Bacterial Diseases

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Bacterial Diseases

• Lecture 10

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Cocci of Medical Importance
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General Characteristics of the Staphylococci

• Spherical cells arranged in irregular clusters
• Gram positive
• Common inhabitant of the skin mucous membranes
• Lack spores and flagella
• May have capsules
• 31 species

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Staphylococcus aureus

• grows in large, round, opaque colonies
• optimum temperature 37oC
• facultative anaerobe
• withstands high salt, extremes in pH, high
  temperatures
• produces many virulence factors

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Enzymes of S. aureus

• Coagulase
• coagulates plasma and blood
• produced by 97 of human isolates
• Hyaluronidase
• promotes invasion
• Staphylokinase
• digests blood clots
• Dnase
• digests DNA
• Lipases
• helps bacteria colonize oily skin
• Penicillinase
• inactivates penicillin

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Toxins of S. aureus

• hemolysins
• lyse RBCs
• Leukocidin
• damages cell membranes
• Enterotoxins
• act in the gastrointestinal tract
• exfoliative toxin
• separates epidermal layers
• toxic shock syndrome toxin (TSST)

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Epidemiology and Pathogenesis

• Present in most environments frequented by humans
• Readily isolated from fomites
• Carriage rate for healthy adults is 20-60
• mostly in anterior nares, skin, nasopharynx,
  intestine
• Predisposition to infection include
• poor hygiene and nutrition, tissue injury,
  preexisting primary infection, diabetes,
  immunodeficiency
• Increase in community acquired methicillin
  resistance
• MRSA

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Staphylococcal Disease

• Range from localized to systemic
• Localized cutaneous infections invade skin
  through wounds, follicles, or glands
• folliculitis
• superficial inflammation of hair follicle
• usually resolved with no complications but can
  progress
• furuncle
• Boil
• inflammation of hair follicle or sebaceous gland
  progresses into abscess or pustule
• carbuncle
• larger and deeper lesion created by aggregation
  and interconnection of a cluster of furuncles
• impetigo
• bubble-like swellings that can break and peel
  away
• most common in newborns

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Staphylococcal Disease

• Systemic infections
• osteomyelitis
• infection is established in the metaphysis
• abscess forms
• bacteremia
• primary origin is bacteria from another infected
  site or medical devices
• endocarditis possible

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Staphylococcal Disease

• Toxigenic disease
• food intoxication
• ingestion of heat stable enterotoxins
• gastrointestinal distress
• staphylococcal scalded skin syndrome
• toxin induces bright red flush, blisters, then
  desquamation of the epidermis
• toxic shock syndrome
• toxemia leading to shock and organ failure

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Other Staphylococci

• S. epidermidis
• lives on skin mucous membranes
• endocarditis, bacteremia, UTI
• S. hominis
• lives around apocrine sweat glands
• S. capitis
• live on scalp, face, external ear
• S. saprophyticus
• infrequently lives on skin, intestine, vagina UTI

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Streptococci

• Gram-positive spherical/ovoid
• cocci arranged in long chains
• Non-spore-forming, nonmotile
• Can form capsules slime layers
• Facultative anaerobes
• Do not form catalase, but have a peroxidase
  system
• Small, nonpigmented colonies
• Sensitive to drying, heat disinfectants
• 25 species

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Streptococci

• Lancefield classification system based on cell
  wall Ag
• 17 groups (A,B,C,.)
• Another classification system is based on
  hemolysis reactions
• b-hemolysis
• A,B,C,G some D strains
• a hemolysis
• S. pneumoniae others collectively called
  viridans
• ?-hemolysis
• Enterococcus faecalis
• does not induce hemolysis

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Human Streptococcal Pathogens

• S. pyogenes
• S. agalactiae
• viridans streptococci
• S. pneumoniae
• Enterococcus faecalis

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b-hemolytic S. pyogenes

• Most serious streptococcal pathogen
• Inhabits throat, nasopharynx, occasionally skin
• Produces C-carbohydrates, M-protein (fimbrae),
  streptokinase, hyaluronidase, DNase, hemolysins
  (SLO, SLS), pyogenic toxin

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S. pyogenes

• Humans only reservoir
• Transmission
• contact, droplets, food, fomites
• Skin infections
• pyoderma, impetigo, erysipelas
• Systemic infections
• strep throat, pharyngitis, scarlet fever
• Sequelae
• rheumatic fever, glomerulonephritis

