Lecture 7 – Gram Negative Cocci BIOL 2010 PDF

BIOL 2010 Lecture 7 – Gram Negative Cocci BAILEY AND SCOT T’S – CHAPTER 27, 39 DIAGNOSTIC MICROBIOLOGY – CHAPTER 17 In this lecture Explain the characteristics and pathogenesis of commonly encountered clinically significant microorganisms, including the most frequently isolated species by body...

BIOL 2010 Lecture 7 – Gram Negative Cocci BAILEY AND SCOT T’S – CHAPTER 27, 39 DIAGNOSTIC MICROBIOLOGY – CHAPTER 17 In this lecture Explain the characteristics and pathogenesis of commonly encountered clinically significant microorganisms, including the most frequently isolated species by body system Gram negative cocci (GNDC and Oxidase Positive) Neisseria Moraxella catarrhalis Discuss bacterial virulence, as related to these organisms ID methods for GNC Oxidase Sugar fermentation tests – we will utilize API NH strips Pathogenicity and Host Range for Neisseria and Moraxella Neisseria - Key Characteristics Most Neisseria spp. Aerobic Nonmotile Nonspore-forming Gram-negative diplococci (GNDC) Cytochrome oxidase and catalase - positive Most species have complex growth requirements Most species capnophilic and grow best in a moist environment What is a capnophile? Neisseria - Primary Human Pathogens N. gonorrhea (often called gonococci) Always pathogenic when present N. meningitidis (meningococci) May be present as a commensal inhabitant of upper respiratory tract of carriers May become an invasive pathogen Both pathogens Are fastidious Require enriched media for optimal recovery Pathogenic Neisseria - Virulence Factors Receptors for human transferrin Allow it to compete for iron Capsule Prevent phagocytosis Cell-outer membrane proteins Antigenic variation Causes production of useless antibodies Bind to pathogen and prevent binding of effective antibodies Pathogenic Neisseria - Virulence Factors (Cont.) Major outer membrane porin proteins Por A/B Effective against inflammatory response and complement killing Protein II (Opa) Facilitate adherence to phagocytic and epithelial cells Protein III Block host serum bactericidal action (IgG) Pathogenic Neisseria - Virulence Factors (Cont.) Pili Five distinct colony types T1 and T2 virulent T3 through T5 have no pili (avirulent) Functions to evade the immune system Aid in attachment to host tissues Help prevent phagocytosis Aid in exchange of genetic material from cell to cell (sex pili) Pathogenic Neisseria - Virulence Factors (Cont.) Lipooligosaccharide (LOS) or endotoxin Lipid A moiety and core LOS that differentiates it from the lipopolysaccharide (LPS) Immunoglobulin A (IgA) protease Cleaves IgA on mucosal surfaces Disseminated infections Anal canal Neisseria gonorrhoeae Neisseria gonorrhoeae is NOT normal flora Humans are the only natural host. Gonorrhea: meaning “flow of seed” (when urethral discharge was mistaken for semen) Also called clap, gonococcus, gonococci, GC Reportable disease known as gonorrhea Most commonly transmitted by sexual contact Asymptomatic carriers are reservoir for increased disease transmission Confirmed cases must be reported to Public Health Unit Men/women b/w ages of 20 and 24 N. gonorrhoeae – Infection in men Most often symptomatic (90% of the time) Causes acute urethritis, characterized by the abrupt onset of dysuria and a purulent urethral discharge Complications Epididymitis: inflammation of small coiled tube of testicle Urethral stricture: narrowing of the urethra Prostatitis: inflammation of the prostate gland N. gonorrhoeae: Infection in Women As many as 50% are asymptomatic. Endocervix and urethra is most common site of infection. Symptoms (if symptomatic) Dysuria Cervical discharge Lower abdominal pain Complications Pelvic inflammatory disease (PID) Sterility Ectopic pregnancy Perihepatitis (Fitz-Hugh-Curtis syndrome) Pelvic peritonitis N. gonorrhoeae – Non-STI Infections Blood-borne dissemination (