Mycobacterium haemophilum: microbiology and expanding clinical and geographic spectra of disease in humans

Mycobacterium haemophilum infection in immunocompetent adults: a literature review and case report

BACKGROUND

Mycobacterium haemophilum has been increasingly found in severely immunocompromised patients but is scarcely reported in immunocompetent adults.

METHODS

We systematically reviewed previous literature to identify studies on infection in immunocompetent adults. Articles reporting at least one case of M. haemophilum infection were included. We excluded articles involving patients who had immunosuppression-related diseases and routinely used glucocorticoids or immunosuppressants. We also reported a case of a young immunocompetent woman infected by M. haemophilum along the eyebrows, which was probably due to the use of an eyebrow pencil retrieved from a sink drain.

RESULTS

Twelve qualifying articles reporting M. haemophilum infection in immunocompetent adults were identified. Among them, most cases report skin lesions along the eyebrows, and the remaining had cervicofacial lymphadenitis, lesions on the arm or fingers, inflammation in the eyeballs, or ulceration in the perineal region. Most cases were caused by tattoos, make-up, injury, or surgical operation. For diagnosis, specialized tissue culture sensitivity was roughly 75%, and polymerase chain reaction (PCR) test sensitivity was approximately 89%. Triple antibiotic therapy for 3 to 24 months, or surgical excision was effective in controlling infection.

CONCLUSION

M. haemophilum infection should be considered if routine antibacterial and glucocorticoid treatments are ineffective against the disease, even in healthy adults. To definitively diagnose this infection, conditioned tissue culture or PCR testing is required. Treatment usually involves a combination of multiple antibiotics and, if necessary, surgical removal of infected tissue.

Mycobacterium haemophilum infection with cutaneous involvement: two case reports and an updated literature review: Mycobacterium haemophilum skin infection

Mycobacterium haemophilum (MH) is a slow-growing, non-tuberculous Mycobacterium that most commonly causes infections in immunocompromised patients. The skin is the most prevalent site of infection and can be an isolated presentation or part of a disseminated disease. Herein, we reported a case of isolated MH infection of the hand and a case of disseminated MH infection with multiple skin lesions. In addition, other MH cases with cutaneous involvement over the last 10 years, from 2011-2022, were reviewed and analyzed. Among the 79 included cases, the common skin findings in MH infections included nodules, ulcers, abscesses, swelling, and pustules. Middle-aged patients with iatrogenic immunosuppression from glucocorticoids, mycophenolate mofetil, cyclosporine, and cyclophosphamide are the most susceptible to MH infection, with a higher risk of dissemination to internal organs. Disseminated MH infections commonly present as tenosynovitis, arthritis/arthralgia, or osteomyelitis. There is a lack of strong evidence for treatment; however, triple therapy of quinolone, macrolides, and rifampicin is most often used in clinical practice. The overall prognosis is good. The presence of iatrogenic immunocompromised diseases, lesions involving the proximal limbs, and dissemination of MH infections are associated with worse clinical outcomes.

Hautbeteiligung bei Infektionen mit Mycobacterium haemophilum: Zwei Fallberichte und eine aktualisierte Literaturübersicht: Mycobacterium haemophilum infection with cutaneous involvement: Two case reports and an updated literature review

Mycobacterium haemophilum (MH) ist ein langsam wachsendes, nicht‐tuberkulöses Mykobakterium. Infektionen treten am häufigsten bei Patienten mit beeinträchtigtem Immunsystem auf; sie manifestieren sich meist an der Haut und kommen isoliert oder bei disseminierten Infektionen vor. Wir berichten hier über einen Fall mit isolierter MH‐Infektion an der Hand sowie über einen weiteren Fall von disseminierter MH‐Infektion mit multiplen Hautläsionen. Zusätzlich haben wir weitere Fallberichte über MH‐Infektionen mit kutaner Beteiligung aus den letzten zehn Jahren (2011–2022) ausgewertet. Die am häufigsten beobachteten Hautmanifestationen der insgesamt 79 Fälle waren Knötchen, Ulzera, Abszesse, Schwellungen und Pusteln. Patienten mittleren Alters mit iatrogener Immunsuppression durch Glucocorticoide, Mycophenolat‐Mofetil, Ciclosporin und Cyclophosphamid scheinen besonders anfällig für MH‐Infektionen zu sein und haben auch ein höheres Risiko für eine Dissemination in die inneren Organe. Disseminierte MH‐Infektionen manifestieren sich gewöhnlich als Tenosynovitis, Arthritis/Arthralgie oder Osteomyelitis. Derzeit gibt es keine starke Evidenz für bestimmte Therapeutika; in der Praxis wird am häufigsten eine Dreifachkombination aus Chinolon, Makroliden und Rifampicin eingesetzt. Die Prognose ist allgemein gut. Iatrogene Immunsuppression, Läsionen im proximalen Bereich der Extremitäten sowie disseminierte Manifestation sind mit schlechteren klinischen Verläufen assoziiert.

