Detection of rifampin resistance patterns in Mycobacterium tuberculosis strains isolated in Iran by polymerase chain reaction-single-strand conformation polymorphism and direct sequencing methods

Isolation and identification of non-tuberculous mycobacteria from aquarium fish in Ilam, Iran

Non-tuberculous mycobacteria (NTM) are among the most important pathogens in wild, captive, marine, and freshwater fish species. So, it is important to consider fish as the primary source of infection for aquarium fish and humans. The present study analyzed the occurrence of NTM in aquarium fish in Ilam, west of Iran. In total, 50 samples of infected fish were collected from different aquariums. Following initial sample processing, sediment of each sample was inoculated into Lowenstein-Jensen and Herrold egg media. The positive colonies were investigated with, growth rate, pigmentation, colony morphology, niacin accumulation, nitrate reduction, catalase activity, urease activity, and arylsulfatase activity. Also, molecular identification was carried out by sequencing of heat shock protein 65 kD gene (hsp65) sequence analysis. According to our results, NTM were isolated from 13 samples (26%), comprising 6 (46.2%) rapid growing, and 7 (53.8%) slow growing mycobacteria. In addition, Mycobacterium marinum was the most common NTM isolated in ornamental fish, which is potentially dangerous for both fish and humans. In conclusion, the current study indicates that ornamental fish play a significant role as a source of NTM.

Evaluation of the effect of Pulicaria gnaphalodes and Perovskia abrotanoides essential oil extracts against Mycobacterium tuberculosis strains

Background:

Mycobacterium tuberculosis (MTB) is the causative agent of tuberculosis (TB), which remains one of the major public health problems in the world. The increasing incidence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) worldwide highlights the urgent need to search for alternative antimycobacterial agents. More and more people in developing countries utilize traditional medicine for their major primary health care needs. It has been determined that the medicinal plants Pulicaria gnaphalodes and Perovskia abrotanoides possess strong antibacterial effect.

Materials and Methods:

In this study, the antimycobacterial effects of P. gnaphalodes and P. abrotanoides essential oil on MTB were examined. Essential oil was prepared from P. gnaphalodes aerial parts and P. abrotanoides flower. The effects of six different concentrations (20 μg/ml, 40 μg/ml, 80 μg/ml, 160 μg/ml, 320 μg/ml, and 640 μg/ml) were examined against sensitive isolates of MTB and MTB H37Rv (ATCC 27294).

Results:

The results showed that P. gnaphalodes and P. abrotanoides essential oil extracts have strong inhibitory effects on MTB. This activity for P. gnaphalodes was observed from very low (4%) to good (70.9%) effect; meanwhile, this activity for P. abrotanoides was observed from very low (4%) to strong (86%) effect.

Conclusion:

The mean of inhibition percentage for P. gnaphalodes and P. abrotanoides in 640 μg/ml was 58.1% and 76.2%, respectively. So, P. abrotanoides plant is more effective against MTB than P. gnaphalodes. Identification of the effective fraction against MTB is a further step to be studied.

Analysis of DNA gyrA Gene Mutation in Clinical and Environmental Ciprofloxacin-Resistant Isolates of Non-Tuberculous Mycobacteria Using Molecular Methods

Background

During the past several years, nontuberculous mycobacteria (NTM) have been reported as some of the most important agents of infection in immunocompromised patients.

Objectives

The aim of this study was to evaluate the ciprofloxacin susceptibility of clinical and environmental NTM species isolated from Isfahan province, Iran, using the agar dilution method, and to perform an analysis of gyrA gene-related ciprofloxacin resistance.

Materials and Methods

A total of 41 clinical and environmental isolates of NTM were identified by conventional and multiplex PCR techniques. The isolates were separated out of water, blood, abscess, and bronchial samples. The susceptibility of the isolates to 1 µg/mL, 2 µg/mL and 4 µg/mL of ciprofloxacin concentrations was determined by the agar dilution method according to CLSI guidelines. A 120-bp area of the gyrA gene was amplified, and PCR-SSCP templates were defined using polyacrylamide gel electrophoresis. The 120-bp of gyrA amplicons with different PCR-SSCP patterns were sequenced.

Results

The frequency of the identified isolates was as follows: Mycobacterium fortuitum, 27 cases; M. gordonae, 10 cases; M. smegmatis, one case; M. conceptionense, one case; and M. abscessus, two cases. All isolates except for M. abscessus were sensitive to all three concentrations of ciprofloxacin. The PCR-SSCP pattern of the gyrA gene of resistant M. abscessus isolates showed four different bands. The gyrA sequencing of resistant M. abscessus isolates showed 12 alterations in nucleotides compared to the M. abscessus ATCC 19977 resistant strain; however, the amino acid sequences were similar.

