The biological properties and special characteristics of the human T mycoplasmas have been reviewed and summarized. The T mycoplasmas are distinguished from all other known mycoplasmas by their production of urease, and, therefore, by their ability to hydrolyze urea. This singular property significantly sets the T mycoplasmas apart from all other members of the order Mycoplasmatales. In consideration of this distinguishing property, it is reasonable to propose establishing a new, separate genus in the family Mycoplasmataceae in which t o classify the T mycoplasmas isolated from man and lower animals. The name Ureaplasma is proposed for this new genus, which at present contains a single human species of at least eight different serotypes. The name Ureaplasma urealyticum is proposed for this new species. The type strain of U. urealyticum is human strain 960-(CX8), serotype VIII (Black); it has been deposited in the American Type Culture Collection as ATCC 27618.T mycoplasmas were first recognized and identified in 1954 in primary agar cultures of urethral exudates from male nongonococcal urethritis patients. They were called "tiny-form PPLO" (pleuropneumonia-like organisms) and "T-form colonies of PPLO" after the minute size, distinctive characteristics, and morphology of their agar colonies. The first published reference to these unusual mycoplasmas was a brief description accompanying two photomicrographs of "T" colonies in a primary agar culture of urethral exudate (53). Subsequent studies confirmed that T mycoplasmas were new, previously undescribed members of the human mycoplasma group. Their distinctive morphology and cultural characteristics were described and illustrated in detail in 1956 (54).The original minute colony size (10 * 5 pm) was the result of nutritionally inadequate culture media of distinctly unfavorable alkaline reaction (pH 7.8 to 8.0) resulting in near threshold performance in supporting growth of T mycoplasmas. Some of the early failures of other investigators t o isolate T mycoplasmas from clinical exudates may also be explained by the incorporation by these investigators of thallium acetate in the medium in accordance with standard classical mycoplasma methodology. This antibacterial agent is almost completely inhibitory t o many strains of T mycoplasmas in primary agar cultures in alkaline media of pH 7.8 t o 8.0. Thallium acetate was never employed in Shepard's laboratory , where only penicillin was incorporated as an antibacterial agent (1,000 U/ml).Prior to 1966, identification of T mycoplasmas in primary cultures was limited exclusively to characteristic minute size, morphology, and staining reaction of agar colonies. The subsequent development of improved agar culture media made identification based upon the above-mentioned criteria less reliable, since T colonies were no longer really "tiny." Identification was especially difficult under conditions of crowding in mixed mycoplasma cultures since classical mycoplasma colonies often completely lost the ability to produce the surface...

The phenotypic and genotypic properties of Ureaplasma urealyticum (family Mycoplasmataceae, order Mycoplasmatales, class Mollicutes) are reviewed here. The 14 recognized serovar standard strains found in humans exhibit no serological cross-reactivity with ureaplasmas from other hosts and uniquely express human immuoglobulin A1 protease activity. However, they exhibit many characteristics which place them in two distinct clusters known as the parvo biovar (or biovar 1 or B) and the T960T biovar (or biovar 2 or A). Established phenotypic markers of the biovars include clustering of antigenic types, polypeptide patterns of whole-cell preparations, differential inhibition by manganese, and polymorphism among their ureases, pyrophosphatases and diaphorases. Established genotypic markers of the biovars are DNA-DNA hybridization of 60% between biovars, and distinctive RFLP patterns and genome sizes. Divergent nucleotide sequences of several highly conserved genes attest to the phylogenetic distinctiveness of the two biovars. PCRs founded upon the sequences for 16S rRNA, the 16S-23S rRNA intergenic regions, the genus-defining urease, the serovar-defining, multiple-banded antigen genes or randomly amplified polymorphic DNA tests differentiate the biovars unambiguously. With the availability of rapid, reliable and economical tests for biovar determination, it is now appropriate to propose that the taxonomic status of U. urealyticum be emended. Serovar standard strains exhibiting traits of biovar parvo (serovars 1, 3, 6 and 14) will be designated as a separate species, Ureaplasma parvum sp. nov., as befits its smaller genome size. The serovar 3 standard (strain 27T) will be the type strain of U. parvum and is represented by ATCC 27815T and NCTC 11736T. Serovar standard strains exhibiting traits of biovar T960T (2, 4, 5, 7, 8T, 9, 10, 11, 12 and 13) will retain the U. urealyticum designation and type strain, the serovar 8 standard (strain T960T), represented by ATCC 27618T and NCTC 10177T.

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T-strain mycoplasmas require urea for propagation, but urea metabolism also occurs in nonpropagating viable cultures. Ammonia results from this metabolism and alkalinizes the medium. Ammonium ions and an alkaline p H both inhibit the multiplication of T strains and reduce the viability of T strains in broth. These toxic effects of urea metabolism currently limit the growth of T strains in broth. Stock T-strain cultures are optimally maintained in continuous culture if the routine medium at p H 6.0 is supplemented with 0.05% urea and 0.002% phenol red, but an incubation temperature of 30 C is preferable to 37 C for subculture at 24-hr intervals.

The conditions under which "T-strain" pleuropneumonia-like organisms, as described by Shepard, are best cultured were investigated. The organisms were found to grow on several types of nutrient agar and broth, of which PPLO medium supplemented with yeast extract and horse serum was the simplest. Subculture was possible through broth cultures, provided the broths were not incubated longer than 16 hr. The organisms on agar required either Fortner's anaerobic atmosphere or-10% C02, but broth cultures grew aerobically. "T-strains" grew over a pH range of 6.8 to 7.8, and a temperature range of 30 to 1028

Six women developed chronic long-term arthropathy after postpartum immunization against rubella. All individuals developed acute polyarticular arthritis within 12 days to three weeks postimmunization and have had continuing chronic or recurrent arthralgia or arthritis for two to seven years after vaccination. Acute neurological manifestations, consisting of carpal tunnel syndrome or multiple paresthesiae, developed postvaccination in three women. Two have developed continuing active or chronic recurrent episodes of blurred vision, paresthesiae, and painful limb syndromes together with recurrent joint symptoms. Chronic rubella viremia has been detected in peripheral blood mononuclear cell (MNC) populations in five of the six women up to six years after vaccination. In addition rubella virus was isolated from breast milk MNCs in one individual at nine months postvaccination and from peripheral blood MNCs in two of four breast-fed infants studied at 12-18 months of age. Immune responses to rubella virus studied at sequential intervals after vaccination correlated with development of rheumatologic and neurological manifestations.

Mycoplasma have been isolated from the human genital tract for 30 years, and yet their role in the production of disease is still not clarified. Initially, the isolates had a typical "fried-egg" morphology and were classified as M. horninis or M . ferrnentans strains.' A recent study2 in Vancouver, B. C., Canada, confirmed that M. horninis 1 was the most common organism having classical morphology, with 94 of 100 strains from women and all of 17 strains from men being serologically typed by the disc inhibition method of Clyde3 as M. horninis 1. The remaining six strains from women fermented glucose, and were thought to be related to M. ferrnentans although they were not inhibited by M. ferrnentans antiserum. No M. horninis 2 organisms were found. In 1956, Shephard4 described the Tstrains, which have subsequently proved to be not only morphologically and culturally different but also biochemically and serologically distinct from M. horninis