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Mycoplasma hominis, the first mycoplasma of human origin to be isolated, has been associated with several diseases, notably bacterial vaginosis, pelvic inflammatory disease, prematurity and puerperal fever. The mouse model does not mimic closely these features of human disease, but has some notable features. Given intravaginally to mice, M. hominis does not colonize unless the mice have been pre-treated with oestradiol. As shown here, endogenous hormone has no part to play because removal of the ovaries does not interfere with vaginal colonization. Persistent colonization occurs in hysterectomized mice so that organisms in the upper tract, which are sometimes found, are not responsible, by retrograde leakage, for those in the lower tract. Organisms in the lower tract can be eliminated by treating mice with a tetracycline, or progesterone or by natural resolution. Elimination by whatever means results in a rather weak immunity to recolonization. In contrast, intravenous inoculation of viable, and particularly killed, M. hominis organisms results in strong resistance to recolonization. This is, in part, genetically influenced, being seen in mice of strain BALB/c but not of strain CBA. Resistance is inversely proportional to the presence and titre of M. hominis specific serum antibody. The possible role of cell-mediated immunity is discussed.

Priapism seen occasionally in mice used in various mycoplasmal studies over several years prompted further investigation. Of six strains of young adult male mice inoculated intravenously with Mycoplasma pulmonis, of murine origin, priapism was seen only in CBA mice, penile erections persisting in some for seven to 44 weeks. A few mice given broth medium without mycoplasmas also developed priapism, and mice given five mycoplasmal species, of human origin, developed the condition in a way similar to these controls. However, those given M. pulmonis developed priapism earlier and of longer duration than other mice, suggesting that it was an enhancing factor. The duration of the phenomenon is remarkable and, as yet, has no clear explanation.

Three serovars (5, 8 and 10) of Ureaplasma urealyticum were inoculated intravaginally into groups of oestradiol-treated young adult BALB/c strain mice. Hormone treatment was essential for vaginal colonisation. The proportion of mice colonised initially and the persistence of colonisation were different with the three serovars; half of those given serovar 8 were still colonised after 84 days. A strain of serovar 5 after a further 50 subcultures in vitro was a little less persistent than it was before such subculture, but not in a way to suggest that subculturing was the main reason for differences in the behaviour of the serovars. At autopsy of six mice that were still colonised vaginally 158 days after inoculation of serovar 8, spread to the upper genital tract was shown to have occurred in three of them and dissemination to the liver and kidney in one. Compared with immunocompetent mice of strain CB20, such dissemination was not a feature in genetically related mice with severe combined immunodeficiency. This is not in keeping with the situation in hypogammaglobulinaemic patients in whom ureaplasmas and other mycoplasmas are known to disseminate. However, differences in the proportion of immunocompetent mice colonised or in ureaplasmal persistence with different serovars may act as a marker for differences in human pathogenicity and is worthy of further study.

Mycoplasma pneumoniae and M. genitalium are genomically distinct but share antigens that induce some serological cross-reactivity. Therefore, the possibility that M. pneumoniae infection of the human respiratory tract might provide immunity to M. genitalium infection of the genital tract was considered. Because of the difficulty of assessing this proposition in man, it was evaluated experimentally in a mouse model. Female BALB/c mice were susceptible to infection of the vagina with M. pneumoniae, whereas those infected previously in the oropharynx with M. pneumoniae were completely immune to infection of the vagina with this mycoplasma. However, all mice with such a respiratory tract infection were susceptible to infection of the vagina with M. genitalium. The findings suggest that an M. pneumoniae infection of the human respiratory tract is unlikely to influence infection of the genital tract by M. genitalium.

Antibiotics were given subcutaneously to female mice, colonized by mycoplasmas in the vagina and by others in the oropharynx. Mycoplasma pulmonis was eradicated from the vagina of 36 of 42 immunocompetent TO or BALB/c mice with oxytetracycline, and from 17 of 18 TO mice with lymecycline. Mycoplasma hominis was eradicated from the vagina of all of 18 immunocompetent BALB/c mice with oxytetracycline or tetracycline. Regarding oropharyngeal organisms, M. pulmonis was eradicated from only 20 of 42 TO or BALB/c mice with oxytetracycline and from none of 15 mice with lymecycline. However, Mycoplasma pneumoniae was eliminated from the oropharynx of eight of nine BALB/c mice with oxytetracycline. In contrast to the success in eradicating mycoplasmas from the vagina or oropharynx of immunocompetent BALB/c mice with oxytetracycline, no such effect was seen in nude BALB/c mice, indicating the importance of a competent immune system in conjunction with antibiotic treatment for eradication of these organisms.

