I. Some Diseases of the Skin, Mucosa, Eyes, Wounds

A. Bacterial

1. Scalded Skin Infections (scalded baby syndrome) –Staphylococcus aureus; caused by exotoxins called exfoliatins; toxins travel through bloodstream causing upper skin layers to separate and peel; most common in infants; high fever present; septicemia and death can occur.

2. Abscesses, Boils, Sty – strains of staphylococci

3. Impetigo – caused by S. aureus or S. pyogenes; a highly contagious pyoderma (pus producing skin infection); occurs almost exclusively in children; easily treated with penicillin; usually heals without scarring, but pigment can be permanently lost.

4. Scarlet Fever – Streptococcus pyogenes; bacteria harbor a prophage that codes for production of erythrogenic (“red producing) toxin that causes the scarlet fever rash; can lead to rheumatic fever and kidney problems; was once a life-threatening illness; today's cases are mild.

5. Acne – caused by bacteria feeding on sebum(oil); Propionibacterium acne

6. Conjunctivitis (pink eye) – bacterial conjunctivitis is extremely contagious; can be caused by S. aureus, S. pyogenes, Haemophilus influenzae, Pseudomonas sp., Neisseria gonorrhoeae; conjunctivitis is more commonly caused by viruses; bacterial conjunctivitis is usually more pyogenic than viral.

7. Trachoma – Chlamydia trachomatis; trachoma means “pebbled or rough;” scarring of eyelids causes eyelashes to point inward; leading cause of preventable blindness worldwide; uncommon in US.

8. Hansen’s Disease (Leprosy) – Mycobacterium leprae; 2 forms of disease:

1.) tuberculoid – areas of skin lose pigment and sensation

2.) lepromatous – nodular form where a granulomatous response causes enlarged, disfiguring skin lesions called lepromas.

This is the only bacterium known to destroy peripheral nerve tissue; it “likes” cooler parts of body (nose, ears, fingers, etc.); as it progresses, disease erodes bone and it deforms hands and feet, pits develop in skull; until recently, patients were isolated in special hospitals; now, the disease can be arrested and people can live nearly normal lives (must sleep in separate bedrooms and cannot live with children).

9. Plague – Yersinia pestis; zoonosis; spread from infected rodents to humans by fleas; incidence of disease is low; bacilli travel in lymphatics to lymph nodes where they cause enlargements caused buboes (especially in armpits and groin); hemorrhages turn skin black (“Black Death”); deaths can be prevented with antibiotic treatment.

10. Tularemia – Francisella tularensis – zoonosis; reservoir: usually cottontail rabbits (number of causes rises during rabbit-hunting season); first isolated in Tulare County, CA in 1911; low incidence in US; disease is an occupational hazard for taxidermists; transmission: breaks in skin, bite from arthropod vector (tick, deer fly), inhalation of aerosols during skinning, consumption of contaminated meat; clinical signs: fever, severe headache, and buboes; one form can lead to a septicemia that resembles typhoid fever; vaccine does exist but frequent boosters are required.

11. Lyme Disease - Borrelia burgdorferi (spirochete); transmitted by deer ticks (Ixodes damini); white-tailed deer are a reservoir; develop flu-like symptoms; listed here because of the rash erythema chronicum migrans, which characterizes the disease (“bull’s-eye” rash – concentric rings around initial site of tick bite); other symptoms include arthritis, myocarditis, etc.; there is a vaccine for dogs; treat with antibiotics.

12. Burn infections – usually Pseudomonas aeroginosa

13. Wound infections

a. Gas Gangrene – Clostridium perfringens and other species; often a mixed infection; causes a “snap, crackle, and pop” sound in crepitant tissue (distorted tissue caused by gas bubbles).

b. Tetanus (lockjaw) – Clostridium tetani; spores from dirt are deposited deep in tissues (ex. puncture wound from stepping on nail); spores germinate in anaerobic environment; spastic paralysis results from exotoxin; paralysis leads to death; make puncture wounds bleed to flush out spores or flush with hydrogen peroxide (oxygen kills bacteria); disease treated with antitoxin.

