5.2 Gram Positive Aerobic Rods 1 Flashcards
describe the physical appearance and susceptibility of gram positive aerobic rods
have a thick cell wall; sensitive to penicillin G
what is the habitat for bacillus
humans, animals, soil
gram-positive aerobic rods are important agents of (3)
zoonoses, septicemia and bacteremia
what is the habitat for listeria
throat and urogenital tract
what is the habitat for actinomyces
mouth flora
a cow presents with sudden death and bleeding from orifices… you suddenly suspect
B. anthracis
if you suspect B. anthracis, what are two important tests to perform and what do you never want to perform
1) Gram stain
2) Giemsa stain
Never perform a post-mortem (do not want to open the carcass)
how does B. anthracis appear after Gram and Giemsa staining
purple (G+) with a pink capsule; rod
where is B. anthracis commonly found
skin and soil
does B. anthracis form spores
Y; important virulence factor as it allows it to survive for decades in soil
T/F B. anthracis is zoonotic and reportable
T
B. anthracis spores are incredibly resistant because they are ___________
antiphagocytic
___ and ___ are two toxins created by B. anthracis that require ____ to be released
EF (edema factor); LF (lethal factor); PA (protective antigen)
what is EF and who produces it
edema factor; produced by B. anthracis; it is involved in the perinuclear endosomal membrane
what is LF and who produces it
lethal factor; B. anthracis; involved in apoptosis
what is PA and what does it do? who creates it?
protective antigen; creates a pore for transportation of EF and LF; B. anthracis
why is B. anthracis good at causing septicemia
really rapid proliferation; also causes a cytokine storm from macrophages
T/F B. anthracis infection is worst in birds
F; does not affect brids
how should you dispose of an animal that was infected with B. anthracis
incineration and use of formaldehyde
what 3 forms can anthrax take in humans
1) cutaneous
2) oral (and thus GI)
3) aerogenous (pulmonary)
what antibiotics are Bacillus spp. sensitive to
Penicillin G; aminopenicillins; macrolides
describe the nature of the anthrax vaccine… is it effective or not… why?
very effective since we can target the EF and LF toxins and since the bacteria is largely extracellular
T/F Listeria is zoonotic and reportable
F; zoonotic but not reportable
what is a feature of L. monocytogenes that is also similar to a gram positive aerobic cocci (and which one?)
hemolytic; like Streptococcus
what are features of L. monocytogenes survival (think about characteristics of it’s environment)
tolerates low pH and low temperature
what is psychrophilic
can grow in refrigerators
how can L. monocytogenes spread
feces, milk of ruminants with latent infection, contaminated food, contaminated silage
what is a unique feature about the way that L. monocytogenes can spread in the body
escapes the phagolysosome and spreads directly from cell to cell, allowing it to escape the immune response
what 3 antibiotics can we use to treat L. monocytogenes
penicillin, ampicillin, tetracyclines
how can we prevent listeriosis
quality check silage, vaccinate
what is THE opportunist pathogen of cattle
Trueperella pyogenes
what is unique about the morphology and the ideal environment of Trueperella pyogenes
pleiomorphic (rods and cocci form); facultative anaerobe
what animals can become infected with T. pyogenes
ruminants, pigs
what is characteristic of T. pyogenes (what do the infections look like)
purulent and mixed with anaerobic organisms
what makes T. pyogenes and its friends really great at infecting an animal
quorum sensing (cross-talk) and synergy between toxins; they work together to fuck shit up
what is the characteristic appearance of Actinomyces spp.
branching and filamentous; microcolonies surrounded by calcified macrophages (sulphur granules)
what disease in cattle is caused by actinomyces and what is it associated with (2)
lumpy jaw disease; trauma and teething
why is treatment of Actinomyces infection problematic and difficult
chronic and walled-off
describe the sequence of steps you would go through when you identify a gram positive cocci to how you would rule in/out S. aureus
after gram test shows G+ -> catalase test -> if positive, Staphylococcus; if negative, Streptococcus or Enterococcus -> if positive, then do coagulase test -> if positive, S. aureus; if negative; S. pseudointermedius or S. hyicus
when would you decide to perform MALDI-TOF
when you want to further characterise a bacteria -> species -> subspecies -> specific isolate/strain
what is the mass range for MALDI-TOF
2000-20,000 Da
what are 5 types of proteins you can identify using MALDI-TOF
1) ribosomal proteins
2) DNA binding proteins
3) heat shock proteins
4) cell division proteins
5) primary cell metabolism proteins
what are the 3 parts to MALDI-TOF
1) laser desorption ionization
2) mass spectrometry
3) comparison to reference database
what are some advantages of MALDI-TOF
- high throughput
- low exposure risk
- automated
- cost-effective
- rapid
- small footprint
- single colony/simple to prep the sample
what are some disadvantages of MALDI-TOF
- initial investment
- regulatory issues
- no susceptibility testing
- difficult with polymicrobial samples
- database entries
if a neonate does not receive colostrum, what type of bacterial infections might develop and why
extracellular infections; low antibodies means low humoral immunity, which is needed to fight extracellular infections