A Systemic Lupus Erythematosus Patient with Cutaneous Mycobacterium haemophilum Infection under Belimumab Treatment: A Case Report

A 38-year-old female with systemic lupus erythematosus (SLE) initiated belimumab treatment. One month later, she presented with a reddish painful swelling on her right lower leg. She was treated with ceftriaxone and vancomycin. However, novel erythematous papules and indurated nodules appeared on both her lower legs. Skin biopsy revealed microabscess formation with mixed cell granuloma surrounded by inflammatory cell infiltration within the dermis with subcutaneous fat tissue. A large number of acid-fast bacilli were observed with Ziehl-Neelsen staining. DNA sequencing of both the hsp65 and the 16S rRNA sequences showed a 100% match with the corresponding region of Mycobacterium haemophilum. Mycobacterial culture revealed satellite growth enhancement on Middlebrook 7H11 agar plates around a paper strip containing hemin. She was treated with levofloxacin, rifabutin, and ethambutol. Within 13 months, her cutaneous lesions improved markedly without any side effects. The B cell-targeted biologic belimumab, a fully humanized IgG1γ monoclonal antibody that inactivates B lymphocyte stimulator, has been considered to be beneficial for active SLE. However, this therapy could increase the risk for the development of biologic therapy-associated mycobacterial infections, both tuberculosis and nontuberculous mycobacteria infections.

[Two severe cases of disseminated cutaneous nontuberculous mycobacteriosis due to Mycobacterium haemophilum]

Mycobacterium haemophilum is a rare pathogen belonging to the group of slowly growing nontuberculous mycobacteria (NTM) that can cause infections, especially in immunocompromised patients. Detection by culturing is difficult because M. haemophilum only grows under special cultivation conditions. Therefore, it is believed that the pathogen is too rarely identified as a cause of disease overall. In addition to patients with severe immunodeficiency, e.g. due to acquired immunodeficiency syndrome (AIDS), chemotherapy or immunosuppression after transplantation, patients with underlying rheumatic diseases are increasingly described in the literature, who are at risk due to the immunosuppressive treatment regimen. Clinically, ulcerative skin alterations, lymphadenopathy and arthropathy are in the foreground. In immunosuppressed patients with unclear skin lesions, infections due to M. haemophilum should be considered and specific microbiological diagnostics should be initiated.

Case report: Subcutaneous Mycobacterium haemophilum infection in an immunocompetent patient after lipolysis injections

Mycobacterium haemophilum is a slow-growing, aerobic mycobacterium that acts as a pathogen in immunocompromised adult patients and immunocompetent children. There are only a few rare cases in the literature describing this species as a cause of subcutaneous infections. Here, we describe a subcutaneous infection caused by M. haemophilum in an immunocompetent female after lipolysis injections at an unqualified beauty salon, suggesting that this bacteria can also be a potential causative agent of adverse events in medical aesthetics. In addition, M. haemophilum caused lesions not only at the injection sites and adjacent areas but also invaded distant sections through the subcutaneous sinus tracts. Thus, early diagnosis and appropriate treatment are vital to prevent further deterioration and improve prognosis.

Osteomyelitis due to Mycobacterium haemophilum in an adult renal transplant recipient

Mycobacterium haemophilum is an increasingly recognized pathogen of the non-tuberculous mycobacteria family that largely infects immunocompromised adults and immunocompetent children. M. haemophilum is a fastidious and slow-growing organism that exhibits preferential growth at lower temperature with iron supplemented media, and therefore most clinical manifestations involve cutaneous infection or musculoskeletal infection of the distal extremities. It is believed that opportunistic infection occurs in immunocompromised hosts when the organism is acquired through environmental exposure. We describe the case of a 71-year-old renal transplant recipient who developed acute M. haemophilum osteomyelitis of the left foot, likely contracted from Epsom salt soaks with contaminated tap water. Outcomes of M. haemophilum infection are generally favorable in the literature. Our patient was treated with local debridement and partial amputation followed by a 3-drug anti-mycobacterial regimen until definitive amputation could be completed.

