CNS infections caused by Mycobacterium abscessus complex: clinical features and antimicrobial susceptibilities of isolates

Mycobacterial biofilms: Understanding the genetic factors playing significant role in pathogenesis, resistance and diagnosis

Even though the genus Mycobacterium is a diverse group consisting of a majority of environmental bacteria known as non-tuberculous mycobacteria (NTM), it also contains some of the deadliest pathogens (Mycobacterium tuberculosis) in history associated with chronic disease called tuberculosis (TB). Formation of biofilm is one of the unique strategies employed by mycobacteria to enhance their ability to survive in hostile conditions. Biofilm formation by Mycobacterium species is an emerging area of research with significant implications for understanding its pathogenesis and treatment of related infections, specifically TB. This review provides an overview of the biofilm-forming abilities of different species of Mycobacterium and the genetic factors influencing biofilm formation with a detailed focus on M. tuberculosis. Biofilm-mediated resistance is a significant challenge as it can limit antibiotic penetration and promote the survival of dormant mycobacterial cells. Key genetic factors promoting biofilm formation have been explored such as the mmpL genes involved in lipid transport and cell wall integrity as well as the groEL gene essential for mature biofilm formation. Additionally, biofilm-mediated antibiotic resistance and pathogenesis highlighting the specific niches, sites of infection along with the possible mechanisms of biofilm dissemination have been discussed. Furthermore, drug targets within mycobacterial biofilm and their role as potential biomarkers in the development of rapid diagnostic tools have been highlighted. The review summarises the current understanding of the complex nature of Mycobacterium biofilm and its clinical implications, paving the way for advancements in the field of disease diagnosis, management and treatment against its multi-drug resistant species.

Difficulty in diagnosing intracranial infection caused by Mycobacterium avium in an AIDS patient: case report and review of the literature

BACKGROUND

Mycobacterium avium complex (MAC) is an uncommon clinical pathogen, especially in the central nervous system (CNS), and carries a poor prognosis. MAC infections commonly present as immune reconstitution disease (IRD) in HIV patients. Herein, we report a case of intracranial infection caused by MAC in an AIDS patient without disseminated MAC (DMAC) and immune reconstitution inflammatory syndrome (IRIS).

CASE PRESENTATION

A 31-year-old HIV-positive male presented us with progressively worsening CNS symptoms, and neuroimaging revealed ring-enhancing lesions. The intracranial lesions worsened after the empirical therapy for toxoplasma encephalitis and fungal infection. Due to the rapid progression of the disease, the patient died. Mycobacterium avium was the only pathogen in brain tissue after cultures and molecular biology tests.

CONCLUSION

MAC infection in CNS is challenging to diagnose in HIV patients. Our findings emphasize that obtaining tissue samples and applying molecular biology methods is essential to help diagnose the patient as soon as possible to receive adequate treatment.

Intracranial infection caused by Mycobacterium rhodesiae with specific imaging findings and good response to medication: a case report and literature review

Nontuberculous mycobacteria (NTM) are exceedingly rare etiological agents of intracranial infections. Among them, Mycobacterium rhodesiae stands out as an even less common pathogen. In this paper, we report the first documented case of a central nervous system (CNS) infection in humans caused by Mycobacterium rhodesiae, which has specific imaging findings and good response to the therapy by using Linezolid, Clarithromycin, and Minocycline. The diagnosis was facilitated by a comprehensive multimodal approach, incorporating multisite imaging, cerebrospinal fluid analysis via next-generation sequencing (NGS), and targeted genetic testing. Furthermore, this paper provides a derivation of the clinical characteristics observed in other documented instances of CNS infections attributable to NTM and based on a review of the current literature. Our experience contributes to the evidence that is needed to understand the full spectrum of NTM-related CNS pathologies and underscores the importance of a multidisciplinary diagnostic process in atypical presentations of intracranial infections.

Neurological manifestations of nontuberculous mycobacteria in adults: case series and review of the literature

Introduction

Nontuberculous mycobacteria (NTM) mediated infections are important to consider in cases with neuroinflammatory presentations. We aimed to characterize cases of NTM with neurological manifestations at the National Institutes of Health (NIH) Clinical Center and review the relevant literature.

Materials and methods

Between January 1995 and December 2020, six cases were identified. Records were reviewed for demographic, clinical, and radiological characteristics. A MEDLINE search found previously reported cases. Data were extracted, followed by statistical analysis to compare two groups [cases with slow-growing mycobacteria (SGM) vs. those with rapidly growing mycobacteria (RGM)] and evaluate for predictors of survival. NIH cases were evaluated for clinical and radiological characteristics. Cases from the literature were reviewed to determine the differences between SGM and RGM cases and to identify predictors of survival.

Results

Six cases from NIH were identified (age 41 ± 13, 83% male). Five cases were caused by SGM [Mycobacterium avium complex (MAC) n = 4; Mycobacterium haemophilum n = 1] and one due to RGM (Mycobacterium abscessus). Underlying immune disorders were identified only in the SGM cases [genetic (n = 2), HIV (n = 1), sarcoidosis (n = 1), and anti-interferon-gamma antibodies (n = 1)]. All cases were diagnosed using tissue analysis. A literature review found 81 reports on 125 cases (SGM n = 85, RGM n = 38, non-identified n = 2). No immune disorder was reported in 26 cases (21%). Within SGM cases, the most common underlying disease was HIV infection (n = 55, 65%), and seizures and focal lesions were more common. In RGM cases, the most common underlying condition was neurosurgical intervention or implants (55%), and headaches and meningeal signs were common. Tissue-based diagnosis was used more for SGM than RGM (39% vs. 13%, p = 0.04). Survival rates were similar in both groups (48% SGM and 55% in RGM). Factors associated with better survival were a solitary CNS lesion (OR 5.9, p = 0.01) and a diagnosis made by CSF sampling only (OR 9.9, p = 0.04).

Discussion

NTM infections cause diverse neurological manifestations, with some distinctions between SGM and RGM infections. Tissue sampling may be necessary to establish the diagnosis, and an effort should be made to identify an underlying immune disorder.

Epidemiology, clinical presentation, and predictors of outcome in nontuberculous mycobacterial central nervous system infection: a systematic review

BACKGROUND

CNS manifestations represent an emerging facet of NTM infection with significant mortality. Due to protean presentation and low index of suspicion, many cases are often treated erroneously as tubercular meningitis or fungal infections.

OBJECTIVES

Literature on NTM CNS disease is scarce, with most available data on pulmonary disease. This systematic review aimed to evaluate the epidemiology, clinical presentation, diagnostic modalities, and predictors of outcome in CNS NTM infection.

METHODS

The literature search was performed in major electronic databases (PubMed, Google Scholar, and Scopus) using keywords "CNS," "Central nervous system," "brain abscess," "meningitis," "spinal," "Nontuberculous mycobacteria," "NTM". All cases of CNS NTM infection reported between January 1980 and December 2022 were included.

