Important bacteria grouping Flashcards
does not have a cell wall
Mollicutes (Mycoplasma)
has two circular chromosomes
Leptospira
bacteria that are facultative intracellular bacteria
can survive extracellular or intracellular
Mycobacterium, Rhodococcus
Nausea, vomiting, fever> shock
Staphylococcus, streptococcus
enterotoxins
enterotoxin(superantigens)
Staphylococcus
Nosocomial infections are
Hospital acquired infections
Nosocomial infections:
Staphylococcus aureus, Clostridium difficile
Obligate intracellular pathogen:
They need a cell to replicate.
Eg. Rickettsia
Facultative intracellular pathogen: They can survive in extracellular and
intracellular locations.
Mycobacterium
Group Enterobacteriaceae
Present in water, soil environment
and the GI tract of humans and animals.
Coliform bacteria
E.coli gram negitive
is performed to evaluate
fecal contamination in drinking water
Coliform enumeration
2 membranes
Gram negitive
1 membranes
gram positive
Lipoteichoic acid (for antigenicity)
Gram positive
Lipopolysaccharide (LPS, virulence factor)
Gram Negative outer membrane
Mycolic acid (virulence factor)
Mycobacteria
Gram Negative stain color
pink
Gram positive stain color
purple bc of their thick peptidoglycan cell wall.
Teichoic acid on their
cell walls
Gram Positive
All bacteria contains
peptidoglycan
Lipid A component (endotoxin) of LPS can activate
immune system and exert harmful effects on the
host. Polysaccharide component contributes to
antigenicity
Lipid A component (endotoxin) of LPS can activate
immune system and exert harmful effects on the
host. Polysaccharide component contributes to
antigenicity
Acid Fast staining is due to presence of
mycolic
acid.
AcidFast positive bacteria have Gram positive
cell wall.
AcidFast positive bacteria have Gram positive
cell wall.
Pili / fimbriae
on surface
•Facilitate adherence to the host tissue through specific receptors.
•Contribute to antigenicity.
ecoli have
Capsule
Thick polysaccharide layer outside of the cell wall
- It is used for:
- Sticking cell together.
- As a food reserve.
- As protection against desiccation and chemicals.
- Helps bacteria to evade phagocytosis
is Mycolic acid a virulence factor
true
components of and LPS what do they do
- Lipid A component (endotoxin) can activate
immune system and exert harmful effects on the
host
2.Polysaccharide component contributes to
antigenicity
Endotoxin vs Exotoxins
Endotoxin: part of cell wall (lipopolysacride) and released when gram neg bacteria die heat stable low antigenicy
Exotoxins: protein released from cell heat liable high antigenicy
infection
is the invasion and multiplication of pathogenic microbes in an
individual or population.
Endotoxin vs Exotoxins action
Exotoxins:exert action of specific target cells (Neurotoxins, Leukotoxins ,
Enterotoxins.)
endotoxin:They can induce inflammation by stimulating the immune
system
Endotoxin vs Exotoxins action
Exotoxins:exert action of specific target cells (Neurotoxins, Leukotoxins ,
Enterotoxins.)
endotoxin:They can induce inflammation by stimulating the immune
system
some virulence factors Endotoxin vs Exotoxins
Superantigens
Superantigens
• Produced by pathogenic microbes (including viruses, mycoplasma,
and bacteria).
• Indiscriminate binding to MHC class II molecule on the antigen
presenting cells and T helper cell receptor.
• Result in polyclonal T cell activation and massive cytokine
release.
• Nausea, vomiting, fever> shock, (Staphylococcus, streptococcus
enterotoxins).
Processes used for transfer of virulence factors
Conjugation (direct contact between bacteria) is the process by which one bacterium( bacterium with a fertility factor) transfers genetic material to another through direct contact.
Transformation (uptake of genetic info form environment) is the genetic alteration of a cell resulting from the
direct uptake and incorporation of exogenous genetic material
from its surroundings and taken up through the cell membrane(s)
Transduction (virus) is the process by which DNA is transferred from one bacterium to another by a virus.
• Lysogenic conversion with Bacteriophages can result inbacteria with virulence factors, such as toxins or capsules
• Lytic=bacteria simply bust expelling viral dna
Transformation
uptake of random genetic info from environment
Transduction
virus
Lysogenic conversion with Bacteriophages can result inbacteria with virulence factors, such as toxins or capsules
• Lytic=bacteria simply bust expelling viral dna
What is the difference between an obligate intracellular bacteria and facultative intracellular bacteria? (And examples)
obligate intracellular bacteria: they need a host cell to replicate).
(Rickettsia, Chlamydia)
facultative intracellular bacteria: can survive extracellular or intracellular
(Mycobacterium, Rhodococcus)
obligate intracellular and facultative intracellular bacteria examples
obligate=Rickettsia, Chlamydia
facultative intracellular bacteria: Mycobacterium, Rhodococcus
How do you culture Bacteria
Liquid (Broth)Media
Eg. Nutrient broth, peptone broth, thioglycolate broth.
Solid (Agar) media
Eg. Trypticase soy agar with Blood
- Selective media
- PEA agar - Gram Positive selective media
- MacConkey agar- Gram negative selective media
- Hektoen Enteric Agar for Salmonella
What is antibody titer
Seroconversion: Antibody development after exposure to a pathogen or an antigen. Antibody Titer: Measurement of antibody level (quantity). Expressed as the reciprocal of the highest dilution of serum that positively reacts in a specific test. Higher the antibody response higher the titer. eg. a titer of 1280 in a test means that the serum sample remains positive when diluted 1:1280.
Higher the number for example 1/1280 more antibodies
β lactam antibiotics
β lactam antibiotics Eg: Penicillin, ampicillin, cephalosporins,
Inhibit peptidoglycan synthesis. Also bind and inhibit
a group of proteins called penicillin binding proteins
(involved in peptidoglycan synthesis).
Natural (true antibiotics): produced by bacteria or
fungus examples
(Streptomycin, penicillin, tetracycline).
Streptomycin and tetracycline:
Inhibit 30s subunit of bacterial ribosome.
Classification of antimicrobials
• Chemical structure
• Mode of action
Bactericidal-kills bacteria
Bacteriostatic-inhibits bacteria
• Type of antimicrobial activity
• Broad spectrum antibacterials are active against both Gram-positive
and Gram-negative organisms ( tetracyclines, chloramphenicol, fluoroquinolones,
cephalosporins).
• Narrow spectrum antibacterials have limited activity and are primarily only useful
against particular species of microorganisms(Gram positive or Gram negative).
• Spectrum of antimicrobial activity
Penicillin(β lactam antibiotics)
Inhibit peptidoglycan synthesis
What is the difference between aerobic, anaerobic, Facultative anaerobic and capnophilicbacteria?
• Oxygen required for growth
(aerobic, microaerophilic, capnophilic)
• •Oxygen not required or utilized for growth
(obligate anaerobe, aerotolerant anaerobe)
• •Oxygen not required but can be utilized for growth
(facultative anaerobe)
Oxygen not required or utilized for growth
anaerobe
Oxygen not required but can be utilized for growth
facultative anaerobe
Capnophilic bacteria
require oxygen and CO2
