Bug or no bug: challenges in diagnosing cutaneous mycobacterial infections

DNA microarray chip assay in new use: early diagnostic value in cutaneous mycobacterial infection

Introduction

The clinical practicability of DNA microarray chip in detecting the presence of mycobacterial species/isolates directly in the skin tissues has not been evaluated, nor the efficacy of DNA microarray chip as a novel diagnostic tool for the early diagnosis of cutaneous mycobacterial infections is known.

Methods

The present study analyzed the incidence of cutaneous mycobacterial infections in Shanghai and explored the efficacy of a novel DNA microarray chip assay for the clinical diagnosis of the disease from skin tissue specimens compared to traditional detection methods. A total of 60 participants fulfilling the defined diagnostic criteria and confirmed positive for cutaneous mycobacterial infections from 2019 to 2021 were enrolled in the study. Subsequent to recording the participants' medical history and clinical characteristics, the skin tissue specimens were collected for analyses. The specimens underwent histopathological analyses, skin tissue culture, and DNA microarray chip assay.

Results

Increased incidence of cutaneous mycobacterial infection was detected from 2019 to 2021. The most common infecting pathogen was M. marinum followed by M. abscessus. The sensitivity, specificity and accuracy of the skin tissue culture method were 70%, 100% and 76.62%, respectively, while that of the DNA microarray chip assay were 91.67%, 100% and 93.51%, respectively. The sensitivity and accuracy of the DNA microarray chip assay were significantly higher than those of the skin tissue culture method. The positive likelihood and diagnostic odds ratio were >10 and >1, respectively for both the methods. The negative likelihood ratio was significantly higher (30% vs 8.33%) and the Youden's index was significantly lower (70.00% vs 91.67%) in the skin culture method compared to that of the DNA microarray chip assay. There was a significant association of false negative results with a history of antibiotic use in the skin tissue culture method.

Discussion

Given the increasing incidence of cutaneous mycobacterial infections, early diagnosis remains a prime clinical focus. The DNA microarray chip assay provides a simple, rapid, high-throughput, and reliable method for the diagnosis of cutaneous mycobacterial infections with potential for clinical application.

Diagnosis and therapy of Mycobacterium marinum: a single-center 21-year retrospective analysis

BACKGROUND AND OBJECTIVES

In Europe, infections with Mycobacterium (M.) marinum are rare. We conducted a retrospective single-center study to assess the clinical spectrum of M. marinum infection and its diagnosis, treatment and outcome under real-world conditions.

PATIENTS AND METHODS

Eighteen patients presenting with M. marinum infections between 1998 and 2018 were identified in the data warehouse of the University Hospital Würzburg and considered for detailed analysis.

RESULTS

Twelve patients reported aquatic exposure. In 16/18 cases the upper extremities were affected. No invasive infections were detected. Mean time to diagnosis was 15 weeks. Histology revealed granulomatous inflammation in 14 patients while mycobacterial cultures were positive for M. marinum in 16 cases. Most patients received antibiotic monotherapy (14/18) while combination therapy was administered in four cases. Treatment (with a median duration of 10 weeks) was successful in 13 patients. Five patients were lost to follow-up.

CONCLUSIONS

Our retrospective analysis of M. marinum infections at a German tertiary referral center revealed a considerable diagnostic delay and the relevance of microbiological culture, PCR and histology for diagnosis. Monotherapy with clarithromycin (rather than doxycycline) appeared as a reasonable treatment option while immunosuppressed or -compromised patients and those with extended disease received combination therapy.

[Artificial ulcer with perforating bone defect on the scalp due to repeated - scratching attacks in dementia syndrome]

HISTORY

 We report on a 72-year-old demented patient with a palm-sized skin defect on the scalp, who has been manipulating her head several times a day with her fingers but also with sharp objects for many months.

CLINICAL FINDINGS

 A 4 × 6 cm circular, cleanly granulated ulcer was visible on the high parietal surface. On general examination, the patient was little affected: no fever, no signs of inflammation around the ulcer, no evidence of meningitis.

EXAMINATIONS

 There was no histological evidence of the presence of a malignant or benign tumor. A CT of the skull showed a bony defect measuring 2.6 × 3.3 cm without involvement of the dura. The whole body CT without pathological findings.

THERAPY AND COURSE

 First, a protective helmet was made for the patient. Subsequently, a titanium plate was surgically inserted as a bone substitute and the defect was closed by means of transpositionoplasty. In the two-year follow-up, no tumor disease was detected.

CONCLUSION

 Due to the lack of evidence of tumorigenesis in a follow-up period of two years, we evaluate the lesion as an artificial ulcer with perforating bone defect caused by repeated scratching attacks in the context of dementia syndrome.

Diagnosis of Mycobacterium abscessus/chelonae complex cutaneous infection: Correlation of tissue culture and skin biopsy

Mycobacterium abscessus and M. chelonae belong to the rapid-growing nontuberculous mycobacteria (NTM) group, which are defined by their ability to form visible colonies on agar within 7 days of subculture. Cutaneous infections by this complex show a heterogeneous clinical presentation with varied histopathologic findings. However, the presence of vacuoles in many specimens has been reported as a specific histologic finding. Herein, we correlate the histopathology of patients with tissue-culture positive M. abscessus/M. chelonae complex in order to identify features that may prompt a rapid categorization of the infectious etiology. The cohort includes 33 skin punch biopsy specimens from 28 patients who had associated positive tissue cultures. The most frequent clinical presentation was a single or multiple nodule. Twenty-seven specimens (81.81%) were found to have vacuoles. The observation of certain histologic features (ie, polymorphonuclear microabscesses and epithelioid granuloma formation) should raise the possibility of infection by NTM. In addition to these findings, we believe the presence of vacuoles in the dermal and subcutaneous inflammation should raise suspicion for NTM.

Diagnosis of mycobacterial skin infections

The diagnosis of cutaneous mycobacterial infections may be challenging. Owing to the broad spectrum of their clinical presentations, mycobacterioses have to be considered as differential diagnoses to many inflammatory dermatoses. Diagnostic measures comprise histology including special staining, cultures and molecular microbiological examinations as well as the detection of cellular immune reactions of the patient by means of interferon-γ release assays and skin testing. Clinicians should know the appropriate use and combination of procedures to diagnose mycobacterioses quickly and correctly and to avoid costs and delays caused by unnecessary examinations. This mini review summarizes advantages, limitations, and pitfalls of diagnostic methods for mycobacterial skin infections.

Cutaneous Tuberculosis: Clinicopathologic Arrays and Diagnostic Challenges

The clinicopathological manifestations of cutaneous tuberculosis are diverse. The precise diagnosis is often overlooked, due to clinical presentations as those of cutaneous diseases with different etiology and the relative paucity of the pathogens in the lesions. Meanwhile, almost all of the diagnostic methods confer lower sensitivity and specificities which augments further diagnostic challenges. This article revises the current scenario of the disease's physiopathology and underscores clinicopathological challenges, due to multifaceted presentations of cutaneous tuberculosis, in the diagnosis.