Sexually Transmitted Infections Flashcards
1
Q
How many new STIs each year?
A
~500 million
2
Q
What are the 6 factors for why STIs cause such a burden of disease?
A
- Often asymptomatic
- Stigma about getting tested/unaware
- Often incurable/long term infections
- Lack of education/disempowerment
- People unwilling to change behaviour/behaviours private
- People like having sex
3
Q
What are 2 important considerations to have towards STIs?
A
Generally fragile organisms involved
- survive poorly outside of the body
- transmission requires close contact and/or direct transmission of bodily fluids
May have multiple infections at once
- one infection may increase susceptibility to other infections
4
Q
If you have one STI already how does that impact the ability of transmission of HIV?
A
HIV transmission increases by 5-10 times
5
Q
What are the 6 most common bacterial causes of STIs?
A
Chlamydia trachomatis Neisseria gonorrhoea Treponema pallidum Haemophilus ducreyi Mycoplasma genitalium Gardnerella vaginalis
6
Q
What are the 4 most common viral causes of STIs?
A
HIV
HSP
HPV
HBV
7
Q
What is the most common fungal cause of STIs?
A
Candida albicans
8
Q
What is most common protozoan cause of STIs?
A
Trichomonas vaginalis
9
Q
Describe cervicitis and urethritis
A
Inflammation of cervix and urethra
Symptoms: dysuria, itching, +/- discharge
10
Q
Which organisms cause cervicitis and urethritis?
A
N. gonorrhoea
C. trachomatis
M. genitalium
HSV
11
Q
Describe vaginosis
A
Disrupted vaginal flora
Symptoms: unpleasant odour and/or vaginal discharge
12
Q
Which organisms cause vaginosis?
A
T. vaginalis
C. albicans
G. vaginalis
13
Q
Which organisms cause genital ulcers?
A
HSV
C. trachomatis
T. pallidum
H. ducreyi
14
Q
Describe pelvic inflammatory disease
A
Symptoms: chronic pelvic pain, fallopian tube damage, infertility
15
Q
Which organisms cause pelvic inflammatory disease?
A
C. trachomatis
N. gonorrhoea
G. vaginalis
Mycoplasma hominis
16
Q
Effects of HIV
A
> 40 million people infected
~1 million deaths/year
17
Q
Effects of HSV
A
> 500 million people infected
~20 million new infections/year
18
Q
Effects of HPV
A
~30 million infections/year
~250,000 cancer deaths/year
19
Q
Effects of HBV
A
> 200 million people infected
20
Q
Describe HIV
A
HIV-1 and HIV-2
Retrovirus of the lentivirus family
Encode a reverse transcriptase (pol gene)
21
Q
What is HIV the causative agent of?
A
Acquired Immune Deficiency Syndrome (AIDS)
22
Q
What does HIV infect?
A
CD4+ cells
- T helper cells, monocytes
- Dendritic cells
- Microglia
23
Q
How is HIV transmitted?
A
Transmitted in body fluids Non-sexual - blood - mother to child (vertical transmission) Sexual - male to male - male to female - female to male
24
Q
What is the most common transmission of HIV in Africa and Asia?
A
Female to male transmission
25
Describe HIV pathogenesis
```
Initial acute phase:
- Massive loss of CD4+ T cells
-> profoundly weakens the immune system
- Stage lasts for a few weeks
Second chronic phase:
- HIV replication checked by immune system
-> chronic immune activation
-> increasing threat of opportunistic infection
- Stage lasts for several years
```
26
Describe AIDS onset
A wide array of disease associated with HIV-induced immune compromise
Infections often in unusual tissues
27
How is HIV treated?
Treated with drugs that mostly target the reverse transcriptase step of HIV replication
- Nucleoside RT inhibitors (NRTIs)
- Non-nucleoside RT inhibitors (NNRTIs)
Also protease inhibitors and fusion inhibitors
Current use of combined therapy
- Highly active antiretroviral therapy (HAART)
28
Describe HSV
Caused by herpes simplex virus
| Double-stranded DNA virus, large genome
29
Describe HSV-1
Generally transmitted by saliva
Oral cold sores ~70% seroprevalence in adults
Accounts for 50% of new genital herpes causes in developed countries
30
Describe HSV-2
Generally transmitted by sexual contact
| Genital blisters/ulcers
31
How is HSV acquired?
