Key Terminology & Definitions - Bacteriology Flashcards
(102 cards)
1
Q
Bacteria
A
Single-cell organisms = prokaryotes which have no chlorophyll, multiply by simple division and some of which cause diseases in animals, plants and humans
2
Q
Respiratory host bacteria
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Mycobacterium, haemophilus
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Intestinal host bacteria
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Salmonella, E. coli, Yersinia
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Skin host bacteria
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Staphylococcus aureus
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Systemic host bacteria
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Streptococcus suis, salmonella
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Q
Gram-positive bacteria
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Thicker cell wall, lacks cell envelope (one cell mem), contains teichoic acid, purple/blue staining
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Q
Gram-negative bacteria
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Thin cell wall, have cell envelope (two cell mems), don’t have teichoic acid, pink staining
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Q
Mycobacteria
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Gram-positive, but don’t stain well, ZN stain better, acid-fast
9
Q
Spirochaetes
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Gram-negative, don’t stain well, silver stains, spiral/corkscrew
10
Q
Mycoplasma
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Very small bacteria, lacks cell wall, have very few genes, many ABs ineffective against them, cause disease in humans and animals (arthritis, abortion, pneumonia, infertility, meningitis and mastitis)
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Q
Binary fission
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Bacterial replication
12
Q
Infectious disease
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Disease caused by a microorganism, potentially transferable to new individuals, may or may not be communicable/contagious
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Q
Contagious disease
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Disease capable of spreading rapidly from one individual to another by contact or close proximity e.g. Parvo, MRSA
14
Q
Communicable disease
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Infectious disease that is contagious and can be transmitted from one source to another (term more in human medicine)
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Non-contagious infectious disease
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Infectious disease not transmitted by direct contact or exposure to contaminated environment (needs a vector) e.g. Bluetongue, Malaria, Lyme disease
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Primary pathogens
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Can cause disease in a healthy host (true pathogens), satisfy Koch’s postulates e.g. Bovine TB, Salmonella, Anthrax
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Opportunistic pathogens
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Cause disease in the presence of or following a predisposing factor e.g. Avian colibacillosis - depends on certain circumstances
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Horizontal transmission
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Same generation
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Direct contact
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E.g. Sarcoptes scabiei canis, Microsporum canis, MRSA
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Sexual transmission
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E.g. Trichomonas foetus, Brucella, CEM (contagious equine metritis), papillomavirus
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Vertical transmission
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Different generation e.g. mother to offspring - FIP, Brucella, Salmonella (eggs), BVD)
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Q
Indirect transmission
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Contaminated food/water (E. coli, Salmonella, Listeria); actively/passively by vectors (Malaria, West nile, Bluetongue); Airbone (Avian flu, FMDV); contaminated equipments (Fungi, Sarcoptes scbiei, FMDV, mastitis); infected lorries/housing; environment (wildlife).
23
Q
One health concept
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Recognises the interrelationship between animal, human and environmental health
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Q
Bacilli
A
Rods
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Cocci
Spherical
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Spirocheates (morphology)
Long, thin, windings
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Vibrios
Comma (bean-shaped)
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Gram-staining
Distinguishes between gram +ive and gram -ive, based on retaining crystal violet staining + counterstaining, heat fixation, not usable with all bacteria
Gram +ive will retain purple colour (peptidoglycan binds CV), gram -ive will be destained by alcohol (no trapping of CV to peptidoglycan)
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Diff Quick staining (modified Giemsa/Romanowsky)
Rapid staining for morphology, wet fixation
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Ziehl-Neelsen (ZN) staining
Specific staining for mycobacteria
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Silver staining
Specific staining for spirocheates
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Peptidoglycan
Gives rigidity to bacterial cells, assists in preventing phagocytosis, has pyrogenic properties (causes fever), can be degraded by lysozyme enzyme
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Fastidious organisms
Require particular nutrient requirement
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Non-fastidious organisms growth media
Nutrient media - nutrient agar, Mueller Hinton (broth media)
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Fastidious organisms growth media
Enriched media - blood/serum agar (whole blood, lysed blood, serum), other supplements (electron acceptors, energy sources)
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Selective media
