Infectious Diseases Affecting the Urinary and Reproductive Systems
Urinary and Reproductive Systems: Infectious Diseases
Urinary Tract Defenses
Physical Flushing: Urine flow helps to remove microbes from the urinary tract.
Low pH: The acidity of urine inhibits the growth of many bacteria.
High Urea Content: Urea is toxic to some bacteria.
Antimicrobial Proteins:
Defensins: Antimicrobial peptides that disrupt bacterial membranes.
Secretory IgA: An antibody that neutralizes pathogens.
Small amounts of IgG and IgM: Antibodies that provide immune protection.
Prostate Secretion (Males): Contains zinc, which has antimicrobial properties.
Epithelial Cell Shedding: Removes attached bacteria.
Mucus Secretions and Ciliary Clearance: Trap and remove pathogens.
Indigenous Microbiota of the Urinary Tract
Kidneys, Ureters, and Bladder: Normally sterile.
Urethra: Often colonized near the terminus, with approximately 10-1000 cells/mL of urine.
Midstream Samples: Important for accurate infection diagnosis by avoiding normal microbiota contamination.
Transmission: Microbes can be transmitted to partners during sexual intercourse, especially from male to female.
Reproductive System Defenses
Males
Prostate Secretion: Contains zinc.
Localized Immune Responses: Antibodies along the urethra and in seminal fluid.
Females
Acidic vaginal pH encourages the growth of Lactobacillus which in turn lowers the pH.
Mucosa of the vagina and cervix.
Mucociliary Escalator: Transports mucus and trapped pathogens.
Antimicrobial Chemicals in Mucus:
Lysozyme: Antibacterial enzyme (Less friendly to sperm).
Lactoferrin: Iron-binding protein with antibacterial properties (High at day 7, low at day 21 of the menstrual cycle).
Antibacterial Peptides:
Defensins
IgA
IgG
Note: Lactoferrin, Definsins, IgA and IgG fluctuate oppositely during the menstrual cycle
Indigenous Microbiota of the Reproductive System
Males
Semen: Sterile.
Urethra: Accumulates indigenous microbiota as it travels along. The end of the urethra is naturally colonized.
Females
Acidic pH in vagina: Encourages growth of Lactobacillus, which lowers the pH.
Vulva and Cervix: Also colonized by various microbes.
Common Sexually Transmitted Diseases (STDs)
Chlamydia
Gonorrhea
Syphilis
Herpes Simplex Viruses
Human Papilloma Viruses
Trichomoniasis
Human Immunodeficiency Virus
STD Trends
Chlamydia and Gonorrhea Rates Among Females Aged 15-54
Chlamydia rates are significantly higher than gonorrhea rates across all age groups.
*Rate comparisons for Chlamydia and gonnorehea from the United Kingdom from 2009 to 2011
Chlamydia trachomatis
Characteristics
Ovoid-shaped with cellular and outer membranes, but no peptidoglycan.
Size:
Obligate intracellular pathogen.
Very small chromosome.
Unique biphasic life cycle.
Developmental Cycle of C. trachomatis
Elementary Body (EB): The infectious form that attaches to epithelial cells.
Reticulate Body (RB): The replicative form that multiplies within the host cell.
Process: EB attaches to the cell, transforms into RB, replicates, and then transforms back into EB to infect other cells.
Timescale: The cycle takes approximately 48-72 hours.
Chlamydia trachomatis
Epidemiology
Reservoir: Humans.
Transmission: Vertically (mother to child) or during sexual intercourse.
Chlamydial pharyngitis or proctitis may result from oral or anal intercourse.
Pathogenesis
Incubation period: 1-3 weeks.
Complications:
In females, 40% of untreated infections progress to Pelvic Inflammatory Disease (PID), including salpingitis, leading to infertility due to scarring, and ectopic pregnancies.
A leading cause of first-trimester-related deaths in the U.S.
In males, inflammation of the epididymis may result in sterility.
Neonatal conjunctivitis in newborns.
Symptoms
Asymptomatic in 80-90% of infected individuals.
Related to the inflammatory response of the immune system.
Discharge (difficult to distinguish in females).
Inflammation of the cervix.
Tingling in the penis.
Painful urination.
Treatment
95% cure rate with one dose of azithromycin or seven days of doxycycline.
Pregnant women cannot use doxycycline due to its effect on bone development in infants.
Neonatal conjunctivitis can be treated with oral antibiotics.
Prevention
Self-screening.
Safe sex practices.
Treatment of pregnant mothers before delivery.
Treponema pallidum
Characteristics
Spirochete with a flexible cell wall.
Motility: Moves using endoflagella (axial filaments) that rotate, causing the spirochete to corkscrew and move forward.
Structure: Outer membrane, cell membrane, and axial filaments.
Syphilis
Epidemiology
Reservoir: Humans.
Approximately 44,000 cases annually (85% males) in the U.S.
12 million cases worldwide.
Pathogenesis
Penetrates the epithelial surface of mucosal membranes of genitalia, wounds, hair follicles, or abrasions.
Penetrates the placental barrier after the third or fourth month of pregnancy, causing congenital syphilis.
Congenital Syphilis: Hutchinson’s triad includes deafness, impaired vision, and notched, peg-shaped teeth.
Stages of Syphilis
Primary
Chancre (painless ulcer) lasting 10-90 days.
Enlarged lymph nodes in the groin.
Secondary
Occurs in 30% of untreated primary cases.
Skin rash on palms and soles (3-12 weeks).
