Microbiology Final Flashcards
What bacteria causes Thrush in horses?
Fusobacterium
What is Thrush?
An infection of the frog of the hoof.
How do horses get thrush?
Packed mud/manure creates an anaerobic environment.
How do you prevent & treat Thrush?
Keep feet picked out. Topical antibiotics
What 2 bacteria causes Foot Rot in cattle and sheep?
Fusobacterium & Bacteroides
Define: antibiotic
Drugs that act on bacteria.
What is another name for antibiotic?
Antimicrobial
Define the 2 spectrums of antibiotics.
Broad spectrum antibiotics are effective on some Gram (+) and some Gram (-).
Narrow spectrum antibiotics are effective on either some Gram (+) bacteria or some Gram (-) bacteria.
Define: bactericidal
antibiotic that kills bacteria
Define: bacteristatic
antibiotic that inhibits the replication of bacteria.
What does a bacteristatic antibiotic rely on?
It relies on the host’s immune system to clear up the existing population.
What are the 5 Mechanisms of Action (M of A) or 5 ways that antibiotics do their job?
- Inhibit cell wall synthesis (Cidal, Penicillen).
- Alter cell membrane permeability (Cidal, polymyxins–antibiotic oitments)
- Inhibit protein synthesis (Static, Tetracycline)
- Inhibit NA synthesis (Static, metronidazole–Flagyl)
- Interfere with a Metabolic Pathway (Static or Cidal, Sulfonamides)
What are the 3 main reasons antibiotics fail?
Microbiological, Drug, Host
What are the 7 non-enteric GNROD genuses?
Brucella, Bordetella, Pasteurella, Moraxella, Francisella, Pseudomonas,Campylobacter
What are the 7 Clostridium species?
botulinum, tetani, perfringens, septicum, chauveoi, novyi, haemolyticum
What does Yersinia pestis causes?
The Plague
What is the result of an Oxidase test on Non-Enteric GNRODs?
Oxidase (+)
What are the 7 Microbiological reasons ab don’t work?
1) Well established infections (work best if treated early on)
2) Abscess with poor drainage/walled off (ab cannot penetrate)
3) Foreign bodies mistaken for infection (grass own in ear causes irritation that can look like otitis.
4) Neoplasias can be mistake for infections (Ex. Enlarged lymph node. Infection or lymphoma?)
5) MO resistance to the drug
6) Wrong ID of the bacteria
7) Mixed Infx (anaerobic/aerobic or Gram (+)/Gram (-))
What are the 6 drug reasons that ab don’t work?
1) wrong spectrum for existing infx (wrong drug)
2) Incorrect dosage (math)
3) Incorrect route
4) Tx too short
5) Poor bio-availability (% of drug absorbed affected by food in stomach, pH, etc–don’t get good peak blood levels)
6) Drug incompatibilities (can cancel each other out)
What are the 2 Host reasons that ab don’t work?
1) Elimination of competing NF (secondary infx)
2) Immunosuppression (can be important if using static ab)
How do you know if an ab works?
If a MO is susceptible/sensitive to it
How do you know if an ab doesn’t work?
If a MO is resistant to it.
What are the 2 reasons for ab resistance?
1) Natural Resistance
2) Acquired Resistance
Describe Natural Drug Resistance
Depends on the MO and the spectrum of the ab:
- Examples: Gram (+) MO are naturally resistant to Gram (-) narrow spectrum ab.
- **Mycoplasma is naturally resistant to penicillin
Describe Acquired Drug Resistance
- -Repeated exposure of MO to ab over time can cause a genetic mutation allowing the MO to survive
- -Drug resistance is passed on genetically to future generations
Give the 11 examples of drugs that are becoming increasingly resistant to ab.
Staph, Strep, E. coli, Salmonella, Proteus, Klebsiella, Mycobacterium, Pasteurella, Pseudomonas, MRSA, VRE
Describe the issues/talking points involving ab in livestock feed.
- -Leads to ab resistant MO in food animals
- -Can cause ab resistant bacterial infx in people and pets in rural areas
- -It’s illegal: have to have a withdrawal period
What are the 4 things that MO are doing to become resistant to ab?
1) MO can make an enzyme that inactivates or destroys an ab.
2) MO can change cell permeability so the drug can’t get in.
3) MO can modify site of ab attachment
4) MO can develop alternate metabolic pathways
What are the 5 things that we can do to help minimize acquired drug resistance?
1) use narrow spectrum ab
2) use -cidal drugs
3) use ab only for bacterial infx
4) Use correct dose (amount & duration)
5) Do C & S testing
What are the 2 types of ab susceptibility testing?
- -Kirby Bauer (qualitative–yes, no, maybe–which ones will work?)
- -Minimum Inhibitory Concentration (MIC–quantitative–gives minimum dose of ab that will work on MO)
What is the media used for the Kirby Bauer?
Meuller-Hinton
Describe the general procedure for the Kirby Bauer ab susceptibility test.
- *must have a pure culture
- apply a set concentration of MO to a plate then add paper discs with a set of concentration of ab)
Describe the BBL Promt Inoculation System for Kirby Bauer.
