The reliability of the ESP Culture System II (ESP II; Difco Laboratories, Detroit, Mich.), a continuously monitoring mycobacterial culture system, was evaluated by comparing its performance with the BACTEC TB 460 (BACTEC TB) and Middlebrook 7H11/7H11 selective agar systems. A total of 2,283 specimens of all types (70.7% were respiratory specimens) were cultured; 149 (6.5%) yielded mycobacteria. The most common species recovered were Mycobacterium avium complex (MAC, 73 isolates) and Mycobacterium tuberculosis complex (MTBC, 53 isolates). The recovery rates by individual system were 87, 81, and 65% for ESP II, BACTEC TB, and Middlebrook agar, respectively, for all mycobacteria; the recovery rates were 89, 92, and 89%, respectively, for MTBC. For liquid plus solid medium system combinations, recovery rates for all mycobacteria and for MTBC, respectively, were 91 and 94% for ESP II plus Middlebrook agar and 85 and 96% for BACTEC TB plus Middlebrook agar. The difference between the recovery rates of all mycobacteria by ESP II and by BACTEC TB was not significant, whereas for the individual species, the only significant difference was recovery of more isolates of MAC by ESP II. For those isolates recovered in the individual systems, mean times to detection of all mycobacteria, MTBC, and MAC, respectively, were 13.1, 15.5, and 10.9 days for ESP II; 14.4, 16.6, and 12.1 days for BACTEC TB; and 17.8, 18.3, and 18.8 days for Middlebrook agar. ESP II is a reliable, nonradiometric, less labor-intensive alternative to BACTEC TB for growth and detection of mycobacteria, but as with other liquid culture methods, ESP II should be used in combination with a solid medium, not as a stand-alone system.

The performance of a fully automated, random access, enhanced chemiluminescence immunoassay (Ortho/ ECi) for the detection of antibody to hepatitis C virus (HCV) (anti-HCV), HBsAg, and antibody to HBsAg (anti-HBsAg), in human serum was compared to a Abbott second-generation enzyme immunoassay (EIA 2.0). The Ortho/ECi assays employ an immunometric technique with enhanced chemiluminescence for optimal assay performance. With regard to the study of clinical laboratory performance, six groups of sera prescreened with Abbott EIAs were assayed: anti-HCV-negative samples (n ‫؍‬ 318), anti-HCV-positive samples (n ‫؍‬ 177), anti-HBsAg-negative samples (n ‫؍‬ 241), anti-HBsAg-positive samples (n ‫؍‬ 239), HBsAg-positive samples (n ‫؍‬ 158), and HBsAg-negative samples (n ‫؍‬ 312). Sera with discrepant results in the two serological assays were resolved by confirmatory tests. Sera with indeterminate results by one or more confirmatory tests were evaluated by reviewing medical records. The overall concordance between the Ortho/ECi assay and the Abbott EIA were 97.78, 93.54, and 97.66% for anti-HCV antibodies, anti-HBsAg antibodies, and HBsAg, respectively. After resolving the discrepancies, the specificities of the new assay for anti-HCV and anti-HBsAg antibodies and HBsAg were 98.1, 92.8, and 100%, respectively. The sensitivities of the new assay for anti-HCV, anti-HBsAg, and HBsAg were 100, 98.8, and 97.4%, respectively. In conclusion, The Ortho/ECi assays for diagnosis of HCV and hepatitis B virus (HBV) infections are highly specific and sensitive assays. The rapid turnaround time, random access, full automation, and high throughput make it an effective assay system for clinical laboratory diagnosis of HCV and HBV infections.The four immunoassays described here are associated with the diagnosis of hepatitis C and B virus (HCV and HBV, respectively) infections. HCV, an enveloped positive-stranded RNA virus of the Flaviviridae family, has been demonstrated to be the etiologic agent of 90% of chronic non-A, non-B hepatitis (2, 5, 10, 15). HCV infection is often asymptomatic; however, the vast majority of HCV-infected individuals (Ͼ85%) develop persistent chronic infection and chronic hepatitis (9,32,45,46). Diagnosis of HCV infection has serious implications, especially for the high-risk patients such as those undergoing hemodialysis (20,27,35). The presence of anti-HCV antibodies indicates that an individual may have been infected with HCV and/or may be capable of transmitting HCV infection while active infection is marked by the presence of HCV RNA detected by reverse transcriptase PCR (6,17,35,42). Detection of viremia is often required in certain cases of acute infection and/or immunodeficiency, where individuals may fail to produce antibodies specific for HCV (32, 39).The HCV genome consists of seven functional regions: the core, the envelope, including the E1 and E2 regions, and the nonstructural region, including NS2, NS3, NS4, and NS5 (31). The first commercially available HCV test was an enzymelinked immunosorbent a...