Construction and Analysis of the Complete Genome Sequence of Leprosy Agent Mycobacterium lepromatosis

Leprosy is caused by Mycobacterium leprae and Mycobacterium lepromatosis. We report construction and analyses of the complete genome sequence of M. lepromatosis FJ924. The genome contained 3,271,694 nucleotides to encode 1,789 functional genes and 1,564 pseudogenes. It shared 1,420 genes and 885 pseudogenes (71.4%) with M. leprae but differed in 1,281 genes and pseudogenes (28.6%). In phylogeny, the leprosy bacilli started from a most recent common ancestor (MRCA) that diverged ~30 million years ago (Mya) from environmental organism Mycobacterium haemophilum. The MRCA then underwent reductive evolution with pseudogenization, gene loss, and chromosomal rearrangements. Analysis of the shared pseudogenes estimated the pseudogenization event ~14 Mya, shortly before species bifurcation. Afterwards, genomic changes occurred to lesser extent in each species. Like M. leprae, four major types of highly repetitive sequences were detected in M. lepromatosis, contributing to chromosomal rearrangements within and after MRCA. Variations in genes and copy numbers were noted, such as three copies of the gene encoding bifunctional diguanylate cyclase/phosphodiesterase in M. lepromatosis, but single copy in M. leprae; 6 genes encoding the TetR family transcriptional regulators in M. lepromatosis, but 11 such genes in M. leprae; presence of hemW gene in M. lepromatosis, but absence in M. leprae; and others. These variations likely aid unique pathogenesis, such as diffuse lepromatous leprosy associated with M. lepromatosis, while the shared genomic features should explain the common pathogenesis of dermatitis and neuritis in leprosy. Together, these findings and the genomic data of M. lepromatosis may facilitate future research and care for leprosy. IMPORTANCE Leprosy is a dreaded infection that still affects millions of people worldwide. Mycobacterium lepromatosis is a recently recognized cause in addition to the well-known Mycobacterium leprae. M. lepromatosis is likely specific for diffuse lepromatous leprosy, a severe form of the infection and endemic in Mexico. This study constructed and annotated the complete genome sequence of M. lepromatosis FJ924 and performed comparative genomic analyses with related mycobacteria. The results afford new and refined insights into the genome size, gene repertoire, pseudogenes, phylogenomic relationship, genome organization and plasticity, process and timing of reductive evolution, and genetic and proteomic basis for pathogenesis. The availability of the complete M. lepromatosis genome may prove to be useful for future research and care for the infection.

Disseminated cutaneous Mycobacterium haemophilum infection in a patient on infliximab for rheumatoid arthritis

Mycobacterium haemophilum is a rarely encountered pathogen that is difficult to identify given its unique growth requirements. It is most often seen in adult patients who are immunosuppressed due to advanced HIV or haematological malignancy. Our case highlights a typical presentation of an atypical pathogen in a patient with rheumatoid arthritis receiving anti-tumour necrosis factor therapy. This case represents an important patient population in whom this previously rare infection is increasingly common.

Nontuberculous Mycobacteria

Nontuberculous mycobacteria (NTM) are ubiquitous in the environment and 193 species of NTM have been discovered thus far. NTM species vary in virulence from benign environmental organisms to difficult-to-treat human pathogens. Pulmonary infections remain the most common manifestation of NTM disease in humans and bronchiectasis continues to be a major risk factor for NTM pulmonary disease (NTM PD). This article will provide a useful introduction and framework for clinicians involved in the management of bronchiectasis and NTM. It includes an overview of the epidemiology, pathogenesis, diagnosis, and management of NTM PD. We will address the challenges faced in the diagnosis of NTM PD and the importance of subspeciation in guiding treatment and follow-up, especially in Mycobacterium abscessus infections. The treatment of both Mycobacterium avium complex and M. abscessus, the two most common NTM species known to cause disease, will be discussed in detail. Elements of the recent ATS/ERS/ESCMID/IDSA NTM guidelines published in 2020 will also be reviewed.

Fatal disseminated Mycobacterium haemophilum infection involving the central nervous system in a renal transplant recipient

Mycobacterium haemophilum is a slow growing nontuberculous mycobacterium which prefers cooler temperatures and requires iron for growth. It usually causes skin and soft tissue infections in immunocompromised hosts and cervical lymphadenitis in healthy children. We present the case of fatal disseminated M. haemophilum in an immunocompromised host with central nervous system (CNS) involvement. Our case is a 65-year-old Hispanic male with history of end-stage renal disease status post renal transplantation six years prior (on maintenance immunosuppression with mycophenolate, tacrolimus and prednisone), diabetes mellitus type 2, coronary artery disease, ventricular arrhythmias with implantable cardioverter defibrillator, prior stroke and cochlear implant. In the four months preceding admission to our institution he had frequent hospitalizations for altered mental status (AMS), sepsis syndromes and failure to thrive. Two months prior to presentation he developed progressive swelling and redness of the wrists, right third and left fifth digits. Computed tomography (CT) showed extensive cellulitis in distal right forearm and hand with chronic osteomyelitis. Serial incision and drainage (I&D) of right wrist yielded positive AFB stain and growth on AFB culture. PCR was negative for Mycobacterium tuberculosis. Patient was started on rifampin, clarithromycin and ethambutol. Two days later patient developed AMS and severe septic shock requiring transfer to our facility. CT head revealed indeterminate lesion in the left frontal lobe along with nonspecific hypodensities in the pons and thalamus. Repeat CT upper extremities showed osteomyelitis of distal radius and small hand bones with adjacent abscesses. I&D also revealed bilateral tenosynovitis. Cultures were resent. With suspicion for rapidly growing mycobacterial infection, the regimen was changed to linezolid, imipenem and azithromycin. Several changes in antimicrobials were necessary throughout hospitalization due to complicated hospital course. Unfortunately, despite aggressive measures, patient developed multiorgan failure culminating in death 10 days after starting anti-mycobacterial drugs. On the day of death, the organism was identified as M. haemophilum. Susceptibilities were not done as patient had died. On autopsy the brain was noted to have multiple abscesses containing AFB. The organism also grew from the wrists and right finger cultures. M. haemophilum of the CNS is extremely rare and has been reported in HIV or AIDS patients. To our knowledge this is the first reported case of M. haemophilum brain abscesses in a patient without HIV/AIDS. Because of its fastidious growth requirements, M. haemophilum usually shows on acid fast stains but does not grow on routine AFB cultures. Although it prefers lower temperatures for growth and is usually limited to skin and soft tissues, disseminated disease occurs in immunocompromised patients and has high mortality. It is usually treated with a multi drug regimen including clarithromycin, rifampin, ciprofloxacin and amikacin.

