Bacteremia and Sepsis

Question 1

• presence of viable bacteria in the blood

- one of the most serious infections

Answer 1

Bacteremia

Question 2

contamination of blood through phlebotomy

Answer 2

Pseudobacteremia

Question 3

bacteremia present with the absence of physical signs/symptoms

Answer 3

Occult Bacteremia

Question 4

Bacteremia plus clinical presentation of signs/symptoms of bacterial invasion and toxin production

Answer 4

Septicemia

Question 5

Systemic response to infection sometimes accompanied by organ involvement

Answer 5

Sepsis

Question 6

Sepsis accompanied by hypotension

Answer 6

Septic shock

Question 7

Primary bacteremia

Answer 7

• arises from endovascular source

- i.e., patient with pneumonia gets into bloodstream

Question 8

Secondary bacteremia

Answer 8

• arises from extravascular source

- i.e., catheters

Question 9

Classification of Bacteremia by site of origin

Answer 9

Primary Bacteremia
Secondary Bacteremia
Bacteremia of Unknown Origin

Question 10

Classification of Bacteremia by Causative agent

Answer 10

• Gram-positive bacteremia: S. pneumo, S. aureus, Enterococcus faecium
• Gram-negative bacteremia: E. coli, P. aeruginosa, B. frag
• Polymicrobial bacteremia (IV drug use, burns, GI sources)

Question 11

Classification of Bacteremia by Place of Acquisition

Answer 11

• Community-acquired bacteremia: S. pneumo

- Nosocomial bacteremia: P. aeruginosa, Enterococcus

Question 12

Classification of Bacteremia by Duration

Answer 12

• Transient bacteremia: result of procedure, caused by flora
• Intermittent bacteremia: result of abscess (meningococcemia, gonococcemia)
• Continuous bacteremia: intravascular source, continuously present, i.e., prosthetic heart valve

Question 13

Bacteremia (risk factors)

Answer 13

• immune competency
• increased use of invasive procedures increases risk
• age (very young and old at higher risk)
• antimicrobials: broad spectrum reduce normal flora

Question 14

Bacteremia (causative agents)

Answer 14

• in the past: E. coli, P. aeruginosa, S. aureus, CoNS, Enterococcus
• recently: fungemias (Candida albicans, malassesia furfur)

Question 15

• associated with community-acquired illness
• Optochin S, Sodium desoxycholate +
• capsule, IgA protease

Answer 15

S. pneumoniae

Question 16

• UTI’s, bacteremia, other infections
• catalse +, coagulase +
• hyaluronidase, latex +

Answer 16

S. aureus

Question 17

• blue/green on MAC
• oxidase +, glucose oxidizer, 42C
• capsule, motile, associated with nosocomial infection
• CF patients pneumonia
• Hot tub syndrome

Answer 17

P. aeruginosa

Question 18

• # 1 colon flora, anaerobic
• tolerates bile
• vancomycin, kanamycin, colistin resistant

Answer 18

B. fragilis

Question 19

Antimicrobial resistant bacteremia agents

Answer 19

• MRSA
• VRE (Vancomycin-resistant Enterococcus)
• ESBL (Extended spectrum beta lactamases)

Question 20

Vaccine reduction of bacteremia

Answer 20

Hib and S. pneumoniae vaccines

Question 21

Bateremia (pathogenesis)

Answer 21

• Disruption of skin or mucosa gives bacteria access to microvasculature
• Complications are metastatic infection (infection to multiple sites) and septic shock

Question 22

Clinical syndromes associated with bacteremia

Answer 22

• Catheter-related bloodstream infections: S. epi, Enterococcus, S. aureus
• UTI’s: E. coli, common in elderly
• Pneumonias: S. pneumo, H. flu, S. aureus, P. aeruginosa
• Intraabdominal infections: primary and secondary peritonitis (E. coli, Kleb. pneumo, Enterococcus)
• Skin infections: bed ridden patients and diabetics
• Infective endocarditis: CoNS, Viridans strep, S. aureus
• Musculoskeletal infections: bone capillaries, prosthetic joints

