Multicenter evaluation of mycobacteria growth indicator tube (MGIT) compared with the BACTEC radiometric method, BBL biphasic growth medium and Löwenstein—Jensen medium

ObjectiveTo evaluate the new BBL mycobacteria growth indicator tube (MGIT) in comparison with other media.MethodsMGIT was evaluated in 10 Italian centers on 433 clinical samples, mainly of respiratory origin and mainly smear positive, in comparison with Löwenstein—Jensen and with one or more other methods represented, according to participating centers, by the BACTEC radiometric method or by the biphasic BBL Septi-Chek AFB system. While MGIT and Löwenstein—Jensen were used for all the samples, 285 of them were also inoculated in BACTEC vials and 274 in biphasic bottles. Of these samples, 132 were investigated with all the four methods.ResultsAlthough less rapid and sensitive than the radiometric method, the results of MGIT were equal when compared with the other two media with respect to overall isolation yield; furthermore, it allowed the detection of growth in significantly shorter times.ConclusionsThe results of this study indicate the value of MGIT for the detection of mycobacteria and, thanks to its extreme simplicity of use, its suitability for small and large laboratories. Its combined use with a solid medium can substantially improve the diagnosis of mycobacterial infection

Comparison of MB/BacT ALERT 3D System with Radiometric BACTEC System and Löwenstein-Jensen Medium for Recovery and Identification of Mycobacteria from Clinical Specimens: a Multicenter Study

The MB/BacT ALERT 3D System (MB/BacT) (Organon Teknika, Boxtel, The Netherlands) is a fully automated, nonradiometric system with a revised antibiotic supplement kit designed for the recovery of mycobacteria from clinical specimens. In a multicenter study, the recovery rate of acid-fast bacilli (AFB) and the mean time to their detection from clinical specimens was determined by using the MB/BacT system. Data were compared to those assessed by the radiometric BACTEC 460 system (B460) and by culture on Löwenstein-Jensen (L-J) solid medium. A total of 2,859 respiratory and extrapulmonary specimens were processed by the N-acetyl-l-cysteine (NALC)-NaOH method using two different concentrations of sodium hydroxide; 1.5% was adopted in study design A (1,766 specimens), and 1.0% was used in study design B (1,093 specimens). The contamination rates for MB/BacT were 4.6% (study design A) and 7.1% (study design B). One hundred seventy-nine mycobacterial isolates were detected by study design A, with 148 Mycobacterium tuberculosis complex (MTB) isolates and 31 nontuberculous mycobacteria (NTM) isolates. Overall recovery rates were 78.8% for MB/BacT (P = 0.0049), 64.2% for L-J (P < 0.0001), and 87.1% for B460, whereas they were 84.5, 70.9, and 91.2%, respectively, for MTB alone. A total of 125 mycobacteria were detected by study design B, with 46 MTB and 79 NTM. Overall recovery rates by the individual systems were 57.6% (P = 0.0002), 56.8% (P = 0.0001), and 80% for MB/BacT, L-J, and B460, respectively, whereas the rates were 91.3, 78.3, and 97.8% for MTB alone. By study design A, the mean times to detection of smear-positive MTB, smear-negative MTB, and NTM were 11.5, 19.9, and 19.6 days, respectively, with the MB/BacT; 8.3, 16.8, and 16.6 days, respectively, with the B460; and 20.6, 32.1, and 27.8 days, respectively, with L-J medium. By study design B, the mean times were 15.1, 26.7, and 26 days with the MB/BacT; 11.7, 21.3, and 24.8 days with the B460; and 20.4, 28.7, and 28.4 days with L-J medium. Identification was attempted by probing (Accuprobe) MB/BacT-positive bottles within the first working day following instrument positive flag. Results were compared to those obtained in the B460 positive vials by the p-nitro-α-acetylamino-β-hydroxypropiophenone (NAP) test (study design A) or by the Accuprobe assay (study design B). About 90% of MTB and 100% of NTM could be identified, showing turnaround times closely related to those obtained by combining B460 and the NAP test or the Accuprobe assay. In conclusion, even though recovery rates were shown to be lower than B460, especially for NTM, and contaminants were somewhat higher, MB/BacT represents a valuable alternative to the radiometric system, especially in those laboratories where disposal of radioactive waste is restricted. Finally, when AFB are cultured in nonradiometric liquid media, our data (detection times and bacterial overgrowth rates) suggest that decontamination with 1.5% NaOH may be more suitable than the standard NALC-NaOH

Reliability of the chemiluminescence Liaison Treponema Screen test for the screening of anti-Treponema antibodies

