Bacteria

Question 1

How can bacteria be categorised?

Question 2

What is the difference between aerobic and anaerobic bacteria?

Answer 2

Aerobic bacteria require oxygen whereas anaerobic bacteria do not.

Question 3

What is the difference between gram positive, gram negative and atypical bacteria?

Answer 3

• Gram positive bacteria have a thick peptidoglycan cell wall that stains with crystal violet stain.
• Gram negative bacteria don’t have this thick peptidoglycan cell wall and don’t stain with crystal violet stain but will stain with other stains.
• Atypical bacteria cannot be stained or cultured in the normal way.

Question 4

How are bacteria classified on their shapes?

Answer 4

Rod shaped bacteria are called bacilli and circular shaped bacteria are called cocci.

Question 5

What are the two main steps involved in a gram stain?

Answer 5

• Add a crystal violet stain which binds to molecules in the thick peptidoglycan cell wall in gram positive bacteria turning them violet.
• Then add a counterstain (such as safranin) which binds to the cell membrane in bacteria that don’t have a cell wall (gram negative bacteria) turning them red/pink.

Question 6

Give examples of gram positive cocci

Answer 6

• Staphylococcus
• Streptococcus
• Enterococcus

Question 7

Give examples of gram positive rods

Answer 7

Use the mnemonic “corneyMike’slistofbasiccars”:

Corney – Corneybacteria

Mike’s – Mycobacteria

List of – Listeria

Basic – Bacillus

Cars – Nocardia

Question 8

Give examples of gram negative anaerobes

Answer 8

Use the mnemonic “CLAP”:

C – Clostridium

L – Lactobacillus

A – Actinomyces

P – Propionibacterium

Question 9

Common gram negative organisms are:

Answer 9

• Neisseria meningitis
• Neisseria gonorrhoea
• Haemophilia influenza
• E. coli
• Klebsiella
• Pseudomonas aeruginosa
• Moraxella catarrhalis

Question 10

What is the definition of atypical bacteria and what condition is it commonly implicated in?

Answer 10

The definition of atypical bacteria is that they cannot be cultured in the normal way or detected using a gram stain.

Atypical bacteria are most often implicated in pneumonia.

Question 11

Which atypical bacteria can cause atypical pneumonia?

Answer 11

legions of psittaci MCQs

• ​​Legions – Legionella pneumophila
• Psittaci – Chlamydia psittaci
• M – Mycoplasma pneumoniae
• C – Chlamydydophila pneumoniae
• Qs – Q fever (coxiella burneti)

Question 12

What is Methicillin-Resistant Staphylococcus Aureus (MRSA)?

Answer 12

MRSA refers to staphylococcus aureus bacteria that have become resistant to beta-lactam antibiotics such as penicillins, cephalosporins and carbapenems.

Question 13

How are patients being admitted for surgery or treatment screened for MRSA and how is it eradicated?

Answer 13

Patients are screened for MRSA infection by taking nasal and groin swabs.

Eradication usually involves a combination of chlorhexidine body washes and antibacterial nasal creams.

Question 14

What are the antibiotic treatment options for MRSA?

Answer 14

• Doxycycline
• Clindamycin
• Vancomycin
• Teicoplanin
• Linezolid

Question 15

What are Extended Spectrum Beta Lactamase bacteria (ESBLs)?

Answer 15

• ESBLs are bacteria that have developed resistance to beta-lactam antibiotics.
• They produce beta lactamase enzymes that destroy the beta-lactam ring on the antibiotic.
• They can be resistant to a very broad range of antibiotics.
• ESBLs tend to be e. coli or klebsiella and typically cause urinary tract infections but can also cause other infections such as pneumonia.

Question 16

What antibiotics are ESBLs sensitive to?

Answer 16

They are usually sensitive to carbapenems such as meropenem or imipenem.