A national audit of the laboratory diagnosis of tuberculosis and other mycobacterial diseases within the United Kingdom.
(25/1137)
In order to audit United Kingdom laboratory diagnostic and reference services including novel molecular methods for tuberculosis, a questionnaire was sent to laboratories submitting specimens to the PHLS Mycobacterium Reference Unit (MRU) and regional centres and to the Scottish Mycobacteria Reference Laboratory (SMRL) in 1996-7. Nationally, 67.2% of laboratories responded. Most UK laboratories were fully or conditionally CPA accredited and take part in the NEQAS proficiency scheme. On average only 3.3% of primary samples submitted for mycobacterial diagnosis in 1995 produced a mycobacterial culture from approximately half as many patients (that is, a mean of 1488 specimens producing 49 isolates from 23 patients). Potentially over 380,000 specimens are processed for mycobacteria in the UK each year. The majority of laboratories use 4% NaOH +/- NALC for specimen decontamination. Culture on solid media was used by most laboratories and 62.9% also use liquid media. Most laboratories incubated cultures for eight weeks. Few laboratories use molecular diagnostic methods. Laboratories were most likely to use molecular methods for diagnosing tuberculous meningitis and for specimens from immunocompromised patients, although usage was strongly influenced by cost. Within England and Wales 43.9% (47/107) and 56% (61/109) of laboratories wanted a rapid service for rifampicin resistance detection in M tuberculosis from immunocompetent and immunocompromised patients, respectively. In regard to a tuberculous meningitis service, 80.5% (43/112) and 84.3% (102/121) of laboratories wanted this service for immunocompetent and immunocompromised patients, respectively. The quality of reference services was rated as "very good"/"good" by 85.6% of respondents nationally. Rapid molecular amplification diagnostic services were established at the PHLS MRU for rifampicin drug resistance detection nationally and for tuberculous meningitis at the MRU. (+info)
Disseminated infection with Mycobacterium genavense: a challenge to physicians and mycobacteriologists.
(26/1137)
In the present study we compared the clinical presentations of patients with a clinical diagnosis of AIDS and disseminated Mycobacterium genavense infection (n = 12) with those of patients with AIDS and disseminated M. avium complex (MAC) infection (n = 24). Abdominal pain was seen more frequently in the group of patients infected with M. genavense than in patients infected with MAC (P = 0. 003). Analysis of microbiological data revealed that stool specimens from patients infected with M. genavense were more often smear positive than stool specimens from patients infected with MAC (P = 0. 00002). However, M. genavense could be cultured on solid media from only 15.4% of the stool specimens, whereas MAC could be cultured from 71.4% of the specimens. Bone marrow and liver biopsy specimens yielded growth of M. genavense within a reasonably short time, allowing species identification by DNA technology. Microbiological data clearly demonstrated the importance of acidic liquid medium for primary culture, the avoidance of pretreatment and the use of additives in culture, and the necessity for prolonged incubation if M. genavense is suspected. Susceptibility testing showed that M. genavense is sensitive to rifamycins, fluoroquinolones, and macrolides, whereas it is resistant to isoniazid. Susceptibility to ethambutol and clofazimine could not be evaluated. The mean survival times of patients in the two groups were similar. (+info)
Macrophage apoptosis in mycobacterial infections.
(27/1137)
Mycobacterial diseases are a major public health concern. In the case of tuberculosis, the problem has been acerbated due to the emergence of drug-resistant strains of Mycobacterium tuberculosis, and Mycobacterium avium is the major opportunistic pathogen in HIV-1 infection in the United States. M. tuberculosis and M. avium replicate in human macrophages and induce apoptosis. Incubation of freshly added uninfected autologous macrophages with apoptotic M. avium-infected macrophages results in 90% inhibition of bacterial growth. Apoptosis also prevents the release of intracellular components and the spread of mycobacterial infection by sequestering the pathogens within apoptotic bodies. Consistent with the model that host cell apoptosis is a defense mechanism against mycobacteria is the finding that the virulent M. tuberculosis strain H37Rv induces substantially less macrophage apoptosis than the attenuated strain H37Ra. Evasion of apoptosis by this pathogen is achieved by enhanced release of sTNFR2 by H37Rv-infected macrophages and subsequent formation of inactive TNF-alpha-TNFR2 complexes. These observations contribute to the hypothesis that apoptosis of the host macrophage is an important defense mechanism in mycobacterial infections, which prevents the spread of the infection. (+info)
Nontuberculous mycobacterial infection of the head and neck in immunocompetent children: CT and MR findings.
