Optimized molecular resolution of cross-contamination alerts in clinical mycobacteriology laboratories

Role of Molecular Epidemiology on Tuberculosis Control in the Middle East Countries: a Systematic Review and Meta-Analysis

BACKGROUND

Tuberculosis (TB) is a public health problem in developing countries and yet the numbers of people with the disease are abundant. Early detection of transmission sources and effective treatment of the cases is essential to control the disease which will be possible by application of molecular epidemiology approaches. Studies conducted based on Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) method in Muslim Middle East countries were evaluated to determine their role in TB control.

MATERIALS AND METHODS

All studies from January 2005 to April 2016 were systematically reviewed in four electronic databases and finally 16 articles were found eligible to be included in this study. The mean clustering rate was determined as 44% and the recent transmission rate was 12.3 to 78.8% with average of 33%.

RESULTS

The results showed that both reactivation and recent transmission were important in developing new cases of TB in Middle East countries; but, reactivation plays a more critical role.

CONCLUSION

Regarding to ongoing war and immigration in the region along with the increasing of drug-resistant TB, in the case of improper supervision in the future, the disease, especially drug- resistant TB, will be problematic.

False-positive tuberculous meningitis due to laboratory contamination: importance of a holistic clinical evaluation

Incidence of tuberculosis in Nebraska is 1.9/100,000 people. Tuberculous meningitis is rare and comprises 1% of extrapulmonary tuberculosis. An elderly Caucasian man presented with fever, headache, altered mentation and a history of tick bite. Cerebrospinal fluid (CSF) analysis showed negative cultures and the patient was treated empirically for tickborne illness. Forty-five days later, CSF nucleic acid amplification test (NAAT) was positive for tuberculosis. On readmission, repeat neurological examination and CSF analysis were benign and the patient was not offered antituberculous treatment. Genotype investigation of the culture and NAAT specimen by the Center for Disease Control confirmed laboratory contamination. The literature reports an incidence of 2-4% for false-positive tuberculosis cultures. Contaminated devices, clerical errors and laboratory errors have been implicated. Laboratory contamination results in smear-negative culture-positive cases. Epidemiological investigation with genotype testing is confirmatory. Detailed clinical assessment with good clinical and laboratory communication and frequent laboratory surveillance is advocated to mitigate these cases.

The re-emergence of tuberculosis: what have we learnt from molecular epidemiology?

Tuberculosis (TB) has re-emerged over the past two decades: in industrialized countries in association with immigration, and in Africa owing to the human immunodeficiency virus epidemic. Drug-resistant TB is a major threat worldwide. The variable and uncertain impact of TB control necessitates not only better tools (diagnostics, drugs, and vaccines), but also better insights into the natural history and epidemiology of TB. Molecular epidemiological studies over the last two decades have contributed to such insights by answering long-standing questions, such as the proportion of cases attributable to recent transmission, risk factors for recent transmission, the occurrence of multiple Mycobacterium tuberculosis infection, and the proportion of recurrent TB cases attributable to re-infection. M. tuberculosis lineages have been identified and shown to be associated with geographical origin. The Beijing genotype is strongly associated with multidrug resistance, and may have escaped from bacille Calmette-Guérin-induced immunity. DNA fingerprinting has quantified the importance of institutional transmission and laboratory cross-contamination, and has helped to focus contact investigations. Questions to be answered in the near future with whole genome sequencing include identification of chains of transmission within clusters of patients, more precise quantification of mixed infection, and transmission probabilities and rates of progression from infection to disease of various M. tuberculosis lineages, as well as possible variations in vaccine efficacy by lineage. Perhaps most importantly, dynamics in the population structure of M. tuberculosis in response to control measures in high-prevalence areas should be better understood.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification of mycobacteria in routine clinical practice

Background

Non-tuberculous mycobacteria recovered from respiratory tract specimens are emerging confounder organisms for the laboratory diagnosis of tuberculosis worldwide. There is an urgent need for new techniques to rapidly identify mycobacteria isolated in clinical practice. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) has previously been proven to effectively identify mycobacteria grown in high-concentration inocula from collections. However, a thorough evaluation of its use in routine laboratory practice has not been performed.

Methodology

We set up an original protocol for the MALDI-TOF MS identification of heat-inactivated mycobacteria after dissociation in Tween-20, mechanical breaking of the cell wall and protein extraction with formic acid and acetonitrile. By applying this protocol to as few as 10⁵ colony-forming units of reference isolates of Mycobacterium tuberculosis, Mycobacterium avium, and 20 other Mycobacterium species, we obtained species-specific mass spectra for the creation of a local database. Using this database, our protocol enabled the identification by MALDI-TOF MS of 87 M. tuberculosis, 25 M. avium and 12 non-tuberculosis clinical isolates with identification scores ≥2 within 2.5 hours.

Conclusions

Our data indicate that MALDI-TOF MS can be used as a first-line method for the routine identification of heat-inactivated mycobacteria. MALDI-TOF MS is an attractive method for implementation in clinical microbiology laboratories in both developed and developing countries.

Rapid detection of laboratory cross-contamination with Mycobacterium tuberculosis using multispacer sequence typing

BACKGROUND

The ability to culture Mycobacterium tuberculosis from clinical specimens serves as the gold standard for the diagnosis of tuberculosis. However, a number of false-positive diagnoses may be due to cross-contamination of such specimens. We herein investigate such episode of cross-contamination by using a technique known as multispacer sequence typing (MST). This technique was applied to six M. tuberculosis isolates prepared within the same laboratory over a two-week period of time.

RESULTS

MST analysis indicated a unique and common sequence profile between a strain isolated from a patient with proven pulmonary tuberculosis and a strain isolated from a patient diagnosed with lung carcinoma. Using this approach, we were able to provide a clear demonstration of laboratory cross-contamination within just four working days. Further epidemiological investigations revealed that the two isolates were processed for culture on the same day.

CONCLUSION

The application of MST has been demonstrated to serve as a rapid and efficient method to investigate cases of possible cross-contamination with M. tuberculosis.