Treatment of infections caused by nontuberculous mycobacteria

Clinical presentation and treatment outcomes of extrapulmonary nontuberculous mycobacterial infections with rapid and slow growth rates in Cali, Colombia

INTRODUCTION

The increasing prevalence of extrapulmonary nontuberculous mycobacterial (NTM) infections poses significant challenges in clinical management due to their inherent drug resistance, the need for prolonged antibiotic regimens and the complexities associated with surgical management. Although these infections are infrequent in daily clinical practice, detailed information on associated clinical outcomes is lacking in the local literature.

MATERIALS AND METHODS

This descriptive observational study examined 17 patients with extrapulmonary NTM infection from the General Mycobacteria Registry of Fundación Valle del Lili University Hospital (FVL), a leading reference care center located in Cali, a city in southwestern Colombia. Notably, Cali is classified as a high-risk area for tuberculosis. The study reviewed a total of 391 patients between 2007 and 2021.

RESULTS

A predominance of women with a history of cosmetic surgery was observed, with the skin being the most common site of involvement, especially for M. fortuitum complex and M. abscessus complex. Clarithromycin based therapy was given to 14/18 (82.3%) of the patients. The mean duration of treatment was 4-6 months, for a cure rate of 15/17 (88.2%).

CONCLUSION

The treatment regimens implemented mostly align with the literature recommendations. However, it is essential to note that while the observed cure rate exceeds 80%, this assertion is tempered by the limitation imposed by the lack of confirmatory imaging in some cases. A contributing factor to the higher cure rate observed in this study may be the use of more extensive surgical interventions, with some patients undergoing more than one procedure. Given the limited number of case series on extrapulmonary nontuberculous mycobacterial infections, these findings emphasize the potential importance of surgical management in achieving higher cure rates. The observed cure rate suggests potentially better clinical management of these infections in our region and underscores the need for future research to understand the factors contributing to this comparative therapeutic success.

New antibiofilm strategies for the management of nontuberculous mycobacteria diseases

INTRODUCTION

Nontuberculous mycobacteria (NTM) represent a group of microorganisms comprising more than 190 species. NTM infections have increased recently, and their treatment is a major challenge because to their resistance to conventional treatments. This review focuses on innovative strategies aimed at eradicating NTM biofilms, a critical factor in their resistance. Important areas addressed include biofilm formation mechanisms, current therapeutic challenges, and novel treatment approaches. The main objective is to compile and analyze information on these emerging strategies, identifying pivotal research directions and recent advancements.

AREAS COVERED

A review of the scientific literature was conducted to identify emerging novel therapies for the treatment of NTM infections and to explore potential synergies with existing treatments.

EXPERT OPINION

Experts highlights a limited understanding of optimal treatment regimens, often supported by insufficient scientific evidence. Current therapies are typically prolonged, involve multiple antibiotics with adverse effects, and frequently do not achieve patient cure. Certain species are even considered virtually impossible to eradicate. A thorough understanding of these new approaches is imperative for improving patients outcomes. This review provides a robust foundation for developing of more effective antibacterial strategies, which are essential because of the increasing incidence of NTM infections and the limitations of existing therapies.

Prevalence of resistance to macrolides and aminoglycosides in Mycobacterium avium, M. abscessus, and M. chelonae identified in the Laboratorio Nacional de Referencia of Colombia from 2018 to 2022

Introduction

The Mycobacterium chelonae species and the M. avium and M. abscessus complexes are emerging pathogens that cause mycobacteriosis. Treatment depends on the species and subspecies identified. The drugs of choice are macrolides and aminoglycosides. However, due to the resistance identified to these drugs, determining the microbe’s sensitivity profile will allow clinicians to improve the understanding of the prognosis and evolution of these pathologies.

Objective

To describe the macrolide and aminoglycoside susceptibility profile of cultures identified by Colombia’s Laboratorio Nacional de Referencia de Mycobacteria from 2018 to 2022, as Mycobacterium avium complex, M. abscessus complex, and M. chelonae. Materials and methods. This descriptive study exposes the susceptibility profile to macrolides and aminoglycosides of cultures identified as M. avium complex, M. abscessus complex, and M. chelonae using the GenoType® NTM-DR method.

Materials and methods

This descriptive study exposes the susceptibility profile to macrolides and aminoglycosides of cultures identified as M. avium complex, M. abscessus complex, and M. chelonae using the GenoType® NTM-DR method.

