Rapidly Growing Mycobacteria

Epidemiology of Mycobacterium abscessus

BACKGROUND

Nontuberculous mycobacteria (NTM) are highly abundant in soil, dust, and water sources, making human-pathogen contact frequent and recurrent. NTM represents over 200 species/subspecies; some are considered strict or opportunistic pathogens. Mycobacterium abscessus, often regarded as one of the most antibiotic-resistant mycobacteria, is the second most frequent NTM pulmonary disease pathogen.

OBJECTIVES

To describe the epidemiology of M. abscessus through a literature review focusing on clinical aspects.

SOURCES

We conducted searches on PubMed and Web of Knowledge for articles published from 2010 to the present using the keywords 'Mycobacterium abscessus', 'Nontuberculous mycobacteria', and 'epidemiology'. Our search prioritized original reports on the occurrence of NTM and M. abscessus infection/disease.

CONTENT

Advanced molecular and genetic diagnostic techniques have refined the M. abscessus complex (MABC) microbiological classification over the last few decades. MABC can adhere to surfaces and form a biofilm. This characteristic and its resistance to common disinfectants allow these microorganisms to persist in the water distribution systems, becoming a constant reservoir. The frequency and manifestation of NTM species vary geographically because of environmental conditions and population susceptibility differences. MABC lung disease, the most frequent site of NTM infection in humans, is often seen in patients with underlying lung diseases such as bronchiectasis, whereas MABC disseminated disease is related to immunosuppression. Skin and soft tissue infections are associated with surgical or injection procedures. Epidemiological evidence suggests an overall increase in MABC infection and disease in the last decade.

IMPLICATIONS

Establishing the burden of this disease is challenging because of varying measures of incidence and prevalence, referral bias, and differences in medical practices and reporting. Furthermore, environmental and structural determinants, infection routes, and MABC pulmonary disease mechanisms require additional investigation. This review contributes to a better understanding of the epidemiology of MABC, which could inform clinical practice and future research.

Fracture-associated infection with Mycobacterium smegmatis in a 16-year old patient

We present a patient who suffered an agricultural rollover trauma and developed a fracture-associated tissue infection caused by Mycobacterium smegmatis. Since cases are rare, treatment of infections with M. smegmatis requires an interprofessional approach and the combination of surgery and adjunctive antimicrobial treatment.

Management of M. abscessus subsp. abscessus early-onset prosthetic joint infection: Case report and literature review

Nontuberculous mycobacteria are a rare but still emerging cause of difficult-to-treat prosthetic joint infection. To our knowledge only 17 cases of M. abscessus complex prosthetic joint infection are reported in literature, of which only 1 is by M. abscessus subps. abscessus. No guidelines are available for this clinical scenario. We describe a 68-years-old female patient with an early-onset M. abscessus subsp. abscessus prosthetic joint infection, successfully treated with a tailored medical-surgical strategy, and present an overview of cases currently available in the literature to assist physicians in the management of these uncommon infections.

In vitro activity of gepotidacin and comparator antimicrobials against isolates of nontuberculous mycobacteria (NTM)

Novel antimicrobials are needed to treat rising nontuberculous mycobacteria (NTM) infections. Using standard broth microdilution methods, 68 NTM isolates were tested against gepotidacin, a new, first-in-class, oral triazaacenaphthylene bacterial topoisomerase inhibitor. MICs varied (0.25 to >64 µg/mL) with the lowest being M. fortuitum complex (0.25-8 µg/mL), M. mucogenicum complex (1-2 µg/mL), M. kansasii (0.25-8 µg/mL), and M. marinum (4-16 µg/mL). Testing greater numbers of some species is suggested to better understand gepotidacin activity against NTM.

Significance of early diagnosis and surgical management in treating Mycobacterium immunogenum-related pyogenic extensor tenosynovitis: a case report

BACKGROUND

Non-tuberculous mycobacteria (NTM) are environmental organisms that are increasingly contributing to human infections. Mycobacterium immunogenum, a variant of NTM discovered in 2001, is a rapidly growing mycobacterium that exhibits multidrug resistance. Reports of infections caused by this organism, particularly tenosynovitis in the musculoskeletal system, are limited.

CASE PRESENTATION

A 71-year-old female with vesicular pemphigus, undergoing immunosuppressive therapy, presented with a progressively enlarging tumour on the dorsum of her right hand, along with erythematous papules that extended across her right forearm. The specimens of skin tissues and blood cultures revealed the presence of M. immunogenum. Magnetic resonance imaging evaluation led to the diagnosis of pyogenic extensor tenosynovitis. A multidrug regimen, comprising amikacin and clarithromycin, was initiated, followed by synovectomy. The patient underwent a course of 180 days of antimicrobial therapy and demonstrated no signs of disease recurrence one year after treatment completion.

CONCLUSION

Early diagnosis and surgical intervention are crucial to prevent the adverse prognostic implications of pyogenic extensor tenosynovitis caused by M. immunogenum. Effective management requires precise microbial identification and susceptibility testing, necessitating collaborative engagement with microbiological laboratories.

Mycobacterium porcinum Disseminated Infection in Non-severely Immunocompromised Host

Mycobacterium porcinum is a nontuberculous mycobacteria (NTM) recently identified to cause human infection. Correct speciation of NTMs can be difficult and result in misdiagnosis and delayed treatment. Because of the paucity of the literature, there is a lack of awareness of the possibility of serious infections caused by M. porcinum. Although severe infections tend to occur in individuals with certain risk factors, the primary being an immunocompromised state, our case illustrates that it can also be possible in non-severely immunocompromised individuals. A 65-year-old male with a medical history of diabetes mellitus (DM), end-stage renal disease (ESRD) on hemodialysis (HD), congestive heart failure (CHF), and chronic obstructive pulmonary disease (COPD) was admitted to the emergency room due to a laceration on his right lower leg following a fall. He reported shortness of breath but denied other respiratory symptoms. On examination, he showed signs of infection and increased oxygen requirement compared to baseline. Blood culture was positive for acid-fast bacilli (AFB), initially reported as M. avium complex (MAC) and later confirmed as M. porcinum through gene sequencing and morphology analysis. Interval blood cultures taken a week later confirmed true M. porcinum bacteremia. Treatment initially involved intravenous antibiotics- imipenem and ciprofloxacin before transitioning to oral linezolid and ciprofloxacin based on sensitivities. Following 10 days of antibiotic therapy, subsequent blood cultures returned negative, and treatment with oral antibiotics was advised, with continued outpatient follow-up with infectious disease in two weeks. M. porcinum, typically considered a contaminant in healthy individuals, was identified as the causative agent of a disseminated infection in a non-severely immunocompromised patient. This case underscores the importance of accurately identifying the specific mycobacterial species, confirming true infection, and conducting antibiotic susceptibility testing due to the distinct antibiotic susceptibility profile of M. porcinum compared to other NTM like MAC.

