(II) Gram Negative Rods - (1) Enterobacteriaceae Overview

Question 1

Antibiotics for Enterobacteriaceae infection:

Older drugs: Ampicillin (but obsolete now as many strains produce beta-lactamases)

Newer drugs: […]

Alternative drugs:
[…]

Rehydration important in diarrhoeal diseases!

Answer 1

Antibiotics for Enterobacteriaceae infection:

Older drugs: Ampicillin (but obsolete now as many strains produce beta-lactamases)

Newer drugs: Cephalosporins such as ceftriaxone (but extended- spectrum beta-lactamase producing strains have arisen)

Alternative drugs:
- Synergistic combinations like co-amoxiclav and pip-tazo, or co-trimoxazole (for UTI, but resistance is increasing)
- Quinolones like ciprofloxacin (but resistance is emerging)
- Aminoglycosides like gentamicin & amikacin (effective but toxic, need TDM = therapeutic drug monitoring)
- Carbapenems like imipenem, meropenem

Rehydration important in diarrhoeal diseases!

Question 2

Enterobacteria are grown on […] agar

Answer 2

Enterobacteria are grown on MacConkey agar

MacConkey agar is a selective medium containing bile salts

Can be lactose fermenting (LF)(pink/red colonies) or non-lactose fermenting (NLF)(yellow/pale colourless colonies)

Question 3

Enterobacteriaceae are generally oxidative […]

Answer 3

Enterobacteriaceae are generally oxidative negative
Because they are facultative anaerobes

Question 4

The Enterobacteriaceae are a large family of Gram-negative bacteria that includes, along with many harmless symbionts, many of the more familiar pathogens. What are the 5 important enterobacteriaceae?

• […] (Lactose fermenting)
• […] (Lactose fermenting)
• […] (Non lactose fermenting)
• […] (Non lactose fermenting)
• […] (Non lactose fermenting)

Answer 4

The Enterobacteriaceae are a large family of Gram-negative bacteria that includes, along with many harmless symbionts, many of the more familiar pathogens. What are the 5 important enterobacteriaceae?

• Escherichia coli (Lactose fermenting)
• Klebsiella (Lactose fermenting)
• Shigella (Non lactose fermenting)
• Proteus (Non lactose fermenting)
• Salmonella (Non lactose fermenting)
  Shigella and Salmonella are NOT NORMAL GUT FLORA. The rest are.

Following bacteria also part of this. but just for classification (or irrelevance in exams, are excluded)
Yersinia pestis (under fastidious gram negative rods)
Enterobacter
Serratia
Citrobacter.

Question 5

Typing methods for enterobacteria includes somatic […] and flagellar […] antigens

Answer 5

Typing methods for enterobacteria includes somatic O and flagellar **H **antigens

Question 6

We dont test enterobacteria for oxidase negativity anymore. Now we use […]

Answer 6

We dont test enterobacteria for oxidase negativity anymore. Now we use Mass Spectroscopy

Talk about high tech

Question 7

What are the nocosomial causes of enterobacteriae infections:

[…]

Answer 7

What are the nocosomial causes of enterobacteriae infections:

• Due to GIT surgery (release of bacteria, causing wound infections, peritonitis, abdominal & pelvic abscesses)
• Due to neurosurgery or head trauma (causes meningitis)
• Due to prolonged hospitalization as broad-spectrum antibiotics used select for survival of resistant strains of coliforms (commonly results in infection of urinary tract, wounds and lungs)