Flu-like symptoms.
Hair and weight loss.
May last for years or resolve without treatment.
Latent
Untreated during primary and secondary stages.
Non-contagious.
Asymptomatic.
Lasts 1-30 years.
Tertiary
Occurs in 40% of latent cases.
Lasts from 1 year to decades.
Causes severe damage to the body and pronounced symptoms, often resulting in death.
Symptoms include blindness, paralysis, numbness, uncoordinated muscle movements, heart problems, neurological problems, dementia, other mental disorders, and lesions on various parts of the body.
Syphilis
Treatment
Detection of infection:
Using fluorescence or dark-field microscopy from chancre sample.
Serological exams for antibodies in the serum.
Identification and treatment of sexual contacts of patients.
Penicillin: Usually a single dose for primary and secondary syphilis.
Prevention
Safe sex practices.
Treatment of pregnant mothers.
Trichomonas vaginalis
Characteristics
Anaerobic eukaryotic parasite.
Only has the trophozoite stage.
Most common protozoan infection in humans in industrialized countries.
Trichomonas vaginalis
Epidemiology
Reservoir: Humans.
160 million cases per year worldwide.
Pathogenesis
Transmitted sexually, most commonly through vaginal intercourse.
Specializes in attachment to vaginal epithelial cells.
Sensitive to time, temperature, and pH.
Attachment damages epithelial cells causing inflammation, and RBCs released will also lyse.
Predisposes tissue to other infections, making complications common.
Symptoms
Women:
Strawberry cervix (punctate hemorrhages).
Vaginalis characterized by frothy, green secretions with a bad odor.
Itching around the vagina or on the thighs.
Men (varies):
Urethritis.
Small gray/white vesicles on the exterior.
Infected individuals may be asymptomatic and still infectious.
Complications
Pregnancy: Pre-term delivery, low birth weight, and increased mortality.
Increased risk for HIV (men and women).
Cervical cancer.
Treatment
Single dose of metronidazole or tinidazole.
Increasing to 500mg metronidazole twice daily for seven days if initial treatment unsuccessful.
Contact and treatment of previous sexual partners, even if asymptomatic.
Prevention
Safe sex practices.
Parasite can infect areas not covered by a condom, so not 100% effective.
Treatment of pregnant mother with a single dose of metronidazole (NOT tinidazole).
Human Immunodeficiency Virus (HIV)
Characteristics
Retroviridae family.
Two copies of ss +RNA packed with reverse transcriptase enzymes.
Icosahedral capsid with envelope.
Two spikes: gp120 (attachment) and gp41 (fusion with host plasma membrane).
Two types:
HIV-1
HIV-2 (Develops slowly, Less infectious during early stages.)
History
Most likely jumped from chimpanzees to humans via bush meat in west-central Africa.
1981: First U.S. report of a syndrome involving opportunistic infections related to immune deficiency.
Blood samples taken in 1959 from a man from the Congo showed that he was infected by HIV.
Scientists suspect that the disease actually emerged in the 1930s.
Transmission of HIV
Does not occur through sharing utensils, plates, or cups.
Saliva has natural inhibitors of the virus, though there is one documented case of transmission through deep kissing (French kissing).
Most Common Modes of Transmission:
Male-male sexual contact.
Male-female sexual contact.
Blood Transmission:
Historically a major problem. Now, all donations are tested.
Can be prevented with antiviral drugs early in pregnancy.
Associated with helper T-cells, macrophages, and dendritic cells.
Sexual transmission: CD4 T-cells associated with the mucosa of the genital tract.
Pathogenesis
The CD4 surface antigen allows communication with antigen-presenting cells.
CD4 (helper) T-cells are targeted by HIV.
Stages of AIDS
Stage 1: Acute
Incubation: 1-3 months.
Symptoms: Asymptomatic to acute flu-like illness (~3 days).
Seroconversion occurs (anti-HIV antibodies detectable in the blood).
Virus count in the blood is very high, and individuals are very infectious.
Stage II: Asymptomatic
Asymptomatic.
T-cell count is high.
May last 2-12 years.
Can transfer the virus to other individuals during this time.
Stage III: Chronic Disease
The number of viruses rises rapidly.
Increased antibody production against the virus.
T-cell count begins to plummet.
Antibody production decreases.
Symptoms include fatigue, weight loss, weakness, and opportunistic infections.
Stage IV: Full-blown AIDS
Persistent opportunistic infections.
Extreme weight loss and weakness.
T-cell count VERY low.
Extreme immunocompromised state causes death from usually harmless microorganisms.
HIV also causes a rare form of skin cancer called Kaposi’s sarcoma and produces a substance that may cause deterioration of brain function.
Treatment
Antiretroviral Therapy (ART)
Ideally, a combination of three different drugs.
Expensive.
Active treatment campaigns in many African nations (charity or governments).
In developed countries, the most common causes of AIDS-related deaths are now lifestyle-related, such as suicide, drug overdose, and liver disease.
Preventing the Spread of AIDS
Screening donated blood, tissue, and organs.
Administration of AZT to pregnant women prevents transmission of the virus to the fetus.
Delivering the baby via cesarean section lowers the risk of transmission through blood contact during birth.
Providing clean needles to drug addicts in big cities has helped reduce the spread of the virus among these populations.
Circumcision of males significantly reduces the risk of infection.
Safe sex education and practices:
Abstinence.
Limit the number of partners.
Use condoms (only 80% effective!!!!).