Multicenter evaluation of the BACTEC MGIT 960 system for recovery of mycobacteria.

We evaluated the BACTEC MGIT 960 system, which is a fully automated, noninvasive system for the growth and detection of mycobacteria with a capacity to incubate and continuously monitor 960 7-ml culture tubes. We studied 3,330 specimens, 2,210 respiratory and 1,120 nonrespiratory specimens, collected from 2,346 patients treated at six sites. Processed specimens were inoculated into the BACTEC MGIT 960 and BACTEC 460 TB systems, as well as onto Lowenstein-Jensen slants and Middlebrook 7H11/7H11 selective plates. From all culture systems, a total of 362 isolates of mycobacteria were recovered; these were recovered from 353 specimens collected from 247 patients. The greatest number of isolates of mycobacteria (289, or 80% of the 362 isolates) was recovered with the BACTEC MGIT 960, followed by the BACTEC 460 TB (271, or 75%) and solid media (250, or 69%). From all culture systems a total of 132 isolates of Mycobacterium tuberculosis complex were recovered. The greatest number of isolates of M. tuberculosis complex was recovered when liquid medium was combined with conventional solid media; the number recovered with BACTEC 460 TB plus solid media was 128 (97%), that recovered with BACTEC MGIT 960 plus solid media was 121 (92%), that recovered with BACTEC 460 TB was 119 (90%) and that recovered with all solid media combined was 105 (79%). The recovery with BACTEC MGIT 960 alone was 102 (77%). The mean times to detection (TTD) for M. tuberculosis complex were 14.4 days for BACTEC MGIT, 15.2 days for BACTEC 460 TB, and 24.1 days for solid media. The numbers of isolates of Mycobacterium avium complex (MAC) recovered were 172 (100%) for all systems, 147 (85%) for BACTEC MGIT 960, 123 (72%) for BACTEC 460 TB, and 106 (62%) for all solid media combined. The TTD for MAC in each system were 10.0 days for BACTEC MGIT 960, 10.4 days for BACTEC 460 TB, and 25.9 days for solid media. Breakthrough contamination rates (percentages of isolates) for each of the systems were 8.1% for BACTEC MGIT 960, 4.9% for BACTEC 460 TB, and 21.1% for all solid media combined.

Epidemiology of invasive pneumococcal disease in southern California: implications for the design and conduct of a pneumococcal conjugate vaccine efficacy trial.

Population-based prospective surveillance of invasive pneumococcal disease was done in Southern California from 31 March 1992 to 1 April 1995; 814 cases were identified, for an incidence of 12.5/100,000 persons/year. The incidence among persons < or = 2, < or = 5, and > or = 65 years of age was 145, 72, and 32/100,000, respectively. More than 95% of cases included bacteremia; incidence of meningitis was 0.8/100,000. Among children < or = 2 years of age, 79% of isolates were obtained in the outpatient setting, compared with 16% of isolates among persons > or = 15 years of age. Eighty percent of isolates were serotypes included in heptavalent pneumococcal conjugate vaccines currently being evaluated. Children < or = 2 years of age were at highest risk of having an isolate resistant to penicillin. Among resistant isolates, high-level resistance increased from 4% to 21% over a 3-year period. Prospective epidemiologic data are needed to perform a protective efficacy trail of pneumococcal conjugate vaccines in infants, among whom most invasive pneumococcal disease is vaccine-preventable.

Analysis of vancomycin time-kill studies with Staphylococcus species by using a curve stripping program to describe the relationship between concentration and pharmacodynamic response.

Mono- and biexponential killing curves for vancomycin over a 2- to 50-micrograms/ml concentration range were generated for 11 Staphylococcus aureus isolates and 12 coagulase-negative Staphylococcus species in the logarithmic phase of growth. Nonlinear least-squares regression of the initial growth rate and disappearance were not significantly different for lower or higher concentrations of vancomycin in broth.

Disseminated Nocardia asteroides diagnosed by blood culture in a patient with disseminated histoplasmosis.

We describe herein a provocative case involving an immunosuppressed patient with disseminated Histoplasma capsulatum and also disseminated Nocardia asteroides, which was documented by multiple routine blood culture samples. Nocardia asteroides was isolated from 15 routine blood cultures using the nonradiometric blood culture system (Bactec NR-660, Becton Dickinson, Towson, Md). Several different species of the genus Nocardia proved to thrive in blood culture bottles (Bactec) when experimental inoculations were performed. The paucity of reports in the literature of disseminated nocardiosis with positive blood cultures has led us to consider cause for the apparent poor recovery of these organisms from blood culture media. We suggest that the media (Bactec) can successfully support growth of Nocardia species and that other variables, such as incubation times and subculture, should be considered to optimize isolation of this pathogen in blood culture systems.

Mycobacterial cross contamination during radiometric culturing.

Pseudobacteremias in blood cultures performed on the BACTEC radiometric blood culture system have been reported. We report three cases of cross contamination with Mycobacterium avium that occurred when mycobacteria were cultured with the BACTEC 460 TB system. Malfunction of the needle sterilization heating block was demonstrated.

Identification of the dietary lectin, wheat germ agglutinin, in human intestinal contents.

Plant lectins are known to have potent biological actions of normal and malignant cells. High concentrations of these lectins are present in many types of high residue diets. The specific binding of wheat germ agglutinin, a dietary plant lectin, to N-acetylglucosamine was used as the basis for purification of this lectin by biospecific chitin affinity chromatography. Subsequently, methods were developed for the extraction, purification, and identification of wheat germ agglutinin from fecal samples. Biologically intact wheat germ agglutinin was detected in ileostomy effluent and fecal collections from human subjects consuming a diet containing wheat germ. These studies demonstrate that wheat germ agglutinin can traverse the human small intestine intact. It is feasible that orally ingested wheat germ agglutinin and other plant lectins which interact with a wide variety of cell membranes may alter intestinal epithelial or bacterial cell function in the human bowel.