Rapid detection and differentiation of mycobacterial species using a multiplex PCR system

Cas12a/Guide RNA-Based Platform for Rapid and Accurate Identification of Major Mycobacterium Species

Mycobacterium tuberculosis infection and nontuberculous mycobacteria (NTM) infections exhibit similar clinical symptoms; however, the therapies for these two types of infections are different. Therefore, the rapid and accurate identification of M. tuberculosis and NTM species is very important for the control of tuberculosis and NTM infections. In the present study, a Cas12a/guide RNA (gRNA)-based platform was developed to identify M. tuberculosis and most NTM species. By designing species-specific gRNA probes targeting the rpoB sequence, a Cas12a/gRNA-based platform successfully identified M. tuberculosis and six major NTM species (Mycobacterium abscessus, Mycobacterium intracellulare, Mycobacterium avium, Mycobacterium kansasii, Mycobacterium gordonae, and Mycobacterium fortuitum) without cross-reactivity. In a blind assessment, a total of 72 out of 73 clinical Mycobacterium isolates were correctly identified, which is consistent with previous rpoB sequencing results. These results suggest that the Cas12a/gRNA-based platform is a promising tool for the rapid, accurate, and cost-effective identification of both M. tuberculosis and NTM species.

Molecular epidemiology of mycobacteria among herds in Marajó Island, Brazil, reveals strains genetically related and potential zoonotic risk of clinical relevance

Mycobacterium bovis is the main causative agent of bovine tuberculosis (bTB) being among the animal-adapted Mycobacterium tuberculosis complex. Herds can also be infected with non-tuberculous mycobacteria (NTM) causing a negative effect on the economy and on animal and human health through zoonotic infections. Molecular tools are required for mycobacteria identification; thus, it is laborious to determine the epidemiological information of mycobacteria among herds. We aimed to describe the mycobacterial pathogens associated with cases of suspected bTB lesions in cattle/buffaloes slaughtered for consumption and to investigate bTB transmission. We evaluated 74 lesion samples from 48 animals (27 bovine/21 buffaloes) from 16 mapped farms. Positives samples from nested-PCR were cultured in Lowenstein-Jensen (LJ), 2% pyruvate (LJ + P), and 2% glycerol (LJ + G) media, followed by Ziehl-Neelsen (ZN) staining technique and partial gene sequencing (hsp65, rpoB, and 16S-rRNA). Spoligotyping and 24-MIRU-VNTR were performed. The LJ + P increased the chance of obtaining bacilli. The respiratory tract and the oral cavity were the most important infection route. In addition, the calcified part of the lesions suggested chronic bTB. Spoligotypes of M. bovis (SIT986/SB0885) differed from others found in South America, and the MIRU-VNTR 24 loci suggested that bTB was associated to highly related strains. The NTM species found are of clinical importance in humans.

[Non-tuberculous mycobacterial cervical adenitis in children: 2 cases]

BACKGROUND

Cervical lymphadenitis is the most common manifestation of infection with nontuberculous mycobacteria (NTM) in immunocompetent children. Nevertheless, it is poorly known by dermatologists. Its incidence, which is currently increasing since the cessation of BCG vaccination in 2007, raises several issues regarding its pathophysiology, diagnosis and management.

PATIENTS AND METHODS

We report two cases of NTM adenitis: one in a 2-year-old girl vaccinated with BCG and one in an unvaccinated 22-month-old boy, in whom a misleading presentation led to delayed diagnosis. The condition progressed to fistula formation and the diagnosis was finally made on systematic cultures of lymph node samples. The time to diagnosis was 2 and 4months, respectively. The girl was treated with erythromycin for 3 weeks and with clarithromycin for 3 weeks; the boy received clarithromycin for 7 weeks and underwent complete surgical excision.