(28/1137)
BACKGROUND AND PURPOSE: Infections caused by nontuberculous mycobacteria (NTM) commonly manifest as cervicofacial adenitis in otherwise healthy children. The aim of this study was to characterize the imaging findings of NTM infection of the head and neck in immunocompetent children. METHODS: The medical records and imaging examinations (CT in 10, MR in two) were reviewed in 12 immunocompetent children with NTM infection of the head and neck. RESULTS: The usual presentation (n = 9) was of an enlarging, non-tender mass with violaceous skin discoloration, unresponsive to conventional antibiotics. The duration of symptoms was 6 days to 5 months. Imaging revealed asymmetric adenopathy with contiguous low-density ring-enhancing masses in all patients. There was cutaneous extension in 10 patients. Inflammatory stranding of the subcutaneous fat was minimal (n = 9) or absent (n = 2) in 11 patients. The masses involved the submandibular space (n = 3), the parotid space (n = 2), the cheek (n = 1), the anterior triangle of the neck (n = 2), the submandibular and parotid spaces (n = 2), the parotid space and neck (n = 1), and the neck and retropharyngeal space (n = 1). Surgical management included incision and drainage only (n = 2), incision and drainage with curettage (n = 2), excisional biopsy after incision and drainage (n = 1), excisional biopsy only (n = 5), superficial parotidectomy only (n = 1), and superficial parotidectomy with contralateral excisional biopsy (n = 1). All patients improved in response to surgery and long-term antimycobacterial antibiotics. CONCLUSION: NTM infection of the head and neck has a characteristic clinical presentation and imaging appearance. Recognition of this disease is important; appropriate treatment is excision and, in selected cases, antimycobacterial therapy. (+info)
Partial interferon-gamma receptor signaling chain deficiency in a patient with bacille Calmette-Guerin and Mycobacterium abscessus infection.
(29/1137)
Complete deficiency of either of the two human interferon (IFN)-gamma receptor components, the ligand-binding IFN-gammaR1 chain and the signaling IFN-gammaR2 chain, is invariably associated with early-onset infection caused by bacille Calmette-Guerin vaccines and/or environmental nontuberculous mycobacteria, poor granuloma formation, and a fatal outcome in childhood. Partial IFN-gammaR1 deficiency is associated with a milder histopathologic and clinical phenotype. Cells from a 20-year-old healthy person with a history of curable infections due to bacille Calmette-Guerin and Mycobacterium abscessus and mature granulomas in childhood were investigated. There was a homozygous nucleotide substitution in IFNGR2, causing an amino acid substitution in the extracellular region of the encoded receptor. Cell surface IFN-gammaR2 were detected by flow cytometry. Cellular responses to IFN-gamma were impaired but not abolished. Transfection with the wild-type IFNGR2 gene restored full responsiveness to IFN-gamma. This is the first demonstration of partial IFN-gammaR2 deficiency in humans. (+info)
Differentiation among members of the Mycobacterium tuberculosis complex by molecular and biochemical features: evidence for two pyrazinamide-susceptible subtypes of M. bovis.
