Intra-abdominal infections

Question 1

Examples of intra-abdominal infections

Answer 1

Acute diverticulitis
Cholecystitis (with secondary infection)
Ascending cholangitis
Appendicitis
Spontaneous bacterial peritonitis
Intra-abdominal abscess

Question 2

Common causes of intra-abdominal infections

Answer 2

Anaerobes (e.g. bacteroides and clostridium)
E. coli
Klebsiella
Enterococcus
Streptococcus

Question 3

Treating intra-abdominal infections

Answer 3

When treating intra abdominal infections a broad spectrum of antibiotic cover is required unless culture results are available. This is to cover gram positive, gram negative and anaerobic bacteria. Always follow the local guidelines as these are frequently changed based on local resistance and infection control issues.

Question 4

What Abx can be used for intra-abdominal infections?

Answer 4

• Co-amoxiclav
• Quinolones
• Metronidazole
• Gentamicin
• Vancomycin
• Cephalosporins
• Tazocin and meropenem

Question 5

Co-amoxiclav

Answer 5

This provides good gram positive, gram negative and anaerobic cover. It does not cover pseudomonas or atypical bacteria.

Question 6

Quinolones

Answer 6

Ciprofloxacin and levofloxacin provide reasonable gram positive and gram negative cover and also cover atypical bacteria however they don’t cover anaerobes so are usually paired with metronidazole when treating intra-abdominal infections.

Question 7

Metronidazole

Answer 7

This provides exceptional anaerobic cover but does not provide any cover against aerobic bacteria.

Question 8

Gentamicin

Answer 8

This provides very good gram negative cover with some gram positive cover particularly against staphylococcus. It is bactericidal so works to kill the bacteria rather than just slowing it down.

Question 9

Vancomycin

Answer 9

This provides very good gram positive cover including MRSA. It is often combined with gentamicin (to cover gram negatives) and metronidazole (to cover anaerobes) in patients with penicillin allergy.

Question 10

Cephalosporin

Answer 10

These provide good broad spectrum cover against gram positive and gram negative bacteria but are not very effective against anaerobes. They are often avoided due to the risk of developing C. difficile infection.

Question 11

Tazocin and meropenem

Answer 11

Piperacillin/Tazobactam (Tazocin) and Meropenem are heavy hitting antibiotics that cover gram positive, gram negative and anaerobic bacteria. They don’t cover atypical bacteria or MRSA and tazocin doesn’t cover ESBLs but they cover almost everything else. They are usually reserved for very unwell patients or those not responding to other antibiotics.

Question 12

Common regimes for intra-abdominal infections

Answer 12

• Co-amoxiclav alone
• Amoxicillin plus gentamicin plus metronidazole
• Ciprofloxacin plus metronidazole (penicillin allergy)
• Vancomycin plus gentamicin plus metronidazole (penicillin allergy)

Antibiotics can be given orally where an oral version is avaliable, for example in mild diverticulitis, or intravenous in more serious infections.

A stat dose of gentamicin is often added to regimes not including gentamicin if the patient is severely septic to provide initial strong bactericidal gram negative action.

Question 13

Spontaneous bacterial peritonitis

Answer 13

This is a serious infection that typically occurs in patients with liver failure.

Piperacillin/Tazobactam (Tazocin) is often first line
Cephalosporins such as cefotaxime are also often used
Levofloxacin plus metronidazole is an common alternative in penicillin allergy