Supplemented plates e.g. antibiotics (Campylobacter)
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Differential use of nutrients
Fermentation of sugars - MacConkey agar - stops gram +ive from growing/fungi
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Oxidase test
Test for gram -ive bacteria, based on cytochrome C oxidase
Positive e.g. Pseudomonas, Neisseria, Moraxella, Campylobacter (gram -ive)
Negative e.g. Enterobacteriaceae (gram +ive)
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Catalase test
Measures conversion of H2O2 to H2O and O2 = bubbles
Positive e.g. Staphyloccus, Listeria, Enterobacteriaceae
Negative e.g. Streptococcus, enterococcus
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Coagulase test
```
Converts fibrinogen (soluble) to fibrin (insoluble), used to distinguish Staphylococcus species
Positive: S. aureus, S. intermedius
Negative: S. epidermidis, S. hominis
```
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MacConkey agar
Selects for lactose-fermenters, senses pH-change with neutral red ---> purple, inhibits gram +ive growth with bile and CV
Lactose fermenting colonies = pink, non-lactose fermenting colonies = colourless
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Lactose fermenting colonies
Escherichia coli, enterobacter aerogenes (Enterobacteriaceae)
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Non-lactose fermenting colonies
Proteus vulgaris, Salmonella typhimurium, Staphylococcus aureus
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Haemolysis
Breakdown of RBCs, ability of bacterial colonies to induce haemolysis when grown on blood again differs between microorganisms
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Beta-haemolysis
Complete haemolysis, see-through, see a lot of light e.g. Streptococcus pyogenes
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Alpha-haemolysis
Incomplete haemolysis e.g. Escherichia coli
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Gamma-haemolysis
Lack of haemolysis (none) e.g. Staphyloccus epidermidis
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Serology
Based on antisera to surface structures - flagella (H antigen), lipopolysaccharide (LPS/LOS), capsule (K antigens in E. coli)
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Phage-typing
Based on susceptibility to panel of bacteriophages
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Antimicrobial susceptibility
Based on susceptibility/resistance to specific antimicrobials
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Pathogenicity
Ability to cause disease (damage the host)
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Virulence
Degree of pathology caused by the organism/infection
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Infectivity
The capacity for transmission/spreading to new hosts
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Transmissibility
Capacity to grow in parts of the body, readily exit an infected host (boy orifices - blood to blood, nasal-nasal sneezing, vectors), survive in transition between hosts (sporulation, environment, arthropod-borne infections)
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Exogenous
Mainly true pathogens (don't carry with you)
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Endogenous
Opportunistic pathogens and persisten true pathogens e.g. trauma in nasopharynx, opportunistic pathogens could become true pathogens
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Mucin
Mucus - mesh of proteins and polysaccharides which protects many parts of the body
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Non-proteinaceous toxins
Endotoxins - released into bloodstream + cause septic shock, lipopolysaccharide/lipooligosaccharide
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Proteinaceous toxins
Exotoxins - proteolysis, neurological, contraction of things
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Pus
DNA, proteins, dead immune cells (neutrophils), host cells (abscess)
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Spreading factors
Proteins like DNases and proteases that act as 'meat tenderisers', facilitate spread into neighbouring tissue
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Adhesions
Mechanism of adhering to host surfaces through specialist attachment proteins (pili/fimbrae)
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Exotoxins
Mainly produced by gram +ive bacteria (gram -ive e.g. E. coli can also produce them), proteins in nature (few are enzymes), rapidly spread from bacteria by filtration, usually thermolabile, can cause cytopathic effects
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Endotoxins
Released after natural autolysis/artifical disruption (freezing, thawing, sonic vibrations), thermostable, integral part of outer layer of bacterial cell walls, gram -ive bacteria, complex phospholipid, toxic shock syndrome
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Aggressins
Contribute to the ability of capsulate or non-capsulate bacteria to invade and multiply in the host's tissues and enhance the permeability of tissues, facilitating the spread of bacteria
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Commensals
One member of one species gain benefits while those of the other species neither benefit nor are harmed
E.g. Commensals of the mucosal surfaces may cause disease if the body defences are compromised due to viral infections (2^y infection) or following trauma, surgical interventions, immunosuppression or other environmental stress
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Microbiota
Microorganisms
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Microbiome
Genes that makeup microbiota
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Common bacterial skin flora
Mainly gram +ive - Staphylococci, Streptococci, Corneybacterium, occasionally also gram -ive - some pathogenic (dermatitis)
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Microflora of upper respiratory tract
Pasteurella multocida, Mannheimia haemolytica, Haemophilus somnus, Mycoplasma bovis, histophilus somni and Mycoplasma bovirhinis
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Microflora of oral cavity
Streptococci, Staphylococci + various anaerobic and aerobic bacteria - Treponemes
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Microflora of GIT
Enterobacteria (E. coli, Proteus spp., Klebsiella spp., Citrobacter, Yersinia)
Anaerobic bacteria (Clostridium spp., Bacteriodes spp., Fusobacterium spp.)
