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Streptococcus agalactiae: Characteristics, Epidemiology, and Clinical Impact

Streptococcus agalactiae, the only species carrying Group B antigen, can lead to severe infections in newborns, pregnant women, and compromised individuals. Learn about its physiology, spread, diagnosis, and treatment options.

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Streptococcus agalactiae: Characteristics, Epidemiology, and Clinical Impact

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  1. Streptococcus agalactiae • Only species that carries the group B antigen. • Initially recognized to cause puerperal sepsis (childbed fever ) • Now this is uncommon • Septicemia, pneumonia, and meningitis in newborns • Other infections (Box 23-3)

  2. Streptococcus agalactiae • Physiology and Structure • Gram (+) streptococci • Facultative anaerobe • β –hemolytic (1-2% are nonhemolytic) • Classified by B antigen

  3. Streptococcus agalactiae • Epidemiology • Site of colonization: • Lower gastrointestinal tract • Genitourinary tract • 10% to 30% of pregnant women are carriers. • 60% of infants born to colonized mothers become infected with mothers’ organisms. • This can lead to pneumonia, bacteremia, and meningitis

  4. Streptococcus agalactiae • Epidemiology cont. • Infections in men and non-pregnant women: • Primarily skin and soft-tissue • Bacteremia • Urosepsis (UTI with bacteremia) • Pneumonia

  5. Streptococcus agalactiae • Epidemiology cont. • Conditions that predispose disease in adults: • Diabetes mellitus • Cancer • Alcoholism

  6. Streptococcus agalactiae • Clinical Diseases • Early-Onset Neonatal Disease • Disease acquired in utero or at birth, symptoms appear within the first week of life. • Diseases: • Bactermia • Pneumonia • Meningitis • Pulmonary problems observed in most infants • Meningeal involvement may be non-apparent at first • CSF examination is a must

  7. Streptococcus agalactiae • 5% mortality rate • 15% to 30% of meningitis survivors have neurological problems including: • Blindness • Deafness • Severe mental retardation • Late-Onset (1 week to 3 months) • Source of disease: • Mother • Other infants • Bacteremia with meningitis

  8. Streptococcus agalactiae • Clinical Diseases cont. • Pregnant women – UTI’s • Infections in Men and Non-pregnant women • Generally older and/or compromised immunity • Common infections • Bacteremia • Pneumonia • Bone and joint infections • Skin and soft-tissue infections • Mortality is higher in this group 15% to 32%.

  9. Streptococcus agalactiae • Diagnosis • Culturing • Antigen Detection • DNA (PCR) test • Treatment • Penicillin G • Pregnant women are give IV 4 hours before delivery

  10. Viridans Streptococci • Viridans • Heterogeneous collection of α-hemolytic and nonhemolytic streptococci • Name • Viridis is Latin for “green” • 20 species identified and placed in 6 groups • Table 23-5 • Viridans cultures: • Require complex media • Supplemented with blood products • Incubation in 5% to 10% CO2

  11. Viridans Streptococci • Viridans • Colonization • Oropharynx • Gastrointestinal tract • Genitourinary tract • Rarely found on skin • Sebum is toxic to viridans • Common infections • Dental caries • Subacute endocarditis • http://heart.healthcentersonline.com/infectionsinjuries/endocarditis.cfm

  12. Viridans Streptococci • Viridans • Common infections cont. • Suppurative intraabdominal infections • Prevention and Control • Susceptible to Penicillin, (most strains) • Moderately and highly resistant strains have become more common

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