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Group B S. agalactiae

• Regularly resides in human vagina, pharynx
  large intestine
• can be transferred to infant during delivery
  cause severe infection
• Most prevalent cause of neonatal pneumonia,
  sepsis, meningitis
• Pregnant women should be screened treated
• wound and skin infections endocarditis in
  debilitated people

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Scope of Clinical Disease

• Skin infections
• Impetigo (pyoderma)
• superficial lesions that break and form highly
  contagious crust
• often occurs in epidemics in school children
• associated with insect bites, poor hygiene, and
  crowded living conditions
• Erysipelas
• pathogen enters through a break in the skin
• eventually spreads to the dermis and subcutaneous
  tissues
• can remain superficial or become systemic
• Throat infections
• Streptococcal pharyngitis
• strep throat

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Long-Term Complications

• Rheumatic fever
• follows overt or subclinical pharyngitis in
  children
• carditis with extensive valve damage possible,
  arthritis, chorea, fever
• Acute glomerulonephritis
• nephritis, increased blood pressure, occasionally
  heart failure
• can become chronic leading to kidney failure

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Enterococcus faecalis E. faecium

• Normal colonists of human large intestine
• Cause opportunistic urinary, wound, and skin
  infections, particularly in debilitated persons

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Viridans Group

• a-hemolytic streptococci
• Large complex group
• Most numerous widespread residents of the oral
  cavity
• also found in nasopharynx, genital tract, skin
• Not very invasive
• dental or surgical procedures facilitate entrance

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Viridans Group

• Bacteremia, meningitis, abdominal infection,
  tooth abscesses
• S. mutans produces slime layers that adhere to
  teeth
• basis for plaque
• involved in dental caries
• Most serious infection
• subacute endocarditis
• blood-borne bacteria settle grow on heart
  lining or valves
• preexisting heart disease at high risk
• receive prophylactic antibiotics before surgery
  or dental procedures

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S. pneumoniae

• Causes 60-70 of all bacterial pneumonias
• Small, lancet-shaped cells arranged in pairs and
  short chains
• Culture requires blood or chocolate agar
• Growth improved by 5-10 CO2
• Lack catalase peroxidases
• cultures die in O2

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S. pneumoniae

• All pathogenic strains form large capsules
• major virulence factor
• Causes pneumonia otitis media
• Vaccine available for high risk people

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S. Pneumoniae Epidemiology

• 5-50 of all people carry it as normal flora in
  pharynx
• Does not survive long outside of its habitat
• Pneumonia occurs when cells are aspirated into
  the lungs of susceptible individuals
• Pneumococci multiply
• induce inflammatory response
• Traditionally treated with penicillin G or V
• Increased drug resistance

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Cultivation and Diagnosis

• Gram stain of specimen
• presumptive identification
• a hemolytic
• Quellung test or capsular swelling reaction

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Family Neisseriaceae

• Gram-negative cocci
• Residents of mucous membranes of warm-blooded
  animals
• Genera include Neisseria, Moraxella,
  Acinetobacter
• 2 primary human pathogens
• Neisseria gonorrhoeae
• Neisseria meningitidis

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Neisseria

• Gram-negative, bean-shaped, diplococci
• none develop flagella or spores
• capsules on pathogens
• pili
• Strict parasites
• do not survive long outside of the host
• Aerobic or microaerophilic
• Oxidative metabolism
• produce catalase
• Pathogenic species require enriched complex media
  and CO2

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Neisseria gonorrhoeae

• Causes gonorrhea
• Virulence factors
• pili, other surface molecules, IgA protease
• Strictly a human infection
• In top 5 STDs
• Infectious dose 100-1,000
• Does not survive more than 1-2 hours on fomites
• Infection is asymptomatic in 10 of males and
  50 of females

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Gonorrhea

• Males
• urethritis, yellowish discharge, scarring
  infertility
• Extragenital infections
• anal, pharygeal, conjunctivitis, septicemia,
  arthritis

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Gonorrhea

• Females
• vaginitis, urethritis, salpingitis (PID) mixed
  anaerobic abdominal infection
• common cause of sterility ectopic tubal
  pregnancies

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Gonorrhea in Newborns

• Infected as they pass through birth canal
• Eye inflammation, blindness
• Prevented by prophylaxis after birth

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Diagnosis and Control

• Gram stain
• Gram-negative intracellular (neutrophils)
  diplococci from urethral, vaginal, cervical, or
  eye exudate
• 20-30 of new cases are penicillinase-producing
  PPNG or tetracycline resistant TRNG
• Recurrent infections can occur
• Reportable infectious disease

