Sexually Transmitted Infections - Introduction

Question 1

What is a commensal organism?

Answer 1

Commensal microorganism = microorganism that derives food or other benefits from another organism without hurting or helping it

Question 2

What is a pathogen?

Answer 2

Pathogen = a microorganism that can cause disease

Question 3

What is an infection?

Answer 3

Infection = invasion of all of part of the body by a microorganism, can be: no symptoms (sub-clinical) or symptoms (clinical)

Question 4

What is a sexually transmissible organism?

Answer 4

Sexually transmissible organism = virus, bacteria, protozoan, insect or arthropod which can be spread by sexual contact

Question 5

What is a sexually transmitted infection (STI)?

Answer 5

Sexually transmitted infection (STI) = infection by a pathogen which is sexually transmissible and which is unlikely to be transmitted by non-sexual means

Question 6

What is a sexually transmitted disease (STD)?

Answer 6

Sexually transmitted disease (STD) = a disorder of structure or function caused by a sexually transmitted pathogen

Question 7

What are examples of sexually transmitted organisms?

Answer 7

• Bacteria
  
  • Chlamydia trachomatis
  • Klebsiella granulomatis
  • Mycoplasma genitalium
  • Traponema pallidum (syphilis)
  • Neisseria gonorhoeae (gonorrhoea)
  • Haemophilus ducreyi (chancroid)
• Viruses
  
  • HSV
  • HIV
  • HPV
  • Molluscum contagiosum virus
• Parasites
  
  • Pthirus pubis
  • Sarcoptes scabei
  • Trichomonas vaginalis

Question 8

What organism causes syphilis?

Answer 8

• Traponema pallidum (syphilis)

Question 9

What organism causes gonorrhoea?

Answer 9

• Neisseria gonorhoeae (gonorrhoea)

Question 10

What organism causes chancroid?

Answer 10

• Haemophilus ducreyi (chancroid)

Question 11

What organism causes chlamydia?

Answer 11

• Chlamydia trachomatis

Question 12

What are some characteristics, and corresponding implications of STIs?

Answer 12

Question 13

What are different types of sexual contact from at most risk of catching an infection to least?

Answer 13

• Group sex
• Anal sex
• Vaginal sex
• Oral sex
  
  • Cunnilingus, fellatio
• Touching someone else’s genitals with your genitals
• Mutual masturbation
• “Pants on” cuddling

Question 14

What are some unpleasant symptoms STIs may cause?

Answer 14

• Unpleasant symptoms – grouped into syndromes
  
  • Ulceration
  • Lumps
  • Genital discharge
  • Non-genital discharge
  • Rashes

Question 15

What are some systemic symptoms STIs may cause?

Answer 15

• Fever
• Rash
• Lymphadenopathy
• Malaise
• Arthralgia and arthritis

Question 16

What are some possible late complications of STIs?

Answer 16

• Infertility – such as from chlamydia
• Cancer – cervical cancer from HPC
• Adverse pregnancy outcomes – from syphilis

Question 17

What is the reproductive number of an infectious disease?

What is it proportionate too?

Answer 17

Average number of infections produced

Question 18

For the reproductive number, what does it mean if R>1 and R<1?

Answer 18

R>1 means epidemic is sustained

R<1 means epidemic is reducing

Question 19

Why can prevalence of STIs be higher in certain groups?

Answer 19

Prevalence can be higher in certain groups due to people of that group usually having sex with each other, example is gay men:

• Cores and assertive mixing
  
  • Some people have sex with people like them, leading to high prevalence within a subpopulation (core) but limited spread through the wider community

These people however can spread it to other groups, such as a gay man occasionally having sex with a woman:

• Chains and random mixing
  
  • Random mixing leads to lower prevalence but wider dissemination along ‘chains’

Question 20

Describe a typical consultation with someone with symptoms suggestive of an STI?

Answer 20

• History
  
  • Sexual history as well as standard
• Partner notification
  
  • 2 ways of doing this - patient tells contacts (client referral), NHS tells contact (provider referral)
• Further testing
• Health promotion