Identification of the Optimal Cultivation Period Required to Isolate Representatives of Mycobacterium abscessus Complex Isolated from Patients with Cystic Fibrosis.

BACKGROUND: In patients with cystic fibrosis (CF), representatives of the fast-growing Mycobacterium abscessus complex (MABSc) are often distinguished, but the culture of the material taken from such patients increases the growth time. We analyzed the terms of cultivation of MABSc representatives on dense nutrient media and also evaluated the productivity of a modified nutrient medium based on agar for the isolation of Burkholderia cepacia complex (BCC). METHODS: Sixty-four strains of MABSc isolated from patients with CF and suspected tuberculosis were analyzed. The material from the patients was cultured on a universal chromogenic medium, 5% blood agar, yolk-salt agar, selective medium for isolation of BCC, and Löwenstein-Jensen medium. The cultures were incubated for 5 days (37°C, aerobic conditions), after for 23 days (28°C, aerobic conditions). The productivity of the developed nutrient medium was evaluated by the number of cells that gave visible growth after culturing 0.1 mL of a bacterial suspension of 103 CFU/mL. RESULTS: 76.8% of the strains grew in a 2-week period, and 23.2% of the strains were obtained at a later date from 18 to 28 days (average: 21.23 days). The modified medium with a concentration of 240 mg of iron (III) polymaltose hydroxide proved to be the most optimal for the isolation of MABSc. CONCLUSION: When using a chromogenic medium for culture material from patients with CF, it is necessary to extend incubation up to 28 days to increase the probability of MABSc isolation. The modified BCC medium showed a good selectivity result but required further investigation.

Comparison of protein profiles obtained by matrix-assisted laser desorption/ionization-Time-of-flight mass spectrometry in representatives of the family Mycobacteriaceae grown on various nutrient media.

Background: The nutrient medium effects on the quality of the matrix-assisted laser desorption/ionization-time-of-flight (MALDI-ToF) mass spectra. The standard library includes spectra of microorganisms of the family Mycobacteriaceae grown on the Lowenstein-Jensen and Middlebrook Media. There are new methods for culturing microorganisms from this group, including inoculation on chromogenic media. Methods: The study included 240 strains of NTM isolated from patients during tuberculosis examination. The inoculation of the biological material was carried out on solid culture media of Lowenstein-Jensen and universal chromogenic media. Identification of bacteria from both types of media was performed by MALDI-ToF mass spectrometry (Bruker Daltonik GmbH, Germany). Analysis of protein spectra was performed. Results: For all strains, the spectra revealed both coinciding peaks (regardless of the cultivation medium) and significant differences, including the complete absence of some peaks depending on the medium. The results of a greater divergence of peaks in mass and intensity were obtained for slow-growing species than for fast-growing species. For all analyzed cultures, the number of peaks in the mass spectra was significantly higher when cultivating on a universal chromogenic medium than on a Lowenstein-Jensen medium. Conclusions: The use for NTM cultivation of a universal chromogenic medium makes it possible to obtain acceptable identification results by MALDI-ToF mass spectrometry using a standard library.

Species diversity of microorganisms previously identified as nontuberculous mycobacteria by DNA hybridization.

Background: Over the past 10 years, the clinical importance of opportunistic bacteria of the order Actinomycetales has increased significantly. While many problems for the Mycobacterium tuberculosis complex have been solved, for nontuberculous mycobacteria, some questions remain open. These pathogens have a number of structural features that allow them to persist in the external environment for a long time. Methods: The main inclusion criteria were cultural characteristics in assessing the growth of microorganisms on solid egg media. If nontuberculous mycobacteria (NTM) growth was detected, identification signs were carried out using the DNA hybridization method. Subsequently, these cultures were identified using the matrix-assisted laser desorption/ionization-time-of-flight (MALDI-ToF) mass spectrometry method. In case of obtaining unacceptable results of identification from primary inoculations, re-identification to obtain pure cultures was carried out after transferring the material from primary media to agar media: 5% blood agar and universal chromogenic medium. When re-identifying isolated cultures using MALDI-ToF mass spectrometry, all isolated cultures were analyzed, regardless of whether they belonged to the NTM group or not. Results: DNA hybridization, which accounted for 59.5% of the total number of cultures included in the study, performed species identification of 188 strains. Using MALDI-ToF mass spectrometry, 345 strains were identified. Conclusion: The use of methods based on DNA hybridization makes it possible to identify quite accurately some of the most common NTM species. MALDI-ToF mass spectrometry is an important technique to allow species identification of most Actinomycetales. However, algorithms to standardize methods for their isolation from clinical material are needed.