STDs and Microbial conditions Flashcards
What is a Commensal micro-organism?
A micro-organism that derives food or other benefits from another organism without hurting or helping it.
What is a Pathogen?
A micro-organism that can cause disease.
What is an infection?
The invasion of all or part of the body by a micro-organism.
If an infection has no symptoms what is it termed?
Sun-clinical
If an infection has symptoms what is it termed?
Clinical
What is a Sexually transmissible microbe?
A virus, bacteria or protozoan which can be spread by sexual contact:
- Commensal
- Pathogen
What is a Sexually transmitted infection (STI)?
An infection by a pathogen which is sexually transmissible and which is unlikely to be transmitted by non-sexual means:
- Neisseria gonorrhoeae
- HPV type 6
What is a Sexually transmitted disease (STD)?
A disorder of structure or function caused by a sexually transmitted pathogen:
- Pelvic inflammatory disease
- Genital warts
What are the Venereal diseases?
> Syphilis (Treponema pallidum pallidum)
> Gonorrhoea (Neisseria gonorrhoea)
> Chancroid (Haemophilus ducreyi)
Examples of bacterial “Sexually transmitted”
organisms in the UK?
Bacteria:
- Chlamydia trachomatis
- Klebsiella granulomatis
- Mycoplasma genitalium
Examples of viruses “Sexually transmitted”
organisms in the UK?
Viruses:
- HSV
- HIV
- HPV
- Molluscum contagiosum virus
Examples of parasites “Sexually transmitted”
organisms in the UK?
Parasites:
- Pthirus pubis
- Sarcoptes scabei
- Trichomonas vaginalis
Characteristics of STIs?
> Transmissible = Must treat sexual partners as well
> Often asymptomatic
> All are manageable but not all are curable
> Avoidable
What does sexually transmitted mean?
> Transmitted by sexual contact.
> But, there are a lot of different types of sexual contact.
Which STI require genital contact only?
Genital contact only:
- Pubic lice (Pthirus pubis)
- Scabies (Sarcoptes scabeii)
- Warts (human papilloma virus types 6 &11)
- Herpes (Herpes Simplex Virus types 1 & 2)
Why are STIs important?
1) They cause morbidity and can kill:
- Unpleasant symptoms
- Psychological issues
2) They’re a drain on resources:
- Infertility costs a lot
- HIV treatment is costly
- Time off work
3) They’re common
Ro=BcD
Ro = reproductive number (average number of infections produced) = likelihood of transmission
B = likelihood of transmission
c = rate of acquiring new partners
D = duration of infectivity
If Ro >1 then epidemic is sustained
If Ro <1 then epidemic reduces
If Ro is >1 what does this mean?
If Ro >1 then epidemic is sustained
If Ro is <1 what does this mean?
If Ro <1 then epidemic reduces
Which vaccination is recommended at ages 11 or 12, why?
HPV vaccination is recommended as it can drastically reduce the risk of future HPV infection and therefore cancer
NATSAL study (National survey of sexual attitudes and lifestyle) - what has it told us about sex and infection rates?
1) Increased numbers of partners/person
2) Increased concurrent partners
3) More people having anal sex
4) More men reporting sex with men (also increased condom usage).
Why my rates of STIs be increasing?
1) Change in the number of cases
2) Change in the number of diagnoses but no change in cases
Why my rates of STIs be increasing - number of cases?
1) Increased numbers of partners/person
2) Increased concurrent partners
3) More people having anal sex
4) More men reporting sex with men (also increased condom usage)
5) Dating apps
6) Alcohol consumption, “beer googles”
Why my rates of STIs be increasing - number of diagnosis?
1) More people asking for tests
2) More clinicians considering STIs and testing for them.
3) Better tests e.g. Nucleic acid amplification tests versus enzyme immunoassays for chlamydia
What is the idea around “Cores” and assortative mixing and STIs?
> Some people have sex with people like them (similar lifestyle – eg IDU, same ethnicity)
> Leads to high prevalence within a subpopulation (core) but limited spread through the wider community.
- Syphilis in people who exchange sex for drugs
- Lymphogranuloma venereum or HCV in HIV+ve MSM
What is the idea around “chains” and random mixing and STIs?
> Some ‘cores’ are very big – eg heterosexual men and women.
> Random mixing leads to lower prevalence but wider dissemination along ‘chains’.
> Most people have few sexual contacts over a given period of time and so chains are quite short
> If this was generalised, STI epidemics wouldn’t be sustained
What are the important aspect of a STI history?
