Gender, family and culture - Microbiology Flashcards
Why are STIs difficult to control?
- Increasing density and mobility of human population
- The difficulty of engineering changes in human sexual behaviour
- The absence of vaccines for almost all STIs, except for the HPV vaccine
Microorganisms gain entry via the urogenital tract. Explain why microorganisms spread so easy in the urogenital tract?
The urogenital tract is a continuum, so microogranisms can spread easily from one part to another
Describe the host defences and microboial strategies against it
- Integrity of mucosal surface - specific attachment mechanism
- Urine flow (for uretherthral infction) - specific attachment mechanism, infection of urethrl epithelial or subepithelial cells
- Phagocytosis (especially polymorphia) - induce negligble inflammation, resist phagocytosis
- Complement - C3d receptor on pathogen binds c3b/d and reduces C3b/d-mediated polymorph phagocytosis
- Inflammation -Induce strong inflammatory response, yet evade consequences
- Antibodies (especially IgA) - produce IgA protease
- Cell-mediated immune response (T cells, lymphokines, NK cells etc) - antigenic variation; allows re-infection of a gven indiviudal with an antigenic variantand poorly understood factors cause ineffective cell-mediated response
a) Most microbes are unstable on drying. How does this affect their transmission?
b) Describe 5 examples of unstable micoorganisms and the consequences
a) Most STIs are unstable on drying so as a result require close repiratory/sexual contact or spread via vectors or water/food
b) E.g.,
- Influenza reuires close repiratory contact
- HIV requires close sexual contact
- Vibrio cholerae is spread via water, food
- Malaria is spread via vectors
- Larvae/eggs of worms need moist soil (except pinworms)
Describe the vaginal defences
- During reproductive life, vaginal epithelium contains glycogen which is metabolized to lactic acid. As a result, the pH is about 5.0 which inhibits colonization by all (except lactobacilli and certain other streptococci and diphtheroids)
- Normal vaginal secretions conatin 108/mL of these commensal bacteria
Describe how semen acts as a source of infection
- Cytomegalovirus (CMV) that is shed from oropharynx is also often present in large quantities in semen
- Hep B and HIV are also present in semen
a) What organism causes syphilis?
b) What is the structure of the organism?
c) Describe the transmission of this organism
a) Treponema pallidum
b) spirochete
c)
- T.pallidum enters the body through minute abrasions or mucous membranes
- Transmission requires close personal contact; horizontal spread occurs through sexual and vertical spread via transplacental infection of the foetus
What is horizontal and vertical transmission of syphylsis?
Horizontal transmission - occurs through sexual contact
Vertical spread - Infected women can trasmit T.pallidum to her baby in utero (transplancental infection of the foeutus)
An infected women an transmit T.pallidum to her baby in utero. Congenital syphilis is acquired after 3 months of pregnanacy. Describe the 3 ways the disease can manifest as
- Serious infection - resulting in intrauterine death
- Congenital abnormalities - which may be obvious at birth
- Silent infection - which may not be apparent until 2 years (facial and tooth deformities)
Describe the serological diagnosis of syphilis
Non-specific test (non-treponema tests)
- Veneral Disease Rearch Lab (VDRL)
- Rapid Plasma Reagin (RRR) test
Specific test
- Enzyme-lnked immunosorbent (ELISA) detecting IgM and IgG
- Confirmation of diagnosis depends upon several serological tests
a) Describe the treatment of syphilis
b) Describe treatment reactions to penicillin
a) Penicillin is the drug of choice for treating people with syphilis and their contacts
b)
- Anaphylaxis
- Jarsch-Herxheimer - acute febrile reaction that is charcterised by headache, malaie, myalgia and resolves within 24hrs
- Procraine reaction - fear of impending death and may be associated with hallucinations or fits
How is 2’ and 3’ syphilis disease prevented?
- Early diagnosis
- Adequate treatment
- Contact tracing with screening important
How is congenital syphilis prevented?
If women are screened serologically early in pregnancy (< 3 months) and those positive treated with penicillin
a) What organism is gonorrhea caused by and what type of organism is it?
b) What is the structure of this organism?
a) Neisseria gonorrhoeae - gram negative bacteria (the genococcus)
b) coccus
a) Describe the infection of gonorrhea
b) What can persistent untreated infection lead to?
a) Infection is usually localised, but in some cases,bacteria isolates and can invade blood stream and so spread to other parts of the body
b) Chronic inflammation and fibrosis
a) When do symptoms of gonorrhoea develop?
