David A. Bankert

Identification of Streptococcus pneumoniae Revisited

ABSTRACT The sensitivities and specificities of several different diagnostic assays for Streptococcus pneumoniae were assessed using 99 clinical isolates of S. pneumoniae and 101 viridans streptococci and were as follows: Pneumoslide, 99 and 87%, respectively; Directigen, 100 and 85%, respectively; Phadebact, 100 and 98%, respectively; deoxycholate drop test, 99 and 98%, respectively; deoxycholate tube test, 100 and 99%, respectively; optochin, 99 and 98%, respectively; and Gram Positive Identification Card, 90 and 96%, respectively. Identification of clinical isolates ofS. pneumoniae should be confirmed using one or more diagnostic assays with well-documented high (e.g., ≥95%) sensitivities and specificities.

Application of the Sherlock Mycobacteria Identification System Using High-Performance Liquid Chromatography in a Clinical Laboratory

ABSTRACT There is a growing need for a more accurate, rapid, and cost-effective alternative to conventional tests for identification of clinical isolates of Mycobacterium species. Therefore, the ability of the Sherlock Mycobacteria Identification System (SMIS; MIDI, Inc.) using computerized software and a Hewlett-Packard series 1100 high-performance liquid chromatograph to identify mycobacteria was compared to identification using phenotypic characteristics, biochemical tests, probes (Gen-Probe, Inc.), gas-liquid chromatography, and, when necessary, PCR-restriction enzyme analysis of the 65-kDa heat shock protein gene and 16S rRNA gene sequencing. Culture, harvesting, saponification, extraction, derivatization, and chromatography were performed following MIDIs instructions. Of 370 isolates and stock cultures tested, 327 (88%) were given species names by the SMIS. SMIS software correctly identified 279 of the isolates (75% of the total number of isolates and 85% of the named isolates). The overall predictive value of accuracy (correct calls divided by total calls of a species) for SMIS species identification was 85%, ranging from only 27% (3 of 11) for M. asiaticum to 100% for species or groups including M. malmoense (8 of 8), M. nonchromogenicum (11 of 11), and the M. chelonae-abscessus complex (21 of 21). By determining relative peak height ratios (RPHRs) and relative retention times (RRTs) of selected mycolic acid peaks, as well as phenotypic properties, all 48 SMIS-misidentified isolates and 39 (91%) of the 43 unidentified isolates could be correctly identified. Material and labor costs per isolate were

Performance of an enzyme immunoassay test and anaerobic culture for detection of group A streptococci in a pediatric practice versus a hospital laboratory

10.94 for SMIS,

Frequency of low level bacteremia in infants from birth to two months of age.

26.58 for probes, and

Frequency of Low-Level Bacteremia in Children from Birth to Fifteen Years of Age

42.31 for biochemical identification. The SMIS, combined with knowledge of RPHRs, RRTs, and phenotypic characteristics, offers a rapid, reasonably accurate, cost-effective alternative to more traditional methods of mycobacterial species identification.

Clinical comparison of isolator and thiol broth with ESP aerobic and anaerobic bottles for recovery of pathogens from blood.

The ability of pediatricians and hospital laboratory personnel to detect group A streptococci in patients with suspected streptococcal pharyngitis was evaluated using the TestPack Strep A and anaerobic culture. Duplicate throat specimens (for similar processing by both the pediatricians and laboratory technologists) were simultaneously collected on rayon-tipped swabs from patients with symptoms of pharyngitis. Each swab was first inoculated to a 5% sheep blood agar plate, then tested for group A streptococcus antigen using the TestPack Strep A according to the manufacturers instructions. Cultures were incubated anaerobically at 35 degrees C for 2 nights unless positive after 1 night. Group A streptococci were identified using specific antisera. Pediatric office or laboratory cultures from 112 (31.3%) of the 358 patients contained group A streptococci. Of the patients with positive cultures, 96 (85.7%) and 107 (95.5%) were detected by the pediatricians and laboratory, respectively. Respective findings with the TestPack Strep A by the pediatricians and laboratory were sensitivity 68.8% and 74.8%, specificity 94.3% and 95.6%, predictive value of a positive result 81.5% and 87.9%, and predictive value of a negative result 89.2% and 89.9%. Anaerobic culture was significantly more sensitive than the TestPack Strep A for detection of group A streptococci by both the pediatricians (P less than 0.005) and laboratory personnel (P less than 0.05).