Mycobacterium abscessus endocarditis post cardiac cathetrisation-a case report and review of 25 cases (2001-2023)

47 year male underwent percutaneous transluminal coronary angioplasty elsewhere, developed fever after two days, and treated empirically in various hospitals for the subsequent two months. Echocardiography showed vegetation in aortic valve and blood cultures were negative. He was then diagnosed as a case of endocarditis due to M. abscessus in our centre by repeated positive blood cultures. After treatment with Imipenem, Amikacin and clarithromycin in the background of pancytopenia, patient was discharged with advice to continue antibiotics and planned for aortic valve replacement. Patient was noncompliant to treatment, readmitted with worsening symptoms, developed multiorgan failure and subsequently died of infection.

Modeling nontuberculous mycobacterial infections in zebrafish

The incidence of infections due to nontuberculous mycobacteria (NTM) has increased rapidly in recent years, surpassing tuberculosis in developed countries. Due to inherent antimicrobial resistance, NTM infections are particularly difficult to treat with low cure rates. There is an urgent need to understand NTM pathogenesis and to develop novel therapeutic approaches for the treatment of NTM diseases. Zebrafish have emerged as an excellent animal model due to genetic amenability and optical transparency during embryonic development, allowing spatiotemporal visualization of host-pathogen interactions. Furthermore, adult zebrafish possess fully functional innate and adaptive immunity and recapitulate important pathophysiological hallmarks of mycobacterial infection. Here, we report recent breakthroughs in understanding the hallmarks of NTM infections using the zebrafish model.

The interplay between the polar growth determinant DivIVA, the segregation protein ParA, and their novel interaction partner PapM controls the Mycobacterium smegmatis cell cycle by modulation of DivIVA subcellular distribution

IMPORTANCE

The genus of Mycobacterium includes important clinical pathogens (M. tuberculosis). Bacteria of this genus share the unusual features of their cell cycle such as asymmetric polar cell elongation and long generation time. Markedly, control of the mycobacterial cell cycle still remains not fully understood. The main cell growth determinant in mycobacteria is the essential protein DivIVA, which is also involved in cell division. DivIVA activity is controlled by phosphorylation, but the mechanism and significance of this process are unknown. Here, we show how the previously established protein interaction partner of DivIVA in mycobacteria, the segregation protein ParA, affects the DivIVA subcellular distribution. We also demonstrate the role of a newly identified M. smegmatis DivIVA and ParA interaction partner, a protein named PapM, and we establish how their interactions are modulated by phosphorylation. Demonstrating that the tripartite interplay affects the mycobacterial cell cycle contributes to the general understanding of mycobacterial growth regulation.

A bronchoscopy-associated pseudo-outbreak of Mycobacterium chelonae and Mycobacterium mucogenicum associated with contaminated ice machine water and ice

A pseudo-outbreak of bronchoscopy-associated Mycobacterium chelonae and M. mucogenicum was traced to contaminated ice machine water and ice. A nonsterile ice bath was used to cool uncapped, sterile, saline syringes used to slow procedural bleeding. Joining the growing evidence of bronchoscopy pseudo-outbreaks, our investigation describes several lessons for future prevention.

A case report on Mycobacterium houstonense infection after total hip arthroplasty

BACKGROUND

Mycobacterium houstonense is a category of rapidly growing mycobacteria that is gram-positive, acid-fast, polycrystalline, and non-spore-forming. There have been few reports of human infection caused by Mycobacterium houstonense worldwide.

CASE PRESENTATION

We present a case of chronic periprosthetic joint infection caused by Mycobacterium houstonense in an elderly female patient. The patient developed signs of infection after undergoing total hip arthroplasty. Despite receiving antibiotic treatment and revision surgery, the signs of infection recurred repeatedly. Multiple bacterial cultures during the treatment period were negative. Later, we identified the pathogenic bacteria Mycobacterium houstonense through mNGS testing, isolated the bacteria from the ultrasonically centrifuged fluid of the prosthesis and obtained drug sensitivity results. Finally, we performed a revision surgery and treated the patient with moxifloxacin and clindamycin. After treatment, the patient did not show signs of infection recurrence during 24 months of follow-up.

CONCLUSION

Through a relevant literature search, we believe that Mycobacterium houstonense may show higher sensitivity to amikacin and quinolone antibiotics. Additionally, clarifying occult infection sources through methods such as gene testing will improve the diagnosis and treatment of periprosthetic joint infection.

Antimicrobial Resistance in Rapidly Growing Nontuberculous Mycobacteria among Domestic and Wild Animals Emphasizing the Zoonotic Potential

Non-tuberculous mycobacteria (NTM) are opportunistic pathogens capable of causing infections in humans and animals. The aim of this study was to demonstrate the potential role of domestic and wild animals as a reservoir of multiple resistant, rapidly growing NTM strains representing a potential zoonotic threat to humans. A total of 87 animal isolates belonging to 11 rapidly growing species (visible colonies appear within three to seven days) were genotyped and tested for susceptibility to the 15 most commonly used antibiotics in the treatment of such infections in a human clinic. By determining the antimicrobial susceptibility, the most prevalent resistance was found to cephalosporins (>50%), followed by amoxicillin-clavulanate (31.0%), clarithromycin (23.0%), tobramycin (14.9%) and doxycycline (10.3%). Resistance to imipenem, ciprofloxacin, minocycline and linezolid was notably lower (<7.0%). All tested isolates were susceptible to amikacin and moxifloxacin. The most frequent resistance was proved in the most pathogenic species: M. fortuitum, M. neoaurum, M. vaccae and M. porcinum. Meanwhile, other species displayed a higher sensitivity rate. No significant resistance differences between domestic and wild animals were found. The established significant frequency of resistance highlights the significant zoonotic potential posed by circulating rapidly growing NTM strains, which could lead to challenges in the treatment of these infections.

Application of FT-IR Spectroscopy for Mycobacterium abscessus complex subspecies differentiation

Mycobacterium abscessus complex (MABSC) subspecies differentiation improves patients' therapy and outcome. Fourier-Transform-Infrared Spectroscopy (FT-IRS) was applied for subspecies discrimination of 15 strains on different media: Löwenstein-Jensen showed the best resolution power; Linear Discriminant Analysis model differentiated M. abscessus susbsp. abscessus from M. abscessus subsp. massiliense. FT-IRS has a potential role in rapidly MABSC subspecies identification.

In Vitro and In Vivo Efficacy of NITD-916 against Mycobacterium fortuitum

Mycobacterium fortuitum represents one of the most clinically relevant rapid-growing mycobacterial species. Treatments are complex due to antibiotic resistance and to severe side effects of effective drugs, prolonged time of treatment, and co-infection with other pathogens. Herein, we explored the activity of NITD-916, a direct inhibitor of the enoyl-ACP reductase InhA of the type II fatty acid synthase in Mycobacterium tuberculosis. We found that this compound displayed very low MIC values against a panel of M. fortuitum clinical strains and exerted potent antimicrobial activity against M. fortuitum in macrophages. Remarkably, the compound was also highly efficacious in a zebrafish model of infection. Short duration treatments were sufficient to significantly protect the infected larvae from M. fortuitum-induced killing, which correlated with reduced bacterial burdens and abscesses. Biochemical analyses demonstrated an inhibition of de novo synthesis of mycolic acids. Resolving the crystal structure of the InhAMFO in complex with NAD and NITD-916 confirmed that NITD-916 is a direct inhibitor of InhAMFO. Importantly, single nucleotide polymorphism leading to a G96S substitution in InhAMFO conferred high resistance levels to NITD-916, thus resolving its target in M. fortuitum. Overall, these findings indicate that NITD-916 is highly active against M. fortuitum both in vitro and in vivo and should be considered in future preclinical evaluations for the treatment of M. fortuitum pulmonary diseases.

