Transcript Chapter 24b
Sexually Transmitted Diseases • Epidemic over last 50 years – 330 million annually worldwide • Often asymptomatic in women – Increased risk of pelvic inflammatory disease, ectopic pregnancy, miscarriage, birth defects, sterility and cervical cancer • STD prevention methods – Proven effective • Sexual abstinence & mutual monogamy – Somewhat effective • proper, consistent condom use • ~20% failure rate • Bacterial Discharge Diseases – Increased fluid discharge for males and females • Gonorrhea (clap) • Chlamydia • co-infections ~45% of cases • Bacterial Ulcerative Diseases – Lesions on genitals of males and females • Syphilis Gonorrhea • Causative agent – Neisseria gonorrhoeae • Gram-negative; diplococci • Fimbriae and capsule • Low infecting dose • Signs & Symptoms – In men: • Most men are symptomatic • Pain on urination, discharge from penis – In women: • Women more likely to be asymptomatic (50-80%) • Painful urination, mild discharge – May be overlooked as UTI – ~25% develop PID – Less common manifestations: • Heart damage, arthritis, meningitis, UTI, pharyngitis • Antigenic variation – protects from antibodies • Opa proteins on fimbriae bind to T-cells – Prevents activation of immune response • IgA proteases • Gonococci survive and multiply in WBCs Endotoxin can cause damage to fallopian tubes Scar tissue leads to increased risk of ectopic pregnancy and sterility • Opthalmia neonatorum – Gonococcal conjunctivitis of the newborn – Acquired from infected birth canal – Prevented with silver nitrate or erythromycin in eyes • Epidemiology – Humans only host – Risk increases with number of sexual partners • More common in blacks(4X) and males (slightly) • Most cases involve adolescents with multiple partners – Factors that influence infection include • Birth control pills • Asymptomatic Carriers • Lack of immunity Overall incidence is declining except in southeastern states like MS and AL • Treatment – No vaccine available • Antigenic variation interferes with ability to make effective vaccine – Doxycycline for co-infection – Broad spectrum cephalosporins • Increasing number of strains resistant to numerous antibiotics Chlamydial Infections • Causative agent: Chlamydia trachomatis • Non-motile; obligate intracellular pathogen • Gram – with no PTG • Non-gonococcal urethritis (7 strains) • Lymphogranuloma venereum (3 strains) • Trachoma • Leading cause of preventable, non-traumatic blindness Unique life cycle with two cellular forms Elementary body is infectious stage (extracellular) Reticulate body is reproductive stage (intracellular) • Signs & Symptoms – In men: • Most (75%) symptomatic • Thin grayish-white discharge from penis • Sometimes epididymitis or orchitis • May lead to sterility – In women • Most (85%) asymptomatic • Increased vaginal discharge, painful urination • Risk of PID and sterility • Increased risk of cervical cancer for adolescents • Lymphogranuloma venereum – – – – Severe chlamydial STD (LGV strains) Strains tend to be isolated to the tropics Characterized by genital lesion at site of infection Followed by bubo in groin, fever, chills, myalgia and arthritis • Trachoma strains multiply in cells of conjunctiva – Kills cells and stimulates production of purulent discharge which scars conjunctiva – Eyelids turn inward and eyelashes scar cornea – Cornea fills with blood vessels and blindness results • Epidemiology: – Most common reportable STD in US – 500 million cases of trachoma worldwide • Newborns infected at birth • Direct, indirect and vector transmission also possible • Treatment – Azithromycin; tetracycline or erythromycin – Doxycycline for co-infection with gonorrhea – Erythromycin cream in infant eyes for 10-14 days for trachoma Syphilis • Causative agent – Treponema pallidum • Narrow Gram -, spirochete • Axial filaments • Can’t be cultivated in artificial media • Signs & Symptoms – Occurs in numerous forms • Often confused with other diseases – “great imitator” – Manifestation occurs in three stages • Primary stage • Secondary stage • Tertiary stage – Primary stage • Characterized by hard, painless, red ulcer – Chancre – Appears at the site of infection • Local lymph nodes become enlarged • Spontaneous healing of chancre • Secondary stage • Runny nose, watery eyes, sore throat, oral lesions, generalized aches and pains • Non-itchy rash – Usually on palms and soles of feet • Spontaneous healing – Tertiary stage • • • • Characteristic lesions called gummas Infection attacks other organs Numerous nervous system disorders Blindness; metal illness; stroke • Congenital syphilis • • • • Organism crosses placenta Nearly 40% result in miscarriage or stillbirth Begins as an early profuse nasal discharge Most children develop deformities – Hutchinson’s teeth, saddle nose, sabre shins • Organism penetrates mucous membrane and broken skin – Low infecting dose • Less than 100 organisms – Organism multiplies in localized area • Chancre caused by immune response • Spreads to lymph nodes and bloodstream • Epidemiology – Human only host – Transmitted via direct contact, blood transfusion, mother to fetus – 12 million annual cases worldwide – Maintain low incidence in US • Treatment – VDRL test used for diagnosis – Primary, secondary and congenital stages effectively treated with penicillin – No proven alternative for those with penicillin allergy – Antibiotics not effective for tertiary