RESULTS

A total of 77 studies (112 cases) were included in the final analysis. The mean age of all patients was 38 years, with most patients male (62.5%). Mycobacterium avium complex (MAC) was the most common aetiology, followed by M. fortuitum and M. abscessus (34.8%, 21.4% and 15.2%, respectively). The disseminated disease was found in 33% of cases. HIV (33.9%) and neurosurgical hardware (22.3%) were the common risk factors. Intracranial abscess (36.6%) and leptomeningeal enhancement (28%) were the most prevalent findings in neuroimaging. The overall case fatality rate was 37.5%. On multivariate analysis, male gender (adjusted OR 2.4, 95% CI 1.2-7.9) and HIV (adjusted OR 3.7, 95% CI 1.8-6.1) were the independent predictors of mortality). M. fortuitum infection was significantly associated with increased survival (adjusted OR 0.18, 95% CI (0.08-0.45), p value 0.012).

CONCLUSIONS

Current evidence shows the emerging role of rapid-grower NTM in CNS disease. Male gender and HIV positivity were associated with significant mortality, while M fortuitum carries favourable outcomes.

Mycobacterium abscessus Meningitis Associated with Stem Cell Treatment During Medical Tourism

Mycobacterium abscessus infections have been reported as adverse events related to medical tourism. We report M. abscessus meningitis in a patient who traveled from Colorado, USA, to Mexico to receive intrathecal stem cell injections as treatment for multiple sclerosis. We also review the management of this challenging central nervous system infection.

A Rare Case of Nontuberculous Mycobacterial Abscess Mimicking Brain Tumor in an Immunocompetent Patient

Nontuberculous mycobacteria (NTM) is a type of bacteria that typically infects the pulmonary system, and NTM-central nervous system (CNS) infection, which occurs in the brain, is a very rare disease. A 64-year-old female patient presented with seizures as the main symptom and was found to have a mass of less than 1 cm in the right temporal lobe with accompanying edema. Although diseases such as tumor metastasis and parasitic cyst were suspected, the patient underwent a surgical resection, and NTM-CNS infection with abscess was diagnosed through biopsy. Antibiotic treatment was initiated after surgery, and the patient has been followed up without any significant symptoms. In this report, we review a rare case of NTM-CNS infection and discuss the understanding and treatment of this disease.

Cerebrospinal fluid protein levels are elevated 100 times in a Leptomeningeal metastasis patient: a case report and literature review

Leptomeningeal metastasis (LM) has a high degree of malignancy and high mortality. We describe a patient admitted to hospital with acute lower extremity weakness, dysuria, and high intracranial pressure. Enhanced magnetic resonance imaging (MRI) showed extensive enhancement of the leptomeningeal and spinal meninges with multiple nodular changes and extensive fusion. His cerebrospinal fluid (CSF) was yellow and cloudy, the Pandy test was strongly positive (++++), the protein was 46 g/L (normal range 0.15-0.45 g/L), which attracted our attention. Initially, miliary TB with associated tuberculous meningitis (TBM) was diagnosed, and neurosarcoidosis cannot be ruled out. After poor therapeutic effect of standard antituberculosis (anti-TB) therapy, further inspection found that malignant cells were detected by cerebrospinal fluid (CSF) cytology. PET/CT suggested the diagnosis of LM. The purpose of this paper is to describe the characteristics of atypical diffuse LM. In conclusion, when patient with unexplained high levels of CSF protein, it is necessary to be alert to the diagnosis of LM. Multiple examinations of fresh CSF are helpful to increase the positive detection rate of tumor cells. Early diagnosis and active treatment are conducive to improving survival rate.

The cell envelope of Mycobacterium abscessus and its role in pathogenesis

Mycobacterium abscessus is a nontuberculosis mycobacterium (NTM) that has shown an exponential rise in its ability to cause disease. Due to its ubiquitous presence in the environment, M. abscessus is widely implicated in secondary exacerbations of many nosocomial infections and genetic respiratory disorders, such as cystic fibrosis (CF). Contrary to other rapidly growing NTMs, the cell envelope of M. abscessus harbors several prominent features and undergoes modifications that are responsible for its pathogenesis. Compositional changes of the mycobacterial outer membrane (MOM) significantly decrease the presence of glycopeptidolipids (GPLs) and enable the transition from a colonizing, smooth morphotype into a virulent, rough morphotype. The GPLs are transported to the MOM by the Mycobacterial membrane proteins Large (MmpL), which further act as drug efflux pumps and confer antibiotic resistance. Lastly, M. abscessus possesses 2 type VII secretion systems (T7SS): ESX-3 and ESX-4, both of which have recently been implicated in host-pathogen interactions and virulence. This review summarizes the current knowledge of M. abscessus pathogenesis and highlights the clinically relevant association between the structure and functions of its cell envelope.

Impact on Macrolide Resistance of Genetic Diversity of Mycobacterium abscessus Species

Our previous study identified that the Mycobacterium abscessus subsp. abscessus T28 sequevar does not fully represent inducible macrolide resistance. Thus, we initiated a correlation study between genotypes and phenotypes. In total, 75 isolates from patients with skin and soft tissue infections were enrolled in the study. These strains were tested against 11 antimycobacterial agents using Sensitire RAPMYCO plates and the CLSI-recommended broth microdilution method. In order to analyze erm(41) and partial hsp65, rpoB, secA1, and rrl genes, bacterial genomic DNA was extracted from bacteria. The MEGA X software was used for phylogenetic analyses. The most active agents against most M. abscessus species were amikacin and tigecycline. Clarithromycin was effective toward M. abscessus subsp. massiliense and nearly all M. abscessus subsp. abscessus C28 sequevars. Two varieties of M. abscessus subsp. abscessus T28 sequevars did not represent inducible macrolide resistance. Most M. abscessus species showed intermediate susceptibility to cefoxitin and imipenem. Six additional agents were less effective against M. abscessus species. Following phylogenetic analyses, two outliers of M. abscessus subsp. abscessus T28 sequevars seem to represent no inducible macrolide resistance. In addition, we discovered genetic mosaicism of hsp65, rpoB, and secA1 in M. abscessus species was common. T28 sequevars of M. abscessus subsp. abscessus do not fully represent inducible macrolide resistance. The outlier of erm(41) phylogeny of the M. abscessus subsp. abscessus T28 sequevar is possibly due to macrolide susceptibility. Evaluation of the antimicrobial susceptibility of M. abscessus species is a reliable tool for assisting physicians in selecting the most effective antimycobacterial agent(s). IMPORTANCE Macrolides are the mainstays of the antimycobacterial regimens against Mycobacterium abscessus species (formerly Mycobacterium abscessus complex). erm(41) confers inducible macrolide resistance for M. abscessus subsp. bolletii strains, and the majority of M. abscessus subsp. abscessus T28 sequevars. Furthermore, the acquired macrolide resistance of M. abscessus species is due to a point mutation in rrl. However, not all M. abscessus subsp. abscessus T28 sequevars have inducible macrolide resistance. Exploration of the mechanism of macrolide resistance requires an understanding of genetic diversity. The genetic mosaicism of the erm(41), rpoB, hsp65, and secA1 genes within three subspecies of M. abscessus species is not uncommon. The T28 sequevar of erm(41) confers inducible macrolide resistance to the genetic mosaic strain. The development of new anti-M. abscessus species infection overcoming inducible macrolide resistance and/or acquired macrolide resistance is a crucial issue.

