Generation of resistant mutants of Mycobacterium chelonae and Mycobacterium fortuitum after exposure to subinhibitory concentrations of clarithromycin and moxifloxacin

Surgical cure of clarithromycin resistant Mycobacterium chelonae breast implant infection: A case report and review of the literature

Clusters of patients who obtain cosmetic surgeries abroad have developed surgical site infections due to rapid growing non-tuberculous mycobacteria (NTM). These are usually treated with a combination of surgery and months of anti-mycobacterial therapy, but poor outcomes, including permanent scarring are common. We present a case of a 36-year-old female who developed a clarithromycin-resistant M. chelonae (CRMC) infection after undergoing breast augmentation in the Dominican Republic. She underwent debridement and explant of her silicone implants, but due to a series of complications including discordant antimicrobial susceptibility testing profiles, GI side effects, and then pregnancy, she was unable to receive typical multidrug anti-mycobacterial therapy after surgery. She received close clinical follow up and demonstrated full recovery without any evidence of recurrence of infection at 9 months of follow up. We searched the literature for cases of NTM surgical site infection after breast surgery. To our knowledge, this is the first case report of confirmed NTM breast implant infection being cured with surgery alone, and only the second report of clarithromycin resistant M. chelonae in a patient without disseminated infection or pre-exposure to macrolides. The increasing prevalence of drug resistant NTM infections is an emerging concern for clinicians treating patients with complications related to medical tourism.

Bacterial antibiotic resistance development and mutagenesis following exposure to subinhibitory concentrations of fluoroquinolones in vitro: a systematic review of the literature

BACKGROUND

Understanding social and scientific drivers of antibiotic resistance is critical to help preserve antibiotic efficacy. These drivers include exposure to subinhibitory antibiotic concentrations in the environment and clinic.

OBJECTIVES

To summarize and quantify the relationship between subinhibitory fluoroquinolone exposure and antibiotic resistance and mutagenesis to better understand resistance patterns and mechanisms.

METHODS

Following PRISMA guidelines, PubMed, Web of Science and Embase were searched for primary in vitro experimental studies on subinhibitory fluoroquinolone exposure and bacterial antibiotic resistance and mutagenesis, from earliest available dates through to 2018 without language limitation. A specifically developed non-weighted tool was used to assess risk of bias.

RESULTS

Evidence from 62 eligible studies showed that subinhibitory fluoroquinolone exposure results in increased resistance to the selecting fluoroquinolone. Most increases in MIC were low (median minimum of 3.7-fold and median maximum of 32-fold) and may not be considered clinically relevant. Mechanistically, resistance is partly explained by target mutations but also changes in drug efflux. Collaterally, resistance to other fluoroquinolones and unrelated antibiotic classes also develops. The mean ± SD quality score for all studies was 2.6 ± 1.8 with a range of 0 (highest score) to 7 (lowest score).

CONCLUSIONS

Low and moderate levels of resistance and efflux changes can create an opportunity for higher-level resistance or MDR. Future studies, to elucidate the genetic regulation of specific resistance mechanisms, and increased policies, including surveillance of low-level resistance changes or genomic surveillance of efflux pump genes and regulators, could serve as a predictor of MDR development.