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68 Cards in this Set

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  • Back

What are the features of a gram +ve cell wall?

- Proteins

- Teichoic Acid

- Lipoteichoic Acid

- Peptidoglycan

How can gram stain differentiate between +ve and -ve?

+ve shows as purple-blue

-ve shows as red

What are the features of a gram -ve cell wall?

- O Polysaccharide / Lipopolysaccharide (Endotoxin)

- Porins

- Proteins

- Lipid A (innermost part of LPS)

Survive on drying?

+ve Yes

-ve No

Produce spores?

+ve Yes

-ve No

What do all gram -ve have in their cell wall?

Lipopolysaccharide (endotoxin)

Name three gram +ve rods?

- Clostridium

- Bacillus

- Diptheria / Listeria

Name some gram -ve rods?

- Enterobacteriacaea

- Pseudomonas

- Legionella

- Haemophilus Influenzae

- Bacteroides

Pathogenic mechanisms of E.Coli?

- LPS binds to LPS binding protein which binds to cell surface molecules eg. TLR4

- Stimulates pro-inflammatory cytokines (TNFα / IL-1 / IL-6)

- Small capsule is antiphagocytic

- Iron binding proteins scavenge iron

Two types of E.Coli?

- ETEC - Enterotoxigenic (Traveller's Diarrhoea)

- EHEC - Enterohaemorrhagic (colitis / Blood diarrhoea)

What infections can E.Coli cause?

- 80% of community acquired UTI

- Pyelonephritis (from urinary tract -> kidney)

- Intraabdominal infections

- Septic shock / bloodstream

- Pneumonia

Drugs for E.Coli treatment?

- Amoxicillin if sensitivity confirmed (<50%)

- UTI / Communty acquired severe sepsis - Trimethoprim / Nitrofurantoin

- Hospital acquired severe sepsis - Tazobactam / Pipericillin

- Aminoglycosides (sometimes for severe sepsis)

What type of bacteria is salmonella?

- Non-lactose fermenting gram -ve rod

- Enteric fever types (typhoid)

Pathogenic factors of Pseudomonas Aeruginosa?

- Heat tolerant

- Endotoxin

- Exotoxin A / Elastase / Leucocidin

- Iron binding proteins

- (Produces pyocyanin - green pigment)

Who is extremely susceptible to Pseudomonas infection?

- Those with mucus accumulation ie CF

What infections can Pseudomonas Aeruginosa cause?

- Neutropenia

- UTI (instrumentation)

- Pneumonia

- Skin & soft tissue

- Eye keratinitis

- Endopthalmitis

Where does Pseudomonas Aeruginosa typically transmit from?

- Unclean water

- Contaminated equipment

- Poor quality drinking water

Which drugs should be used to treat Pseudomonas?

- Fluoroquinolone (Aproflaxin) only oral agent

- Pipericillin / Tazobactam for hospital acquired severe sepsis

- Gentamicin if severe

What are the pathogenic factors of Haemophilus influenzae?

- Large polysaccharide capsule (types a-f) but b is most invasive therefore vaccine as a child

- IgAse inactivated IgA on mucosal surfaces

- Adhesins in cell wall promote colonisation

Where does HI mostly colonise?

- Mucosal surfaces

- Mostly the Upper RT

What infections does Haemophilus cause?

- Invasive - Meningitis / Pneumonia / Cellulitis / Epiglottitis (pain swallowing food)

Non-invasive - Blood cultures -ve / Otitis media / Conjunctivitis

Which drugs are used to treat Haemophilus?

- Amoxicillin - 15% resistant

- Co-Amoxiclav if resistant

- Rifampicin given as chemoprophylaxis when other children <5y/o in the family

How do you get E.Coli

Eating / drinking food / contact with human / animal faeces contamination

How does haemophilus spread?

- Usually harmless in the nose and throat

- Can spread to blood --> infection

What are bacteroides and what drug are some sensitive to?

- Most common bacteria in body (faeces)

- Anaerobes are sensitive to Metranidazole

How do Neisseria species replicate?

- Unable to survive outside of the body

- Survive and replicate inside neutrophils

Where can Legionella Pneumophila be found?

- Gram -ve rod in freshwater aquatic environments

- Infection by aerosol contaminated water

What can Legionella cause and how can it be detected?

- Severe community acquired Pneumonia

- Legionella urinary antigen is +ve for 7-10 days post symptoms

How does Helicobacter Pylori affect the host? What conditions does it cause?

- Colonises stomach & lives under mucus

- Produces urease to increase local pH

- CagA associated with virulence

- Gastritis / Duodenal Ulceration / Gastric Lymphoma

How is Helicobacter detected? How is it treated?

- Antigen detection in the stool

- PPI + Dual / triple antibiotics required for erad.

What are the Staph Aureus virulence factors (not inc. exotoxins)?


Protein A which binds the Fc portion of IgG and is therefore anti-phagocytic


Coagulase which deposits fibrin around bacteria in tissues

Which exotoxins do Staph Aureus produce?

- Haemolysins

- Enterotoxins (short lived, profuse vomiting)

- Exfoliatin

- PVL (vs neutrophils)

- TSST (IL-1 / 2 / TNF)

What drugs are used to treat Staph Aureus?