Omadacycline for management of Mycobacterium abscessus infections: a review of its effectiveness, place in therapy, and considerations for use

The Mycobacterium abscessus complex (MABC) is a group of acid-fast, rapidly dividing non-tuberculous mycobacteria (NTM) that include a number of clinically important subspecies, including M. abscessus, M. bolletii, and M. massiliense. These organisms are prevalent in the environment and are primarily associated with human pulmonary or skin and skin structure infections (SSSI) but may cause more deep-seeded disseminated infections and bacteremia in the immunocompromised. Importantly, these NTM are resistant to most first-line anti-tuberculous agents and, due to intrinsic or acquired resistance, exhibit exceedingly low, variable, and geographically distinct susceptibilities to commonly used antibacterial agents including older tetracyclines, macrolides, aminoglycosides, cephalosporins, carbapenems, and sulfamethoxazole-trimethoprim. Omadacycline is a novel third-generation member of the tetracycline family of antibacterials that has recently been demonstrated to have potent anti-NTM effects and clinical efficacy against MABC, including M. abscessus. The purpose of this review is to present a comprehensive and up-to-date assessment on the body of literature on the role of omadacycline for M. abscessus infections. Specifically, the in vitro and in vivo microbiology, mechanisms of action, mechanisms of resistance, clinical pharmacokinetics, clinical efficacy, adverse effects, dosage and administration, and place in therapy of omadacycline in management of M. abscessus infections will be detailed.

Mycobacterium abscessus Ventriculoperitoneal Shunt Infection

Mycobacterium abscessus is a rapidly growing mycobacterium (RGM) known to be abundant in soil, dust and water. Unlike other non-tuberculous mycobacteria, RGM is typically resistant to first-line anti-tuberculosis drugs. These organisms are known to cause community and hospital-acquired infections; however, central nervous system (CNS) infections caused by these pathogens have not been abundantly reported. As the use of vascular catheters and prosthetic devices is becoming more common, a rise in CNS infections secondary to M. abscessus has been noted. Here, we present such a case where the removal of a ventricular catheter was necessary to guarantee source control and eradication of the infection.

A novel DNA chromatography method to discriminate Mycobacterium abscessus subspecies and macrolide susceptibility

Background

The clinical impact of infection with Mycobacterium (M.) abscessus complex (MABC), a group of emerging non-tuberculosis mycobacteria (NTM), is increasing. M. abscessus subsp. abscessus/bolletii frequently shows natural resistance to macrolide antibiotics, whereas M. abscessus subsp. massiliense is generally susceptible. Therefore, rapid and accurate discrimination of macrolide-susceptible MABC subgroups is required for effective clinical decisions about macrolide treatments for MABC infection. We aimed to develop a simple and rapid diagnostic that can identify MABC isolates showing macrolide susceptibility.

Methods

Whole genome sequencing (WGS) was performed for 148 clinical or environmental MABC isolates from Japan to identify genetic markers that can discriminate three MABC subspecies and the macrolide-susceptible erm(41) T28C sequevar. Using the identified genetic markers, we established PCR based- or DNA chromatography-based assays. Validation testing was performed using MABC isolates from Taiwan.

Finding

We identified unique sequence regions that could be used to differentiate the three subspecies. Our WGS-based phylogenetic analysis indicated that M. abscessus carrying the macrolide-susceptible erm(41) T28C sequevar were tightly clustered, and identified 11 genes that were significantly associated with the lineage for use as genetic markers. To detect these genetic markers and the erm(41) locus, we developed a DNA chromatography method that identified three subspecies, the erm(41) T28C sequevar and intact erm(41) for MABC in a single assay within one hour. The agreement rate between the DNA chromatography-based and WGS-based identification was 99·7%.

Interpretation

We developed a novel, rapid and simple DNA chromatography method for identification of MABC macrolide susceptibility with high accuracy.

Funding

AMED, JSPS KAKENHI

Mycobacterium chimaera Encephalitis Following Cardiac Surgery: A New Syndrome

We report the cases of 3 patients with fatal, disseminated Mycobacterium chimaera infections following cardiac surgeries. Progressive neurocognitive decline and death were explained by active granulomatous encephalitis, with widespread involvement of other organs. This syndrome is clinically elusive and, thus, may have caused deaths in prior reported series.

General Overview of Nontuberculous Mycobacteria Opportunistic Pathogens: Mycobacterium avium and Mycobacterium abscessus

Nontuberculous mycobacteria (NTM) are emerging human pathogens, causing a wide range of clinical diseases affecting individuals who are immunocompromised and who have underlying health conditions. NTM are ubiquitous in the environment, with certain species causing opportunistic infection in humans, including Mycobacterium avium and Mycobacterium abscessus. The incidence and prevalence of NTM infections are rising globally, especially in developed countries with declining incidence rates of M. tuberculosis infection. Mycobacterium avium, a slow-growing mycobacterium, is associated with Mycobacterium avium complex (MAC) infections that can cause chronic pulmonary disease, disseminated disease, as well as lymphadenitis. M. abscessus infections are considered one of the most antibiotic-resistant mycobacteria and are associated with pulmonary disease, especially cystic fibrosis, as well as contaminated traumatic skin wounds, postsurgical soft tissue infections, and healthcare-associated infections (HAI). Clinical manifestations of diseases depend on the interaction of the host's immune response and the specific mycobacterial species. This review will give a general overview of the general characteristics, vulnerable populations most at risk, pathogenesis, treatment, and prevention for infections caused by Mycobacterium avium, in the context of MAC, and M. abscessus.