Through close contact
- from an infected person shedding virus
- via skin contact or genital secretions
32
Describe HSV pathogenesis
HSV replicates initially in epithelial cells
- fluid filled blisters contain: detached epithelial cells, inflammatory cells, virions
The HSV penetrates dermis and enters sensory nerve axons
- enters latent stage, persistence for life
33
What are the steps involved in HSV pathogenesis?
1. Initial entry to epithelial cells
- lytic replication
2. enters sensory neuron
- travels to nucleus
3. periodic reactivation
- shedding back to epithelial cells
34
How many HSV infections are asymptomatic?
~70%
35
Describe primary lesions in HSV infection
They form 4-7 days after initial infection
Usually on penis, vulva (but may be intravaginal)
Symptoms: pain, itching, burning at site, dysuria
Overall symptoms: +/- fever, low grade headache, malaise, myalgias, inguinal lymphadenitis
36
How long do lesions from HSV take to heal?
3-4 weeks
37
How common are recurrent infections in HSV?
70-90% have recurrence within 1 year
| Less severe than initial episode
38
Compare and contrast primary lesions and recurrent lesions
```
Primary lesions
- multiple, widespread lesions at different stages
Recurrent lesions
- typically grouped
- identical stages of development
```
39
What are serious consequences of neonatal HSV?
Skin and eye disease
Cognitive impairment
Organ dysfunction
Death
40
How to prevent neonatal HSV from a mother with lesions?
Elective caesar
41
How do we diagnose HSV?
Initial diagnosis through clinical symptoms
Confirm by laboratory tests
- swab base of genital lesion, vesicle fluid
- send swab in viral culture medium
42
What are 3 methods of diagnosing HSV?
Viral culture
- poor sensitivity, HSV in <50% of recurrent lesions
PCR
- faster and ~4-times more sensitive than culture
HSV antigen detection
- Type specific IgG (HSV-1, -2) against glycoproteinG
43
What types of drugs are given for HSV infection and what do they do?
Antiviral drugs which reduce severity of symptoms and time to resolve
Give decreased viral shedding
44
What are 3 drugs that can be given for HSV infection?
Acyclovir, Valacyclovir, Famciclovir
| Orally or intravenously
45
How do we prevent the transmission of HSV?
- Abstain from sex if lesions present
| - Use condoms consistently at other times
46
Describe HPV
Double-stranded DNA virus
8kb genome
8 genes
47
How many distinct types of HPV are there?
120
~40 types infect genital tract
~80% of females will acquire genital HPV infection by the age of 50
48
What cancers is HPV linked to?
```
Cervical
Anal
Vulvar
Penile
However, whilst HPV infection is necessary it is not sufficient
```
49
Which HPV strains show strong links to cancer?
HPV-16 and -18 found in 64-79% of cervical cancers
| HPV-31 and -45 also "high risk"
50
How is HPV transmitted?
Via skin to skin contact
51
Describe the pathogenesis of HPV
Enters squamous epithelium cells via microabrasions
- infection often resolved naturally
Viral proteins E6 and E7 disrupt cell division
- infected cells outgrow non-infected cells; resulting in warts and tumours
- may integrate into genome
52
How is HPV diagnosed?
Clinical observation of lesions
Subclinical diagnosis: dilute acetic acid causes whitening of warts
Cytology
- Papnicolaou (Pap) smear test
- identification of cervical intraepithelial neoplasia (CIN) and early cervical cancers
53
How do we treat HPV?
Cosmetic, non-specific, controls growth
| - Liquid nitrogen, excision, causative agents
54
How do we prevent HPV?
Preventative vaccine (Gardasil)
- L1 virus structural protein
- Virus like particles
- nonavalent vaccine
55
Which types of HPV are targeted by Gardasil?
