[Frontiers in Bioscience 1, e42-54, August 1,1996]


Catherine Brenner, Olivier Neyrolles, Alain Blanchard

Institut Pasteur, Unité d'Oncologie Virale, Département SIDA et Rétrovirus, 28, rue du Dr. Roux, 75724 Paris Cedex 15, France

Received 07/05/96; Accepted 07/09/96; On-line 08/01/96


Simultaneous with the publication of these in vitro observations, the isolation and detection of mycoplasmas in HIV-infected subjects was reported by various groups. M. fermentans was the first mycoplasma species reported to be invasive in AIDS patients. The first isolate, named incognitus, was identified as a strain of M. fermentans (28-31). In our laboratory, mycoplasma strains including M. fermentans (AOU) and M. pirum (BER) were isolated from blood of HIV seropositive patients (18). In another study, M. fermentans was isolated from the urine of two of 43 patients and seven were PCR-positive for this mycoplasma (32). The low sensitivity of culture as compared to PCR is a common characteristic of some mycoplasma species which are known to be extremely fastidious and therefore difficult to grow. This property is also exemplified by results from another study in which M. fermentans, identified using specific antiserum, could be cultured for one passage from several of urine samples collected from HIV-infected subjects, but subcultures failed to grow (33). Prior to these observations, M. fermentans was considered as a species rarely isolated from the human urogenital tract. It has been implicated in rheumatoid arthritis although the evidence is conflicting. Indeed recently published data indicate that the putative association with arthritic diseases remains under investigation (34).

M. penetrans was initially isolated from urine from six HIV seropositive male homosexuals (35, 36). To date, M. penetrans has only been isolated from HIV-infected subjects although epidemiological studies (see below) have indicated its presence in other HIV-seronegative subjects. This novel mycoplasma has an elongated flask shape with a terminal structure as shown in Figure 1.

Figure 1: Ultrastructural morphology of M. penetrans. A M. penetrans organism indicated by the arrow is shown within the cytoplasm, inside a vacuole of an lymphocyte experimentally infected with the mycoplasma. The insert shows a single M. penetrans cell from an in vitro culture; the thin section was treated with ruthenium red which reveals external layer of the capsule-like material. In both electron micrographs, the bar represents 300nm.

Under the electron microscope, two distinct compartments are observed: a densely packed tip-like structure and a broader body compartment with a more heterogeneous cytoplasm structure. A similar morphology has been described for another mycoplasma, M. iowae, a poultry pathogen. Comparative analysis of 16S rRNA genes indicates that M. penetrans and M. iowae are phylogenetically related (37).

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