Lactic acid bacteria (Lactobacillus, Enterococci)
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Microflora of hoof
Fusobacterium necrophorum, Bacteriodesdes melaninogenicus, Dichelobacter nodosus.
Treponema spp., Peptococcus and Campylobacter (Cattle and sheep digital dermatitis)
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Microflora of ears
Ear wax (cerumen prevents flora entering inner ear canal) - Staphylococci, Streptococci, Pseudomonas spp. (not normally part of predominant normal flora of ear, normally associated with infection), bacteria, yeasts, fungi, viruses and protozoa
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Bacterial flora of upper ear
Mainly gram +ive (Staphylococci, Streptococci)
| Sometimes gram -ive (E .coli, Branhamella (Moraxella), Pseudomonas spp. - on skin of ear)
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Microflora of eye
On the conjunctiva - Streptococcus and Staphylococcus
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Dysbiosis (dysbacteriosis)
Microbial imbalance or maladaptation on or inside the body
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Probiotics
Live microorganisms which when administered in adequate amounts (high) confer a health benefit to the host e.g. Lactobacillus (produce lactic acid bacteria), Bifidobacteria (produce butyric acid bacteria), Enterococci.
Act by allowing out-competition of pathogens, producing anti-microbial compounds, altering immune response
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Horizontal gene transfer (HGT)
Movement and rearranging DNA in prokaryotes e.g. bacteria, also referred to as lateral gene transfer (LGT)
Requires at least physical movement of DNA and incorporation into the receiving genome so it is stably inherited
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Mobile genetic elements (MGE)
Type of DNA that can move around within and the genome (one organism to another) e.g. transposons (transposable elements - retrotransposons, DNA transposons, insertion sequences); plasmids, bacteriophage, group II introns, group I introns
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Mobilome
Total of all mobile genetic elements in a genome
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Plasmid
Circular piece of self-replicating DNA located outside of the bacterial chromosome. They can carry multiple resistance mechanisms e.g. ESBL (extended-spectrum beta-lactamase), and transfer them via a pilus
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Pilus
Appendage that allows bacteria to adhere to each other and transfer genetic material
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Phage
Virus infecting bacteria
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Conjugation
Two living bacteria come in direct contact - one bacterium transfers its DNA (plasmid) to the other
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Transformation
When a bacterium dies, its DNA is released into the environment where it can be taken up by another living bacteria (free DNA)
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Transduction
A phage takes some DNA from one bacterium and transfers it to another
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Competence
Physiological state, often highly dependent on the environment, which enables bacteria to uptake macromolecules that bind to its surface
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Antimicrobials
Chemicals that either kill or prevent the growth of microbes - bacteria, viruses, fungi or protozoa
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Prophylaxis
'Healthy' individuals to prevent infections where is a perceived risk
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Metaphylaxis
There is a definable hazard
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Extended-Spectrum Beta-Lactamases (ESBLs)
Enzymes that can be produced by bacteria making them resistant to cephalosporins e.g. cefuroxime, cefotaxime and ceftazidime, resistance can be carried on a plasmid
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Innate, natural or intrinsic resistance
Vancomycin - gram -ive bacteria and Lactobacilli
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Mutational resistance
Fluoroquinolone resistance (point mutation) - E. coli, Salmonella
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Extrachromosomal, chromosomal or acquired resistance
ESBL resistance - E. coli, Salmonella, Klebsiella - MRSA, MecA gene (moved from one staphylococcus to another)
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Phenotypic/persister state
Mycobacterium bovis - no genetic basis, organisms can go into dormant state + metabolism slowed right down for survival
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Physical mechanisms of resistance
Biofilms - Salmonella, Campylobacter, E. coli, Pseudomonas (wound infection)
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Efflux pump
Antibiotic resistance - extrude AB out of the cell as fast as it can enter
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Primary active transporters
Utilise energy stored in ATP to catalyse transport of drug across the membrane by ATP hydrolysis
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Secondary active transporters
Driven by the energy stored in ion gradients that are in turn generated by respiration, to catalyse the transport of drugs across the membrane
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Phosphotransferase system (PTS)
Catalyses the transport of drug with a concomitant phosphorylation of the drug, usually for cellular entry of the drug substrate
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Mutant prevention concentration (MPC)
The lowest concentration of AB to inhibit the emergence of mutants, if an AB conc is maintained above the MPC, resistant bacteria should not be selected for
