Nontuberculous mycobacterial infections of the lower extremities: A 15-year experience

Epidemiology, clinical characteristics, and outcomes of nontuberculous mycobacterial skin, soft tissue, and bone infections from a single center over a 10-year period

Introduction

Non-tuberculous mycobacteria (NTM) cause a wide variety of clinical syndromes. Data guiding diagnosis and treatment of NTM skin and soft tissue infections (SSTI) and bone infections are limited. We sought to better understand SSTI and bone infections caused by NTM.

Methods

All NTM clinical isolates recovered at Brooke Army Medical Center from 2012 to 2022 were screened; SSTI and bone isolates were included. Electronic health records were reviewed for epidemiologic, microbiologic, and clinical data. Infections were defined as recovery of one or more NTM isolate from skin, soft tissue, or bone cultures with a corresponding clinical syndrome.

Results

Forty isolates of skin, soft tissue, or bone origin from 29 patients were analyzed. Twenty (69 %) patients, majority female (14/20, 70 %), had infecting isolates, most commonly secondary to surgery (35 %) or trauma (35 %). Six of 20 (30 %) had bone infections. Time from symptom onset to isolate recovery was a median 61 days (IQR 43-95). Eight (40 %) had combined medical/surgical therapy, 8 (40 %) had surgery alone, and 4 (20 %) had medical therapy alone. M. abscessus was more frequently isolated from patients with true infections.

Conclusions

Data supporting diagnosis and treatment decisions in NTM SSTI/bone infections is sparse. In this study the majority of NTM isolated were true infections. We confirm that surgery and trauma are the most common routes of exposure. The delay between symptom onset and directed therapy and the wide variety of treatment regimens highlight a need for additional studies delineating criteria for diagnosis and treatment.

Comparative genome analysis reveals high-level drug resistance markers in a clinical isolate of Mycobacterium fortuitum subsp. fortuitum MF GZ001

Introduction

Infections caused by non-tuberculosis mycobacteria are significantly worsening across the globe. M. fortuitum complex is a rapidly growing pathogenic species that is of clinical relevance to both humans and animals. This pathogen has the potential to create adverse effects on human healthcare.

Methods

The MF GZ001 clinical strain was collected from the sputum of a 45-year-old male patient with a pulmonary infection. The morphological studies, comparative genomic analysis, and drug resistance profiles along with variants detection were performed in this study. In addition, comparative analysis of virulence genes led us to understand the pathogenicity of this organism.

Results

Bacterial growth kinetics and morphology confirmed that MF GZ001 is a rapidly growing species with a rough morphotype. The MF GZ001 contains 6413573 bp genome size with 66.18 % high G+C content. MF GZ001 possesses a larger genome than other related mycobacteria and included 6156 protein-coding genes. Molecular phylogenetic tree, collinearity, and comparative genomic analysis suggested that MF GZ001 is a novel member of the M. fortuitum complex. We carried out the drug resistance profile analysis and found single nucleotide polymorphism (SNP) mutations in key drug resistance genes such as rpoB, katG, AAC(2')-Ib, gyrA, gyrB, embB, pncA, blaF, thyA, embC, embR, and iniA. In addition, the MF GZ001strain contains mutations in iniA, iniC, pncA, and ribD which conferred resistance to isoniazid, ethambutol, pyrazinamide, and para-aminosalicylic acid respectively, which are not frequently observed in rapidly growing mycobacteria. A wide variety of predicted putative potential virulence genes were found in MF GZ001, most of which are shared with well-recognized mycobacterial species with high pathogenic profiles such as M. tuberculosis and M. abscessus.

Discussion

Our identified novel features of a pathogenic member of the M. fortuitum complex will provide the foundation for further investigation of mycobacterial pathogenicity and effective treatment.

Difficulty in Diagnosis and Management of Musculoskeletal Nontuberculous Mycobacterial Infections

We describe two cases of musculoskeletal nontuberculous mycobacterial (NTM) infection resulting in undesirable outcomes. These organisms can be difficult to identify and treat, potentially leading to significant morbidity. NTM should remain on the differential for culture negative bone and joint infections, especially with a prior surgical history or environmentally-acquired injuries.

•

There is considerable difficulty in diagnosing NTM orthopedic infections.

•

These infections can be prolonged and progressive.

•

Consider NTM infection with negative cultures and failure of routine antibacterials.

•

Surgical debridement is essential in combination with antimycobacterials.

•

Treatment should be determined after culture results yield drug susceptibilities.