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Neisseria meningitidis

• Virulence factors
• capsule, pili, IgA protease
• 12 strains
• serotypes A, B, C, cause most cases
• Disease begins when bacteria enter bloodstream,
  pass into cranial circulation, multiply in
  meninges
• very rapid onset
• endotoxin causes hemorrhage and shock
• can be fatal
• Treated with penicillin, chloramphenicol
• Vaccines exist for group A and C

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Clinical Diagnosis

• Gram stain, CSF, blood, or nasopharyngeal sample
• Culture for differentiation
• Rapid tests for capsular antigen

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Gram-negative Bacilli of Medical Importance
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Gram-negative Bacilli

• Large, diverse group of non-spore-forming
  bacteria
• Wide range of habitats
• large intestines (enteric), zoonotic,
  respiratory, soil, water
• Most are not medically important
• true pathogens
• opportunists
• All have a lipopolysaccharide outer membrane of
  cell wall
• endotoxin

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Aerobic Gram-Negative Bacilli

• 1. Pseudomonas
• 2. Brucella
• 3. Francisella
• 4. Bordetella
• 5. Legionella
• 6. Alcaligenes

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1. Pseudomonas

• small gram-negative rods
• single polar flagellum
• produce oxidase catalase
• highly versatile metabolism

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Pseudomonas aeruginosa

• intestinal resident in 10 normal people
• resistant to soaps, dyes, quaternary ammonium
  disinfectants, drugs, drying
• Use aerobic respiration
• do not ferment carbohydrates
• Produce oxidase and catalase
• Many produce water soluble pigments
• Opportunistic

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Pseudomonas aeruginosa

• common cause of nosocomial infections in hosts
  with burns, neoplastic disease, cystic fibrosis
• complications include pneumonia, UTI, abscesses,
  otitis, corneal disease
• grapelike odor
• greenish-blue pigment (pyocyanin)
• multidrug resistant
• cephalosporins, aminoglycosides, carbenicillin,
  polymixin, quinolones

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2. Brucella

• Brucellosis, malta fever, undulant fever, Bang
  disease
• zoonosis transmitted to humans from infected
  animals
• tiny gram-negative coccobacilli
• 2 species
• Brucella abortus (cattle)
• Brucella suis (pigs)
• fluctuating pattern of fever
• weeks to a year
• combination of tetracycline
• rifampin or streptomycin
• animal vaccine available
• potential bioweapon

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3. Francisella tularensis

• causes tularemia
• zoonotic disease of mammals (particularly
  rabbits)
• endemic to the northern hemisphere
• transmitted by contact with infected animals,
  water dust or bites by vectors
• headache, backache, fever, chills, malaise
  weakness
• 10 death rate in systemic pulmonic forms
• intracellular persistence can lead to relapse
• gentamicin or tetracycline
• potential bioterrorism agent

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4. Bordetella pertussis

• minute, encapsulated coccobacillus
• causes pertussis or whooping cough
• communicable childhood affliction
• acute respiratory syndrome
• often severe, life-threatening complications in
  babies
• reservoir
• apparently healthy carriers
• transmission by direct contact or inhalation of
  aerosols

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Bordetella pertussis

• virulence factors
• receptors that recognize bind to ciliated
  respiratory epithelial cells
• toxins that destroy dislodge ciliated cells
• DTaP vaccine
• acellular vaccine contains toxoid other Ags

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5. Legionella pneumophila

• Legionellosis, Legionaires disease
• Motile rods
• widely distributed in water
• live in close association with amebas
• prevalent in males over 50
• nosocomial disease in elderly patients
• fever, cough, diarrhea, abdominal pain, pneumonia
  
• fatality rate of 3-30
• azithromycin

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6. Alcaligenes

• live primarily in soil water
• may become normal flora
• A. faecalis
• most common clinical species
• isolated from feces, sputum, urine
• occasionally associated with opportunistic
  infections
• pneumonia, septicemia, meningitis

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Enterobacteriaceae Family

• Enterics
• gram-negative bacteria
• many members inhabit soil, water, decaying
  matter
• all members are small, non-sporing rods
• facultative anaerobes
• grow best in air
• cause diarrhea through enterotoxins
• divided into coliforms (lactose fermenters) and
  non-coliforms (non lactose fermenters)

