21 - Neisseria gonorrhoeae Flashcards
Neisseria gonorrhoeae in men
- Colonises the urethra
- Incubation period: 1 to 7 days
- Transmitted only by intimate sexual contact
- 95% show symptoms of acute infection
Symptoms in men
Dysuria, urethral discharge
Complications in men
- Epididymitis
- Urethral stricture (narrowing of the urethra)
- Prostatitis
Treatment in men
Antibiotics
Neisseria gonorrhoeae in woman
- Colonises the endocervix
- 20% to 80% are asymptomatic
Symptoms (if symptomatic) in woman
- Abdominal pain
- Vaginal bleeding
- Fever
Complications in woman
- Pelvic inflammatory disease (PID)
- Ascending infection into the fallopian tubes (Sterility, Ectopic pregnancy)
- Perihepatitis
Treatment in woman
Antibiotics do not prevent PID but do prevent transmission
Other clinical manifestations
- Disseminated gonococcal disease
- Gonococcal arthritis
- Ophthalmia neonatorum (infection in the eye) during delivery
- Pharyngitis
Multi drug resistance
Decreased susceptibility to one currently recommended therapy (cephalosporin OR azithromycin) PLUS
resistance to at least two other antimicrobials (penicillin, tetracycline, erythromycin, ciprofloxacin)
Lab diagnosis
- Plate within 6 hours onto Thayer Martin (MTM) agar
- Microscopy (gram -ve diplococci)
Extreme drug resistance
Decreased susceptibility to two currently recommended therapies (cephalosporin AND azithromycin) PLUS resistance to at least two other antimicrobials (penicillin, tetracycline, erythromycin, ciprofloxacin)
Antimicrobial resistance
Driven by point mutation and acquisition of resistance
markers by natural transformation
Mechanisms of resistance to Sulphonamides
- Over-synthesis of para-aminobenzoic acid
- Chromosomal mutations in the dihydropteroate synthetase gene to prevent binding by sulphonamides
Mechanism of resistance to Quinolones
Chromosomal mutations in the gyrA and parC genes (DNA replication machinery)
Mechanisms of resistance to Macrolides
- Chromosomal mutations in the 23S rRNA rrl to prevent antibiotic binding to ribosome
- Mutations in the mtrR and mtrR gene to increase efflux from the MtrCDE pump
MtrR
- Repressor of the transcription of the multidrug efflux pump, MtrCDE
- Mutation results in high constitutive expression of the pump thus increased drug resistance
MtrCDE
ABC transporter for the removal of drugs
Mechanisms of resistance to tetracyclines
- Chromosomal mutations in the rpsJ (30S ribosomal protein S19) to exclude binding to ribosome
- penB to exclude antibiotic
- mtrR promoter and gene to efflux antibiotic
- Plasmid-mediated production of the TetM protein
Mechanisms of resistance to spectinomycin
- Chromosomal mutations in the spc locus
- Plasmid-mediated resistance (very rare)
- Not recommended as a first-line agent due to the ease with which resistance may occur
Mechanisms of resistance to aminoglycosides
Chromosomal mutations in the kan gene
Do gonococcal infections increase
transmission of other STIs
Yes, in particular HIV.
Why are vaccines difficult to design
- Neisseria gonorrhoeae is naturally transformable
- High antigenic variation and genetic drift
EptA
Enzyme that adds phosphoethanolamine to lipid A headgroups in the periplasm of gram negative bacteria
