Microbiology of Intra-abdominal Sepsis

Question 1

What are aerobes and give examples?

Answer 1

Organism that grow better with oxygen but can also grow without it; these are the majority of human pathogens, e.g:
Staphylococci - gram positive cocci in clusters
Streptococci - gram positive cocci in chains
Enterococci - gram positive
Coliforms - gram negative bacilli

Question 2

What antibiotic are the aerobes sensitive to?

Answer 2

Metronidazole

Question 3

What are strict aerobes and give examples?

Answer 3

Organism that REQUIRE oxygen for growth, e.g: pseudomonas sp. (gram negative bacilli commonly found as an opportunistic pathogen in immunocompromised/suppressed people)

Question 4

What antibiotic are the strict aerobes sensitive to?

Answer 4

Gentamicin

Question 5

What are the anaerobes and give examples?

Answer 5

Organism that WILL NOT grow in the presence of oxygen, e.g:
Clostridium sp. (gram positive bacilli)
Bacteroides sp. (gram positive bacilli)
Anaerobic cocci

Question 6

What antibiotics are the anaerobes sensitive to?

Answer 6

Metronidazole

Question 7

What are the coliforms, give examples and the antibiotic used?

Answer 7

Aerobic organisms (facultative anaerobes) that inhabit the large bowel and are gram negative baccili, e.g:
E. coli
Klebsiella sp.
Proteus sp.
Enterobacter sp.
Serratia sp.

Antibiotic - gentamicin

Question 8

Normal flora of the oral cavity?

Answer 8

Mucosal shedding inhibits colonisation of the mucosa; examples of organism found on swabbing the mucosa inc. Candida sp. and Neisseria

Dental plaques have dense bio-films, leading to polymicrobial growths, e.g: Strep. “viridans”, Staph

Question 9

Normal flora of the stomach and duodenum?

Answer 9

Low pH and so usually sterile; there is some Candida sp. and Staphylococcus sp.
Helicobacter pylori (able to withstand pH, invades local mucosa and can cause ulcers)

Question 10

Normal flora of the jejunum?

Answer 10

Small numbers, e.g: Coliforms and anaerobes

Question 11

Normal flora of the colon?

Answer 11

Abundant nutrients and high bacterial load, e.g: may anaerobes, coliforms and enterococci

Question 12

Normal flora of the bile ducts?

Answer 12

Usually sterile

Question 13

Normal flora of the peritoneal cavity?

Answer 13

Normally sterile; leakage of contents into the cavity causes peritonitis

Question 14

Causes of peritonitis?

Answer 14

Perforated duodenal ulcer, causing H. pylori leakage

Perforated appendix

Perforated diverticulum (diverticulitis)

Perforated tumour

Surgery

Question 15

How do abscesses form in the peritoneal cavity?

Answer 15

Micro-organisms leak in and form abscesses (of pus cells and organisms)

Question 16

Management of abscesses?

Answer 16

Large abscesses - no blood supply and so poor antibiotic penetration; DRAINAGE is essential

Small abscesses - may be treated with antibiotics

Question 17

What are the empiric antibiotics used in treatment of intra-abdominal sepsis?

Answer 17

Gentamicin (to cover coliforms)
Metronidazole (to cover anaerobes)
Amoxicillin (to cover enterococci)

Question 18

Prophylactic antibiotics before GI tract/hepatobiliary surgery?

Answer 18

Gentamicin and metronidazole

Question 19

Definition of colonisation?

Answer 19

Presence of a microbe in the human body that does not cause infection due to a specific inflammatory response

Question 20

Definition of infection?

Answer 20

Occurrence of inflammation due to a microbe strain

Question 21

Definition of bacteraemia?

Answer 21

The presence of viable bacteria in the blood; usually causes sepsis, but not always

Question 22

Definition of sepsis?

Answer 22

Systemic inflammatory response to infection

Question 23

3 factors that make recognition of infection difficult?

Answer 23

Abnormal host response, e.g: with age, immunosuppression, co-morbidities, drugs and genetics

Abnormal microbe response, e.g: virulence expression latency (intracellular predilection for certain sites)

Site of infection, e.g: “deep” infection, e.g: endocarditis, bone and joint infections; also, occult infections

Question 24

Local symptoms of infection?

