Current Understanding of Streptococcal Urinary Tract Infection

Group B streptococcus (GBS), also known as Streptococcus agalactiae is a Gram-positive, ┚hemolytic, chain-forming bacterium and a commensal within the genital tract flora in approximately 25% of healthy adult women (Campbell et al., 2000). The organism is a leading cause of serious infection in newborns, pregnant women, and older persons with chronic medical illness (Baker et al., Edwards&Baker, 2005). In neonates GBS infection most commonly causes pneumonia, meningitis, and sepsis. In addition to maternal cervicovaginal colonization and neonatal infection that can result from vertical transmission of GBS from mothers to their infants, the bacterium can also cause urinary tract infection (UTI). The spectrum of GBS UTI includes asymptomatic bacteriuria (ABU), cystitis, pyelonephritis, urethritis, and urosepsis (Bronsema et al., 1993, Edwards&Baker, 2005, Farley et al., 1993, Lefevre et al., 1991, McKenna et al., 2003, Munoz et al., 1992, Ulett et al., 2009). GBS ABU is particularly common among pregnant women, although those most at risk for cystitis due to GBS appear to be elderly individuals (Edwards&Baker, 2005, Falagas et al., 2006, Muller et al., 2006). In addition to acute and asymptomatic UTI other invasive diseases caused by GBS infection include skin infections, bacteraemia, pneumonia, arthritis, and endocarditis (Liston et al., 1979, Patil&Martin, 2010, Tissi et al., 1997, Trivalle et al., 1998). Thus, GBS is considered unique in terms of its ability to cause a spectrum of diseases in newborns and adult humans and its ability to colonize the genital tract of healthy women in a commensal-type manner. In contrast to GBS disease conditions resulting from neonatal infection, the clinical and microbiological features of GBS UTI and asymptomatic genital tract colonization are not well characterized. Moreover, the risk factors for the various diseases caused by GBS including UTI and the pathogenesis of the different diseases caused as a result of GBS infection are not well defined. Recent advances in the awareness, diagnosis and treatment of GBS infections, particularly in relation to vertical transmission and neonatal infection, have significantly reduced mortality in the newborn population. Establishment of preventative and treatment guidelines by the Centres for Disease Control (CDC) beginning in the 1990s has resulted in a reduction in mortality rates due to acute GBS infection in newborns from approximately 30-50% to 4–5% (Dermer et al., 2004). Guidelines for the prevention of GBS infections in newborns first published in 1992 and revised in 1997 include surveillance programs and administration of antibiotics during labour (intrapartum antibiotic chemoprophylaxis) (1992, 1997). Since the mid-1990s, most pregnant women in the United States have been screened for infection by