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Bacterial Sexually Transmitted Infections


Three distinct bacterial pathogens causing sexually transmitted infections ... NCSP aimed to screen at least 15% of sexually active 16-24 year olds. ... – PowerPoint PPT presentation

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Title: 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
  • 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

  • Neisseria gonorrhoeae

Clinical and epidemiological aspects
  • 2nd commonest bacterial STI
  • 2007 18,710 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

Number of diagnoses of gonorrhoea by sex, GUM
clinics, England and Wales 1925 2006
Scotland Northern Ireland data are excluded
as they are incomplete from 1925 - 2003 Routine
GUM clinic returns
Rates of diagnosis of uncomplicated gonorrhoea by
sex and age group, GUM clinics, United Kingdom
1997 - 2006
Routine GUM clinic returns
Number of diagnoses of uncomplicated gonorrhoea
by sex and male sexual orientation, GUM clinics,
United Kingdom 1997 - 2006
Routine GUM clinic returns
Symptoms (if present)
  • Males urethral discharge, severe burning on
  • Females vaginal discharge, yellow or
    blood-stained, pain on urination
  • Rectal infection gives rise to pain and discharge
  • Pharyngeal infection, sore throat

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
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

Gram stain from a clinical sample
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.

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

Identification tests
  • Once you have cultured your samples you need to
    perform tests on single colonies to check/confirm
  • Oxidase test - result?
  • Gram stain what are you looking for?
  • Phadebact GC uses a specific monoclonal
  • API NH utilizes carbohydrates plus enzymes
    activity, similar to API 20E

N. gonorrhoeae is often referred to as a
gonococcus or GC
  • There is increasing resistance to penicillin and
    now ciprofloxacin
  • The recommended treatment of gonorrhoea is now
    either ceftriaxone (injectable) or cefixime
    (oral). As yet, no resistance has been reported
    to these third generation cephalosporins. In
    either case, a single dose is all that is
    necessary for the treatment of non-disseminated

  • Chlamydia trachomatis

Clinical and epidemiological aspects
  • The most common bacterial sexually transmitted
    infection, with 121,986 cases reported to the
    Health Protection Agency in 2007
  • The causative organism is Chlamydia trachomatis
  • The number of cases has risen steadily since the
    mid 1990s

Rates of diagnoses of uncomplicated genital
chlamydial infection by sex and country, GUM
clinics, United Kingdom 1997 - 2006
Routine GUM clinic returns
Rates of diagnoses of uncomplicated genital
chlamydial infection by sex and age group, GUM
clinics, United Kingdom 1997 - 2006
Routine GUM clinic returns
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 25s
    announced in 2003

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
  • Is it working?

Chlamydial disease
  • Also known as NSU or NGU
  • The infection has a longer incubation period than
    gonorrhoea, of 1 to 3 weeks compared to 2-3 days
  • As symptoms for gonorrhoea appear first this is
    why treatment for both infection is usually
  • Asymptomatic Chlamydial infection is common in
    both sexes at least 50 in males and 70 in

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

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

  • In up to 20 of patients with PID, infertility
    develops and the risk of ectopic pregnancy
  • The risk of infertility also increases if there
    has been more than one episode of PID
  • Infection in pregnancy can lead to infection of
    the baby - trachoma inclusion conjunctivitis or

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

  • During their lifecycle Chlamydia may be found in
    two forms elementary bodies and reticulate
  • 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

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

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
  • inside the vacuole, the RB grows and replicates
    its DNA
  • during this phase, the contents of the vacuole
    are termed an Inclusion Body

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

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)

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

Do you remember what a serotype is? see PIP!
  • Not an STI
  • very common in tropical countries and when
    sufferers dont get treated for the initial
  • transmitted via handsetc. and via flies

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

  • 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

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

  • Was rare in developed nations before 2003
  • 386 cases in UK in 2007 (500 increase in 10
  • Most often seen in men who are HIV positive

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?

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!