(30/1137)
The variations in biochemical as well as molecular characteristics among several members of the Mycobacterium tuberculosis complex that are not M. tuberculosis have been assessed to facilitate an unambiguous species identification. Altogether, 96 M. tuberculosis complex strains including 52 M. bovis isolates and 44 M. africanum isolates were analyzed by spoligotyping. The strains could be clustered into five spoligotype groups. All M. bovis isolates showed the typical absence of the spacers 39 to 43 and typical biochemical properties. However, within these strains we found a group of strains that had a spoligotype pattern which is clearly defined by the additional absence of spacers 3 to 16 and that were uncommonly susceptible to pyrazinamide (PZA). This spoligotype pattern has previously been described as being typical for a caprine genotype because of its predominant isolation from sheep and goats. Due to the clinical importance of PZA resistance, we propose two M. bovis subtypes: M. bovis subtype bovis, which is resistant to PZA, and M. bovis subtype caprae, which is susceptible to PZA. Two additional strains that clustered in group 3 showed biochemical and genetic properties typical for M. bovis and were also sensitive to PZA; thus, they may represent a third PZA-susceptible M. bovis subtype. The M. africanum isolates could be clustered into two spoligotype groups which can be differentiated from M. bovis by hybridization to spacers 39 to 43. These groups correspond to the previously described M. africanum subtypes I and II and can be clearly distinguished from each other by spoligotyping and resistance to thiophen-2-carboxylic acid hydrazide. Our results demonstrate that spoligotyping is a useful tool for differentiation of M. bovis and M. africanum. Moreover, we describe two PZA-susceptible M. bovis subtypes and describe a method that facilitates an unambiguous differentiation of the two M. africanum subtypes. (+info)
Sequence-based identification of Mycobacterium species using the MicroSeq 500 16S rDNA bacterial identification system.
(31/1137)
We evaluated the MicroSeq 500 16S rDNA Bacterial Sequencing Kit (PE Applied Biosystems), a 500-bp sequence-based identification system, for its ability to identify clinical Mycobacterium isolates. The organism identity was determined by comparing the 16S rDNA sequence to the MicroSeq database, which consists primarily of type strain sequences. A total of 113 isolates (18 different species), previously recovered and identified by routine methods from two clinical laboratories, were analyzed by the MicroSeq method. Isolates with discordant results were analyzed by hsp65 gene sequence analysis and in some cases repeat phenotypic identification, AccuProbe rRNA hybridization (Gen-Probe, Inc., San Diego, Calif.), or high-performance liquid chromatography of mycolic acids. For 93 (82%) isolates, the MicroSeq identity was concordant with the previously reported identity. For 18 (16%) isolates, the original identification was discordant with the MicroSeq identification. Of the 18 discrepant isolates, 7 (six unique sequences) were originally misidentified by phenotypic analysis or the AccuProbe assay but were correctly identified by the MicroSeq assay. Of the 18 discrepant isolates, 11 (seven unique sequences) were unusual species that were difficult to identify by phenotypic methods and, in all but one case, by molecular methods. The remaining two isolates (2%) failed definitive phenotypic identification, but the MicroSeq assay was able to definitively identify one of these isolates. The MicroSeq identification system is an accurate and rapid method for the identification of Mycobacterium spp. (+info)
Evaluation of the BACTEC MGIT 960 and the MB/BacT systems for recovery of mycobacteria from clinical specimens and for species identification by DNA AccuProbe.
(32/1137)
A total of 120 mycobacterial isolates were recovered from 1,068 clinical specimens. Of these, 82.5% were in MGIT 960, 83.3% were in MB/BacT, 80% were in BACTEC 460, and 70% were on Lowenstein-Jensen medium. Mean times to detection of Mycobacterium tuberculosis (n = 96) were significantly shorter with MGIT 960 (12.6 days, P = 0.003) and BACTEC 460 (11.8 days, P < 0.001) than with MB/BacT (15.9 days). Although, MGIT 960 showed the lowest rate of recovery of M. kansasii genotype I (64.3%), the earliest growth was detected with this system (8.9 days). Low and similar rates of contamination were obtained with MGIT 960 (3.3%) and MB/BacT (3%). The AccuProbe test for identification showed excellent sensitivities with MGIT 960 (96. 8%) and MB/BacT (100%) cultures. In addition to being nonradiometric, both MGIT 960 and MB/BacT are accurate, rapid, and labor-saving detection systems which could replace the radiometric method. (+info)