Nontuberculous mycobacterial lung disease epidemiology in Taiwan: A systematic review

Nontuberculous mycobacteria (NTM) are critical emerging global infectious pathogens. Though NTM can be mere colonizers when isolated from human specimens, NTM are also responsible for diverse human infections. NTM-lung disease (NTM-LD) is the most common human disease entity. The present review aims to provide general insight into NTM-LD epidemiology in Taiwan. In reviewing NTM epidemiology in Taiwan, we discovered three distinguishing features. First, NTM disease incidence has increased in Taiwan over the past decade. Second, the distribution of NTM varies geographically in Taiwan. Mycobacterium avium-intracellulare complex (MAC) is the dominant species in northern Taiwan, whereas Mycobacterium abscessus complex and MAC may be equally dominant in southern Taiwan. Third, researchers in Taiwan have published valuable research investigating NTM among special patient populations, including patients in intensive care units, with ventilator dependency, with pulmonary tuberculosis, and who are infected with specific NTM species. The largest obstacle to clarifying NTM epidemiology in Taiwan may be the lack of routine NTM species identification in laboratories. Increased awareness of NTM diseases and acknowledgment that NTM species identification is crucial and guides clinical management are essential steps for facilitating the identification of NTM species in laboratories.

Clinical Characteristics and Treatment Outcomes for Patients Infected with Mycobacterium haemophilum

Mycobacterium haemophilum is a nontuberculous mycobacterium that can infect immunocompromised patients. Because of special conditions required for its culture, this bacterium is rarely reported and there are scarce data for long-term outcomes. We conducted a retrospective study at Siriraj Hospital, Bangkok, Thailand, during January 2012–September 2017. We studied 21 patients for which HIV infection was the most common concurrent condition. The most common organ involvement was skin and soft tissue (60%). Combination therapy with macrolides and fluoroquinolones resulted in a 60% cure rate for cutaneous infection; adding rifampin as a third drug for more severe cases resulted in modest (66%) cure rate. Efficacy of medical therapy in cutaneous, musculoskeletal, and ocular diseases was 80%, 50%, and 50%, respectively. All patients with central nervous system involvement showed treatment failures. Infections with M. haemophilum in HIV-infected patients were more likely to have central nervous system involvement and tended to have disseminated infections and less favorable outcomes.

Pediatric Ventriculoperitoneal Shunt Infection: The Role of Shunt Tract Debridement in Mycobacterium abscessus Eradication

Ventricular shunt infections caused by nontuberculous mycobacteria are uncommon, and those caused by Mycobacterium abscessus are particularly rare. This mycobacterium is intrinsically resistant to first-line anti-tuberculous drugs and is considered the most pathogenic of the atypical, rapidly growing mycobacteria. Given the paucity of reported M. abscessus ventricular shunt infections, the appropriate surgical treatment for these cases, especially in the pediatric setting, has yet to be described. The authors present a 4-year-old male with history of intraventricular hemorrhage resulting in hydrocephalus who presented with an M. abscessus ventricular shunt infection that disseminated to the skin and soft tissue of the entire shunt tract. Despite aggressive antimicrobial therapy, several shunt exchanges, and numerous incisions and debridements of separate infected tract areas, the patient's clinical course was prolonged by multiple relapses and re-admissions. Only after opening and debriding the entire length of the infected tract, which measured 100 cm and extended from the scalp to the groin, and months of intrathecal antibiotics did CSF and tissue culture results become negative, and the entire tract was able to be closed. This article describes the management of the second-encountered pediatric M. abscessus shunt infection along with the management of the 4 previously reported cases. In addition, it highlights the vital role of early, aggressive surgical debridement to achieve infection eradication.

Central Nervous System Infections Caused by Mycobacterium abscessus: Ventricular Shunt Infection in Two Pediatric Patients and Literature Review

A 4-year-old former 24-week gestation male and an 18-month-old former 26-week gestation female, both with history of intraventricular hemorrhage resulting in hydrocephalus, presented with Mycobacterium abscessus ventricular shunt infections affecting both the shunt track and the ventricular fluid. Both children required prolonged combination antimycobacterial therapy; the 4 years old required more than 2 months of triple intravenous antibiotics and intraventricular amikacin to sterilize the cerebrospinal fluid. Each infection came under control only after removal of all foreign material and multiple and extensive adjunctive surgical procedures to excise infected shunt track tissue. Central nervous system infections caused by M. abscessus are rare, and their management is challenging: prolonged antimicrobial therapy is required, adverse effects from antibiotics are common and rates of mortality and morbidity are high.

Unusual cause of progressively impaired cognitive function: Mycobacterium avium complex meningoencephalitis

Mycobacterium avium complex (MAC) is a rare cause of meningoencephalitis. Non-tuberculous mycobacterium meningoencephalitis including MAC meningoencephalitis is an important cause of rapidly progressive dementia. We present a case of MAC meningoencephalitis in an immunosuppressed woman who had progressively impaired cognitive function. An 83-year-old woman who had been taking glucocorticoid for myasthenia gravis developed cognitive dysfunction and visual hallucinations over a period of 2 weeks. Cerebrospinal fluid (CSF) findings were normal, but MAC was positive in CSF culture and M. avium and M. intracellulare were identified by PCR. She was treated with multiple antimycobacterial agents and her symptoms fully recovered. MAC meningoencephalitis is an unusual cause of progressively impaired cognitive function. The possibility of mycobacterial central nervous system infection cannot be excluded by normal CSF findings.

Current significance of the Mycobacterium chelonae-abscessus group

Organisms of the Mycobacterium chelonae-abscessus group can be significant pathogens in humans. They produce a number of diseases including acute, invasive and chronic infections, which may be difficult to diagnose correctly. Identification among members of this group is complicated by differentiating at least eleven (11) known species and subspecies and complexity of identification methodologies. Treatment of their infections may be problematic due to their correct species identification, antibiotic resistance, their differential susceptibility to the limited number of drugs available, and scarcity of susceptibility testing.

Mycobacterium abscessus and β-Lactams: Emerging Insights and Potential Opportunities

β-lactams, the most widely used class of antibiotics, are well-tolerated, and their molecular mechanisms of action against many bacteria are well-documented. Mycobacterium abscessus (Mab) is a highly drug-resistant rapidly-growing nontuberculous mycobacteria (NTM). Only in recent years have we started to gain insight into the unique relationship between β-lactams and their targets in Mab. In this mini-review, we summarize recent findings that have begun to unravel the molecular basis for overall efficacy of β-lactams against Mab and discuss emerging evidence that indicates that we have yet to harness the full potential of this antibiotic class to treat Mab infections.

Mycobacterium abscessus Infections in Children: A Review of Current Literature

There is limited literature on Mycobacterium abscessus infections in children and limited data about its diagnosis and management. The incidence of infections due to M abscessus appears to be increasing in certain populations and can be a significant cause of morbidity and mortality.Management of these infections is challenging and relies on combination antimicrobial therapy and debridement of diseased tissue, depending on the site and extent of disease. Treatment regimens often are difficult to tolerate, and the antimicrobials used can cause significant adverse effects, particularly given the long duration of therapy needed.This review summarizes the literature and includes information from our own institution's experience on pediatric M abscessus infections including the epidemiology, transmission, clinical manifestations, and the management of these infections. Adult data have been used where there are limited pediatric data. Further studies regarding epidemiology and risk factors, clinical presentation, optimal treatment, and outcomes in children are necessary.

