Non-tuberculous cutaneous mycobacterioses

Design and Validation of a Simplified Method to Determine Minimum Bactericidal Concentration in Nontuberculous Mycobacteria

BACKGROUND/OBJECTIVES

Nontuberculous mycobacteria (NTM) infections are rising, particularly those by Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MAB). Treating NTM infections is challenging due to their poor response to antibiotics. This study aimed to optimize the treatment of NTM infection by selecting antibiotics with bactericidal activity for combination therapy. To do this, we used the minimum bactericidal concentration (MBC) determination approach to define bactericidal or bacteriostatic activity. We developed three main objectives: validate a new method to determine MBC based on a reincubation method, determine MBC values of 229 NTM clinical isolates using the reincubation method, and evaluate antibiotic stability in preincubated microtiter plates.

METHODS

First, we assessed the stability of the antibiotics included in SLOWMYCOI Sensititre™ microtiter plates. Five strains of MAC were studied comparing the minimum inhibitory concentrations (MICs) of those preincubated for seven days vs. non-incubated plates. Then, we evaluated the percentage of reproducibility of MBC values using two methods, reincubation and subculturing (standard or traditional method) in 30 MAC isolates. Finally, we validated the reincubation method and prospectively determined the MBC values of the 229 NTM clinical strains.

RESULTS

Antibiotic stability: The MIC was equivalent after 7 and 14 days for all the antibiotics, except rifampicin, for which the MIC increased by 2- to 3-fold after preincubation. Reincubation method: The percentage of reproducibility of the MBC values between the two methods was 95.2% (range 76.6% to 100%). Prospective validation: MBC/MIC ratios revealed differential bactericidal activity for most antibiotics according to the different species, being bactericidal in M. avium and Mycobacterium xenopi, and predominantly bacteriostatic in MAB.

CONCLUSIONS

Preincubation of Sensititre™ microtiter plates did not alter the MIC values of the antibiotics included except for rifampicin, suggesting a loss of activity. MBC determination can be easily performed by the Reincubation method presented. MBC values provide useful additional information regarding MIC values since the MBC/MIC ratio reveals whether antibiotics have bactericidal or bacteriostatic activity according to the species, which is pivotal for selecting the most adequate antibiotic combination to ensure efficient treatment management.

Cutaneous Atypical Mycobacterial Infections: A Brief Review

Nontuberculous mycobacterial (NTM) infections are increasingly recognized, particularly in tropical regions and are often found in immunocompetent individuals. These infections are emerging as significant health concerns, especially pulmonary NTM, which is reported more frequently and is known to be associated with hospital environments. While pulmonary NTM infections are on the rise, partly due to drug resistance and possible patient-to-patient transmission, there is no current evidence indicating an increase in cutaneous NTM infections. The clinical manifestations of NTM infections, except for well-known entities like Buruli ulcer and fish tank granuloma, are diverse and nonspecific, often mimicking other chronic infections. History of minor trauma at the site of infection can be misleading and may complicate the diagnosis of cutaneous NTM. Surgical-site and port-site NTM infections typically present with erythema, edema, and abscesses and are commonly caused by rapidly growing mycobacteria like M. fortuitum and M. chelonae. These infections may not respond to standard antibiotics, suggesting the need for NTM-specific treatment. Diagnostically, histopathology may not be conclusive, and standard staining techniques often lack sensitivity. Molecular methods offer better speciation and drug resistance profiling for pulmonary NTM but are expensive and not widely available for cutaneous forms. The high cost and limited availability of diagnostic tools necessitate an empirical treatment approach, which is also recommended by the INDEX-Tb guidelines for extrapulmonary tuberculosis. Empirical treatment regimens for NTM, such as combinations of clarithromycin, doxycycline, and cotrimoxazole or fluoroquinolones, have shown promise, but there is a lack of rigorous studies to establish standardized treatments. Monitoring for adverse effects and continued evaluation of the causative organism is essential during empirical treatment, allowing for adjustment if the initial regimen fails.

