Bacterial pathogens

Question 1

Gram + cocci

Answer 1

Staphylococcus aureus
Streptococcus pyogenes
Streptococcus agalactiae

Question 2

Gram - cocci

Answer 2

Neisseria meningitidis

Neisseria gonorrhoeae

Question 3

Gram + bacilli

Answer 3

Bacillus anthracis
Clostridium difficile
Listeria monocytogenes
Corynebacterium diptheriae

Question 4

Gram - bacilli

Answer 4

Salmonella typhi
Shigella spp
Escherichia coli
Proteus ssp
Yersinia pestis

Question 5

Gram - coccobacilli

Answer 5

Haemophilus
Bordetella
Brucella
Pasteurella

Question 6

Spiral bacteria

Answer 6

Helicobacter
Campylobacter
Borrielia
Leptospira
Treponema pallidum

Question 7

Cell structure

Answer 7

Gram + have thicker cell wall than Gram -

Gram + thick wall retains blue black colour of stain

Question 8

Stain colour

Answer 8

Gram + = Blue black

Gram - = pinky red

Question 9

Cell shape

Answer 9

Cocci are circular

Bacilli are flattened oval

Question 10

Why do bacteria cause infections

Answer 10

Host factors, Bacterial factors, opportunity

Question 11

Host factors

Answer 11

Immune system, devices

Question 12

Bacterial factors

Answer 12

Virulence, resistance, ability to survive in environment

Question 13

Opportunity

Answer 13

Exposure, normal flora

Question 14

E.Coli and UTI’s

Answer 14

• Part of normal bowel flora in most humans
• Colonisation of urethral meatus
• Able to adhere to uroepithelial cells and triggers inflammatory response in bladder
• develops resistance to antibiotics

Question 15

S. AUREUS and skin infections

Answer 15

• Carried in nasal carriage in up to 50% of people
• Adheres to damaged skin
• Produces exoenzymes and toxins that damage tissue

Question 16

Staphylococccus aureus features

Answer 16

• Causes skin/soft tissue infections
• Bacteraemia, septicaemia
• Endocarditis, pneumonia

Question 17

Staphylococcus epidermis

Answer 17

• opportunistic pathogen
• Most people carry on skin
• Causes infection with foreign bodies such as catheters etc
• Adheres to plastic/metals using glycocalyx (slime)

Question 18

Streptococcus pyogenes

Answer 18

• Commonest cause of bacterial sore throat
• Scarlet Fever, necrotising fasciitis and other SSTI’s
• Invasive infections such as pneumonia

Question 19

Streptococcus pneumoniae

Answer 19

• commonest cause of bacterial pneumonia
• Commonest cause of bacterial meningitis
• can cause other common childhood infections like otitis media

Question 20

Streptococcus agalactiae

Answer 20

• also known as group B strep

- Commonest cause of bacterial meningitis and sepsis in neonates (3 months and under)

Question 21

Streptococcus milleri complex

Answer 21

• 3 closely related species of pus-forming streptococci

- Associated with abscesses - dental, lung, liver, brain and others

Question 22

Viridans streptococci

Answer 22

• Collective name for a number of species of haemolytic streptococci that inhabit the URT
• cause sub-acute bacterial endocarditis

Question 23

Streptococcus gallolyticus

Answer 23

• Type of alpha-haemolytic streptococcus in bowel flora

- This organism can cause bacteraemia due to colonic malignancies

Question 24

Listeria monocytogenes

Answer 24

• Gram + bacillus
• rare but significant cause of sepsis and meningitis during pregnancy and neonates
• Zoonosis - able to grow at low temps
• unpasteurised milk can be a cause

Question 25

Corynebacterium species

Answer 25

- Gram + bacillus - Most of the species are commensals of the skin and URT - Corynebacterium diphtheriae causes diphtheria

Question 26

Propionibacterium acnes

Answer 26

- Gram + bacillus | - Now called Cutibacterium acne - causes acne

Question 27

Enterobacteriaceae (coliforms)

Answer 27

- A number of species of gram - bacteria found in bowel flora - include Escherichia coli, Enterobacter cloacae

Question 28

E.coli

Answer 28

- Commonest cause of UTI - commonest cause of bacteraemia - Cause of nosocomial infections - pneumonia, wound infections - certain toxigenic strains associated with severe diarrhoea and HUS

Question 29

Pseudomonas aeruginosa

Answer 29

- Multi-resistant Gram - bacteria - Can cause respiratory infections, UTI's and other infections - produces green pigment

Question 30

Neisseria meningitidis

Answer 30

- Gram negative diplococcus - causes meningococcal sepsis (meningitis) - Classic presentation is a non-branching rash

Question 31

Neisseria gonorrhoeae

Answer 31

- Gram - diplococcus - Causes gonorrhoeae - Rarely causes secondary invasive infection

Question 32

Haemophilus influenzae

Answer 32

- Gram - bacillus - normal RT flora - causes respiratory tract infections such as pneumonia - The vaccine only prevents type B infections

Question 33

Anaerobes

Answer 33

- Clostridium species (c.difficile, c.tetani etc) | - Often part of polybacterial infections

Question 34

Mycobacterium species

Answer 34

- Do NOT stain using gram stains - referred to as Acid fast Bacilli - Mycobacterium tuberculosis - TB - Atypical Mycobacteria cause respiratory infections

Question 35

Bacteria without a conventional cell wall

Answer 35

- Chlamydia species, C. trachomatis - common STI | - Mycoplasma species M. pneumoniae - common cause of RTI

Question 36

Spirochaetes

Answer 36

- Treponema pallidum - causes syphilis | - Other species cause Leptospirosis and Lyme disease