Incidental intraoperative diagnosis of Mycobacterium abscessus meningeal infection: a case report and review of the literature

PURPOSE

Mycobacterium abscessus, and rapidly growing mycobacteria in general, are rare but increasing causes of central nervous system (CNS) infections. The aim of this study is to highlight the importance of considering these microorganism in the differential diagnosis of CNS infections, obtaining a prompt diagnosis, and improving clinical outcomes.

METHODS

Case report and literature review.

RESULTS

We report a case of meningeal infection in a patient who underwent decompressive craniectomy after a craniofacial trauma. The diagnosis was made analyzing a sample obtained during a second operation of cranioplasty. A regimen of amikacin, clarithromycin, and imipenem/cilastatin was started. In the following days, the patient experienced a variety of side effects. So, first clarithromycin was replaced with linezolid, then amikacin was stopped and cefoxitin added to the therapy and at the end all the antibiotics were withdrawn. The patient was discharged in good conditions and a clinical interdisciplinary follow-up was started. After 12 months, the patient is still doing well. After a literature analysis, 15 cases of M. abscessus CNS infections were identified. Various modes of acquisition, underlying disease and therapeutic schemes were evident.

CONCLUSIONS

Considering the results of the literature analysis and the increasing incidence of M. abscessus, all specialists involved in the management of CNS infection should be aware of the importance of atypical microorganisms in differential diagnosis.

In Vitro Evaluation of Povidone-Iodine and Chlorhexidine against Outbreak and Nonoutbreak Strains of Mycobacterium abscessus Using Standard Quantitative Suspension and Carrier Testing

Povidone-iodine (PI) and chlorhexidine (CHX) are widely used antiseptics active against conventional Staphylococcus aureus, Enterobacteriaceae, Candida species, and viruses, but their efficacy against Mycobacterium abscessus remains unproven. We determined the in vitro potency of alcoholic PI and CHX against M. abscessus subsp. abscessus (ATCC 19977), M. abscessus subsp. bolletii (BCRC 16915), and our outbreak strain of M. abscessus subsp. massiliense (TPE 101) in reference to Staphylococcus aureus (ATCC 29213) by standard quantitative suspension and carrier methods (EN 14563). By suspension, all mycobacterial strains compared to S. aureus were significantly more resistant to CHX, but not PI. By carrier, the mean logarithmic reductions (LR) achieved by PI under clean (dirty) conditions were 6.575 (2.482), 5.540 (2.298), 4.595 (1.967), and 1.173 (0.889), while those achieved by CHX under clean (dirty) conditions were 3.164 (5.445), 5.307 (2.564), 3.844 (2.232), and 0.863 (0.389) for S. aureus, M. abscessus subsp. bolletii, M. abscessus subsp. abscessus, and M. abscessus subsp. massiliense, respectively. M. abscessus subsp. massiliense (outbreak strain) was significantly more resistant than the other tested strains to PI and CHX. By both methods, the mean LR achieved by PI was higher than for CHX for all mycobacterial strains, but under dirty conditions, neither antiseptic was effectively mycobactericidal (LR < 5). These preliminary findings caution against the universal replacement of PI with CHX as the first-line skin antiseptic, since all M. abscessus isolates were resistant to CHX. More studies are needed to establish the best practice for skin antisepsis if mycobacterial infections are also to be prevented.

Mycobacterium abscessus WhiB7 Regulates a Species-Specific Repertoire of Genes To Confer Extreme Antibiotic Resistance

Mycobacterium abscessus causes acute and chronic bronchopulmonary infection in patients with chronic lung damage, of which cystic fibrosis (CF) patients are particularly vulnerable. The major threat posed by this organism is its high intrinsic antibiotic resistance. A typical treatment regimen involves a 6- to 12-month-long combination therapy of clarithromycin and amikacin, with cure rates below 50% and multiple side effects, especially due to amikacin. In the present work, we show that M. abscessuswhiB7, a homologue of Mycobacterium tuberculosis and Mycobacterium smegmatis whiB7 with previously demonstrated effects on intrinsic antibiotic resistance, is strongly induced when exposed to clinically relevant antibiotics that target the ribosome: erythromycin, clarithromycin, amikacin, tetracycline, and spectinomycin. The deletion of M. abscessuswhiB7 results in sensitivity to all of the above-mentioned antibiotics. Further, we have defined and compared the whiB7 regulon of M. abscessus with the closely related nontuberculous mycobacterium (NTM) M. smegmatis to demonstrate the induction of a species-specific repertoire of genes. Finally, we show that one such gene, eis2, is specifically induced in M. abscessus by whiB7 and contributes to its higher levels of intrinsic amikacin resistance. This species-specific pattern of gene induction might account for the differences in drug susceptibilities to other antibiotics and between different mycobacterial species.

Mycobacterium abscessus Complex Infections in Children: A Review

PURPOSE OF REVIEW

Infections in children with Mycobacterium abscessus complex represent a particular challenge for clinicians. Increasing incidence of these infections worldwide has necessitated focused attention to improve both diagnostic as well as treatment modalities. Published medical literature was reviewed, with emphasis on material published in the past 5 years.

RECENT FINDINGS

Increasing availability of new diagnostic tools, such as matrix-assisted laser desorption ionization-time of flight mass spectrometry and custom PCRs, has provided unique insights into the subspecies within the complex and improved diagnostic certainty. Microbiological review of all recent isolates at the University of Minnesota Medical Center was also conducted, with description of the antimicrobial sensitivity patterns encountered in our center, and compared with those published from other centers in the recent literature. A discussion of conventional antimicrobial treatment regimens, alongside detailed description of the relevant antimicrobials, is derived from recent publications. Antimicrobial therapy, combined with surgical intervention in some cases, remains the mainstay of pediatric care. Ongoing questions remain regarding the transmission mechanics, immunologic vulnerabilities exploited by these organisms in the host, and the optimal antimicrobial regimens necessary to enable a reliable cure. Updated treatment guidelines based on focused clinical studies in children and accounting especially for the immunocompromised children at greatest risk are very much needed.

Mycobacterium abscessus Osteomyelitis of the Calcaneus Presenting as Tumor-Mimicking Lesions: A Case Report

CASE

We present the case of a 51-year-old immunocompetent man with refractory heel pain who initially had been treated for plantar fasciitis. However, the pain was proven to be caused by a Mycobacterium abscessus infection of the calcaneus. The process of diagnosis and treatment is described.

CONCLUSION

Although rare, chronic heel pain can be caused by an atypical mycobacterial infection of the calcaneus. Because of its indolent clinical course, misdiagnosis is not uncommon with calcaneal osteomyelitis. Physicians should note that this rare infection should be considered in patients with refractory heel pain.

