Evaluation of a simplified IS6110 PCR for the rapid diagnosis of Mycobacterium tuberculosis in an area with high tuberculosis incidence.

PURPOSE: To assess the diagnostic yield of a simplified IS6110-PCR in an area with high tuberculosis incidence. METHODS: Pulmonary (218) and extrapulmonary (121) samples were collected from 236 patients including smearpositive leprosy patients. All samples were processed to detect acidfast bacilli by microscopy, culture on solid media and PCR. To remove PCR inhibitors, three washing steps of the decontaminated pellet were included before mycobacterial cell lysis by heat treatment. No detergents, enzymes, or chelating agents were used. From the 339 samples, 34 were selected basing on their large volume and were tested by the commercial kit GenoType Mycobacteria Direct (GTMD) (VER 4, Hain Lifescience, Germany) in addition to the tests cited above. RESULTS: The overall sensitivity and specificity of PCR were 93.8 and 98.6% for pulmonary samples, 63.6 and 100% for extrapulmonary samples, respectively. The assay detected MTC in 94.2% of smear positive samples with a positive predictive value of 100%. No inhibition was found among seven samples that were PCR negative but bacteriological confirmed as containing Mycobacterium tuberculosis. No false positive result occurred with samples from leprosy patients. The sensitivities for PCR and GTMD were 81.8 and 75%, respectively. CONCLUSION: PCR could efficiently complement conventional bacteriological tools for the rapid diagnosis of tuberculosis but cannot replace them.

Rapid detection of immunoglobulin G against Mycobacterium tuberculosis antigens by two commercial ELISA kits.

SETTING: Tunisia. OBJECTIVE: To assess the clinical usefulness of the commercial Pathozyme-Myco G (Myco G) and Pathozyme TB complex plus (Patho) enzyme-linked immunosorbent assay (ELISA) kits for the rapid diagnosis of active tuberculosis (TB) and to distinguish between active TB and non-TB pulmonary diseases in Tunisian patients. DESIGN: Immunoglobulin G mediated humoral immune response against mycobacterial antigens (38 kDa and lipoarabinomannan, Myco G; 16 and 38 kDa, Patho) was evaluated in a group of active TB patients (128 smear-positive pulmonary and 33 extra-pulmonary samples) and in a control group (107 patients with non-tuberculous lung disease and two with leprosy). Active TB cases were confirmed by Mycobacterium tuberculosis culture from clinical samples. RESULTS: The sensitivity of the Myco G test was 71% in active TB (pulmonary and extra-pulmonary), while the specificity was 100%. The Patho test showed a sensitivity of 43.5% with a specificity of 96.3%. A combination of both tests showed a sensitivity of 81% and a specificity of 96.3%. CONCLUSIONS: Both ELISA tests were simple and easy to perform. Their combined use led to an increase in the diagnostic accuracy of active TB and its discrimination from non-TB pulmonary diseases. They could therefore be used as screening tools in poorly equipped laboratories in TB-endemic regions.

A three-year surveillance of nosocomial infections by methicillin-resistant Staphylococcus haemolyticus in newborns reveals the disinfectant as a possible reservoir.

OBJECTIVE: Study of the clonality of methicillin-resistant Staphylococcus haemolyticus responsible of epidemic infections in a neonatal intensive care unit. PATIENTS AND METHODS: Methicillin-resistant Staphylococcus haemolyticus isolates were collected during the period from March 2004 to November 2006, from newborns, the clean hands of nurses and from disinfectant bottles used in the unit. Molecular typing by pulsed-field gel electrophoresis (PFGE) was achieved for all isolates. RESULTS: Forty-six isolates of S. haemolyticus resistant to methicillin were collected from 42 newborns, the hand of two nurses and from two disinfectant bottles used in the unit. PFGE analysis revealed five types (A, B, C, D and E) among newborns isolates. Types A and B were predominant. Nurses' isolates revealed PFGE types similar to types A and B. Disinfectant isolates were of type B. qacA/B PCR analysis revealed that the majority of type B isolates contain the disinfectant resistance gene qacA/B. No isolate of type A possessed this gene. CONCLUSION: These results suggest that MRSH neonatal infections are caused by a limited number of clones. Clone B was able to survive in disinfectant bottles and to conserve its ability to infect newborns. We therefore conclude that the disinfectant can serve as a reservoir for MRSH and point out the need to control all disinfectants used in a neonatal intensive care unit.

Clonality of clinical methicillin-resistant Staphylococcus epidermidis isolates in a neonatal intensive care unit.

OBJECTIVE: Study of the clonality of methicillin-resistant Staphylococcus epidermidis responsible of epidemic infections in a neonatal intensive care unit. PATIENTS AND METHODS: All S. epidermidis isolates (mecA+) were collected during the epidemic period (December 2003-September 2004) from different pathological products of newborns. Isolates were characterized by genotyping in pulsed-field gel electrophoresis and by electrophoretic profiles obtained by PCR-based analysis of inter-IS256 spacer polymorphisms. RESULTS: Twenty methicillin-resistant S. epidermidis isolates were collected from newborns during the epidemic period and represented 41.6% of the total isolates of S. epidermidis, which is the first Staphylococcus species isolated from the unit. These isolates were collected from blood cultures (80%), vascular catheters (5%), pus (10%), and intra-tracheal tube (5%). Six genotypic profiles were individualized: type A, type B, type C, type D, type E, and type F, with clear dominance of type A. Five different PCR patterns were found with poor correlation to genotypes defined by PFGE. CONCLUSION: Neonatal nosocomial outbreak of methicillin-resistant S. epidermidis was caused by multiple clones of this species with predominance of one epidemic and multiresistant clone. This clone may be transmitted between babies and was able to persist in the unit. PCR IS 256 proved to be less discriminative than PFGE for typing MRSE.