Skin and soft tissue infections due to rapidly growing mycobacteria

PURPOSE OF REVIEW

The aim of this article is to review skin and soft tissue infections due to rapidly growing mycobacteria (RGM), with a particular focus on recently published literature (2021-2022).

RECENT FINDINGS

RGM are increasingly reported as a cause of skin and soft tissue infections, both in the community setting and as a cause of nosocomial outbreaks. Recent advances in molecular methods have expanded the number of species of RGM and resulted in increased diagnosis. New treatment options are under evaluation particularly for Mycobacterium abscessus , the most difficult-to-treat among RGM.

SUMMARY

RGM are an uncommon cause of skin and soft tissue infections and a high clinical suspicion together with advanced laboratory facilities are required for diagnosis. Species identification and antimicrobial susceptibility testing are essential to drive appropriate treatment, which combines surgical debridement with prolonged antimycobacterial combination therapy.

A Systematic Review of Nontuberculous Mycobacterium Infection Following Anterior Cruciate Ligament Reconstruction

Although infection following anterior cruciate ligament (ACL) reconstruction is rare, these cases have potentially catastrophic ramifications. Nontuberculous mycobacteria (NTM) are ubiquitous, located in the water supply and soil. Our objective was to review the literature to characterize NTM infection following ACL reconstruction.

Methods

A database search was performed for arthroscopic ACL reconstructions that resulted in a postoperative diagnosis of NTM infection.

Results

The literature search returned 6 case reports that met the inclusion criteria. The initial postoperative presentation occurred after 3 to 52 weeks, which is consistent with reports of postoperative NTM infection.

Conclusions

The common indolent course of NTM infection hinders prompt diagnosis and treatment. Organism susceptibility testing is crucial for effective treatment and limiting unnecessary antibiotic exposure.

Clinical Relevance

The duration of medical treatment for NTM infection is 4 to 6 months, depending on the severity of disease and species. Based on the aggregate literature, we recommend removal of local implants if the infection is localized and without articular involvement. However, in cases of articular involvement, all fixation and graft material should be removed.

A case of novel, rapidly-growing Mycolicibacter kumamotonensis infection in a patient with severe pulmonary disease treated in New York City

INTRODUCTION

Mycolicibacter kumamotonensis is a slowly growing, non-chromogenic non-tuberculous mycobacteria (NTM) that was initially distinguished from the M. terrae complex in 2006. Since then it has been rarely reported as the cause of pulmonary and soft-tissue infections in both immunocompromised and immunocompetent patients.

CASE PRESENTATION

We present a case of severe pulmonary disease due to Mycolicibacter kumamotonensis in a 57-year-old male who was immunocompetent at time of diagnosis, with a history of interstitial lung disease and a prior diagnosis of tuberculosis (TB). After initial treatment for TB in 2017, his condition stabilized until a recurrence in September 2021, leading to an evaluation for lung transplant in the setting of pulmonary fibrosis and emphysema which led to the identification of Mycolicibacter kumamotonensis. A lung transplant was completed, and the patient was successfully treated with a combination of Ethambutol, Azithromycin, and Rifabutin.

CONCLUSIONS

This represents the first case reported of M. kumamotonensis in a patient undergoing lung transplant, and the first case with rapid culture growth during identification of the organism (4 days). This report highlights the need for consideration of M. kumamotonensis as a pathogen in humans, with the potential for rapid growth in liquid media, and the importance of early identification to inform empiric therapy.

Skin and soft tissue infection of Nontuberculous mycobacterium after injection lipolysis

BACKGROUND

Injection lipolysis is used for body and face contouring due to its minimal invasiveness and cost-effectiveness, but related complications such as nontuberculous mycobacterium infection significantly affect its clinical application.

AIMS

This study aimed to review the literature on NTM infection after injection lipolysis.

METHODS

We conducted a literature review of scientific journals published in Medline and PubMed up to September 2022 on patients with NTM skin and soft tissue infections. We used the keywords: nontuberculous mycobacterium, infection, injection lipolysis, and lipolytic solution in various combinations with the Boolean operators AND, OR, and NOT. Only articles available in English and full version publications were considered for this review. Here, we reviewed the relevant mechanisms and drugs for injectable lipolysis and analyzed the possible correlation between NTM infection and injection lipolysis. We also summarize methods for the diagnosis and treatment of NTM infections and present some perspectives on this therapy.

RESULTS

Many patients with NTM infections had a history of fat-related surgery or therapy. NTM infection after injection lipolysis may be related to inadequate disinfection and sterilization of injection equipment and clinical procedures, the unqualified medication itself and free fatty acids released during injection lipolysis. Currently, diagnosis and treatment of NTM infection after lipolysis injections remains challenging.

CONCLUSIONS

Injection lipolysis represents a helpful option for local fat reduction. Doctors should strictly abide by the aseptic operation standards and use qualified products for there is a correlation between skin and soft tissue infection of nontuberculous mycobacterium and injection lipolysis. Providers should understand the mechanism, indications, and associated risks of injection lipolysis when injecting fat-dissolving drugs to reduce localized fat.

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.

Shower water contributes viable nontuberculous mycobacteria to indoor air

Nontuberculous mycobacteria (NTM) are frequently present in municipal drinking water and building plumbing, and some are believed to cause respiratory tract infections through inhalation of NTM-containing aerosols generated during showering. However, the present understanding of NTM transfer from water to air is insufficient to develop NTM risk mitigation strategies. This study aimed to characterize the contribution of shower water to the abundance of viable NTM in indoor air. Shower water and indoor air samples were collected, and 16S rRNA and rpoB genes were sequenced. The sequencing results showed that running the shower impacted the bacterial community structure and NTM species composition in indoor air by transferring certain bacteria from water to air. A mass balance model combined with NTM quantification results revealed that on average 1/132 and 1/254 of NTM cells in water were transferred to air during 1 hour of showering using a rain and massage showerhead, respectively. A large fraction of the bacteria transferred from water to air were membrane-damaged, i.e. they had compromised membranes based on analysis by live/dead staining and flow cytometry. However, the damaged NTM in air were recoverable as shown by growth in a culture medium mimicking the respiratory secretions of people with cystic fibrosis, implying a potential infection risk by NTM introduced to indoor air during shower running. Among the recovered NTM, Mycobacterium mucogenicum was the dominant species as determined by rpoB gene sequencing. Overall, this study lays the groundwork for future pathogen risk management and public health protection in the built environment.

