Lecture 2 Flashcards
what are the 6 requirements for bacterial growth?
- energy source (sun, organic compounds, inorganic compounds)
- carbon source (organic carbon of CO2)
- major elements (C,H,O,N,S,P,K,Mg, Fe, Ca, Mn)
- trace elements (Mn, Co, Cu, Zn, Mo)
- growth factors (amino acids, vitamins, purines/pyrimidines)
- permissive conditions (temp, pH, osmotic pressure, oxygen)
based on their temp/rate of growth graphs, which bacteria would cause infections in animals?
mesophiles and thermophiles
which is more stable in high temperatures, saturated or unsaturated fatty acids?
saturated fatty acids
the normal pH of mammalian blood is usually between
7.3-7.5
bacteria are more tolerant of osmotic variation than eukaryotic cells because
they have cell walls
why is the presence of oxygen good for some bacteria and bad for others?
all cells have enzymes that react with oxygen which creates ozygen metabolites, and some bacteria can handle these toxic oxygen metabolites and others can’t. main metabolites produced are H2O2 and O2-
describe the difference between the following:
- obligate aerobes
- facultative anaerobes
- aerotolerant anaerobes
- obligate anaerobes
obligate aerobes: requires oxygen for aerobic respiration
facultative anaerobes: preforms aerobic resp when oxygen is available, but can survive by preforming anaerobic respiration
aerotolerant anaerobes: preforms anaerobic resp but can survive in presence of oxygen
obligate anaerobes: oxygen is lethal so they only preform anaerobic resp
describe the difference between sterilization, disinfection, and antisepsis
sterilization: all viable microorganisms are eliminated/destroyed including spores
disinfection: reduction of pathogenic organisms associated with inanimate objects to a level below that which causes an infection
antisepsis: inactivation or destruction by chemical means of microbes associated with the animal
what are the two methods of sterilization and list examples for each method
physical: heat, radiation, filtration
chemical: ethylene oxide, ozone, formaldehyde, gas plasma
what is the difference between boiling and pasturization?
boiling heats to boiling temperature but it is NOT the same as sterilization, it kills most bacteria but spores can be resistant
pasturization is heating of food to a degree that kills all potential human pathogens, ex) milk is heated to 72 degrees C for 15 seconds or 63 degrees for 30 minutes
what makes alcohol a good disinfectant?
what makes alcohol a not so good disinfectant?
it will denature proteins and dissolve lipids, kills many bacteria and viruses, no residual effect
spores are resistant to alcohol and ehtanol specifically can dehydrate tissue
how do you use bleach properly as a disinfectant? what are pros and cons of bleach?
use a 1:10 water to bleach ratio, and make sure there is at least 10 minutes of contact time
clean is a good disinfectant, but it doesn’t clean very well, can damage surfaces, and is inactivated in the presence of organic material
why is virkon a good disinfectant?
it is bactericidal, fungicidal, and virucidal, AND a detergent so it cleans and disinfects, it is non corrosive, needs 10 minutes of contact time
why is it important to know that organic material can inactivate many disinfectants?
you must clean up the JUNK before you disinfect! get rid of all the blood, poop, pee, pus, exudates, etc FIRST
what are the two classic examples of antiseptics used to clean an animals skin? how do they work?
povidone-iodine: interacts with bacterial proteins, nucelotides, and fatty acids to cause cell death
clorohexidine gluconate: interferes with bacterial cell membrane function causing cell death
what are 4 sources of bacteria you may encounter?
- infected animals with disease
- carrier aimals without clinical disease
- inanimate objects
- normal commensals
what are 3 examples of bacterial that free live in the soil, and 1 example of a bacteria that forms spores in the soil
free living in soil: pseudomonas, listeria, clostridia
spores: bacillus anthracis
list the 7 steps or chronology of microbial disease
- acquire access to a portal of entry
- encounter specific targets
- colonize target and get across host barriers
- spread locally and colonize new populations of target cells
- enter blood or lymph
- spread
- cause dysfunction and disease
list all the portals of entry for a bacteria
alimentary system, respiratory system, urogenital system, skin, eye, ear
is the infection via a bacteria a random process?
no! microbes will reach a site that has their target cells or substances suitable for their specific growth and replication and will colonize those targets and progress from there to cause disease
the initial host defenses are in 4 categories. list them and some examples in each
physical barriers: mucus layer in GI tract
chemical barriers: acid in the stomach
transport systems: mucociliary apparatus
immune system: mucus associated lymphoid tissue (MALT)
**bacteria must breack these to reach their targets and to allow for colonization
a bacterial infection can be assumed by non specific symptoms which are what
fever and neutrophilic leukocytosis (neutrophilia)
actual diagnosis of a bacterial infection can be ade by 5 different methods which are:
- visualization under microscope
- isolation of the organism
- detection of genetic material
- detection of a rise in antibody titre
- detection of specific cellular immune response
when you are collecting a sample for testing, what are some considerations?
get the sample before antibiotic therapy is started, use sterile containers and instruments, avoid dessication, get a good history, labell stuff, sent it to the lab ASAP, and store and ship at the correct conditions
why do you do a “selective culture” to isolate a bacteria?
because a swab or sample likely has lots of different bacteria on it, so to determine the presence of a specific pathogen, you need to do specific culture techniques to enhance the growth of the bacteria of most interest
what is a culture media?
broth that contains all nutrients and growth factors needed to grow bacteria, usually mized with a gel/agar
demonstration of bacteria from a normally sterile site without concurrent inflammation suggests what
contamination rather than an infection
briefly explain what each of these selective media are used for:
- blood agar
- macConkey agar
- hematin agar
- XLD agar
blood agar: detects presence of hemolysins
maConkey: selective for gram - and detect lactose fermentation
hematin: used for haemophilus spp and taylorella equigenitalis
XLD: colonies change color depending on the pH, yellow indicates lactose fermentation
what is a coagulase test?
used to differentiate bacteria species, a positive result will show coagulation or jelly like consistency
what test do you use to detect genetic material from a bacterial pathogen?
PCR DUH
what’s the diffreence between comventional PCR and RT PCR?
conventional used amplification and sequencing, RT uses amlification and detection (fluorescence)
does the presence of an antibody/titer indicate infection? why or why not?
no, because many bacteria are present normally within the host or in the environment, so you have lots of antibodies in you all the time!
what is the proper way to do titer/antibody testing to detect an infection?
do two serum samples collected 2 weeks apart and showing a 4x increase in antibody tier combined with clinical signs are indicative of infection
what is a caudal fold/tuberculin test?
used in cattle, you inject a small bleb of tuberculin intradermally into the tail and swelling 72 hours later is considered a response, indicating the cow has been exposed before to tuberculin
what is a gamma interferon test?
used to confirm the results of tuberculin test. T cells normall lease IFN gamma when exposed to specific antigens so the test is an ELISA for IFN gamma
