Gram Negative Bacteria

Question 1

Describe Neisseria Meninigitis?

Answer 1

Cocci

Causes meningitis which is the inflammation of meninges and septicaemia.

Question 2

Describe Nesseria Gonorrhoeae?

Answer 2

Cocci
Causes urethritis in men
Causes pelvic inflammatory disease in women
Spread by sexual contact

Question 3

Describe Morexella Catarrhalis?

Answer 3

Cocci

Causes respiratory tract infections

Question 4

What are coliforms?

Answer 4

Organisms which are in the Enterobacteriaceae family.

Mainly commensals of the human large intestine.

Question 5

Describe Escherichia coli?

Answer 5

Bacilli
Several virulence mechanisms- pili, capsule, ends/exotoxins.
Ferments lactose
Causes UTIs and diarrhoea (can be bloody)

Question 6

Describe Salmonella spp?

Answer 6

Bacilli
Does not ferment lactose
Causes diarrhoea
Can be invasive

Question 7

Describe Salmonella typhi?

Answer 7

Bacilli
Distinct from enterica
Causes typhoid fever/constipation

Question 8

What are some other common coliforms?

Answer 8

Shigella spp.
Klebsiella spp.
Proteus spp.

Question 9

Describe Campylobacter spp.?

Answer 9

Curved bacilli 
Domestic origin from chicken and animals
likes low oxygen levels
Transmitted via faecal-oral route
Causes diarrhoea

Question 10

Describe Helicobacter pylori?

Answer 10

Curved bacilli
Natural habitat in human stomach
Can cause damage to mucosa and stomach ulcers
Risk of gastric adenocarcinoma

Question 11

Describe Haemophilus influenzae?

Answer 11

Cocci-bacilli mix

Causes respiratory tract infections.

Question 12

Describe Pseudomonas spp.?

Answer 12

Curved bacilli
Water and soil coloniser
Multi drug resistance
Causes UTIs, bacteriaemia and rarely pneumonia.

Question 13

What are anaerobes?

Answer 13

Bacteria that live in the absence of oxygen.

Question 14

Describe Bacteroides fragilis?

Answer 14

Anaerobe
Part of normal colonic flora
May cause intra-abdominal abscesses.

Question 15

What are some oral anaerobes?

Answer 15

Prevotella
Porphyromonas
Pasteurella spp
Capnocytophyga spp

Question 16

What are some bacteria that can’t be stained using Gram’s Method?

Answer 16

Mycobacterium spp.
Spirochaetes
Chlamydia

Question 17

What causes tuberculosis?

Answer 17

Mycobacterium tuberculosis

Question 18

Describe Mycobacterium leprae?

Answer 18

Can’t be gram stained
Cannot be cultured
Attacks peripheral nerves

Question 19

What are Spirochaetes?

Answer 19

Long, spiral-shaped bacteria.
Not easily visualised by light microscopy.
Very difficult to culture (never Treponema pallidum).
Dark ground microscopy or immunofluorescence.
Often diagnosed by serology
Cannot be gram stained.

Question 20

What are some common spirochaete diseases and the organisms that cause them?

Answer 20

Treponema pallidum - Syphilis
Borrelia burgdorferi - Lyme disease
Leptospira interrogans- Leptospirosis

Question 21

What is syphilis ?

Answer 21

Primary - skin lesions
Secondary - systemic infections and rash
Tertiary- central nervous sytem infection

Question 22

What is Lyme’s disease?

Answer 22

Transmitted by ticks
Primary- skin rash at site of bite
Secondary- systemic illness months later when patients exp. cardiac or neurological symptoms.
Tertiary- Chronic disease, occurring years later when patients present with chronic skin, nervous system or joint abnormalities.

Question 23

Describe Chlamydia trachomatis?

Answer 23

Can’t be gram stained.
Causes tropical eye infections and genital and neonatal infections.
Commonest STI in UK
Can cause pelvic inflammatory disease and infertility in women.