Bacteremia and Sepsis Flashcards
- presence of viable bacteria in the blood
- one of the most serious infections
Bacteremia
contamination of blood through phlebotomy
Pseudobacteremia
bacteremia present with the absence of physical signs/symptoms
Occult Bacteremia
Bacteremia plus clinical presentation of signs/symptoms of bacterial invasion and toxin production
Septicemia
Systemic response to infection sometimes accompanied by organ involvement
Sepsis
Sepsis accompanied by hypotension
Septic shock
Primary bacteremia
- arises from endovascular source
- i.e., patient with pneumonia gets into bloodstream
Secondary bacteremia
- arises from extravascular source
- i.e., catheters
Classification of Bacteremia by site of origin
Primary Bacteremia
Secondary Bacteremia
Bacteremia of Unknown Origin
Classification of Bacteremia by Causative agent
- 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)
Classification of Bacteremia by Place of Acquisition
- Community-acquired bacteremia: S. pneumo
- Nosocomial bacteremia: P. aeruginosa, Enterococcus
Classification of Bacteremia by Duration
- 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
Bacteremia (risk factors)
- immune competency
- increased use of invasive procedures increases risk
- age (very young and old at higher risk)
- antimicrobials: broad spectrum reduce normal flora
Bacteremia (causative agents)
- in the past: E. coli, P. aeruginosa, S. aureus, CoNS, Enterococcus
- recently: fungemias (Candida albicans, malassesia furfur)
- associated with community-acquired illness
- Optochin S, Sodium desoxycholate +
- capsule, IgA protease
S. pneumoniae
- UTI’s, bacteremia, other infections
- catalse +, coagulase +
- hyaluronidase, latex +
S. aureus
- blue/green on MAC
- oxidase +, glucose oxidizer, 42C
- capsule, motile, associated with nosocomial infection
- CF patients pneumonia
- Hot tub syndrome
P. aeruginosa
- # 1 colon flora, anaerobic
- tolerates bile
- vancomycin, kanamycin, colistin resistant
B. fragilis
Antimicrobial resistant bacteremia agents
- MRSA
- VRE (Vancomycin-resistant Enterococcus)
- ESBL (Extended spectrum beta lactamases)
Vaccine reduction of bacteremia
Hib and S. pneumoniae vaccines
Bateremia (pathogenesis)
- Disruption of skin or mucosa gives bacteria access to microvasculature
- Complications are metastatic infection (infection to multiple sites) and septic shock
Clinical syndromes associated with bacteremia
- 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
Bacteremia (Symptoms/Lab findings)
- 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
Blood culture contaminants
- CoNS, Corynebacterium, Bacillus, alpha hemolytic strep, Propionibacterium acnes
- skin flora contamination is expected (2-3%)
- should be < 3%, from one site
Blood Culture Collection (amount collected)
- neonates/children: < 1%
- adults: up to 4%
- dilution factor: 1:5 - 1:10
Blood Culture Collection (other concerns)
- 3 collections are recommended
- ideally collected before temperature rise in intermittent
- single blood cultures are not acceptable
Bacteremias that must be followed with Blood Cultures
- infective endocarditis
- S. aureus bacteremia
Blood culture medium
- Nutrient broth with SPS (anticoagulant)
- incubate at 37C for 5 days
Sodium polyanethol sulfonate (SPS)
- 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)
Blood Culture Additives
- Gelatin to counteract inhibitory action of SPS
- Antimicrobial removal device (ARD): absorbs antimicrobial
BD Septi-Chek system
- manual method
- rapid recovery of facultative bacteria and isolated colonies for ID and susceptibility
Lysis-Centrifugation
- manual method
- optimal recovery of unusually fastidious bacteria
BACTEC
- automated method
- measures CO2 production from microbe metabolism
BacT/ALERT
- automated method
- measures CO2 derived pH changes by colorimetric sensor
Special Blood Culture Cases (Francisella)
add L-cystine and glucose to liquid broth
Special Blood Culture Cases (Leptospira)
add 1-3 drops of SPS-blood to Fletcher’s medium, examine weekly with darkfield microscopy
Special Blood Culture Cases (Brucella)
- manual methods: hold up to 6 weeks
- automated methods: hold 10-14 days
Special Blood Culture Cases (Nutritionally Deficient Strep)
require 0.001% pyridoxal HCl
Special Blood Culture Cases (Campylobacter)
microaerophilic, 42C, curved GNR’s, fastidious
Special Blood Culture Cases (Coxiella)
- can’t be isolated by blood cultures
- diagnosed by serology
- causes Q fever
Special Blood Culture Cases (Bartonella)
- enriched media under increased CO2 for 3 weeks
- molecular methods are preferred
Special Blood Culture Cases (HACEK Group)
fastidious, hold cultures and subculture to enriched media
Special Blood Culture Cases (Mycobacteria)
Middlebrook based media, hold for 6 weeks
Contaminated disinfectants
- Benzalkonium chloride
- Povidone-iodine: Burkholderia cepacia
Contamination or Pathogen
- 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