Results

We identified 159 (47.3 %) cultures as M. avium complex, of which 154 (96.9 %) were sensitive to macrolides, and 5 (3.1 %) were resistant; all were sensitive to aminoglycosides. From the 125 (37.2 %) cultures identified as M. abscessus complex, 68 (54.4 %) were sensitive to macrolides, 57 (45.6 %) were resistant to aminoglycosides, and just one (0.8 %) showed resistance to aminoglycosides. The 52 cultures (15.5 %) identified as M. chelonae were sensitive to macrolides and aminoglycosides.

Conclusions

The three studied species of mycobacteria have the least resistance to Amikacin. Subspecies identification and their susceptibility profiles allow the establishment of appropriate treatment schemes, especially against M. abscessus.

Rapid growth atypical mycobacteria infection associated with growth hormone injections: a case report

Introduction

Infections caused by fast growing mycobacteria have increased markedly worldwide. They are normally associated with trauma, surgery or cosmetic interventions. Paraguay has a deficit in sanitary control including clinics, private practices, and aesthetic centres. This situation is accompanied by the easy access to drugs, which leads to the performance of exclusively medical aesthetic procedures by people without professional knowledge or training.

Case report

A 26-year-old female patient comes to a medical consultation with pain and bruising in the abdominal area with more than 3 months of progression, without fever or apparent cause. Later, she confessed to the application of subcutaneous injections of ‘growth hormones’ at the gym. Excisional biopsy of the lesions was carried out for anatomopathological and microbiological studies. In addition, the use of polymerase chain reaction analysis was indicated because of the strong suspicion of an atypical mycobacterial infection. The Ziehl-Neelsen staining was negative for BAAR, and the PAS-Hematoxylin negative for fungal elements. When performing the culture, the growth of atypical mycobacteria was observed on chocolate and blood agar medium culture. Through the polymerase chain reaction study, it was possible to identify the atypical mycobacterium as ‘Mycobacterium abscessus’.

Conclusion

The irresponsible application of medications by people without professional authorization or biosafety precautions can lead to the development atypical infections that are difficult to diagnose and treat. This situation could lead to serious complications and even death.

Ribosome Protection as a Mechanism of Lincosamide Resistance in Mycobacterium abscessus

Mycobacterium abscessus has emerged as a successful pathogen owing to its intrinsic drug resistance. Macrolide and lincosamide antibiotics share overlapping binding sites within the ribosome and common resistance pathways. Nevertheless, while M. abscessus is initially susceptible to macrolides, they are completely resistant to the lincosamide antibiotics. Here, we have used RNA sequencing to determine the changes in gene expression in M. abscessus upon exposure to the lincosamide, clindamycin (CLY). We show that Mab_1846, encoding a putative ARE-ABCF protein, was upregulated upon exposure to macrolides and lincosamides but conferred resistance to CLY alone. A Mycobacterium smegmatis homologue of Mab_1846, Ms_5102, was similarly found to be required for CLY resistance in M. smegmatis. We demonstrate that Ms5102 mediates CLY resistance by directly interacting with the ribosomes and protecting it from CLY inhibition. Additional biochemical characterization showed that ribosome binding is not nucleotide dependent, but ATP hydrolysis is required for dissociation of Ms5102 from the ribosome as well as for its ability to confer CLY resistance. Finally, we show that in comparison to the macrolides, CLY is a potent inducer of Mab_1846 and the whiB7 regulon, such that exposure of M. abscessus to very low antibiotic concentrations induces a heightened expression of erm41, hflX, and Mab_1846, which likely function together to result in a particularly antibiotic-resistant state.

Repurposing Avermectins and Milbemycins against Mycobacteroides abscessus and Other Nontuberculous Mycobacteria

Infections caused by nontuberculous mycobacteria (NTM) are increasing worldwide, resulting in a new global health concern. NTM treatment is complex and requires combinations of several drugs for lengthy periods. In spite of this, NTM disease is often associated with poor treatment outcomes. The anti-parasitic family of macrocyclic lactones (ML) (divided in two subfamilies: avermectins and milbemycins) was previously described as having activity against mycobacteria, including Mycobacterium tuberculosis, Mycobacterium ulcerans, and Mycobacterium marinum, among others. Here, we aimed to characterize the in vitro anti-mycobacterial activity of ML against a wide range of NTM species, including Mycobacteroides abscessus. For this, Minimum Inhibitory Concentration (MIC) values of eight ML were determined against 80 strains belonging to nine different NTM species. Macrocyclic lactones showed variable ranges of anti-mycobacterial activity that were compound and species-dependent. Milbemycin oxime was the most active compound, displaying broad-spectrum activity with MIC lower than 8 mg/L. Time kill assays confirmed MIC data and showed bactericidal and sterilizing activity of some compounds. Macrocyclic lactones are available in many formulations and have been extensively used in veterinary and human medicine with suitable pharmacokinetics and safety properties. This information could be exploited to explore repurposing of anti-helminthics for NTM therapy.