B. Viral

1. Rubella (German Measles) - rash first appears on trunk

2. Measles (Rubeola) - febrile disease (causes fever); Koplik’s spots (white spots with central bluish specks) appear on upper lip and cheek mucosa; sometimes accompanied by conjunctivitis; rash begins on forehead and spreads to upper extremities, then trunk, and then lower extremities.

3. Chicken pox & shingles– already discussed

4. Small pox – already discussed

5. Warts – caused by papillomaviruses; some warts are malignant (cancerous) – some are associated with cervical cancer; grow on skin, genital and respiratory tracts, and oral cavity; transmitted by direct contact or my fomites; no cure for infected but warts can be removed - treated with cryotherapy (freezing) or caustic chemical agents.

6. Roseola – caused by a herpesvirus; seen in infants; several days of high fever, followed by a rash. (Be careful not to confuse with Rubella and Rubeola)

7. Fifth Disease (Erythema infectiosum) – virus destroys cells in bone marrow that give rise to blood cells; infected children have a bright red rash on the cheeks (“slapped cheek” rash) that may spread to the trunk and extremities, low grade fever; serious danger to those having chronic hemolytic anemia (ex. sickle cell anemia); virus can travel across the placenta; probably spread via respiratory route.

19^th century list of 5 childhood diseases: 1.) scarlet fever, 2.) rubeola, 3.) rubella,

4.) epidemic pseudoscarlatina (type of sepsis), and 5.) erythema infectiosum.

II. Urogenital Tract Infections & STD’s (Chapter 23)

Understand anatomy of urogenital system:

Urinary system: kidneys, ureters, bladder, urethra

Reproductive system:

Female: external genitalia, vagina, uterus, fallopian tubes, ovaries

Male: testes, penis, glands (produce seminal fluid), specific ducts (vas deferens, etc.)

A. Urogenital Diseases Usually Not Transmitted Sexually

1. UTI’s

Urethritis – inflammation of urethra Cystitis – bladder infections

Ureteritis – inflammation of ureter Pyelonephritis – kidney infection

Diagnosis: urinalysis; look for presence of nitrates & proteins.

Prevention: drink lots of water; urinate frequently; drink cranberry juice; urinate after sexual intercourse; avoid bubble bath, etc. that could irritate urethra; wipe front to back.

Treatment: antibiotics

2. TSS (Toxic Shock Syndrome) – S. aureus; incidence rose sharply in late 1970’s; rise associated with new superabsorbent, but abrasive, tampons, which were left in vagina for long periods of time; tampons caused small tears in vaginal wall and provided appropriate conditions for bacteria to multiply; organism enters blood and produce exotoxins; fever, low blood pressure (shock), and a red rash on the trunk; deaths are due to shock.

3. Vaginitis – usually caused by opportunistic organisms that multiply when the normal vaginal microflora are disturbed by antibiotics or other factors (pregnancy, use of contraceptive pills, menopause, douching); most bacterial infections caused by Gardnerella vaginalis.

B. STD’s (Sexually Transmitted Diseases)

1. Syphilis – Treponema pallidum (spirochete) – can be transmitted in saliva; see disease stages on p. 579; has periodic latent stages that make patients sometimes think that they do no have an STD; called the “great imitator” because its symptoms mimic those of so many other diseases; heart valves, blood vessels, and meninges can be affected; internal gummas destroy neural tissue, external gummas destroy skin tissue; mental illness accompanies neural damage; congenital syphilis occur when bacteria cross the placenta from mother to baby – infant may show signs such as notched incisors (Hutchinson’s teeth), a perforated palate, a deformed tibia (shin bone), an aged face with a saddle-shaped nose; treated with antibiotics

2. Gonorrhea (“flow of seed” a Greek physician in 130 AD mistook pus for semen) – Neisseria gonorrhoeae; can survive in dried masses of pus for 6-7 weeks; possess pili that allow them to attach to epithelial cells and to sperm; produce an endotoxin that damages the mucosa in reproductive tract and produce proteases that destroy IgA antibody; some people are asymptomatic; can be a carrier for 5-15 years postinfection; contraceptive pill alter vaginal conditions in favor of gonococcal growth; females can develop PID (pelvic inflammatory disease which leads to sterility); can also cause infections of pharynx, rectum, arthritis, blindness); treatable with antibiotics; silver nitrate administered to the eyes of newborns to prevent infections