Conclusions

This study demonstrated the specificity and sensitivity of the PCR-SSCP method for finding mutations in the gyrA gene. Due to the sensitivity of most isolates to ciprofloxacin, this antibiotic should be considered an appropriate drug for the treatment of related diseases.

A systematic review of rapid drug susceptibility tests for multidrug-resistant tuberculosis using rifampin resistance as a surrogate

BACKGROUND

The emergence of multidrug-resistant tuberculosis (MDR-TB) has prompted the development of rapid drug susceptibility assays with a focus on rifampin in recent years. Systematic reviews with evaluation of predictive values for different assays are scarce.

METHOD

MEDLINE was searched on 6 September 2008 for English articles that contain concurrent original data for generating summary measures of sensitivity, specificity and likelihood ratios of rapid rifampin susceptibility assays.

RESULTS/CONCLUSIONS

Significant heterogeneity was found in likelihood ratios across studies of all assays except nitrate reductase assay and colorimetric assays. Although rapid assays are fairly reliable for ruling out MDR-TB, careful consideration of clinical risk factors is required before using these assays to rule in MDR-TB under different epidemiological settings.

Rapid and accurate identification of Mycobacterium tuberculosis complex and common non-tuberculous mycobacteria by multiplex real-time PCR targeting different housekeeping genes

Rapid and accurate identification of mycobacteria isolates from primary culture is important due to timely and appropriate antibiotic therapy. Conventional methods for identification of Mycobacterium species based on biochemical tests needs several weeks and may remain inconclusive. In this study, a novel multiplex real-time PCR was developed for rapid identification of Mycobacterium genus, Mycobacterium tuberculosis complex (MTC) and the most common non-tuberculosis mycobacteria species including M. abscessus, M. fortuitum, M. avium complex, M. kansasii, and the M. gordonae in three reaction tubes but under same PCR condition. Genetic targets for primer designing included the 16S rDNA gene, the dnaJ gene, the gyrB gene and internal transcribed spacer (ITS). Multiplex real-time PCR was setup with reference Mycobacterium strains and was subsequently tested with 66 clinical isolates. Results of multiplex real-time PCR were analyzed with melting curves and melting temperature (T (m)) of Mycobacterium genus, MTC, and each of non-tuberculosis Mycobacterium species were determined. Multiplex real-time PCR results were compared with amplification and sequencing of 16S-23S rDNA ITS for identification of Mycobacterium species. Sensitivity and specificity of designed primers were each 100 % for MTC, M. abscessus, M. fortuitum, M. avium complex, M. kansasii, and M. gordonae. Sensitivity and specificity of designed primer for genus Mycobacterium was 96 and 100 %, respectively. According to the obtained results, we conclude that this multiplex real-time PCR with melting curve analysis and these novel primers can be used for rapid and accurate identification of genus Mycobacterium, MTC, and the most common non-tuberculosis Mycobacterium species.

Rapid identification of mycobacteria and drug-resistant Mycobacterium tuberculosis by use of a single multiplex PCR and DNA sequencing

Tuberculosis (TB) remains a significant global health problem for which rapid diagnosis is critical to both treatment and control. This report describes a multiplex PCR method, the Mycobacterial IDentification and Drug Resistance Screen (MID-DRS) assay, which allows identification of members of the Mycobacterium tuberculosis complex (MTBC) and the simultaneous amplification of targets for sequencing-based drug resistance screening of rifampin-resistant (rifampin(r)), isoniazid(r), and pyrazinamide(r) TB. Additionally, the same multiplex reaction amplifies a specific 16S rRNA gene target for rapid identification of M. avium complex (MAC) and a region of the heat shock protein 65 gene (hsp65) for further DNA sequencing-based confirmation or identification of other mycobacterial species. Comparison of preliminary results generated with MID-DRS versus culture-based methods for a total of 188 bacterial isolates demonstrated MID-DRS sensitivity and specificity as 100% and 96.8% for MTBC identification; 100% and 98.3% for MAC identification; 97.4% and 98.7% for rifampin(r) TB identification; 60.6% and 100% for isoniazid(r) TB identification; and 75.0% and 98.1% for pyrazinamide(r) TB identification. The performance of the MID-DRS was also tested on acid-fast-bacterium (AFB)-positive clinical specimens, resulting in sensitivity and specificity of 100% and 78.6% for detection of MTBC and 100% and 97.8% for detection of MAC. In conclusion, use of the MID-DRS reduces the time necessary for initial identification and drug resistance screening of TB specimens to as little as 2 days. Since all targets needed for completing the assay are included in a single PCR amplification step, assay costs, preparation time, and risks due to user errors are also reduced.