Since 1937, 13 Mycoplasma species, two Acholeplasma species, and one Ureaplasma species have been isolated from humans. Six of these have the urogenital tract as the primary site of colonisation but others, which have the oropharynx and respiratory tract as the primary site, are found occasionally in the urogenital tract because of orogenital contact. Mycoplasma hominis was the first to be isolated and is most strongly associated with bacterial vaginosis (BV), together with a variety of other bacteria. Its involvement in pelvic inflammatory disease (PID) and other conditions may be as part of BV, although when isolated in pure culture from the blood of women who have postpartum or postabortal fever there is no reason to suspect its aetiological role. There is evidence for an aetiological role for Ureaplasma urealyticum organisms (ureaplasmas) in acute non-gonococcal urethritis (NGU) and particularly chronic NGU in men, but they rank third to Chlamydia trachomatis and M. genitalium. Whether the association of ureaplasmas with miscarriage and preterm labour is in the context of BV is not clear. Of no doubt, however, is the ability of ureaplasmas to cause septic arthritis in hypogammaglobulinaemic patients and there is evidence that they may cause some cases of sexually acquired reactive arthritis. The advent of polymerase chain reaction technology has seen an advance in the understanding of the role of M. genitalium; there is strong evidence that it is one of the causes of both acute and chronic NGU independent of C. trachomatis. There is some support for the role of M. genitalium in PID, but this needs to be substantiated. Other mycoplasmas, for example M. fermentans, M. pivum, M. primatum, M. penetrans, M. spermatophilum and even M. pneumoniae have the capacity to cause urogenital tract disease but there is no evidence to indicate that they do so.

A survey of 358 patients with primary antibody deficiency shows that mycoplasmal infection is the commonest cause of severe chronic erosive arthritis. We review our experience with 18 patients with confirmed or probable mycoplasmal arthritis. There was a broad spectrum of severity from a monoarthritis rapidly responding to tetracyclines to severe debilitating polyarthritis, sometimes with antibiotic-resistant organisms which in two cases were eliminated following hyperimmune animal serum therapy. Most patients had very low serum 1gG levels at the onset of arthritis, suggesting that maintaining levels within the normal range with immunoglobulin replacement may prevent infection. The unique susceptibility of these patients to mycoplasmal arthritis shows that antibodies play a crucial role in protection against these organisms.

A case is reported of common variable immunodeficiency (CVID) presenting as an acute septic arthritis due to Mycoplasma hominis. The diagnosis was not considered until the hypogammaglobulinaemia was discovered and the synovial fluid cultured specifically for mycoplasmas. The importance of diagnosing immunodeficiency states and searching for mycoplasmas in 'bacteriologically culture negative' cases is emphasized.

Thirty young adult mice, of strain BALB/c, treated previously with progesterone, were inoculated intravaginally (10 mice) or directly into the uterus (10 mice) with Mycoplasma pulmonis and 10 mice remained uninoculated. Ten mice not treated with the hormone were also inoculated intrauterinely with M. pulmonis. The same numbers of mice treated with oestradiol were inoculated in the same ways with M. hominis. Vaginal swab specimens were obtained from all mice 7, 14 and 28 days after inoculation and samples of genital tract tissue were collected from pairs of mice at the same time intervals. Large numbers of M. pulmonis and M. hominis organisms were isolated from the vagina throughout the course of the experiments and they were cultured also from the cervix and uterine horns. Mycoplasma-like bodies were demonstrated by scanning electron microscopy in the cervix and in the uterus, but neither mycoplasmal species was found attached to vaginal epithelium. The results of silver-enhanced immunogold labelling in conjunction with scanning microscopy provided assurance that the mycoplasma-like bodies were, in fact, mycoplasmas. The importance of hormone treatment was indicated by the diminished susceptibility of untreated mice to M. pulmonis and the almost complete insusceptibility to M. hominis, shown by culture and scanning electron microscopy.

Resistance against vaginal colonisation by Mycoplasma pulmonis in strain TO mice after exposure to the mycoplasma was investigated. Eighteen mice from which M. pulmonis had been eliminated from the vagina, either naturally or by antibiotic therapy, were resistant to vaginal recolonisation. Specific antibody was measured by an indirect microimmunofluorescence technique and the geometric mean titre (GMT) for each group of mice is presented. Almost all of 31 mice that had developed circulating antibody (GMT 83) or local antibody (GMT 40), or both, after vaginal exposure were resistant to re-colonisation, as were those in which antibodies could not be detected. Seven other mice which had been colonised only in the oropharynx previously and which possessed antibody--circulating (GMT 64) or local (GMT 30), or both--were resistant to vaginal colonisation, but 13 mice with little or no antibody after lack of colonisation at either anatomical site were susceptible. All of 15 mice given killed M. pulmonis organisms intravenously, despite developing circulating antibody in high titre (GMT 122), were susceptible to vaginal colonisation, as were 14 of 15 mice that developed circulating (GMT 15) and local antibodies after being given killed organisms intravaginally. However, 25 mice with high titres of circulating (GMT 154-170) or local (GMT 20) antibody, or both, after receiving live organisms intravenously, were less susceptible to vaginal colonisation (17 becoming colonised) than were 21 non-immunised mice (all becoming colonised) and the organisms were eradicated more rapidly from the former. Despite this, the mice that were colonised following intravenous inoculation of live organisms had pre-challenge antibody titres that were as great as those that were not colonised.(ABSTRACT TRUNCATED AT 250 WORDS)

