Microbiology

Question 1

Describe how you would identify a bacteria as Salmonella using Microbiology tests including differentiating it from Shigella? (4)

Answer 1

Salmonella is a gram-negative bacilli. Gram Stain= Pink. (1)

Bacilli Appearance= Rod shaped. (1)

MacConkey Agar tests for fermentation of lactose, Salmonella does not therefore plate remains clear (fermenters go pink). (1)

Do serotyping (API strip) to confirm Salmonella vs Shigella. (1)

Question 2

What do beta lactam antibiotics target?

Answer 2

-

Question 3

Give four types of beta lactam antibiotics

Answer 3

Question 4

Why are mycoplasma resistant to beta-lactams?

Answer 4

They have no cell wall. (beta lactams inhibit peptidoglycan synthesis)

Question 5

What pathogen is most commonly isolated in chronic diarrhoea in someone with HIV?

Answer 5

Cryptosporidium parvum (protozoan parasite)

Question 6

what is co-trimoxazole a combination of and what do they do?

Answer 6

co-trimoxazole = TRIMethoprim + sulfamethOXAZOLE

Inhibit folate synthesis

Question 7

What shape are neisseria bacteria?

Answer 7

Question 8

What shape bacteria is haemophilus influenzae?

Answer 8

Question 9

How would you identify pseudomonas?

Answer 9

• gram neg rod
• non-lactose fermenting
• oxidase positive

Question 10

Which gram positive bacteria are coagulase positive?

Answer 10

Question 11

What stain is used for TB?

Answer 11

Zeihl-Nielson

Question 12

What antibiotic can cause C. diff colonisation?

Answer 12

Clindamycin

Question 13

Four steps of gram staining?

Answer 13

“Come In And Stain”

• Crystal violet: primary stain
• Iodine: binds to crystal violet and traps it in the cell
• Alcohol wash
• Safranin: counterstain

Question 14

Why do gram positives and gram negatives appear different under staining?

Question 14

Why do gram positives and gram negatives appear different under staining?

Answer 14

• Gram positive: purple due to thick peptidoglycan wall retaining crystal violet
• Gram negative: pink as they retain the safranin counterstain

Question 15

How would you identify E. coli?

Answer 15

Question 16

How would you differentiate pseudomonas from shigella/salmonella?

Answer 16

Question 17

How would you differentiate between Shigella and Salmonella?

Answer 17

Question 18

What shape bacteria are neisseria species?

Answer 18

Question 19

What agar would you use to identify H. influenzae?

Answer 19

Question 20

Give three bacteria that are gram negative and comma shaped.

Answer 20

Question 21

What would a microbiologist see on a histology slide of TB? (weakly-gram positive aerobic bacillus)

Answer 21

Caseating granulomata

Question 22

What class of antibiotic is ceftriaxone / cefotaxime?

Answer 22

Question 23

What antibiotic can be given for prophylactic treatment to avoid meningitis?

Answer 23

Ciproflaxacin

Question 24

What class of antibiotic is ciprofloxacin and how does it work?

Answer 24

Question 25

Definition of a commensal microorganism?

Answer 25

The microorganism can be cultured from the host but isn't causing disease (also known as colonisation or asymptomatic carriage)

Question 26

Definition of an infection by a microorganism?

Answer 26

The microorganism can be cultured from the host and is causing disease

Question 27

Definition of an opportunistic pathogen/infection?

Answer 27

refers to microorganisms that only cause disease when a hosts defences are somehow compromised

Question 28

Definition of virulence/pathogenicity?

Answer 28

the degree to which a microorganism is pathogenic

Question 29

What is acid fastness?

Answer 29

A microorganisms ability to resist decolorisation by acids during lab staining procedures

Question 30

what are the two main forms of fungi?

Answer 30

Question 31

how do yeast divide?

Answer 31

Question 32

what does the cell wall of fungi usually contain?

Answer 32

Question 33

what ending do anti-fungal drugs usually have?

Answer 33

Question 34

what's the most pathogenic candida species?

Answer 34

Question 35

what's the most pathogenic aspergillus species?

Answer 35

Question 36

where do aspergillus fumigatus usually infect the body?

Answer 36

Question 37

where does Candida albicans usually infect the body?

Answer 37

Question 38

what two species of candida can cause thrush?

Answer 38

candida albicans candida glabrata

Question 39

what's the name of the structures that mould grows by making?

Answer 39

Question 40

give the names of two drugs that inhibit ergosterol synthesis in fungi.

Answer 40

Question 41

into what three groups can worms be divided into roughly by appearance?

Answer 41

Question 42

what's the definition of the pre-patent period with worms?

Answer 42

Question 43

what types of immunoglobulin are involved in the response to nematodes?

Answer 43

Question 44

Two most common bacterial causes of cellulitis?

Answer 44

Question 45

Antibiotics for cellulitis?

Answer 45

Question 46

Main side effect of vancomycin?

Answer 46

nephrotoxicity