[Molecular pathology of tuberculosis : Status, methodology, and limits]

In the diagnosis of mycobacterioses, microbiological examination with culture and antibiogram, possibly in combination with molecular biological testing of the fresh material, still represents the gold standard. However, these methods are not available for formalin-fixed paraffin-embedded (FFPE) material or other fixed samples. For this reason, the first step in pathology is to attempt microscopic pathogen detection (ZN/Fite/rhodamine-auramine). Subsequently, molecular pathological examination for the detection of mycobacterial gene sequences should also be considered mandatory today. Although this has clear limits due to the material, it is nevertheless well suited, if carried out correctly, to detect a mycobacterial infection or make it unlikely. A negative result may favor an alternative diagnosis but does not completely rule out mycobacteriosis.For the therapy of tuberculosis or nontuberculous mycobacterial (NTM) disease, the reliable detection of the species and the determination of resistance is of utmost importance. With regard to therapy, the clinician cannot afford to make a false diagnosis. In case of doubt, a rebiopsy for sampling native material, particularly for microbiological testing, should be discussed.

Cost of multidrug resistant tuberculosis in Germany-An update

BACKGROUND

In 2019, new therapeutic recommendations for multidrug-resistant (MDR-) and extensively drug-resistant (XDR) tuberculosis (TB) were published by the WHO, advocating the use of oral drugs and stepwise composition of antibiotic regimens. To date, the economic consequences of those recommendations in low incidence settings have not been evaluated.

OBJECTIVE

To assess the costs of applying the new recommendations against a set of 86 MDR-TB/XDR-TB strains, each with individual phenotypic drug resistance patterns, identified in 2018/2019 by the German National Reference Center for Mycobacteria.

METHODS

Hospitalization costs as covered by German statutory health insurance and the loss of productivity due to illness were calculated using the most recent 2018 statistical data. Costs due to combining five agents in the intensive phase and costs of outpatient monitoring were determined by Monte-Carlo simulation covering all treatment options over an 18-month period. Drug costs were compared to those arising under the approach recommended by the WHO in 2016.

RESULTS

Hospitalization costs per MDR-TB patient were €30,152 and the mean costs of antimicrobials over a period of 18 months were €66,854 (range €20,671 to €187,444). Total treatment costs, including outpatient monitoring, were €73,551.56 per patient (range €30,114 to €145.878). In addition, we determined an average cost of €11,410.20 due to productivity loss over a period of 6 months sick leave. Despite a shortened minimum recommended treatment duration (18 versus 20 months), the estimated costs were 24.5% higher based on the 2019 recommendations as compared to the 2016 guideline version.

CONCLUSION

Higher costs for treating MDR-TB/XDR-TB in Germany are to be expected under the new WHO regimens. However, it must be determined whether treatment duration and costs associated with sick leave may be further reduced in the future through shorter hospital stays and earlier culture conversion.

Die neuen WHO-Empfehlungen für schnelle Diagnostik und Therapie resistenter Tuberkulose in Deutschland, Österreich und der Schweiz

Die erfreulicherweise zunehmende Evidenz hat in den letzten Jahren mehrfache Änderungen der internationalen Empfehlungen für die Diagnostik und Therapie der resistenten Tuberkulose notwendig gemacht. In diesem Jahr hat die WHO umfassende Empfehlungen veröffentlicht, die die Entwicklungen der letzten Jahre berücksichtigen. Die aktuelle deutsche Tuberkuloseleitlinie erschien im Jahr 2017 und weicht in einigen Bereichen von diesen Empfehlungen ab. Hier werden die Neuerungen der WHO-Empfehlungen von 2020 für schnelle Diagnostik und die Therapie resistenter Tuberkulose zusammengefasst und relevante Abweichungen für Deutschland, Österreich und die Schweiz kommentiert. Eine Neubewertung der Literatur findet derzeit im Rahmen der Aktualisierung der deutschsprachigen AWMF-2k-Leitlinie statt.