Host DNA depletion can increase the sensitivity of Mycobacterium spp. detection through shotgun metagenomics in sputum

Identification and phenotypic drug-susceptibility testing for mycobacteria are time-consuming and challenging but essential for managing mycobacterial infections. Next-generation sequencing (NGS) technologies can increase diagnostic speed and quality, but standardization is still lacking for many aspects (e.g., unbiased extraction, host depletion, bioinformatic analysis). Targeted PCR approaches directly on sample material are limited by the number of targets that can be included. Unbiased shotgun metagenomics on direct material is hampered by the massive amount of host DNA, which should be removed to improve the microbial detection sensitivity. For this reason, we developed a method for NGS-based diagnosis of mycobacteria directly from patient material. As a model, we used the non-tuberculous mycobacterium (NTM) Mycobacterium abscessus. We first compared the efficiency of three different DNA extraction kits for isolating DNA (quality and concentration). The two most efficient kits were then used in a follow-up study using artificial sputum. Finally, one extraction kit was selected and further evaluated for DNA isolation from a patients’ sputum mixture spiked with M. abscessus at three concentrations (final concentrations 108, 107, 106  CFU/ml). The spiked sputum samples were processed with and without saponin treatment (ST) in combination with DNAse treatment prior to bacterial DNA extraction to evaluate the recovery of bacteria and depletion of host DNA by PCR and Illumina sequencing.

While Ct values of the qPCR targeting mycobacterial ITS DNA remained rather stable, Ct values in the qPCR targeting the human β-actin gene increased by five Ct values in ST samples. In subsequent Illumina sequencing, a decrease of 89% of reads mapped to the human genome was observed in ST samples. The percentage of reads mapped to M. abscessus (108 CFU/ml) increased by 89%, and the sequencing depth increased two times when undergoing ST.

In conclusion, the sensitivity of M. abscessus detection in artificial sputum was increased using a saponin pre-treatment step. The saponin followed by the DNase I treatment approach could be efficiently applied to detect and characterize mycobacterial infections, including tuberculosis, directly from sputum.

Nontuberculous Mycobacterial Infections Associated With Left Ventricular Assist Devices in 3 Patients

Durable left ventricular assist devices (LVADs) provide circulatory support in patients with end-stage heart failure; however, complications include infection of the driveline exit site. Nontuberculous mycobacterial infections are rare in patients with LVADs, but they should be considered in those who have undergone device exchanges and have bacterial infections with driveline exit-site discharge but no fever or leukocytosis. We reviewed the charts of patients who had an LVAD implanted at our institution from January 2009 through December 2019, to identify those with a device-related nontuberculous mycobacterial infection. Collected data included patient demographics, premorbid conditions, infection type, previous device complications, treatment, and outcomes. We identified infections in 3 patients (mean age, 41 yr): Mycobacterium abscessus in 2 and M. chimaera in 1. All had a HeartMate II device and had undergone device exchanges for pump thrombosis or for driveline fault or infections. All presented with driveline exit-site discharge without fever or leukocytosis. The mean time between initial device implantation and diagnosis of a nontuberculous mycobacterial infection was 55 months. All 3 patients were treated with antibiotics and underwent localized surgical débridement; one underwent an additional device exchange. The M. abscessus infections disseminated, and both patients died; the patient with M. chimaera infection continued to take suppressive antibiotics. Nontuberculous mycobacterial infections are associated with high morbidity and mortality rates, warranting prompt diagnosis and treatment.

Central nervous system infection caused by Mycobacterium houstonense: A case report

Background

Mycobacterium houstonense is a rapidly growing mycobacterium (RGM) that belongs to the unnamed third biovariant complex of the Mycobacterium fortuitum group, which is rarely responsible for human infection. Approximately 76% of infections caused by the M. fortuitum group occur after open fractures or skin, soft tissue, bone, or puncture wounds. To date, only a few cases of human infectious disease caused by M. houstonense have been reported worldwide.

Case presentation

We present a case of a 26-year-old man with a central nervous system (CNS) infection caused by M. houstonense. The patient was transferred to our hospital because of headaches and muscle strength changes. One month prior to presentation at our hospital, the patient was diagnosed with tuberculous meningitis at the other two hospitals, but his condition did not improve after anti-tuberculous treatment, antibiotics, and anti-viral treatment before admission to our hospital. Lumbar puncture was performed at both previous hospitals, as well as at our hospital; the results consistently indicated high cerebrospinal fluid (CSF) opening pressure. M. houstonense was detected in the CSF of the second hospital's lumbar puncture by metagenomic next-generation sequencing (mNGS) but was not identified at our hospital. The patient was discharged from our hospital after receiving non-tuberculous mycobacterium (NTM) treatment for 1 month according to the Chinese NTM guidelines. However, the patient died 20 days after discharge.

Conclusion

Since it is difficult to identify M. houstonense, this is the first case of human CNS infection caused by M. houstonense in China. This case may be considered by neurologists and infectious physicians when CNS infection does not respond to conventional treatment, especially in the uncommon type of NTM.

New RAPMYCOI SensititreTM Antimicrobial Susceptibility Test for Atypical Rapidly Growing Mycobacteria (RGM)

Rapidly growing mycobacteria (RGM) cause an increasing international concern, mainly due to their natural resistance to many antibiotics. The aim of this study was to conduct species identification and determine the antimicrobial susceptibility profiles of RGM isolated in Poland. Antimicrobial susceptibility was tested using broth microdilution and the RAPMYCOI panel. A total of 60 strains were analysed, including the following species: M. fortuitum complex (30), M. abscessus subsp. abscessus (16), M. abscessus subsp. massiliense (7), M. chelonae (5), and M. mucogenicum (2). For 12 M. abscessus subsp. abscessus strains, the presence of the erm 41T28 genotype associated with inducible macrolide resistance and a functional erm gene was confirmed. A MUT2 mutation in the rrl gene (constitutive resistance) was identified for two strains from the subtype M. abscessus subsp. massiliense. Among the 15 tested antibiotics, amikacin and linezolid had the strongest antimycobacterial activity. Most of the tested strains were resistant to doxycycline and trimethoprim/sulfamethoxazole. Tigecycline MICs were low for all tested strains. Findings from our study highlight the importance of correct identification of clinical isolates and antimicrobial susceptibility testing.

First case of systemic fatal mycobacteriosis caused by Mycobacterium goodii in a pet Kenyan sand boa (Eryx colubrinus loveridgei)

Background

Environmental nontuberculous mycobacteria species that are not members of the M. tuberculosis complex, are ordinary inhabitants of a wide variety of environmental reservoirs and their role in human and animal diseases has been fully recognized. Even if spontaneous mycobacterial infections have been reported in a wide variety of reptiles, this is the first report of systemic fatal mycobacteriosis sustained by Mycobacterium goodii in a pet reptile. 

