PATH 3100 Medical Microbiology - Streptococcus and Enterococcus - PDF

PATH 3100, Medical Microbiology Streptococcus and Enterococcus Dr. Elena Enioutina, M.D., Ph.D. Objectives Describe the classification of Streptococcus and Describe Enterococcus species based on hemolysis on sheep blood agar (alpha, beta, nonhemolytic)....

PATH 3100, Medical Microbiology Streptococcus and Enterococcus Dr. Elena Enioutina, M.D., Ph.D. Objectives Describe the classification of Streptococcus and Describe Enterococcus species based on hemolysis on sheep blood agar (alpha, beta, nonhemolytic). Associate the diseases caused by S. pyogenes, S. agalactiae, Associate S. pneumoniae, viridans group Streptococcus, group D Streptococcus, and Enterococcus species. Discuss the treatment of Streptococcal and Enterococcal Discuss infections Select the appropriate body site(s) from which the Name Streptococcus and Enterococcus species are considered normal flora as well as pathogens.  Streptococci Gram-positive Spherical bacteria (cocci) May occur in pairs or chains Non-motile Non-spore forming Facultative anaerobes Able to ferment sugars with the end product lactic acid Acid tolerant Group A streptococci have a hyaluronic acid capsule Catalase negative https://en.wikipedia.org/wiki/Enterococcus  Sources of Streptococci Many species are normal flora in upper respiratory and intestinal tracts Streptococci isolated from drinking water - fecal contamination. Food sources with high risk of Streptococcal contamination: milk and dairy products eggs steamed lobster potato salad, shrimp salad rice pudding Classification system of Streptococci is based on: Specific carbohydrate antigens Hemolysis on blood agar plates Biochemical properties  Classification of Streptococcus and Enterococcus Based on Hemolysis Alpha = green/brown zone (S. viridance, S. pneumoniae) Beta = clear, colorless zone (S. pyogenes, S. agalactia) Gamma = no hemolysis (Enterococci spp.) The hemolytic reaction can be https://microbenotes.com/hemolysis-of-streptococci/ visualized on blood agar plates  Alpha-Hemolytic Streptococci Alpha hemolytic Streptococcus does not lyse the red blood cells, but the hemoglobin is converted to methemoglobin Representative species: Streptococcus pneumoniae Streptococcus bovis (some species) Enterococcus Viridans Streptococcus American Society for Microbiology © 2016 Beta hemolytic Streptococci Beta hemolytic Streptococci complete lyse erythrocytes by the enzyme hemolysin. Beta-hemolytic Streptococci can be further divided into serological groups S. pyogenes (Group A) S. agalactiae (Group B) S. equisimilis (Group C) S. equi (Group C) S. anginosus (Group F) S. canis (Group G) Enterococcus rarely produce beta hemolysis American Society for Microbiology © 2016 Serologic grouping of Streptococcus spp. Species Lancefield Group Typical Hemolysis Streptococcus A Beta pyogenes S. agalactiae B Beta Alpha, Beta or Enterococcus faecalis D None S. bovis D Alpha or none S. pneumoniae Not groupable Alpha Viridans group Not groupable Alpha Streptolysin O Streptolysin S Beta-hemolysis ONLY where Beta-hemolysis visible around “stabbed” surface colonies (oxygen-labile) (oxygen-stable)  Non-Hemolytic or Gamma-Hemolytic Streptococci Non-hemolytic or gamma-hemolytic Streptococci rarely cause disease Enterococcus (Group D) S bovis group (Group D Strep) Streptococcus pyogenes Group A streptococcus Virulence factors Infections M protein Pharyngitis Hyaluronidase Otitis media Streptokinase Scarlet fever Streptolysin O Impetigo Cellulitis  “Strep Throat” Group A streptococcal pharyngitis is an acute pharyngitis that commonly presents with: Sudden-onset of sore throat Odynophagia (painful swallowing) Fever Sometimes, build-up of pus-filled pockets Other symptoms may include: headache abdominal pain nausea and vomiting Patients with group A strep pharyngitis typically do not have a cough, rhinorrhea, hoarseness, oral ulcers, or conjunctivitis. https://www.cdc.gov/groupastrep/diseases-hcp/  “Strep Throat” Epidemiology, 2018 Cases Deaths Age (years) No. (Rate*) No. (Rate*)