While rapid bacterial identification and susceptibility testing led to earlier changes and a significant reduction in antibiotic use, they did not reduce mortality.

The aim of this prospective randomized controlled clinical trial was to assess the impact of immediate incubation of blood cultures delivered to the laboratory outside its hours of operation on turnaround times, antibiotic prescription practices, and patient outcomes. A continuously monitoring blood culture incubator was placed outside the laboratory, which was switched on (intervention arm) and off (control arm) in a randomized manner. Included were new bacteremia episodes of patients older than 18 years. During the 30-week study period, the first positive blood culture specimen of an episode had to be brought to the laboratory outside its hours of operation. The median time from specimen collection until growth detection was reduced by 10.1 h in the intervention arm (P < 0.001). For 46 of 66 (70%) episodes in the intervention arm and for 51 of 85 (60%) episodes in the control arm, the antibiotic regimen was changed (not significant). The median time until the first change in the antibiotic regimen was 42.8 h in the intervention arm and 64.0 h in the control arm (P, 0.024). There was no difference in length of stay or hospital mortality. Immediate incubation of blood cultures outside laboratory hours reduces turnaround times and accelerates antibiotic switching.Appropriate antibiotic therapy for bacteremia is associated with a decrease in mortality (10). Shortening the period during which no therapy or only empirical therapy is given may result in improved patient outcomes. A major step in reducing mortality rates (6), costs (1), and antibiotic use was the introduction of microbiological diagnostic systems that reduce the turnaround time of tests for the identification and susceptibility testing of bacterial pathogens.Probably the most important moment for changing antibiotic therapy is when the results of blood culture specimens from patients with signs and symptoms of severe sepsis become available. Blood culture specimen analysis was considerably improved by the introduction of automated blood culture systems.Our hypothesis was that immediate incubation of blood culture bottles would shorten the time until antibiotic therapy is changed and therefore might improve patient outcomes. With this aim, we placed a continuously monitoring blood culture incubator (Bactec 9120; Becton Dickinson, Sparks, MD) outside the laboratory. We assessed the impact of immediate incubation of blood cultures delivered to the laboratory after the hours of operation on turnaround times, the time to antibiotic regimen change, in-hospital mortality, and hospital stay in a randomized, controlled clinical trial. MATERIALS AND METHODSSetting. The Erasmus University Medical Centre is a 1,200-bed tertiary-care university medical center. The Department of Medical Microbiology and Infectious Diseases has its laboratory integrated with an active infectious-disease (ID) consultation service run by a team of M.D. microbiologists and infectious-disease specialists. This ID consultation service operates 24 h per day, 7 days per week.The laboratory...

In a prospective observational study of bacteremic patients we ascertained the influence of different parts of culture results on the correctness of empirical antibiotic therapy. Ninety-three bacteremic patients requiring antibiotic treatment were included. Patients who had consultations with an infectious disease consultation service before they became bacteremic received microbiologically correct empirical antibiotic therapy more often than those who did not have such consultations (75% versus 53%; P ‫؍‬ 0.03). As a direct result of Gram staining, 92% of all patients received microbiologically correct antibiotic therapy. Severe sepsis is a major health care problem, affecting millions of patients each year. The incidence of sepsis and septic shock is increasing, and the mortality rate is 25% (2). Byl et al. have shown that results of blood culture identification and susceptibility increase appropriate antibiotic treatment significantly, from 63% to 94%, and that empirical therapy is significantly more often correct if prescribed by infectious disease specialists (1).We performed an observational prospective cohort study of positive blood cultures to determine which part of the culture results-Gram stain from positive blood cultures or identification or susceptibility of the microorganisms-was most influential on antibiotic treatment. Furthermore, the effect of infectious disease consultations on the correctness of empirical therapy was measured.The Erasmus Medical Center (MC) is a 1,200-bed tertiarycare university medical center. The Department of Medical Microbiology and Infectious Diseases has its laboratory integrated with an active infectious disease (ID) consultation service run by a team of medical microbiologists and infectious disease specialists, including residents in training. This ID consultation service operates 24 hours a day, 7 days a week. The ID consultants actively trace the attending physician in case of a positive blood culture and recommend antibiotic treatment. ID consultants are also frequently consulted for advice on empirical treatment.Blood cultures were processed with the Bactec system (Becton Dickinson, Sparks, MD). Identification and susceptibility testing were performed with the Vitek system (1 or 2; bioMérieux, Marcy l'Étoile, France). During the off-shift, no blood culture bottles were processed and no identification or susceptibility results were made available.A total of 171 consecutive patients were included; patients could be included only once. A questionnaire was filled in by ID consultants at the time of consultancy, generated by each consecutive culture result. Collected data included the timing of consultation in relation to the culture result for each consultancy continuation or changing antibiotic therapy and whether there had been any previous consultation before determination of a positive blood culture. Information on microbiological culture results, age, sex, department of stay, underlying diseases, antibiotic use, and infections during the hospital stay was colle...