Meningomyeloencephalitis secondary to Mycobacterium haemophilum infection in AIDS

Infections by opportunistic non-tuberculous mycobacteria (NTM) are rising in global incidence. One emerging, slowly growing NTM is Mycobacterium haemophilum, which can cause skin, lung, bone, and soft tissue infections in immunocompromised patients as well as lymphadenitis in immunocompetent individuals. Detection of this microorganism is difficult using conventional culture-based methods and few reports have documented involvement of this pathogen within the central nervous system (CNS).

We describe the neuropathologic autopsy findings of a 39-year-old man with AIDS who died secondary to M. haemophilum CNS infection. He initially presented with repeated bouts of pyrexia, nausea and vomiting, and altered mental status that required numerous hospitalizations. CSF infectious workups were consistently negative. His most recent admission identified hyperintensities within the brainstem by MRI and despite antibiotic therapies for suspected CNS infection, he died. Autopsy revealed a swollen brain with marked widening of the brainstem. Microscopic examination of the brain and spinal cord showed focal lymphohistiocytic infiltrates, gliosis and neuronal loss that were associated with acid-fast bacilli (AFB). The brainstem was the most severely damaged and AFB were found to congregate along arterial territories lending support to the notion of hematogenous spread as a mechanism for the organisms’ dissemination. 16S rRNA sequencing on formalin-fixed paraffin-embedded tissue enabled post-mortem identification of M. haemophilum. This sequencing methodology may permit diagnosis on CSF intra-vitam.

Rare infection in patient with rheumatoid arthritis treated with adalimumab

Mycobacterium haemophilum is a rare pathogen, predominately present in the immunocompromised population. It is especially studied in HIV and haematological malignancy patients. Given its unique living conditions, it is often difficult to establish its diagnosis, but it is often suspected by its classic association with ulcerating skin findings. Our case is unique in that our patient is immunocompromised by his rheumatoid arthritis treatment, and presented without any skin lesions, but was found to have this rare pathogen causing a constellation of unusual symptoms.

Hypercalcaemia secondary to disseminated Mycobacterium abscessus and Mycobacterium fortuitum

The incidence and prevalence of nontuberculous mycobacteria (NTM) infection is on the rise with many cases still going unreported. Given the vague and nonspecific clinical features of NTM infections, it is often missed or mistaken for Mycobacterium tuberculosis. The presumption that NTM infections are benign and do not contribute to morbidity no longer holds true. NTM infections need to be considered in patients with disseminated multisystem disease and in those not responding to standard M. tuberculosis treatment. As NTM infection is associated with granuloma formation, it can result in hypercalcaemia. Interestingly, there is evidence that there may be other mechanisms in play contributing to hypercalcaemia besides the increased calcitriol levels.

Cutaneous Infections Due to Nontuberculosis Mycobacterium: Recognition and Management

Nontuberculous mycobacteria (NTM) are a diverse group of organisms that are ubiquitous in the environment, and the incidence of cutaneous infections due to NTM has been steadily increasing. Cutaneous infections due to NTM can be difficult to diagnose, due to their wide spectrum of clinical presentations and histopathological findings that are often nonspecific. A variety of modalities including tissue culture and polymerase chain reaction (PCR) assays may be necessary to identify the organism. Treatment can also be challenging, as it can depend on multiple factors, including the causative organism, the patient's immunological status, and the extent of disease involvement. In this review, we discuss the common presentations of cutaneous NTM infections, diagnostic tools, and treatment recommendations. A multi-disciplinary approach that involves good communication between the clinician, the histopathologist, the microbiologist, and infectious disease specialists can help lead to successful diagnosis and management.

