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Bacterial Sexually Transmitted Infections

Bacterial Sexually Transmitted Infections. Patrick Kimmitt. Today we are going to look at…. Three distinct bacterial pathogens causing sexually transmitted infections Neisseria gonorrhoeae Chlamydia trachomatis Treponema pallidum. We are going to consider….

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Bacterial Sexually Transmitted Infections

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  1. Bacterial Sexually Transmitted Infections Patrick Kimmitt

  2. Today we are going to look at… • Three distinct bacterial pathogens causing sexually transmitted infections • Neisseria gonorrhoeae • Chlamydia trachomatis • Treponema pallidum

  3. We are going to consider… • The organism, structure and physiology • The pathology of disease • Epidemiology • Laboratory diagnosis and treatment • There are many contrasts when looking at these uniquely adapted pathogens • You should be able to discuss each of these aspects • But first some background…

  4. National Survey of Sexual Attitudes and LifestylesChanges Between 1990-2000 • Age first sexual intercourse ↓ • Number of lifetime partners ↑ • Marriage ↓ cohabitation ↑ • Risky behaviours ↑ • Partner change, unsafe sex Greater changes in; • women • those living outside London

  5. Number of new diagnoses of selected STIs, GUM clinics, United Kingdom: 2007 Routine GUM clinic returns

  6. 2011 • The upward trend in STIs appears to be continuing • ~430,000 new cases of STIs • Attributed to increased numbers of tests and continued ‘risky behaviour’ • ~1 in 10 of those 18-24 years with an STI get a new infection within a year • Tackling STIs poses unique problems

  7. STIs and social stigma • Unlike most other infections STIs tend to be considered embarrassing and it is often difficult to discuss them openly • This affects some groups more than others e.g. teenagers, sex workers, some cultural groups • Lots of initiatives to address this but little impact so far (Kimmitt et al., 2010 Int. J. STD & AIDS) • Web 2.0 resources can be used both positively (confidential advice, etc) and negatively (finding sex partners)

  8. Taking a sexual history and contact tracing is essential • What did you do? • With whom? • When? • Where? • And what symptoms did it leave you with?

  9. Gonorrhoea Neisseria gonorrhoeae

  10. Clinical and epidemiological aspects • 2nd commonest bacterial STI • 2011: 20,398 cases reported to HPA • Most common age groups: males 20-24 females 16-19 • Males: usually symptomatic • Females: often asymptomatic • Complications: untreated females – PID, infertility, ectopic pregnancy

  11. Symptoms (if present) • Males: urethral discharge, severe burning on urination • Females: vaginal discharge, yellow or blood-stained, pain on urination • Rectal infection gives rise to pain and discharge • Pharyngeal infection, sore throat

  12. Urethral gonorrhoea in a male

  13. Symptoms 2 • Both sexes: disseminated infection on rare occasions – usually as septic arthritis* • Infection during pregnancy may lead to ophthalmia neonatorum of baby (conjunctivitis)- blindness • May see dual genital infection with Chlamydia trachomatis – usual to treat for both at time of gonorrhoea diagnosis * For more info – Kimmitt et al Journal of Travel Medicine (2008); 15; 369-371

  14. Neisseria gonorrhoeae • The causative organism is Neisseria gonorrhoeae, a Gram-negative diplococcus i.e. often see cells as a pair. The genus Neisseria contains one other pathogenic species, N. meningitidis, which is the principle cause of bacterial meningitis. There are also many non-pathogenic species of Neisseria, often found in the pharynx

  15. Gram stain from a clinical sample

  16. Neisseria gonorrhoeae • N. gonorrhoeae is phagocytosed by polymorphonuclear neutrophils but resists intracellular destruction, remaining intact within the neutrophil. • It is fastidious, sensitive to desiccation and requires aerobic incubation with 5% carbon dioxide for growth. It grows as a small colony, often requiring 48 hours incubation. The colonies are grey, shiny, often with an irregular edge. The organism is catalase positive and rapidly oxidase positive. • No protective antibody response to gonorrhoea: recurrent infections are common in people who are at risk.

  17. Laboratory methods • Culture is required - for identification and antibiotic sensitivity tests • Urethral, cervical, rectal or pharyngeal swab • Use selective medium containing antibiotics and growth supplements (look this up) • e.g. Thayer Martin or New York City media • Molecular tests have been developed for the direct detection of N. gonorrhoeae infection and a single swab may be used in a double test to detect N. gonorrhoeae and Chlamydia trachomatis. • Commercial tests include the COBAS Amplicor and SDA tests

  18. Identification tests • Once you have cultured your samples you need to perform tests on single colonies to check/confirm identification • Oxidase test • Gram stain • Phadebact GC* – uses a specific monoclonal antibody • API NH – utilizes carbohydrates plus enzymes activity, similar to API 20E * N. gonorrhoeae is often referred to as a gonococcus or GC

  19. Treatment • There is increasing resistance to penicillin and now ciprofloxacin • Treatment of gonorrhoea is now either ceftriaxone (injectable) or cefixime (oral). • Worryingly, cases of cephalosporin resistance have emerged and are increasing, it is now recommended to give higher doses or use in combination with another antibiotic

  20. Chlamydia Chlamydia trachomatis

  21. Clinical and epidemiological aspects • The most common bacterial sexually transmitted infection, with 183,561 cases reported to the Health Protection Agency in 2011 • The causative organism is Chlamydia trachomatis • The number of cases has risen steadily since the mid 1990s

  22. Rates of diagnoses of uncomplicated genital chlamydial infection by sex and country, GUM clinics, United Kingdom: 1997 - 2006 Males Females Routine GUM clinic returns

  23. Chlamydia STIs • We have known about Chlamydia causing STIs for many years but it is only in the last 10-15 years where we have seen it emerge as a major pathogen • Most common age groups: males 20-24 females 16-19 • Government screening for Chlamydia in under 25’s announced in 2003

  24. National Chlamydia Screening Programme • NCSP aimed to screen at least 15% of sexually active 16-24 year olds. • £70m invested – aim to reduce the burden of disease due to Chlamydia • Hospital labs have seen a dramatic increase in their Chlamydia testing workload – 2.2 million tests were done in 2010-11 • Is it working?