Objectives: To study the occurrence of mycoplasmas and ureaplasmas in patients with hypogammaglobulinaemia and the relationship of these micro-organisms to septic arthritis., Methods: Over a period of about 20 years, 53 men and 38 women with hypogammaglobulinaemia, most of whom were less than 50 years old, were examined clinically and microbiologically. Mycoplasmas and ureaplasmas were sought in the throat, urogenital tract and joints by standard cultural methods, although not consistently in the three sites of all patients., Results: Arginine-hydrolysing mycoplasmas and ureaplasmas occurred with similar frequency in the sputum/throat of the hypogammaglobulinaemic patients, but no more often than might be expected in immunocompetent patients. Ureaplasmas, however, dominated in the urogenital tracts of both men and women, being found in 75% of vaginal specimens. Arginine-hydrolysing mycoplasmas occurred two to six times more frequently and ureaplasmas two to three times more frequently in urine specimens from hypogammaglobulinaemic patients than they did in such specimens from sex- and age-matched non-venereal disease, hospital patients or healthy subjects; these differences were statistically significant (p < 0.05). Enhanced mucosal colonisation probably increases the chance of spread to distant sites, such as the joints. Of the 91 patients, 21 (23%) had septic arthritis involving one or more joints. Mycoplasmas and/or ureaplasmas, but not bacteria, were isolated from the joints of eight (38%) of these patients. However, dissemination to joints apparently had not occurred in some despite the opportunity by virtue of mycoplasmal or ureaplasmal colonisation at a mucosal site. Sometimes antibiotic therapy failed clinically, and microbiologically and recommendations for management are outlined., Conclusions: Hypogammaglobulinaemic patients appear to be more susceptible to colonisation of mucous membranes, especially of the urogenital tract, with mycoplasmas and ureaplasmas than are immunocompetent individuals. These micro-organisms are responsible for about two fifths of the septic arthritides occurring in these patients.

Intranasal inoculation of 12 young adult mice (strain TO) with Mycoplasma pulmonis protected all of them against vaginal colonization when they were challenged intravaginally 60 days later with the same mycoplasmal strain. In contrast, all 15 mice without a respiratory infection became colonized vaginally (geometric mean titre [GMT] 4.6 x 10(6) colour-changing units [c.c.u.]) when challenged in the same way. The GMT of serum antibody, measured by a microimmunofluorescence technique, prior to challenge was 200 and 8 for the oropharyngeally infected and unexposed mice, respectively. The GMT of antibody in vaginal washings from the two groups was 6 and 3, respectively. All four nude BALB/c mice were susceptible to vaginal colonization (GMT 5.6 x 10(6) c.c.u.) after oropharyngeal infection (GMT 5.1 x 10(4) c.c.u.) resulting from intranasal inoculation, as were all six nude mice (vaginal GMT 1.4 x 10(7) c.c.u.) that had not been inoculated intranasally. In contrast, all ten of their immunocompetent counterparts were resistant to vaginal colonization after oropharyngeal infection (GMT 1.3 x 10(3) c.c.u.), whereas all nine such mice that had not been infected oropharyngeally were susceptible to vaginal colonization (GMT 7.6 x 10(6) c.c.u.). These results show the important role that a respiratory infection has in protecting the vagina against colonization and that protection is dependent on a functioning T-lymphocyte system.

Progesterone induces susceptibility in murine genital tracts to Mycoplasma pulmonis, Mycoplasma pneumoniae, and Mycoplasma genitalium when each is given intravaginally. In contrast, estradiol, but not progesterone, induced such susceptibility to Ureaplasma urealyticum, Mycoplasma hominis, and Mycoplasma fermentans, the "incognitus" and PG18 strains of the latter behaving similarly. None of the mice that had been given M. fermentans intravaginally died, whereas others that had been given large numbers of M. fermentans organisms intraperitoneally died within a few days. M. pulmonis spreads from the respiratory tract to other sites more often in T cell-depleted mice than in immunocompetent mice. In addition, the "incognitus" strain of M. fermentans given intravenously killed BALB/c nude mice but did not kill immunocompetent control mice of the same strain or CBA nude mice. The effect is not unique to M. fermentans since M. hominis inoculated intravenously also killed CBA nude mice or made them ill. Such observations raise the possibility that immunosuppression caused by the human immunodeficiency virus could allow mycoplasmas to flourish and exacerbate disease.

A survey of previous evidence for the intracellular localization of mycoplasmas within nonphagocytic cells indicated that it was insufficient to conclude unequivocally that such localization occurred. Illustrations of the seemingly intracellular existence of Mycoplasma fermentans in the tissues of patients with AIDS and other patients rekindled interest in the topic of mycoplasmal entrance into epithelial cells. Accordingly, the "incognitus" and PG18 strains of M. fermentans were sought and demonstrated within HeLa cells by electron microscopy following treatment of the cell cultures with gold-labeled antiserum specific to the mycoplasma, together with ruthenium red staining. The phenomenon is not unique to this mycoplasma, being demonstrated also with Mycoplasma hominis. In hindsight, some of the earlier investigators who hinted at intracellular localization were probably correct in doing so.