Late-onset postoperative Mycobacterium haemophilum endophthalmitis masquerading as inflammatory uveitis: a case report

Background

Although atypical mycobacteria had been increasingly found in various ocular infections in the past decades, a slow-growing Mycobacterium haemophilum (M. haemophilum) was scarcely reported. Similar to tuberculous infection, the presentation can masquerade as low-grade granulomatous intraocular inflammation with partial response to corticosteroids. Besides, the special requirements for culture make this pathogen difficult to diagnose. The study aims to report the clinical presentation and notify the awareness of NTM endophthalmitis among clinicians. This is the first case report of late-onset, postoperative M. haemophilum endophthalmitis in the literature.

Case presentation

A 66-year-old man with non-insulin-dependent diabetes mellitus (NIDDM) manifested chronic granulomatous inflammation in the left eye after multiple glaucoma surgeries. With a diagnosis of noninfectious panuveitis, he was treated with systemic corticosteroids. The inflammation initially responded to therapy although it subsequently worsened and became purulent endophthalmitis. The vitreous cultures grew M. haemophilum. Intraocular and systemic antimicrobial treatments were administered early, but the patient eventually turned blind.

Conclusions

M. haemophilum endophthalmitis is a rare but serious intraocular complication leading to loss of vision or eyeball. Awareness of atypical mycobacterial infections is necessary especially in patients with impaired immune function, previous intraocular surgery, and corticosteroid resistance. Proper laboratory investigations and treatments should be performed. However, due to the rarity of the disease, the development of guidelines for its investigation and therapy is still challenging.

Other Slow-Growing Nontuberculous Mycobacteria

The list of clinically important slow-growing nontuberculous mycobacteria (NTM) continues to expand as new species are identified and older ones are found to be pathogenic. Based on pigment production, the strains may be classified as photochromogenic, scotochromogenic, or unpigmented. Some of these organisms are not newly discovered but have heretofore been considered virtually nonpathogenic. Previously, many were regarded as contaminants when isolated from clinical specimens. Ubiquitous in nature, many NTM have been isolated from groundwater or tap water, soil, house dust, domestic and wild animals, and birds. Most infections result from inhalation or direct inoculation from environmental sources. They are not spread from person to person. The infections may be localized or disseminated. In most cases, the optimal regimen or duration of therapy has not been firmly established. The results of in vitro susceptibility testing may be used to select a therapeutic regimen. Many experts recommend clarithromycin with companion drugs such as rifampin and ethambutol for most, but not all, slowly growing species. Aminoglycosides, clofazimine, fluoroquinolones, linezolid, pyrazinamide, or trimethoprim-sulfamethoxazole also may be effective against some strains. Immunocompetent patients with clinically significant infections with NTM usually should receive 18 to 24 months of therapy. Infected immunocompromised patients, particularly those with disseminated infection, probably should receive therapy as long as their immune systems remain impaired. Some of the species discussed include Mycobacterium alsiense, M. celatum, M. gordonae, M. haemophilum, M. kyorinense, M. malmoense, M. simiae complex, M. szulgai, M. terrae complex, M. ulcerans, and M. xenopi.

Fifteen-year clinical experience with Mycobacterium haemophilum at the Mayo Clinic: A case series

Mycobacterium haemophilum is an uncommonly encountered acid-fast staining bacillus (AFB) that can cause a broad range of infections. We describe a tertiary care center's experience with M. haemophilum infections identified from 2000 to 2015. Ten adult patients were identified with M. haemophilum infections, and most had immunocompromising conditions. M. haemophilum presented in one of two syndromes: a peripheral cutaneous infection presenting with skin nodularity and local invasion, and a cervicofacial infection involving regional lymph nodes. Duration of therapy was variable (0–18 months) and was dependent on the underlying syndrome and immunological status of the patient. Treatment responses were favorable in all patients. During therapy, three patients developed culture-negative aseptic cutaneous lesions, consistent with immunologic reconstitution inflammatory syndrome (IRIS); we postulate that such reactions may not be uncommon with select M. haemophilum infections.

HIV and mycobacteria

The importance of mycobacteria as opportunistic pathogens, particularly members of the M. avium complex (MAC), in patients with progressive HIV infection was recognized early in the AIDS epidemic. It took longer to appreciate the global impact and devastation that would result from the deadly synergy that exists between HIV and M. tuberculosis. This HIV/M. tuberculosis co-pandemic is ongoing and claiming millions of lives every year. In addition to MAC, a number of other non-tuberculous mycobacteria have been recognized as opportunistic pathogens in HIV-infected individuals; some of these are more commonly encountered (e.g., M. kansasii) than others (M. haemophilum and M. genevense). Finally, there are challenges to concomitantly treating the HIV and the infecting Mycobacterium species, because of antimicrobial resistance, therapeutic side-effects and the complex pharmacologic interactions of the antiretroviral and antimycobacterial multidrug therapy.