Case presentation

An adult, wild caught (WC), male Kenyan sand boa (Eryx colubrinus loveridgei) age unknown, was presented for clinical examination due to decreased activity level, decreased appetite and diarrhea. Blood tests showed unreliable results. Coprologic exam showed a moderate to severe presence of flagellates. X rays and ultrasound showed moderate presence of air and faeces in the large intestine. The snake was hospitalized and oral metronidazole was chosen as antiprotozoal agent in association with subcutaneous warm fluids. The snake was discharged after 2 weeks therapy in good clinical condition. Faecal exam resulted negative. One month after, the snake was quickly hospitalized again because of a recrudescence of symptoms. Biochemistry showed severe increase of AST, ALT and biliary acids. Severe leucocytosis and moderate to severe anemia were highlighted. Ultrasound examination revealed a severe diffused alteration of the liver parenchyma and a fine needle aspiration was performed. The cytological diagnosis was mixed inflammation, with a numerous of unstained rod-shaped bacteria both inside macrophages and free in the sample. The snake’s condition rapidly deteriorated and euthanasia was performed. The histology of the coelomic organs confirmed a systemic mycobacteriosis. Real-time PCR identified the mycobacteria as Mycobacterium goodii.

Conclusions

Species from the genus Mycobacterium are among the most important micro-organism including the causative agents of tuberculosis. Even if the general incidence of disease in reptiles due to mycobacteria is comparatively low, they can serve as reservoirs of many ubiquitous mycobacteria species. Mycobacterium goodii is a rapidly growing non‐tuberculous mycobacterium that has recently been associated with severe infections in animals and humans. Although in this case the pathogenesis was not completely clear, we highlight the zoonotic risk of mycobacteriosis in exotic animals especially in WC specimens.

Rapid Detection of Clarithromycin and Amikacin Resistance in Mycobacterium abscessus Complex by High-Resolution Melting Curve Analysis

The emergence of Mycobacterium abscessus complex (MABC) infection is the most noteworthy health care problem. Clarithromycin (CLA) and amikacin (AMK) constitute the cornerstone of treatment for patients infected with MABC; thus, early detection of resistance to these two drugs is essential for formulating effective therapeutic regimens. In the present study, we aimed to validate the use of MeltPro MAB assay, a melting curve analysis with dually labeled probes, on a set of clinical isolates to detect CLA and AMK resistance. A total of 103 clinical MABC strains were collected in our analysis, including 76 strains of M. abscessussubsp. Abscessus (MAA) and 27 strains of M. abscessussubsp. Massiliense (MAM). In vitro susceptibility testing revealed that two isolates exhibited intrinsic CLA resistance by harboring A2270T mutation in rrl, and inducible resistance was noted in 42 isolates. Additionally, two MAA isolates with erm(41)T28 genotype were susceptible to CLA. Notably, we found three out of 44 isolates had two melting curve peaks, representing the simultaneous presence of mutant and the wild type in these specimens. In contrast, no known mutations were identified in six AMK-resistant isolates. Further analysis revealed that MeltPro yielded 100% and 96.67% sensitivity and specificity for detecting CLA resistance. In summary, this study firstly demonstrates that MeltPro is a promising diagnostic for early detection of CLA resistance for MABC isolates, which significantly improves the turnaround time within 2 h. Approximate two fifths of MABC isolates are resistant to CLA by 23S rRNA mutation or its methylation, emphasizing the urgent need for early detection of CLA resistance prior to empirical treatment of MABC infections.

IMPORTANCEMycobacterium abscessus complex (MABC) has attracted increasing attention due to the numerous cases of infection. This pathogen is notorious for its intrinsic drug resistance, which complicates clinical management of patients with MABC infections. Clarithromycin (CLA) and amikacin (AMK) are the cornerstone of treatment regimens for MABC. Herein, our data firstly demonstrates that MeltPro is a promising diagnostic for early detection of CLA resistance for MABC isolates. The high frequency of CLA-resistant MABC isolates in China emphasizes the urgent need for early detection of CLA resistance prior to empirical treatment of MABC infections.

Mycobacterium fortuitum pacemaker infection: A case report

BACKGROUND

Mycobacterium fortuitum is a rapidly growing mycobacterium, ubiquitous in soil and water, but it is an uncommon cause of infections in immunocompetent hosts. Cardiac device infections and bloodstream infections due to non-tuberculous mycobacteria are rare.

CASE PRESENTATION

We present the case of an 85-year-old patient with infective endocarditis and pacemaker lead infection secondary to M. fortuitum.

Cardiovascular device infections due to rapidly growing Mycobacteria: A review of cases at a tertiary care hospital

Cardiovascular device infection due to rapidly growing mycobacteria (RGM) is rarely encountered in clinical practice. Due to the increasing number of indications and use of cardiovascular devices in an aging population, optimized management of these infections is of great importance. We report seven cases of RGM cardiovascular device infection. Three patients had left-ventricular assist device (LVAD) infections; two patients had cardiovascular implantable device (CIED) infections; and one had an aortic vascular stent infection. Specific cardiac valvular infection was not detected among any of the patients. All patients had a high number of comorbidities which limited some patients from receiving optimal combination antimicrobial therapy. The prognosis of cardiovascular device infections with RGM is guarded with only four patients still alive; however, the treatment approach for each patient varied considerably and often based on concurrent medical conditions, overall adjustments to goals of care, and specific patient preferences. Further analysis of cardiovascular device infections with RGM is warranted to establish a more systematic approach in successful management.

Mycobacterium abscessus and Mycobacterium massiliense exhibit distinct host and organ specificity: a cross-sectional study

PURPOSE

Precise subspeciation of Mycobacterium abscessus complex (MAB) is crucial for predicting antibiotic susceptibilities and patient outcomes. However, routine clinical microbiology laboratories have limited diagnostic tools for the differentiation of the subspecies. Thus, we investigated the predictors for MAB subspecies to actuate rapid differentiation and the optimal treatment plans.

METHODS

We retrospectively identified stored clinical isolates of MAB and reviewed patient medical records to compare clinical characteristics, sites of infection, and outcomes among patients infected with M. abscessus subsp. abscessus (M. abscessus) and M. abscessus subsp. massiliense (M. massiliense). MAB subspecies were characterized by multilocus sequence analysis with three-locus sequence (hsp65, rpoB, and secA1) and pulsed-field gel electrophoresis.

RESULTS

After outbreak and duplicated cases were excluded, 56 and 36 patients with infection caused by M. abscessus and M. massiliense, respectively, were included in the analysis. Patients with either cardiovascular disease or risk factors for cardiovascular disease (male gender and age ≥55 years) were 4.5 times more likely to harbor M. abscessus (P = 0.002), while M. massiliense was 4.8 times more frequently recovered from cutaneous and surgical wounds (P = 0.04).

CONCLUSION

Distinct host and organ specificity were observed among patients infected with M. abscessus and those with M. massiliense. These differences may provide clinically significant clues to optimize treatment strategies.

A new approach to the treatment of nontuberculous mycobacterium skin infections caused by iatrogenic manipulation: Photodynamic therapy combined with antibiotics: A pilot study

BACKGROUND

Recently, the number of nontuberculous mycobacterium (NTM) infections caused by iatrogenic procedures, especially rapid NTM skin infections, has been increasing. Due to the nonspecific clinical manifestations and nonstandard treatment guidelines, these infections are often misdiagnosed and challenging to treat.

