Antibiotics, diagnostics and vaccines

What are bacteriocidal antibiotics

Antibiotics that kill bacteria

What are bacteriostatic antibiotics

Antibiotics that prevent bacteria growing

What are narrow spectrum antibiotics

Antibiotics that target a specific type of bacteria such as penicillin and aminoglycosides

What are broad spectrum antibiotics

Antibiotics that target many types of bacteria such as some synthetic penicillins, potentiated sulphonamides, tetracyclines and fluoroquinolones

What antibiotic is antibiotic resistance more common in during treatement

Fluoroquinolones and rifampicin

When are empiric antibiotics used

When the infecting organism is not yet identified so has a broad spectrum use

When are definitive antibiotics used

When the organism is identified and specific therapy is chosen so has narrow spectrum use

What is prophylaxis

The prevention of disease

What is metaphylaxis

The treatment of animals that are at risk of disease to control the spread

What is the minimal inhibitory concentration of a drug

The minimum concentration of the chemical that prevents the growth of bacteria

What is direct detection when determining resistance

A method that identifies the presence of antibiotic resistance genes directly from a sample without the need to culture and isolate the bacteria instead using PCR and whole genome sequencing

What antibiotic targets DNA synthesis in bacteria

Fluoroquinolones

What antibiotics targets folic acid synthesis in bacteria

Sulfonamides and trimethoprim

What antibiotic targets the outer membrane of bacteria

Polymixins

What antibiotics target protein synthesis of bacteria

Macrolides, tetracycline and aminoglycosides

What antibiotics target the inhibition of cell wall synthesis in bacteria

β-lactams

What is inherent/intrinsic resistance

Bacteria’s natural ability to resist a specific antibiotic due to its inherent structure or functional characteristics

What are examples of acquired resistance

Mutation within its own DNA or horizontal gene transfer

What is co-selection

When bacteria develops resistance to multiple antibiotics at the same time

What are the stages of the resistance mechanism

1. Pump the antibiotics out of the bacteria via efflux pumps sitting in the membrane or cell wall

2. Decrease permeability of the membrane that surrounds the bacteria cell

3. Destroy the antibiotic via enzymes that inactivate them

4. Modify the antibiotic to prohibit binding between the antibiotic and its target in the bacteria cell

What are examples of natural penicillins

Benyzl penicillin / penicillin G

What are examples of amino penicillins

Amoxicillin and ampicillin

What does the term magic bullets mean

A chemical that kills bacteria without harming the body

What is a first generation antibiotic

Antibiotics that have good activity against gram-positive bacteria but poor activity against gram-negative bacteria

What is a second generation antibiotic

Antibiotics with increased activity against gram-negative bacteria but decreased activity against gram positive bacteria

What are some examples of prophylactic and metaphylactic uses of antibiotics in animals

• After surgery

• Dry cow therapy

• Before transportation

• Potential outbreaks

• Stressful conditions

What classes are in the family β-lactams

• Penicillin

• Cephalosporins

• Carbapenems

What is the main method of β-lactam resistance

• Enzyme modification

• β-lactamases hydrolyses the liable β-lactam ring pond

• Can be used in combination with other β-lactams to act as a β-lactamase inhibitor

What are extended-spectrum β-lactamases

• Hydrolyze a wide range of β-lactam antibiotics including 3rd and 4th generation cephalosporins

• Inhibited by clavulanic acid

• AmpC β-lactamases of gram-negatives are not inhibited by clavulanic acid

What are aminoglycosides

• Gentamicin, streptomycin

• Often used in combination with the β-lactam antibiotics such as the penicillin

• Are toxic

What are the methods of aminoglycosides resistance

• Ribosome alteration

• Decreased permeability

• Inactivation of aminoglycosides 16SrRNA methylases

What are the different generations of fluoroquinolones

• 1st Gen Nalidixic acid

• 2nd Gen Ciprofloxacin, enrofloxacin

• 3rd Gen Marbofloxacin

What is the mechanism for fluoroquinolones

Inhibit DNA metabolism and are broad spectrum

What should be considered when choosing an antibiotic

• Is it a bacterial infection

• Does is require treatment

• What is the site of infection

• What bacteria are involved

How do you decide what bacteria is causing an infection

• Site and species

• Examination of smears

• Culture and identification

• Susceptibility and resistance profiles

What is the maximum residue limit

The highest allowable concentration of a antibiotic residue that can legally remain on or in food to be safe for consumption

What are diagnostic tests

• Laboratory tests such as blood and urine tears

• Imaging tests such as ultrasound or CT scan

• Endoscopy such as colonoscopy and bronchoscopy

What are aseptic techniques

Any method used to sterilise and maintain the sterility of an object or location such as an operating theatre or laboratory