- 90% of strains are resistant

- Flucloxacillin & Co-Amoxiclav effective

- Macrolides (Erythromycin & Clarithromycin) in penicillin allergy

What is special about MRSA resistance?

- Has mecA gene - altered penicillin binding sequence

- Low affinity for all B-Lactams

- Frequently has macrolide resistance

What is Strep Pyogenes' main virulence factor?

M Protein in its cell wall is anti-phagocytic

What can Strep Pyogenes cause?

- Suppurative infections

- ENT - Pharyngitis / Tonsilitis / Sinusitis

- Puerpal Fever (& scarlet fever)

- Skin - Impetigo / Cellulitis / Necrotising fasciitis

- Streptococcal toxic shock (SpE superantigen)

- Acute Rheumatic fever

- Acute Glomerulonephritis

What is the difference between Staph Aureus & Strep Pyogenes toxic shock?

Unlike Staph Aureus toxic shock, blood cultures are usually positive

What are the mnemonics to remember SA Vs SPy manifestation?

SA produces HEEPT

SPy causes SEPSS AA

What are the mnemonics to remember SA Vs SPy manifestation?

SA produces HEEPT

SPy causes SEPSS AA

How does SPy cause Acute Rheumatic Fever?

- 2-3 weeks post acute streptococcal pharyngitis / scarlet fever in 5-15 year olds

- Fever / rash / polyarthritis / pancarditis

Which parts of the body are most affected in Acute Rheumatoid Fever?

- Heart Valves

- Basal Ganglia

- Joints

How does SP cause Acute Glomerulonephritis?

- 3 weeks after SP in 2-6 y/o

- Fluid overload - Oedema / Hypertension / Oliguria

Which drugs are used to treat SPy?

- Group A strep are 100% sensitive to penicillin

- Erythro / Clarithro / Vanco

Distinctive features of Strep Pneumoniae?

- Pneumolysin (alpha haemolysis on blood agar)

- Cell wall contains C-Polysaccharide & Pneumococcal teichoic acid

What is the effect of C-Polysaccharid?

- Induces C-reactive protein production in the host

- Non-specific marker of INFLAMMATION

What can SPn cause?

- Upper respiratory (sinusitis)

- Lower respiratory (pneumonia)

- CNS (meningitis)

Who's most at risk of SPn infection?

- Hyposplenic / Splenectomised
Bacterial Peritonitis

What is the current preventation / treatment for SPn?

- 2 Vaccines

- 7 valent conjugate as part of childhood imm.

- 23 valent polysaccharid for adults at risk of invasive

What famous disease can Bacillus cause?

Bacillus --> Enterotoxins & Anthracis --> Anthrax

Name a coagulase +ve and a -ve?

+ve - Staph Aureus

-ve - Staph Epidermis

Distinctive properties of the Clostridium species?

- Ubiquitous

- Produce exotoxins with diverse effects

What is the mechanism by which C Dif works?

- Spores ingested germinate and infect colon

- Enterotoxins produced --> inflammatory diarrhoea / collitis

How does C Tet work?

- Gains entry through wound

- Tetanospasmin prevents inhibitory neurotransmitter release

- Lockjaw

How does C Bot work?

- Ingested from contaminated food

- Imported to CNS and inhibits ACh release at NMJ --> Paralysis

What are the Mycobacterium Tuberculosis pathogenic factors?

- Replicates inside macrophages

- Mycolic acid stimulate host sensitivity

What is the hose response to MT?

- Antibodies formed but ineffective

- Mycobacterial antigens presented on surface

- Lymphokine contribute to tissue damage and attract activated macrophages

How is MR transmitted?

- Exposure to droplet nuclei

- Cumulative <8h required

- Extrapulmonary --> any system

- 85% involve lower RT


What antibiotics are used to treat TB?

2 Months

Rifampicin / Isoniazad / Pyrazinamide / Ethambutol

4 Months

Rifampicin / Isoniazad

What can Treponema Pallidium cause?

- Syphillis

- Lyme Disease

What are the problems with Treponema identification? How is it transmitted?

- Cannot be gram stained so viewed by dark ground microscopy

- Congenital / Sexual transmission

Phases of Syphillis?

1' - Genitals / mouth chancre

2' - 2-8w post primary systemic illness due to dissemination

Latent - 2/3 do not progress & may last years

3' - Late - CV / neurosyphilis / gummatous

How is Syphilis treated?


What are the hallmark symptoms of congenital syphilis?

Hutchinson's Triad

- Hutchinson's Teeth - Barrel Shaped / Notched incisors

- Deafness

- Interstitial Keratitis

What are the distinctive feature of Mycoplasma Pneumoniae?

- Contain sterols not peptidoglycan

- No gram stained but can be slow cultured

How can Mycoplasma Pneumoniae be detected?


Distinctive features of Chlamydia species?

- Intracellular and reuire host cell ATP to replicate

- Not visible on gram stain

What diseases can Chlamydia Trachomatis cause?

- STI --> Urethritis

- Eye infection --> Blindness

What diseases are cause by Chlamydia Psittaci / Pneumoniae?

Pneumonia (both)

PCR for diagnosis