Microbial Diseases of the Urinary and Reproductive Systems

Chapter 26: Microbial Diseases: Urinary and Reproductive Systems

Learning Objectives

• Modes of Transmission and Epidemiology: Describe how infections of the urinary and reproductive systems are transmitted and their epidemiological data.
• Microbial Pathogens: Discuss bacterial, viral, fungal, and protozoan diseases affecting the reproductive system.
• Normal Microbiota: Describe the normal microbiota found in the upper urinary tract, male urethra, female urethra, and vagina.
• Portals of Entry: Identify portals of entry for microbes into both the female and male reproductive systems.
• Antimicrobial Features: List the antimicrobial features present within the urinary system.
• Structures: Name the key structures related to the urinary and reproductive systems.

Structure and Function of the Urinary System

• The urinary system serves several critical functions:
  • Regulates the chemical composition and volume of blood.
  • Excretes nitrogenous wastes and excess water, including ammonia, urea, and uric acid.
• The reproductive system has two primary roles:
  • Produces gametes necessary for reproduction.
  • Supports the development of a growing embryo (specifically in the female).
• Microbial Diseases: These diseases can either arise from external microbes or opportunistic infections from normal microbiota.

Structure and Function of the Urinary System

• Components:
  • 2 Kidneys
  • 2 Ureters
  • 1 Urinary Bladder
  • 1 Urethra
• Infection Prevention Mechanisms:
  • Valves in ureters prevent the backflow of urine to the kidneys.
  • The acidity of urine helps inhibit microbial growth.
  • Mechanical flushing occurs during urination, which helps remove microbes.

Structure and Function of the Reproductive Systems

Female Reproductive Organs

• Comprises:
  • 2 Ovaries
  • 2 Uterine (Fallopian) Tubes
  • Uterus (including the cervix)
  • Vagina
  • External Genitals (vulva) including labia majora and labia minora.

Male Reproductive Organs

• Comprises:
  • 2 Testes
  • System of ducts including:
  • Epididymis
  • Ductus (Vas) Deferens
  • Ejaculatory Duct
  • Urethra
  • Accessory glands such as the Seminal Vesicle and Prostate Gland.
  • Penis.

Normal Microbiota of the Urinary and Reproductive Systems

• Normal Urine: Is not sterile; it contains microbiota towards the end of its passage.
• Predominant Vaginal Microbes:
  • Lactobacilli:
  • Produce hydrogen peroxide (H₂O₂) and lactic acid, contributing to an acidic pH (3.8 - 4.5).
  • Growth is promoted by estrogen (sex hormones).
  • Other microbes include Streptococci, anaerobes, and some gram-negative bacteria.
  • Candida albicans (yeast) is also commonly found.
• Male Urethra:
  • Introduces bacteria into semen, containing microbes such as Propionibacterium, Corynebacterium, and Pseudomonas.

Bacterial Diseases of the Urinary System

Key Conditions:

• Urethritis:
  • Inflammation of the urethra.
• Cystitis:
  • Inflammation of the urinary bladder.
• Ureteritis:
  • Infection of the ureters.
• Pyelonephritis:
  • Inflammation of one or both kidneys.
• Epidemiology:
  • Annually, there are approximately 8 million urinary tract infections (UTIs), with many cases attributed to Escherichia coli.

Cystitis

• Common Causes:
  • Primarily caused by E. coli and Staphylococcus saprophyticus.
• Symptoms:
  • Dysuria (difficult or painful urination).
  • Pyuria (presence of pus in urine).
• Demographics:
  • Eight times more prevalent in females due to the shorter urethra and proximity to the anal opening.
• Diagnosis:
  • Presence of >1,000 CFUs/mL of a single species and a positive leukocyte esterase (LE) test.

Pyelonephritis

• Causes:
  • 75% of cases are due to E. coli.
• Symptoms:
  • Fever and back/flank pain.
• Implications:
  • Can lead to bacteremia and formation of scar tissue in kidneys, which can be life-threatening.
• Diagnosis:
  • >100,000 CFUs/mL of a single species and a positive LE test indicating pus.

Bacterial Diseases of the Reproductive Systems

Overview of STIs

• Terminology:
  • STDs (Sexually Transmitted Diseases) have been renounced in favor of STIs (Sexually Transmitted Infections).
  • 20 million new cases are reported annually in the U.S., predominantly in individuals aged 15 to 24.
  • Many STIs are preventable with proper use of condoms.

