Assessment of in vitro activities of novel modified antimicrobial peptides against clarithromycin resistant Mycobacterium abscessus

Mycobacterium abscessus (Mab) is one of the most drug resistant bacteria with a high treatment failure rate. Antimicrobial peptides (AMPs) are alternative therapeutic agents against this infection. This study was aimed to assess the in vitro activities of thirteen AMPs (S5, S52, S6, S61, S62, S63, KLK, KLK1, KLK2, Pug-1, Pug-2, Pug-3 and Pug-4) that have never been investigated against drug resistant Mab isolates. Only four novel modified AMPs (S61, S62, S63 and KLK1) provided the lowest minimum inhibitory concentration (MIC) values ranging from 200–400 μg/ml against the Mab ATCC19977 strain. These four potential AMPs were further tested with 16 clinical isolates of clarithromycin resistant Mab. The majority of the tested strains (10/16 isolates, 62.5%) showed ~99% kill by all four AMPs within 24 hours with an MIC <50 μg/ml. Only two isolates (12.5%) with acquired clarithromycin resistance, however, exhibited values <50 μg/ml of four potential AMPs, S61, S62, S63 and KLK1 after 3-days-incubation. At the MICs level, S63 showed the lowest toxicity with 1.50% hemolysis and 100% PBMC viability whereas KLK1 showed the highest hemolysis (10.21%) and lowest PBMC viability (93.52%). S61, S62 and S63 were further tested with clarithromycin-AMP interaction assays and found that 5/10 (50%) of selected isolates exhibited a synergistic interaction with 0.02–0.41 FICI values. This present study demonstrated the potential application of novel AMPs as an adjunctive treatment with clarithromycin against drug resistant Mab infection.

Correlation between clarithromycin resistance, virulence factors and clinical characteristics of the disease in Helicobacter pylori infected patients in Shahrekord, Southwest Iran

The purpose of this study was to determine the mutations associated with clarithromycin resistance in Helicobacter pylori strains isolated from biopsy samples that were collected from the endoscopic ward of Shahrekord Hajar teaching Hospital and also to study the frequency of virulence factor and their correlation and pathological findings with clarithromycin resistance during the years 2019–2020. In this cross-sectional descriptive study, 152 patients with Helicobacter pylori infection were considered, and then, two common A2142G and A2143G mutations in the 23SrRNA gene associated with resistance were analyzed by Real-time PCR (Taq man). The presence of vacA, iceA1, iceA2, cagA, babA2, and oipA virulence genes was investigated by PCR and electrophoresis in 8% polyacrylamide gel. Then, data were analyzed using the relevant statistical tests. In this study, the frequency of Helicobacter pylori was 76% and the frequency of mutant isolates was 57.2%. The frequencies of A2142G and A2143G point mutations were 42.1% and 28.3%. There was a significant correlation among oipA, vacA, and iceA1 virulence factors, type of disease, chronic inflammatory score, and glandular atrophy with the antibiotic resistance to clarithromycin. There was no significant correlation between the age and sex of the patients with antibiotic resistance. According to the results of this study, it seems that the use of clarithromycin to combat this bacterium should be limited.

Assessment of antimycobacterial activities of pure compounds extracted from Thai medicinal plants against clarithromycin-resistant Mycobacterium abscessus

Background Infection with Mycobacterium abscessus is usually chronic and is associated with clarithromycin resistance. Increasing drug resistance is a major public-health problem and has led to the search for new antimycobacterial agents. We evaluated the antimycobacterial activity, toxicity, and synergistic effects of several plant secondary metabolites against M. abscessus. Methods Twenty-three compounds were evaluated for antimycobacterial activity against thirty M. abscessus clinical isolates by broth microdilution to determine their minimum inhibitory concentration (MIC) values. Toxicity was evaluated using red and white blood cells (RBCs and WBCs). The compounds were used in combination with clarithromycin to investigate the possibility of synergistic activity. Results Five out of twenty-three compounds (RL008, RL009, RL011, RL012 and RL013) exhibited interesting antimycobacterial activity against M. abscessus, with MIC values ranging from <1 to >128 μg/mL. These extracts did not induce hemolytic effect on RBCs and displayed low toxicity against WBCs. The five least-toxic compounds were tested for synergism with clarithromycin against seven isolates with inducible clarithromycin resistance and seven with acquired clarithromycin resistance. The best synergistic results against these isolates were observed for RL008 and RL009 (8/14 isolates; 57%). Conclusions This study demonstrated antimycobacterial and synergistic activities of pure compounds extracted from medicinal plants against clarithromycin-resistant M. abscessus. This synergistic action, together with clarithromycin, may be effective for treating infections and should be further studied for the development of novel antimicrobial agents.

Culture and Susceptibility of Levofloxacin Resistant H.pylori

Background Antibiotic resistance in Helicobacter pylori is the major cause of eradication failure. Prevalence of H.pylori antibiotic resistance is increasing worldwide, and it is the main factor affecting efficacy of current therapeutic regimens. Our aim is to investigate H.pylori resistant patients toward Levofloxacin and detect the most effective antibiotic in eradication of H.pylori. Objective To investigate H.pylori resistant patients toward Levofloxacin including regimens and to detect the most effective antibiotic in H.pylori eradication. Patients and Methods The present study aimed to investigate the Susceptibility of Levofloxacin Resistant H.pylori in patients who had been diagnosed and received any regimen including Levofloxacin and still signs and symptoms of H.pylori infection not releaved and after proper time of stoppage of PPI and antibiotics H.pylori Ag in stool still positive at the period from January 2019 to February 2020. Results In the present study we found a wide spectrum of resistance to rates of H. pylori, from nearly negligible rates of Rifampicin (0%), Imipenem (0%), Cefotaxime (2%), Tetracycline (6%), Doxycycline(10%), and Amoxicillin(38%). To high rates resistance to Metronidazole (100%), Erythromycin (72%), Clarithromycin (68%), Azithromycin (60%), Ciprofloxacin (52%), and Levofloxacin (48%). Conclusion Helicobacter pylori is the most common chronic bacterial infection in humans. Antibiotic resistance is a major issue nowadays. Prior use of macrolide antibiotics or metronidazole appears to increase the risk of H. pylori resistance. Clarithromycin resistance appears to be an "absolute" condition that can not be overcome by increasing the macrolide dose. Levofloxacin resistance seems to be increasing. Culture and susceptibility should be done before starting second line treatment.

Minimum-inhibitory-concentration (MIC) distributions of routinely tested antimicrobials, and rifabutin, eravacycline, delafloxacin, clofazimine, and bedaquiline for Mycobacterium fortuitum

Rapid-growing-mycobacteria (RGM) are environmental organisms, which may cause infections in patients with particular risk factors. Whilst members of the Mycobacterium abscessus complex (MabsC) are the most commonly identified RGM from patient samples, Mycobacterium fortuitum is the second most commonly identified RGM in our setting in Singapore (1, 2). Although less common, the spectrum of clinical infections is similar (3). Treatment guidelines are not species-specific but it is generally recommended that combination antibiotics be used based on susceptibility testing results (4, 5). Due to the low incidence of infections caused by M. fortuitum , clinical evidence is limited, and clinical efficacy of individual antibiotics for treatment is unclear. The majority of the M. fortuitum complex have also been reported to have inducible clarithromycin resistance due to the erm (39) gene (6), indicating the need for alternative antibiotics to treat these infections.