Time-to-positivity, type of culture media and oxidase test performed on positive blood culture vials to predict Pseudomonas aeruginosa in patients with Gram-negative bacilli bacteraemia.

OBJECTIVE: The aim of this study was to determine the usefulness of oxidase test and time-to-positivity (TTP) in aerobic and anaerobic blood culture vials to detect the presence of Pseudomonas aeruginosa in patients with Gram-negative bacilli (GNB) bacteraemia. METHODS: TTP was recorded for each aerobic and anaerobic blood culture vial of monomicrobial bacteraemia due to GNB. Oxidase test was performed in a pellet of the centrifuged content of the positive blood culture. An algorithm was developed in order to perform the oxidase test efficiently taking into account TTP and type of vial. RESULTS: A total of 341 episodes of GNB bacteraemia were analysed. Sensitivity, specificity, positive predictive value and negative predictive value of the oxidase test performed on positive vials with GNB to predict P. aeruginosa were 95%, 99%, 91%, and 99%, respectively. When growth was first or exclusively detected in anaerobic vials, P. aeruginosa was never identified hence the performance of the oxidase test could be avoided. When growth was only or first detected in aerobic vials, a TTP≥8h predicted P. aeruginosa in 37% or cases (63 of 169), therefore oxidase test is highly recommended. CONCLUSIONS: Oxidase test performed onto positive blood culture vials previously selected by TTP and type of vials is an easy and inexpensive way to predict P. aeruginosa. In most cases, this can lead to optimization of treatment in less than 24 hours.

Development of a new protocol for rapid bacterial identification and susceptibility testing directly from urine samples.

The current gold standard method for the diagnosis of urinary tract infections (UTI) is urine culture that requires 18-48 h for the identification of the causative microorganisms and an additional 24 h until the results of antimicrobial susceptibility testing (AST) are available. The aim of this study was to shorten the time of urine sample processing by a combination of flow cytometry for screening and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) for bacterial identification followed by AST directly from urine. The study was divided into two parts. During the first part, 675 urine samples were processed by a flow cytometry device and a cut-off value of bacterial count was determined to select samples for direct identification by MALDI-TOF-MS at ≥5 × 10(6) bacteria/mL. During the second part, 163 of 1029 processed samples reached the cut-off value. The sample preparation protocol for direct identification included two centrifugation and two washing steps. Direct AST was performed by the disc diffusion method if a reliable direct identification was obtained. Direct MALDI-TOF-MS identification was performed in 140 urine samples; 125 of the samples were positive by urine culture, 12 were contaminated and 3 were negative. Reliable direct identification was obtained in 108 (86.4%) of the 125 positive samples. AST was performed in 102 identified samples, and the results were fully concordant with the routine method among 83 monomicrobial infections. In conclusion, the turnaround time of the protocol described to diagnose UTI was about 1 h for microbial identification and 18-24 h for AST.

[Compliance with antibiotic treatment in nonhospitalized children]. / Cumplimiento del tratamiento antibiótico en niños no hospitalizados.

OBJECTIVE: To evaluate compliance with antibiotic treatment in children and to determine the factors that may be associated with compliance with antibiotic treatment in children not in hospital. DESIGN: Prevalence study. SETTING: La Rioja primary care centres. PATIENTS AND OTHER PARTICIPANTS: 384 children from 0 to 10, not in hospital, who needed antibiotic treatment between October 1998 and January 1999. MEASUREMENTS AND MAIN RESULTS: Antibiotic compliance was measured with the Morisky-Green test through a phone survey of the parents ten days after the treatment was prescribed. The number of children who complied satisfactorily with the prescribed treatment was 214 (55.7%; 95% CI, 50.6-60.7). Correct compliance was more common in children with 12-hour rather than 8-hour intervals (OR: 1.87; CI OR, 1.23-2.85), and in children who went to nursery rather than children at school (OR: 1.77; CI OR, 1.08-2.91). CONCLUSIONS: Correct compliance in the study was low. Approximately half the children prescribed an antibiotic treatment at two or three doses a day took it as the paediatrician had indicated.