Pathogenicity of Mycoplasma fermentans and Mycoplasma penetrans in experimentally infected chicken embryos

Evaluation of Mycoplasma inactivation during production of biologics: egg-based viral vaccines as a model

Although mycoplasmas are generally considered to be harmless commensals, some mycoplasma species are able to cause infections in pediatric, geriatric, or immunocompromised patients. Thus, accidental contamination of biologics with mycoplasmas represents a potential risk for the health of individuals who receive cell-derived biological and pharmaceutical products. To assess the efficiency of inactivation of mycoplasmas by the agents used in the manufacture of egg-derived influenza vaccines, we carried out a series of experiments aimed at monitoring the viability of mycoplasmas spiked into both chicken allantoic fluid and protein-rich microbiological media and then treated with beta-propiolactone, formalin, cetyltrimethylammonium bromide, Triton X-100, and sodium deoxycholate, which are agents that are commonly used for virus inactivation and disruption of viral particles during influenza vaccine production. Twenty-two mycoplasma species (with one to four strains of each species) were exposed to these inactivating agents at different concentrations. The most efficient inactivation of the mycoplasmas evaluated was observed with either 0.5% Triton X-100 or 0.5% sodium deoxycholate. Cetyltrimethylammonium bromide at concentrations of >or=0.08% was also able to rapidly inactivate (in less than 30 min) all mycoplasmas tested. In contrast, negligible reductions in mycoplasma titers were observed with 0.0125 to 0.025% formaldehyde. However, increasing the concentration of formaldehyde to 0.1 to 0.2% improved the mycoplasmacidal effect. Incubation of mycoplasmas with 0.1% beta-propiolactone for 1 to 24 h had a marked mycoplasmacidal effect. A comparison of the mycoplasma inactivation profiles showed that strains of selected species (Mycoplasma synoviae, Mycoplasma gallisepticum, Mycoplasma orale, Mycoplasma pneumoniae, and Acholeplasma laidlawii) represent a set of strains that can be utilized to validate the effectiveness of mycoplasma clearance obtained by inactivation and viral purification processes used for the manufacture of an inactivated egg-based vaccine.

Hemolytic and hemoxidative activities in Mycoplasma penetrans

Mycoplasma penetrans is a newly isolated Mollicute from the urine of patients infected with human immunodeficiency virus that demonstrates the capacity to adhere to and invade human cells. A previous report, based on assays with mouse red blood cells (RBCs), indicated that M. penetrans lacked hemolytic activity. In our studies, we incubated different isolates of M. penetrans with various RBC species and observed hemolytic zones surrounding individual mycoplasma colonies. All M. penetrans strains displayed hemolysis after 2 to 3 days of incubation. Hemolytic activity diffused from single colonies, eventually causing complete lysis. Hemolysis was most pronounced with sheep RBCs, followed by horse, chicken, and human cells. Furthermore, hemolytic activity was demonstrable in both intact mycoplasma cell preparations and spent culture supernatant. However, unlike intact mycoplasmas, the hemolytic activity in the supernatant was dependent on the reducing agent, cysteine. In addition to hemolysis, a brown precipitate was closely associated with mycoplasma colonies, suggesting oxidation of hemoglobin. Absorption spectra indicated that hemoglobin was oxidized to methemoglobin, and the addition of catalase demonstrated H(2)O(2)-mediated hemoxidation. Other experiments suggested that hemoxidation enhanced total hemolysis, providing the first evidence of both hemolytic and hemoxidative activities in M. penetrans.

Phase variations of the Mycoplasma penetrans main surface lipoprotein increase antigenic diversity

Mycoplasma penetrans is a recently identified mycoplasma, isolated from urine samples collected from human immunodeficiency virus (HIV)-infected patients. Its presence is significantly associated with HIV infection. The major antigen recognized during natural and experimental infections is an abundant P35 lipoprotein which, upon extraction, segregates in the Triton X-114 detergent phase and is the basis of M. penetrans-specific serological assays. We report here that the P35 antigen undergoes spontaneous and reversible phase variation at high frequency, leading to heterogeneous populations of mycoplasmas, even when derived from a clonal lineage. This variation was found to be determined at the transcription level, and although this property is not unique among the members of the class Mollicutes, the mechanism by which it occurs in M. penetrans differs from those previously described for other Mycoplasma species. Indeed, the P35 phase variation was due neither to a p35 gene rearrangement nor to point mutations within the gene itself or its promoter. The P35 phase variation in the different variants obtained was concomitant with modifications in the pattern of other expressed lipoproteins, probably due to regulated expression of selected members of a gene family which was found to potentially encode similar lipoproteins. M. penetrans variants could be selected on the basis of their lack of colony immunoreactivity with a polyclonal antiserum against a Triton X-114 extract, strongly suggesting that the mechanisms involved in altering surface antigen expression might allow evasion of the humoral immune response of the infected host.

Multiplex PCR for the detection of Mycoplasma fermentans, M. hominis and M. penetrans in cell cultures and blood samples of patients with chronic fatigue syndrome

A multiplex polymerase chain reaction (PCR) was initially developed to detect the presence of mycoplasma genus DNA sequences in cell cultures and to differentiate between three human pathogenic mycoplasma species simultaneously. The assay in turn, proved to be a useful tool for the detection of mycoplasma infection in human DNA samples. One set of oligonucleotide primers which are specific for a highly conserved region among all members of the genus mycoplasma along with three other primer sets which are specific for Mycoplasma fermentans, Mycoplasma hominis andMycoplasma penetrans species were used in this assay. The sensitivity of detection was determined by infecting peripheral blood mononuclear cells (PBMC) of healthy individuals with known bacterial copy numbers from each species, extracting the DNA, and subjecting 1 microgram of DNA from each sample to 40 cycles of amplification. By using agarose gel electrophoresis the detection level was determined to be 7, 7, 9 and 15 mycoplasma cells per microgram of human genomic DNA for M. genus,M. fermentans, M. hominis and M. penetrans, respectively. The assay was applied to DNA extracted from the PBMCs of individuals suffering from chronic fatigue syndrome (CFS) (n=100) as determined by the Center for Disease Control (CDC) criteria, and compared to healthy individuals (n=100). The percentage of M. genus infection was found to be 52% in CFS patients and only 15% in healthy individuals. Mycoplasma fermentans, M. hominis andM. penetrans were detected in 32, 9 and 6% of the CFS patients while they were detected in 8, 3 and 2% of the healthy control subjects, respectively. This assay provides a rapid and cost efficient procedure to screen either cell cultures or clinical samples for the presence of three potentially pathogenic species of mycoplasma with a high level of sensitivity and specificity.