b) Describe the clincial symptoms of gonorrohoea in males and females
a) Develops within 2-7 days on infenction
b)
Male - urethral discharge and dysuria
Female - vaginal discharge or dysuria
At least 50% of all infected women with gonorrhea have only mild symptoms or are asymptomatic until complications arise. List these complications
- Pelvic inflammatory disease (PID)
- Chronic pelvic pain
- Infertility resulting from damage to the fallopian tubes
Describe the manifestation of systemic spread of gonorrohea
- Skin lesions
- Endocarditis
- Arthritis
- Ophthalmia neontarium (charcterised by sticky discharge in eyes)
- Gonoccal infection of throat may result in sore throat
Describe the diagnosis of gonorrhea
Diagnosis is made from microcopy and culture of appropriate specimens + molecular tests
a) Describe the treatment of gonorrhoea
b) Why is gonorrhoea no longer treated with a single oral dose of antimicrobials?
c) What is the added benefit of this treatmtent?
d) How is the spread of gonorrohea controlled?
a) Ceftriaxone 500mg and azithromycin 1g
b) Due to emerging resistance it is making it increasingly difficult to cure gonorrhoea with a single oral dose antimicrobials
c) It also targets chlamydia
d) Follow-up of patients and contact tracing
a) Name the species that causes chlamydial infection (sexually transmitted genital infections) including the serotypes
b) What type of organism is it?
a) Chlamydia trochamatis serotypes D-K
b) bacteria
Name the 3 species of Chlamydia
- Chlamydia trochamatis
- Chalmydi Pistacci
- Chlamydia pneumonia (infects respiratory tract)
The species of C.trochamatis can be subdivided into different serotpes. Which serotypes are associated with men who have sex with men?
Serotypes L1, L2, L3
Describe the entry and replication of chlamydia
- Chlamydia enter the host through minute abrasions in the mucosal surface
- They bind to specific receptors on the host cells and enter th cells by ‘parasit induced’ endocytosis
How does the genital tract infections with serotypes D-K affect females and males differently
Genital tract infections with serotypes D-K are locally asymptomatic in most women but usually symptomatic in men
Describe the clinical features of chlamydial infection in woem
- Infection is asymptomatic in about 80% of patients
- May cause intermenstrual and/or post-coital bleeding
- Dysuria
- Vagina discharge
Descibe the diagnosis and treatment of chlamydia
Diagnosis - A variety of nucleic-acid-bsed test are commercially available for chlamydial detection
Treatment - treated/prevented with doxycycline or azithromycin
Which herpes simplex is the most common cause of genital herpes?
HSV-2
Which STI is HSV-2 (causing genital herpes) associated with? Explain why
HSV-2 is associated with HIV.
HSV-2 infection can result in a two-fold increased risk of developing HIV; due to breaches in mucosal barrier beacuse of the HSV ulcers
Describe the clinical presentation of genital herpes causes by herpes simplex virus (HSV)
- Ulcerating vesicle that can take up to 2 weeks to heal
- Recurrent lesions (‘genital cold sores’)
- Aseptic meningitis or encephalitis can occur as a rare complicication in adults
- Spread of infection from mother to infant at the time of delivery can give rise to neonatal disseminated herpes or encephalitis
Describe the diagnosis and treament of genital herpes
Diagnosis
- Diagnosed by clinical appearance
- HSV DNA can be detected and typed in vescile fluid or ulcer swabs
Treatment
- Aciclovir can be used for treatment and prophylaxis
a) What does HPV infect?
c) What condition is it linked with?
a) Infects skin or mucosal surfaces
b) Linked with cervicle cancer
What are the 1st targets of HIV?
CD4 receptor-bearing cell including T-helper cells, monocytes, Langerhans cells and other dendritic cell, macrophages, amd microglia
Describe the diagnosis and treatment of HIV
Diagnosis
- Laboratory tests for HIV infection involve both serological and molecular analysis
Treatment
- Antiretroviral therpay resuts in a dramatic improvememnt in disease prognosis
a) What is candida albicans? Is it considered an STI?
b) Does vulvovaginal candidiasis always imply sexual transmission?
a) It is a pathogenic yeast that causes a range of genital tract diseases (thrush). It is not considered an STI
b) The yeast is a normal inhabitant of the female vaginal so whilst Candida can be transmitted sexually, the prescnece of vulvovaginal candidiasis does not necessarily imply ssexual transmission
a) What is trichomonas vaginalis and is considered an STI?
b) Where does it inhabit?
a) It is a protozoan parasite and causes vaginitis with copious discharge.It not considered an STI
b)
- The vagina in women
- The urethra (and sometimesthe prostate) in men
a) What is bacterial vaginosis and is it considered an STI?
b) What organism is it associated with?
c) This non-specific syndrome is charcterized by at least three of four signs and symptoms. What are the four signs and symptoms?
a) It is a type of vaginal inflammation caused by the overgrowth of bacteria naturally found in the vagina.I is not considered and STI
b) Gardnerella vaginalis
c)
- Excessive malodorous vaginal discharge
- Vaginal pH > 4.5
- Presence of clue cells (vaginal epithelial cells coated with bacteria)
- A fishy amine-like odour
Name 6 opportunist STIs
- Hep B
- Hep A
- Salmonellae
- Shigellae
- Giardia intestinalis
- Entamoeba histolytica