1) A good history:
- Presenting complaint
- Direct questions
- History
- Past medical history
- Ginae history
2) Sexual history:
- When did you last have sexual contact?
- Casual contact vs ‘regular’ partner?
- How long were you going out with them for?
- Were they male or female?
- Asking about nature of sex act sometimes useful
anxiety about a specific incident
- If it’s going to alter where you swab from eg MSM
- Did you use condoms?
- Other contraception used
- Nationality of contact
3) Risk assessment (Man):
- Have you ever had sexual contact with a man?
- Have you ever injected drugs?
- Sexual contact with anyone who’s injected drugs?
- Someone from outside the UK? (clarify)
- Medical treatment outside UK? (clarify)
- Involvement with sex industry. (had sex with prostitute)
What are the important aspect of a STI history - Sexual history?
Sexual history:
- When did you last have sexual contact?
- Casual contact vs ‘regular’ partner?
- How long were you going out with them for?
- Were they male or female?
- Asking about nature of sex act sometimes useful
anxiety about a specific incident
- If it’s going to alter where you swab from eg MSM
- Did you use condoms?
- Other contraception used
- Nationality of contact
4) Partner notification (Contact tracing):
- Patient tells contacts “client referral”
- NHS tells contact “provider referral”
5) Offer/recommend further testing:
- Most STIs are risk factors for HIV acquisition and transmission.
- If someone has one STI (eg chlamydia) they could have another (eg HIV)
6) Health promotion:
- Condoms prevent transmission of some STIs -
Eg HIV, chlamydia, gonorrhoea
- Condoms aren’t very good at preventing transmission of other STIs
eg herpes and warts
- Oral sex carries risks too
> Not as great as vaginal or anal sex
> fellatio more than cunnilingus
- Alcohol and other drugs
What are the important aspect of a STI history - Risk assessment?
Risk assessment (Man):
- Have you ever had sexual contact with a man? - Have you ever injected drugs? - Sexual contact with anyone who’s injected drugs? - Someone from outside the UK? (clarify) - Medical treatment outside UK? (clarify) - Involvement with sex industry. (had sex with prostitute)
What are the important aspect of a STI history - Partner notification?
Partner notification (Contact tracing):
- Patient tells contacts “client referral”
- NHS tells contact “provider referral”
What are the important aspect of a STI history - Health promotion?
Health promotion:
1) Condoms prevent transmission of some STIs -
Eg HIV, chlamydia, gonorrhoea
2) Condoms aren’t very good at preventing transmission of other STIs
eg herpes and warts
3) Oral sex carries risks too
> Not as great as vaginal or anal sex
> fellatio more than cunnilingus
4) Alcohol and other drugs
What are the important aspect of a STI history - Offer/recommend further testing?
Offer/recommend further testing:
- Most STIs are risk factors for HIV acquisition and transmission.
- If someone has one STI (eg chlamydia) they could have another (eg HIV)
What is the difference between an STI and STD?
An STI is the infection, eg Human Papilloma Virus, whereas an STD is the disease(s) it causes; eg warts.
What causes Gonnorrhoea?
Neisseria gonorrhoeae
Symptoms of gonorrhoea in males?
1) 10% of males have no symptoms though might have clinical signs if examined.
2) Thick, profuse yellow discharge
3) Dysuria.
4) Rectal and pharyngeal infection often asymptomatic.
Symptoms of gonorrhoea in females?
1) >50% have no symptoms.
2) Vaginal discharge
3) Dysuria
4) Intermenstrual/post-coital bleeding
Complications of gonorrhoea?
Male = Epididymitis
Female:
- Pelvic inflammatory disease
- Bartholin’s abscess. [Gonococcal ophthalmia neonatorum.]
Both:
- Acute monoarthritis usually elbow or shoulder.
- Disseminated
Gonococcal Infection: skin lesions - pustular with halo. (both v rare).
What is the incubation period of Neisseria gonnorheoae?
Average 5 to 6 days. Range 2 days to 2 weeks (if get symptoms at all)
Number of new cases of gonnorheoa in grampian each year?
Approx 150 cases/yr in Grampian. Much less common than chlamydia. Most cases are in men, often in men who have sex with men (MSM).
How is gonnorhoea diagnosed?
1) Nucleic Acid Amplification Test (NAAT) on urine or swab from an exposed site – vagina, rectum, throat.
2) Gram stained smear from urethra/cervix/rectum in symptomatic people.
3) Culture of swab-obtained specimen from an exposed site using highly selective lysed blood agar in a
5% CO2 environment. Should be done for all confirmed cases to assess antibiotic sensitivity