Cengiz Cavusoglu

Characterization of rpoB Mutations in Rifampin-Resistant Clinical Isolates of Mycobacterium tuberculosis from Turkey by DNA Sequencing and Line Probe Assay

ABSTRACT Mutations in an 81-bp region of the rpoB gene associated with rifampin resistance were studied in 41 rifampin-resistant clinical strains of Mycobacterium tuberculosis isolated in Turkey. Fourteen different rpoB alleles, three of which had not been reported before, were found. A reverse hybridization-based line probe assay (the Inno-LiPA Rif.TB test) for rapid detection of the mutations was evaluated with these isolates. Rifampin resistance was correctly identified in 23 of 41 isolates (56.1%) with the kits R probes specific for these mutations. Seventeen of 41 isolates (41.5%) yielded hybridization patterns, with at least one negative signal obtained with the S probes for the wild type. One isolate was identified as rifampin sensitive by the line probe assay. The rate of concordance of the results of the line probe assay with the results of the in vitro susceptibility test was high (97.6%). These results demonstrate that the line probe assay kit may be useful for the rapid diagnosis of rifampin-resistant tuberculosis.

Evaluation of the GeneXpert MTB/RIF Assay for Rapid Diagnosis of Tuberculosis and Detection of Rifampin Resistance in Pulmonary and Extrapulmonary Specimens

ABSTRACT Mycobacterium tuberculosis remains one of the most significant causes of death from an infectious agent. The rapid diagnosis of tuberculosis and detection of rifampin (RIF) resistance are essential for early disease management. The GeneXpert MTB/RIF assay is a novel integrated diagnostic device for the diagnosis of tuberculosis and rapid detection of RIF resistance in clinical specimens. We determined the performance of the MTB/RIF assay for rapid diagnosis of tuberculosis and detection of rifampin resistance in smear-positive and smear-negative pulmonary and extrapulmonary specimens obtained from possible tuberculosis patients. Two hundred fifty-three pulmonary and 176 extrapulmonary specimens obtained from 429 patients were included in the study. One hundred ten (89 culture positive and 21 culture negative for M. tuberculosis) of the 429 patients were considered to have tuberculosis. In pulmonary specimens, sensitivities were 100% (27/27) and 68.6% (24/35) for smear-positive and smear-negative specimens, respectively. It had a lower sensitivity with extrapulmonary specimens: 100% for smear-positive specimens (4/4) and 47.7% for smear-negative specimens (21/44). The test accurately detected the absence of tuberculosis in all 319 patients without tuberculosis studied. The MTB/RIF assay also detected 1 RIF-resistant specimen and 88 RIF-susceptible specimens, and the results were confirmed by drug susceptibility testing. We concluded that the MTB/RIF test is a simple method, and routine staff with minimal training can use the system. The test appeared to be as sensitive as culture with smear-positive specimens but less sensitive with smear-negative pulmonary and extrapulmonary specimens that include low numbers of bacilli.

Evaluation of the Genotype MTBDR Assay for Rapid Detection of Rifampin and Isoniazid Resistance in Mycobacterium tuberculosis Isolates

ABSTRACT A novel PCR-based reverse hybridization method Genotype MTBDR assay (Hain Lifescience GmbH, Nehren, Germany) was evaluated for rapid detection of rifampin (RIF) and isoniazid (INH) resistance in Turkish Mycobacterium tuberculosis isolates. The Genotype MTBDR assay is designed to detect mutations within the 81-bp hotspot region of rpoB and mutations at katG codon 315. A total of 41 RIF-resistant M. tuberculosis isolates with rpoB mutations that were previously tested by the INNO-LiPA Rif.TB kit and also characterized by DNA sequencing were included in the study. Thirty-seven of these isolates were also resistant to INH. RIF resistance was correctly identified in 39 of 41 isolates (95.1%) with the Genotype MTBDR assay probes specific for these mutations. One isolate with a Gln-490-His mutation and another one with a CGG insertion between codons 514 and 515 were identified as RIF sensitive by the Genotype MTBDR assay. While the INNO-LiPA Rif.TB kit was able to determine the CGG insertion between codons 514 and 515, the Gln-490-His mutation outside the 81-bp hotspot region was not detected by the INNO-LiPA Rif.TB kit. These isolates had MICs of ≥32 μg/ml for RIF. The Genotype MTBDR assay also correctly identified 27 of 37 INH-resistant isolates (73%) with mutations in katG codon 315. In conclusion, the Genotype MTBDR assay may be useful for the rapid diagnosis of the most common mutations found in multidrug-resistant M. tuberculosis strains. However, the test results should always be confirmed with phenotypic methods.

