Bacteria Flashcards
Mycoplasma spp.
- no cell wall (therefore not treatable with penicillin)
- sterols in plasma membrane
- smaller than average bacteria (0.15-0.3 um diameter, size of poxvirus)
Spp. lacking cell wall (2)
- Mycoplasma
2. Ureaplasma
Spp. with flexible cell wall (3)
- Borrelia
- Leptospira
- Treponema
“BLT”
Spp. with rigid, filamentous cell wall (3)
- Actinomyces
- Myobacterium
- Nocardia
Obligate intracellular pathogens with rigid, simple, cell wall (5)
- Rickettsiaceae family
- Anaplasmataceae family (Ehrlichia/Anaplasma/Neorickettsia/Wolbachia)
- Coxiella genus
- Chlamydiaceae family (Chlamydia/Chlamydophila)
- Mycobacterium leprae
Gram +, cocci spp. (3)
- Staphylococcus
- Streptococcus
- Enterococcus
Gram +, rods spp. (6)
- Bacillus
- Clostridium
- Corynebacterium
- Lactobacilli
- Listeria
- Propionibacterium
Gram -, cocci spp. (2)
- Moraxella
2. Neisseria
Gram -, non-enteric rods spp. (8)
- Bartonella
- Bordetella
- Brucella
- Burkholderia
- Francisella
- Haemophilus
- Legionella
- Pseudomonas
Gram -, enteric rods spp. (10)
- Campylobacter
- Enterobacter
- Helicobacter
- Escherichia
- Salmonella
- Shigella
- Vibrio
- Klebsiella
- Proteus
- Yersinia
Streptococcus pneumoniae
- diplococci arrangement
Streptococcus pyogenes
- gram +
- streptococcal pharyngitis
- streptococci arrangement
- use of an afrimbrial adhesin (lipoteichoic acid)
- substratum: buccal epithelial cells
- evades complement/phagocytosis by secreting extraceullular protease (C5a peptidase) -> degrades C5a (inhibits neutrophil chemotaxis)
Staphylococcus spp.
- staphylococcus arrangement
- highly invasive bacteria
- evade macrophages and leukocytes -> Panton-Valentine leukocidin (i.e. in meticillin-resistant staph aureus)
- leukocidins: kill neutrophils and macrophages (alter phospholipid metabolism by ADP-ribosylaiton of a protein controlling phosphatidylinositol -> disruption of cellular activities)
Sarcina spp.
- tetrad arrangement
Coccobacillus
- “cop out” term
- short, fat rods
Pleomorphic
- name for young/old cells, not sure what characteristic shape they have
Acid fast staining spp.
- Mycobacterium spp.
2. Nocardia spp.
Ziehl-Neelsen Stain
- type of acid fast staining
- hot method
- hot basic carbolfuchsin (red stain) -> decolourize (acid-alkali) -> counterstain (methylene blue or malachite green)
acid-fast bacteria: red/pink
non acid-fast bacteria: blue/green
Kinyoun Stain
- type of acid fast staining
- cold method; same as Ziehl-Neelsen, but doesn’t require heating
Fluorochrome Stain
- type of acid fast staining
- auramine-rhodamine
fluorescent dyes-> decolourize-> counterstain (potassium permanganate, an oxidizing agent)
stained organisms appear yellow/green against black background
Bacillus anthracis
- anthrax
- exception: produces polypeptide capsule, not a glycocalyx
- haematogenous dissemination - disseminate to a different site within the host via blood (in plasma)
Zoonotic pathogens (4)
- Rickettsiaceae family
- Anaplasmataceae family
- Coxiella genus (C. burnetti)
- Chlamydophila genus (C. psittaci, C. pneumoniae)
Treponema pallidum
- syphillis
Francisella
- tularemia (rabbit fever)
Intracellular facultative bacteria (12)
Brucella spp. Bordetella pertussis Campylobacter spp. (Some) E. coli Group B Streptococcus Leigonella spp. Listeria monocytogenes Neisseria gonorrhoeae (meningitides) Salmonella spp. Shigella spp. Yersinia spp.
Extracellular bacteria (14)
Bacillus spp. Borrelia spp. Clostridium spp. Corynebacterium diphtheriae (Most) E. coli Group A Streptococcus Haemophilus spp. Klebsiella spp. Helicobacter spp. Proteus spp. Pseudomonas spp. Staphylococcus spp. Treponema spp. Vibrio cholerae
Streptococcus mutans
- tissue tropism/specificity for enaml - causes dental plaque
- catalase -
Streptococcus salivarius
- tissue tropism/specificity for tongue epithelial cells
- catalase -
Helicobacter pylori
- tissue tropism/specificity for gastric mucosa
- use of an afrimbrial adhesin (LPS or LOS)
- substratum: gastric epithelial cells
Campylobacter spp.
- tissue tropism/specificity for intestinal mucosa
Neisseria gonorrhoeae
- tissue tropism/specificity for urethral epithelium
Neisseria spp.
