Localized cutaneous infections in immunocompetent individuals due to rapidly growing mycobacteria

Skin and Soft Tissue Nontuberculous Mycobacteria Infection: A Retrospective Case Series of 49 Patients

BACKGROUND

The incidence of skin and soft tissue nontuberculous mycobacteria infection (SSTNI) is increasing. But it may be challenging to diagnose and treat SSTNI.

OBJECTIVE

To summarize course, clinical features, diagnosis and treatment of SSTNI and discuss the association between SSTNI and procedures.

METHODS

A retrospective case series study was conducted among patients diagnosed with SSTNI after surgical procedures. Medical history was collected, disease course and characteristics were analyzed.

RESULTS

49 patients were collected. Among them, 39 (80%) patients were infected with Mycobacterium abscesses. 40 (82%) patients had a history of fat-related procedures. The median and interquartile range of onset time were 15 and 43 days (1-100). Time from first visit to diagnosis was 82±57 days (23-308). Wound healing time was 161±92 days (30-545). The most common symptom were redness (96%), followed by swelling (96%), abscess (84%), pain (80%) and induration (76%). The most common infected site were head and neck (56%), followed by breasts (20%). 6 (12.5%) patients were diagnosed clearly before admission to our department. 10 (28%) patients showed positive acid-fast bacilli (AFB) smears among 36 patients. Treatment included debridement surgeries, drainage and antibiotics.

CONCLUSION

Patient with the above symptoms should be considered as SSTNI. Results of AFB smears are frequently negative after empirical antibiotic treatment so that molecular diagnostic techniques are required for rapid and accurate identification. Debridement surgeries, drainage and sensitive antibiotics are effective. Drug safety and psychological status should be paid attention.

LEVEL OF EVIDENCE IV

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Disseminated cutaneous Mycobacterium chelonae infection secondary to an indwelling catheter in an immunocompetent host

Background

Mycobacterium chelonae is a species of nontuberculous mycobacteria that typically causes localized cutaneous disease in immunocompetent hosts. There have been few reports of disseminated infections in immunocompetent individuals which have often been associated with invasive medical procedures.

Case Presentation

In this report, we describe a 43-year-old immunocompetent female with an implanted venous access device who presented with skin lesions increasing in size and frequency over the course of five months despite antimicrobial therapy. A diagnosis was not made until mycobacterial culture from a skin biopsy grew M. chelonae.

Conclusion

Disseminated cutaneous M. chelonae infection can be a rare complication of indwelling venous catheterization among immunocompetent patients.

Cutaneous Coinfection of Cytomegalovirus and Mycobacterium chelonae Accelerated by Immunosuppression

A mildly diabetic 58-year-old male had traumatic ulceration on the left popliteal fossa, and the lesion progressed to a painful 6 cm deep ulcer. After surgical debridement and skin grafting, ulceration recurred. Pyoderma gangrenosum was clinically diagnosed after the first biopsy, indicating a noninfective ulcer. Immunosuppressive therapy (prednisolone and cyclosporine A) induced complete epithelialization in three months. Four months later, subcutaneous nonulcerated nodules appeared on the anterior area of the left lower leg. Subcutaneous induration progressed and ulceration recurred, so that immunosuppressive therapy continued for one year. Cytomegalovirus (CMV) viremia was detected, and the second biopsy demonstrated CMV inclusions of endothelial and perivascular cells in fibrosing septolobular panniculitis. Cyclosporine A was cancelled, prednisolone was tapered, and ganciclovir started. Viremia soon disappeared, but the lesion progressed to large induration with multiple ulcers measuring up to 3 cm. The third biopsy disclosed infection of Gram-positive mycobacteria, accompanying fat droplet-centered suppurative granulomas without CMV infection. Microbial culture identified Mycobacterium chelonae. Clarithromycin with thermotherapy was effective. A review of the second biopsy confirmed coinfection of CMV and Gram-positive mycobacteria. Immunostaining using a panel of anti-bacterial antibodies visualized the mycobacteria in the lesion. Positive findings were obtained with antibodies to Bacillus Calmette-Guérin, Bacillus cereus, MPT64 (Mycobacterium tuberculosis-specific 24 kDa secretory antigen), LAM (Mycobacterium tuberculosis-related lipoarabinomannan), and PAB (Propionibacterium acnes-specific lipoteichoic acid).

Ex vivo infection of murine precision-cut lung tissue slices with Mycobacterium abscessus: a model to study antimycobacterial agents

Background

Multidrug-resistant infections due to Mycobacterium abscessus often require complex and prolonged regimens for treatment. Here, we report the evaluation of a new ex vivo antimicrobial susceptibility testing model using organotypic cultures of murine precision-cut lung slices, an experimental model in which metabolic activity, and all the usual cell types of the organ are found while the tissue architecture and the interactions between the different cells are maintained.