Rapid detection of isoniazid, rifampin, and ofloxacin resistance in Mycobacterium tuberculosis clinical isolates using high-resolution melting analysis

A high-resolution melting analysis (HRMA) assay was developed to detect isoniazid, rifampin, and ofloxacin resistance in Mycobacterium tuberculosis by targeting resistance-associated mutations in the katG, mabA-inhA promoter, rpoB, and gyrA genes. A set of 28 (17 drug-resistant and 11 fully susceptible) clinical M. tuberculosis isolates was selected for development and evaluation of HRMA. PCR amplicons from the katG, mabA-inhA promoter, rpoB, and gyrA genes of all 28 isolates were sequenced. HRMA results matched well with 18 mutations, identified by sequencing, in 17 drug-resistant isolates and the absence of mutations in 11 susceptible isolates. Among 87 additional isolates with known resistance phenotypes, HRMA identified katG and/or mabA-inhA promoter mutations in 66 of 69 (95.7%) isoniazid-resistant isolates, rpoB mutations in 51 of 54 (94.4%) rifampin-resistant isolates, and gyrA mutations in all of 41 (100%) ofloxacin-resistant isolates. All mutations within the HRMA primer target regions were detected as variant HRMA profiles. The corresponding specificities were 97.8%, 100%, and 98.6%, respectively. Most false-positive results were due to synonymous mutations, which did not affect susceptibility. HRMA is a rapid, sensitive method for detection of drug resistance in M. tuberculosis which could be used routinely for screening isolates in countries with a high prevalence of tuberculosis and drug resistance or in individual isolates when drug resistance is suspected.

PCR-single-strand conformational polymorphism method for rapid detection of rifampin-resistant Mycobacterium tuberculosis: systematic review and meta-analysis

The reference standard methods for drug susceptibility testing of Mycobacterium tuberculosis, such as culture on Lowenstein-Jensen or Middlebrook 7H10/11 medium, are very slow to give results; and due to the emergence of multidrug-resistant M. tuberculosis and extensively drug-resistant M. tuberculosis, there is an urgent demand for new, rapid, and accurate drug susceptibility testing methods. PCR-single-strand conformational polymorphism (PCR-SSCP) analysis has been proposed as a rapid method for the detection of resistance to rifampin, but its accuracy has not been systematically evaluated. We performed a systematic review and meta-analysis to evaluate the accuracy of PCR-SSCP analysis for the detection of rifampin-resistant tuberculosis. We searched the Medline, Embase, Web of Science, BIOSIS, and LILACS databases and contacted authors if additional information was required. Ten studies met our inclusion criteria for rifampin resistance detection. We applied the summary receiver operating characteristic (SROC) curve to perform the meta-analysis and to summarize diagnostic accuracy. The sensitivity of PCR-SSCP analysis for the rapid detection of rifampin-resistant tuberculosis was 0.79 (95% confidence interval [CI], 0.75 to 0.82), the specificity was 0.96 (95% CI, 0.94 to 0.98), the positive likelihood ratio was 16.10 (95% CI, 5.87 to 44.13), the negative likelihood ratio was 0.20 (95% CI, 0.10 to 0.40), and the diagnostic odds ratio was 100.93 (95% CI, 31.95 to 318.83). PCR-SSCP analysis is a sensitive and specific test for the rapid detection of rifampin-resistant M. tuberculosis. Additional studies in countries with a high prevalence of multidrug-resistant M. tuberculosis and also cost-effectiveness analysis are required in order to obtain a complete picture on the utility of this method for rapid drug resistance detection in M. tuberculosis.