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Enterobacteriaceae Family

• Coliforms in Normal Flora
• Rapid lactose-fermenting enteric bacteria that
  are normal flora and opportunistic
• E. coli
• Enterobacter
• Serratia
• Klebsiella
• Hafnia
• Citrobacter
• Noncoliforms in Normal Flora
• Lactose-negative bacteria that are opportunistic,
  normal gut flora
• Proteus
• Providencia
• Morganella
• Edwardsiella

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Enterobacteriaceae Family

• True Pathogenic Enterics
• Salmonella typhi
• S. cholerae-suis
• S. enteritidis
• Shigella dysenteriae
• S. flexneri
• S. boydii
• S. sonnei
• Yersinia enterocolitica
• Y. pseudotuberculosis

• True Pathogenic Nonenterics
• Yersinia pestis

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Testing of Enterics

• miniaturized, multichambered tube
• inoculating rod pulled through length of tube
• carries an inoculum to all chambers

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Antigens Virulence Factors

• H
• flagellar Ag
• K
• capsule /or fimbrial Ag
• O
• somatic or cell wall Ag
• endotoxin
• exotoxins

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Coliform Organisms and Diseases Escherichia coli

• most common aerobic non-fastidious bacterium in
  gut
• _at_ 150 strains
• Most not infectious

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Escherichia coli

• enterotoxigenic E. coli
• causes severe diarrhea due to heat-labile toxin
  heat-stable toxin
• stimulate secretion fluid loss
• also has fimbrae
• enteroinvasive E. coli
• causes inflammatory disease of the large
  intestine
• enteropathogenic E. coli
• linked to wasting from infantile diarrhea
• Enterohemorrhagic E. coli
• Newest strain
• Can permanently damage kidney

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Escherichia coli

• pathogenic strains frequent agents of infantile
  diarrhea
• greatest cause of mortality among babies
• causes 70 of travelers diarrhea
• causes 50-80 UTI
• indicator of fecal contamination in water

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Other Coliforms

• Klebsiella pneumoniae
• normal inhabitant of respiratory tract
• large capsule
• cause of nosocomial pneumonia, meningitis,
  bacteremia, wound infections UTIs
• Enterobacter
• UTIs, surgical wounds

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Other Coliforms

• Serratia marcescens
• produces a red pigment
• causes pneumonia, burn wound infections,
  septicemia meningitis
• Citrobacter
• opportunistic UTIs bacteremia

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Noncoliform Lactose-negative Enterics

• Proteus
• Salmonella
• Shigella

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1. Proteus

• Swarms on surface of moist agar in a concentric
  pattern
• Causes UTI, wound infections, pneumonia,
  septicemia, infant diarrhea

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2. Salmonella

• Motile
• ferments glucose
• S. typhi
• typhoid fever
• ingested bacilli adhere to small intestine
• cause invasive diarrhea that leads to septicemia
• S. cholerae-suis
• pigs
• S. enteritidis
• 1,700 serotypes
• salmonellosis
• zoonotic
• gastroenteritis 2-5 days

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3. Shigella

• shigellosis
• incapacitating dysentery
• S. dysenteriae, S. sonnei, S. flexneri S.
  boydii
• produce H2S or urease
• Nonmotile
• nonencapsulated

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Shigella

• invades villus of large intestine
• can perforate intestine or invade blood
• enters Peyers patches instigates inflammatory
  response
• endotoxin exotoxins
• treatment
• fluid replacement ciprofloxacin
  sulfa-trimethoprim

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True Pathogenic Nonenteric Yersinia pestis

• tiny, gram-negative rod
• unusual bipolar staining capsules
• virulence factors
• capsular envelope proteins protect against
  phagocytosis foster intracellular growth
• coagulase

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Yersinia pestis

• sylvatic plague
• humans develop plague through contact with wild
  animals
• urban plague
• domestic or semidomestic animals or infected
  humans
• found in 200 species of mammals
• rodents harbor the organism but do not develop
  the disease
• flea vectors
• bacteria replicates in gut, coagulase causes
  blood clotting that blocks the esophagus
• flea becomes ravenous

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Pathology of Plague

• bubonic
• bacillus multiplies in flea bite, enters lymph,
  causes necrosis swelling in groin or axilla
• bubo
• septicemic
• progression to massive bacterial growth
• virulence factors cause intravascular coagulation
  subcutaneous hemorrhage purpura
• black plague
• pneumonic
• infection localized to lungs, highly contagious
• fatal without treatment

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Plague

• Treatment
• streptomycin, tetracycline or chloramphenicol
• Killed or attenuated vaccine

