A study of the diagnosis, treatment and epidemiology of Mycobacterium abscessus in patients with cystic fibrosis

Members of the Mycobacterium abscessus complex (MABSC) are a highly antibiotic-resistant complex of organisms within the genus Mycobacterium, increasingly acknowledged as a significant cause of lung infection in patients with cystic fibrosis (CF)and associated with poor clinical outcomes. Current methods of isolation of MABSC are hindered by the fact that they grow at a slower rate in culture than other microorganisms with many patient samples having to be discarded due to the overgrowth of more rapidly growing species. Decontamination of samples has shown to have an adverse effect upon the viability of MABSC, therefore improvements in the isolation of MABSC are urgently required in order to offer the possibility of a more rapid and accurate diagnosis. A novel medium (RGM) was developed for the isolation of MABSC. Commercially available pre-poured media were compared with RGM and challenged with isolates of rapidly growing mycobacteria and other species. In addition, in a multi-centre study sputum samples collected from patients with CF were inoculated onto RGM medium, BCSA and standard automated liquid culture method and assessed for growth. RGM demonstrated superior sensitivity over currently used methods without any requirement for decontamination and could easily be incorporated into any laboratory alongside routine culture for other CF pathogens. Chromogenic and fluorogenic substrates were investigated for the possibility of differentiating between subspecies within the MABSC complex. However, the results established that these would not provide any additional benefit to RGM. Possible environmental sources were explored in order to establish how patients with CF were acquiring MABSC. Although person-to-person transmission has been suggested, there are very few reports to substantiate this at present and many questions remain unanswered. In this study, MABSC was not isolated from any of the environments screened. Finally, a selection of antimicrobials were investigated against MABSC with the purpose of ascertaining susceptibility and whether any may be used for a more successful treatment outcome. There were no clinically applicable results therefore further work is required in this area. To conclude, RGM is a novel culture medium, which can be embedded alongside routine culture for other CF pathogens without any requirement for decontamination. This means that all respiratory samples submitted from patients with CF can be conveniently cultured for NTM, considerably improving the service offered to clinicians and patients. Furthermore, it is likely that formal AFB culture methods could be replaced by use of such a medium, potentially enabling substantial savings in terms of materials and labour time

A study of the diagnosis, treatment and epidemiology of Mycobacterium abscessus in patients with cystic fibrosis

Members of the Mycobacterium abscessus complex (MABSC) are a highly antibiotic-resistant complex of organisms within the genus Mycobacterium, increasingly acknowledged as a significant cause of lung infection in patients with cystic fibrosis (CF) and associated with poor clinical outcomes. Current methods of isolation of MABSC are hindered by the fact that they grow at a slower rate in culture than other microorganisms with many patient samples having to be discarded due to the overgrowth of more rapidly growing species. Decontamination of samples has shown to have an adverse effect upon the viability of MABSC, therefore improvements in the isolation of MABSC are urgently required in order to offer the possibility of a more rapid and accurate diagnosis. A novel medium (RGM) was developed for the isolation of MABSC. Commercially available pre-poured media were compared with RGM and challenged with isolates of rapidly growing mycobacteria and other species. In addition, in a multi-centre study sputum samples collected from patients with CF were inoculated onto RGM medium, BCSA and standard automated liquid culture method and assessed for growth. RGM demonstrated superior sensitivity over currently used methods without any requirement for decontamination and could easily be incorporated into any laboratory alongside routine culture for other CF pathogens. Chromogenic and fluorogenic substrates were investigated for the possibility of differentiating between subspecies within the MABSC complex. However, the results established that these would not provide any additional benefit to RGM. Possible environmental sources were explored in order to establish how patients with CF were acquiring MABSC. Although person-to-person transmission has been suggested, there are very few reports to substantiate this at present and many questions remain unanswered. In this study, MABSC was not isolated from any of the environments screened. Finally, a selection of antimicrobials were investigated against MABSC with the purpose of ascertaining susceptibility and whether any may be used for a more successful treatment outcome. There were no clinically applicable results therefore further work is required in this area. To conclude, RGM is a novel culture medium, which can be embedded alongside routine culture for other CF pathogens without any requirement for decontamination. This means that all respiratory samples submitted from patients with CF can be conveniently cultured for NTM, considerably improving the service offered to clinicians and patients. Furthermore, it is likely that formal AFB culture methods could be replaced by use of such a medium, potentially enabling substantial savings in terms of materials and labour time

Evaluation of RGM Medium for Isolation of Nontuberculous Mycobacteria from Respiratory Samples from Patients with Cystic Fibrosis in the United States

ABSTRACT A novel selective agar (RGM medium) has been advocated for the isolation of rapidly growing mycobacteria from the sputa of cystic fibrosis (CF) patients. The aim of this study was to compare RGM medium to Burkholderia cepacia selective agar (BCSA) and a standard acid-fast bacillus (AFB) culture method for the isolation of nontuberculous mycobacteria (NTM) from patients with CF. The applicability of matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) for the identification of NTM isolated on RGM medium was also assessed. Respiratory samples ( n = 869) were collected from 487 CF patients and inoculated directly onto RGM medium and BCSA. Cultures were incubated at 30°C and examined for up to 28 days. A subset of 212 samples (from 172 patients) was also cultured by using a mycobacterial growth indicator tube (MGIT) and on Lowenstein-Jensen medium following dual decontamination. By using a combination of all methods, 98 mycobacteria were isolated from 869 samples (11.3%). The sensitivity of RGM medium (96.9%) was significantly higher than that of BCSA (35.7%) for the isolation of mycobacteria ( P < 0.0001). The sensitivity of RGM medium was also superior to that of standard AFB culture for the isolation of mycobacteria (92.2% versus 47.1%; P < 0.0001). MALDI-TOF MS was effective for the identification of mycobacteria in RGM medium. RGM medium offers a simple and highly effective tool for the isolation of NTM from patients with CF. Extended incubation of RGM medium for 28 days facilitates the isolation of slow-growing species, including members of the Mycobacterium avium complex (MAVC)