High-level rifampin resistance correlates with multiple mutations in the rpoB gene of pulmonary tuberculosis isolates from the Afghanistan border of Iran

The aim of this study was to investigate the significance of multiple mutations in the rpoB gene as well as predominant nucleotide changes and their correlation with high levels of resistance to rifampin (rifampicin) in Mycobacterium tuberculosis isolates that were randomly collected from the sputa of 46 patients with primary and secondary cases of active pulmonary tuberculosis from the southern region (Afghanistan border) of Iran where tuberculosis is endemic. Drug susceptibility testing was performed using the CDC standard conventional proportional method. DNA extraction, rpoB gene amplification, and DNA sequencing analysis were performed. Thirty-five (76.09%) isolates were found to have multiple mutations (two to four) in the rpoB (beta-subunit) gene. Furthermore, we demonstrate that the combination of mutations with more prevalent nucleotide changes were observed in codons 523, 526, and 531, indicating higher frequencies of mutations among patients with secondary infection. In this study, 76.08% (n = 35) of all isolates found to have mutation combinations involving nucleotide changes in codons 523 (GGG-->GCG), 531 (TCG-->TTG or TTC), and 526 (CAC-->CGC, TTC, AAC, or CAA) demonstrated an association with higher levels of resistance to rifampin (MIC, >or=100 microg/ml).

Characterization of RPO B gene for detection of rifampicin drug resistance by SSCP and sequence analysis

PURPOSE

Because of the emergence of multidrug-resistant tuberculosis in recent times, the rapid detection of resistance to the first-line anti-tuberculosis drug rifampicin was felt worldwide. Accordingly, this study was conducted to evaluate the diagnostic potential of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) for checking its utility as a rapid screening test for determination of rifampicin drug resistance.

MATERIALS AND METHODS

A total of 34 isolates of Mycobacterium tuberculosis (M. tuberculosis) (22 rifampicin resistant, 11 rifampicin sensitive and one control H37Rv) strains were analysed by PCR-SSCP and DNA sequencing within the 157-bp region of the rpo B gene (Ala 500-Val 550).

RESULTS

Rifampicin resistance was detected successfully by PCR-SSCP in 20/22(90.90%) of rifampicin-resistant strains showing a total of nine different mutations in seven codon positions: codon 513 (CAA-->CCA), 516 (GAC-->GTC), 507 (GGC-->GAC), 526 (CAC-->GAC, TAC), 531 (TCG-->TTG, TGG), 522 (TCG-->TGG) and 533 (GTG-->CCG). Two rifampicin-resistant strains showed an identical PCR-SSCP pattern with the wild type H37Rv; 77.27% rifampicin-resistant strains showed a single point mutation and 9.09% had no mutation. Three rifampicin-resistant strains showed characteristic double mutations at codon positions 526 and 531. Sensitivity and specificity were calculated as 90.90% and 100%.

CONCLUSIONS

Rifampicin-resistant genotypes were mainly found in codon positions 516, 526 and 531. PCR-SSCP seems to be an efficacious method of predicting rifampicin resistance and substantially reduces the time required for susceptibility testing from 4 to 6 weeks to a few weeks.

Genotypic detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis strains by DNA sequencing: a randomized trial

BACKGROUND

Tuberculosis is a growing international health concern. It is the biggest killer among the infectious diseases in the world today. Early detection of drug resistance allows starting of an appropriate treatment. Resistance to drugs is due to particular genomic mutations in specific genes of Mycobacterium tuberculosis(MTB). The aim of this study was to identify the presence of Isoniazid (INH) and Rifampicin(RIF) drug resistance in new and previously treated tuberculosis (TB) cases using DNA sequencing.

METHODS

This study was carried out on 153 tuberculous patients with positive Bactec 460 culture for acid fast bacilli.

RESULTS

Of the 153 patients, 105 (68.6%) were new cases and 48 (31.4%) were previously treated cases. Drug susceptibility testing on Bactec revealed 50 resistant cases for one or more of the first line antituberculous. Genotypic analysis was done only for rifampicin resistant specimens (23 cases) and INH resistant specimens (26 cases) to detect mutations responsible for drug resistance by PCR amplification of rpoB gene for rifampicin resistant cases and KatG gene for isoniazid resistant cases. Finally, DNA sequencing was done for detection of mutation within rpoB and KatG genes. Genotypic analysis of RIF resistant cases revealed that 20/23 cases (86.9%) of RIF resistance were having rpoB gene mutation versus 3 cases (13.1%) having no mutation with a high statistical significant difference between them (P < 0.001). Direct sequencing of Kat G gene revealed point mutation in 24/26 (92.3%) and the remaining 2/26 (7.7%) had wild type KatG i.e. no evidence of mutation with a high statistical significant difference between them (P < 0.001).

CONCLUSION

We can conclude that rifampicin resistance could be used as a useful surrogate marker for estimation of multidrug resistance. In addition, Genotypic method was superior to that of the traditional phenotypic method which is time-consuming taking several weeks or longer.