METHODS

In this study, eight patients had NTM skin infections caused by iatrogenic procedures, and were diagnosed by bacterial culture and flight mass spectrometry tests. They were treated with 5-aminolevulinic acid-photodynamic therapy (ALA-PDT) combined with antibiotic therapy.

RESULTS

All eight patients enrolled in the study were cured with 100% efficacy after receiving combination therapy with ALA-PDT and antibiotics for 3-6 months. All patients experienced redness and pain during treatment but no other discomfort and were satisfified with the results of their treatments.

CONCLUSION

Local ALA-PDT combined with antibiotics is a safe and effective method of treating NTM skin infections.

Nontuberculous Mycobacteria under Scrutiny in the Geneva Area (2015-2020)

BACKGROUND

Nontuberculous mycobacteria (NTM) are increasingly identified in industrialized countries, and their role as pathogens is more frequently recognized. The relative prevalence of NTM strains shows an important geographical variability. Thus, establishing the local relative prevalence of NTM strains is relevant and useful for clinicians.

METHODS

Retrospective analysis (2015-2020) of a comprehensive database was conducted including all results of cultures for mycobacteria in a University Hospital (Geneva, Switzerland), covering a population of approximately 500,000 inhabitants. All NTM culture-positive patients were included in the analyses. Patients' characteristics, NTM strains, and time to culture positivity were reported.

RESULTS

Among 38,065 samples analyzed during the study period, 411 were culture-positive for NTM, representing 236 strains, and 231 episodes of care which occurred in 222 patients. Patients in whom NTM were identified were predominantly female (55%), with a median age of 62 years, and a low BMI (median: 22.6 kg/m2). The Mycobacterium avium complex (MAC) was the most frequently identified group (37% of strains) followed by Mycobacterium gordonae (25%) and Mycobacterium xenopi (12%) among the slowly growing mycobacteria (SGM), while the Mycobacterium chelonae/abscessus group (11%) were the most frequently identified rapidly growing mycobacteria (RGM). Only 19% of all patients were treated, mostly for pulmonary infections: the MAC was the most frequently treated NTM (n = 19, 43% of cases in patients treated) followed by RGM (n = 15, 34%) and M. xenopi (n = 6, 14%). Among those treated, 23% were immunosuppressed, 12% had pulmonary comorbidities, and 5% systemic comorbidities. Cultures became positive after a median of 41 days (IQR: 23; 68) for SGM and 28 days (14; 35) for RGM.

CONCLUSIONS

In Western Switzerland, M. avium and M. gordonae were the most prevalent NTM identified. Positive cultures for NTM led to a specific treatment in 19% of subjects. Patients with a positive culture for NTM were mostly female, with a median age of 62 years, a low BMI, and a low prevalence of immunosuppression or associated severe comorbidities.

Bloodstream infections with rapidly growing nontuberculous mycobacteria

Background

Bloodstream infections (BSI) with rapidly growing mycobacteria (RGM) resulted in recent nosocomial outbreaks predominantly in immunocompromised patients. A little is known about the clinical implications of RGM BSI with different species.

Methods

We conducted a multicenter retrospective cohort study of patients with RGM BSI from November 2011 to December 2020. Demographic data, clinical presentation, laboratory and radiographic findings and microbiological characteristics were used to tabulate descriptive statistics. We performed a comparative analysis of patients with BSI due to Mycobacterium abscessus complex (MABC) vs. other RGM.

Results

We identified 32 patients with positive blood cultures for RGM, 4/32 (12.5%) were considered to have unclear significance. The most common source for RGM BSI was intravascular catheters (14/28, 50%). Compared to other sources, patients with catheter-related bloodstream infection (CRBSI) received a shorter course of antimicrobial therapy (median [IQR]: one month [0.37–2.25] vs. six months [2–12]), (P = 0.01). The most common species isolated were MABC (12/28, 42.9%), followed by Mycobacterium fortuitum group (6/28, 21.4%) and Mycobacterium chelonae (6/28, 21.4%). Compared to other RGM, MABC BSI was more likely to be secondary to skin and soft tissue infection, associated with longer hospital stay (P = 0.04) and higher death rates despite a higher number of antimicrobial agents used for empirical and directed therapy per patient.

Conclusion

MABC BSI is associated with an overall more resistant profile, longer hospital stay, and higher death rate despite a more aggressive therapy approach.

Cutaneous Mycobacterium chelonae in a Patient with Sjogren's Syndrome

A case of cutaneous Mycobacterium chelonae infection in a patient with Sjogren's syndrome (SS) was misdiagnosed as sporotrichosis. A 56-year-old female patient was admitted to another hospital. Based on results of the histopathological examination and secretion culture obtained at the other hospital, the patient was diagnosed with sporotrichosis and received antifungal therapy. After treatment failure, the patient was admitted to our hospital, and a histopathological examination and secretion culture were performed again. The secretion culture revealed the presence of Mycobacterium chelonae. The antinuclear antibody test suggested SS, and the patient was treated with antibiotics and corticosteroids.

A Ventral Hernia-repair-related Mycobacterium mageritense Mesh Infection Treated with NPWT without Mesh Removal

Abdominal hernias are often repaired using prosthetic mesh, which is susceptible to infections. Normally, it is necessary to remove the mesh. However, successful mesh salvation with negative-pressure wound therapy (NPWT) has recently been reported. We encountered Mycobacterium(M) mageritense infection after hernia repair using the mesh. M. mageritense is classified as a fast-growing nontuberculous mycobacterium, but few cases have been reported. Nontuberculous mycobacterium can cause rare chronic infections. Skin and soft-tissue infections by nontuberculous mycobacterium involving localized abscess formation and chronic abscesses under various situations have been reported. We report an 85-year-old woman in whom a ventral hernia repair-related M. mageritense mesh infection was treated with NPWT without mesh removal. The hernia was repaired using Bard Ventralex mesh. Pus discharge was seen on the seventh postoperative day, and there was a small area of necrosis under the mesh. From the 13th postoperative day, NPWT was performed for 4 weeks. On the 29th postoperative day, a M. mageritense infection was diagnosed, which was resistant to multiple drugs. After the NPWT, most of the wound showed good granulation tissue formation. In conclusion, the mesh used to repair a hernia became infected with M. mageritense, but NPWT was able to salvage it. In cases of mesh infection involving small necrotic areas, performing NPWT under the guidance of an infectious disease expert may make it possible to preserve the mesh.

Photo-damage promoted by tetra-cationic palladium(II) porphyrins in rapidly growing mycobacteria

Antimicrobial photodynamic therapy (aPDT) has gained prominence in microbiology, especially in treating non-invasive infections. Diseases such as mycobacteriosis, which causes localized infections and has a slow treatment, tend to be future targets for this type of technology. Therefore, this study aimed to explore the action of two isomeric Pd(II)-porphyrins on fast-growing mycobacterial strains (RGM). Tetra-cationic porphyrins (4-PdTPyP and 3-PdTPyP) were synthesized and applied against standard strains of Mycobacteroides abscessus subsp. abscessus (ATCC 19977), Mycolicibacterium fortuitum (ATCC 6841), Mycolicibacterium smegmatis (ATCC 700084), and Mycobacteroides abscessus subsp. massiliense (ATCC 48898). Reactive oxygen species (ROS) scavengers were used in an attempt to determine possible ROS produced by the photosensitizers (PS) under study. Moreover, the impact of porphyrin on the mycobacterial surface was further evaluated by atomic force microscopy (AFM), and we observed significant damage on cells walls and altered nanomechanical and electrostatic adhesion properties. The results presented herein show that the positively charged porphyrin at the meta position (3-PdTPyP) was the most efficient PS against the RGM strains, and its bactericidal activity was proven in two irradiation sessions, with singlet oxygen species being the main ROS involved in this process. This study demonstrated the therapeutic potential of porphyrins, especially the 3-PdTPyP derivative.