The Diverse Cellular and Animal Models to Decipher the Physiopathological Traits of Mycobacterium abscessus Infection

Mycobacterium abscessus represents an important respiratory pathogen among the rapidly-growing non-tuberculous mycobacteria. Infections caused by M. abscessus are increasingly found in cystic fibrosis (CF) patients and are often refractory to antibiotic therapy. The underlying immunopathological mechanisms of pathogenesis remain largely unknown. A major reason for the poor advances in M. abscessus research has been a lack of adequate models to study the acute and chronic stages of the disease leading to delayed progress of evaluation of therapeutic efficacy of potentially active antibiotics. However, the recent development of cellular models led to new insights in the interplay between M. abscessus with host macrophages as well as with amoebae, proposed to represent the environmental host and reservoir for non-tuberculous mycobacteria. The zebrafish embryo has also appeared as a useful alternative to more traditional models as it recapitulates the vertebrate immune system and, due to its optical transparency, allows a spatio-temporal visualization of the infection process in a living animal. More sophisticated immunocompromised mice have also been exploited recently to dissect the immune and inflammatory responses to M. abscessus. Herein, we will discuss the limitations, advantages and potential offered by these various models to study the pathophysiology of M. abscessus infection and to assess the preclinical efficacy of compounds active against this emerging human pathogen.

Rapidly Growing Mycobacteria

Rapidly growing mycobacteria (RGM) compose approximately one-half of the currently validated mycobacterial species and are divided into six major groups, including the Mycobacterium fortuitum group, M. chelonae/M. abscessus complex, M. smegmatis group, M. mucogenicum group, M. mageritense / M. wolinskyi , and the pigmented RGM. This review discusses each group and highlights the major types of infections associated with each group. Additionally, phenotypic and molecular laboratory identification methods, including gene sequencing, mass spectrometry, and the newly emerging whole-genome sequencing, are detailed, along with a discussion of the current antimicrobial susceptibility methods and patterns of the most common pathogenic species.

Identification of nontuberculous mycobacteria in MGIT by matrix-assisted laser desorption/ionization mass spectrometry

Aim: The performance of Bruker Biotyper matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in identifying species of nontuberculous mycobacteria (NTM) in flagged Mycobacteria Growth Indicator Tubes (MGIT)s is unclear. Materials & methods: A total of 92 sequential MGIT-positive nontuberculous mycobacteria isolates, including Mycobacterium intracellulare, M. abscessus complex, M. avium complex and M. avium, were used to compare the performance of the MALDI-TOF MS for species-level identification with that of the BluePoint MycoID plus kit and final identification. Results: A total of 44 (47.8%) and 80 (87.0%) isolates were correctly identified to the species level by the MALDI-TOF MS and BluePoint MycoID plus kit, respectively. Conclusion: The procedure of MALDI-TOF MS in MGITs inoculated with clinical specimens is needed to be further optimized.

Risk Factors and Outcomes of Nontuberculous Mycobacterial Disease among Rheumatoid Arthritis Patients: A Case-Control study in a TB Endemic Area

Increasing evidence indicates that the risk of nontuberculous mycobacteria (NTM) disease is elevated in patients with rheumatoid arthritis (RA). However, the risk factors and outcomes for NTM disease among RA patients remain unclear. We conducted a case-control study and estimated odds ratios (ORs) for RA patients with NTM disease according to comorbidities and anti-rheumatic medications by using conditional logistic regression. Prior tuberculosis history (adjusted OR (aOR) =5.58, p < 0.001), hypertension (aOR = 2.55, p = 0.013), diabetes mellitus (aOR = 3.31, p = 0.005), interstitial lung disease (aOR = 8.22, p < 0.001), chronic obstructive pulmonary disease (aOR = 8.59, p < 0.001) and exposure to oral corticosteroids in a dose-dependent manner (5- < 10 mg/day aOR = 2.51, Ptrend = 0.007) were associated with a significantly increased risk of NTM disease in RA patients. The predominant species causing NTM disease in RA patients was Mycobacterium intracellulare (46.0%). Most NTM isolates were resistant to the majority of the antibiotics that are currently available, which maybe caused treatment failure; hospitalization and mortality are increased. To prevent and treat NTM disease efficiently, we suggested that it is important to monitor the development of NTM disease in RA patients receiving therapy with corticosteroids, particularly in those with predisposing factors.

Mycobacterium abscessus Complex Infections in Humans

New treatments, rapid and inexpensive identification methods, and measures to contain nosocomial transmission and outbreaks are urgently needed.

Mycobacterium abscessus complex comprises a group of rapidly growing, multidrug-resistant, nontuberculous mycobacteria that are responsible for a wide spectrum of skin and soft tissue diseases, central nervous system infections, bacteremia, and ocular and other infections. M. abscessus complex is differentiated into 3 subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. abscessus subsp. bolletii. The 2 major subspecies, M. abscessus subsp. abscessus and M.abscessus subsp. massiliense, have different erm(41) gene patterns. This gene provides intrinsic resistance to macrolides, so the different patterns lead to different treatment outcomes. M. abscessus complex outbreaks associated with cosmetic procedures and nosocomial transmissions are not uncommon. Clarithromycin, amikacin, and cefoxitin are the current antimicrobial drugs of choice for treatment. However, new treatment regimens are urgently needed, as are rapid and inexpensive identification methods and measures to contain nosocomial transmission and outbreaks.

Deciphering and Imaging Pathogenesis and Cording of Mycobacterium abscessus in Zebrafish Embryos

Zebrafish (Danio rerio) embryos are increasingly used as an infection model to study the function of the vertebrate innate immune system in host-pathogen interactions. The ease of obtaining large numbers of embryos, their accessibility due to external development, their optical transparency as well as the availability of a wide panoply of genetic/immunological tools and transgenic reporter line collections, contribute to the versatility of this model. In this respect, the present manuscript describes the use of zebrafish as an in vivo model system to investigate the chronology of Mycobacterium abscessus infection. This human pathogen can exist either as smooth (S) or rough (R) variants, depending on cell wall composition, and their respective virulence can be imaged and compared in zebrafish embryos and larvae. Micro-injection of either S or R fluorescent variants directly in the blood circulation via the caudal vein, leads to chronic or acute/lethal infections, respectively. This biological system allows high resolution visualization and analysis of the role of mycobacterial cording in promoting abscess formation. In addition, the use of fluorescent bacteria along with transgenic zebrafish lines harbouring fluorescent macrophages produces a unique opportunity for multi-color imaging of the host-pathogen interactions. This article describes detailed protocols for the preparation of homogenous M. abscessus inoculum and for intravenous injection of zebrafish embryos for subsequent fluorescence imaging of the interaction with macrophages. These techniques open the avenue to future investigations involving mutants defective in cord formation and are dedicated to understand how this impacts on M. abscessus pathogenicity in a whole vertebrate.

