Characterization of Clinical Isolates of Mycobacterium simiae Using Drug Susceptibility Tests and Molecular Analyses

Pyrazinamide (PZA) is widely used to treat drug-sensitive or multidrug resistance tuberculosis. However, conventional PZA susceptibility tests of clinical isolates are rather difficult because of the requirement of acid pH. Since resistance to pyrazinamide is primary mediated by mutation of pncA, an alternative way of PZA susceptibility test is to analyze the pyrazinamidase activities of Mycobacterium tuberculosis clinical isolates. Therefore, a database containing the full spectrum of pncA mutations along with pyrazinamidase activities will be beneficial. To characterize mutations of pncA in M. tuberculosis from Chongqing, China, the pncA gene was sequenced and analyzed in 465 clinical isolates. A total of 124 types of mutations were identified in 424 drug-resistant isolates, while no mutation was identified in the 31 pan-susceptible isolates. Ninety-four of the 124 mutations had previously been reported, and 30 new mutations were identified. Based on reported literatures, 294 isolates could be predicted resistant to pyrazinamide. Furthermore, pyrazinamidase activities of the 30 new mutations were tested using the Escherichia coli pncA gene knockout strain. The results showed that 24 of these new mutations (28 isolates) led to loss of pyrazinamidase activity and six (8 isolates) of them did not. Taken together, 322 isolates with pncA mutations could be predicted to be PZA resistant among the 424 drug-resistant isolates tested. Analysis of pncA mutations and their effects on pyrazinamidase activity will not only enrich our knowledge of comprehensive pncA mutations related with PZA resistance but also facilitate rapid molecular diagnosis of pyrazinamide resistance in M. tuberculosis.

Download Full-text

Five years prospective survey of antibiotic resistance in Bacteroides and Parabacteroides isolated from inpatients of clinical hospital in Warsaw, Poland

Medycyna Doświadczalna i Mikrobiologia ◽

10.32394/mdm.72.02 ◽

2020 ◽

pp. 13-19

Keyword(s):

Clavulanic Acid ◽

Antimicrobial Susceptibility ◽

Bacterial Infections ◽

Anaerobic Bacteria ◽

Empirical Therapy ◽

Drug Susceptibility ◽

Clinical Isolates ◽

Patient Treatment ◽

Antimicrobial Susceptibility Tests ◽

Susceptibility Tests

Objectives: Diagnostics of anaerobic bacterial infections and determination of drug susceptibility are technically difficult and time-consuming; therefore, the number of studies on Anaerobic Gram-negative bacilli is significantly limited, especially in Europe. The aim of the study was to analyze the antibiotic susceptibility of clinically important anaerobic bacteria Bacteroides spp. and Parabacteroides distasonis. Strains were isolated from infections of patients hospitalized at one Polish hospital as a result of routine microbiological diagnostics. Material and methods: Clinical isolates were identified with MALDI-TOF MS. Antimicrobial susceptibility of 276 strains was carried out by E-test gradient strip to commonly used antibiotics i.e. benzylpenicillin, amoxicillin with clavulanic acid, imipenem, clindamycin and metronidazole. MIC values were determined. The interpretation of antimicrobial susceptibility tests were conducted in accordance with The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommendations. Results: Susceptibility tests of all isolates yielded the following rates of resistance to the evaluated β-lactam antibiotics: benzylpenicillin (96%), amoxicillin/clavulanic acid (7.6%), imipenem (2.1%). In presented study 38.8% of clindamycin-resistant strains were isolated, among them 18.3% of B. fragilis and 53.85% P. distasonis. All strain were susceptible to metronidazole. Conclusions: Obtained results and analysis of the results of other researchers convinces us that it is necessary to routinely or at least periodically monitor drug susceptibility of clinical isolates of anaerobic bacteria and use targeted therapy based on the result of the antibiogram. Although high percentage of the tested Bacteroides and Parabacteroides strains remained susceptible to metronidazole and β-lactam antibiotics the use of clindamycin in empirical therapy may not be efficacious. Antibiogram results should be consult with the staff responsible for patient treatment and hospital antibiotic policies.

Download Full-text