- have specific surface receptors to “grab” the host’s iron
- also act as chelators to keep the iron sequestered in the microbe
Bordetella pertussis
- tissue tropism/specificity for upper respiratory tract epithelium
- use of an afrimbrial adhesin (filamentous haemagglutinin, FHA)
- substratum: epithelial cells of upper respiratory tract
- **Can give FHA in a vaccine; if given prior to exposure, FHA will bind to receptor sites in the resp tract - actual bacteria cannot attach
Staphylococcus aureus
- tissue tropism/specificity for nasal membranes
- use of an afrimbrial adhesin (lipoteichoic acid)
- substratum: epithelial cells
Evasion of destruction by phagocyte - replicates and lives in phagocytic cells
- catalase + ; inactivates oxygen radicals and enables bacteria to survive inside phagolysosome
-class I (membrane acting/ superantigen) exotoxin; TSST-1 -> system-wide shock
Escherichia coli/ Enterotoxigenic Escherichia coli (ETEC)
- use of an adhesin/ligand: Type I pili (CFA)
- receptor: GM1 ganglioside (intestinal epithlium)
- secrete siderophores (low mw compounds that have a high affinity for iron - form a siderophore-iron complex)
Enterotoxigenic E. coli
- class III (intracellular) exotoxin; LT/ST Enterotoxin - Excessive watery diarrhoea
- exotoxin structure: A5B - two genes encode A&B subunits; noncovalently associated in stable complex
Salmonella typhimurium
- use of an afrimbrial adhesin (LPS or LOS)
- substratum: macrophages
- invasion strategy: injected into host cell via membrane ruffling
- post-invasion, spreads from epithelium to immediate underlying tissue. No further dissemination
Candida albicans
- use of an afrimbrial adhesin (mannans)
- substratum: epithelial mucosa
Listeria monocytogenes
- facultative intracellular pathogen
invasion strategy: injected into host cell via membrane ruffling
- internalin A on surface of bacterial cell binds to glycoprotein receptors on the host cell surface (i.e. epithelial cadherin, E-cadherin) -> mediates the attachment of Listeria to, and invasion of, hepatocytes, epithelial, and endothelial cells
Evasion of destruction by phagocyte - replicates and lives in phagocytic cells
- escapes phagolysosome via the action of class II (membrane damaging) exotoxin - Listeriolysin O (aka channel forming toxins - CFTs)
- forms pores in the phagolysosome
- also forms pores in cytoplasmic membrane - cytoplasmic contents leak out -> water enters cell (moves down concentration gradient) -> cell lysis
- haematogenous dissemination; disseminates to a different site within the host via mononuclear cells in the blood
Shigella spp.
- post-invasion, restricted at site of entry
infectious dose for shigella dysenteriae: 10 bacteria
Hyaluronidase
- dissemination enzyme (facilitate direct dissemination - In surface fluids, by flow of intestinal contents)
- breaks down hyaluronic acid of connective tissue
Streptokinase
- dissemination enzyme (facilitate direct dissemination - In surface fluids, by flow of intestinal contents)
- breaks down fibrin clots (converts plasminogen -> plasmin)
Collaginase
- dissemination enzyme (facilitate direct dissemination - In surface fluids, by flow of intestinal contents)
- breaks down collagen
Mechanisms used by bacteria to evade complement (4)
- Capsules
- Complement-binding proteins
- Proteases
- Host cell mimicry
Mechanisms used by bacteria to evade phagocytic killing (3)
- Capsules
- Type III Secretion systems
- Intracellular parasitism
Mechanisms used by bacteria to evade antigen processing (1)
- Interfere with MHC function and antigen processing
Mechanisms used by bacteria to evade antibodies (2)
- Ig-binding/inactivating proteins
2. Antigenic variation
Capsule-possessing bacteria/fungi (17)
***evasion of complement
Staphylococcus aureus Streptococcus pneumoniae Streptococcus pyogenes (group A) Streptococcus agalactiae (group B) Bacillus anthracis Bacillus subtilis Neisseria gonorrhoeae Neisseria meningitidis Haemophilus influenzae Escherichia coli Klebsiella pneumoniae Salmonella spp. Yersinia pestis Campylobacter fetus Pseudomonas aeruginosa Bacteroides fragilis Cryptococcus neoformans (yeast)
Chemical composition of capsule
***Varies from species to species - allows for serotyping, which is used to generate vaccines
components:
- polysaccharide
- polyribose ribitol phosphate
- hyaluronic acid; “host cell mimicry” - not seen as foreign by host macrophages -> bacteria avoids phagocytosis/opsonization
Pseudomonas aeruginosa
- gram -
- evades complement/phagocytosis by secreting extraceullular protease (elastase) -> inactivates C3b, C5a
Histoplasma capsulatum
Evasion of destruction by phagocyte - replicates and lives in phagocytic cells
- production of surface components that protects the bacterial cell within the phagolysosome
Legionella pneumophila
Evasion of destruction by phagocyte - replicates and lives in phagocytic cells
- inhibits phagosome-lysosome fusion
Biofilm
- collection of microorganisms that are attached to a surface, covered by a microbially-produced exopolymeric substance (EPS) aka the slime layer