The genital tract of young female mice was rendered susceptible to colonisation with Mycoplasma pulmonis by pre-treating them with progesterone (usually 2.5 mg) given subcutaneously at weekly intervals for 4 weeks. Colonisation was influenced by the size of the inoculum and by the dose of progesterone; at least 2.5 x 10(4) organisms and at least 0.5 mg of hormone (administered on four occasions) were required. The duration of colonisation was related also to the size of the inoculum and the dose of progesterone. Similar results were obtained in TO, BALB/c and CBA strains of mice. Progesterone treatment induced the dioestrous stage of the reproductive cycle within 5 days and the cycle of the majority of untreated, mycoplasma-susceptible mice was also at this stage. However, mice, particularly of the CBA strain, were far less susceptible when not given progesterone and the mycoplasmas tended to persist for a shorter time. Mice treated with oestradiol, even in small doses, became completely refractory to infection with M. pulmonis. In vitro, progesterone inhibited the growth of M. pulmonis, as did oestradiol, but vaginal washings from progesterone-treated mice were no more inhibitory than those from untreated mice. Thus, the success of progesterone in enhancing colonisation could not be attributed to a direct stimulatory effect of the hormone at the mucosal surface and we suggest that it may be due to a greater availability of progesterone-induced receptors for mycoplasmas in the dioestrous phase of the reproductive cycle than in the oestrous phase.

Colonization of the genital tract of female mice, mainly BALB/c, by Mycoplasma genitalium, M. pneumoniae and M. pulmonis was enhanced by pretreatment of the mice with progesterone. M. fermentans, M. hominis and M. salivarium, and three serotypes and two untyped strains of Ureaplasma urealyticum colonized under the influence of oestradiol but not progesterone. Mycoplasmas dependent on progesterone were glucose-metabolizing, with strong haemadsorptive and other attachment properties, and possessed a terminal structure. Mycoplasmas dependent on oestradiol were arginine or arginine/glucose metabolizing. Ureaplasmas also required oestradiol. The oestradiol-requiring group appeared to be less cytadsorptive and devoid of a morphological terminal structure. Mycoplasmas that had had multiple passes in media were less able to colonize. This may be one, but not the only, reason for the failure of seven mycoplasmas to colonize under the influence of either hormone. The observations suggest the existence of a receptor mechanism for colonization, progesterone-requiring mycoplasmas being exposed to, and needing, genital tract cells different from those exposed to oestradiol-requiring mycoplasmas.

Mycoplasma fermentans (strain 'incognitus') was incubated with HeLa cells for up to 96 h. After 24 h, mycoplasma organisms were demonstrated intracellularly by immunocytochemistry using mule anti-M. fermentans antiserum and gold labelling on ultrathin sections of both Lowicryl K4M and Araldite-embedded HeLa cells, the latter being treated with hydrogen peroxide. The Araldite-embedded cells were fixed with glutaraldehyde and osmium tetroxide in the presence of ruthenium red to stain the mucopolysaccharide surface components of both the procaryotic and eucaryotic cells. Intracellular localization of some M. fermentans organisms was confirmed by exclusion of ruthenium red from their membranes. Various numbers of mycoplasma organisms were seen per cell and occasionally some were within vacuoles, the membranes of which were also unstained by ruthenium red. The PG18 strain of M. fermentans and a strain of M. hominis were also detected intracellularly using similar methodology and homologous mule or rabbit antisera. The occasional presence of both apparently normal and some denser degenerate mycoplasmas in the same cell may indicate gradual degradation by phagolysosomal digestion.

The polymerase chain reaction (PCR) was developed to detect Mycoplasma genitalium. Oligonucleotide primers were used to amplify a 374 bp region of the attachment protein of the mycoplasma. DNA from three strains of M. genitalium tested gave a characteristic PCR product which was not seen with DNA from any other source. As little as 10(-15) g of M. genitalium DNA could be detected and it was found in the vagina of progesterone-treated BALB/c mice inoculated with M. genitalium organisms later than they could be cultured from this site, but not in mice that never became colonised vaginally.

Germ-free BALB/c mice treated with oestradiol and inoculated intravaginally with a serum-resistant strain or a freshly isolated, piliated strain of Neisseria gonorrhoeae were colonised vaginally. The organisms were recovered intermittently for a month or longer and there was evidence that they could reach the upper genital tract. Mice given progesterone and those not treated with either hormone did not become colonised. This is the first evidence of sustained mucosal colonisation in animals other than chimpanzees.

Twenty progesterone-treated TO mice were infected intravaginally with Mycoplasma pulmonis. One month later, ten of the mice were given oestradiol which changed the reproductive cycle to the oestrous phase and within a week resulted in eradication of the organisms from six of them; vaginal persistence in the other mice may have been due, at least in part, to reinoculation of organisms from the oropharynx, a site heavily infected in all the mice. The majority of the mice not treated with oestradiol continued to shed the organisms from the vagina for at least 91 days. In another experiment, 19 oestradiol-treated BALB/c mice were infected intravaginally with M. hominis. One month later, nine of the mice were given progesterone which changed the reproductive cycle to the dioestrous phase and eradicated the organisms from seven within 2 weeks and from all of them within about a month. This was in contrast to the mice not given progesterone, the majority of which continued to shed the organisms for at least 167 days.