MYCOBACTERIUM FORTUITUM-CHELONAE COMPLEX INFECTION IN A CHILD WITH COMPLETE INTERLEUKIN-12 RECEPTOR BETA 1 DEFICIENCY

A 10-year-old boy had chronic diarrhea, abdominal pain, severe weight loss and hepatomegaly; multiple enlarged para-aortic and mesenteric lymph nodes. Mycobacterium fortuitum-chelonae complex was identified in the culture of the lymph nodes. Interleukin-12 receptor beta 1 expression could not be observed in phytohemagglutinin-driven T cell blasts. A homozygous missense interleukin-12 receptor beta 1 mutation was found (R173P).

Mycobacterium tuberculosis infection and laboratory diagnosis in solid-organ transplant recipients

Tuberculosis (TB) is an unusual infection in transplant recipients. We evaluated (i) the frequency of TB, (ii) the duration to develop the TB infection, and (iii) clinical consequences, in 380 solid‐organ recipients from January 1995 to December 2000. A total of 10 (2.63%) patients (eight renal, two liver transplant recipients) were found to have post‐transplantation TB. The frequency of TB in this patient population is 8.5‐fold higher than the prevalance in the general Turkish population. Tuberculosis developed within 2–33 months after transplantation, with a median of 15 months. In all of these 10 patients, Mycobacterium tuberculosis (MTB) was isolated from the culture. All the patients continued to have low dose immunosuppressive treatment, and also quadriple antituberculosis treatment [isoniazid (INH), rifampin (RIF), pyrazinamide (PRZ) and ethambutol (ETB)] has been given. The two recipients had died of disseminated form of TB. Relapse was detected in one patient 6 months after the completion of the treatment. As post‐transplant TB infection develops mostly within the first year after transplantation, clinicians should be more careful for early and fast diagnosis and treatment should be started immediately.

Direct electrochemical genosensing for multiple point mutation detection of Mycobacterium tuberculosis during the development of rifampin resistance.

We present a robust and simple method for the direct detection of multiple point mutations in the Mycobacterium tuberculosis rpoB gene during the development of rifampin (RIF) resistance using an electrochemical genosensor. The device contained five different capture probes which are designed to hybridize with several sequence segments within the bacterial rpoB gene hotspot region. Point mutations were detected by monitoring the guanine oxidation with differential pulse voltammetry after hybridization between PCR amplicons and inosine modified capture probes at graphite surface. Changes in the peak voltage corresponding to guanine oxidation provide an electrochemical signal for hybridization that can be used to determine the presence of point mutations conferring rifampin resistance. The analytical parameters (sensitivity, selectivity and reproducibility) were evaluated. High selective discrimination against point mutation of bacteria at hot-spot region was observed. Several mutations were detected at several parts of the amplicon from 21 positive samples.

