The effects of volume of blood, number of consecutive cultures, and incubation time on pathogen recovery were evaluated for 37,568 blood cultures tested with the automated BACTEC 9240 instrument (Becton Dickinson Diagnostic Instrument Systems) at a tertiary care center over the period of 12 June 1996 through 12 October 1997. When the results for this study were compared with previous data published for manual broth-based blood culture systems and patient samples obtained in the 1970s and 1980s, the following were found: (1) the percentage increase in pathogen recovery per milliliter of blood is less, (2) more consecutive blood culture sets over a 24-h period are required to detect bloodstream pathogens, and (3) a shorter duration of incubation is required to diagnose bloodstream infections. Guidelines developed in the 1970s and 1980s for processing and culturing blood may require revision.

Lactobacilli are part of normal gastrointestinal and genitourinary flora but are an uncommon cause of bacteremia. We reviewed the cases of 45 patients with clinically significant lactobacillus bacteremia occurring over 15 years. Underlying conditions were common, including cancer (40%), recent surgery (38%), and diabetes mellitus (27%). Twenty-two patients were in the intensive care unit at the time of onset of lactobacillus bacteremia. Eleven of the 45 patients were receiving immunosuppressive therapy, 11 were receiving total parenteral nutrition, and 23 had received antibiotics without activity against Lactobacillus prior to the occurrence of bacteremia. Bacteremia was polymicrobial in 27 patients and developed during hospitalization in 39. Thirty-one patients died, but only one death was attributable to lactobacillus bacteremia. Lactobacilli are relatively avirulent pathogens that produce bacteremia in patients with serious underlying illnesses, many of whom have received prior antibiotic therapy that may select out for the organism. While rarely fatal in itself, lactobacillus bacteremia identifies patients with serious and rapidly fatal illness.The lactobacilli are anaerobic or facultatively anaerobic who had lactobacilli isolated from one or more blood cultures gram-positive rods that are part of the normal flora of the were identified. Six patients were excluded because the organgastrointestinal and genitourinary tracts [1, 2]. Lactobacillus is ism was considered a contaminant. These patients received no rarely a human pathogen but has been reported to cause dental therapy and did well. 1983, when it was replaced by the BACTEC 660 system, each Few studies have examined the epidemiology and long-term involving the inoculation of 3 -5 mL of blood into aerobic and outcome of lactobacillus bloodstream infection (table 1). The anaerobic bottles. In 1986 this system was replaced by the 10-largest review, by Antony et al. [18], described only 12 patients mL Isolator system (Wampole Laboratories, Cranbury, NJ) and and discussed the prior literature. Other recent studies have a bottle containing tryptic soy broth (Difco Laboratories, Dereported lactobacillus bacteremia in small series of liver transtroit). Beginning in 1992 the tryptic soy broth bottle was replant recipients and patients with AIDS [16, 19]. We recently placed successively by the ESP Aerobic 80A bottle (Difco encountered several patients with clinically significant lactobaLaboratories) and the BACTEC Plus Aerobic/F bottle (Becton cillus bacteremia at the Cleveland Clinic Foundation (CleveDickinson). land, OH), which prompted us to retrospectively review our Lactobacilli were identified presumptively by standard methinstitutional experience with regard to the clinical presentation, ods, including a characteristic gram-stain morphology after epidemiology, and outcome of this infection.growth on agar media incubated aerobically and anaerobically, a negative catalase reaction, and the absence of hydrogen sulfide formation in a triple sugar agar slant. A...

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The minimal inhibitory concentrations of 601 clinical isolates of anaerobic bacteria to 10 different antimicrobial agents were determined by an agar-dilution technique. Nearly all strains were resistant to kanamycin and gentamicin, although moderate activity to both drugs was noted with Fusobacterium sp., anaerobic cocci, some strains of Bacteroides melaninogenicus, and nonsporeforming gram-positive bacilli. Chloramphenicol at 12.5 ,ug/ml inhibited all but three of the strains tested. Tetracycline at 6.25 ,ug/ml had high activity against all groups tested, with the exception that only 39% of strains of Bacteroidesfragilis were inhibited at this concentration. Excluding certain species of Bacteroides, the majority of anaerobes were inhibited by penicillin at 3.1 ,ug/ml or less and by cephalothin at 12.5 ,ug/ml or less. Lincomycin at 6.2 ,ug/ml or less was active against nearly all strains. Erythromycin at a concentration of 3.1 ,ug/ml was active against B. fragilis; however, erythromycin was less active against the other groups. Most of the minimal inhibitory concentrations of lincomycin exceeded those of clindamycin by fourfold; Rifampin inhibited virtually all strains at 3.1 /Ag/ml.

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Seven laboratories participated in a collaborative study to

In a controlled evaluation of 6,010 blood cultures, the yield of clinically significant microorganisms was greater from a lysis-centrifugation system (Isolator, Du Pont Co.) than from a nonvented vacuum bottle containing tryptic soy broth with sodium polyanetholesulfonate and CO2 and a vented bottle containing biphasic brain heart infusion medium with sodium polyanetholesulfonate. The Isolator significantly increased the frequency of isolation of Staphylococcus aureus and Candida spp. and significantly decreased the time required for the detection of S. aureus, Pseudomonas aeruginosa, and Candida spp.; however, anaerobic bacteria were recovered significantly more frequently from nonvented bottles with tryptic soy broth, and pneumococci were recovered significantly more frequently from both bottle systems. Contamination of cultures was significantly greater with the Isolator system than with either bottle system. Regardless of the number of blood cultures obtained per septic episode, the Isolator detected microbiologically proven bacteremia or fungemia in a significantly greater number of patients and significantly decreased the time required for detection.