Metal center ion effects on photoinactivating rapidly growing mycobacteria using water-soluble tetra-cationic porphyrins

Rapidly growing mycobacteria (RGM) are pathogens that belong to the mycobacteriaceae family and responsible for causing mycobacterioses, which are infections of opportunistic nature and with increasing incidence rates in the world population. This work evaluated the use of six water-soluble cationic porphyrins as photosensitizers for the antimicrobial photodynamic therapy (aPDT) of four RGM strains: Mycolicibacterium fortuitum, Mycolicibacterium smeagmatis, Mycobacteroides abscessus subs. Abscessus, and Mycobacteroides abscessus subsp. massiliense. Experiments were conducted with an adequate concentration of photosensitizer under white-light irradiation conditions over 90 min and the results showed that porphyrins 1 and 2 (M = 2H or Zn^II ion) were the most effective and significantly reduced the concentration of viable mycobacteria. The present work shows the result is dependent on the metal-center ion coordinated in the cationic porphyrin core. Moreover, we showed by atomic force microscopy (AFM) the possible membrane photodamage caused by reactive oxygen species and analyzed the morphology and adhesive force properties. Tetra-positively charged and water-soluble metalloporphyrins may be promising antimycobacterial aPDT agents with potential applications in medical clinical cases and bioremediation.

Opportunistic infections in pediatrics: when to suspect and how to approach

OBJECTIVES

To describe the characteristics of opportunistic infections in pediatrics regarding their clinical aspects, as well as the diagnostic strategy and treatment.

SOURCE OF DATA

Non-systematic review of literature studies in the PubMed database.

SYNTHESIS OF DATA

Opportunistic infections caused by non-tuberculous mycobacteria, fungi, Herpesvirae, and infections affecting individuals using immunobiological agents are analyzed. Because these are severe diseases with a rapid evolution, diagnostic suspicion should be early, associated with the patient's clinical assessment and history pointing to opportunistic infections. Whenever possible, samples of secretions, blood, and other fluids and tissues should be collected, with early therapy implementation.

CONCLUSIONS

Despite the improved diagnosis of opportunistic infections in recent years, they remain a challenge for pediatricians who are not used to these infections. They should raise the suspicion and start treating the case, but should also resort to specialists in the management of these infections to provide a better outcome for these patients, who still have high mortality.

High Levels of Intrinsic Tetracycline Resistance in Mycobacterium abscessus Are Conferred by a Tetracycline-Modifying Monooxygenase

Tetracyclines have been one of the most successful classes of antibiotics. However, its extensive use has led to the emergence of widespread drug resistance, resulting in discontinuation of use against several bacterial infections. Prominent resistance mechanisms include drug efflux and the use of ribosome protection proteins. Infrequently, tetracyclines can be inactivated by the TetX class of enzymes, also referred to as tetracycline destructases. Low levels of tolerance to tetracycline in Mycobacterium smegmatis and Mycobacterium tuberculosis have been previously attributed to the WhiB7-dependent TetV/Tap efflux pump. However, Mycobacterium abscessus is ∼500-fold more resistant to tetracycline than M. smegmatis and M. tuberculosis In this report, we show that this high level of resistance to tetracycline and doxycycline in M. abscessus is conferred by a WhiB7-independent tetracycline-inactivating monooxygenase, MabTetX (MAB_1496c). The presence of sublethal doses of tetracycline and doxycycline results in a >200-fold induction of MabTetX, and an isogenic deletion strain is highly sensitive to both antibiotics. Further, purified MabTetX can rapidly monooxygenate both antibiotics. We also demonstrate that expression of MabTetX is repressed by MabTetR_x, by binding to an inverted repeat sequence upstream of MabTetR_x; the presence of either antibiotic relieves this repression. Moreover, anhydrotetracycline (ATc) can effectively inhibit MabTetX activity in vitro and decreases the MICs of both tetracycline and doxycycline in vivo Finally, we show that tigecycline, a glycylcycline tetracycline, not only is a poor substrate of MabTetX but also is incapable of inducing the expression of MabTetX. This is therefore the first demonstration of a tetracycline-inactivating enzyme in mycobacteria. It (i) elucidates the mechanism of tetracycline resistance in M. abscessus, (ii) demonstrates the use of an inhibitor that can potentially reclaim the use of tetracycline and doxycycline, and (iii) identifies two sequential bottlenecks-MabTetX and MabTetR_x-for acquiring resistance to tigecycline, thereby reiterating its use against M. abscessus.