Multiple Indolent Purplish Nodules and Plaques of the Extremities in an 85-year-old Man: A Quiz

Abstract is missing (Quiz)

Probing Dermal Immunity to Mycobacteria through a Controlled Human Infection Model

Cutaneous mycobacterial infections cause substantial morbidity and are challenging to diagnose and treat. An improved understanding of the dermal immune response to mycobacteria may inspire new therapeutic approaches. We conducted a controlled human infection study with 10 participants who received 2 × 106 CFUs of Mycobacterium bovis bacillus Calmette-Guérin (Tice strain) intradermally and were randomized to receive isoniazid or no treatment. Peripheral blood was collected at multiple time points for flow cytometry, bulk RNA sequencing (RNA-seq), and serum Ab assessments. Systemic immune responses were detected as early as 8 d postchallenge in this M. bovis bacillus Calmette-Guérin-naive population. Injection-site skin biopsies were performed at days 3 and 15 postchallenge and underwent immune profiling using mass cytometry and single-cell RNA-seq, as well as quantitative assessments of bacterial viability and burden. Molecular viability testing and standard culture results correlated well, although no differences were observed between treatment arms. Single-cell RNA-seq revealed various immune and nonimmune cell types in the skin, and communication between them was inferred by ligand-receptor gene expression. Day 3 communication was predominantly directed toward monocytes from keratinocyte, muscle, epithelial, and endothelial cells, largely via the migration inhibitory factor pathway and HLA-E-KLRK1 interaction. At day 15, communication was more balanced between cell types. These data reveal the potential role of nonimmune cells in the dermal immune response to mycobacteria and the utility of human challenge studies to augment our understanding of mycobacterial infections.

Severe Cutaneous Manifestation of Malignant Syphilis in a Patient with Behçet's Uveitis: A Case Report

Introduction

Syphilis exhibits a wide range of clinical presentations, mimicking various systemic and ocular diseases. Ocular syphilis, in particular, manifests with multiple presentations, ranging from anterior uveitis to panuveitis, making it a potential differential diagnosis for Behçet's uveitis. Here, we present a unique case of Behçet's panuveitis that was undergoing immunomodulatory therapy and was complicated by ocular syphilis. Notably, this case also featured rare cutaneous manifestations associated with secondary syphilis, commonly known as malignant syphilis.

Case Presentation

A 38-year-old Thai man with refractory end-stage Behçet's panuveitis reported a maculopapular rash accompanied by increased intraocular inflammation. The escalation of immunomodulatory therapy, intended to manage the provisional diagnosis of active ocular and cutaneous Behçet's disease, resulted in clinical deterioration, with the rash transforming into multiple noduloulcerative lesions. Despite negative serologic tests for syphilis at baseline before initiating immunomodulatory therapy, syphilis infection was eventually diagnosed following reevaluation and the observation of spirochetes in a skin biopsy specimen. The patient was treated with intravenous penicillin G, resulting in an improvement in intraocular inflammation and resolution of noduloulcerative rashes.

Conclusion

Intraocular inflammation and mucocutaneous lesions in syphilis can mimic the presentation of Behçet's disease. The introduction of immunomodulatory therapy may alter the clinical picture, leading to a severe and atypical presentation. A high index of suspicion for reevaluating serologic tests or performing tissue biopsies is warranted for an accurate diagnosis.