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

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

Other traditional tests
  • Direct immunofluorscence using a labelled
    monoclonal antibody specific to the major outer
    membrane protein (MOMP)
  • ELISA tests to detect Chlamydia antigen e.g.
    IDEIA are useful and can be automated
  • However, molecular tests are rapid, specific and

Molecular methods
  • A number of molecular methods based on
    amplification of Chlamydia nucleic acids have
    been introduced.
  • These include assays based on PCR, NASBA, TMA,
    Strand displacement amplification, LCR etc
  • Most common method in UK is BD ProbeTec SDA assay

  • Treponema pallidum

Clinical and epidemiological aspects
  • We have seen an 870 increase in cases of
    syphilis since 1996
  • In 2007, 2680 cases were reported to HPA
  • Age groups Males 25-44 years, Females 20-24
  • There are hotspots of cases in the UK e.g.
    London, Manchester
  • Most often seen in males, especially men who have
    sex with men (MSM)

Numbers of diagnoses of syphilis (primary,
secondary and early latent) by sex, GUM clinics,
England and Wales, and Scotland 1931 - 2006
Equivalent Scottish data are not available
prior to 1945. N. Ireland data from 1931 to 2000
are incomplete and have been excluded.Routine
GUM clinic returns
Number of diagnoses of infectious syphilis
(primary and secondary) by sex and male sexual
orientation, GUM clinics, United Kingdom 1997
Routine GUM clinic returns
Rates of diagnoses of infectious syphilis
(primary secondary) by sex and age group, GUM
clinics, United Kingdom 1997 - 2006
Routine GUM clinic returns
Stages of disease
  • There are four main stages of disease
    progressively more destructive.
  • Treatment can prevent development of the next
    stage -
  • 1. Primary
  • 2. Secondary
  • 3. Latent
  • 4. Tertiary

Clinical aspects
  • Caused by the spirochaete bacterium, Treponema
    pallidum ssp pallidum
  • Highly infectious
  • Starts with the development of one or more ulcers
    at the point of entry of the organism CHANCRE
  • A chancre is the lesion of primary syphilis
  • Typically painless and will disappear even
    without treatment

Primary syphilis
  • 30 who come into contact with syphilis during
    sex will be infected
  • Only 40 show symptoms of classical appearance
  • 90 day incubation period
  • Lesion will disappear within three weeks even
    without treatment.
  • Can be missed/dismissed by patient

Secondary syphilis
  • Usually appears around 6 weeks after chancre
  • Can be up to 2 years before signs show
  • Multiple system involvement
  • Mucosal and skin involvement most common
  • Symptoms will resolve in most cases.
  • The most infectious stage of syphilis

Syphilis the great mimic
  • The symptoms seen in patients with syphilis are
    highly variable and often similar to those seen
    in other diseases the great mimic
  • Makes diagnosis without laboratory testing very
  • Sir William Osler the physician who knows
    syphilis knows medicine"

Latent syphilis
  • Two stages
  • Early latent- up to 2 years
  • Patient still infectious
  • Late latent- after 2 years
  • Patient no longer sexually infectious although
    can still pass infection vertically

Tertiary syphilis
  • 3 - 20 years after primary infection
  • Benign gummatous phase - Characterized by slow
    growing granulomatous lesions
  • Infiltrative or destructive
  • Can affect any organ

Tertiary syphilis
  • May also see cardiovascular complications e.g.
    aortic aneurysm
  • Tertiary syphilis is often associated with
    dementia CNS involvement may also present as
    general paralysis of the insane, demyelination of
    the spinal cord resulting in pains, loss of
    feeling and difficulty walking. Changes in the
    joint - so-called Charcot's joints may develop
    owing to loss of nerve supply

Congenital syphilis
  • If infection is acquired in pregnancy, usually
    miscarriage or still-birth ensues. However, if
    the foetus survives, it may show signs of
    congenital syphilis the Hutchinsons Triad
    Hutchinsons teeth (pointed), deafness
  • There is a statutory requirement to screen all
    pregnant women for evidence of syphilis
    antibody test (see later)

  • Syphilis is a potentially devastating disease
    that is easy to treat, but it is essential that
    it is caught in the early stages.
  • Benzathine penicillin is usually used. A single
    dose is sufficient to cure primary syphilis,
    although longer treatments are required for later
    stages, including the treatment of late latent
    syphilis. No penicillin resistance has been

Treponema pallidum ssp pallidum
  • Treponema pallidum ssp pallidum is a very long,
    slender bacterium, which is about 0.1µm in
    diameter and 22µm in length
  • Since the maximum resolution of a bright-field
    microscope is 0.2µm, the organism cannot be seen
    by conventional microscopy
  • Cannot Gram stain this organism