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Medically Important Gram-Positive Bacilli
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Medically Important Gram-Positive Bacilli

• Three general groups
• Endospore-formers
• Bacillus, Clostridium
• Non-endospore-formers
• Listeria, Erysipelothrix
• Irregular shaped and staining properties
• Corynebacterium, Proprionibacterium,
  Mycobacterium, Actinomyces, Nocardia

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Gram-positive spore-forming bacilli
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Bacillus

• gram-positive
• endospore-forming
• motile rods
• mostly saprobic
• aerobic catalase positive
• versatile in degrading complex macromolecules
• source of antibiotics
• primary habitat is soil
• 2 species of medical importance
• Bacillus anthracis
• Bacillus cereus

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Bacillus anthracis

• facultative
• large, block shaped rods
• central spores
• develop under all conditions except in the living
  body
• virulence factors
• capsule exotoxins

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Bacillus anthracis

• 3 types of anthrax
• Cutaneous
• spores enter through skin, black sore
• least dangerous
• Pulmonary
• inhalation of spores
• Gastrointestinal
• ingested spores
• treated with penicillin or tetracycline
• vaccine
• toxoid 6X over 1.5 years
• annual boosters

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Bacillus cereus

• common airborne dustborne
• grows in foods, spores survive cooking
  reheating
• ingestion of toxin-containing food
• causes nausea, vomiting, abdominal cramps
  diarrhea
• 24 hour duration
• no treatment
• spores abundant in the environment

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Clostridium

• gram-positive
• spore-forming rods
• anaerobic catalase negative
• 120 species
• oval or spherical spores produced only under
  anaerobic conditions
• cause wound tissue infections and food
  intoxications

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Clostridium perfringens

• causes gas gangrene in damaged or dead tissues
• 2nd most common cause of food poisoning,
  worldwide
• virulence factors
• toxins
• alpha toxin
• collagenase
• hyaluronidase
• DNase

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Pathology

• Not highly invasive
• requires damaged and dead tissue
• anaerobic conditions
• Conditions stimulate spore germination,
  vegetative growth and release of exotoxins
• Fermentation of muscle carbohydrates results in
  the formation of gas and further destruction of
  tissue

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Treatment and Prevention

• Immediate cleansing of dirty wounds, deep wounds,
  decubitus ulcers, compound fractures, and
  infected incisions
• Debridement of disease tissue
• Large doses of cephalosporin or penicillin
• Hyperbaric oxygen therapy
• No vaccines available

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Clostridium difficile-Associated Disease (CDAD)

• Normal resident of colon, in low numbers
• Causes antibiotic-associated colitis
• relatively non-invasive
• treatment with broad-spectrum antibiotics kills
  the other bacteria
• allowing C. difficile to overgrow
• Produces enterotoxins that damage intestines
• Major cause of diarrhea in hospitals
• Increasingly more common in community acquired
  diarrhea

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Treatment and Prevention

• Mild uncomplicated cases respond to fluid and
  electrolyte replacement and withdrawal of
  antimicrobials
• Severe infections treated with oral vancomycin or
  metronidazole and replacement cultures
• Increased precautions to prevent spread

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Tetanus

• Clostridium tetani
• Common resident of soil and GI tracts of animals
• Most commonly among geriatric patients and IV
  drug abusers
• neonates in developing countries

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Pathology

• Spores usually enter through accidental puncture
  wounds, burns, umbilical stumps, frostbite, and
  crushed body parts.
• Anaerobic environment is ideal for vegetative
  cells to grow and release toxin
• Tetanospasmin
• neurotoxin causes paralysis by binding to motor
  nerve endings
• muscles contract uncontrollably
• Death most often due to paralysis of respiratory
  muscles

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Treatment and Prevention

• Treatment aimed at deterring degree of toxemia
  and infection and maintaining homeostasis
• Control infection with penicillin or tetracycline
• and muscle relaxants
• Vaccine available
• booster needed every 10 years

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Clostridium botulinum

• Causes 3 diseases
• food poisoning
• spores are in soil, may contaminate vegetables
• improper canning does not kill spores they
  germinate in the can producing botulinum toxin
• toxin causes paralysis by preventing release of
  acetylcholine
• infant botulism
• caused by ingested spores that germinate
  release toxin
• wound botulism
• spores enter wound cause food poisoning symptoms

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Gram-Positive Regular Non-Spore-Forming Bacilli

