-
Medically Important Gram Positive Rods (Aerobic)
- Bacillus
- Corynebacterium
- Erysipelothrix
- Listeria
- Gardnerella
-
Bacillus Virulence Factors
-
Etiological Agent of Anthrax
Bacillus anthracis
-
Clinical Presentations of Anthrax
- Cutaneous
- Gastroenteritis
- Inhalation (100% fatality)
-
Clinical Presentations of B. cereus
- Gastroenteritis (mediated by enterotoxins)
- Ocular (rapid, progressive destruction following trauma)
-
Severity of B. Cereus Gastroenteritis
- Mild, self-limiting disease.
- N/V or diarrhea.
- Often ignored as food bug
-
Etiological Agent of Diphtheria
Corynebacterium diphtheriae
-
Diphtheroids
Non-pathogen species that often find their way into lab media
-
Microscopic Morphology of Erysipelothrix
Small, thin rods that form long filaments
-
Microscopic Morphology of Listeria
Small, paired coccobacilli
-
Erysipelothrix associated with human disease
E. rhusiopathiae
-
Erysipelothrix disease
Endocarditis
-
#1 Cause of mortality in foodborne illnesses
Listeria monocytogenes
-
Methods of transmission for Listeria monocytogenes
Contaminated food (unpasteurized milk), vertical, zoonotic.
-
Medically Important Gram Positive Rods
- Actinomyces
- Clostridium
- Lactobacillus
- Mobiluncus
- Propionibacterium
-
Gram positive Rod genus with filamentous morphology
Actinomyces (resembles hyphae)
-
Actinomyces species most commonly involved in human infections
A. israelii
-
Spore forming genera
Bacillus and Clostridium
-
Virulence of serotypes of Clostridium perfringens
5 serotypes, type A most responsible for human disease
-
Virulence factors of Clostridium perfringens
Arsenal of toxins known as lethal toxins. A-toxin (lecithinase)
-
Virulence factors of C. tetani
- hemolysin
- neurotoxin (tetanospasmin) responsible for clinical expression of tetanus by blocking neurotransmitter release
-
Clinical presentations of botulism
- Food borne (foods with low acid content)
- Infant botulism (used to be caused by giving kids honey)
- Wound botulism
-
Virulence factors of C. diff
Enterotoxin and Cytotoxin
-
Clinical presentations of Lactobacillus
Transient bacteremia, endocarditis, opportunistic septicemia
-
Gram staining of Mobiluncus and Gardnerella
On gram stain appear Gram - or gram variable, but have a gram positive cell wall, show antibiotic susceptibility similar to Gram + bacteria, lack endotoxin.
-
Colonization of Mobiluncus and Gardnerella
Colonize female genital tract in large numbers
-
Most medically important species of Propionibacterium
P. acnes
-
medically important species of Clostridium
- C. perfringens
- C. botulinum
- C. tetani
- C. dificile
-
C. perfringens
- What disease(s) does the microbe cause?
- Mild gastroenteritis to severe myonecrosis (gas gangrene)
- Where (ie site in the body) is the disease?
- Wound that becomes infected w/ spores from environment
- Why is the microbe able to cause disease?
- Virulence factors: arsenal of toxins known as “lethal toxins”
- Ά-toxin ( a lecithinase) is produced in large quantities by type A strains of C. perfringens
- Lecithinase: lyses all types of cells
- Form spores
- Who is at risk for the disease?
- People w/ open wounds
- How is the disease transmitted?
- Grows easily and rapidly in vitro
- 5 serotypes: A-E
- Type A responsible for most human disease
-
C. tetani
- terminal endospore is characteristic (looks like drumstick)
- difficult to grow in vitro
- What disease(s) does the microbe cause?
- Tetanus
- Muscle spasms/ paralysis
- Where (ie site in the body) is the disease?
- GI tract?
- Why is the microbe able to cause disease?
- Spore-former
- hemolysin
- neurotoxin (tetanospasmin): responsible for clinical expression of tetanus by blocking neurotransmitter release
- Who is at risk for the disease?
- tetanus now rarely seen in developed countries but still a major problem in developing countries
How is the disease transmitted?
-
C. botulinum
- What disease(s) does the microbe cause?
- Botulism
- bacterium divided into 4 groups: I, II, III, IV
- likely represents 4 different species
- 3 clinical presentations of botulism:
- food borne: improper canning; food w/ low acid content
- infant botulism: caused by giving kids honey– normal flora not fully developed yet
- Kids can get incidentally by inhalation from soil
- wound botulism: contaminated wounds
- Where (ie site in the body) is the disease?
- GI tract?
- Why is the microbe able to cause disease?
- commonly found in soil but disease is rare
- disease mediated by neurotoxin:
- these toxins identified as types A-G; are antigenically distinct
Who is at risk for the disease?
- How is the disease transmitted?
- Food
- Soil/ inhalation
- Contaminated wounds
-
C. difficile
- What disease(s) does the microbe cause?
- etiologic agent of antibiotic associated colitis (AAC)
- C diff= most common cause of AAC; other spp of Clostridium can cause AAC too
- Clinical presentation: have “double-digit” stools (>10 episodes); feel poorly overall
- Where (ie site in the body) is the disease?
- GI tract
- Why is the microbe able to cause disease?