Answer 24

Pain, tenderness and guarding

Blood PR in some

Question 25

Systemic symptoms of infection?

Answer 25

Fever, chills and rigors
Nausea and vomiting
Constipation or diarrhoea
Malaise 
Anorexia

Question 26

Progression of sepsis?

Answer 26

Colonisation leads to infection:
SIRS
Sepsis
Severe sepsis
Septic shock

Mortality increases with each stage

Question 27

Definition of SIRS?

Answer 27

Systemic Inflammatory Response Syndrome - a non-specific clinical response inc. 2 or more of the following:
Temp >38C or 90 bpm
RR >20 / min
WCC >12,000 /mm3 or 10% immature neutrophils

Question 28

Causes of SIRS?

Answer 28

Infection, trauma, burns, pancreatitis and other insults

Question 29

Definition of sepsis?

Answer 29

SIRS with a presumed/confirmed infectious process

Question 30

Definition of severe sepsis?

Answer 30

Sepsis with hypoperfusion, i.e: signs of one or more of the following:
Renal
Respiratory 
Hepatic
Haematological, e.g: disseminated intravascular coagulation
CNS
Unexplained lactic acidosis (metabolic)
CVS (hypotension)

Question 31

Definition of septic shock?

Answer 31

Severe sepsis with hypotension refractory to adequate volume resuscitation, i.e: treatments do not correct it:
Hypotension defined as 40 mmHg from baseline (in the absence of other causes of hypotension)

Question 32

SOFA score of more than 2 means?

Answer 32

Overall mortality risk of 10% in a general hospital population, with suspected infection

Question 33

Diagnosing infection investigations?

Answer 33

WCC, CRP (marker of inflammation, not infection), platelet count, clotting

Microbiology - CULTURE (blood), stool, urine, wound, tissue, etc

Microscopy of stool, urine, CSF, sputum

Serology

Antigen detection

PCR

Question 34

Common bacterial causes of sepsis in the community?

Answer 34

E. coli (urine, abdomen)

S. pneumoniae (respiratory)

S. aureus (usually MRSA, in skin)

Question 35

Common bacterial causes of sepsis in the hospital?

Answer 35

E. coli (catheter related or abdomen)

S. aureus (may be MRSA and line/wound related)

Coagulase negative Staphylococci (line/prosthesic related)

Enterococci (urine, wound or line)
Klebsiella spp. (urine, wound)

Pseudomonas spp.

Question 36

Two forms of management of infection syndrome?

Answer 36

Antibiotics

Supportive:
Fluids
Analgesia
Need for surgery
VTE propylaxis
O2
Controlling electrolyte balance
Need for transfusion

Question 37

How should antibiotic treatment of intra-abdominal sepsis proceed?

Answer 37

Total IV/PO: 7-10 days

IV amoxicillin, metronidazole, gentamicin then step down to PO co-trimoxazole and metronidazole

If penicillin-allergic, IV vancomycin + metronidazole + gentamicin, then step down to PO co-trimoxazole + metronidazole

Question 38

Concerns with gentamicin?

Answer 38

Nephrotoxicity

Question 39

Protocol when using gentamicin?

Answer 39

Limit Duration:
72 hours then ID/microbiology approval required
24 hours if concern with renal function

Monitor renal function daily

Correct dosing for overweight patients

Maximum dose of 600mg

Clear exclusion criteria

Use nomogram or dose when

Question 40

Relationship between hypotension and mortality with sepsis?

Answer 40

For every hour of hypotension (low blood pressure) there is an increased risk of death

Question 41

Sepsis six bundle?

Answer 41

Must be done in one hour:
Give high flow oxygen
Target SaO2 94-98% unless COPD patients (88-92%) or severe sepsis

Start IV fluid resuscitation
(500mls saline STAT) - increase preload to improve stroke volume

Take blood cultures and other cultures, urine or wound swabs

Give IV antibiotics

Measure lactate and FBC
(higher lactate may require higher level of care)

Monitor accurate hourly urine output (useful assessment of kidney perfusion)

Question 42

What does a higher lactate level indicate?

Answer 42

Anaerobic glycolysis is occurring due to tissue hypoperfusion and tissue dysoxia

Reduced metabolism (hepatic and renal)