All of five lyophilised cultures of Mycoplasma orale kept for 23 years at room temperature were still viable, as were all but one of 12 lyophilised cultures of six Mycoplasma spp. that had been stored for 18-22 years at 4 degrees C. Similarly, 11 of 13 lyophilised ureaplasma cultures were viable after 8-22 years at 4 degrees C; the titre of organisms in the viable cultures had diminished no more than 100-fold. Seven broth cultures of five different Mycoplasma spp. all proved viable 5-13 years after being frozen and stored at -70 degrees C, although there was up to 10(4)-fold reduction in the titre of organisms in some cultures. Furthermore, 18 (82%) of 22 different Mycoplasma spp., originally lyophilised and then reconstituted and stored at -70 degrees C, were viable after 16 years. Viable organisms were found, with little or no reduction in titre, in all of seven broth cultures of Ureaplasma urealyticum, comprising six serotypes, after storage for 6-10 years at -70 degrees C, but five of 18 broth cultures of other human and animal ureaplasmas stored likewise were not viable after 13-14 years and in a further seven of them the titre of viable organisms had diminished greater than or equal to 10(4)-fold.

To examine the potential role of bacterial infection in the cause of spontaneous preterm labor, human amnion cells in tissue culture were exposed to medium conditioned by culturing each of 21 microorganisms previously found in association with chorioamnionitis and preterm labor. At a final concentration of 0.1% bacterial conditioned medium, a significant stimulation of prostaglandin E2 production from amnion cells was observed for this range of microorganisms. Conditioned medium obtained from culturing Bacteroides fragilis caused a dose-related increase in prostaglandin production, final concentrations of 0.02% to 0.1% being stimulatory but greater concentrations (0.1% to 10%) causing a progressive inhibition of prostaglandin synthesis. A similar concentration-related response in which stimulation was followed by inhibition occurred on addition of increasing concentrations of phospholipase A2 to amnion cells. These data suggest that bacterial phospholipase may release arachidonic acid from amnion leading to prostaglandin E2 synthesis, but excessive addition of phospholipase and consequent increased arachidonic acid availability may give rise to substrate inhibition of cyclooxygenase enzyme and inhibit prostaglandin E2 synthesis. Overall it appears that a wide variety of microorganisms associated with preterm labor may secrete phospholipase, which liberates amnion arachidonic acid for conversion to the oxytocic agent prostaglandin E2.

Chlamydia trachomatis elementary bodies (EBs) were found in synovial membranes or synovial fluid cell deposits from five of 15 women with seronegative mono- or oligoarthritis by means of a fluorescein conjugated anti-chlamydial monoclonal antibody (Micro Trak; Syva). Genital tract specimens were taken from only five of the patients, one of whom had intra-articular EBs, but none was chlamydia positive. Six of 10 patients tested were HLA-B27 positive, and chlamydial IgG antibody, measured by microimmunofluorescence, was present at a titre of 1/greater than or equal to 64 in the sera of five of the 15 patients, three of the five having EBs in their joints. In contrast, chlamydial EBs were not detected in the joints of a control group of 10 other women, most of whom had rheumatoid arthritis. None of them was HLA-B27 positive, and only one had a chlamydial antibody titre of 1/greater than or equal to 64. Neither Mycoplasma hominis nor ureaplasmas were isolated from the synovial fluids of seven patients and five controls who were tested. Antibody to M genitalium, however, was detected in five of the 10 patients but in none of the controls. This evidence apart, there was no other suggest that mycoplasmas or ureaplasmas might be responsible for arthritis which could not be attributed to chlamydiae.

Six of 58 patients with primary hypogammaglobulinaemia developed chronic urethritis and/or cystitis. We have some evidence that this complication may be caused by infection with strains Rof Ureaplasma urealyticum. This is important because ureaplasmas are usually resistant to most antibiotics routinely used to treat lower urinary tract infections. It appears that hypogammaglobulinaemic patients develop less localised and more severe ureaplasmal infections than immunocompetent subjects, which indicates that antibodies are important in controlling the growth of these organisms in the bladder and urethra.

Ureaplasmas were isolated from the oropharynx of all of 22 male and 19 female adult marmosets and from the genital tract of about a quarter of them. These ureaplasmas seem to be natural inhabitants of the oropharynx and not of human origin because half the animals had had very limited human contact and preliminary serological tests indicate that the organisms are not the same as the known human serotypes. 11 babies born in captivity were found to have oropharyngeal organisms usually within 24 h of birth and the oropharynx of the parents was thought to be the most likely source. The marmoset may be a useful model for studying the role of ureaplasmas in human disease.

31 women with acute pelvic inflammatory disease, in whom serum antibodies to Chlamydia trachomatis and Mycoplasma hominis could not be detected, were examined for antibodies to Mycoplasma genitalium by a microimmunofluorescence technique. About 40% of them had a fourfold or greater change in the titre of antibody during the one-month period after the onset of disease. This evidence implicates M genitalium in the aetiology of pelvic inflammatory disease.