Mycobacterium celeriflavum sp. Nov., a rapidly growing scotochromogenic bacterium isolated from clinical specimens

Six strains of a rapidly growing scotochromogenic mycobacterium were isolated from pulmonary specimens of independent patients. Biochemical and cultural tests were not suitable for their identification. The mycolic acid pattern analysed by HPLC was different from that of any other mycobacterium. Genotypic characterization, targeting seven housekeeping genes, revealed the presence of microheterogeneity in all of them. Different species were more closely related to the test strains in various regions: the type strain of Mycobacterium moriokaense showed 99.0 % 16S rRNA gene sequence similarity, and 91.5-96.5 % similarity for the remaining six regions. The whole genome sequences of the proposed type strain and that of M. moriokaense presented an average nucleotide identity (ANI) of 82.9 %. Phylogenetic analysis produced poorly robust trees in most genes with the exception of rpoB and sodA where Mycobacterium flavescens and Mycobacterium novocastrense were the closest species. This phylogenetic relatedness was confirmed by the tree inferred from five concatenated genes, which was very robust. The polyphasic characterization of the test strains, supported by the ANI value, demonstrates that they belong to a previously unreported species, for which the name Mycobacterium celeriflavum sp. nov. is proposed. The type strain is AFPC-000207(T) ( = DSM 46765(T) = JCM 18439(T)).

Does dexamethasone affect ceftriazone penetration into cerebrospinal fluid in adult bacterial meningitis

Trough cerebrospinal fluid (CSF) ceftriaxone concentrations were measured daily to investigate the effect of dexamethasone on ceftriaxone penetration into CSF in adult patients with acute bacterial meningitis. Patients were divided into two groups in this double blind randomized study. In group 1 (n=6) patients were given ceftriaxone with dexamethasone whereas in group 2 (n=6) patients were only administered ceftriaxone. Plasma and CSF samples were collected at 24, 48, 72, 96 and 264 h following the study treatments. The trough CSF ceftriaxone concentrations were measured using high performance liquid chromatography (HPLC) and microbiological assay. CSF ceftriaxone concentrations were 3.21 mg/l at 24 h in group 1 and 4.85 mg/l at the same time in group 2 by HPLC. Although microbiological assay results were lower than HPLC the trough CSF ceftriaxone concentrations in dexamethasone group were at least 10(3) times higher than the minimum inhibitory concentrations of the susceptible strains. It was concluded that the ceftriaxone concentration in CSF was adequate and ceftriaxone penetration was not significantly affected by concomitant dexamethasone use in adult patients with acute bacterial meningitis.

Genotyping of rifampin-resistant Mycobacterium tuberculosis isolates from western Turkey

Background Although the rate of multiple drug resistance is high, there is no published data on the transmission rate of drug-resistant strains of Mycobacterium tuberculosis in the Aegean region of western Turkey that are based on molecular methods. Methods IS6110 and pTBN12 restriction fragment length polymorphism (RFLP) methods were used for typing M. tuberculosis strains isolated from 26 sputum samples from 26 patients. Results Nineteen of the rifampin-resistant isolates (73.1%) contained 6 to 11 copies of IS6110. Eighteen different IS6110 DNA fingerprint patterns were observed in the 26 rifampin-resistant isolates. Twenty-three of the 26 rifampin-resistant isolates were also resistant to isoniazid. When evaluated together, both methods yielded 21 (80.9%) different banding patterns and the level of clustering was 34.6%. The average number per pattern was 1.23 (26/21). Conclusions IS6110 fingerprinting suggests that the rifampin-resistant isolates obtained from the Aegean region had a relatively high clustering rate and were clonally related. These findings showed that the rifampin-resistant isolates are actively transmitted between patients. Urgent measures should be taken to prevent the spread of these resistant strains.

Disseminated BCG Infectious Disease and Hyperferritinemia in a Patient With a Novel NEMO Mutation

Hypomorphic mutations of the nuclear factor κB essential modulator gene (NEMO) result in a wide range of clinical phenotypes, including ectodermal dysplasia (EDA) with immunodeficiency and Mendelian susceptibility to mycobacterial disease [1–3]. Mycobacterial infectious diseases are reported in about 40% of patients with the NEMO mutation [1–3]. We report a patient with a novel NEMO mutation who presented with disseminated mycobacterial infection leading to increased ferritin levels with no signs of EDA.