Rapid, simple, and culture-independent detection of rpsL codon 43 mutations that are highly predictive of streptomycin resistance in Mycobacterium tuberculosis

Antimicrobial Susceptibility Pattern of Helicobacter heilmannii and Helicobacter ailurogastricus Isolates

A combined agar and broth dilution method followed by qPCR was used to determine the antimicrobial susceptibility of feline H. heilmannii and H. ailurogastricus isolates. All H. ailurogastricus isolates showed a monomodal distribution of MICs for all the antimicrobial agents tested. For H. heilmannii, a bimodal distribution was observed for azithromycin, enrofloxacin, spectinomycin, and lincomycin. Single nucleotide polymorphisms (SNPs) were found in 50S ribosomal proteins L2 and L3 of the H. heilmannii isolate not belonging to the WT population for azithromycin, and in 30S ribosomal proteins S1, S7, and S12 of the isolate not belonging to the WT population for spectinomycin. The antimicrobial resistance mechanism to enrofloxacin and lincomycin remains unknown (2 and 1 H. heilmannii isolate(s), resp.). Furthermore, H. heilmannii isolates showed higher MICs for neomycin compared to H. ailurogastricus isolates which may be related to the presence of SNPs in several 30S and 50S ribosomal protein encoding genes and ribosomal RNA methyltransferase genes. This study shows that acquired resistance to azithromycin, spectinomycin, enrofloxacin, and lincomycin occasionally occurs in feline H. heilmannii isolates. As pets may constitute a source of infection for humans, this should be kept in mind when dealing with a human patient infected with H. heilmannii.

A genotypic approach for detection, identification, and characterization of drug resistance in Mycobacterium ulcerans in clinical samples and isolates from Ghana

Standardized antimycobacterial therapy is considered the treatment of choice for Buruli ulcer disease. To assess the prevalence of drug resistance among clinical Mycobacterium ulcerans isolates in Ghana, we conducted a sequence-based approach to detect mutations associated with drug resistance. We subjected clinical samples to direct DNA sequencing of rpoB and rpsL genes and compared culture and whole-genome extracts regarding the efficiency of sequence analysis; 99.1% (rpoB) and 100% (rpsL) of the patients harbored M. ulcerans wild type. In one isolate (0.9%), a point mutation of the rpoB gene at codon Ser522 leading to an amino acid change was detected. Culture extracts yielded a significantly higher sequencing efficiency than whole-genome extracts. Our data suggest a low level of drug resistance in Ghana. However, mutations associated with drug resistance do occur and require monitoring. Improved techniques are necessary to enhance the efficiency of sequence analysis of whole-genome extracts.

One-tube loop-mediated isothermal amplification combined with restriction endonuclease digestion and ELISA for colorimetric detection of resistance to isoniazid, ethambutol and streptomycin in Mycobacterium tuberculosis isolates

In this study, we designed a simple and rapid colorimetric detection method, a one-tube loop-mediated isothermal amplification (LAMP)-PCR-hybridization-restriction endonuclease-ELISA [one-tube LAMP-PCR-HY-RE-ELISA] system, to detect resistance to isoniazid, ethambutol and streptomycin in strains of Mycobacterium tuberculosis isolated from clinical specimens. The clinical performance of this method for detecting isoniazid-resistant, ethambutol-resistant and streptomycin-resistant isolates of M. tuberculosis showed 98.9%, 94.3% and 93.8%, respectively. This assay is rapid and convenient that can be performed within one working day. One-tube LAMP-PCR-HY-RE-ELISA system was designed based on hot spot point mutations in target drug-resistant genes, using LAMP-PCR, hybridization, digestion with restriction endonuclease and colorimetric method of ELISA. In this study, LAMP assay was used to amplify DNA from drug-resistant M. tuberculosis, and ELISA was used for colorimetrical determination. This assay will be a useful tool for rapid diagnosis of mutant codons in strains of M. tuberculosis for isoniazid at katG 315 and katG 463, ethambutol at embB 306 and embB 497, and streptomycin at rpsL 43.

Multidrug-resistant tuberculosis in Lisbon, Portugal: a molecular epidemiological perspective

Portugal has the fourth highest tuberculosis (TB) incidence rate in the European Union (EU). Thirty-nine percent of all cases originate in Lisbon Health Region. Portugal also presents high levels of multidrug-resistant tuberculosis (MDR-TB) (1.5%, primary rate and 2.4%, in retreatment cases). In the present study we have characterized 58 MDR-TB clinical isolates by: (i) determining the resistance profile to first- and second-line drugs used in the treatment of tuberculosis; (ii) genotyping all isolates by MIRU-VNTR; (iii) analyzing mutations conferring resistance to isoniazid, rifampicin, streptomycin, and ethambutol, in katG, mabA-inhA, rpoB, rpsL, rrs, and pncA genes. We have therefore established the prevalence of the most common mutations associated with drug resistance in the Lisbon Health Region: C-15T in mabA-inhA for isoniazid; S531L in rpoB for rifampicin; K43R in rpsL for streptomycin; and V125G in pncA for pyrazinamide. By genotyping all isolates and combining with the mutational results, we were able to assess the isolates' genetic relatedness and determine possible transmission events. Strains belonging to family Lisboa, characterized several years ago, are still responsible for the majority of the MDR-TB. Even more alarming is the high prevalence of extensive drug-resistant tuberculosis (XDR-TB) among the MDR-TB isolates, which was found to be 53%. The TB status in Portugal therefore requires urgent attention to contain the strains continuously responsible for MDR-TB and now, XDR-TB.