Phenotypic and genomic hallmarks of a novel, potentially pathogenic rapidly growing Mycobacterium species related to the Mycobacterium fortuitum complex

Previously, we have identified a putative novel rapidly growing Mycobacterium species, referred to as TNTM28, recovered from the sputum of an apparently immunocompetent young man with an underlying pulmonary disease. Here we provide a thorough characterization of TNTM28 genome sequence, which consists of one chromosome of 5,526,191 bp with a 67.3% G + C content, and a total of 5193 predicted coding sequences. Phylogenomic analyses revealed a deep-rooting relationship to the Mycobacterium fortuitum complex, thus suggesting a new taxonomic entity. TNTM28 was predicted to be a human pathogen with a probability of 0.804, reflecting the identification of several virulence factors, including export systems (Sec, Tat, and ESX), a nearly complete set of Mce proteins, toxin-antitoxins systems, and an extended range of other genes involved in intramacrophage replication and persistence (hspX, ahpC, sodA, sodC, katG, mgtC, ClpR, virS, etc.), some of which had likely been acquired through horizontal gene transfer. Such an arsenal of potential virulence factors, along with an almost intact ESX-1 locus, might have significantly contributed to TNTM28 pathogenicity, as witnessed by its ability to replicate efficiently in macrophages. Overall, the identification of this new species as a potential human pathogen will help to broaden our understanding of mycobacterial pathogenesis.

Nontuberculous mycobacterial infection of the knee after arthrocentesis for idiopathic hemarthrosis: A case report

Introduction

Nontuberculous mycobacterial (NTM) infections of the musculoskeletal system are uncommon. Such infections are typically acquired by direct inoculation after penetrating trauma, surgical procedures, or needle injections. There are no reported cases of NTM infection after arthrocentesis for idiopathic hemarthrosis of the knee. Here we report a case of NTM infection in the knee that developed after arthrocentesis for idiopathic hemarthrosis of the knee.

Presentation of case

The patient was an 85-year-old woman who experienced swelling of the left knee. An arthrocentesis was carried out, and hemarthrosis was found. The patient was referred to our hospital for repeated recurrence of hematoma of the knee. Significant swelling was observed in the suprapatellar sac. Magnetic resonance imaging examination revealed a mass at the suprapatellar sac. Laboratory data showed elevation of inflammatory markers. Debridement was performed under arthroscopy and samples were collected for culture. Although routine microbiological cultures were negative, the patient continued to experience knee swelling and laboratory data showed high C-reactive protein levels. Therefore, open debridement was carried out. At 4 weeks after the first surgical treatment, intraoperative cultures yielded Mycobacterium intracellulare. At this point, we diagnosed septic arthritis of the knee due to NTM infection. The patient showed an excellent prognosis with three-drug medical treatment for 1 year.

Conclusion

Clinically, diagnosis of septic arthritis due to NTM infection is not easy. Because selection of examination depends on clinical suspicion, NTM infections should be considered for patients with elevation of inflammatory markers after episodes of surgical procedures, and/or needle injections.

•

・Nontuberculous mycobacterial (NTM) infections of the musculoskeletal system are uncommon.

•

・A case of NTM infection in the knee that developed after arthrocentesis.

•

・NTM infections should be considered for patients with elevation of inflammatory markers after needle injections.

A living donor kidney transplant recipient with mycobacterium senegalense bacteremia: A case report

Mycobacterium senegalense is primarily known in sub-Saharan Africa to cause bovine farcy, a chronic granulomatous inflammation of the skin and lymphatics in cows. Reports of M. senegalense are rare among humans. We report a unique case of M. senegalense bloodstream infection in a living donor kidney transplant recipient with multiple possible sources of infection.

Skin and Soft Tissue Infections in Non-Human Immunodeficiency Virus Immunocompromised Hosts

Skin and soft tissue infections among the non-human immunodeficiency virus infected immunosuppressed population are a serious and growing concern. Many pathogens can cause cutaneous infections in these patients owing to the highly varied and profound immune deficits. Although patients can be infected by typical organisms, the diversity and antimicrobial-resistant nature of the organisms causing these infections result in significant morbidity and mortality. The diagnostic approach to these infections in immunocompromised hosts can differ dramatically depending on the potential causative organisms. An understanding of new immunosuppressive treatments and evolving antimicrobial resistance patterns are required to optimally manage these difficult cases.

Mycobacterium abscessus Prosthetic Joint Infections of the Knee

M. abscessus complex prosthetic joint infections (PJI) of the knee are rare. We present a patient with an M. abscessus subsp. massiliense, a nontuberculous mycobacterium (NTM), peri-prosthetic knee infection who presented with wound drainage followed by sepsis. The published peer-reviewed literature on knee PJIs due to this organism is reviewed to highlight its clinical presentation,symptomatology, microbiology, surgical interventions, antimicrobial regimens, and outcomes.