Methods

Precision cut lung slices (PCLS) were prepared from the lungs of wild type BALB/c mice using the Krumdieck^® tissue slicer. Lung tissue slices were ex vivo infected with the virulent M. abscessus strain L948. Then, we tested the antimicrobial activity of two drugs: imipenem (4, 16 and 64 μg/mL) and tigecycline (0.25, 1 and 4 μg/mL), at 12, 24 and 48 h. Afterwards, CFUs were determined plating on blood agar to measure the surviving intracellular bacteria. The viability of PCLS was assessed by Alamar Blue assay and corroborated using histopathological analysis.

Results

PCLS were successfully infected with a virulent strain of M. abscessus as demonstrated by CFUs and detailed histopathological analysis. The time-course infection, including tissue damage, parallels in vivo findings reported in genetically modified murine models for M. abscessus infection. Tigecycline showed a bactericidal effect at 48 h that achieved a reduction of > 4log₁₀ CFU/mL against the intracellular mycobacteria, while imipenem showed a bacteriostatic effect.

Conclusions

The use of this new organotypic ex vivo model provides the opportunity to test new drugs against M. abscessus, decreasing the use of costly and tedious animal models.

Recurrence of cutaneous Mycobacterium chelonae infection: A case report

Mycobacterium chelonae is a species of mycobacteria that can be found ubiquitously in the environment. It can be found in soil, water, and in aquatic animals. Infections with this pathogen usually involve the soft tissues, eyes, bones, and skin. We present the case of a recurrence of a sporotrichoid cutaneous infection by M. chelonae in an immunocompromised 31-year-old woman with systemic lupus erythematosus. The patient originally developed a swelling of her right foot followed by a sporotrichoid pattern of infection on her right lower leg. A susceptibility profile was established, and treatment with linezolid and clarithromycin was administered for 8 months, in accordance with guidelines from the American Thoracic Society. The patient was clear of new lesions for approximately 1 month before noting a re-emergence. Treatment with linezolid and clarithromycin was re-initiated with subsequent improvement. This case underlines the need for prolonged treatment of this infection in patients with an immunocompromised status.

Cutaneous Nontuberculous Mycobacterial Infections in Alberta, Canada: An Epidemiologic Study and Review

Background:

Cutaneous infections caused by nontuberculous mycobacteria (NTM) occur infrequently. Nonetheless, the incidence of NTM infections is reported to be increasing. In Canada, cutaneous NTM infections have not been well described.

Objectives:

A database review from 2006 to 2016 was done to assess species frequency, incidence, and trends of the most common cutaneous NTMs in the province of Alberta, Canada. We also reviewed major diagnostic and epidemiologic aspects of NTM cutaneous infections with a focus on Mycobacterium marinum.

Results:

A database search identified 244 cases of NTM infections. Mycobacterium avium-intracellulare complex had the highest incidence, causing 64% of cases. Rapid growers ( Mycobacterium abscessus, Mycobacterium chelonae, Mycobacterium fortuitum) caused 23% and M marinum 13%. Information on infection site was available for 117 cases. There was no difference noted in sex distribution; however, differences in age groups between species were noted.

Conclusions:

The incidence of NTM cutaneous infections in Alberta, Canada, was reported for the first time and the incidence of M marinum was found to be similar to that reported in the worldwide literature. Patients’ age groups were different between species. Knowledge of the unique microbiological features of NTMs and the role of the diagnostic laboratory are important.

Isolated subcutaneous nontuberculous mycobacterial infection: a rare case initially mischaracterized as a soft tissue malignancy

The occurrence of nontuberculous mycobacterial (NTM) infection is rare, and the involvement of the musculoskeletal system is even less common. However, the incidence of soft tissue and skin NTM infection is increasing, particularly in patients who undergo injections and minor surgical procedures. Given the non-specific clinical manifestations of NTM infection, the lack of knowledge among physicians regarding this rare infection could lead to inaccurate and delayed diagnosis. Herein, we present a case of an isolated subcutaneous NTM infection caused by Mycobacterium abscessus in the upper back of an immunocompetent 68-year-old woman. The clinical presentation, magnetic resonance imaging findings (including diffusion-weighted imaging), and pathologic findings of subcutaneous NTM infection are described and compared with those of tuberculosis and tumor presentations to provide a more accurate clinical picture for a differential diagnosis.

Mycobacterium chelonae infection complicating traumatic and surgical wounds: A case series

Mycobacterium chelonae is a rapidly growing non-tuberculous mycobacterium. The skin and soft tissue infections due to this organism are steadily on the rise and need to be delineated specifically as most of these are not responsive to routine antituberculosis treatment. Here, we report 3 different presentations caused by Mycobacterium chelonae in traumatic and surgical wounds. Mycobacterium chelonae can complicate surgical or traumatic wounds.This infection may also present as injection site abscesses. Diabetics on insulin injections are especially at risk. A high index of suspicion is necessary in long standing culture negative lesions for clinching the diagnosis. PCR can be helpful in confirming the diagnosis.