- normal GI flora in some; disrupted by antibiotics
- virulence factors: two major toxins
- toxin A: enterotoxin
- toxin B: cytotoxin
- spore formation allows organism to survive in hospital environment
- Who is at risk for the disease?
- like MRSA, increasing presence in community outpatient populations
- How is the disease transmitted?
- Nosocomial, opportunistic
-
Describe the virulence factors associated with species of Clostridium.
Gram positive rods that colonize skin and mucosal surfaces
- C. diff
- virulence factors: two major toxins
- toxin A: enterotoxin
- toxin B: cytotoxin
- spore formation allows organism to survive in hospital environment
- C. botulim
- commonly found in soil but disease is rare
- disease mediated by neurotoxin:
- these toxins identified as types A-G; are antigenically distinct
- C. tetani
- Spore-former
- hemolysin
- neurotoxin (tetanospasmin): responsible for clinical expression of tetanus by blocking neurotransmitter release
- C. perfringens
- Virulence factors: arsenal of toxins known as “lethal toxins”
- Ά-toxin ( a lecithinase) is produced in large quantities by type A strains of C. perfringens
- Lecithinase: lyses all types of cells Form spores
-
Identify the medically important species of Bacillus.
- B. anthracis:
- etiologic agent of anthrax
- anthrax has 3 clinical presentations:
- cutaneous
- Gastroenteritis: relatively rare
- Inhalation: mortality rate 100%
- Classic sign= wide mediastinum
- B. cereus:
- two clinical presentations:
- gastroenteritis:
- More common
- mediated by enterotoxins
- ocular:
- Keratoconjunctivitis
- trauma→ rapid, progressive destruction
-
Discuss the epidemiology of B. anthracis and B. cereus.
genus of large Gram positive rods
- B. anthracis
- What disease(s) does the microbe cause?
- etiologic agent of anthrax
- anthrax has 3 clinical presentations:
- cutaneous: ulcers w/ lymphadenopathy
- Gastroenteritis: relatively rare
- Inhalation: mortality rate 100%
- Pneumonia and septicemia
- Classic sign: wide mediastinum
- Where (ie site in the body) is the disease?
- Skin, GI, respiratory
- Why is the microbe able to cause disease?
- endospores
- enterotoxins
Who is at risk for the disease?
- How is the disease transmitted?
- Airborne, touch
- Contaminated animal products
- B. cereus
- What disease(s) does the microbe cause?
- two clinical presentations:
- gastroenteritis:
- More common
- mediated by enterotoxins
- ocular:
- Keratoconjunctivitis
- trauma→ rapid, progressive destruction
- Where (ie site in the body) is the disease?
- GI tract, eyes
- Why is the microbe able to cause disease?
- endospores
- enterotoxins: heat stable toxin
Who is at risk for the disease?
- How is the disease transmitted?
- Contaminated food products
-
Describe the virulence factors associated with these species of Bacillus.
-
Describe the epidemiology of Listeria monocytogenes.
- Gram positive rods
- VERY COMMON
- Should always be on differential, esp. w/ immunocompromised pt.s
- like Erysipelothrix is widely found in animals
- worldwide distribution: soil, water, vegetation, variety of mammals, fish, fowl
- #1 CAUSE OF MORTALITY IN FOOD INDUSTRY
- What disease(s) does the microbe cause?
- asymptomatic carrier state (1-5%)
- mono-like sx
- meningitis, bacteremia, encephalitis
- in pregnant women: intrauterine death, premature labor, neonatal infection
Where (ie site in the body) is the disease?
- Why is the microbe able to cause disease?
- virulence factors:
- hemolysin
- listeriolysin O: avoid phagocytosis
- ability to survive in cold temperatures (1-40 degrees C)
- Who is at risk for the disease?
- uncommon and restricted to distinct immunocompromised populations: neonates, elderly, pregnant women, cancer/transplant patients
- Early presentation: babies get this but survive. Have abscesses
- Late presentation: babies get meningitis and poor prognosis
- How is the disease transmitted?
- human disease transmitted by contaminated (by animal feces) food (esp. unpasturized milk- soft cheese, cold cuts); vertical, zoonotic
-
Describe the virulence factors associated with L. monocytogenes.
- hemolysin
- listeriolysin O: avoid phagocytosis
- ability to survive in cold temperatures (1-40 degrees C)
-
Discuss the epidemiology of Corynebacteria.
- genus of Gram positive rods: often irregularly shaped (maybe club-shaped)
- grow readily on most laboratory media
- What disease(s) does the microbe cause?
- etiologic agent of diphtheria acute inflammation and necrosis toxemia-> myocarditis, neuropathy, paralysis
- Where (ie site in the body) is the disease?
- Very common skin contaminant
- Nasopharynx larynx
- Why is the microbe able to cause disease?
- Toxin production: toxin lethally interrupts prot synthesis in cells and has direct action on myocardium-> myocarditis, and on PNS-> neuropathy and paralysis
Who is at risk for the disease?
- How is the disease transmitted?
- Respiratory or direct contact w/ skin lesion
-
Describe the virulence factors associated with Corynebacterium diphtheriae.
Toxin production: toxin lethally interrupts prot synthesis in cells and has direct action on myocardium-> myocarditis, and on PNS-> neuropathy and paralysis
|
|