Eighteen male and eight female primates, representing five subhuman species, were inoculated urogenitally with Mycoplasma genitalium, a microorganism recovered from men with nongonococcal urethritis. Male rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys apparently were resistant. Female squirrel monkeys (Saimiri sciureus) and female tamarins (Saguinus mystax) exhibited low-level, genital-tract infections. Male chimpanzees (Pan troglodytes) developed an obvious genital-tract infection, with some shedding organisms for 21 weeks. M. genitalium was recovered from the blood of two of the male chimpanzees, usually when large numbers of organisms were in the urethra. Female chimpanzees generally shed organisms for 12-15 weeks. Most chimpanzees colonized with the organism exhibited increased numbers of polymorphonuclear leukocytes in the genital tract and developed a significant antibody response. The results offer substantial evidence for the pathogenicity of M. genitalium for the urogenital tract of higher primates and suggest the microorganism may have a role in human genital-tract infections.

The relation between maternal genital colonization by mycoplasmas and fetal growth was examined in a study of 195 women. Swabs were taken from the endocervix on three occasions during pregnancy and once post partum. Ureaplasma urealyticum organisms (ureaplasmas) were recovered from 42.7 per cent of Caucasian women and from 34.6 per cent of Asian women at their first antenatal visit. These isolation rates remained similar throughout pregnancy, although there was a decrease in isolation after delivery. Mycoplasma hominis was recovered from 6.5 per cent of Caucasians and from 11.5 per cent of Asians at their first antenatal visit and these rates remained fairly constant during pregnancy and after delivery. Caucasian women colonized by ureaplasmas had a longer mean length of gestation (p less than 0.025) than non-colonized women. Furthermore, the colonized women gave birth to infants who had a statistically significant greater mean birth weight and a greater mean birth weight-for-dates than those of the non-colonized Caucasians. There was no correlation between gestational length, birth weight, or birth weight-for-dates and genital colonization of Asian mothers by ureaplasmas or M. hominis. It is clear the ureaplasmas are not associated with low birth weight in our population.

In an attempt to demonstrate the pathogenicity of a newly discovered mycoplasma (strain G37) isolated from the human genital tract, six female marmosets (Callithix jacchus) were inoculated intravaginally. Four of the animals were infected as indicated by repeated recovery of the organisms on vaginal swabbing, and infection persisted for 72-149 days or more. In addition, the infected marmosets exhibited a serum antibody response detected most easily by an immunofluorescence technique, and a persistent vaginal polymorphonuclear leucocyte response not seen in two uninfected and in two uninoculated animals.

As human genital mycoplasmas have been associated with various forms of reproductive failure, the present study was undertaken to investigate whether M. hominis and U. urealyticum organisms (ureaplasmas) are capable of crossing intact fetal membranes. Nearly 300 women in Denmark and England were investigated. Most of them were seen at about the fourth month of gestation and the remainder towards or at the time of birth, all with unruptured membranes. A swab was taken from the uterine cervix or vagina and M. hominis was isolated from 9% of the women and ureaplasmas from half of them. The presence of these mycoplasmas was not associated with an abnormal outcome of pregnancy. In contrast to the frequent presence of mycoplasmas in the lower genital tract, amniotic fluids obtained by transabdominal amniocentesis or at cesarean section did not contain M. hominis and ureaplasmas were isolated from only one of them. This was associated with the same ureaplasmas serotype being recovered from the cervix and also from the blood of both infant and mother, whose case differed from the others as labor had already started when the amniotic fluid was obtained. Thus, in our populations, we have no evidence that mycoplasmal invasion of the amniotic fluid occurs before the onset of labor. During labor, despite intact membranes, it seems that genital mycoplasmas may occasionally invade the fetal--placental unit, probably by the hematogenous route after strong uterine contractions, or otherwise directly after membrane rupture. Since both these events are followed usually by immediate delivery, there would seem to be insufficient time for the genital mycoplasmas to cause fetal damage.

Experimental Chlamydia trachomatis infection of the genital tract of female CBA and TO mice was greatly curtailed by a concurrent genital infection with Mycoplasma pulmonis. TO mice in which chlamydial infection had been suppressed by the mycoplasma infection were treated with the anti-mycoplasma agent, gentamicin. This did not cause a reappearance of the chlamydiae, suggesting that these organisms had been eliminated completely. The M. pulmonis infection stimulated a striking and persistent polymorphonuclear leukocyte response, which may have been the cause of the curtailment of the chlamydial infection.

Follicular cervicitis was recognised in 15 (44 per cent) of 34 women who were examined colposcopically and who were sexual partners of men with non-gonococcal urethritis. Valid results of culture for Chlamydia trachomatis were obtained in 26 cases: the organism was isolated from the cervix of five of 11 women in whom follicular cervicitis had been diagnosed, but from only one of 15 whose cervices did not have this change. A similar correlation was not found for infection with Mycoplasma hominis or Ureaplasma urealyticum.

