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ESA3 > Infection Introduction to Microbials > Flashcards

Infection Introduction to Microbials Flashcards

1
Q

What is an infection?

A

When a group of microorganisms invade host tissue and cause disease by multiplication, toxins and the host response

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2
Q

3 ways people get infections

A

Transfer from another- vector, airborne, physical agent Contaminated environment- food or water, surface, inhalation Microbiota- commensals

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3
Q

Define a Pathogen and Pathogenicity

A

A microorganism which is capable of causing a disease

The ability to cause disease

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4
Q

Define commensals

A

An organism which is part of the normal bacterial flora

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5
Q

Define Virulence

A

The ability to cause SEVERE disease

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6
Q

How do microorganisms cause disease?

A

1) Exposure
2) Adherence
3) Invasion
4) Multiplication
5) Dissemination

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7
Q

Give some Virulence Factors

A

Exotoxins- AB Toxins, Superantigens, Enzymes (Proteins) -Toxic substances released by the organism into the cell

Endotoxins- Part of the Cell, made of lipid

Both damage the host

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8
Q

Disease Determinants

A

Pathogens- Virulence factors, innoculation size, antimictobial resistance

Patient- Site and Co-morbidities

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9
Q

Investigating an Infection: What do we do and Why?

A

1) History- severity, duration, potential exposures
2) Full Blood Count- neutrophils and lymphocytes
3) C Reactive Protein - acute phase protein is a measure of inflammation
4) Blood Chemistry- LFT KFT
5) Imaging
6) Histopathology
7) Examination
8) Bacteriology- grow specimen, microscopy, culture, succeptability, antigen/nucleic acid detection
9) Virology- antigen, antibody, viral nucleic acid detection

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10
Q

How can we classify Bacteria?

A

Gram stain

Shape- cocci, bacilli, spirals

Do they have an endospore? shape and position

An/aerobes, Enzymes, Serology, DNA Sequencing

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11
Q

Which bacteria are always Gram Positive?

A

Streptococci,

Staphylococci,

Listeria,

Clostridium,

Bacillus

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12
Q

Describe Gram Staining

A

Cells are stained with crystal violet dye. Iodine is added to create a complex with the violet (larger than original stain) Ethanol is added to dehydrate the peptidoglycan layer (shrinks and tighten) As positive bacteria have a thick peptidogylcan layer it is trapped. Negative Bacteria have a thinner P layer and the outside is mainly lipopolysaccharide so can be counter-stained red

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13
Q

What are the main features of a Virus?

A

Nucleic Acid- allow replication, can be DNA or RNA

Protein Coat

Envelope

Virus proteins- allow to bind and enter cells

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14
Q

What is a Bacteriophage?

A

A virus that invades and replicates inside bacteria

They transfer DNA to Bacteria, can transfer antibiotic resistance from B to B

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15
Q

Mechanism of Bacterial Pathogenesis

A

Host Entry - Capsule

Invasive - Specific enzymes to get into cells (e.g. Collagenase)

Adherence - Pili and Fimbrae

Iron Sequestration

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16
Q

Types of Fungi?

A

Yeast- single celled Moulds- multicellular

17
Q

Types of Parasite?

A

Protozoa- single-celled Helminths- multicellular, worms and flukes

18
Q

Describe the Infection Model

A

1) Patient and Pathogen meet 2) Mechanism of Infection 3) Infection 4) Management 5) Outcome

19
Q

Define the Mechanisms of Infection

A

Contiguous Spread- direct e.g from skin into a wound Inoculation- trauma carries bacteria into site Haematogenous- via blood stream Ingestion- usually Faecal to Oral transmission Inhalation- Droplets or Aerosols Vector Vertical- Mother to Baby

20
Q

What do Antibacterials aim at?

A

1) DNA Synthesis Quinolones, Antifolates 2) Protein Synthesis Aminoglycosides, Tetracycline, Macrolides 3) Cell Wall Synthesis - Most Common Beta Lactams, Glycopeptides

21
Q

Give 3 ways that Antibiotic Resistance can occur

A

1) Drug Inactivation 2) Alteration of the Target 3) Altered Uptake

22
Q

How does resistance occur?

A

Chromosomal Gene Mutation Horizontal Gene Transfer- Conjugation, Transduction or Transformation

23
Q

Name one Qualatative and one Quantitative way of measuring the activity of antibacterials

A

Disc Sensitivity Testing Minimum Inhibitory Concentration

24
Q

Name some gram negative bacteria

A

Neisseria

E Coli

Salmonella typhi

Haemophilus influenza

Proteus

25
Q

Give some examples of Cocci?

Are they Gram + or - ?

A

Streptococcus pneumoniae (+)

Coagulase negative Staph (+)

Staph aureus (+)

Neisseria (-)

Enterococcus faecilis (+)

26
Q

Give some examples of bacilli?

Are they Gram + or - ?

A

E Coli (-)

Salmonella typhi (-)

Listeria (+)

Bacillus … (+)

27
Q

Give some examples of encapsulated bacteria

Are they Gram + or - ?

A

Neisseria (-)

Salmonella typhi (-)

Strep pneumoniae (+)
Haemophilus influenzae (-)
28
Q

Describe Staphylococcus aureus

Shape

Gram Stain

Virulence Factors

Diseases it causes

Relevence?

A

Cocci, Aerobe

Gram Positive Bacteria

Capsule to evade phagocytosis, Exotoxins

Causes Hospital Acquired Pneumonia and Cellulitis

Normal Skin Commensal

Resistant Strains (enzyme cleaves B lactam ring)

29
Q

Describe Clostrium Difficile

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Spore Forming Anaerobe

Gram Positive

Part of Intestinal Flora, F to O transmission

It becomes pathogenic following drug (amoxicillin) treatment as flora is disrupted

Secretes Toxins A and B (cytotoxic and enterotoxic)

Causes Colitis

Hospital Acquired Infections

30
Q

Describe Streptococcus pneumoniae

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Cocci, Encapsulated Bacteria

Gram Positive

Increased risk in Asplenic patients

Causes Community Acquired Pneumonia, Meningitis and Bone infections

31
Q

Describe Neisseria meningitidis

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Gram Negative, Diplococci, Encapsulated

Causes Meningitis

Secrete Endotoxins, Pili, Polysaccharide, Capsule

Can be present in nasopharynx flora (10% adult carriers)

Spread: Aerosols

32
Q

Describe E coli

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Gram Negative, Bacilli

Part of Intestinal Flora (Coliform)

Causes UTIs, Diarrhoea

33
Q

Describe Helicobacter pylori

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Helical

Gram Negative

Secreates Urease, Has Flagellum, Releases Cytotoxins

Can be part of Stomach Flora

Speads O to O or F to O

Causes Gastritis and Ulceration

34
Q

Describe Influenza A

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Single Stranded

RNA Virus

No Gram Stain

Direct, Surface Contamination or Aerosol

35
Q

Describe Legionella pneumoniae

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Gram Positive, Coccobacillus

Has Flagellum, Aerobic

Spread: Infected water aerosols

Causes Legionnaires

Immunocompromised more at risk

36
Q

Describe Salmonella typhi

Shape

Gram Stain

Virulence Factors

Diseases it causes

A

Gram Negative, Aerobe

Encapsulated, Has invasin and fimbrae

Bacilli

Travel Related Infections

From F to O (food and water contaminated)

Causes Headache, Constipation.. Typhoid Fever

ESA3 (17 decks)

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