6, 11, 16, 18, 31, 33, 45, 52, 58
56
Effects of Chlamydia trachomatis
Chlamydia
| ~130 million infections/year
57
Effects of Neisseria gonorrhoea
Gonorrhoea
| ~78 million infections/year
58
Effects of Treponema pallidum
Syphilis
| ~6 million infections/year
59
Effects of Haemophilus ducreyi
Chancroid
60
What type of pathogen is Chlamydia trachomatis?
Obligate intracellular bacterial pathogen
| ATP parasite
61
What type of infection can C. trachomatis cause?
persistent, chronic infections
62
What are the different serotypes of C. trachomatis and what type of disease do they cause?
A, B, C = serious eye disease trachoma
D-K = cause genital infection (chlamydia)
L1, L2, L3 cause the systemic STI lymphogranuloma venereum (infection in draining lymph nodes)
63
How has the incidence of chlamydial infection changed since 2001.
Increased ~20% per year since 2001
64
What are the steps in the C. trachomatis lifecycle?
1. Attachment: Elementary body attaches to specific receptor on host cell
2. Entry: parasite-specified endocytosis
3. Differentiation to Reticulate body
4. Multiplication of Reticulate body
5. Differentiation of Elementary body
6. Release: Elementary body progeny spread to adjacent cells
65
Describe the Elementary body in C. trachomatis infection
Adapted for extracellular survival
| Is metabolically inactive but stable extracellularly
66
Describe the Reticulate body in C. trachomatis infection
Adapted for intracellular lifecycle
67
Describe the symptoms of C. trachomatis infection
Symptoms observed 7-14 days after infection
| Watery/mucopurulent discharge, dysuria
68
What are some complications of C. trachomatis infection?
```
Chlamydial cervicitis and urethritis
Both males and females may be asymptomatic
Female complications:
- Pelvic inflammatory disease
- Chronic pain
- Ectopic pregnancy
- Infertility
Complications rare in males
```
69
How is C. trachomatis infection diagnosed?
```
Its symptoms do not differentiate it from other STIs, therefore we must rely on the following:
Cell culture
- 100% specific, 48-72 hours
Direct antigen detection
- ELISA
- Direct immunofluorescence (low sensitivity)
PCR
- can use urine samples
- high sensitivity, fast 2-4 hours
```
70
How is C. trachomatis infection treated?
Azythromycin - single dose
| Tetracycline - doxycycline (10-day course)
71
Are co-infections likely with C. trachomatis infection?
They occur in 5% of N. gonorrhoea infected patients
72
Describe Neisseria gonorrhoea
Gram-negative bacteria
Only infects humans
Survives poorly in the environment
73
What is N. gonorrhoea transmission called when transmitted vertically during vaginal delivery?
Ophthamia neonatorum
74
Describe the pathogenesis of N. gonorrhoea
1. Site of entry generally vagina or urethral mucosa of penis (also throat and rectal mucosa)
2. Initial attachment facilitated by pili
- high antigenic variation
- outer membrane proteins (e.g. Opa) also important
3. Invasion of non-ciliated epithelial cells
- replication in vacuole
- release through basement membrane
4. Damage to host results from the host inflammaotry response
75
What are the symptoms of N. gonorrhoea infection?
Symptoms observed within 2-7 days after initial infection
- vaginal or urethral (male) discharge
- Dysuria
Females often asymptomatic
76
What are some complications of N. gonorrhoea?
Males = rare
Females:
- Pelvic inflammatory disease (10-20% of untreated cases)
- Chronic pelvic pain
- Fallopian tube damage and infertility
- Bloodstream infections (1-3% of cases) (septic arthritis)
77
How is N. gonorrhoea infection diagnosed?
```
Purulent discharge not reliably distinguishable from chlamydial discharge
Microscopy and culture:
- Smear of urethral discharge
- Gram-negative intracellular diplococci
- Organism very sensitive to drying
```
78
How is N. gonorrhoea infection treated?
Ceftriaxone IM with azithromycin
Single treatment therapy
Ciprofloxacin or spectinomycin also useful
79
Is N. gonorrhoea resistant to any antibiotics?
Yes, shows significant resistance to penicillins and increasing resistance to fluoroquinolones
80
Is N. gonorrhoea infection notifiable?