• Medically important
• Listeria monocytogenes
• Erysipelothrix rhusiopathiae

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Listeria monocytogenes

• non-spore-forming gram-positive
• ranging from coccobacilli to long filaments
• 1-4 flagella
• no capsules
• resistant to cold, heat, salt, pH extremes bile
• primary reservoir is soil water
• can contaminate foods grow during refrigeration

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Listeria monocytogenes

• Listerosis
• immunocompromised patients, fetuses neonates
• affects brain meninges
• 20 death rate
• ampicillin trimethoprimsulfamethoxazole
• Prevention
• pasteurization cooking

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Erysipelothrix rhusiopathiae

• gram-positive rod
• widely distributed in animals the environment
• primary reservoir
• tonsils of healthy pigs
• enters through skin abrasion, multiplies to
  produce erysipeloid, dark red lesions
• penicillin or erythromycin
• vaccine for pigs

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Gram-Positive Irregular Non-Spore-Forming Bacilli

• Medically important genera
• Corynebacterium
• Proprionibacterium
• Mycobacterium
• Actinomyces
• Nocardia

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Corynbacterium diptheriae

• gram-positive irregular bacilli
• produce catalase
• 2 stages of disease
• Local infection
• upper respiratory tract inflammation
• sore throat, nausea, vomiting, swollen lymph
  nodes, pseudomembrane formation can cause
  asphyxiation
• Diptherotoxin production and toxemia
• target organs primarily heart and nerves

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Epidemiology and Pathology

• Reservoir of healthy carriers
• potential for diphtheria is always present
• Most cases occur in non-immunized children living
  in crowded, unsanitary conditions
• Acquired via respiratory droplets from carriers
  or actively infected individuals

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Corynbacterium diptheriae

• Diagnostic methods
• Pseudomembrane and swelling indicative
• Stains
• Conditions, history
• Serological assay
• Treatment
• Antitoxin
• Penicillin or erythromycin
• Prevented by toxoid vaccine series and boosters

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Propionibacterium acnes

• gram-positive rods
• aerotolerant or anaerobic
• nontoxigenic
• common resident of sebaceous glands
• causes acne

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Mycobacteria

• gram-positive irregular bacilli
• acid-fast staining
• strict aerobes
• produce catalase
• possess mycolic acids a unique type of
  peptidoglycan
• do not form capsules, flagella or spores
• grow slowly
• 2 medically important
• Mycobacterium tuberculosis
• Mycobacterium leprae

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Mycobacterium tuberculosis

• produces no exotoxins or enzymes
• contain complex waxes cord factor
• prevent destruction by lysosomes of macrophages
• transmitted by airborne respiratory droplets
• only 5 infected people develop clinical disease

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Primary TB

• infectious dose 10 cells
• phagocytosed by alveolar macrophages
• multiply intracellularly
• after 3-4 weeks immune system attacks, forming
  tubercles
• granulomas consisting of a central core
  containing bacilli surrounded by WBCs

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Secondary TB

• reactivation of bacilli
• tubercles expand drain into the bronchial tubes
  upper respiratory tract
• gradually patient experiences more severe
  symptoms
• violent coughing, greenish or bloody sputum,
  fever, anorexia, weight loss, fatigue
• untreated 60 mortality rate

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Extrapulmonary TB

• during secondary TB, bacilli disseminate to
  regional lymph nodes, kidneys, long bones,
  genital tract, brain, meninges
• these complications are grave

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Diagnosis

• in vivo or tuberculin testing
• X rays
• direct identification of acid-fast bacilli in
  specimen
• cultural isolation and biochemical testing

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Treatment of TB

• 6-24 months of at least 2 drugs from a list of 11
• one pill regimen called Rifater (isoniazid,
  rifampin, pyrazinamide)
• vaccine based on attenuated bacilli Calmet-Guerin
  strain of M. bovis used in other countries

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Mycobacterium leprae

• Hansens bacillus
• strict parasite
• slowest growing of all species
• multiplies within host cells in large packets
  called globi
• causes leprosy
• chronic disease that begins in the skin mucous
  membranes progresses into nerves

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Leprosy (Hansens Disease)

• spread through direct inoculation from leprotics
• 2 forms
• tuberculoid
• superficial infection without skin disfigurement
• damages nerves and causes loss of pain perception
• lepromatous
• deeply nodular infection
• causes severe disfigurement of the face
  extremities

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Diagnosing

• Combination of symptomology, microscopic
  examination of lesions, and patient history
• Detection of acid-fast bacilli in skin lesions,
  nasal discharges, and tissue samples

