M6 - Genitourinary Infections Flashcards
What groups of people are mainly at risk
- Young heterosexuals
- Male homosexuals
- Minority ethnic groups
What are some of the underlying causes of increases of STD prevalence in the UK
- More tolerance towards sexual diversity and behaviour
- Inconsistent use of condoms, especially among the younger groups of people
- High levels of asymptomatic infection
- Poor access to GUM clinics and sexual health services
- GUM clinics running at capacity
What bacteria causes gonorrhoea
Neisseria Gonorrhoeae
What are the characteristics of neisseria gonorrhoeae
- Human pathogen spread by sexual contact, acute and relatively easy to treat
- Gram -ve cocci
- Aerobic
- Catalase +ve
- Oxidase +ve
- Best growth in 5-10% CO2, moist atmosphere
- Occur in pairs, spherical
How does gonorrhoea present
- Purulent infection of the mucous membrane of the urethra and cervix (also rectal and pharyngeal)
- Purulent discharge, dysuria
- Microscope = bacteria seen inside polymorphonuclear cells of the inflammatory exudate
If gonorrhoea is left untreated, what complications can occur
- Epididymitis, can spread to testicle - possibility of infarction (necrosis)
- Salpingitis inflammation of the fallopian tube - can lead to pelvic inflammation disease and sterility
- Purulent conjunctivitis in newborn - blindness possible
- Disseminated gonorrhoea (fever, painful joints, skin lesions)
Describe the treatment of gonorrhoea
Penicillin - slow release intramuscular also tetracycline, ceftriaxone
N.B. Beta-lactamase mediated penicillin resistance
What are spirochaetes
Spiral bacteria
What is the causative organism of syphilis
Treponema Pallidum (spirochaete)
Describe the characteristics of treponema pallidum
- Spiral shaped bacterium
- Rigid cell
- Motile - polar flagella enclosed in outer membrane
What can be used to observe treponema pallidum
- Visible through dark ground microscopy, UV microscopy using anti-treponema antibodies linked to fluorescein
How does T.pallidum enter the body
Enters by penetration of intact mucosa or through abraded skin
N.B low no. of cells probably required for infection
Describe primary syphilis
- Bacteria multiply at entry site
- Lesion at approx 3 wks (painless) frequently on external genitalia
- Chancre (lesion) heals after approx 6 wks.
Describe secondary syphilis
2-12 wks after primary infection
- Macular or pustular lesion/rash esp on trunk and extremities
- Highly infectious lesions
- Also flu-like illness
What oral manifestation suggests secondary syphilis
Snail track ulcer
Describe Tertiary syphilis
3-30 years later if left untreated
- Slow, progressive destructive inflammatory disease that can affect any organ - neurosyphilis, CVS, gummatous (bones and skin lesions)
Describe the features of congenital syphilis
In-utero transmission of T.pallidum to baby after 3 months of pregnancy
- Possible death of foetus
- Congenital abnormalities/deformities
- Facial and tooth deformities arising a few years later
Name a tooth deformity associated with congenital syphilis
Hutchinson’s teeth - moon shaped edges to teeth/incisors
Describe the diagnosis of syphilis and why its hard
Cant be grown on agar in lab
- Microscopy + serological (antibodies)
Describe the non-specific diagnosis test for syphilis
Cardiolipin antibody test - screening - if positive will then take specific test
Describe the specific diagnosis test for syphilis
Use treponemal antigens e.g. VDRL - T.Pallidum antibody tests - Treponema pallidum immobilisation test (TPI) live treponemes immobilised by antibodies in the patient’s serum
What is the treatment route for syphilis
Penicillin or Tetracyclines, erythromycin, chloramphenicol
What is the causative agent of chlamydia std infection
Chlamydia. trachomatis
there are other chlamydias that cause other forms of chlamydia infection
Describe the basic morphology of chlamydia bacteria
- Small bacteria
- Obligate intracellular parasites
Describe the basic life cycle of chlamydia organisms
- Elementary bodies (EB) - live outside body of host and initiate infection
- Attachment + entry to host
- Reticulate bodies (RB) - non-infectious for intracellular multiplication, new EB’s produced to invade adjacent cells
Describe the clinical manifestations of chlamydia infection
They indicate damage from cell destruction and inflammatory response and give rise to urethritis, cervicitis, epididymitis, conjunctivitis etc.
NB - asymptomatic infection in women is common
How is lab diagnosis of chlamydia infections carried out
- Cell culture growth as they are obligate intracellular pathogens (parasites)
- Immunofluorescent staining
- Direct Ag (antigen) detection in smears
What is chlamydia usually treated with
Tetracycline
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Chlamydia is often asymptomatic and can lead to pelvic inflammatory disease, ectopic pregnancy etc
Describe the aetiology of UTIs
Usually an ascending bacterial infection:
Urethra -> bladder -> kidney -> urinary tract
Occasionally will continue to invade the blood stream and cause septicaemia
Much less commonly bacteria can each the kidney by the haematogenous route
What are some of the predisposing factors of UTI
- Disruption of urine flow, e.g. catheterisation, pregnancy, prostratic hypertrophy
- Shorter urethra in females than males
- UTI incidence is higher amongst sexually active populations
- Male infants; due to faecal organisms
- Prevention of complete bladder emptying makes person more susceptible to infection
- Reflux of urine from bladder to ureters predisposes to ascending infection and kidney damage
- Diabetes can mean more severe infections
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Women more likely to get UTIs than men
What is a common bacteria type that causes UTIs
E.Coli due to faecal contamination
Why are E.Coli bacteria a common UTI causative agent
- Have particular types of antigen pili from adherence to urethral and bladder epithelium
- Capsular polysaccharides (K antigens) are associated with ability to cause pylonephritis and resist host phagocytosis
- Haemolysin production: membrane damaging
Name another faecal organism besides E.Coli than can cause UTIs
Proteus Mirabilis (very motile) - Urease production is significant in pyelonephritis
What are some of the host defences against UTIs
- Urinary tract is generally resistant to colonisation
- pH, chemical composition and flushing action of urine helps to dispose of bacteria in urethra and prevents growth of commonly urethral bacteria
What are the clinical features of lower urinary tract infections
- Acute infections: dysuria, pain
- Cloudy urine: due to cells and bacteria often with catheterised patients. Possibility of chronic inflammatory changes in the bladder, prostate and periurethral glands
- Prostatitis: acute, chronic
What are the clinical feature of Upper Urinary tract infections
- More difficult to diagnose as distinct from lower UTIs
- Symptoms as lower UTI + fever often as kidney is involved (pyelonephritis)
- Recurrent pyelonephritis leads to renal damage
Describe the Lab diagnosis of UTIs
All about finding high levels of bacteria in urine:
Bacteruria defined as significant when a midstream urine sample has >10^5 bacteria per ml
Infected urine will likely have only one species of bacteria in the urine as well
Also >10 WBCs per ml of urine is abnormal and may indicate infection
What methods of urine collection are there
- Midstream urine
- Catheter
- Supra pubic (from bladder)
What bacteriological media are commonly used in lab diagnosis of UTIs
- Blood agar (non-selective medium)
- MacConkeys agar (selective medium for GI tract bacteria)
- 35-37C for 18 hours
Describe the treatment of UTIs
- Uncomplicated case = Trimethoprim or ampicillin (5 days)
- If organism is resistant (50% amp. resistance incidence) then cephaloxin