Yes, must be notified to the Health Department and partner must be notified
81
Does co-infection with N. gonorrhoea happen?
Yes, likely with chlamydia
82
What pathogen causes Syphilis?
Treponema pallidum
83
What are the 4 stages of T. pallidum infection?
Primary
Secondary
Latent
Tertiary: neurosyphilis, cardiovascular syphilis, congenital
84
How is T. pallidum transmitted?
Sexual contact
- 15-30% risk of infection after sex with infected partner
Vertical transmission: mother to child in the placenta
85
What is the incubation period of T. pallidum infection?
9-90 days
| average is 2-4 weeks
86
What is primary syphilis?
Lesions
Women: cervix, labia, urethra
Men: Penis, ano-rectal (MSM)
Lesions at extragenital sites uncommon (2-7%): fingers, lips, nipples
87
What is secondary syphilis?
```
Systemic spread of treponemes
7-10 weeks after primary lesion
- generally a skin rash
- highly infectious
Resolves in ~3 months
```
88
What is tertiary syphilis?
In 3-30 years, 30% develop tertiary syphilis
Cell-mediated response
- Soft tissue destruction and gummas; granulomas resulting from chronic inflammation
- Cardiovascular; leaking of aortic valve
- Neurosyphilis; dementia and psychotic symptoms
89
How is T. pallidum infection diagnosed?
Microscopy and serology
- No in vitro culture (culture in rabbits very slow)
Microscopy
- exudate from primary chancre (very infectious)
Non-treponemal tests
Treponemal tests
90
How do non-treponemal tests diagnose T. pallidum?
Detect antibodies against cardiolipin (host membrane component-host damage) usually present in syphilis patients
RPR - Rapid Plasma Reagin test
VDRL - Venereal Disease Research Laboratory test
Low sensitivity (false negatives) and specificity (false positives)
91
What does low sensitivity mean?
False negatives
92
What does low specificity mean?
False positives
93
How do Treponemal tests diagnose T. pallidum?
Enzyme immunoassay (ELISA for patient antibody)
TPHA - T. pallidum HaemAgglutination assay
FTA-ABS - Fluorescent Treponemal Antibody - Absorbed Test
High Specificity
94
How is T. pallidum infection treated?
Historically:
- Heavy metals: mercury, arsenic compounds (Neosalvarsan)
- Malaria-induced fever (esp. for neurosyphilis)
Modern:
- Penicillin - high dose
-> doxycycline/Erythromycin if allergic
95
How is T. pallidum infection prevented?
Safe sex
| Secondary, tertiary and congenital syphilis prevention require early diagnosis and adequate treatment
96
What pathogen causes Trichomoniasis?
T. vaginalis
97
What is T. vaginalis?
Flagellated protozoan
98
What are the symptoms of Trichomoniasis?
```
Women:
- Cervicitis
- Malodorous profuse frothy vaginal discharge
- Itchy/soreness
~50% women are asymptomatic
Most men are asymptomatic
- unusually dysuria and penile discharge
```
99
What is the route of transmission of T. vaginalis?
Vaginal, oral or anal sexual intercourse
100
How is T. vaginalis infection diagnosed?
PCR on first pass urine or high vaginal swab
101
How is T. vaginalis infection treated?
Metronidazole (flagyl)
- 2g orally once or 400mg for 5 days
or Tinidazole
102
What is Candida albicans?
Diploid fungus
| Normal oral, gut and vaginal flora
103
What infection does Candida albicans cause?
overgrowth -> vaginal candidiasis (thrush)
104
What are the symptoms of C. albicans infection?
Irritation
Inflammation
Cheesy discharge
+/- dysuria
105
What are predisposing factors of C. albicans infection?
Hormone changes (menses, pregnancy)
Diabetes
Reduced cell-mediated immunity
Antibiotic treatment
106
In who is C. albicans most likely to cause systemic infection?
```
AIDS patients
Transplant patients
Cancer patients
Burns patients
Anyone with an immunodeficiency
```
107
How is C. albicans infection treated?
Topical or oral antifungal