The landscape of diagnostic mycobacteriology in Germany-challenges of decentralised care

OBJECTIVE: To perform a nationwide inventory of diagnostic mycobacteriology services in Germany.METHOD: A survey was conducted among participants of the national mycobacteriology external quality assurance scheme asking for smear microscopy techniques, molecular assays, culture systems and drug susceptibility testing (DST) capacities for Mycobacterium tuberculosis complex (MTBC) and non-tuberculous mycobacteria (NTM), and numbers of processed/culture-positive samples, and DSTs performed in 2016.RESULTS: We found that 170/238 laboratories (71.4%) provided data. Numbers of samples processed for culture varied between 35 and 40 000 (median 1856, interquartile range [IQR] 761-3500). Specimen numbers culture-positive for MTBC or NTM ranged from 0 to 1895 (median 46, IQR 17-116), and from 0 to 833 (median 30, IQR 13-71), respectively. Numbers of performed first-line susceptibility tests varied between 3 and 1400 (median 36, IQR 28-78). Eight laboratories performed DST for NTM. Also, 26.9% of all laboratories did not offer rapid genotypic DST (gDST) from primary samples.CONCLUSION: The landscape of diagnostic mycobacteriology in Germany is highly heterogenic with considerable variations in sample numbers and testing methodologies. Shortcomings exist with respect to fluorochrome staining of primary samples, rapid gDST of MTBC, and DST of NTM. National guidelines need to be adapted accordingly.

International Society of Cardiovascular Infectious Diseases Guidelines for the Diagnosis, Treatment and Prevention of Disseminated Mycobacterium chimaera Infection Following Cardiac Surgery with Cardiopulmonary Bypass

Mycobacterial infection-related morbidity and mortality in patients following cardiopulmonary bypass surgery is high and there is a growing need for a consensus-based expert opinion to provide international guidance for diagnosing, preventing and treating in these patients. In this document the International Society for Cardiovascular Infectious Diseases (ISCVID) covers aspects of prevention (field of hospital epidemiology), clinical management (infectious disease specialists, cardiac surgeons, ophthalmologists, others), laboratory diagnostics (microbiologists, molecular diagnostics), device management (perfusionists, cardiac surgeons) and public health aspects.

Differential drug susceptibility patterns of Mycobacterium chimaera and other members of the Mycobacterium avium-intracellulare complex

OBJECTIVES

To determine MIC distributions for Mycobacterium chimaera, Mycobacterium intracellulare, Mycobacterium colombiense and Mycobacterium avium, and to derive tentative epidemiological cut-off (ECOFF) values.

METHODS

A total of 683 bacterial isolates (M. chimaera, n = 203; M. intracellulare, n = 77; M. colombiense, n = 68; M. avium, n = 335) from 627 patients were tested by broth microdilution according to CLSI protocol M24-A2 on Sensititre RAPMYCOI plates. MICs were interpreted based on CLSI breakpoints for clarithromycin, and tentative breakpoints for amikacin, moxifloxacin and linezolid. Tentative ECOFFs were determined by visual approximation and the ECOFFinder algorithm.

RESULTS

Modal MIC, MIC₅₀ and MIC₉₀ values were within ± one dilution step from the respective aggregated data set for 47/48 (97.9%), 48/48 (100%) and 48/48 (100%) species-drug combinations. Clarithromycin wild-type populations were mostly classified as susceptible (MIC₉₀ 4-8 mg/L; S ≤8 mg/L). Rifabutin MICs were lower than those of rifampicin. Tentative moxifloxacin, linezolid and amikacin breakpoints split wild-type populations. No ECOFFs could be set for rifampicin, ethambutol, ciprofloxacin, isoniazid, trimethoprim/sulfamethoxazole and doxycycline because of truncation of MIC distributions. Agreement between the visually determined and the modelled 97.5% ECOFFs was 90.9%. All 99.0% ECOFFs were one titre step higher than by visual approximation.

CONCLUSIONS

Drug susceptibility patterns of M. chimaera are comparable to those of closely related species. Except for clarithromycin, breakpoints for Mycobacterium avium-intracellulare complex should be re-evaluated. Statistical determination of the 99.0% ECOFF may be superior to visual approximation.

[Advances in diagnostic microbiology : Opportunities and limitations]

In the light of ever increasing problems related to the emergence of multidrug-resistant bacteria, rapid microbiological diagnostics are of growing importance. Timely pathogen detection and availability of susceptibility data are essential for optimal treatment, but are even more crucial for de-escalation of broad spectrum empiric therapies. Medical microbiology is, thus, an integral part of antimicrobial stewardship programs. Traditional microbiological techniques for species identification and susceptibility testing rely on bacterial growth and are, thus, characterized by inherent slowness. Time-to-report is usually 48 h or longer, and typically delays optimization of therapeutic regimens. Constant improvement of available techniques (e. g., molecular methods) and introduction of novel methods (e. g., matrix-assisted laser desorption ionization time-of-flight [MALDI-ToF] mass spectrometry) have fundamentally changed diagnostic procedures. As a consequence, sensitivity and specificity as well as time-to-report have been dramatically improved. In this manuscript, key methodological advances in medical microbiology are discussed, emphasizing consequences for daily management of infectious disease patients.