Mycoplasmas and ureaplasmas as neonatal pathogens

Abstract

The genital mycoplasmas represent a complex and unique group of microorganisms that have been associated with a wide array of infectious diseases in adults and infants. The lack of conclusive knowledge regarding the pathogenic potential of Mycoplasma and Ureaplasma spp. in many conditions is due to a general unfamiliarity of physicians and microbiology laboratories with their fastidious growth requirements, leading to difficulty in their detection; their high prevalence in healthy persons; the poor design of research studies attempting to base association with disease on the mere presence of the organisms in the lower urogenital tract; the failure to consider multifactorial aspects of diseases; and considering these genital mycoplasmas only as a last resort. The situation is now changing because of a greater appreciation of the genital mycoplasmas as perinatal pathogens and improvements in laboratory detection, particularly with regard to the development of powerful molecular nucleic acid amplification tests. This review summarizes the epidemiology of genital mycoplasmas as causes of neonatal infections and premature birth; evidence linking ureaplasmas with bronchopulmonary dysplasia; recent changes in the taxonomy of the genus Ureaplasma; the neonatal host response to mycoplasma and ureaplasma infections; advances in laboratory detection, including molecular methods; and therapeutic considerations for treatment of systemic diseases.

FIG. 1.

Photomicrograph of lung (magnification 100×) collected at autopsy of a neonate who died at 6 days of age with pneumonia and sepsis due to Ureaplasma spp. (318). Antemortem cultures of blood, pleural fluid, and tracheal secretions and postmortem cultures of nasopharynx, conjunctiva, and brain were positive for Ureaplasma spp. in pure culture. There is extensive pneumonitis, mixed mononuclear and polymorphonuclear infiltrate with abundant macrophages, and fibrin deposition.

FIG. 2.

Proposed scheme for involvement of Ureaplasma spp. in the pathogenesis of bronchopulmonary dysplasia.

FIG. 3.

Colonies of Ureaplasma spp. growing on A8 agar after 48 h of incubation as they appear under 126× magnification using a stereomicroscope. Colonies are typically 15 to 30 μm in diameter and have a brownish appearance due to urease activity in the presence of the CaCl₂ indicator contained in the agar.

FIG. 4.

Colonies of Mycoplasma hominis growing on A8 agar after 72 h of incubation as they appear under 126× magnification using a stereomicroscope. Colonies are typically 200 to 300 μm in diameter and demonstrate a characteristic fried-egg appearance.