First case of Mycobacterium heckeshornense cavitary lung disease in the Latin America and Caribbean region

Cold Cas: reevaluating the occurrence of CRISPR/Cas systems in Mycobacteriaceae

Bacterial CRISPR/Cas systems target foreign genetic elements such as phages and regulate gene expression by some pathogens, even in the host. The system is a marker for evolutionary history and has been used for inferences in Mycobacterium tuberculosis for 30 years. However, knowledge about mycobacterial CRISPR/Cas systems remains limited. It is believed that Type III-A Cas systems are exclusive to Mycobacterium canettii and the M. tuberculosis complex (MTBC) of organisms and that very few of the >200 diverse species of non-tuberculous mycobacteria (NTM) possess any CRISPR/Cas system. This study sought unreported CRISPR/Cas loci across NTM to better understand mycobacterial evolution, particularly in species phylogenetically near the MTBC. An analysis of available mycobacterial genomes revealed that Cas systems are widespread across Mycobacteriaceae and that some species contain multiple types. The phylogeny of Cas loci shows scattered presence in many NTM, with variation even within species, suggesting gains/losses of these loci occur frequently. Cas Type III-A systems were identified in pathogenic Mycobacterium heckeshornense and the geological environmental isolate Mycobacterium SM1. In summary, mycobacterial CRISPR/Cas systems are numerous, Type III-A systems are unreliable as markers for MTBC evolution, and mycobacterial horizontal gene transfer appears to be a frequent source of genetic variation.

[Cavernous Nontuberculous Mycobacterial Lung Infection in an HIV-positive Patient]

Since we first described Mycobacterium heckeshornense, a rare species of mycobacteria in 2000, only 21 cases of infection with this mycobacterium have been described in humans. We relate the diagnosis and therapy of another case of this uncommon nontuberculous mycobacterium in an immune-suppressed patient.

A Comparative Genomics Approach for Shortlisting Broad-Spectrum Drug Targets in Nontuberculous Mycobacteria

Many members of nontuberculous mycobacteria (NTM) are opportunistic pathogens causing several infections in animals. The incidence of NTM infections and emergence of drug-resistant NTM strains are rising worldwide, emphasizing the need to develop novel anti-NTM drugs. The present study is aimed to identify broad-spectrum drug targets in NTM using a comparative genomics approach. The study identified 537 core proteins in NTM of which 45 were pathogen specific and essential for the survival of pathogens. Furthermore, druggability analysis indicated that 15 were druggable among those 45 proteins. These 15 proteins, which were core proteins, pathogen-specific, essential, and druggable, were considered as potential broad-spectrum candidates. Based on their locations in cytoplasm and membrane, targets were classified as drug and vaccine targets. The identified 15 targets were different enzymes, carrier proteins, transcriptional regulator, two-component system protein, ribosomal, and binding proteins. The identified targets could further be utilized by researchers to design inhibitors for the discovery of antimicrobial agents.

A case of pulmonary Mycobacterium heckeshornense infection in a healthy Japanese man

A 72-year-old man, healthy, smoker, with long-standing cough, was referred to our hospital and his chest X-ray (CXR) revealed a cavity lesion in the right upper lobe. Direct sputum smears, but not culture in solid medium, were positive for acid-fast bacilli (AFB) without tuberculosis DNA. The preliminary diagnosis was of a non-tuberculosis infection that progressed slowly, and the CXR showed the condition to worsen daily. Four years later, a commercialized mycobacteria growth indicator tube system was used to culture the colonies of AFB successfully in liquid medium, and the species Mycobacterium heckeshornense was identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. The patient responded well to triple therapy with rifampicin, ethambutol, and clarithromycin, the sputum cultures remained negative and the roentgenogram showed minor improvement over the following 6 months.

Species Distribution and Isolation Frequency of Nontuberculous Mycobacteria, Uruguay

Nontuberculous mycobacteria (NTM) increasingly are recognized as opportunistic pathogens of humans. NTM species distribution is well documented in Europe and North America, but data from other regions are scarce. We assessed NTM isolation frequency and species distribution in Uruguay during 2006–2018.

Pulmonary Mycobacterium heckeshornense infection in a healthy woman

Pulmonary infection due to Mycobacterium heckeshornense (M. heckeshornense) in healthy adults without underlying diseases is very rare and optimal treatments have not yet been established. A 39-year-old woman was admitted to our hospital for further examinations following the identification of a pulmonary cavitary nodule. Acid-fast bacilli were cultured from specimens obtained by bronchofiberscopy, and identified with M. heckeshornense using nucleotide sequencing. Antimycobacterial chemotherapy was effective temporarily, while the nodular lesion subsequently worsened. The patient underwent lobectomy and has not relapsed thus far. A lung specimen showed marked granulomatous inflammation with extensive caseous necrosis and the preservation of some parts of alveolar septa within caseous necrosis, indicating an exudative process and resistance to chemotherapy. M. heckeshornense is strongly pathogenic and switching to surgical intervention needs to be considered when chemotherapy is insufficient.