Evaluation of Various Culture Media for Detection of Rapidly-Growing Mycobacteria from Patients with Cystic Fibrosis.

Isolation of nontuberculous mycobacteria (NTM) from the sputum of patients with cystic fibrosis (CF) is challenging due to overgrowth by rapidly growing species that colonize the lungs of patients with CF. Extended incubation on Burkholderia cepacia selective agar (BCSA) has been recommended as an expedient culture method for the isolation of rapidly growing NTM in this setting. The aim of this study was to assess five selective media designed for the isolation of Burkholderia cepacia complex, along with two media designed for the isolation of mycobacteria (rapidly growing mycobacteria [RGM] medium and Middlebrook 7H11 agar), for their abilities to isolate NTM. All seven media were challenged with 147 isolates of rapidly growing mycobacteria and 185 isolates belonging to other species. RGM medium was then compared with the most selective brand of BCSA for the isolation of NTM from 224 sputum samples from patients with CF. Different agars designed for the isolation of B. cepacia complex varied considerably in their inhibition of other bacteria and fungi. RGM medium supported the growth of all isolates of mycobacteria and was more selective than any other medium. NTM were recovered from 17 of 224 sputum samples using RGM medium, compared with only 7 samples using the most selective brand of BCSA (P = 0.023). RGM medium offers a superior option, compared to other selective agars, for the isolation of rapidly growing mycobacteria from the sputum of patients with CF. Furthermore, the convenience of using RGM medium enables routine screening for rapidly growing NTM in all submitted sputum samples from patients with CF

Comparison of Mycobacterial Growth Indicator Tube with Culture on RGM Selective Agar for Detection of Mycobacteria in Sputum Samples from Patients with Cystic Fibrosis

Nontuberculous mycobacteria (NTM) are an important cause of pulmonary disease in patients with cystic fibrosis (CF). A new culture medium (RGM medium) for the isolation of rapidly growing mycobacteria from the sputum of cystic fibrosis patients has recently been reported. The aim of this study was to compare culture of sputum samples on RGM medium with culture using a standard automated liquid culture method. Sputum samples were obtained from 187 distinct patients with CF attending King's College Hospital, London, United Kingdom. Each sample was decontaminated with 3% oxalic acid and inoculated into a mycobacterial growth indicator tube (MGIT) that was monitored for 42 days using the Bactec MGIT 960 instrument. Each sample was also cultured, without decontamination, onto RGM medium, which was incubated for 10 days at 30°C. Mycobacteria were isolated from 28 patients (prevalence, 15%). Mycobacteria were detected in 24 samples (86%) using the MGIT and in 23 samples (82%) using RGM medium (P = 1.00). In this setting, RGM medium showed sensitivity equivalent to that of the MGIT for isolation of NTM from the sputum of patients with CF. RGM medium offers a simple, convenient tool that can be embedded into routine culture methods, allowing the culture of all sputum samples that are submitted from patients with CF

61 Comparison of two chromogenic media for isolation of Staphylococcus aureus from respiratory samples from patients with cystic fibrosis [POSTER]

To evaluate two chromogenic culture media, chromID S. aureus (“chromID”) and chromID S. aureus Elite (“chromID Elite”) for isolation of Staphylococcus aureus from respiratory samples from patients with cystic fibrosis (CF)

Comparison of Mycobacterial Growth Indicator Tube with Culture on RGM Selective Agar for Detection of Mycobacteria in Sputum Samples from Patients with Cystic Fibrosis

Nontuberculous mycobacteria (NTM) are an important cause of pulmonary disease in patients with cystic fibrosis (CF). A new culture medium (RGM medium) for the isolation of rapidly growing mycobacteria from the sputum of cystic fibrosis patients has recently been reported. The aim of this study was to compare culture of sputum samples on RGM medium with culture using a standard automated liquid culture method. Sputum samples were obtained from 187 distinct patients with CF attending King's College Hospital, London, United Kingdom. Each sample was decontaminated with 3% oxalic acid and inoculated into a mycobacterial growth indicator tube (MGIT) that was monitored for 42 days using the Bactec MGIT 960 instrument. Each sample was also cultured, without decontamination, onto RGM medium, which was incubated for 10 days at 30°C. Mycobacteria were isolated from 28 patients (prevalence, 15%). Mycobacteria were detected in 24 samples (86%) using the MGIT and in 23 samples (82%) using RGM medium (P = 1.00). In this setting, RGM medium showed sensitivity equivalent to that of the MGIT for isolation of NTM from the sputum of patients with CF. RGM medium offers a simple, convenient tool that can be embedded into routine culture methods, allowing the culture of all sputum samples that are submitted from patients with CF