Disseminated Mycobacterium chelonae infection with Hughes-Stovin syndrome

Mycobacterium chelonae usually causes localized cutaneous infections and abscesses but has the potential to cause disseminated infections, especially in immunocompromised hosts. We report a 27-year-old man with Hughes-Stovin syndrome and catastrophic antiphospholipid syndrome who was on chronic immunosuppressant therapy and developed disseminated M. chelonae infection. To the best of our knowledge, this is the first case report of M. chelonae infection in a patient with Hughes-Stovin syndrome.

Isolation, characterization of galactose-specific lectin from Odoiporus longicollis and its antibacterial and anticancer activities

Lectins are renowned hemagglutinins and multivalent proteins with a well known quality for sugar-binding specificity that participate significantly in invertebrate defense functions. Studies on biological activity of lectin from coleopteran insect are very scarce. In this study, lectin from the hemolymph in the grub of banana pest, Odoiporus longicollis was subjected to purification, biochemical and functional characterizations. The lectin was purified by PEG precipitation and ion-exchange chromatography using Q-Sepharose as a matrix. The purified lectin showed hemagglutination activity against rat erythrocytes, heat-labile, cation independent and insensitive to EDTA. Further, the carbohydrate affinity of this lectin was found with mannitol, adonitol, L-arabinose, L-rhamnose, D-galactose and sorbitol. The native form of purified lectin was calculated as 360 kDa by FPLC system. Denatured gel electrophoresis of the purified lectin consisted of five distinct polypeptides with molecular weights approximately 160, 60, 52, 40 and 38 kDa, respectively. The amino acid sequences obtained through peptide mass fingerprinting analysis exhibited homologies to the known conserved regions of galactose binding lectins. Further, the purified lectin exhibited bacterial inhibition with LPS from Serratia marcescens. In addition, isolated lectin also exerted bacterial agglutination, antibacterial and anti-proliferative activity against Mycobacterium smegmatis, Bacillus pumilus and Neuro 2a cell line, respectively.

Comparing genotypes and antibiotic resistance profiles of Mycobacterium abscessus and Mycobacterium massiliense clinical isolates in China

This study aimed to investigate differences in the antimicrobial susceptibility of members of the Mycobacterium abscessus complex (MABC): subsp. massiliense and subsp. abscessus, and to identify associations between strain genotypes and antimicrobial resistance phenotypes. A total of 383 clinical MABC isolates (subsp. abscessus: n = 218, 56.9%; subsp. massiliense: n = 163, 42.6%; subsp. bolletii: n = 2, 0.5%) were characterised using multilocus variable number tandem repeat (VNTR) typing and drug susceptibility testing. Most isolates exhibited susceptibility to amikacin, clarithromycin and azithromycin but resistance to cefoxitin and minocycline was statistically more associated with isolates unclustered by VNTR type. The Simpson's diversity indexes of VNTR typing for M. abscessus and M. massiliense isolates were 0.999 and 0.997, respectively. Genotyping of M. abscessus and M. massiliense isolates by VNTR may provide valuable information for predicting resistance phenotype.

Culturing Mycobacteria

Building upon the foundational research of Robert Koch, who demonstrated the ability to grow Mycobacterium tuberculosis for the first time in 1882 using media made of coagulated bovine serum, microbiologists have continued to develop new and more efficient ways to grow mycobacteria. Presently, all known mycobacterial species can be grown in the laboratory using either axenic culture techniques or in vivo passage in laboratory animals. This chapter provides conventional protocols to grow mycobacteria for diagnostic purposes directly from clinical specimens, as well as in research laboratories for scientific purposes. Detailed protocols used for production of M. tuberculosis in large scale (under normoxic and hypoxic conditions) in bioreactors and for production of obligate intracellular pathogens such as Mycobacterium leprae and "Mycobacterium lepromatosis" using athymic nude mice and armadillos are provided.

Pulmonary infection due to fluoroquinolone-resistant Mycolicibacterium fortuitum: a case report

Background

Mycolicibacterium fortuitum is a species of the rapidly growing mycobacteria that can cause pulmonary infection. It is susceptible to multiple antibiotics both in vitro and in clinical practice, so that any combination of susceptible drugs is effective. However, we encountered a case of infection due to fluoroquinolone-resistant M. fortuitum. In this study, we report the case and describe the mechanism of resistance.

Case presentation

A 65-year-old man with a history of total gastrectomy and immunosuppressant treatment for rheumatoid arthritis developed a recurrence of pulmonary infection caused by M. fortuitum. He was treated with clarithromycin and levofloxacin as a first-line treatment, based on the favorable susceptibility at that time. After recurrence, a high minimum inhibitory concentration to fluoroquinolones was detected. DNA sequencing of the pathogen showed the substitution of serine for tryptophan at residue 83 in the gyrA gene. He was successfully treated with a combination of other antibiotics.

Conclusion

This is the first report on the treatment of fluoroquinolone-resistant M. fortuitum and investigation of the mechanism of resistance. We suggest that the susceptibility test remains effective for determining the next line of treatment after a pathogen has acquired resistance, and resistance to fluoroquinolones in M. fortuitum can be attributed to a single change of amino acid.

Mycobacterium septicum: a 6-Year Clinical Experience from a Tertiary Hospital and Reference Laboratory

Mycobacterium septicum is a rarely identified nontuberculous mycobacterium capable of causing infections in both healthy and immunocompromised individuals. Only a few cases of M. septicum infections have been reported, which makes recognizing corresponding clinical disease more challenging for clinicians. Antimicrobial susceptibility profiles for this organism are not well described, and corresponding optimal therapeutic regimens have not been established. We report a tertiary care center's experience with M. septicum from 2014 to 2020. Twelve adult patients with positive cultures for M. septicum were identified. Most cases were identified from sputum samples of individuals with underlying lung disease. Most cases involving M. septicum isolation in culture were not felt to be clinically significant. Two cases were considered possible infections, while only one case was considered a definite infection that required antimicrobial treatment. All M. septicum isolates were susceptible in vitro to amikacin, ciprofloxacin, imipenem, linezolid, moxifloxacin, and trimethoprim-sulfamethoxazole. Isolates were universally resistant to clarithromycin and doxycycline. The isolation of M. septicum in culture is uncommon and requires clinical correlation to determine its clinical relevance and need for treatment. Susceptibility testing should be performed to guide therapy.

