Chapter 21: Miscellaneous Bacterial Agents of Disease

Spirochetes

Thin, regular, coiled cells

Where do spirochetes live in?

Live in the oral cavity, intestinal tract, perigenital regions in humans and animals

Pathogens for spirochetes

strict parasites with complex growth requirements

What do spirochetes require for cultivation?

live cells

Treponema Pallidum

• Spirochete

• causes syphilis

• Extremely fastidious and sensitive; cannot survive long outside of the host

Who are the natural hosts for Treponema Pallidum

Humans

Transmission of Treponema Pallidum

sexual and transplacental

Primary Syphilis

Spirochete binds to the epithelium, multiplies, and forms a lesion called chancre at the site of inoculation (commonly mouth and genitals)

Chancre

• fluid from it is highly contagious

• spontaneously heals as spirochete of syphilis moves into the blood

Secondary Syphilis

• Spirochete is multiplying in the bloodstream

• Rash forms on the skin, palms and soles with fever, headache and sore throat

• Rash does not hurt or itch and can persist for months

• The rash disappears spontaneously

Latency and Tertiary Syphilis

• After resolution of secondary syphilis, ~30% of infections enter a latent period that can last for 20 years or long

• If left untreated, tertiary syphilis forms

• Damage to multiple tissues and organs

• Gummas (painful swollen tumors) may develop

Congenital Syphilis

Treponema pallidum can pass through the placenta to the fetus (infection possible in any of 3 trimesters)

Symptoms of Congenital Syphilis

include nasal discharge, skin eruptions, bone deformation and nervous system abnormalities

Late form of Congenital Syphilis

gives rise to stigmata in the bones, eyes, inner ear, and joints, and causes the formation of Hutchinson’s teeth (notched, barrel-shaped)

Borrelia hermsii

• Relapsing fever

• Wild mammalian reservoirs – squirrels, chipmunks

• As the parasite changes, the immune system responds resulting in recurrent relapses

How is Borrelia hermsii transmitted?

by ticks

Symptoms of Borrelia hermsii

• After 2-15-day incubation, patients have high fever, shaking, chills, headache, and fatigue

• Nausea, vomiting, muscle aches, abdominal pain; extensive damage to liver, spleen, heart, kidneys, and cranial nerves

Treatment of Borrelia hermsii

treated with tetracycline

Borrelia burgdorferi

• Lyme Disease

• nonfatal, slowly progressive syndrome that mimics neuromuscular and rheumatoid conditions

How is Borrelia burgdorferi (lyme disease) acquired?

by ticks

Symptoms of Borrelia burgdorferi (lyme disease)

• 50-70% of patients get bull’s eye rash

• Fever, headache, stiff neck, and dizziness

What happens if Borrelia burgdorferi (lyme disease) is left untreated?

can progress to cardiac and neurological symptoms, polyarthritis

Curviform Bacteria

Gram-negative

Three groups share adaptations to survival in the intestine:

• Vibrio

• Campylobacter

• Helicobacter

What can Curviform bacteria cause?

enteric disease

Vibrio

comma-shaped rods, single polar flagellum

Campylobacter

short spirals or curved rods; one flagellum

Helicobacter

spirochete with tight spirals and several polar flagella

Vibrio cholerae

• Comma-shaped bacteria. Fermentative and grow on ordinary or selective media containing bile at 37°C

• cause of cholera

Epidemiology of Cholera

• Favored by warm, monsoon, alkaline, and saline conditions

• Pandemic pattern since 1961. El Tor biotype survives longer, more infectious

• In nonendemic areas can be spread by ingestion of contaminated food or water

• Cholera toxin

Cholera toxin

causes electrolyte and water loss through secretory diarrhea, “rice water stool”; resulting dehydration leads to muscle, circulatory, and neurological symptoms

Treatment of cholera

rehydrate and treat with Tetracycline

Other Vibrio Pathogens

Salt-tolerant inhabitants of coastal waters, associate with marine invertebrates

• Vibrio parahaemolyticus

• Vibrio vulnificus

Vibrio parahaemolyticus

gastroenteritis from raw seafood; symptoms similar to cholera

Vibrio vulnificus

gastroenteritis from raw oysters; serious complications in persons with diabetes or liver disease

Treatment of other vibrio pathogens (Vibrio parahaemolyticus and Vibrio vulnificus)

fluid and electrolyte replacement; occasionally antimicrobials

Helicobacter pylori

• A gastric pathogen

• Curved cells discovered in 1979 in stomach biopsied specimens

What does Helicobacter pylori causes?

• Causes 90% of stomach and duodenal ulcers; apparent cofactor in stomach cancer

• People with type O blood have a 1.5-2X higher rate of ulcers

what does Helicobacter pylori produce?

Urease which converts urea into ammonium and bicarbonate

Pathogenic bacteria with atypical morphology, physiology, and behavior include:

• Rickettsias

• Chlamydias

• Mycoplasmas

Rickettsias

intracellular pathogens that rely on an arthropod vector

Chlamydias

intracellular pathogens that alternate between elementary and reticulate bodies

• both obligate parasitic gram-negative coccobacilli

Mycoplasmas

Lack of cell wall and are highly pleomorphic

Specific Rickettsioses

1. The Typhus group

2. The spotted fever group

The typhus group

• Epidemic typhus

• Endemic typhus

Epidemic typhus

R. prowazekii carried by lice; starts with a high fever, chills, headache, rash; Brill-Zinsser is a chronic, recurrent form

Endemic typhus

R. typhi, harbored by mice and rats; occurs sporadically in areas of high flea infestation; milder symptoms

The spotted fever group

Rocky Mountain spotted fever

Rocky Mountain spotted fever

R. rickettsii zoonosis carried by dog and wood ticks; most cases in Southeast and on eastern seaboard; distinct spotted rash; may damage heart and CNS

Most common rickettsial infection in the U.S

Symptoms of Rocky Mountain spotted fever

• First symptoms are fever, chills, headache and a spotted rash appears in days

• Central nervous system can become involved and fatality rates are 20% if untreated

The Chlamydiaceae Family: Chlamydia trachomatis

Small, gram-negative, obligate intracellular parasites

In its life cycle, they alternate between two stages:

• Elementary body

• Reticulate body

Elementary body

small metabolically inactive, extracellular, infectious form released by the infected host

Reticulate body

noninfectious, actively dividing form, grows within host cell vacuoles

chlamydial diseases of the eye

• Ocular trachoma

• Inclusion conjunctivitis

Ocular trachoma

severe infection, deforms eyelid and cornea, may cause blindness

Inclusion conjunctivitis

occurs as baby passes through birth canal

how is inclusion conjunctivitis prevented?

by prophylaxis

Sexually Transmitted Chlamydial Diseases

• Chlamydiosis

• Nongonococcal urethritis (NGU)

• Pelvic inflammatory disease (PID)

Chlamydiosis

Most prevalent STD. Long term reproductive damage. Asymptomatic in women (70%) and male (10%)

Nongonococcal urethritis (NGU)

• in males

• Inflammation of the urethra. Mimics gonorrhea, yet do not involve gonococci

Pelvic inflammatory disease (PID)

• in women

• Cervicitis with a white drainage, endometritis, and salpingitis

Cell-Wall-Deficient Bacteria

Mycoplasmas- naturally lack cell walls, highly pleomorphic

Mycoplasma pneumoniae

primary atypical pneumonia; pathogen slowly spreads over interior respiratory surfaces, causing fever, chest pain, and sore throat (“walking pneumonia”)