Gonorrhea

• Causative Agent:
  • Infection caused by Neisseria gonorrhoeae, a gram-negative diplococcus.
• Incidence:
  • In 2016, the U.S. saw an increase to 130 cases per 100,000 people.
• Pathophysiology:
  • Attaches to epithelial mucosa via fimbriae, leading to mucosal inflammation and pus formation.
  • Can occur in pharyngeal and anal regions leading to gonorrhea in those areas.
• Symptoms:
  • In males: painful urination and purulent discharge; can lead to epididymitis.
  • In females: fewer symptoms but can result in pelvic inflammatory disease.
• Complications:
  • Untreated gonorrhea can disseminate causing systemic issues such as endocarditis, meningitis, and arthritis.
  • Can lead to ophthalmia neonatorum (infant blindness due to infections passed from mother to newborn).
• Immunology:
  • No adaptive immunity; exhibits antigenic variability, complicating the prevention and treatment.

Pelvic Inflammatory Disease (PID)

• Characteristics:
  • Extensive bacterial infection of female pelvic organs.
  • Typically polymicrobial, often involves N. gonorrhoeae and C. trachomatis.
• Symptoms:
  • Chronic abdominal pain.
  • Salpingitis, a severe form of PID affecting the uterine tubes; can result in scarring, infertility, or ectopic pregnancy.

Syphilis

• Causative Agent:
  • Caused by Treponema pallidum, a gram-negative spirochete.
  • Grows slowly in cell cultures.
• Transmission:
  • Invades through mucosa or skin breaks into the bloodstream, inducing an inflammatory response.
• Epidemiology:
  • There has been an increasing trend in cases since 2001 in the U.S.
• Stages of Syphilis:
  • Primary Stage: Chancre forms at the infection site 3 weeks post-exposure, painless and highly infectious, disappears in 2 weeks.
  • Secondary Stage: Presents skin and mucosal rashes, primarily on palms and soles due to the inflammatory response.
  • Latent Period: No symptoms present.
  • Tertiary Stage: Years after latency; cell-mediated immune reactions can cause:
  • Gummatous syphilis: Gummas on various organs.
  • Cardiovascular syphilis: Weakened aorta.
  • Neurosyphilis: Affects the central nervous system, potentially leading to dementia.
  • Congenital Syphilis: Results in neurological damage to the fetus.

Bacterial Vaginosis

• Definition: Overgrowth of bacteria that disrupts the natural balance of vaginal microbiota.
• Causative Agent: Usually caused by Gardnerella vaginalis, which is a normal commensal of the vagina.
• Reactions:
  • Vaginitis: Inflammation due to infection; Vaginosis: imbalance with no inflammation.
• Indicators: pH above 4.5, a fishy odor (whiff test), and copious frothy discharge. Clue cells (vaginal epithelial cells covered with biofilm of Gardnerella vaginalis) are diagnostic.

Viral Diseases of the Reproductive Systems

Genital Herpes

• Causative Agent: Caused by herpes simplex virus type 2 (HSV-2).
  • In the U.S., approximately one in four individuals over the age of 30 are infected.
• Symptoms: Presence of painful vesicles on the genitals and painful urination; lesions typically heal within 2 weeks.
• Recurrences: Viruses remain latent in nerve cells which can reactivate under triggers such as menstruation, emotional stress, or illness.
• Management: No cure exists; suppression possible via medications like acyclovir, famciclovir, and valacyclovir.

Genital Warts

• Epidemiology: Approximately 5 million new cases reported annually in the U.S.
• Causative Agent: Caused by human papillomaviruses (HPV).
  • Visible warts caused by serotypes 6 and 11; serotypes 16 and 18 are implicated in cervical cancer.
• Impact: Cervical cancer causes around 4,000 female deaths annually in the U.S.; other cancers include anal and head & neck.
• Management: Treatment involves removal of warts; prevention can be achieved with quadrivalent or nine-valent HPV vaccines.

FDA-approved HPV Vaccines

Discussion on HIV and Hepatitis

• Question: Why are HIV and Hepatitis B/C viruses not discussed in this chapter?
  (Encouraging student engagement through a Think, Pair, Share exercise).

Fungal Diseases of the Reproductive Systems

Candidiasis

• Causative Agent: Caused by Candida albicans which typically grows on the mucosa of the mouth, intestines, and genitourinary tract.
• Pathogenesis:
  • Opportunistic overgrowth commonly due to factors such as antibiotic use, diabetes, and hormonal changes.
• Symptoms:
  • Oral candidiasis referred to as thrush and vulvovaginal candidiasis leading to vaginitis characterized by a yeasty, thick, whitish-yellow discharge.

Protozoan Diseases of the Reproductive Systems

Trichomoniasis

• Causative Agent: Caused by Trichomonas vaginalis, commonly referred to as Trich.
• Epidemiology: Very common STI with about 8 million cases annually in the United States.
• Pathogenesis: A normal inhabitant of the vagina that grows when acidity is disturbed.
• Symptoms:
  • In females: irritation accompanied by a profuse, frothy greenish-yellow discharge with a foul odor.
  • In males: typically asymptomatic but may experience burning and irritation.

Most Common Types of Vaginitis and Vaginosis

Comparison of Microbial and Symptoms