Laboratory tools for tuberculosis control in a setting with a high burden of HIV/AIDS.

Introduction. Nosocomial transmission of Mycobacterium tuberculosis is an important health issue and the detection of tuberculosis (TB) cases is the main tool for controlling this disease.Aim. We aimed to assess the possible occurrence of nosocomial transmission of M. tuberculosis in a reference hospital for HIV/AIDS patients and evaluate both the performance of the Xpert MTB/RIF (Xpert) platform and drug resistance profiles.Methodology. We evaluated the performance of the Xpert platform. Samples that tested positive on the BACTEC MGIT 320 (MGIT320) platform were submitted for genotyping and drug susceptibility testing.Results. In this study, pulmonary and extrapulmonary samples from 407 patients were evaluated, and among these, 15.5 % were diagnosed with TB by the MGIT320 platform, with a TB/HIV coinfection rate of 52.4 %. The Xpert platform gave positive results for TB for 11 samples with negative results on the MGIT320 platform. In the genotyping results, 53.3 % of the strains clustered; of these strains, half were in two of the four clusters formed, and the patients had visited the hospital on the same day. Drug resistance was observed in 11.7 % of the strains.Conclusion. Putative nosocomial transmission of M. tuberculosis was detected, showing that genotyping is a powerful approach for understanding the dynamics of M. tuberculosis transmission, especially in a high-burden TB and HIV landscape.

Comparative evaluation of the Nitrate Reductase Assay and the Resazurin Microtitre Assay for drug susceptibility testing of Mycobacterium tuberculosis against first line anti-tuberculosis drugs.

Tuberculosis remains as a serious infection disease of worldwide distribution, with high morbidity and mortality, mainly in low socio-economic condition countries. The state of emergency of tuberculosis caused by the resistant and multidrug-resistant (MDR) strains, became the main threat to the tuberculosis treatment and control programs. A fast detection method for the resistant strains will allow the implementation of an adequate treatment and contribute for controlling the dissemination of these resistant strains. This study evaluated the performance of the nitrate reductase assay in solid (NRA-LJ) and liquid (NRA-7H9) media, to determine the susceptibility to first line anti-tuberculosis drugs: isoniazid (INH), rifampicin (RMP), ethambutol (EMB) and streptomycin (SMR). Both methods NRA-LJ and NRA-7H9 were evaluated among 18 strains with a known susceptibility profile. The resazurin microtiter assay (REMA) was performed as a reference method. One hundred percent of accordance was observed between NRA-7H9 and REMA for the four tested drugs. When the NRA-LJ method was compared to REMA, the sensitivity and the specificity to INH, RMP, EMB and SMR were 100%, 100 %, 85.7%, 76.9% and 80%, 100%, 75% and 80%, respectively. From the 57 clinical isolates of M. tuberculosis evaluated by NRA-7H9 and REMA, 56 (98.2%) were sensitive to all antibiotics tested (INH, RMP, EMB and SMR) by the NRA-7H9 method, while three of these strains were resistant to INH by REMA. One strain showed resistance to INH and RMP for both methods, and MIC of 1.0 µg/ml to INH for both methods, while MIC of 1.0 and 2.0 µg/ml to RMP for REMA and NRA-7H9, respectively. The three assays showed a high level of agreement for rapid detection of rifampicin and isoniazid resistance. Regarding rapidness, the detection of color change in the NRA method is within instants as compared to the overnight incubation required for the REMA test. NRA might represent an inexpensive and alternative assay for rapid detection of resistance in low-income countries.

Activity of Rifabutin and Hemi-synthetic Derivatives Against Mycobacterium abscessus.

BACKGROUND: Mycobacterium abscessus causes a wide range of clinical diseases that are difficult to treat. This microorganism is resistant not only to the classical antituberculosis agents but also to most of the antimicrobials that are currently available, resulting in limited therapeutic options and treatment failure. This scenario stresses the need to search for new drugs with activity against M. abscessus. OBJECTIVE: To evaluate in vitro the antimycobacterial activity and cytotoxicity of rifabutin (RFB 1) and ten derivatives (2-11) against M. abscessus ATCC 19977. METHOD: The minimum inhibitory concentration (MIC) of the molecules was determined by the microdilution broth method according to the guideline described in CLSI. The toxicity evaluation was carried in 96-well microplates, using the cell line J774A.1 (ATCC TIB-67). RESULT: From the eleven molecules tested, RFB 1 and RFB 4 were the compounds showing higher activities against M. abscessus, with MICs of 0.9 and 1.0 µM, respectively. The R1 and R2 moieties seem to have deciding influence over the final activity. Furthermore, N-oxide derivatives 9, 10, and 11 were also active against M. abscessus, with MICs of 7.2 µM, 1.8 µM and 3.8 µM, respectively. An explanatory hypothesis for the better activities of compounds RFB 1, RFB 4, RFB 10 and RFB 11 considers the likely hydrogen bonding between ligands and receptor, balancing the global flexibility and interaction energies. RFB 1 and its most effective derivatives were found to be not toxic. CONCLUSION: Besides RFB 1, its derivatives 4, 10 and 11 show potential for clinical development in the M. abscessus treatment.

