FINALS

• Sexually Transmitted Diseases (STDs)


  Infections that are passed from one person to another through sexual contact
• Causes of STDs


  • Bacteria
  • Parasites
  • Yeast
  • Viruses
• Examples of STDs


  • Syphilis
  • Gonorrhea
  • Chlamydia
  • Genital Herpes
  • Human Papilloma Virus
  • Trichomoniasis
• Syphilis


  Causative agent: Treponema pallidum (spirochete)
• Transmission of Syphilis


  1. Close personal contact

  2. Sexual contact - horizontal spread

  3. Transplacental infection of the fetus - vertical spread

  4. Enters through abrasions/mucous membrane
• Incubation period of Syphilis

  3 weeks
• Stages of Syphilis


  • Primary
  • Secondary
  • Latent
  • Tertiary
• Primary Stage of Syphilis


  • Positive for lesion
  • Chancre (3 weeks after infection)
• Secondary Stage of Syphilis


  • Headaches, general aches
  • Loss of appetite and maybe a fever
  • Dark red rash for few weeks or months (backs, legs, arms, hands, feet)
• Latent (hidden) Stage of Syphilis


  • No visible signs or symptoms
  • Early latent infection occurred within the past 12 months
  • Late latent syphilis is where infection occurred more than 12 months ago
  • Can last for years
• Tertiary Stage of Syphilis


  • Painful permanent ulcers on the skin
  • Lesions on ligaments, joints and on bones
  • Can attack the nervous system, the heart and blood vessels that results in blindness, paralysis, and insanity
• Congenital Syphilis


  • Acquired after the 1st three months of pregnancy
  • Serious infection resulting in intrauterine death
  • Congenital abnormalities, which may be obvious at birth
  • Silent infection, which may not be apparent until about two years of age
• Diagnosis of Syphilis


  • T. pallidum can't be grown in vitro
  • Microscopic identification
  • Can't be seen in gram stain
  • Serology (VDRL, RPR)
• VDRL and RPR


  • Non-specific tests that allow the detection of antibodies
  • Shows positive result within 4-6 weeks of infection (or 1-2 weeks after the primary chancre appears)
• Positive VDRL/RPR test


  • May mean you have syphilis
  • Next step is to confirm with FTA-ABS test
• FTA-ABS


  • Specific test using treponemal antigens extracted from T.pallidum
  • Confirms a positive result with non-specific test is truly due to syphilis
• TPHA


  Specific test that confirms a positive result with non-specific test is truly due to syphilis
• Treatment for Syphilis


  • Penicillin (Benzathine Penicillin G)
  • Tetracycline or Doxycycline (for patient allergic to penicillin)
  • Person usually cannot transmit syphilis 24 hours after starting treatment
• Gonorrhea


  • Causative agent: Neisseria gonorrhoeae (a gram-negative coccus)
  • Transmission: Sexual contact from person to person, Infected mother to the baby during childbirth
  • Risk of Infection after a single intercourse: 50% in women, 20% in men
• Symptoms of Gonorrhea


  • Develops within 2-7 days of infection
  • Women - almost always asymptomatic (vaginal discharge, pelvic inflammatory disease, chronic pelvic pain)
  • Men - urethral discharge and dysuria (TULO)
  • Infertility
• Diagnosis of Gonorrhea


  • Microscopy and culture of discharges and other specimens (gram-negative intracellular diplococci)
  • Antibiotic susceptibility test
  • Serologic tests are unsatisfactory
• Treatment for Gonorrhea


  • Incidence of resistance is increasing
  • Recommended antibiotics: Penicillin, Ciprofloxacin, Ceftriaxone
  • Alternatives: Gentamicin + Azithromycin, Cefixime
  • Prophylactic use has no effect in preventing sexually acquired gonorrhea
  • Ophthalmic antibacterial agents are effective for babies born to mothers with gonorrhea
• Chlamydial Infection


  • Causative agent: Chlamydia trachomatis
  • Serotypes: A, B, Ba, C (eye infection), D-K (urogenital infection), L1, L2, L3 (LGV)
  • Transmission: sexual intercourse, ocular-genital contact, through birth canal
• Clinical Effects of Chlamydial Infection


  • Most women are asymptomatic (urethritis, cervicitis, salpingitis, conjunctivitis, bartholinitis)
  • Symptomatic in men (urethritis, epididymitis, proctitis, conjunctivitis)
• Diagnostic Tests for Chlamydia


  • Cell culture
  • Direct antigen detection (Direct EIA)
  • Microscopic examination with fluorescein conjugated monoclonal antibodies (DFA)
  • Nucleic acid amplification test (NAAT)
• Treatment for Chlamydia


  • Chlamydia are not susceptible to beta-lactam antibiotics
  • Doxycycline/Tetracycline recommended
  • Erythromycin should be used for babies
• Cholera


  Bacterial infection caused by Vibrio cholerae
• Shigellosis


  Bacterial infection caused by Shigella bacteria
• Typhoid fever


  Severe bacterial infection caused by Salmonella typhi
• Diseases caused by E. coli


  Enterotoxigenic E. coli (ETEC), Enteropathogenic E. coli (EPEC), Enteroinvasive E. coli (EIEC), Enteroaggregative E. coli (EAEC), Enterohemorrhagic E. coli (EHEC)
• Bacterial Food Poisoning


  Intoxications, Staphylococci, Botulism, Infectious food poisoning, Salmonella, Campylobacter, Clostridium perfringens, Vibrio parahemolyticus, Bacillus cereus, Listeriosis

  
• Viral Gastroenteritis


  Rotavirus, Norwalk & related agents
• Shigella


  • Gram-negative rods, non-motile, non-spore forming, cannot ferment lactose, no capsule, S. sonnei common in US, S. flexneri common in Third World
• Shigella natural reservoir & transmission


  Man only "reservoir", mostly young children, fecal to oral contact, children to adults, transmitted by adult food handlers, unwashed hands
• Shigellosis


  Symptoms start 1-3 days after exposure with profuse watery diarrhea, can progress to dysentery with abdominal pain, intense diarrhea, relatively scant stool with blood, mucous, and white blood cells, symptoms usually resolve on their own in 1 week, rarely an infected person becomes a carrier
• Shigella pathogenic factors


  Ipa A,B,C, and D proteins are secreted into host cells, bacteria invade intestinal cells by endocytosis, escape from endocytotic vesicles and multiply inside the cells, directly invade adjacent cells, host cells die and mucosal abscess forms
• Shiga toxin


  Classic A/B toxin, B subunit binds to cells and gets A inside the cell, A inhibits protein synthesis by lysing 28S rRNA, cytotoxic for intestinal cells
• Treating shigellosis


  Manage dehydration, use of antibiotics (controversial if case is not severe), patients respond to antibiotics, disease duration diminished, fluoroquinolone
• Salmonella


  Over 2000 antigenic O and H serotypes, genetically single species, S. enterica serotype choleraesuis, S. typhi, S. paratyphi
• Salmonella natural reservoir


  Not humans, but many other animals, including birds, reptiles, many others and vegetation, eggs are also a risk