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Treatment and Prevention

• Treatment by long-term combined therapy
• Prevention requires constant surveillance of high
  risk populations
• WHO sponsoring a trial vaccine

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Actinomycetes Filamentous Bacteria

• Genera Actinomyces Nocardia are nonmotile
  filamentous bacteria related to mycobacteria
• Actinomyces sp
• responsible for diseases of the oral cavity
  intestines
• Nocardia brasiliensis
• causes pulmonary disease similar to TB

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Miscellaneous Bacterial Disease Agents
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Spirochetes

• Gram negative human pathogens
• Treponema
• Leptospira
• Borrella

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1. Treponema

• thin, regular, coiled cells
• live in the oral cavity, intestinal tract,
  perigenital regions of humans animals
• pathogens are strict parasites

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Treponema pallidum

• human is the natural host
• extremely fastidious sensitive
• cannot survive long outside of the host
• causes syphilis
• infectious dose is 57 organisms

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Pathogenesis and Host Response

• Spirochete binds to epithelium, multiplies, and
  penetrates capillaries.
• Moves into circulation and multiplies
• Untreated marked by stages
• Primary
• Secondary
• Tertiary
• Spirochete appears in lesions and blood during
  first 2 stages
• communicable

124
Stages of Syphilis

• Primary syphilis
• appearance of hard chancre at site of inoculation
• chancre heals spontaneously
• Secondary syphilis
• fever, headache, sore throat, red or brown rash
  on skin, palms and soles
• rash disappears spontaneously

125
Stages of Syphilis

• Tertiary syphilis
• about 30 of infections enter in tertiary stage
• can last for 20 years or longer
• neural, cardiovascular symptoms, gummas develop
• Congenital syphilis
• nasal discharge, skin eruptions, bone
  deformation, nervous system abnormalities

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Diagnosis and Treatment

• Stages of syphilis mimic other diseases
• Consider symptoms, history, microscopic and
  serological testing
• Treatment
• penicillin G

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2. Leptospira

• tight, regular individual coils with a bend or
  hook at one or both ends
• L. biflexa
• harmless, free-living saprobe
• L. interrogans
• causes leptospirosis
• zoonosis
• bacteria shed in urine
• infection occurs by contact
• targets kidneys, liver, brain, eyes
• sudden high fever, chills, headache, muscle
  aches, conjunctivitis, vomiting

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3. Borrelia

• Borrelioses
• transmitted by arthropod vector
• B. hermsii
• relapsing fever
• B. burgdorferi
• Lyme disease

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B. hermsii - Relapsing Fever

• mammalian reservoirs
• squirrels, chipmunks, wild rodents
• tick-borne
• after 2-15-day incubation, patients have high
  fever, shaking, chills, headache, fatigue
• Nausea, vomiting, muscle aches, abdominal pain
• extensive damage to liver, spleen, heart,
  kidneys, cranial nerves
• parasite changes immune system tries to control
  it
• recurrent relapses
• tetracycline

130
B. burgdorferi - Lyme Disease

• transmitted by ticks
• complex 2-year cycle involving mice deer
• nonfatal, slowly progressive syndrome that mimics
  neuromuscular rheumatoid conditions
• Symptoms
• 70 get bulls eye rash
• fever, headache, stiff neck, dizziness
• if untreated can progress to cardiac
  neurological symptoms, polyarthritis
• tetracycline, amoxicillin
• vaccine for dogs, human vaccine discontinued
• insect repellant containing DEET

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Curviform Gram-negative Bacteria

• 1. Vibrio
• Comma shaped rods with single flagella
• 2. Camphylobacter
• Short spirals with one or more flagella
• 3. Helicobacter
• Spirochete with spirals and endoflagella

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1. Vibrio cholera

• Cholera
• top 7 causes of morbidity mortality
• ingested with food or water
• infectious dose 108

134
Vibrio cholera

• infects surface of small intestine, noninvasive
• cholera toxin causes electrolyte water loss
  through secretory diarrhea, resulting dehydration
  leads to muscle, circulatory, neurological
  symptoms
• Treatment
• oral rehydration, tetracycline
• vaccine

135
2. Campylobacter jejuni

• important cause of bacterial gastroenteritis
• transmitted by beverages food
• reach mucosa at the last segment of small
  intestine near colon
• adhere, burrow through mucus and multiply
• symptoms of headache, fever, abdominal pain,
  bloody or watery diarrhea

