Bacterial STIs Flashcards
Name the two neisseria species commonly involved in infection and their characteristics
N. gonnorrhoeae, N meningitidis
Aerobis, gram-negative diplococci that are catalase and oxidase positive
What differentiates gonnorrhoea from other neisseria species?
Won’t grow on SBA
Why can’t you make a gonnococcus diagnosis from a gram stain alone?
Because all women are colonized by non-pathogenic neisseria species
What is the metabolic difference between N. gonnorhoeae and meningitidis?
N.g. only ferments glucose, N.m. ferments glucose and maltose
What are the 4 risk factors for gonnorhoeae?
Under 25 years old, homeless/street youth, new sexual partner or more than 2 a year, non-barrier contraception
What are 5 clinical manisfestations of gonnorrhoea?
Acute urethritis or cervicitis, ano-rectal or phayngeal infection, pelvic inflammatory disease, septic arthritis, copious urethral discharge
What are the transmission risks for males and females?
20% for female to male
50% for male to female
What are the 2 virulence factors of gonnorhoea and their functions
1) Pili: adherence and inhibits killing by neutrophils
2) Outer membrane proteins: adhesion, endotoxic activity
Describe the 3 basic steps of gonnorrhoeal pathogenesis
1) infection mainly of columnar or cuboidal epithelium
2) vigorous neutrophil response causing sloughing of epithelium and exudation of pus (bacteria appear intracellular in neutrophils on gram stain)
3) Infection may spread to proximal genital tract, bloodstream or joints
Describe the difference between sensitivity and specificity in testing for the infectious agent
Sensitivity is the percentage of sick people correctly identified as having the condition
Specificity is the percentage of healthy people who are correctly identified as not having the condition
What are the 2 cultural/diagnostic methods used to detect gonnorhoea and the types of specimens required from male and females for each?
1) Culture on a very nutritious medium containing antibiotics such as TMA, MLA, NYCA. Requires urethral swabs from men and cervical swabs from women
2) PCR, requires vaginal swabs from women and urine samples from men
What is the only drug class recommended for treatment of N. gonnorrhoeae infections? What two drugs of that class are used?
Cephalosporins.
800 mg of Cefixime or
250 mg of ceftriaxone
Describe the basic pathogenesis of chlamydia
Infection of host cell by the elementary body, differentiation into the reticular body and replication by binary fission, EB release from host cell
What are the clinical manifestations of chlamydia in men and women?
Incubation is between 7 and 21 days. 25% of men are asymptomatic.
Urethritis in men.
Cervicitis, PID and urethritis in women: 80% of women are asymptomatic for cervicitis
What is the best diagnostic method for chlamydia and what are the preferred specimens for men and women?
PCR.
Males: urine
Females: vaginal swabs