DISCUSSION

NTM adenitis preferentially affects girls under 4 years and occurs more frequently in winter and spring. First, the other differential diagnoses, including tuberculosis, must be ruled out by chest radiography. The diagnosis is oriented by the clinical picture, a positive TST and resistance to conventional antibiotics. However, it is only certified by systematic culture or PCR of lymph node biopsies, with screening for atypical mycobacteria being specified. The decrease in child protection by BCG vaccination coincides with the current increase in NTM infections, of which the most frequent is Mycobacterium avium complex (MAC) for cervical adenitis. The reference treatment is surgery. However, alternative treatments (incomplete excision, antibiotics, watchful waiting, etc.) should be considered where surgery fails or there is excessive risk of injury to a branch of the facial nerve.

CONCLUSION

Atypical mycobacterial adenitis in immunocompetent children has become an increasingly common infection since the abandonment of BCG vaccination. Improved knowledge of this disease would result in complete surgical excision at an early stage with a lower rate of aesthetic sequelae.

Surgical treatment for chronic cervical lymphadenitis in children. Experience from a tertiary care paediatric centre on non-tuberculous mycobacterial infections

OBJECTIVES

Non-tuberculous mycobacteria are the most frequent cause of chronic lymphadenitis in children. We reviewed treatment and outcomes of paediatric patients with chronic cervical lymphadenitis, to better understand their differential diagnosis, surgical indication, complication and recover.

METHODS

A retrospective study was carried out on children who underwent surgery from 2013 to 2016 at Meyer Children's University Hospital, Florence, Italy. Time to cure, type of surgery, and complications rate were determined and etiologic agents were identified and correlated to their clinical presentation.

RESULTS

275 children were evaluated. Nearly 98% of the patients were cured regardless of which therapeutic option was used and surgery was necessary in 38.2% of children. Complete excisional biopsy ensured recover in 97.7% of patients compared with the non-excisional surgical group 88.2% (p = 0.06). Re-interventions were needed in the 2.3% of complete excision group and in two cases of the incision and drainage group; all of them developed fistula and were caused by Mycobacterium avium complex. Excision followed by adjunctive antibiotic therapy was favoured in the majority of the patients (80.1%, n = 71).

CONCLUSION

In cases of non-tuberculous mycobacteria lymphadenitis, surgery is the treatment of choice and it is closely related to a favourable prognosis.

Diagnosis of mycobacterial infections based on acid-fast bacilli test and bacterial growth time and implications on treatment and disease outcome

BACKGROUND

The establishment of therapeutic regimens for mycobacteriosis depends on the accurate identification of Mycobacterium species, and misdiagnosis can result in inappropriate treatment and increased mortality of patients. Differential diagnosis among Mycobacterium species has been made by conventional phenotypic and biochemical tests after a long culture period. Specialized molecular diagnostics of mycobacteria allows rapid detection and species identification; however, such tests are not available in public health programs. Our aim was to demonstrate the clinical implications of erroneous diagnosis by performing molecular genotyping of mycobacterial infections in patients that were diagnosed based on symptoms, culture and bacilloscopy.

METHODS

Culture samples of mycobacterial infections from 55 patients clinically diagnosed as tuberculosis in 2013 and 2014, based on conventional methods, were identified by PCR -RFLP and results are discussed.

RESULTS

We have confirmed 35 (63.6%) positive samples as M. tuberculosis, but 18 (32.7%) were identified as non-tuberculous mycobacteria (M. avium type 1, M. avium type 2, M. kansasii type 1 type 1, M. mucogenicum, M. chelonae, M. terrae type 3, and 1 unknown RFLP pattern) and two were negative. Regarding clinical diagnosis, 61.8% (34/55) was classified as pulmonary tuberculosis. It is important to emphasize that 36.4% (20/55) of samples were misdiagnosed by conventional methods, and 11 (61.1%) of the HIV positive patients (18/55) were NTM-coinfected.

CONCLUSION

The identification of species in mycobacterial infections is essential for correct diagnosis and choice of treatment regimen, and misdiagnosis by conventional tools can lead to chronic disease, increased resistance and death.