The reliability of the enhanced Amplified Mycobacterium Tuberculosis Direct Test (E-MTD; Gen-Probe, Inc., San Diego, Calif.) for rapid diagnosis of pulmonary tuberculosis (TB) was evaluated by testing 1,004 respiratory specimens from 489 Texas prison inmates. Results were compared to those of mycobacterial culture (BACTEC TB 460 and Middlebrook 7H11 biplates), smear for acid-fast bacilli (AFB; auramine O), and clinical course. After chart review, three patients (nine specimens) who were on antituberculosis therapy before the study began were excluded from final analysis. Of the remaining 995 specimens, 21 were AFB smear positive: 13 grew Mycobacterium tuberculosis complex (MTBC), 6 grew nontuberculous mycobacteria, and 2 (from two patients diagnosed with TB and started on therapy after the study began) were culture negative. Twenty-eight specimens (20 patients) were positive for MTBC by culture and E-MTD. Seven specimens (seven patients) were positive by culture alone; three were from patients who had other E-MTD-positive specimens, two were false-positive cultures, and two were false-negative E-MTD results. Eight specimens were positive by E-MTD only; four specimens (four patients) were false-positive E-MTD results, and four specimens were from two patients with earlier E-MTD-positive specimens that grew MTBC. Thus, there were 22 patients with TB (10 smear positive and 12 smear negative). The sensitivity and specificity of the AFB smear for diagnosis of TB, by patient, were 45.5 and 98.9%, respectively. After resolving discrepancies, these same values for E-MTD were 90.9 and 99.1% overall, 100 and 100% for the smear-positive patients, and 83.3 and 99.1% for the smear-negative patients. Excluding the one smear-negative patient whose E-MTD-negative, MTBC culture-positive specimen contained inhibitory substances, the sensitivity of E-MTD was 95.2% overall and 90.9% in smear-negative patients. The specificity and positive predictive value of E-MTD can be improved, without altering other performance characteristics, by modifying the equivocal zone recommended by the manufacturer. These data suggest that E-MTD is a reliable method for rapid diagnosis of pulmonary TB, irrespective of the AFB smear result. Guidelines for the most appropriate use of E-MTD with smear-negative patients are needed.

Objective.—To evaluate the performance of the BBL MGIT (Mycobacterial Growth Indicator Tube) AST SIRE system for the antimycobacterial susceptibility testing of Mycobacterium tuberculosis to isoniazid (at a concentration equivalent to the lower concentration used for testing by the method of proportion), rifampin, ethambutol, and streptomycin. Design.—Thirty-one clinical isolates and 30 challenge strains provided by the Centers for Disease Control and Prevention (CDC) were tested by MGIT AST SIRE using 2 methods of inoculum preparation, and results were compared with those of the method of proportion, which was considered the reference method. Clinical isolates for which the results of the 2 methods were discordant also were tested at 2 reference laboratories. Results.—Based on data from our site and the reference laboratories, agreement rates between initial MGIT AST SIRE results and the method of proportion for the clinical isolates with the inoculum prepared from a McFarland equivalent and from a positive MGIT tube, respectively, were 100% and 96.8% for isoniazid, 100% and 100% for rifampin, 96.8% and 100% for ethambutol, and 100% and 100% for streptomycin, excluding the isolate for which the discordant streptomycin result could not be resolved. For the 30 challenge isolates, agreement rates between MGIT AST SIRE and expected results and between method of proportion and expected results, respectively, were 96.7% and 93.3% for isoniazid, 93.3% and 100% for rifampin, 83.3% and 100% for ethambutol, and 93.3% and 100% for streptomycin. For the clinical isolates, the mean time to an MGIT AST SIRE result of susceptible was 6.15 ± 0.13 days (range, 5–8 days). For a result of resistant, the mean time overall was 5.00 ± 0.24 days (range, 3–8 days). Conclusion.—These data suggest that the MGIT AST SIRE system, using either method of inoculum preparation, is an acceptable alternative to the BACTEC 460 TB method of susceptibility testing of clinical isolates of M tuberculosis to isoniazid, rifampin, ethambutol, and streptomycin. Reasons for the lower agreement with the CDC challenge isolates should be investigated. Further evaluation of the MGIT AST SIRE system using a concentration of isoniazid equivalent to the higher concentration tested by the method of proportion would be useful, because the decision concerning use of this agent generally is based on the susceptibility test result at the higher concentration.