Question 23

Bacteremia (Symptoms/Lab findings)

Answer 23

• Shaking, chills, fever, hypotheremia
• Thrombocytopenia, Leukocytosis or Leukopenia, Lactic acidosis, hypoglycemia or hyperglycemia
• Abnormal liver function tests
• coagulopathy
• DIC, elevated C-reactive protein, haptoglobin, fibrinogen

Question 24

Blood culture contaminants

Answer 24

• CoNS, Corynebacterium, Bacillus, alpha hemolytic strep, Propionibacterium acnes
• skin flora contamination is expected (2-3%)
• should be < 3%, from one site

Question 25

Blood Culture Collection (amount collected)

Answer 25

- neonates/children: < 1% - adults: up to 4% - dilution factor: 1:5 - 1:10

Question 26

Blood Culture Collection (other concerns)

Answer 26

- 3 collections are recommended - ideally collected before temperature rise in intermittent - single blood cultures are not acceptable

Question 27

Bacteremias that must be followed with Blood Cultures

Answer 27

- infective endocarditis | - S. aureus bacteremia

Question 28

Blood culture medium

Answer 28

- Nutrient broth with SPS (anticoagulant) | - incubate at 37C for 5 days

Question 29

Sodium polyanethol sulfonate (SPS)

Answer 29

- anticoagulant in blood culture bottles - neutralizes bactericidal activity (complement) - prevention of phagocytosis - inactivation of certain antimicrobial agents (streptomycin, gentamycin) - may inhibit Peptostreptoccus, N. gonorrhoeae, N. meningitidis, Gardnerella)

Question 30

Blood Culture Additives

Answer 30

- Gelatin to counteract inhibitory action of SPS | - Antimicrobial removal device (ARD): absorbs antimicrobial

Question 31

BD Septi-Chek system

Answer 31

- manual method | - rapid recovery of facultative bacteria and isolated colonies for ID and susceptibility

Question 32

Lysis-Centrifugation

Answer 32

- manual method | - optimal recovery of unusually fastidious bacteria

Question 33

BACTEC

Answer 33

- automated method | - measures CO2 production from microbe metabolism

Question 34

BacT/ALERT

Answer 34

- automated method | - measures CO2 derived pH changes by colorimetric sensor

Question 35

Special Blood Culture Cases (Francisella)

Answer 35

add L-cystine and glucose to liquid broth

Question 36

Special Blood Culture Cases (Leptospira)

Answer 36

add 1-3 drops of SPS-blood to Fletcher's medium, examine weekly with darkfield microscopy

Question 37

Special Blood Culture Cases (Brucella)

Answer 37

- manual methods: hold up to 6 weeks | - automated methods: hold 10-14 days

Question 38

Special Blood Culture Cases (Nutritionally Deficient Strep)

Answer 38

require 0.001% pyridoxal HCl

Question 39

Special Blood Culture Cases (Campylobacter)

Answer 39

microaerophilic, 42C, curved GNR's, fastidious

Question 40

Special Blood Culture Cases (Coxiella)

Answer 40

- can't be isolated by blood cultures - diagnosed by serology - causes Q fever

Question 41

Special Blood Culture Cases (Bartonella)

Answer 41

- enriched media under increased CO2 for 3 weeks | - molecular methods are preferred

Question 42

Special Blood Culture Cases (HACEK Group)

Answer 42

fastidious, hold cultures and subculture to enriched media

Question 43

Special Blood Culture Cases (Mycobacteria)

Answer 43

Middlebrook based media, hold for 6 weeks

Question 44

Contaminated disinfectants

Answer 44

- Benzalkonium chloride | - Povidone-iodine: Burkholderia cepacia

Question 45

Contamination or Pathogen

Answer 45

- S. aureus, E. coli, Enterics, S. pneumo, P. aeruginosa, Candida are almost always true pathogens - CoNS, diptheroids, skin flora should be questioned - more than one bottle growing the same thing usually indicates significance - growth of skin biota in single bottle usually indicates contaminant