To evaluate methicillin-resistant Staphylococcus aureus detection, we tested in vitro four selective agars and two enrichment broths apart and in combination. Tryptone soya broth with salt, aztreonam, and cefoxitin appeared to be the most sensitive medium. This broth was superior to a phenol red mannitol broth with aztreonam and ceftizoxime.Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of morbidity and mortality worldwide. Detection of MRSA in screening samples is an important part of the control of MRSA, but due to annex flora, the low level of MRSA often found in screening samples, and the emergence of heteroresistant MRSA strains (4,8,9,12), this is laborious and often difficult. Further cocolonization with other staphylococcal species might lead to false-positive results, especially when using PCR-based methods (1). The use of an enrichment broth for MRSA detection is known to increase sensitivity but requires an extra day of incubation (13,14,16). Several brands of chromogenic agars supplemented with antibiotics have recently become available and have performed well by direct inoculation and 24-h incubation (2,13,14). However, studies that compare chromogenic agars show conflicting results (2). Most of the published evaluations were performed on samples with the traditional "health care-associated" MRSA strains and with no information on the clonal diversity of the investigated isolates. Clonal differences are known to be one of the reasons for discrepancies when MRSA selective media are studied (7).We evaluated the performance in vitro of four different selective agars and two enrichment broths, separately and in combination, using low inocula of MRSA isolates.Ninety-six well-characterized MRSA strains, representing 13 clonal complexes and all six main SCCmec types (6), including low-level-resistant isolates; 52 methicillin-sensitive Staphylococcus aureus (MSSA) isolates; and 49 methicillin-resistant coagulase-negative staphylococcus (MRCNS) isolates were tested. The agars tested were ChromID MRSA (bioMérieux, Marcy l'Etoile, France); MRSA Select (Bio-Rad, Hercules, CA); a chromagar plate manufactured at Statens Serum Institut (SSI) on license from CHROMagar, Paris, France (MRSA SSI); a mannitol salt agar with 4 mg/liter cefoxitin (MSA); and a 5% blood agar (BA). Two enrichment broths were tested, (i) phenol red mannitol broth with 0.5% salt, 75 mg/liter aztreonam, and 5 mg/liter ceftizoxime (PHMB) (16) and (ii) tryptone soya broth with 2.5% salt, 20 mg/liter aztreonam, and 3.5 mg/liter cefoxitin (TSB) from SSI. The concentrations included in TSB were based on pilot investigations (data not shown). These tests showed that 3 mg/liter cefoxitin allowed breakthrough growth of MSSA and that 4 mg/liter cefoxitin and Ͼ20 mg/liter aztreonam resulted in loss of sensitivity. Approximately 20 CFU (20 l of 10 3 CFU/ml vortexed suspension in 0.9% NaCl) of each strain taken from the same suspension, made from fresh overnight-incubated isolates, were inoculated directly onto agar plates and into th...

Rapid identification of bacteria and prompt acquisition of susceptibility results are valuable for patient care. The objective of the present study was to determine the accuracy of direct inoculation of Vitek 2 cards from positive BACTEC cultures compared to inoculation of the cards from subculture plates. Positive BACTEC cultures sampled between March 2001 and June 2002 were included. The results of direct inoculation were compared with the results of inoculation of Vitek 2 cards from subcultures. Of 161 gram-negative bacilli, 129 (80%) were correctly identified by direct inoculation compared to 145 of 161 (90%) by subculture. Susceptibility testing was performed on 2,862 antibiotic-isolate combinations. The essential agreement was 98.7%. The number of very major, major, and minor errors was 1 (0.2% of resistant strains), 1 (0.04% of susceptible strains), and 68, respectively. Direct identification of Staphylococcus spp. was not performed, but antimicrobial susceptibility was tested using 6,042 antibiotic-isolate combinations. The essential agreement was 95.2%. The number of very major, major, and minor errors was 73 (4.5% of resistant strains), 32 (0.8% of susceptible strains), and 106, respectively. Eighty-four percent of the very major errors occurred with trimethoprim-sulfamethoxazole. The results show that direct inoculation of Vitek cards is valuable as a rapid routine method for identification and susceptibility testing of gram-negative bacilli. For Staphylococcus spp., the susceptibility results obtained after direct inoculation of Vitek 2 cards are also acceptable except for those obtained with trimethoprim-sulfamethoxazole. Susceptibility results for this antibiotic, if obtained using direct inoculation, should not be reported to the clinician.