Disseminated Mycobacterium haemophilum infection in a renal transplant recipient

Opportunistic infections are a major concern in renal and transplant medicine. We present the case of a renal transplant recipient with a generalised Mycobacterium haemophilum infection after an increase in immunosuppressive therapy and treatment with a tumour necrosis factor-α (TNF-α) inhibitor. Infection involved skin and soft tissue, joints and bones, as well as the renal transplant with an interstitial nephritis. Rapid diagnosis using PCR and DNA sequencing allowed early appropriate treatment. Triple antibiotic therapy and reduction in immunosuppression resulted in a slow but sustained recovery. Immunosuppression causes severe opportunistic infections. TNF-α inhibitors are very effective and well tolerated but have an increased susceptibility to infections with mycobacteria. Mycobacterial infections represent a significant clinical risk to transplant recipients because of their aggressive clinical course and the need for complex toxic antibiotic treatments. In these patients, M. haemophilum is a cause of skin infections.

Mycobacteria

The immunocompromised host is at increased risk of Mycobacterium tuberculosis complex and nontuberculous mycobacteria infection. Although Mycobacterium tuberculosis complex is a significant mycobacterial pathogen, nontuberculous mycobacteria causes substantial disease in those with suppressed immune responses. Mycobacterial infections can cause significant morbidity and mortality in this patient population, and rapid identification and susceptibility testing of the mycobacterial species is paramount to patient management and outcomes. Mycobacterial diagnostics has undergone some significant advances in the last two decades with immunodiagnostics (interferon gamma release assay), microscopy (light-emitting diode), culture (automated broth-based systems), identification (direct PCR, sequencing and matrix-assisted laser-desorption ionization–time of flight mass spectrometry) and susceptibility testing (molecular detection of drug resistance from direct specimens or positive cultures). Employing the most rapid and sensitive methods in the mycobacterial laboratory will have a tremendous impact on patient care and, in the case of Mycobacterium tuberculosis complex, in the control of tuberculosis.

The Complete Genome Sequence of the Emerging Pathogen Mycobacterium haemophilum Explains Its Unique Culture Requirements

Mycobacterium haemophilum is an emerging pathogen associated with a variety of clinical syndromes, most commonly skin infections in immunocompromised individuals. M. haemophilum exhibits a unique requirement for iron supplementation to support its growth in culture, but the basis for this property and how it may shape pathogenesis is unclear. Using a combination of Illumina, PacBio, and Sanger sequencing, the complete genome sequence of M. haemophilum was determined. Guided by this sequence, experiments were performed to define the basis for the unique growth requirements of M. haemophilum. We found that M. haemophilum, unlike many other mycobacteria, is unable to synthesize iron-binding siderophores known as mycobactins or to utilize ferri-mycobactins to support growth. These differences correlate with the absence of genes associated with mycobactin synthesis, secretion, and uptake. In agreement with the ability of heme to promote growth, we identified genes encoding heme uptake machinery. Consistent with its propensity to infect the skin, we show at the whole-genome level the genetic closeness of M. haemophilum with Mycobacterium leprae, an organism which cannot be cultivated in vitro, and we identify genes uniquely shared by these organisms. Finally, we identify means to express foreign genes in M. haemophilum. These data explain the unique culture requirements for this important pathogen, provide a foundation upon which the genome sequence can be exploited to improve diagnostics and therapeutics, and suggest use of M. haemophilum as a tool to elucidate functions of genes shared with M. leprae.

IMPORTANCE

Mycobacterium haemophilum is an emerging pathogen with an unknown natural reservoir that exhibits unique requirements for iron supplementation to grow in vitro. Understanding the basis for this iron requirement is important because it is fundamental to isolation of the organism from clinical samples and environmental sources. Defining the molecular basis for M. haemophilium's growth requirements will also shed new light on mycobacterial strategies to acquire iron and can be exploited to define how differences in such strategies influence pathogenesis. Here, through a combination of sequencing and experimental approaches, we explain the basis for the iron requirement. We further demonstrate the genetic closeness of M. haemophilum and Mycobacterium leprae, the causative agent of leprosy which cannot be cultured in vitro, and we demonstrate methods to genetically manipulate M. haemophilum. These findings pave the way for the use of M. haemophilum as a model to elucidate functions of genes shared with M. leprae.