Keim oder kein Keim: Herausforderungen bei der Diagnose mykobakterieller Infektionen der Haut

Kutane Mykobakteriosen sind in Deutschland selten. Dennoch ist es für eine frühzeitige Diagnose und anschließende wirksame Behandlung erforderlich, dass diese Krankheitsbilder im ärztlichen Bewusstsein verankert sind. Darüber hinaus stehen Infektionen mit Mykobakterien auf der Liste der Differentialdiagnosen vieler Hautkrankheiten. Diagnosen kutaner Mykobakteriosen beruhen auf klinischen Merkmalen und auf Laboruntersuchungen, einschließlich bakterieller Kulturen, histopathologischer Untersuchungen und PCR-basierten Verfahren. Das Wissen um Möglichkeiten und Grenzen dieser Laboruntersuchungen ist von zentraler Bedeutung, um eine angemessene klinische Entscheidung zu treffen. In diesem Beitrag diskutieren wir die aktuellen diagnostischen Möglichkeiten, die in Verdachtsfällen kutaner Mykobakteriosen zur Verfügung stehen.

Mycobacterium fortuitum infection of the scalp after a skin graft

Mycobacterium fortuitum is a non-tuberculous mycobacterium found in the soil and water of most regions of the world, and it can cause disease in immunocompetent and immunocompromised hosts. We present a 52-year-old man who developed a scalp abscess under a free flap for cranium coverage after a motor vehicle accident. Culture of material drained from the abscess grew M. fortuitum.

Molecular Identification of Nontuberculous Mycobacteria in Humans in Zimbabwe Using 16S Ribosequencing

Background:

Several nontuberculous mycobacteria (NTM) were previously isolated from diverse environments such as water, soil, sewage, food and animals. Some of these NTM are now known to be opportunistic pathogens of humans.

Objective:

The main purpose of the study was to identify NTM isolates stored at the National Microbiology Reference Laboratory (NMRL) and were previously isolated from humans during a national tuberculosis (TB) survey.

Methods:

Pure NTM cultures already isolated from human sputum samples during the national TB survey were retrieved from the NMRL and used for this study. DNA was extracted from the samples and 16S ribosomal RNA gene amplified by polymerase chain reaction. The amplicons were sequenced and bioinformatics tools were used to identify the NTM species.

Results:

Out of total of 963 NTM isolates stored at the NMRL, 81 were retrieved for speciation. Forty isolates (49.4%) were found to belong to Mycobacterium avium-intracellulare complex (MAC) species. The other 41 isolates (50.6%) were identified as M. lentiflavum (6.2%), M. terrae complex (4.9%), M. paraense (4.9%), M. kansasii (3.7%), M. moriokaense (3.7%), M. asiaticum (2.5%), M. novocastrense (2.5%), M. brasiliensis (2.5%), M. elephantis (2.5%), M. paraffinicum (1.2%), M. bohemicum (1.2%), M. manitobense (1.2%), M. intermedium (1.2%), M. tuberculosis complex (1.2%), M. parakoreense (1.2%), M. florentinum (1.2%), M. litorale (1.2%), M. fluoranthenivorans (1.2%), M. sherrisii (1.2%), M. fortuitum (1.2%) and M septicum (1.2%). Two isolates (2.5%) could not be identified, but were closely related to M. montefiorense and M. phlei respectively. Interestingly, the MAC species were the commonest NTM during the survey.

Conclusion:

The study emphasizes the importance of identifying species of NTM in Zimbabwe. Future studies need to ascertain their true diversity and clinical relevance.

Mycobacterium fortuitum induces A20 expression that impairs macrophage inflammatory responses

Mycobacterium fortuitum is a rapidly growing mycobacterium that has been regarded as an etiological agent of a variety of human infections. However, little is known about the host inflammatory responses and the molecular mechanisms by which MF-induced inflammation is regulated in macrophages. In this study, we report that MF infection leads to the induction of an anti-inflammatory molecule, A20 (also known as TNFAIP3), which is essential for the regulation of MF-induced inflammatory responses in murine bone marrow-derived macrophages (BMDMs). MF triggered the expression of tumor necrosis factor-α and interleukin-6 in BMDMs through signaling of the Toll-like receptor 2 (TLR2)-myeloid differentiation primary response gene 88. Additionally, MF rapidly induced the expression of A20, which inhibited proinflammatory cytokine expression and nuclear factor (NF)-κB reporter gene activities in BMDMs. Notably, MF-induced activation of NF-κB signaling was required for A20 expression and proinflammatory responses in BMDMs. Furthermore, the rough morphotype of the MF clinical strain induced a higher level of proinflammatory signaling activation, but less A20 induction in BMDMs, compared to the smooth morphotype. Taken together, these results suggest that MF-induced activation of host proinflammatory responses is negatively regulated through TLR2-dependent A20 expression.