Treatment of female BALB/c mice with oestradiol rendered them susceptible to vaginal colonization by three of four different strains of Mycoplasma hominis. Overall, the organisms were recovered persistently from the vagina of 68 (87%) of 78 of these mice. Strain TO mice given one of the strains were at least susceptible, all of ten becoming colonized and larger numbers of organisms being recovered. The hormone arrested the reproductive cycle in the oestrous phase, characterized by non-nucleated, cornified vaginal epithelial cells. In contrast, M. hominis organisms were isolated transiently from only seven (10.5%) of 66 BALB/c mice not treated with oestradiol, after intravaginal inoculation; treatment with progesterone, which induced the dioestrous phase of the cycle, did not render any of 10 BALB/c mice susceptible to vaginal colonization. The minimum number of organisms (2.5 x 10(5)) of one strain of M. hominis and the minimum dose of oestradiol (0.05 mg) required to induce persistent colonization were established. Vaginal colonization persisted for more than 200 d in some mice, the numbers of organisms recovered ranging between 10(1) and 10(8). At autopsy there was evidence of spread to the uterine horns and ovaries, and also to the oropharynx, of some animals but not to other organs. Infection was not associated with a polymorphonuclear leucocyte response in the vagina or elsewhere, but a fourfold serum antibody response to M. hominis, measured by the metabolism-inhibition technique, was detected in almost half of the mice tested.

A full-term baby boy had respiratory distress, fever and pneumonia within 20 h of birth. Isolation of Mycoplasma hominis from blood taken after 20 h and 11 days was accompanied by an antibody response. Although chlamydial IgM antibody was detected, chlamydial infection probably did not cause the pneumonia. Penicillin was ineffective but treatment with gentamicin, and particularly tetracycline, was associated with slow improvement. Mycoplasma hominis should be considered as a cause of respiratory disease and fever in neonates.

Young adult mice were inoculated intravenously with strains JB or Peter C of Mycoplasma pulmonis. A few were inoculated intranasally with strain JB. This strain but not Peter C was isolated for 50 days or more from the urines of more than half of the mice. Those of strains TO, C3H and CBA, but not CFLP, were susceptible. Recovery of mycoplasmas was intermittent and sometimes the numbers isolated varied within individual mice and between mice of a particular strain, ranging from 5 X 10(1) to greater than or equal to 5 X 10(7) colour-changing units/ml. Fifty serial passes of M. pulmonis, strain JB, in mycoplasmal medium resulted in attenuation, the organisms after inoculation of TO mice not being recovered from the urine and excretion not being stimulated by treating the mice with progesterone. At autopsy, the organisms of early passage were usually but not invariably isolated from the kidneys of mice that had been urinary excretors. About half of the latter had no renal histopathological changes. The others had usually minimal renal perivascular lymphocytic infiltrates but occasionally more widespread inflammatory changes. The findings may have relevance to the spread of mycoplasmal infection within mouse colonies and suggest that an association between such infection and nephritis in other species, including man, should be sought more closely.

Various eucaryotic cells adhere to colonies of some mycoplasmas (adsorption). The chemical nature of the receptors on the cells is not the same for all mycoplasma species, nor are the binding sites on different mycoplasmas the same. Some receptors comprise sialic acid, but in the case of Mycoplasma pulmonis, for example, attachment to cells is not mediated in this way. Nevertheless, adherence seems to be an important factor in the pathogenicity of this mycoplasma. Strain JB caused pneumonia in mice when inoculated intranasally, and colonies of this strain on agar absorbed erythrocytes (hemadsorption) strongly. After multiple passes in mycoplasma liquid medium, the strain lost its hemadsorbing capacity and also its mouse virulence, suggesting that the ability to attach to cells is virulence factor. Examination by electron microscopy of the virulent mycoplasma and its induced avirulent form after ruthenium-red staining showed that the stain was less thick on the surface of the avirulent form. In addition, the protein pattern of the avirulent mycoplasma, demonstrated by polyacrylamide gel electrophoresis, was deficient in three bands. These observations suggest that a glycosylated protein may form the binding site on M. pulmonis organisms that mediates their attachment to cells.

Thirty-three TO mice, 24 of which had received progesterone, were infected originally by Mycoplasma pulmonis given vaginally. Thirty-one of the mice were free of the organisms in the genital tract 236 days later at which time all of them were treated again with progesterone and rechallenged with M. pulmonis vaginally. All 31 mice were resistant. In contrast, of 21 TO mice of the same age that were not infected originally 15 (71%) became infected persistently after vaginal rechallenge. In similar experiments, 12 CBA mice, nine of which had received progesterone, were infected originally. Ten of these mice were free of the organisms genitally 2 years later, at which time all of them were rechallenged vaginally. Only two mice (20%) were reinfected, whereas six (86%) out of seven mice, not infected originally, were reinfected. Autopsy examination revealed that neither infection nor immunity was confined to the lower genital tract. Thus, M. pulmonis organisms were not detected in the upper tract of five TO mice that remained mycoplasma-free vaginally after rechallenge. The contribution of oropharyngeal M. pulmonis infection, which occurred in most of the mice, to the solid, long-lasting genital-tract resistance was difficult to assess, but in two mice, at least, immunity was not afforded by such infection.

