bacteria

Question 1

What are bacteria?

Answer 1

unicellular organisms , lacking organelles

Question 2

What is the main difference between gram neg and pos bacteria?

Answer 2

Gram neg have a thin peptidoglycan layer in the cell wall, also surrounded by an outer membrane containing lipopolysaccharides
Gram pos have a thick peptidoglycan layer in the cell wall

Question 3

What colour gram stains are gram neg and gram pos bacteria?

Answer 3

Purple - pos

Red - neg

Question 4

Ways of classifying bacteria

Answer 4

Growth
Shape - cocci, bacilli, spirilla, vibrios, corkscrew (spirochaetes)
Gram

Question 5

Shape classification meanings

Answer 5

Cocci - spherical
Bacilli - rods
Spirilla - spirals
Vibrios - comma
Spirochaetes - corkscrew

Question 6

Nomenclature of bacteria

Answer 6

Based on genus and species
eg staphylococcus aureus

Strains of species have similar characteristics
DNA typing techniques is used to identify strains

Question 7

NEISSERIA SPP

Answer 7

Neisseria meningitidis (meningococcus) 
- causes meningitis - inflammation of meninges and septicaemia , important when isolated from a sterile site eg blood cuktures or CSF
PCR available on EDTA 

Neisseria gonorrhoeae

• causes urethritis in men and pelvic inflammatory disease in women
• spread by sexual contact

Moraxella catarrhalis

• causative agent of RTI
• especially in those with underlying lung pathology

Question 8

SALMONELLA SPP

Answer 8

Does not ferment lactose
Salmonella enterica > 1500 serotypes
Whole genome sequencing now performed in reference lab
Self-limiting enterocolitis with or without bloody diarrhoea
Second commonest cause of bacterial diarrhoea in UK
Can be invasive ie enters blood stream

Question 9

Salmonella typhi

Answer 9

Distinct from salmonella enterica
Cause of typhoid fever
Fever, constipation early stages
Organism can be isolated from blood cuktures as well as faeces
Risk during foreign travel, vaccine available

Question 10

Helicobacter pylori

Answer 10

Curved rods - bacilli
Natural habitat is human stomach
Damages mucosa and causes ulcers
String risk factor for gastric adenocarcinoma

Question 11

Haemophilus influenzae

Answer 11

Exacerbation of COPD
Cocco-bacilli
Causes resp tract infection (second to S. pneumoniae)
Capsulate form was formerly an imporrtant cause if meningitis in children

Question 12

PSEUDOMONAS SPP.

Answer 12

Water and soil coloniser - drains, sinks, mops
May contaminate medical equipment
Hospital acquired cause of sepsis : eg UTI, bacteraemia, pneumonia (rare)
Feared resp pathogen in CF
Multi-drug resistance mechanisms
Limited treatment options

Question 13

Oral anaerobes

Answer 13

Prevotella 
Porphyromonas eg P gingivalis 
Pasteurella spp
Capnocytophyga spp
Important in aetiology of periodontal disease and may be part of polymicrobial dental abscesses 
Role in aspiration pneumonia 
Human and animal bite infections

Question 14

What are miscellaneous bacteria? Give examples

Answer 14

Bacteria that cannot be stained with gram’s method

Mycobacterium spp.
Spirochaetes
Chlamydia/Chlamydophilia

Question 15

Leprosy

Answer 15

Mycobacterium leprae - cannot be cultured
Mainly India, Nepal, Brazil, parts of Africa
Around 250,000 new cases per year worldwide
Attacks peripheral nerves

Question 16

Lyme disease

Answer 16

Transmitted by ticks
Stage 1 - skin rash appears at site of tick bite
Stage 2 - systemic illness occurs in some patients weeks or months later when patients suffer cardiac or neurological and musculoskeletal symptoms
Stage 3 - chronic disease, occurring years kater when patients present with chronic skin, nervous system or joint abnormalities

Diagnosed by clinical assessment and serology (antibody detection)

Question 17

how are bacteria identified - size, shape, growth, staining

Question 18

main structures and functions of a typical cell

Question 19

bacteria replication

Question 20

genetic variation

Question 21

detection and culture of bacteria