Mycobacterium abscessus Complex Infections in Humans

Mycobacterium abscessus complex comprises a group of rapidly growing, multidrug-resistant, nontuberculous mycobacteria that are responsible for a wide spectrum of skin and soft tissue diseases, central nervous system infections, bacteremia, and ocular and other infections. M. abscessus complex is differentiated into 3 subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. abscessus subsp. bolletii. The 2 major subspecies, M. abscessus subsp. abscessus and M. abscessus subsp. massiliense, have different erm(41) gene patterns. This gene provides intrinsic resistance to macrolides, so the different patterns lead to different treatment outcomes. M. abscessus complex outbreaks associated with cosmetic procedures and nosocomial transmissions are not uncommon. Clarithromycin, amikacin, and cefoxitin are the current antimicrobial drugs of choice for treatment. However, new treatment regimens are urgently needed, as are rapid and inexpensive identification methods and measures to contain nosocomial transmission and outbreaks.

Intracranial abscess due to Mycobacterium avium complex in an immunocompetent host: a case report

Background

Mycobacterium avium complex (MAC) is a ubiquitous pathogen, widely distributed in the environment including water, soil and animals. It is an uncommonly encountered clinical pathogen; primarily causing pulmonary infections in patients with underlying lung disease or disseminated disease in immunocompromised hosts. Sporadically, extra-pulmonary infections have been documented including involvement of the liver, spleen, skin, soft tissue and lymph nodes. Central nervous system (CNS) infections due to MAC are exceedingly rare and carry a poor prognosis. Additionally, such infections are largely reported in patients infected with HIV. Herein we report the first case of intracranial abscess due to MAC in an immunocompetent man with a normal CD4 count and negative HIV status.

Case presentation

A previously healthy 40-year-old male presented to us with progressively worsening CNS symptoms. The patient’s presentation was uncharacteristic of MAC infection in immunocompetent hosts, as he developed subacute, progressive symptoms that included severe frontal headaches, left eyelid swelling, blurry vision, and diplopia, without any pulmonary or systemic manifestations. Neuroimaging revealed multiple ring-enhancing lesions, which required neurosurgical intervention. MAC was the only pathogen that grew from intraoperative tissue cultures. The patient was subsequently treated with a 12-month regimen consisting of Clarithromycin, Ethambutol, and Rifampin, with successful clinical resolution.

Conclusion

Our findings indicate that it is important to consider rare infections such as MAC in immunocompetent patients, regardless of atypical symptoms. Despite the severity of this infection, with timely diagnosis effective treatment is available.

Performance Assessment of the BluePoint MycoID Plus Kit for Identification of Mycobacterium tuberculosis, Including Rifampin- and Isoniazid-resistant Isolates, and Nontuberculous Mycobacteria

The performance of the BluePoint MycoID plus kit (Bio Concept Corporation, Taichung, Taiwan), which was designed to simultaneously detect Mycobacterium tuberculosis (MTB), rifampin- and isoniazid-resistant MTB, and nontuberculous mycobacteria (NTM) was first evaluated with 950 consecutive positive cultures in Mycobacterium Growth Indicator Tube (MGIT) system (BACTEC, MGIT 960 system, Becton-Dickinson, Sparks) from clinical respiratory specimens. The discrepant results between kit and culture-based identification were finally assessed by 16S rRNA gene sequencing and clinical diagnosis. The accuracy rate of this kit for identification of all Mycobacterium species was 96.3% (905/940). For MTB identification, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the kit were 99.7%, 99.3%, 99.0% and 99.8%, respectively. For rifampicin-resistant MTB identification, the sensitivity, specificity, PPV, and NPV of the kit were 100.0%, 99.4%, 91.3%, and 100.0%, respectively, while the corresponding values of isoniazid-resistant MTB identification were 82.6%, 99.4%, 95.0%, and 97.6%, respectively. In identifying specific NTM species, the kit correctly identified 99.3% of M. abscessus (147/148) complex, 100% of M. fortuitum (32/32), M. gordonae (38/38), M. avium (39/39), M. intracellulare (90/90), M. kansasii (36/36), and M. avium complex species other than M. avium and M. intracellulare (94/94). In conclusions, the diagnostic value of the BluePoint MycoID plus kit was superior to culture method for recoveries and identification of NTM to species level. In addition, the diagnostic accuracy of BluePoint MycoID plus kit in MTB identification was similar to conventional culture method with high accuracy rate of rifampicin-resistant M. tuberculosis identification.

Disseminated Mycobacterium abscessus Infection Following Septic Arthritis: A Case Report and Review of the Literature

Mycobacterium abscessus is a rapidly growing mycobacterium found mainly in patients with respiratory or cutaneous infections, but it rarely causes disseminated infections. Little is known about the clinical characteristics, treatment, and prognosis of disseminated M abscessus infection. A 75-year-old Japanese woman who had been treated for 17 years with a corticosteroid for antisynthetase syndrome with antithreonyl-tRNA synthetase antibody developed swelling of her right elbow. X-ray of her right elbow joint showed osteolysis, and magnetic resonance imaging revealed fluid in her right elbow joint. M abscessus grew in joint fluid and blood cultures. She was diagnosed with a disseminated M abscessus infection following septic arthritis. Antimicrobial treatment by clarithromycin, amikacin, and imipenem/cilastatin combined with surgical debridement was administered. Although blood and joint fluid cultures became negative 1 week later, the patient died at 6 weeks from starting antimicrobial treatment. We reviewed 34 cases of disseminated M abscessus infections from the literature. Most of the patients had immunosuppressive backgrounds such as transplantation, use of immunosuppressive agents, hematological malignancy, and end stage renal disease. The duration from onset of symptoms to diagnosis was over 3 months in half of the cases. All fatal cases had positive blood cultures or use of immunosuppressive agents. Clinicians should bear in mind that mycobacterial infections including M abscessus are one of the differential diagnoses in patients with subacute arthritis and soft tissue infections.

Intracranial Mycobacterium abscessus infection in a healthy toddler

We present the first case of pediatric intracranial Mycobacterium abscessus infection in a 16-month-old female with neurofibromatosis type 1. We describe a successful treatment regimen including excisional biopsy combined with high-dose steroids and 16 weeks of triple antimicrobial therapy that resulted in clinical cure and an excellent neurologic outcome.