Endophthalmitis caused by Mycobacterium houstonense: case report

BACKGROUND

Mycobacterium houstonense is rapidly growing mycobacteria (RGM) that belongs to M. fortuitum group. So far, there have been few associated reports of human diseases induced by M. houstonense worldwide.

CASE PRESENTATION

We present a delayed-onset postoperative endophthalmitis caused by M. houstonense after glaucoma drainage implant (GDI) surgery. The ocular infection lasted for 2 months without appropriate treatment that developed into endophthalmitis and the patient underwent an emergency enucleation.

CONCLUSION

Implant erosion and a delay in diagnosis of ocular infection could lead to irreversible damage as observed in our case. Ophthalmologists should be alert for ocular RGM infection, and prompt laboratory diagnosis with initiation of effective multidrug therapy might prevent loss of vision.

Mycobaterium fortuitum disseminated infection in an immunocompetent patient without predisposing factors

Most Mycobacterium fortuitum infections described involve direct inoculation through skin lesions. We describe the case of a patient without risk factors who presented with an intracranial mass and a pulmonary infection with M. fortuitum As M. fortuitum are rarely pathogens, there is little knowledge about the optimal treatment and outcome of such infections: what is the best mode of administration, what is the best therapy duration and is surgery always required are some of the unanswered questions. In our patient, surgical removal of the mass associated with a 1-year antimycobacterial therapy led to a full recovery. Even though M. fortuitum was rapidly identified in sputum, it was initially considered non-pathogenic and the definitive diagnosis required almost 6 weeks of investigations. New molecular techniques will probably lead to more identifications of M. fortuitum in the next few years and a better knowledge of their possible pathogenicity and optimal treatment.

Mycobacterium mageritense Prosthetic Joint Infection

Prosthetic joint infections (PJI) complicate up to 2% of arthroplasties and are usually caused by typical bacterial agents (e.g., staphylococci and streptococci). Although an infrequent cause of PJI, mycobacterial species are difficult to eradicate, as they adhere to hardware, form biofilms, and have high rates of antimicrobial resistance. Mycobacterium mageritense is a rapidly growing Mycobacterium that has been infrequently described as a cause of surgical and device-related infections. We herein described a case of prosthetic knee infection due to M. mageritense. The patient was treated with removal of hardware, antimicrobials, and prosthetic knee reimplantation with a good outcome. To our knowledge, M. mageritense has not been previously described as a cause of PJI in the medical literature.

CFTR Depletion Confers Hypersusceptibility to Mycobacterium fortuitum in a Zebrafish Model

The Mycobacterium fortuitum complex comprises several closely related species, causing pulmonary and extra-pulmonary infections. However, there is very limited knowledge about the disease pathogenesis involved in M. fortuitum infections, particularly due to the lack of suitable animal models. Using the zebrafish model, we show that embryos are susceptible to M. fortuitum infection in a dose-dependent manner. Furthermore, zebrafish embryos form granulomas from as early as 2 days post-infection, recapitulating critical aspects of mycobacterial pathogenesis observed in other pathogenic species. The formation of extracellular cords in infected embryos highlights a previously unknown pathogenic feature of M. fortuitum. The formation of large corded structures occurs also during in vitro growth, suggesting that this is not a host-adapted stress mechanism deployed during infection. Moreover, transient macrophage depletion led to rapid embryo death with increased extracellular cords, indicating that macrophages are essential determinants of M. fortuitum infection control. Importantly, morpholino depletion of the cystic fibrosis transmembrane conductance regulator (cftr) significantly increased embryo death, bacterial burden, bacterial cords and abscesses. There was a noticeable decrease in the number of cftr-deficient infected embryos with granulomas as compared to infected controls, suggesting that loss of CFTR leads to impaired host immune responses and confers hypersusceptiblity to M. fortuitum infection. Overall, these findings highlight the application of the zebrafish embryo to study M. fortuitum and emphasizes previously unexplored aspects of disease pathogenesis of this significant mycobacterial species.

Successful bedaquiline-containing antimycobacterial treatment in post-traumatic skin and soft-tissue infection by Mycobacterium fortuitum complex: a case report

BACKGROUND

Mycobacterium fortuitum complex is a group of rapidly growing nontuberculous mycobacteria (NTM) associated with skin and soft-tissue infections after surgery or trauma. Treatment of NTM is challenging, due to resistance to multiple antimycobacterial agents. Bedaquiline is a diarylquinoline that inhibits mycobacterial ATP-synthase. The drug has recently been approved for the treatment of multidrug-resistant tuberculosis and evidence of its in vitro efficacy against NTM, including Mycobacterium fortuitum complex, has been published.

CASE PRESENTATION

A 20-year-old Caucasian woman with chronic skin and soft tissue infection in the lower leg following a traffic accident in Vietnam underwent a tedious journey of healthcare visits, hospital admissions, empiric antimicrobial treatments, surgical debridement and plastic reconstruction before definite diagnosis of Mycobacterium fortuitum complex-infection was established by culture from a tissue biopsy and targeted antimycobacterial therapy was administered. Histopathological examination revealed granulomatous purulent inflammation, which strongly supported the diagnosis. Genotypic identification was performed and broth microdilution for susceptibility testing showed macrolide resistance. Five weeks of induction treatment with intravenous amikacin, imipenem / cilastin, and oral levofloxacin was administered, followed by all-oral treatment with bedaquiline combined with levofloxacin for four months, which was well-tolerated and led to persistent healing with scars but without signs of residual infection.

CONCLUSIONS

Bedaquiline is a promising novel agent for NTM treatment, although clinical data are limited and trials evaluating efficacy, safety, and resistance of bedaquiline are required. To our knowledge, this is the first reported case of successful in vivo use of bedaquiline for a skin and soft tissue infection caused by Mycobacterium fortuitum complex.

Nontuberculous mycobacteria in patients with suspected tuberculosis and the genetic diversity of Mycobacterium avium in the extreme south of Brazil

Objective:

Nontuberculous mycobacteria (NTM) are a heterogeneous group of bacteria that are widely distributed in nature and associated with opportunistic infections in humans. The aims of this study were to identify NTM in patients with suspected tuberculosis who presented positive cultures and to evaluate the genetic diversity of strains identified as Mycobacterium avium.

Methods:

We studied pulmonary and extrapulmonary samples obtained from 1,248 patients. The samples that tested positive on culture and negative for the M. tuberculosis complex by molecular identification techniques were evaluated by detection of the hsp65 and rpoB genes and sequencing of conserved fragments of these genes. All strains identified as M. avium were genotyped using the eight-locus mycobacterial interspersed repetitive unit-variable-number tandem-repeat method.

Results:

We found that NTM accounted for 25 (7.5%) of the 332 mycobacteria isolated. Of those 25, 18 (72%) were M. avium, 5 (20%) were M. abscessus, 1 (4%) was M. gastri, and 1 (4%) was M. kansasii. The 18 M. avium strains showed high diversity, only two strains being genetically related.

Conclusions:

These results highlight the need to consider the investigation of NTM in patients with suspected active tuberculosis who present with positive cultures, as well as to evaluate the genetic diversity of M. avium strains.