3. Nongonococcal Urethritis (NGU) – most cases caused by Chlamydia trachomatis; prevalence is greater than any other STD; bacteria has an intracellular life cycle; symptoms are similar to gonorrhea, but milder; disease my be difficult to detect (80% of women and 10% of are asymptomatic); females can develop PID; infants can become infected when passing through birth canal; silver nitrate does nothing.

4. AIDS (Acquired Immune Deficiency Syndrome) – caused by HIV (Human Immunodeficiency Virus); most cases in U.S. caused by type I.

a. About the virus: This virus is called a retro virus (retro means backward). This virus uses the enzyme reverse transcriptase to make DNA from its RNA. This DNA can be integrated into the host cell's chromosome (now called a provirus). The provirus can stay in a latent stage in which it is replicated along with host cell DNA, causing the host cell no damage. AZT (azidothymidine), which is used against HIV, helps stop reverse transcription by targeting the enzyme reverse transcriptase.

b. Symptoms: infection typically causes flu-like symptoms, followed by an asymptomatic period of months or years during with the patient can transmit the disease; HIV specifically targets and destroys T helper cells and macrophage, thus affecting both the B cell and cytotoxic T cell responses, so person can die of a secondary infection; see page 520 for symptoms; most patients develop Kaposi’s sarcoma (tumors of blood vessels seen as purplish spots on skin, but occur throughout the body); AIDS has become the leading cause of death among 25 to 44 yr. olds!

c. Transmission: sexual contact (all forms), sharing of needles, blood transfusions, mother to infant; development of a vaccine is difficult due to high mutation rate of virus

5. Hepatitis B Virus (called “AIDS’ Twin” and serum hepatitis); transmission is the same; can create a carrier state (can’t ever donate blood); symptoms are similar to those of hep A, except that liver cells are frequently destroyed; some patients develop fulminant hepatitis, a condition of total liver failure; about half of infected people are asymptomatic; treatment relieves some symptoms, but does not cure disease; has been linked to liver cancer (increases chances of developing liver cancer by as much as 300 times); now part of routine infant vaccination.

6. Hepatitis C – not identified until 1989; mostly transmitted by blood or sexual contact; usually mild or inapparent infection, but can be severe in compromised individuals.

7. Herpes

a. herpes simplex type 1 – oral herpes; causes fever blisters or cold sores

b. herpes simplex type 2 – genital herpes

Oral can become genital and genital can become oral (usually due to oral sex).

Latency is a hallmark of herpes infections. More than 80% of the adult population worldwide harbors these viruses, but only a small proportion experience recurrent infections. Within 2 weeks of an active infection, viruses travel via sensory neurons to ganglia, where they become latent. They can be activated by fever, UV, stress, hormone imbalance, menstrual bleeding, trauma, etc. When reactivated, virus moves along neuron to the epithelial cells, where it replicates and causes lesion.

Neonatal herpes – babies become infected when passing through birth canal; rare, but can become infected in utero; neonates with disseminated infections usually have central nervous system damage and die within 10 days.

Disease can affect mucous membranes of mouth, eyes, lungs (herpes pneumonia); can also affect skin in places other than the mouth and genitals (a herpetic whitlow is a lesion on a finger that can result from exposure to oral, ocular, or genital herpes lesions).

Treatment: cannot eradicate virus, but acyclovir can reduce reoccurrence of lesions.

8. Cytomegalovirus (CMV) - Cytomegalic Inclusion Disease - virus is a member of the herpesvirus group; establishes a latent infection that can be reactivated; cells infected with virus swell and develop inclusion bodies; usually transmitted sexually, but also by the exchange of saliva and infected blood; infection in adults & healthy children is usually asymptomatic, but it may a cause brief, mononucleosis-like illness; can cause stillbirths, spontaneous abortions, birth defects; causes systemic infections in AIDS patients.