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3. Helicobacter pylori

• curved cells discovered in 1979 in stomach
  biopsied specimens
• causes 90 of stomach duodenal ulcers
• people with type O blood have a 1.5-2X higher
  rate of ulcers
• produces large amounts of urease

137
Medically Important Bacteria of Unique Morphology
and Biology

• 1. Rickettsias
• 2. Chlamydias
• 3. Mycoplasmas

138
1. Rickettsia

• obligate intracellular parasites
• gram-negative cell wall
• among the smallest bacteria
• nonmotile pleomorphic rods or coccobacilli
• ticks, fleas louse are involved in their life
  cycle
• bacteria enter endothelial cells cause necrosis
  of the vascular lining
• treat with tetracycline chloramphenicol

139
4 Types of Rickettsioses

• 1. epidemic typhus
• R. prowazekii carried by lice
• starts with a high fever, chills, headache, rash
• Brill-Zinsser is a chronic, recurrent form
• 2. endemic typhus
• R. typhi, harbored by mice rats
• occurs sporadically in areas of high flea
  infestation
• milder symptoms

140
4 Types of Rickettsioses

• 3. Rocky Mountain spotted fever
• R. rickettsii zoonosis carried by dog wood
  ticks
• most cases on eastern seaboard
• distinct spotted rash

141
4 Types of Rickettsioses

• 4. Ehrlichia genus
• contains 2 species of rickettsias
• tickborne bacteria
• Most humans recover rapidly
• 5 chronically ill patients die from disseminated
  infection

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Coxiella burnetti

• Q fever
• intracellular parasite
• produces an unusual resistant spore
• harbored by a wide assortment of vertebrates
  arthropods
• transmitted by air, dust, unpasteurized milk,
  ticks
• usually inhaled causing pneumonitis, fever,
  hepatitis
• tetracycline treatment
• vaccine available

143
Bartonella

• small gram-negative
• Fastidious, cultured on blood agar
• causes
• trench fever
• spread by lice
• cat-scratch disease
• lymphatic infection associated with a clawing
  injury by cats
• bacillary angiomatosus in AIDS patients
• tetracycline, erythromycin rifampin

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2. Chlamydia

• obligate intracellular parasites
• small gram-negative cell wall
• alternate between 2 stages
• elementary body
• small metabolically inactive, extracellular,
  infectious form
• reticulate body
• grows within host cell vacuoles

145
Chlamydia trachomatis

• trachoma
• attacks the mucous membranes of the eyes,
  genitourinary tract lungs
• ocular trachoma
• severe infection, deforms eyelid cornea, may
  cause blindness
• inclusion conjunctivitis
• occurs as babies pass through birth canal
• prevented by prophylaxis
• STD
• urethritis, cervicitis, scarring
• lymphogranuloma venereum
• disfiguring disease of the external genitalia
  pelvic lymphatics

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Chlamydia trachomatis
147
Other Chlamydia

• C. pneumoniae
• causes an atypical pneumonia
• serious in asthma patients
• C. psittaci
• causes ornithosis
• zoonosis transmitted to humans from bird vectors
• highly communicable among all birds
• pneumonia or flulike infection with fever, lung
  congestion

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3. Molliculites and Other Cell-Wall-Deficient
Bacteria

• Called mycoplasmas
• Naturally lack cell walls
• highly pleomorphic
• Require special lipids from host membranes
• Treated with tetracycline, erthyromycin

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Mycoplasmas

• M. pneumoniae
• primary atypical pneumonia
• pathogen slowly spreads over interior respiratory
  surfaces
• causes fever, chest pain and sore throat
• M. hominis and Ureplasma urealyticum
• weak sexually transmitted pathogens

150
Bacteria in Dental Disease

• oral cavity is a complex, dynamic ecosystem
• contains 400 species
• dental caries
• slow progressive infection of irregular areas of
  enamel surface

151
Bacteria in Dental Disease

• begins with colonization by slime-forming species
  
• Streptococcus
• cross adherence with Actinomyces
• process forms layer of plaque
• harbors masses of bacteria which produce acid
  that dissolves enamel
• If plaque is allowed to stay, secondary invaders
  appear
• Lactobacillus, Bacteroides, Fusobacterium,
  Porphyromonas, Treponema
• Acid dissolves tooth enamel

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Peridontal disease

• soft tissue disease
• plaque becomes calcified into calculus above and
  below the gingiva
• irritates tender gingiva causing inflammation
• gingivitis
• pockets between tooth gingiva are invaded by
  bacteria
• tooth socket may be involved
• peridontitis
• tooth may be lost