What are the principles for sample collection

1. Specimens must be obtained aseptically from a site that is representative of the disease process

2. A sufficient quantity of material should be collected

3. Specimens must be collected prior antibiotics to maximise pathogen recovery

4. If cultures are not immediately initiated after collection specimens should be refrigerated

What should be included in a sample submission form

• Presentation and history of patient to help guide microbiologist towards diagnosis

• Required tests to investigate aetiology, specific pathogen and specific screen

• What is the sample type such as faeces, urine, blood, swabs

How should samples be transported

• Fast to stop bugs from dying

• Use transport medium such as amie’s, charcoal, cary-blair

How should samples be stored

• Only if necessary

• 4 degrees

• Long term storage at -80 degrees or below

What are the methods to identify an unknown pathogen in clinical specimens

• Microscopic examinations

• Culture based methods

• Molecular methods

• Antigen-antibody reactions

• Point of care tests

How do you take a direct microscopic observation of clinical material

• Make a smear using a swab

• Make a smear using aspirate

• Make a tissue impression smear

What are the pros of making a direct microscopic observation of clinical material

• Cost effective and rapid

• Provides immediate information on presence or absence of bacteria and number of organisms

• Allows presumptive identification of bacteria such as morphologic characteristics and gram staining properties of microorganisms

• Provides information on the host cellular response

How do you stain fungi for microscopic observation

• KOH 10% with blue Parker ink

• Acts as a clearing agent

• When the ink is added the fungal spores take up the ink and appear blue-violet

How are viruses observed microscopically

• Low sensitivity

• Not very specific

• Expensive equipment

What do bacteria cultures aim to achieve

• Isolation of the organism in pure culture by inoculating specimen onto appropriate artificial culture media

• Identification of the isolate by microscopic examination, biochemical reactions or state of the art techniques

• Anti microbial susceptibility testing after growing the organism in pure culture

How do you isolate bacteria

• Most pathogenic bacteria grow on agar plates

• Most common contaminants also grown on agar plates

• Specific enrichment and selection protocols can be used to hunt for particular pathogens

• Different incubation conditions

What are enrichment media

General propose media supplemented by blood or other special nutrients to encourage the growth of fastidious organisms

What is differential media

Distinguish between differential groups of bacteria on the basis of their biological characteristics

What is selective media

Favour of the growth of particular microorganisms and inhibit the growth of others

How do blood agar plates help

to identify bacteria

Some bacteria secrete enzymes and toxins that lyse the erythrocytes in the agar producing zones of haemolysis

How do you identify if bacteria is gram positive

1. Fixation

2. Crystal violet

3. Iodine treatment

4. Decolorisation

5. counter stain with Sarandon

6. Gram positive stain purple and gram negative stain pink

What is the oxidase test

Detects the presence of cytochrome C oxidase. This enzyme reduces tetramethyl-p-phenylene-diamine, a redox dye, to yield a purple product

What is the catalase test

• Detects the presence of catalase enzyme

• If the bacteria have the enzyme external hydrogen peroxide is broken down to oxygen and water

• Oxygen is seen as bubbles

What are the phenotypic traits used for identification of bacteria

• Oxygen requirements

• Culture characteristics

• Staining properties - gram, acid fast

• Microscopic morphology

• Biochemical reactions

• MALDI-TOF

Why is antimicrobial susceptibility testing used

Help guide the selection of the most appropriate antimicrobial agent

What is the method disc diffusion of antimicrobial susceptibility testing

• A growth medium is seeded throughout the plate with the isolate of interest

• Discs impregnated with antimicrobial agents dispensed

• After an overnight incubation the bacterial growth around each disc is observed

What does it mean if an microorganism is susceptible

The microorganism is inhibited by a concentration of antimicrobial agent that can be attained in blood with the normally recommended does and implies that an infection caused by this microorganism may be appropriately treated with the antimicrobial agent

What does it mean if a microorganism is resistant

The microorganism is resistant to concentrations of the antimicrobial agent that can be attained with normal doses and implies that an infection caused by thus microorganism could not be successfully treated with this antimicrobial agent

What is an intermediate

A buffer zone to avoid misinterpretation, treatment is possible if the infection is in body sites where the antimicrobial is concentrated

What are cyopathic effects

• Rounding of cells

• Fusion - syncytia

• Inclusion bodies

What is viral haemagglutination

• Virus that clumps red blood cells stopping them from settling at the bottom of a well

• The sensitivity of the assay can be compromised by poor management of red blood cells

What are clinical specimens for fungal culture

• Plucked hairs from the lesions

• Toothbrush

• Skin scrapings

• Exudates

• Biopsies and tissues

What is an indirect method of diagnosing ringworm

• Ultraviolet fluorescence

• Some fungi produce metabolites that fluorescence of a vivid apple-green colour when examined under UV light

What are antigen-antibody reaction diagnostic tests

• A known antigen to detect specific antibodies in animal serum

• A known antibody to detect bacteria/viral agents in clinical samples

What is serological testing

• Detect the presence of antibodies in a patients serum

• Antibodies are specifically produced against certain antigens useful to diagnose specific infections