T. pallidum as seen by EM
Treponema pallidum ssp pallidum
  • Can we culture this organism using artificial
  • NO!
  • The organism has undergone reductive evolution so
    it has lost many of the metabolic processes
    required for independent growth
  • This rules out using culture and identification
    as a diagnostic tool

Other subspecies
  • There are three other subspecies of T. pallidum
    these cause the non-venereal infections yaws,
    pinta and bejel
  • These are found in the Caribbean and W. Africa
    they are now very rare
  • However, we need to bear these in mind as the
    antibody response to syphilis is identical to
    these 3 infections
  • Potential for misdiagnosis when interpreting
    serology results!

Laboratory diagnosis
  • Diagnosis is usually confirmed using both
    clinical evidence and laboratory test results
  • Can we see syphilis down the microscope?
  • YES using dark ground microscopy
  • What are the disadvantages of this test?

T. pallidum by dark ground microscopy
Dark ground microscopy
  • Usually done in Genitourinary medicine clinics
  • Take fluid from an abraded ulcer view sample
    against a dark background
  • Treponema is apparent by virtue of refractivity
  • Also often see characteristic corkscrew motility

  • Can detect an antibody response to infection
    using serology
  • A major disadvantage of serology is the immune
    system takes a while to produce antibodies so
    early infection will be missed
  • There are a number of serological tests for
    syphilis BUT no one method is 100 reliable
  • This makes the interpretation of serological
    tests a bit tricky (but I will explain)

Serological tests
  • Serological tests for syphilis can be divided
    into two general types
  • Non-specific tests these rely on the fact that
    syphilis antibodies also bind (cross-react) to
    cardiolipin (found in ox heart) e.g. VDRL and RPR
  • Specific tests e.g. TPPA (TPHA), ELISA and FTA
  • If positive with one method must confirm with a
    second method

Venereal Disease Reference Laboratory test
  • Mix patient sera with antigen (cardiolipin) on a
    slide for 8 mins
  • Examine for agglutination (positive test)
  • Quantitative test if positive test a dilution
    series of sera to obtain the highest dilution
    which is positive antibody titre

  • VDRL becomes positive 1-2 weeks after chancre
    appearance (73) and reaches high titres in
    secondary syphilis (100)
  • BUT becomes negative in latent syphilis and also
    following treatment
  • Therefore this test is very important in
    monitoring the effect of treatment and
    stage/activity of disease
  • False positives are a problem (e.g. recent
    vaccination, connective tissue disease)

Treponema pallidum Particle Agglutination test
  • Specific test for syphilis antibodies
  • Patient sera diluted in a microtitre plate
  • Gelatin particles control particles
  • Gelatin particles coated with Treponema antigen
    test particles
  • Added to different wells
  • Incubate
  • Observe for agglutination indicates serum
    antibodies reacting with antigen on particles
  • If negative the particles will sink to the bottom
    of the well

  • Becomes positive in primary syphilis (71) and
    100 positive in secondary
  • Remains positive for life even if treated
  • Test used to be performed using sheep
    erythrocytes not gelatin particles TPHA
  • TPPA is a cumbersome test to perform so used as a
    confirmatory test
  • For screening patients (e.g. in pregnancy) we use
    an ELISA test - automated

  • Some ELISA kits detect IgG only (OK), others
    detect IgM IgG (best as helps determine stage
    of disease)
  • Positive in 82 of cases of primary syphilis and
    100 of secondary
  • Remains positive despite treatment (IgG)
  • If positive confirm usually with TPPA test

FTA (abs)
  • Indirect immunofluorescence test
  • Gold standard test positive in 86 of primary
    syphilis and 100 of secondary
  • However it is a cumbersome and difficult test to
    do so it is only performed in reference

Laboratory diagnosis of syphilis
  • If patient presents with an ulcer perform dark
    ground microscopy if positive begin treatment
    and monitor by serology
  • If no ulcer or microscopy is negative we must
    rely on serology
  • ELISA is used as a screening test as it is cheap,
    automated and rapid
  • If positive perform a TPPA to confirm a true

Laboratory diagnosis of syphilis
  • If positive by ELISA and TPPA begin treatment and
    perform VDRL test to ensure patient is clear from
  • What laboratory results would you see in a case
    of secondary syphilis?
  • Or latent syphilis?
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