Treatment of non-tuberculosis mycobacteria skin infections

Non-tuberculosis mycobacteria (NTM) skin infections have become increasingly prevalent in recent years, presenting a unique challenge in clinical management. This review explored the complexities of NTM infections localized to the superficial tissues and provided valuable insights into the optimal therapeutic strategies. The antibiotic selection should base on NTM species and their susceptibility profiles. It is recommended to adopt a comprehensive approach that considers the unique characteristics of superficial tissues to improve treatment effectiveness and reduce the incidence of adverse reactions, infection recurrence, and treatment failure. Infection control measures, patient education, and close monitoring should complement the treatment strategies to achieve favorable outcomes in managing NTM skin infections. Further efforts are warranted to elucidate factors and mechanisms contributing to treatment resistance and relapse. Future research should focus on exploring novel treatment options, innovative drug development/delivery platforms, and precise methodologies for determining therapeutic duration. Longitudinal studies are also needed to assess the long-term safety profiles of the integrated approaches.

Effectiveness and safety of multidrug therapy containing clofazimine for paucibacillary leprosy and clarithromycin for rifampicin-resistant leprosy: a systematic review and meta-analysis

Introduction

The present study aimed to evaluate leprosy cure and relapse rates as primary outcomes related to two additional strategies for leprosy treatment: clofazimine for paucibacillary (PB) leprosy patients and clarithromycin for patients with rifampicin-resistant leprosy.

Methods

We conducted two systematic reviews (protocols CRD42022308272 and CRD42022308260). We searched the PubMed, EMBASE, Web of Science, Scopus, LILACS, Virtual Health Library and Cochrane Library databases, registers of clinical trial databases and gray literature. We included clinical trials evaluating the addition of clofazimine to PB leprosy treatment and the use of clarithromycin for treating patients with rifampicin-resistant leprosy. Risk of bias (RoB) in randomized clinical trials was assessed by the RoB 2 tool and that in non-randomized clinical trials was assessed by the ROBINS-I tool; and the certainty of the evidence was assessed by the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. A meta-analysis of dichotomous outcomes was performed.

Results

For clofazimine, four studies were included. Cure and relapse rates were not different with the addition of clofazimine to PB leprosy treatment and demonstrated very low certainty of evidence. For clarithromycin, six studies were included. Considerable heterogeneity resulted from the difference between comparators, and studies showed no difference in the assessed outcomes with the addition of clarithromycin to rifampicin-resistant leprosy treatment. Mild adverse events were reported for both drugs but did not significantly impact treatment.

Discussion

The effectiveness of both drugs still needs to be determined. Adding clofazimine to PB leprosy treatment may reduce the repercussions of an incorrect operational classification with no apparent relevant side effects.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022308272; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022308260, identifier: CRD42022308272; CRD42022308260.

Protective Efficacy of BCG Vaccine against Mycobacterium leprae and Non-Tuberculous Mycobacterial Infections

The genus mycobacterium includes several species that are known to cause infections in humans. The microorganisms are classified into tuberculous and non-tuberculous based on their morphological characteristics, defined by the dynamic relationship between the host defenses and the infectious agent. Non-tuberculous mycobacteria (NTM) include all the species of mycobacterium other than the ones that cause tuberculosis (TB). The group of NTM contains almost 200 different species and they are found in soil, water, animals—both domestic and wild—milk and food products, and from plumbed water resources such as sewers and showerhead sprays. A systematic review of Medline between 1946 and 2014 showed an 81% decline in TB incidence rates with a simultaneous 94% increase in infections caused by NTM. Prevalence of infections due to NTM has increased relative to infections caused by TB owing to the stringent prevention and control programs in Western countries such as the USA and Canada. While the spread of typical mycobacterial infections such as TB and leprosy involves human contact, NTM seem to spread easily from the environment without the risk of acquiring from a human contact except in the case of M. abscessus in patients with cystic fibrosis, where human transmission as well as transmission through fomites and aerosols has been recorded. NTM are opportunistic in their infectious processes, making immunocompromised individuals such as those with other systemic infections such as HIV, immunodeficiencies, pulmonary disease, or usage of medications such as long-term corticosteroids/TNF-α inhibitors more susceptible. This review provides insight on pathogenesis, treatment, and BCG vaccine efficacy against M. leprae and some important NTM infections.