Disseminated Mycobacterium haemophilum infection in an ASSAM trinket snake (Elaphe frenata)

A sub-adult male Assam trinket snake (Elaphe frenata) that was confiscated from an exotic animal dealer was found dead in its enclosure after a 17-mo quarantine. The snake had grown well during that period and had no physical examination or bloodwork abnormalities during the quarantine. On gross necropsy, masses were found in the epaxial musculature and stomach, the lung was diffusely thickened, the ventricular wall was mottled, and there was intracoelomic and pericardial effusion. Histopathology revealed diffusely disseminated granulomatous infiltrates throughout the lung interstitium and multifocal granulomatous infiltrates in the transmural gastric mass, within the myocardium and pericardial adipose tissue, in the liver and kidney parenchyma, in the cervical region surrounding the trachea and thyroid, and replacing the myofibers of the craniolateral epaxial muscles. Fite-Farracho acid-fast staining revealed numerous intracytoplasmic acid-fast bacilli within macrophages, and polymerase chain reaction testing on frozen tissues followed by nucleic acid sequencing of polymerase chain reaction amplicons identified Mycobacterium haemophilum.

Mycobacterium haemophilum bone and joint infection in HIV/AIDS: case report and literature review

We report a case of disseminated Mycobacterium haemophilum osteomyelitis in a patient with advanced HIV infection, who later developed recurrent immune reconstitution inflammatory syndrome after commencement of antiretroviral therapy. We review previous reports of M. haemophilum bone and joint infection associated with HIV infection and describe the management of M. haemophilum-associated immune reconstitution inflammatory syndrome, including the role of surgery as an adjunctive treatment modality and the potential drug interactions between antiretroviral and antimycobacterial agents.

Microbiological diagnosis of nontuberculous mycobacterial pulmonary disease

Pulmonary disease is by far the most frequent disease caused by nontuberculous mycobacteria (NTM). To diagnose NTM pulmonary disease (NTM-PD), patients should have symptoms and radiologic signs suggestive of NTM-PD, and cultures of multiple respiratory tract samples must grow the same NTM species. Thus, the microbiological laboratory has a central role in the diagnosis of NTM-PD. This review summarizes currently available data on techniques involved in the microbiological diagnosis of NTM-PD, and aims to provide a framework for optimal microbiological diagnosis.

Mycobacterial skin and soft tissue infection

Mycobacterial skin and soft tissue infection (SSTI) includes nontuberculous mycobacterial (NTM) infections, tuberculosis (TB), and leprosy. Diagnosis of mycobacterial SSTI can be challenging due to diverse clinical presentation, low yield from cultured specimens, and nonspecific histopathology on tissue biopsy. In addition, immunosuppressed patients may present with atypical or disseminated disease. Despite aggressive medical treatment and often with surgical intervention, results may be suboptimal with poor outcomes. Regimens typically require multiple antibiotics for extended periods of time and are often complicated by medication side effects and drug-drug interactions. Biopsy with culture is the gold standard for diagnosis, but newer molecular diagnostics and proteomics such as matrix-assisted laser desorption ionization-time of flight mass spectrometry have improved diagnosis with increased identification of clinically significant mycobacteria species in clinically relevant time frames. We will review updates in diagnostic tests along with clinical presentation and treatment of mycobacterial SSTI for NTM, TB, and leprosy.

Mycobacterium haemophilum as the Initial Presentation of a B-Cell Lymphoma in a Liver Transplant Patient

A 66-year-old woman presented with pustular lesions of her face, trunk, and limbs and an acute arthritis of the knees and elbows. She had a complex medical background and had been on immunosuppressants for three years after a liver transplant. Tissue samples from her skin lesions and synovial fluid showed acid-fast bacilli. Mycobacterium haemophilum, an atypical mycobacteria, was later grown on culture. During her treatment with combination antibiotic therapy, she developed a pronounced generalised lymphadenopathy. Histology showed features of a diffuse B-cell lymphoma, a posttransplant lymphoproliferative disorder (PTLD).

Heme uptake mediated by LHR1 is essential for Leishmania amazonensis virulence

The protozoan parasite Leishmania amazonensis is a heme auxotroph and must acquire this essential factor from the environment. Previous studies showed that L. amazonensis incorporates heme through the transmembrane protein LHR1 (Leishmania Heme Response 1). LHR1-null promastigotes were not viable, suggesting that the transporter is essential for survival. Here, we compared the growth, differentiation, and infectivity for macrophages and mice of wild-type, LHR1-single-knockout (LHR1/Δlhr1), and LHR1-complemented (LHR1/Δlhr1 plus LHR1) L. amazonensis strains. LHR1/Δlhr1 promastigotes replicated poorly in heme-deficient media and had lower intracellular heme content than wild-type parasites. LHR1/Δlhr1 promastigotes were also less effective in reducing ferric iron to ferrous iron, a reaction mediated by the heme-containing parasite enzyme LFR1 (Leishmania Ferric Reductase 1). LHR1/Δlhr1 parasites differentiated normally into aflagellated forms expressing amastigote-specific markers but were not able to replicate intracellularly after infecting macrophages. Importantly, the intracellular growth of LHR1/Δlhr1 amastigotes was fully restored when macrophages were allowed to phagocytose red blood cells prior to infection. LHR1/Δlhr1 parasites were also severely defective in the development of cutaneous lesions in mice. All phenotypes observed in LHR1/Δlhr1 L. amazonensis were rescued by expression of episomal LHR1. Our results reveal the importance of efficient heme uptake for L. amazonensis replication and vertebrate host infectivity, reinforcing the potential usefulness of LHR1 as a target for new antileishmanial drugs.

