Gram positive rod Flashcards
What are the gram positive rod species?
Bacillus spp
Clostridium spp
Corynebacterium diphtheriae
Listeria monocytogenes
Gram positive
Rod shaped
Spore-forming bacteria
Found in soil, water, wool, hair, air, and on vegetation
Bacillus
What are the two species under Bacillus?
Bacillus anthracis (encapsulated)
Bacillus cereus (motile and non capsulated)
Gram positive rod
spore forming
non motile
non haemolytic
depends on bacterial capsule and anthrax toxin complex
B. anthracis
Bacterial capsule - protects against phagocytosis and lysis
Anthrax toxin complex
a. Protective Antigen (PA) - entry of bacteria into host cell. binds to receptor on macrophage surface
b. Edema Factor (EF) - causes cellular edema within the target tissue and also inhibits neutrophil function
Lethal Factor (LF) - release of tumor necrosis factor-alpha and interleukin-1 by macrophages
Virulence factors of B.anthracis
What is the combination of oedema toxin?
PA and EF
What is the combination of lethal toxin?
PA and LF
Causes an increase in the cellular CAMP levels leading to cellular oedema within the target tissues
Edema toxin
Zinc metalloprotease inactivates mitogen-activated protein kinase (MAPK), causing impaired proliferation, survival, and inflammation in all cell types. Leads to multisystem dysfunction in the host.
Lethal toxin
What is oedema?
Small blood vessels leak fluid into nearby tissues.
Pitting is when it takes a long time for the skin to bounce back
Anthrax is a zoonic infection and is transmitted by inoculation, ingestion, and inhalation.
B. anthracis
Entry of spores through the skin or through fly bites.
Papule, vesicle, eschar.
Commonly found in farmers and in persons handling infected carcasses
Cutaneous anthrax
Ingestion of undercooked meat containing spores.
Abdominal pain and fever are the first symptoms, followed by nausea, vomiting, and diarrhea.
Very rare
Gastrointestinal anthrax
Wool sorters disease
Spores are ingested by alveolar macrophages and are carried to the mediastinal lymph nodes
Does not cause pneumonia, but it causes haemorrhagic mediastinitis and pulmonary oedema
High fatality rate
Inhalational anthrax
Spore forming, motile, gram positive rods
normal inhabitants in soil, regularly isolated from foods such as grains, spices and dairy products
B. cereus
Most important pathogen known to cause food poisoning, “fried rice syndrome” due to improper storage after cooking.
B. cereus
Cytotoxic enzymes (cereolysin and phospholipase C) - tissue destruction
Heat stable and heat labile enterotoxin - emetic and diarrheal forms of food poisoning
B. cereus
How can Bacillus species be differentiated?
B. cereus agar
Resistance to Polymyxin B
Mannitol negative - blue colonies
Lecithinase positive - zone of precipitate around colonies
B. cereus
Gram positive spore-forming rods
Found as harmless saprophytes in the soil, water, and sewage
Normal enteric flora of humans and animals
Ability to produce endospores and produce potent exotoxin
Anaerobes but aerotolerant
Clostridium
What are the Clostridium species?
C. botulinum - motile
C. perfringens - non-motile
C. difficile - motile
C. tetani - motile
Causing gas gangrene and produces toxins and enzymes that lyse blood cells and destroy tissues, leading to soft tissue infections including cellulitis, fasciitis or supportive myositis.
C. perfringens
Produces a heat-sensitive enterotoxin that binds to receptors on the epithelium of the small intestine, leading to clostridial food poisoning intense diarrhea
C. perfringens
Produces necrotizing enteritis
Necrosis of the intestine, leading to bloody diarrhea, shock, and death
C.perfringens
May occur in hospitals
antibiotic associated diarrhea
pseudomembranous colitis
profuse diarrhea, foul-smelling, abdominal cramping, and fever
whitish plaques (pseudomembranes) form over intact colonic tissue
Faecal transplant
C. difficile
Toxin A - potent enterotoxin with slight cytotoxic activity
Toxin B - potent cytotoxic (cytopathic)
C. difficile
Fastidious, strict anaerobe, spore forming, Gram positive rods
Causative agent of botulism due to food poisoning
Flaccid paralysis - respiratory paralysis is the most common cause of death
C. botulinum
- week and dizzy
- blurred vision with fixed and dilated pupil
- diplopia (double vision)
- dysphagia (difficult to swallow), dry mouth
- weakness and inability to breathe
- constipation and abdominal pain
- death due to respiratory paralysis
C. botulinum
- classic or food botulism
- wound botulism
- infant botulism (milk powder / honey)
- inhalation botulism
C. botulinum
Strict anaerobes and forms bulging spore that appears as drumstick.
C. tetani
Tetanospasmin - potent heat labile toxin, prevents the release of neurotransmitter
Tetanolysin - heat stable haemolysin
Neurotoxin
Virulence factor of C. tetani
What is the difference between botulinum and tetanus toxin?
botulinum toxin: flaccid paralysis (stops muscle contraction)
tetanus toxin: spastic paralysis (uncontrollable muscle contraction)
An increased muscle tone and spasms, caused by the release of a neurotoxin called tetanospasmin
Tetanus
A spasm in which the head and heels are bent backwards and the body bowed forward. Deaths results from inability to breathe.
Opisthotonos
Seen in newborns when the mother lacks immunity and the umbilical stamp becomes contaminated with C. tetani spores.
Neonatal tetanus
Causes lockjaw
C. tetani
Gram positive pleomorphic rods, non-motile, and non-sporing that form angles with each other/club shaped, looking like Chinese letters arrangement. Aerobic or facultatively anaerobic
Corynebacterium diphtheria
Diptheria toxin (DT) - inhibits protein synthesis
Corynebacterium diphtheria
Causes diphteria, an acute upper respiratory illness
Corynebacterium diphtheria
Transmitted via airborne, site of infection on the epithelial cells of the tonsils and oropharynx, pathogenesis involves the diphtheria toxin that causes cell damage or death or necrosis and subsequent inflammation leading to thick, gray, adherent pseudomembrane over the tonsil and throat.
Diphtheria infection
Bull’s neck, conjunctivitis, severe myocarditis, and pharyngeal membane
Diphtheria
Gram positive short rods, singly or in pairs, facultative anaerobes, catalase positive, oxidase negative, and non-sporing. Motile by peritrichous flagella. Capable of growing and reproducing in host cells. Exhibit a narrow zone of Beta-haemolytic on blood agar.
Listeria monocytogenes
Cell attachment factors
Haemolysins
A protein that mediates actin-directed intracellular motility
L. monocytogenes virulence factor
causes neonatal disease can result in utero death or multiorgan abscesses
causes meningitis and septicemia in patients and pregnant woman with defects in cell-mediated immunity
influenza-like symptoms, and self limited gastroenteritis in healthy adult
L. monocytogenes