- bacteria growing as biofilms can be significantly more resistant to antimicrobial agents (w/o considering the effects of other resistance mechanisms)
- can have multiple species living in a single biofilm
Klebsiella pneumoniae
- secretes siderophores (low mw compounds that have a high affinity for iron - form a siderophore-iron complex)
Biofilm-associated diseases: device-related infections (9)
- Ventricular derivations
- Contact lenses
- Endotracheal tubes
- Vascular central catheters
- Prosthetic cardiac valves, pacemakers and vascular grafts
- Peripheral vascular catheters
- Tissue fillers, breast implants
- Urinary catheters
- Orthopedic implants and prosthetic joints
Biofilm-associated diseases: tissue infections (10)
- Chronic otitis media, chronic sinusitis
- Chronic tonsilitis, dental plaque, chronic laryngitis
- Endocarditis
- Lung infection in cystic fibrosis
- Kidney stones
- Biliary tract infections
- Urinary tract infections
- Vaginosis
- Osteomyelitis
- Chronic wounds
Gram - bacteria
- inflict damage upon host via TOXIC STRUCTURES (LPS, endotoxin)
- activates almost every immune mechanism, as well as the clotting pathway, which together make LPS one of the most powerful immune stimuli known
Exotoxins
- protein toxins
- secreted into extracellular environment from live cells
- effects on the body are specific to the cell type; usually doesn’t cause fever
- highly potent (small amounts -> toxicity)
- can be used to make a toxoid
- gram + and gram - bacteria
Endotoxins
- lipopolysaccharide toxins (of cell wall); released via cell lysis
- only act as toxins under certain circumstances
- systemic effects, fever, inflammation
- high doses -> toxicity
- can’t be used to make a toxoid
- LPS of gram - bacteria
Toxoid
- a bacterial toxin (usually an exotoxin) whose toxicity has been inactivated or suppressed either by chemical (formalin, formaldehyde) or heat treatment
- immunogenicity is maintained (still antigenic); when used during vaccination, an immune response is mounted and immunological memory is formed against the molecular markers of the toxoid without resulting in toxin-induced illness
-currently: diphtheria toxoid (part of DTaP vaccine), tetanus toxoid
Vibrio cholerae
- exotoxin; Cholera toxin - excessive watery diarrhoea
- toxin structure: A5B - two genes encode A&B subunits; noncovalently associated in stable complex
- mechanism of action: ADP-ribosylator (toxin removes ADP-ribose group from NAD and transfers it to host cell protein, thereby inactivating it)
- infectious dose:
oral: 10^8 bacteria
oral + bicarbonate: 10^4 bacteria
Clostridium botulinum
- exotoxin; Botulism toxin - flaccid muscle paralysis (prevents neurosecretory Ach vesicles from docking/fusing with the nerve synapse plasma membrane of gangliosides, and prevents release of Ach)
Mechanism of action: Zinc metalloendoprotease - two linked fragments, which are proteolytically cleaved
- light chain (LC) - enzymatically active, zinc metalloprotease
- Heavy chain - binding and translocation
Clostridium tetani
- exotoxin; Tetanus Toxin - rigid/spastic muscle paralysis
- tetanus toxin blocks the release of inhibitory neurotransmitters glycine and gamma-Aminobutyric acid (GABA) at the presynaptic membrane of motor neurons
Mechanism of action: Zinc metalloendoprotease - two linked fragments, which are proteolytically cleaved
- light chain (LC) - enzymatically active, zinc metalloprotease
- Heavy chain - binding and translocation
- The rough surface of rusty metal merely provides a prime habitat for C. tetani endospores to reside in, and the nail affords a means to puncture skin and deliver endospores deep within the body at the site of the wound.
Clostridium perfringens
- class II (membrane damaging) exotoxin; Lecithinase (alpha toxin/phospholipase C) - type of cytotoxin
- membrane disruption -> indiscriminate lysis in various target cells
Corynebacterium diphtheriae
- class III (intracellular) exotoxin; diptheria toxin - pseudomembrane, systemic effects
- toxin structure: AB - single gene encodes for single peptide; post-translationally modified to A&B fragments which are covalently linked
- mechanism of action: ADP-ribosylator (toxin removes ADP-ribose group from NAD and transfers it to host cell protein (elongation factor 2, EF2) thereby inactivating it and halting protein synthesis)
Streptococci spp.
- class I (membrane acting/ superantigen) exotoxin; streptococcal pyrogenic exotoxin (SPE) -> rheumatic fever
Haemophilus influenzae
- dissemination to a different site within the host via CSF (cross blood-CSF junction via the choroid plexus)
Yersinia pestis
- dissemination to a different site within the host via lymphatics/ immune system cells (from tissue fluids -> lymphatic capillaries)
Transmission
Number of microorganisms shed and the period of time shed for
- microbial survival/stability in an environment is influenced by:
A) Microbial factors (sensitivity to UV light, ability to resist drying)
B) Extrinsic factors (humidity, temperature, exposure to disinfectants)
Infectious dose
Via oral route of infection, the number of organisms required for infection to occur
Mycobacterium tuberculosis
infectious dose: 1-10 bacteria
