WEEK 9 - Sexually Transmitted Disease (STD / STI) Flashcards
STIs BACKGROUND INFO
- STI cases (esp. gonorrhoea and syphilis) are ↑ due to diagnostic tests improving and population ↑
- Chlamydia cases are stable
- STIs affect more young sexually active
List 5 STIs
- Gonorrhoea
- Syphilis
- Chlamydia
- Genital Warts
- Monkeypox
Ghonorrhoea INFO
inc. Cause, Transmission, Where it affects
CAUSE:
- Neisseria gonorrohoea
- a gram neagtive cocci bacteria
- is an obligate human pathogen
TRANSMISSION:
- Direct mucosal contact
- Vertical (mother to baby)
- conjuctiva seen mainly in natural birth babies as they pass through reproductive tract
WHERE IT AFFECTS:
- Mucosa of the cervical canal
- Anal canal
- Eyes (conjunctiva)
- Pharynx (throat)
OTHER INFO:
- Requires a human host to survive, has poor envrironmental survival
Ghonorrhoea Pathogenesis
N.g = Neisseria gonorrhoea
- N.g adheres to CCAM on host epithelium via TYPE 4 PILI and OPACITY PROTEINS
- Attachment leads to formation of micro N.g colonies on host surface
- competition with resisiding microbiota
- capable of host epithelial invasion via transcytosis
- N.g release peptidoglycan, LOS and outer membrane vesicles (OMVs) from its cell wall
- Triggers innate immunity = activation / recruitment of macrophages, neutrophils, cytokines, chemokines, dendritic cells, NOD receptors
- inflammatory cascade
- inflammatory transcription factors
- Neutrophils recruited to site of N.g infection leads to uptake
- i.e. neutrophils phagocytose N.g
- N.g like surviving in neutrophils and macrophages
- Purulent exudate is released = symptoms of gonorrhoea infection
NOTE:
- N.g does NOT have a capsule or produce exotoxins
- like N.meningitis
- Symptoms are linked to hsot innate immune activation
How does gonorrhoea invade the immune response
- Mimicry
- N.g coats itself in host proteins
- mimics host = immune pathway does NOT recognise it as foreign
- Inactivates complement cascade
- N.g uses factor 1 to cleave complement proteins e.g. C3b
Ghonorrhoea Symptoms
Males:
- Purulent discharge / exudate from penis
- Dysuria (pain / burning when urinating)
- Testicular pain
Anal and pharynx infections are usually asymptomatic
Females:
- ↑ vaginal discharge
- non specific = can be mistaken for other conditions e.g. yeast infection, vaginosis
- Lower abdominal pain
- Pelvic inflammatory disease
- Intermenstrual bleeding
Anal and pharynx infections are usually asymptomatic
NOTE:
- Symptoms are linked to host innate immune activation
- NEED sufficent neutrophil influx to site
List the 2 ghonorrhoea treatments
- Ciprofloxacin 500mg single dose
- if N.g susceptibility is KNOWN - Ceftriaxone 1g IM single dose
- if N.g susceptibility is UNKNOWN
PROCESS
1. REFER to GUM clinic or local sexual health service
2. Ideally take a culture swab or urine sample before starting antibiotic treatment
3. Start ANTIBIOTICS
Systemic gonorrhoea requires hospitalisation
Explain the MoA of Ciprofloxacin
Ghonorrhoea treatment
A Fluoroquinolone
- Targets bacterial DNA gyrase and topoisomerase
- minimses eukaryotic toxicity as it has low affinity for mammalian DNA gyrase
- Prevents DNA supercoiling and replication
Is given if N.g susceptibility is KNOWN
Explain the MoA of Ceftriaxone
Ghonorrhoea treatment
A Beta-lactam antibioitic
- PBP binds to antibiotic, inhbiting peptidoglycan formation
- Prevents PBP crosslinking glycan strains in bacteria cell wall = cell wall integrity is compromised
- Cell wall can’t survive osmotic pressure = celld eath
Is given if N.g susceptibility is UNKNOWN
Is a 3rd gen. cephlasporin
Syphilis INFO
inc. Cause, Transmission, 3 Stages
CAUSE:
- Treponema pallidum (bacterium)
- has long latent period (disease progresses in stages over 10 years)
- obligate human pathogen
TRANSMISSION:
- Direct sexual contact
- Vertical (during pregnancy)
- infected pregnant women have many complications e.g. still birth, death of baby, low birth weight, poor feeding
NOTE: Have a transmission risk for first 4 years of infection
STAGES:
1. Primary
2. Secondary
3. Tertiary
Syphilis Symtpoms in each stage
3 stages
Primary:
- Single ulcer OR multiple lesions
- on genitals / places involved in sexual contact e.g. tongue, hands
- Resolves spontaneously (~3 weeks)
Secondary:
- Fever
- Headache
- Flat, raised rash or lesions (on hands / feet soles)
- Symptom resolution BUT enter latent phase (= asymptomatic)
- still infectious for first 2 years
- can relapse to secondary syphilis
Tertiary (not common):
- Severe lesions
- Cardiac and neurological conditions
- Developed from secondary syphilis
Syphilis Treatment
Benzathine benzylpenicillin (IM injection)
DOSE: depends on stage
- Early stage = single dose
- Later stage = weekly dose for 3 weeks
PROCESS:
1. REFER to GUM clinic
2. GUM specialist conduct lab diagnostics + sexual health screening
3. Antibiotics are started
Chlamydia INFO
inc. Cause, Transmission, Where it affects
CAUSE:
- Chlamydia trachomatis
- an atypical, intracellular pathogen
- has a unique lifecycle - alternates between replicating and non-replictaing form
TRANSMISSION
- Sexual contact
WHERE IT AFFECTS
- Genitals
- Conjuctiva
- Rectum
- Nasopharynx
NOTE:
Intracellular = endocytosed into cell
Explain the Lifecycle of Chlamydia
Alternates between replicating and non-replictaing form
Replicating Form (reticulate body):
- Non-infectious
- Replicates evert 2-3 hours and has an incubation period of 7 to 21 days
- After replication is done shifts to elementary body
Non-replicating Form (elementary body):
- Infectious
- Elementary body germinates inside host cell + interacts with glycogen
- After glycogen interaction it moves into reticulate body
Chlamydia Symtpoms
Commonly Asymptomatic
Men:
- Inflammation of urethra
- Discharge from penis
- Pain / burning when urinating
Women:
- Inflammation of cervix
- Vaginal discharge
- Pain when urinating
- Pelvic tenderness
- Intermenstrual bleeding