  25. Chlamydial disease • The infection has a longer incubation period than gonorrhoea, of 1 to 3 weeks compared to 2-3 days (usually) • As symptoms for gonorrhoea appear first this is why treatment for both infection is usually offered • Asymptomatic Chlamydial infection is common in both sexes – at least 50% in males and 70% in females

  26. Symptoms (when present) Females: • unusual vaginal discharge • bleeding (intramenstrual) • pain on urination • lower abdominal pain Males: • urethral discharge • burning and itching in genital area • pain on urination

  27. Symptoms • In some cases the symptoms subside after a few days • In either sex, complications may ensue in the case of untreated infection • In males, untreated infection may lead to epididymitis and Reiter’s Syndrome (arthritis) • In females, the consequences of untreated infection are pelvic inflammatory disease (PID) in 10 to 40% of cases

  28. Symptoms • In up to 20% of patients with PID, infertility develops and the risk of ectopic pregnancy increases • Infection in pregnancy can lead to infection of the baby - trachoma inclusion conjunctivitis or pneumonia

  29. Chlamydia lifecycle • Chlamydia is an unusual bacterial genus – it is an obligate intracellular pathogen • Over time it has lost the capacity to replicate independently • How would this affect laboratory diagnosis?

  30. Lifecycle • During their lifecycle Chlamydia may be found in two forms – elementary bodies and reticulate bodies • the infective form of Chlamydia is the Elementary Body (EB), a dense, circular body, about 0.3μm in diameter. EBs are fairly inert and can survive outside the cell

  31. Life cycle • EBs carry glycosaminoglycan molecules on their surfaces that bind to receptors on the surface of certain cells • after attachment, the EB is taken into the cell by endocytosis and remains inside the endocytotic vacuole for the next phase of the life cycle

  32. Life cycle • the EB develops into a Reticulate Body (RB) which is larger (0.5 to 1.0μm) and metabolically active, although it uses host cell ATP-generating systems • inside the vacuole, the RB grows and replicates its DNA • during this phase, the contents of the vacuole are termed an “Inclusion Body”

  33. Life cycle • Staining of the Inclusion Body with iodine todemonstrateinfection of cellcultures

  34. Life cycle EB Formation and Release • after 18 to 24 hours,the RB reorganisesinto many EBswhich are releasedon cell rupture(24 to 48 hoursafter infection)

  35. Chlamydia trachomatis • There are many different serotypes* and these can be grouped according to the type of disease that they cause – not all infections are STIs! • Serotypes A, B and C cause a serious eye infection that begins with conjunctivitis and may progress (particularly with repeated infection) to conjunctival scarring and blindness – trachoma • Serotypes D to K cause a less severe form of conjunctivitis that does not usually result in trachoma * Do you remember what a serotype is?

  36. Trachoma • Not an STI • very common in tropical countries and when sufferers don’t get treated for the initial infection • transmitted via handsetc. and via flies

  37. C. trachomatis STIs • The more common type of infection associated with serotypes D to K is sexually transmitted: • NGU (non-gonococcal urethritis) in males (also called NSU: non-specific urethritis) • urethritis, cervicitis, salpingitis in females • can lead to PID (pelvic inflammatory disease) and resulting infertility due to scarring of Fallopian tubes • also increased risk of ectopic pregnancy

  38. Treatment • Azithromycin (clamelle) is usually first choice – single dose is enough • Alternatively can use doxycycline (adults) or erythromycin (babies) - Treat for extended periods (1-3 weeks due to prolonged replication cycle)

  39. Lymphogranuloma venereum • C. trachomatis serotypes L1, L2 and L3 only cause LGV (lymhogranuloma venereum) • begins with a genital ulcer, infection spreads to inguinal lymph nodes which enlarge and break down, discharging pus • if untreated, can lead to enlargement &granulomatous hypertrophy of glands

  40. LGV • Was rare in developed nations before 2003 • 1999 cases in UK in 2011 a rapid recent increase • Most often seen in men who are MSM (>99% of cases) and HIV positive (78%)

  41. Diagnosis of Chlamydia infection • You have two options – 1) Use highly trained professionals or 2) Have a go yourself at home • Which do you think is the most sensible?

  42. Home Chlamydia testing • While better than no testing at all there are concerns that some will not follow the procedure correctly – these tests need to be idiot proof! • Based upon an immunochromatography test on urine – positive = colour change • Such methods are not very sensitive so some positives will be missed!

  43. Laboratory diagnosis • Sample type may be a swab from the affected area (e.g. urethra) or urine is acceptable for some tests • Traditional laboratory methods include tissue culture assay, ELISA and immunofluorescence • These are now being replaced by molecular assays

  44. Tissue culture • Tissue Culture in cycloheximide-treated McCoy cells – detection of inclusion bodies by iodine staining or IF • Cumbersome method

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