Sexually Transmitted Infections - an introduction

Question 1

Commensal micro-organism

Answer 1

A micro-organism that derives food or other benefits from another organism without hurting or helping it.

Question 2

Pathogen

Answer 2

A micro-organism that can cause disease.

Question 3

infection

clinical or subclinical

Answer 3

The invasion of all or part of the body by a micro-organism.

No symptoms sub-clinical
Symptoms clinical

Question 4

Sexually transmissible organism

Answer 4

A virus, bacteria, protozoan, insect or arthropod which can be spread by sexual contact
Commensal
Pathogen

Question 5

Sexually transmitted infection (STI)

Answer 5

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

Question 6

Sexually transmitted disease (STD)

Answer 6

A disorder of structure or function caused by a sexually transmitted pathogen
Pelvic inflammatory disease
Genital warts

Question 7

‘Venereal Diseases’

Answer 7

Syphilis (Treponema pallidum pallidum)

Gonorrhoea (Neisseria gonorhoeae)

Chancroid (Haemophilus ducreyi)

Question 8

Other official “Sexually transmitted”
organisms in the UK

Answer 8

Bacteria
Chlamydia trachomatis
Klebsiella granulomatis
Mycoplasma genitalium

Viruses
HSV
HIV
HPV
Molluscum contagiosum virus

Parasites
Pthirus pubis
Sarcoptes scabei
Trichomonas vaginalis

Question 9

Controversies:
Infection or colonisation?

Answer 9

Mycoplasma hominis
Ureaplasma urealyticum
Bacterial vaginosis
Genital candidosis

Question 10

Activity required for transmission

Answer 10

Skin contact only
pubic lice (Pthirus pubis)
Scabies (Sarcoptes scabeii)
Warts (human papilloma virus types 6 &11)
Herpes (Herpes Simplex Virus types 1 & 2)

Group sex
Hepatitis C

Question 11

What does sexual contact mean?

Answer 11

Group sex
Anal sex
Vaginal sex
Oral sex - cunnilingus
Oral sex - fellatio
Touching someone else’s genitals with your genitals.
Mutual masturbation
‘Pants on’ cuddling

Question 12

Why are STIs important?

Answer 12

STDs cause morbidity and can even kill.
Unpleasant symptoms – grouped in to syndromes
Psychological distress

• ulceration
  -lumps
  -discharge (non genital, genital)
  -systemic symptoms

drain resources
common

Question 13

late complications

Answer 13

Infertility - chlamydia
Cancer. 250,000+ deaths globally from cervical cancer - HPV

300,000 adverse pregnancy outcomes from syphilis per year.

Question 14

R0=βcD

how do you calculate the reproductive number

Answer 14

R0 = reproductive number (average number of infections produced)

β = likelihood of transmission per encounter
c= rate of acquiring new partners
D= duration of infectivity

If R0 >1 then epidemic is sustained
If R0 <1 then epidemic reduces

Question 15

“Beer goggles” formula

Answer 15

An = number of units of alcohol consumed
S = smokiness of the room (graded from 0-10, where 0 clear air; 10 extremely smoky)
L = luminance of ‘person of interest’ (candelas per square metre; typically 1 pitch black; 150 as seen in normal room lighting)
Vo = Snellen visual acuity (6/6 normal; 6/12 just meets driving standard)
d = distance from ‘person of interest’ (metres; 0.5 to 3 metres)

Question 16

Better tests available

Answer 16

eg Nucleic Acid Amplification Tests
vs
Enzyme immunoassays for chlamydia

Question 17

The management of someone with symptoms suggestive of an STI

Answer 17

good history
partner notifiction
HIV testing
health promotion

Question 18

The consultation

Answer 18

Standard history components:
Presenting complaint
History of presenting complaint
PM/SHx
DHx
Include a gynae history.
Need to ask direct questions about symptoms
Eg “discharge from the penis/pain in abdomen?”

Question 19

why is a sexual history necessary

& good questions to ask

Answer 19

Determining possible cause of symptoms
Detecting high-risk behaviour and advising on risk reduction.
Tracing contacts

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

Question 20

how do you assess longer term sexual risk for men

Answer 20

Have you ever had sexual contact with another 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)
Paid for sex or been paid?

Question 21

how do you notify a partner for contact tracing

Answer 21

Patient tells contacts “client referral”
NHS tells contact “provider referral”

Question 22

Offer/recommend further testing and health promotion how do we do this?

Answer 22

Most STIs are risk factors for HIV acquisition and transmission.
If someone has one STI (eg chlamydia) they could have another (eg HIV)

Condoms prevent transmission of some STIs -
Eg HIV, chlamydia, gonorrhoea
Not so 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
Address hazardous drug use.
Vaccination
HIV pre-exposure prophylaxis