure requires between 30 and 45 min. We modified the Giemsa stain and reduced the staining time to 5 min without any loss of quality.

Pharmacokinetics of intraventricularly administered teicoplanin in Staphylococci ventriculitis.

Following craniotomy for a medulloblastoma in the posterior cranial fossa, a 6-year old girl developed a ventriculitis with coagulase negative staphylococci associated with the use of a ventriculostomy. Treatment with intravenous (i.v.) and intraventricular (ivt) vancomycin resulted in negative cultures of the cerebrospinal fluid, but had to be stopped because of a severe allergic skin reaction. Teicoplanin was administered i.v. (240 mg once daily) and ivt (10 mg once daily), resulting in high teicoplanin CSF levels that were used to model the pharmacokinetics of ivt teicoplanin in this patient. No signs of recurrent infection or adverse events occurred. It is concluded that a pharmacokinetic model can be derived from this case that can be used as prior to guide teicoplanin intraventricular therapy in other patients.

Role of bacterial virulence factors and host factors in the outcome of Escherichia coli bacteraemia.

In a study of the role of virulence factors in the outcome of Escherichia coli bacteraemia, blood isolates from 30 hospitalised patients were characterised with regard to O and K antigens, P and type 1 fimbriae, haemolysin production, cytonecrotising factor 1 production, serum resistance, ability to activate neutrophils and resistance to killing. Patients were analysed to identify host factors contributing to morbidity and mortality. In univariate analyses the presence of a K antigen, type 1 fimbriae, absence of haemolysin production, serum resistance and resistance to killing were associated with morbidity and mortality. In multivariate analyses only the absence of haemolysin production was associated with morbidity and mortality, after taking host factors into account. These preliminary findings suggest that host factors override bacterial virulence factors in determining the course of Escherichia coli bacteraemia. The negative association between haemolysin production and clinical deterioration during Escherichia coli bacteraemia might indicate predominance of less virulent strains in patients with other risk factors for morbidity and mortality or inactivation of neutrophil products needed for host defence.

Frequencies of lipopolysaccharide core types in Escherichia coli strains from bacteraemic patients.

We have investigated the distribution of the various core types (R1, R2, R3, R4 and K-12) in 138 Escherichia coli isolates obtained from positive blood cultures. Rabbit antisera, raised against five rough strains expressing the respective core types, were made monospecific by extensive absorption. The reactivity of the antisera was tested in ELISA with bacterial cells that had been autoclaved for full exposure of core epitopes. One hundred and thirty strains could be typed directly, while eight strains required prior digestion with proteinase K for removal of cross-reactions. Ninety-four of the strains (68%) expressed the R1 type, and 9 (6.5%), 12 (8.7%), 7 (5.1%) and 3 (2.2%) strains expressed the R2, R3, R4 and K-12 core types, respectively. An R1R4 mixed core type, hitherto not yet described, was found in 13 (9.4%) strains. Results obtained with polyclonal antisera were in agreement with those obtained with monoclonal antibodies to the R1, R2 and R3 core types. Core typing may serve as an additional serological marker next to conventional typing of O-, H- and K-antigens.

Haemoptysis and an abnormal X-ray after prolonged treatment in the ICU.

We describe a case of Nocardia bronchopneumonia occurring in a patient after 5 weeks of treatment in an ICU. The clinical features were haemoptysis and fever, and an aspecific coarse nodular pattern on the chest roentgenogram. The diagnosis was made, after death, by positive blood cultures for Nocardia asteroides and autopsy showing Nocardia bronchopneumonia.

A nosocomial outbreak of amoxycillin-resistant non-typable Haemophilus influenzae in a respiratory ward.

A nosocomial outbreak of acute bronchitis due to amoxycillin-resistant, non-typable Haemophilus influenzae occurred in a 23-bed unit, housing patients with respiratory disorders. Within a period of one month, 13 patients and two, previously healthy, members of staff were affected. The isolates were studied for strain relatedness by serotyping, biotyping and major outer membrane protein (MOMP) profiles after SDS-polyacrylamide gel electrophoresis; 13 of the isolates belonged to the same biotype and MOMP type, indicating cross-infection. Routine throat cultures of all patients and personnel were undertaken. To stop the epidemic, patients and nurses positive for amoxycillin-resistant H. influenzae were isolated or sent home and, if symptomatic, were treated with co-trimoxazole. We stress the importance of early intervention when amoxycillin-resistant H. influenzae strains occur in a ward.

Pressure transducers: an overlooked source of sepsis in the intensive care unit.

Between January 1988 and May 1989 twenty cases of bacteremia due to Flavobacterium sp. occurred in 17 patients admitted to a surgical intensive care unit. Epidemiologic studies disclosed that the source of the Flavobacterium bacteremias was contaminated reusable pressure transducers. Despite the use of disposable domes spread of the bacteria from the contaminated transducer heads to the fluids given to the patients occurred. An indirect contamination by hands at the time the equipment was initially assembled must have been the mode of transmission. Reinstitution of routine disinfection of the transducer heads controlled the outbreak. Disposable domes failed to prevent septicemia from contaminated pressure transducers.