Epidemiology of non-pigmented rapidly growing Mycobacteria in a university hospital

Abstract number: 1134_04_260

García-Cía J.I., Ortiz A., Esteban J., Fernández-Roblas R.

Objectives:  

To analyze the epidemiology of rapidly growing Mycobacteria by using RAPD during a 12 year period.

Methods:  

Rapidly growing Mycobacteria (RGM) obtained during the period 1990–2002 were maintained frozen since their isolation until the experiments were performed. Bacteria were reidentified and a study using RAPD techniques was performed. We made use of the protocol described by Zhang et al. using primers OPA-2 and OPA-18. Bacteria were grouped by species. We also included strains from an epidemic outbreak of postsurgical infections due to RGM that were sent to us as a reference laboratory as a control for the technique. Band profiles were compared by using the Bio-Profil software (BioGene, USA).

Results:  

During the study period 53 patients had clinical samples where RGM were isolated. The isolates were identified as M. chelonae (23), M. fortuitum (15), M. peregrinum (8), M. abscessus (3) and M. mucogenicum (4), 36 isolates (16 M. chelonae, 11 M. fortuitum, 7 M. peregrinum, 1 M. abscessus and 1 M. mucogenicum) were isolated during the period 1995–1997. No clear relationship between patients could be found after reviewing their clinical charts. RAPD showed readable profiles for all but one strains. The primer OPA-2 demonstrated a discriminative power similar to the OPA-18 one. Using OPA-2 one cluster was detected with a 1% homology coefficient (UPGMA), and 2 more different clusters appeared when a 5% homology coefficient was applied, all of them being M. chelonae strains. Using OPA-18 no cluster was detected for 1% homology coefficient, but when 5% homology coefficient was applied 4 clusters were detected. No predominant strain was detected in the isolates of the period 1995–1997.

Conclusions:  

An increase of the isolates of RGM was detected in a 3-year period, despite no changes in the protocol were performed. No predominant strain or outbreak was detected, so the increase of the number of isolates could be due to other causes than the existence of predominant strains. RAPD is an easy and valuable technique for evaluating the epidemiological relation between strains when the isolates are included in the same gel.