High frequency of aac(6')-Ib-cr gene associated with double mutations in gyrA and parC in Escherichia coli isolates from patients with urinary tract infections.

OBJECTIVES: The aims of this study were (i) to determine the frequency of plasmid-mediated resistance to fluoroquinolones (FQs) in Escherichia coli isolated from patients with urinary tract infections (UTIs) of nosocomial and community origin and (ii) to determine the relationships between the presence of extended-spectrum ß-lactamases (ESBLs), mutations in the gyrA and parC genes, and resistance to FQs. METHODS: A total of 71 E. coli isolates, including 38 ESBL-producers and 33 non-ESBL-producers, were analysed. The aac(6')-Ib gene was amplified using PCR and was subsequently digested with the BtsCI restriction enzyme to identify aac(6')-Ib-cr, a variant associated with FQ resistance. Detection of qnr genes was performed by multiplex PCR. In isolates that tested positive for these genes, the gyrA and parC genes were sequenced and the modulation factor of an efflux pump inhibitor was determined on the minimum inhibitory concentration (MIC) of norfloxacin. RESULTS: The frequencies of qnrS, qnrB and qnrA were 4.2%, 2.8% and 0%, respectively. The frequency of aac(6')-Ib-cr was 40.8% and this variant was associated with double mutations in gyrA and parC as well as resistance to FQs and ESBL production. Modulation of efflux pump activity was more frequent in resistant isolates that had a wild-type parC gene. CONCLUSION: An interplay of resistance mechanisms increased the level of resistance to FQs, and the high frequency of putative plasmid-mediated quinolone resistance genes associated with ESBL-producing isolates reduced therapeutic options to treat UTIs in the affected population.

Naphthoquinone Derivatives as Scaffold to Develop New Drugs for Tuberculosis Treatment.

Despite being a curable disease, tuberculosis (TB) remains a public health problem worldwide mainly due to lengthy treatment, as well as its toxic effects, TB/HIV co-infection and the emergence of resistant Mycobacterium tuberculosis strains. These barriers reinforcing the need for development of new antimicrobial agents, that ideally should reduce the time of treatment and be active against susceptible and resistant strains. Quinones are compounds found in natural sources and among them, the naphthoquinones show antifungal, antiparasitic, and antimycobacterial activity. Thus, we evaluated the potential antimycobacterial activity of six 1,4-naphthoquinones derivatives. We determined the minimum inhibitory concentration (MIC) of the compounds against three M. tuberculosis strains: a pan-susceptible H37Rv (ATCC 27294); one mono-resistant to isoniazid (ATCC 35822); and one mono-resistant to rifampicin (ATCC 35838); the cytotoxicity in the J774A.1 (ATCC TIB-67) macrophage lineage; performed in silico analysis about absorption, distribution, metabolism, and excretion (ADME) and docking sites. All evaluated naphthoquinones were active against the three strains with MIC between 206.6 and 12.5 µM, and the compounds with lower MIC values have also showed low cytotoxicity. Moreover, two naphthoquinones derivatives 5 and 6 probably do not exhibit cross resistance with isoniazid and rifampicin, respectively, and regarding ADME analysis, no compound violated the Lipinski's rule-of-five. Considering the set of findings in this study, we conclude that these naphthoquinones could be promising scaffolds to develop new therapeutic strategies to TB.

In vitro anti-mycobacterial activity of (E)-N'-(monosubstituted-benzylidene) isonicotinohydrazide derivatives against isoniazid-resistant strains.

A series of twenty-three N-acylhydrazones derived from isoniazid (INH 1-23) have been evaluated for their in vitro antibacterial activity against INH- susceptible strain of M. tuberculosis (RG500) and three INH-resistant clinical isolates (RG102, RG103 and RG113). In general, derivatives 4, 14, 15 and 16 (MIC=1.92, 1.96, 1.96 and 1.86 µM, respectively) showed relevant activities against RG500 strain, while the derivative 13 (MIC=0.98 µM) was more active than INH (MIC=1.14 µM). However, these derivatives were inactive against RGH102, which displays a mutation in the coding region of inhA. These results suggest that the activities of these compounds depend on the inhibition of this enzyme. However, the possibility of other mechanisms of action cannot be excluded, since compounds 2, 4, 6, 7, 12-17, 19, 21 and 23 showed good activities against katG-resistant strain RGH103, being more than 10-fold more active than INH.