Mycoplasma pneumoniae from the Respiratory Tract and Beyond

Abstract

Mycoplasma pneumoniae is an important cause of respiratory tract infections in children as well as adults that can range in severity from mild to life-threatening. Over the past several years there has been much new information published concerning infections caused by this organism. New molecular-based tests for M. pneumoniae detection are now commercially available in the United States, and advances in molecular typing systems have enhanced understanding of the epidemiology of infections. More strains have had their entire genome sequences published, providing additional insights into pathogenic mechanisms. Clinically significant acquired macrolide resistance has emerged worldwide and is now complicating treatment. In vitro susceptibility testing methods have been standardized, and several new drugs that may be effective against this organism are undergoing development. This review focuses on the many new developments that have occurred over the past several years that enhance our understanding of this microbe, which is among the smallest bacterial pathogens but one of great clinical importance.

Keywords: Mycoplasma pneumoniae; macrolide resistance; pneumonia; respiratory pathogens.

FIG 1

Electron micrograph of Mycoplasma pneumoniae cells, demonstrating flask-shaped morphology and a prominent attachment tip structure.

FIG 2

Organization of the electron-dense core of the M. pneumoniae attachment organelle. Within the attachment organelle membrane, which is enriched for the transmembrane adhesin P1 and its binding partners, proteins B (P90) and C (P40) (106, 108), is an electron-dense core about 290 nm in length with a characteristic bend (134, 135). The core consists of several substructures. At the distal end, likely interacting with the transmembrane adhesin P30, which is restricted to the tip of the attachment organelle (114), is the terminal button, containing proteins P65 and HMW3 (118). The terminal button is in contact with the thick plate, containing protein HMW2 (118, 473). Parallel to the thick plate is the thin plate, which contains HMW1 (118). Adjacent to the plates at the end close to the cell body, and likely in contact with the chromosomal DNA (128), is the bowl complex, which contains proteins P200, TopJ, P41, and P24 and a protein that arises from an internal translational start within the gene coding for HMW2, called P28 or HMW2-S (118, 474). The bowl complex may be in contact with the membrane. Between the core and the attachment organelle membrane is an electron-lucent space of uncertain composition. This figure was generated with the assistance of Natalie Clines and Patrick Lane.