A chemiluminescent test for anti treponemal total antibodies, Liaison Treponema Screen test (LTS), was compared with Treponema Pallidum Particle Agglutination assay (TPPA) against 1022 regular blood donors and 2627 in-and-outpatients attending the laboratories of five hospitals. All positive and doubtful tests were confirmed by Western Blot (WB) and we have discussed the criteria of WB positivity. The results for blood donors were: nonreactive 1022 TPPA and 1021 LTS and doubtful 1 LTS (WB negative) with a concordance of 99.9%.The mean and median index values of the LTS tests (0.175 and 0.15 respectively) were much lower than the doubtful and positive cut-off index values (0.9 and 1.1 respectively).The results for the 2627 patients were: 2423 (92.2%) LTS and TPPA non reactive; 191 (7.3%) LTS and TPPA reactive; 13 (0.5%) LTS and TPPA discordant. Of the 13 patients with discordant tests (1 TPPA reactive vs. LTS nonreactive and 12 LTS reactive or doubtful vs. TPPA nonreactive) 1 was true positive (LTS reactive and TPPA nonreactive), 10 true negative (LTS reactive/doubtful and TPPA nonreactive) and 2 not verifiable. The sensitivity and specificity of LTS were 99.5% and 99.6% respectively; the sensitivity and specificity of TPPA were 99.0% and 100% respectively. In conclusion, LTS and TPPA are similar in sensitivity and specificity, but an automated analyzer as Liaison is more useful than TPPA in laboratories with high workload in syphilis screening

Alkhurma Hemorrhagic Fever in Travelers Returning from Egypt, 2010

Two travelers returning to Italy from southern Egypt were hospitalized with a fever of unknown origin. Test results showed infection with Alkhurma virus. The geographic distribution of this virus could be broader than previously thought

Multicenter evaluation of mycobacteria growth indicator tube (MGIT) compared with the BACTEC radiometric method, BBL biphasic growth medium and Löwenstein—Jensen medium

ObjectiveTo evaluate the new BBL mycobacteria growth indicator tube (MGIT) in comparison with other media.MethodsMGIT was evaluated in 10 Italian centers on 433 clinical samples, mainly of respiratory origin and mainly smear positive, in comparison with Löwenstein—Jensen and with one or more other methods represented, according to participating centers, by the BACTEC radiometric method or by the biphasic BBL Septi-Chek AFB system. While MGIT and Löwenstein—Jensen were used for all the samples, 285 of them were also inoculated in BACTEC vials and 274 in biphasic bottles. Of these samples, 132 were investigated with all the four methods.ResultsAlthough less rapid and sensitive than the radiometric method, the results of MGIT were equal when compared with the other two media with respect to overall isolation yield; furthermore, it allowed the detection of growth in significantly shorter times.ConclusionsThe results of this study indicate the value of MGIT for the detection of mycobacteria and, thanks to its extreme simplicity of use, its suitability for small and large laboratories. Its combined use with a solid medium can substantially improve the diagnosis of mycobacterial infection

Performance Assessment of New Multiplex Probe Assay for Identification of Mycobacteria

A new DNA probe assay (INNO LiPA Mycobacteria; Innogenetics, Ghent, Belgium) for the simultaneous identification, by means of reverse hybridization and line-probe technology, of Mycobacterium tuberculosis complex, Mycobacterium kansasii, Mycobacterium xenopi, Mycobacterium gordonae, the species of the Mycobacterium avium complex (MAC), Mycobacterium scrofulaceum, and Mycobacterium chelonae was evaluated on a panel of 238 strains including, besides representatives of all the taxa identifiable by the system, a number of other mycobacteria, some of which are known to be problematic with the only other commercial DNA probe system (AccuProbe; Gen-Probe, San Diego, Calif.), and two nocardiae. The new kit, which includes a control probe reacting with the whole genus Mycobacterium, correctly identified 99.6% of the strains tested; the one discrepancy, which remained unresolved, concerned an isolate identified as MAC intermediate by INNO LiPA Mycobacteria and as Mycobacterium intracellulare by AccuProbe. In five cases, because of an imperfect checking of hybridization temperature, a very slight, nonspecific, line was visible which was no longer evident when the test was repeated. Two strains whose DNA failed amplification at the first attempt were regularly identified when the test was repeated. Interestingly, the novel kit dodged all the pitfalls presented by the strains giving anomalous reactions with AccuProbe. A unique feature of INNO LiPA Mycobacteria is its ability to recognize different subgroups within the species M. kansasii and M. chelonae, while the declared overlapping reactivity of probe 4 with some M. kansasii and Mycobacterium gastri organisms and of probe 9 with MAC, Mycobacterium haemophilum, and Mycobacterium malmoense, may furnish a useful aid for their identification. The turnaround time of the method is approximately 6 h, including a preliminary PCR amplification