TRANSMISSION OF NOCARDIOSIS AND MOLECULAR TYPING OF NOCARDIA SPECIES - A SHORT REVIEW

Nocardia species are ubiquitous in the environment and may be found in the soil. They are generally responsible for sporadic pulmonary disea ses acquired by inhalation of spores, with secondary localizations in the central nervous system and subcutaneous tissues. There is no absol ute evidence for person to person transmission. Presumptive outbreaks of nocardiosis were observed in immunocompromised patients, more frequ ently in kidney transplant patients than in cardiac transplant patient s. Nocardia spp., being present in dust particles, closure and disinfe ction of the transplantation unit with formaldehyde arrested the seque nce of cases of nocardiosis. The original sources of the Nocardia sp. remain doubtful. Other possible sources of contamination are other pat ients, medical staff and the hospital environment. The first studies o f Nocardia spp. typing were based on the detection of extracellular an tigens, on the susceptibility of actinomycete strains to killer yeasts , and on the biochemical profiles with fluorogenic substrate. The use of molecular typing techniques have given very promising results. Anal ysis of plasmid profiles is an interesting way to compare the identity of isolates, although the reliability of this method depends of the p resence of plasmids in the isolates. Other typing methods, including a nalysis of restriction length fragment polymorphism of total DNA, ribo somal DNA fingerprinting, require further investigations to evaluate t heir discriminating power or to be easily interpretable, whereas a ran dom amplified polymorphic DNA (RAPD) assay was successful for epidemio logical purposes. Progress in epidemiological analysis of cases of noc ardiosis will be consistent when an improved diagnosis of this infecti on (molecular and serological diagnosis) will be available, when the g enetic diversity of Nocardia spp. isolates will be better known, and w hen molecular typing, that hold promise in complementing investigation s of outbreak of these infections, will be systematically performed wh en an abnormal increase of cases of nocardiosis in a population with r isk factors is observed.