Bedfellows: mycobacteria and rheumatoid arthritis in the era of biologic therapy

In modern times a relationship between tuberculosis (TB) and rheumatoid arthritis (RA) has been firmly recognized, and is primarily attributable to the immunosuppressive therapies used to treat RA. Whereas TB can complicate the successful management of RA, nontuberculous mycobacteria have now perhaps become as important as (if not more so than) TB in the setting of RA, and can represent an even greater challenge to the rheumatologist wishing to use immunosuppressive therapies. This article reviews our most recent understanding of the epidemiological and clinical aspects of mycobacterial disease as it relates to RA, and the existing and emerging immunosuppressive therapies used to treat this disease.

Transition metal-α-amino acid complexes with antibiotic activity against Mycobacterium spp

Synthetic iridium-, rhodium-, and ruthenium-amino acid complexes with hydrophobic l-amino acids have antibiotic activity against Mycobacterium spp., including Mycobacterium bovis BCG and the rapidly growing species Mycobacterium abscessus and Mycobacterium chelonae. Concentrations of transition metal-amino acid complexes demonstrating hemolysis or cytotoxicity were 10- to 25-fold higher than were the MICs.

Disseminated Mycobacterium haemophilum infection in a 72-year-old patient with rheumatoid arthritis on infliximab

Mycobacterium haemophilum is a slow growing, aerobic, fastidious mycobacterium requiring hemin and a temperature of 30-32° C for optimal growth that is ubiquitous in nature. Disease in immunocompromised adults typically manifests as skin lesions such as papules, pustules and ulcerations. This organism also causes lymphadenitis in immunocompetent children. Antitumour necrosis factor-α (anti-TNF-α) therapy with agents such as infliximab, etanercept and adalimumab is increasingly being used for immunosuppression in patients with various autoimmune conditions. These agents are known to place patients at increased risk for tuberculosis and other granulomatous diseases. However, little is known about illness caused by M haemophilum in patients on immunosuppression with anti-TNF-α therapy. We describe a case of disseminated M haemophilum manifesting as skin lesions in a 72-year-old man with rheumatoid arthritis on infliximab and methotrexate.

Antimicrobial susceptibility testing, drug resistance mechanisms, and therapy of infections with nontuberculous mycobacteria

Within the past 10 years, treatment and diagnostic guidelines for nontuberculous mycobacteria have been recommended by the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA). Moreover, the Clinical and Laboratory Standards Institute (CLSI) has published and recently (in 2011) updated recommendations including suggested antimicrobial and susceptibility breakpoints. The CLSI has also recommended the broth microdilution method as the gold standard for laboratories performing antimicrobial susceptibility testing of nontuberculous mycobacteria. This article reviews the laboratory, diagnostic, and treatment guidelines together with established and probable drug resistance mechanisms of the nontuberculous mycobacteria.

Clinical manifestations, diagnosis, and treatment of Mycobacterium haemophilum infections

Mycobacterium haemophilum is a slowly growing acid-fast bacillus (AFB) belonging to the group of nontuberculous mycobacteria (NTM) frequently found in environmental habitats, which can colonize and occasionally infect humans and animals. Several findings suggest that water reservoirs are a likely source of M. haemophilum infections. M. haemophilum causes mainly ulcerating skin infections and arthritis in persons who are severely immunocompromised. Disseminated and pulmonary infections occasionally occur. The second at-risk group is otherwise healthy children, who typically develop cervical and perihilar lymphadenitis. A full diagnostic regimen for the optimal detection of M. haemophilum includes acid-fast staining, culturing at two temperatures with iron-supplemented media, and molecular detection. The most preferable molecular assay is a real-time PCR targeting an M. haemophilum-specific internal transcribed spacer (ITS), but another approach is the application of a generic PCR for a mycobacterium-specific fragment with subsequent sequencing to identify M. haemophilum. No standard treatment guidelines are available, but published literature agrees that immunocompromised patients should be treated with multiple antibiotics, tailored to the disease presentation and underlying degree of immune suppression. The outcome of M. haemophilum cervicofacial lymphadenitis in immunocompetent patients favors surgical intervention rather than antibiotic treatment.

Tattoo-associated Mycobacterium haemophilum skin infection in immunocompetent adult, 2009

After a laboratory-confirmed case of Mycobacterium haemophilum skin infection in a recently tattooed immunocompetent adult was reported, we investigated to identify the infection source and additional cases. We found 1 laboratory-confirmed and 1 suspected case among immunocompetent adults who had been tattooed at the same parlor.