• It can indicate an ongoing infection, past exposure, maternal derived antibodies and vaccinations

What is a skin tuberculin test or intradermal reaction

• For diagnosis of Mycobacterium bovis causing bovine TB

• Interdermal injection of bovine tuberculin

• Subsequent detection of swelling at the site of injection 72 hours later measured with calipers

What are advantages of PCR

• Very sensitive

• Detects microorganisms that are non viable, uncultivable or slow glowing

• Faster results compared to culture methods

What are the limitations of PCR

• Susceptibility of PCR reaction to inhibitors, contamination and experimental conditions

• Failure to differentiate live and dead organisms

What organisms are detected by PCR

• Uncultivable and slow growing

• Mycoplasmas

• Mycobacteria

• Spirochetes

• Viruses

What is point of care testing

• Clinical laboratory testing conducted close to the site of patient where care or treatment is provided

• Rapid test results with the potential to generate a result quickly so that appropriate treatment can be implemented leading to improved clinical or economic outcomes compared to laboratory testing

What is analytic sensitivity of a diagnostic test

The detection limit, the lowest amount a test can detect

What is clinical sensitivity of a diagnostic test

The tests ability to correctly designate an individual with disease as positive to the test

What is analytic specificity of a diagnostic test

The ability to not react with other substances other that the analyte of interest

What is clinical specificity of a diagnostic test

The tests ability to correctly designate an individual who does not have a disease as negative to the test

What is a vaccine as defined by the world health organisation

• Any preparation intended to produce immunity to a disease by stimulating the production of antibodies

• Include suspensions of killed or attenuated microorganisms or products or derivatives of microorgansims

• Most common method of application is injection but some are given by mouth or nasal spray

What are some cases of where vaccines have worked

• Eradication of smallpox

• Eradication of Rinderpest

• Reduction of Salmonella-positive chicken flocks 250 to 7 within for years of vaccinating laying hens in the UK

Who is credited with the first description of "modern" Western vaccination, and what was it based on

Edward Jenner in 1796 using cowpox-infected pustules to vaccinate against smallpox

Why is the term "vaccine" used, and who coined it

By Louis Pasteur to honor Edward Jenner coming from the Latin word vacca, meaning "cow"

What was the first laboratory-produced vaccine and who developed it

By Louis Pasteur in 1872 and it was for fowl cholera in chickens

What were some older vaccination strategies before modern vaccines

Sniffing of dried smallpox pustules in ancient Egypt and China, a practice known as smallpox variolation

What can a vaccine do

• Protect an individual against disease

• Prevent transmission of infection

• Prevent or reduce infection

What are the ideal features when making an effective vaccine

• Must be safe

• Must protect against illness

• Must give sustained protection

• Must induce neutralizing antibody

• Must induce protective T cells

• Must have low cost per dose, biological stability, ease of administration and few side-effects

What is a key factor regarding the cost of veterinary vaccines

• For equine and small companion animals, cost is less important

• For farm animals raised for food production, very low-cost vaccines are essential

What is an important consideration for the administration of veterinary vaccines

• Vaccines should have easy administration for production animals, such as spraying or adding to drinking water

• A single dose for livestock is ideal, while annual boosters for pets ensure animals are regularly seen by a vet

Why is stability important in veterinary vaccines

To ensure they remain effective under various storage and handling conditions

How can veterinary vaccines avoid interference with diagnostics

Vaccines should not interfere with diagnostic tests. For example, older West Nile Virus (WNV) and Foot-and-Mouth Disease Virus (FMDV) vaccines did not distinguish between vaccinated animals and potential carriers

What are the different types of vaccines

• Killed / inactivated

• Live attenuated

• Live recombinant / vector

• Sub-unit

• DNA / RNA

What are killed of inactivated vaccines

• Simplest vaccine form

• Produced from heat or chemically killed pathogen

• Widespread use in human and veterinary medicine

What are some examples of killed vaccines

• Rabies - B-propiolactone

• Polio - formaldehyde

• Influenza - B-propiolaactone

• Salmonella - heat

• Vibrio cholerae - heat

• Bordetella pertussis - heat or formaldehyde

What are live attenuated vaccines

Viruses, bacteria or protozoa that typically have been passaged away from host repeatedly until they have reduced virulence

How are live vaccines administered

• Oral and nasal

• Use of natural route

• Single dose

How are killed vaccines administered

• Parenteral

• Multiple doses

Are live vaccines stable

Need a cold-chain

Are killed vaccines stable

They are heat stable

How does the cost of live and killed vaccines compare

Live are cheaper then killed

How does the duration of immunity of live and killed vaccines compare

Live is longer lasting then killed short lived response

How are traditional vaccines designed

• Empirically, often through attenuation (weakening) via random mutation

• An example is the BCG vaccine