1) Touch 5 isolated colonies and suspend in tube of saline.
2) Use sterile cotton tip applicator to inoculate plate by swabbing the entire plate 3 times while doing a 1/3 turn.*Do not redip swab! Goal is a solid mass of MO with no blanks.
3) Apply ab disks making sure they adhere
Discuss the Kirby Bauer incubation/labeling.
Incubate for 24 hours and label the lid side (only exception to the rule).
How do you read the results of the Kirby Bauer test?
Measure the diameter of the zone of inhibition in mm and use chart to determine if the MO is resistant, intermediate or susceptible to the ab.
How do you interpret the results of the Kirby Bauer test?
Susceptible–ab should work
Resistant– ab probably won’t work
Intermediate-gray zone: may or may not work, may have to use higher than recommended dose
What does MIC stand for?
Minimum Inhibitory Concentration
Discuss the 3 points about MIC.
1) MIC testing determines minimum concentration of ab that will work on a MO
2) a dosage can be calculated from MIC
3) MIC testing may be a good idea if wanting to use a toxic ab (will determine the lowest dose needed to treat the infx)
Describe the MIC procedure.
1) Use tubes containing Mueller-Hinton broth
2) add different amounts of ab (serial dilutions)
3) Put set concentration of MO in each tube
4) incubate
How do you read the results of the MIC test?
1) Clear tubes indicate no growth and cloudy tubes indicate MO growth
2) MIC = lowest concentration w/o MO growth–the first clear tube
* *Once the MIC is determined, a drug dosage can be calculated for the patient
What are the 5 Brucella species?
canis, abortus, suis, ovis, melitensis
What are the characteristics of the genus Brucella?
Small GNROD. Aerobic to microaerophilic. Grows slowly in lab (5-7 days). Very tough bacteria: viable up to 4 months in urine, milk, damp soil, placenta, or aborted fetus (concentrated source of the MO). Can live intracellular. Survives & multiplies inside a phagocyte. Good @ tissue invasion and has an affinity for reproductive tract tissue.
Brucella canis:
What are the BC, reservoir, species affected, dz name, and how acquired?
BC: same for whole genus Res: dogs SA: dogs DN: Brucellosis Acq: Contact w/ vaginal secretions, urine, nursing & breeding
What is the pathology of Brucella canis?
Abortions in the last trimester. Prostatitis, epididymitis, and testicular atrophy in males.
How do you diagnose, treat and prevent Brucella canis?
Dx: Serology
Tx: No reliable tx. Encourage euthanasia. If do tx, be on long term ab and be spayed or neutered.
Pr. Screening by breeders. No immunization.
**Very low risk to humans–became a reportable dz in CO in ‘96.
Define Serology
A blood test for an antigen or the antibodies to that antigen.
Brucella abortus.
What are the BC, reservoir, species affected and dz name.
BC: same for whole genus
Res: occurs in nature (wildlife)
SA: cattle & related animals (buffalo, elk, moose, antelope), humans.
DN: "Bangs Dz" in cattle
"Undulant Fever" in humans
"Brucellosis" in all animalsHow is Brucella abortus acquired?
1: ingestion (most important)–eating aborted fetus/placenta, urine on grass.
2. Uterine/vaginal secretions
3. Urine/semen of infected males
4. Aborted fetus, placenta
5. Via breeding/AI
What is the pathology of Brucella abortus?
MO goes to the reproductive tract:
- Abortion storms (usually last trimester/spontaneous)
- Mastitis (transmitted in milk)
- Testicular abnormalities/prostatitis
- Infertility/conception failures
How do you diagnose and treat Brucella abortus?
Dx: can be cultured, but grows slowly (aerobic to microaerophilic). So, serology (blood test) is the INITIAL DX IN MOST CASES.
*do Brucellosis test when hit breeding age, or selling, transporting, or slaughtering.
*Get more $ for negative animals
TX: None–slaughter
How do you prevent Brucella abortus?
- *Most states have a strict eradication program.
- -goal is to be Brucellosis free (CO, WY, MT)
- -State regs are confusing–changes depending on if dairy or beef cattle
- -More regs with diary b/c shed in milk
- -More regs when moving across state line–esp into state that’s free of it.
- -Grazing on private vs. federal land
- -Slaughter vs shipping–more strict for shipping
What are the 2 primary ways to eradicate Brucellosis?
1: Immunize
2: Testing
Discuss the use of immunization in attempting to eradicate Brucellosis.
- RB51 immunization given to females under 12 months old (5 mo is best in CO).–the imm causes infertility in males–dont do!
- Females receive an ear tattoo or right ear tagged with orange tag.
**RB51 can only be sold to USDA approved DVM. But even he/she can’t do after 12 months b/c it’s a live bacterin and will always get persistent titers (test +)
Discuss the use of testing in attempting to eradicate Brucellosis.
Serology: the frequency varies.
- Do annual testing in dairy cows in CO–test for titers
- Do prior to shipping
- Might depend on use
- Silver metal ear tag