Diseases caused by nontuberculous mycobacteria in Asia

 The isolation rate of nontuberculous mycobacteria (NTM) species and the prevalence of NTM-associated diseases are on the rise in Asian, as well as in Western countries; however, the species distribution of NTM isolates and the types of diseases caused by NTM species vary from region to region. In this review, we present an update on the epidemiology of NTM in Asia. We demonstrate that the distribution of NTM species varies within Asia and differs from that in North America and Europe. In addition, the clinical manifestations of NTM diseases include respiratory tract infections, disseminated infections, skin and soft tissue infections, lymphadenitis, empyema, ocular infections, CNS infections and genitourinary infections. Finally, the rate of adaptive resistance of anti-NTM antimicrobial agents remains high and may be associated with a poor outcome for patients with NTM diseases.

Central nervous system infection due to Mycobacterium haemophilum in a patient with acquired immunodeficiency syndrome

Mycobacterium haemophilum is an environmental organism that rarely causes infections in humans. We report a patient with acquired immunodeficiency syndrome who had central nervous system infection due to M. haemophilum. The diagnosis required brain tissue procurement and molecular identification method while the treatment outcome was unfavourable.

In vivo assessment of drug efficacy against Mycobacterium abscessus using the embryonic zebrafish test system

Mycobacterium abscessus is responsible for a wide spectrum of clinical syndromes and is one of the most intrinsically drug-resistant mycobacterial species. Recent evaluation of the in vivo therapeutic efficacy of the few potentially active antibiotics against M. abscessus was essentially performed using immunocompromised mice. Herein, we assessed the feasibility and sensitivity of fluorescence imaging for monitoring the in vivo activity of drugs against acute M. abscessus infection using zebrafish embryos. A protocol was developed where clarithromycin and imipenem were directly added to water containing fluorescent M. abscessus-infected embryos in a 96-well plate format. The status of the infection with increasing drug concentrations was visualized on a spatiotemporal level. Drug efficacy was assessed quantitatively by measuring the index of protection, the bacterial burden (CFU), and the number of abscesses through fluorescence measurements. Both drugs were active in infected embryos and were capable of significantly increasing embryo survival in a dose-dependent manner. Protection from bacterial killing correlated with restricted mycobacterial growth in the drug-treated larvae and with reduced pathophysiological symptoms, such as the number of abscesses within the brain. In conclusion, we present here a new and efficient method for testing and compare the in vivo activity of two clinically relevant drugs based on a fluorescent reporter strain in zebrafish embryos. This approach could be used for rapid determination of the in vivo drug susceptibility profile of clinical isolates and to assess the preclinical efficacy of new compounds against M. abscessus.

Bacteraemia caused by Mycobacterium abscessus subsp. abscessus and M. abscessus subsp. bolletii: clinical features and susceptibilities of the isolates

Mycobacterium abscessus complex (M. abscessus subsp. abscessus and M. abscessus subsp. bolletii) is an emerging pathogen causing various human infections. However, few studies have focused on M. abscessus complex bacteraemia with detailed species differentiation. The clinical characteristics of patients with bacteraemia due to M. abscessus complex treated at National Taiwan University Hospital from 2005-2012 were evaluated. Species identification was performed by molecular methods, and minimum inhibitory concentrations (MICs) were determined using a Sensititre RAPMYCO Panel Test for preserved M. abscessus complex isolates. During the study period, 15 patients with M. abscessus complex bacteraemia were found but only 14 isolates from 13 patients were preserved for analysis. One patient had two episodes of bacteraemia (one caused by M. abscessus subsp. bolletii and one by M .abscessus subsp. abscessus with a 9-month interval). Of the remaining 12 patients, 9 patients had M. abscessus subsp. bolletii bacteraemia and 3 had M .abscessus subsp. abscessus bacteraemia. Patients were mainly middle-aged adults with various co-morbidities. Steroid usage and malignancy (5/15) were the most common immunocompromised statuses, followed by diabetes mellitus (4/15). Surgical wound infection was the most common infection foci in all patients (5/15), particularly in M. abscessus subsp. bolletii bacteraemia patients. Clarithromycin and tigecycline exhibited good in vitro activities. Overall, the 14-day mortality was 20% (3/15). M. abscessus complex bacteraemia should be considered an emerging opportunistic infection in immunocompromised hosts. Clarithromycin and tigecycline have potent in vitro activities and are promising agents for treating infections due to M. abscessus complex.

Mycobacterium abscessus cording prevents phagocytosis and promotes abscess formation

Mycobacterium abscessus is a rapidly growing Mycobacterium causing a wide spectrum of clinical syndromes. It now is recognized as a pulmonary pathogen to which cystic fibrosis patients have a particular susceptibility. The M. abscessus rough (R) variant, devoid of cell-surface glycopeptidolipids (GPLs), causes more severe clinical disease than the smooth (S) variant, but the underlying mechanisms of R-variant virulence remain obscure. Exploiting the optical transparency of zebrafish embryos, we observed that the increased virulence of the M. abscessus R variant compared with the S variant correlated with the loss of GPL production. The virulence of the R variant involved the massive production of serpentine cords, absent during S-variant infection, and the cords initiated abscess formation leading to rapid larval death. Cording occurred within the vasculature and was highly pronounced in the central nervous system (CNS). It appears that M. abscessus is transported to the CNS within macrophages. The release of M. abscessus from apoptotic macrophages initiated the formation of cords that grew too large to be phagocytized by macrophages or neutrophils. This study is a description of the crucial role of cording in the in vivo physiopathology of M. abscessus infection and emphasizes cording as a mechanism of immune evasion.

Trypanosoma cruzi necrotizing meningoencephalitis in a Venezuelan HIV⁺-AIDS patient: pathological diagnosis confirmed by PCR using formalin-fixed- and paraffin-embedded-tissues

Coinfections with human immunodeficiency virus (HIV) and infectious agents have been recognized since the early 90s. In the central nervous system (CNS) of HIV⁺ patients, parasitic protozoans like Toxoplasma gondii have been described as responsible for the space occupying lesions (SOL) developed. However, the involvement of Trypanosoma cruzi is also described but appears to be less frequent in acquired immunodeficiency syndrome (AIDS) and transplant recipients, associated with necrotizing myocarditis and neurological symptoms related to the occurrence of necrotizing pseudotumoral encephalitis (NPE) and meningoencephalitis (NME). The present work aims to present a Venezuelan case of NME associated with the coinfection of HIV and a T. cruzi-like trypanosomatid as well as its evolution and diagnosis by histopathological techniques, electron microscopy, and PCR methods using formalin-fixed- (FF-) and paraffin-embedded- (PE-) tissues. Postmortem cytological studies of leptomeninges imprints reveal the presence of trypomastigotes of Trypanosoma sp. Histopathological and electron microscopy studies allowed us to identify an amastigote stage and to reject the involvement of other opportunistic microorganisms as the etiological agent of the SOL. The definitive confirmation of T. cruzi as the etiological agent was achieved by PCR suggesting that the NME by T. cruzi was due to a reactivation of Chagas' disease.