We have shown that mycoplasmas bind spontaneously to neutrophils, as well as directly activating the first component of complement with probable subsequent binding through neutrophil complement receptors. Thus, antibody is not required to opsonize mycoplasmas for neutrophil phagocytosis. Furthermore, mycoplasmas remain viable when phagocytosed in the absence of antibody and may be carried inside neutrophils to various parts of the body to cause infection (e.g. joints). We found that antibody alone inhibits the growth of mycoplasmas in vitro. These observations suggest that the role of antibodies is to control the growth of mycoplasmas on mucosal surfaces; neutrophils play no part in defence and may even aid dissemination of the infection. This helps to explain why patients with hypogammaglobulinaemia are prone to systemic mycoplasma infections.

A series of meatal swabs, taken from 17 men over a period of 17 months during their tour at an Antarctic base was examined for mycoplasmas. The number of organisms isolated never exceeded 10(4) and not every specimen from each man yielded mycoplasmas. Nevertheless, Mycoplasma hominis was isolated from 71% and T-mycoplasmas from 59% of the men at some time during their stay. M. hominis persisted in the presence of serum IHA antibody titres of 1/64. Three subjects yielded only M. hominis and one only T-mycoplasmas.Six men had already spent a year at the base when the study began and mycoplasmas were still being isolated from some of them at the end of a 31 month period of isolation. The persistence of mycoplasmas in the male genital tract can therefore be independent of sexual contact. Two modes of persistence are suggested; either a few men act as carriers and reinfect the others by contaminating their environment, or as seems more likely, most men have chronic infections.

The lack of antibody in hypogammaglobulinemic patients probably results in failure of mycoplasmas to be "neutralized" and accounts for the diminished ability of the patients to cope with these organisms escaping hematogenously from the respiratory and urogenital tracts. Furthermore Ureaplasma urealyticum and other mycoplasmas are ingested by neutrophils in the absence of opsonins, indicated by the fact that they are able to trigger the release of chemiluminescence from these cells; ureaplasmas are not killed during this process and it is possible that carriage occurs within phagocytes to various sites. Several mycoplasmal species have localized in joints and U. urealyticum organisms are no exception. They have been isolated from the purulent synovial fluids of at least three hypogammaglobulinemic patients in Canada, England and the United States, respectively, the arthritides responding to appropriate antibiotic therapy. In one male patient, however, repeated and prolonged episodes of arthritis over several years, associated with antibiotic-resistant ureaplasmas, responded only to the administration of specific hyperimmune serum. Apart from joint involvement subcutaneous abscesses have been seen, and in the latter patient persistent urethritis was caused by ureaplasmas, these being the only organisms recovered from the urethra. Chronic urethrocystitis/cystitis in hypogammaglobulinemic patients has been associated also with ureaplasmal infection. In addition polyarthritis with recovery of both ureaplasmas and Mycoplasma hominis from the joints has been seen in a kidney allograft patient on an immunosuppressive regimen. However, further evidence that ureaplasmas cause a problem in immunosuppressed patients or in those with the acquired immunodeficiency syndrome is lacking.

Twenty-two men with non-gonococcal urethritis (NGU), 19 with gonorrhoea, and 22 without urethritis were examined for various micro-organisms. Chlamydia trachomatis was isolated from the urethra of 45% of men with NGU, 21% of those with gonorrhoea, but from none without urethritis. Ureaplasma urealyticum but not Mycoplasma hominis was recovered from a larger proportion of men with NGU than from those in the other groups. M genitalium was isolated presumptively from 32% of men with NGU, 12% of those with gonorrhoea, from 10% of men without urethritis, and from 42% of the men with NGU from whom chlamydiae were not isolated. U urealyticum, M hominis, and M genitalium were sought also in the rectum of men in the three groups. The first two micro-organisms were confined almost exclusively to homosexual men, whereas M genitalium was apparently not restricted in this way and was found particularly in this site in men with NGU. The latter mycoplasma may be a resident primarily of the intestinal tract. A fourfold or greater rise in the titre of antibody to C trachomatis was detected in about 20% of the patients with NGU, but not in other men. A similar rise in the titre of antibody to M genitalium was seen in 29% of the patients with NGU and in 12% of those without urethritis. A concomitant antibody response to M pneumoniae, which is antigenically related to M genitalium, was seen in one patient only. The responses to M genitalium suggest infection by this mycoplasma and indicate the need for further serological studies.

Marmosets, from which endogenous ureaplasmas had been eradicated by treatment with minocycline, were tested for susceptibility to infection by ureaplasmas from the genital and respiratory tracts of other animal species. They could be infected with ureaplasmas of human and simian origin, but were resistant to bovine and canine ureaplasmas. The results indicated that human, marmoset and squirrel-monkey ureaplasmas may form a biological subgroup, distinct from bovine and canine ureaplasmas, and that host range should not be ignored as a parameter for classification.