Download Bacteremia and Sepsis - University of Yeditepe Faculty of

Gülden Çelik
Learning Objectives
At the end of this lecture, the student
should be able to:
 Define bacteremia, fungemia, and sepsis
 List the main types of bacteremia and reasons
 List the main microorganisms causing bacteremia
 List the main laboratory method for detection
 List the important factors influencing the laboratory
test result
Bacteremia
• Presence of viable bacteria in the blood
• May be transient
• Self-limited without clinical consequences
But:
• Frequently reflects the presence of serious infections
• Life-threatening in immunocompromised
• Often associated with hospitalization and
instrumentation
Pseudobacteremia
• As a result of contamination of blood samples during
phlebotomy
• False positive results of blood culture
• Contamination is due to skin commensals: coagulasenegative staphylococci(CoNS) or other skin flora
But:
• Depending on the clinical situation these skin flora
may not represent pseudobacteremia
Occult(unsuspected)bacteremia
 No physical sign s or symptoms of severe infection
 Frequently in children younger than 2 years
 Due to Streptococcus pneumoniae
 Diagnosis may be overlooked
 If treatment delayed, catastrophic sequences
Sepsis
 In the past septisemia :bacteremia+bacterial invasion
and toxin production
Now terms are used to explain systemic response to
infection according to the severity:
 Systemic inflammatory response syndrome(SIRS)
 Septic shock
 Multiple organ dysfunction syndrome (MODS)
%70 septic patients
 Blood culture negative
Clasification of bacteremia
 Site of origin:
 Primary bacteremia: Arises from endovascular source
such as infected cardiac valve or infected intraveneous
catheter
 Secondary bacteremia: Arises from infected
extravasular source such as lung in patient with
pneumonia
 Bacteremia of unknown origin
Clasification of microbiology
 Gram-positive
 Gram-negative
 polymicrobial
CoNS bacteremia
 In hospitalized patient
 Indwelling vascular device
Polymicrobial bacteremia
 Enterococci and gram-negative microorganisms:
invasion from bowel perforation
Clasification of place of acquisition
 Community acquired
 Nosocomial : resistant strains
Clasification of duration
 Transient: dental, colonoscopic procedures
 Intermittant: meningecoccemia
 Continuous: infective endocarditis
Bacteremic patients
 Incidence of septic shock %10-30
 Mortality of septic shock:%40-50
Risk for bacteremia
 Decreased immune competency of selected patients
 Increased use of invasive procedures
 Age of the patient
 Administration of drug therapy
Microbiology
 Over the last 25 years patterns of organisms has
shifted:
 1960s-1970s: gram-negatives
 E.coli,P. Aeruginosa
 1980s-1990s:gram-positives: S. aureus, CoNS,
enterococcus
 More recently:Fungi(Candida)
 Fungemia: antifungal susceptibility test
Microbiology
 Methicillin-resistant S. aureus(MRSA)
 Vancomycin-resistant enterococci(VRE)
 Extended-spektrum Beta-lactamases (ESBL)
producing gram-negatives
 Haemophilus influenzae b (Hib)decreased by %95 by
conjugate Hib vaccine
Clinical syndomes associated with
bacteremia
• Catheter-related bloodstream infection
• Urinary tract infection
• Pneumonia
• Intraabdominal infection
• Skin infection
• Infective endocarditis
• Musculoskeletal infection
• Central nervous system infection
Laboratory diagnosis
Hemoculture(Venous blood ! : in sterile conditions))
 Density of bacteremia in adults versus neonates:
 10-15 bacteria/ml is detected by the blood culture
 Newborns have higher numbers of microorganisms
Laboratory diagnosis
Hemoculture(Venous blood ! : in sterile conditions))
 Density of bacteremia in adults versus neonates:
 10-15 bacteria/ml is detected by the blood culture
 Newborns have higher numbers of microorganisms
 Rapid molecular techniques:
 NAT(nucleic acid amplification techniques)
Laboratory diagnosis
Hemoculture (volume!)
 Density of bacteremia in adults versus neonates:
 Age
Amount
 ≤9 yıl
1 ml per year
 ≥10 yıl
20ml
Laboratory diagnosis
Hemoculture
Frequency of collection(!)
Three sets
One set: 1 aerobic one anaerobic
Just before fever rises(!)
Laboratory diagnosis
1.set:%80
2.set:%90
3.set:%99
-In the first 1-2 hours from three different veins 3
sets
-In subacute bacterial endocarditis: in the first
24 hours three sets 1 hour in between sampling
-Bacteremia of unknown origin: in 48 hours 4-6
times 10ml
Laboratory diagnosis
Brucellosis
During the initial presentation and at the anticipated
temperature spike
Blood culture methods
 Blood culture systems
 7 days of incubation
 Bacterial endocarditis and fungemia: 2weeks
 Brucellosis:21-28 days subcultured weekly
 Anaerobic subculture is performed after 2 days
 Any presumptive positive finding should be reported
to the physician by phone(panic values in laboratory).
Source of contamination
 %2 -3
 Staphylococcus epidermidis
 Micrococcus
 Diphtheroids
 Propionibacterium acnes
 Any organism cultured from 2-3 blood cultures should
not be overlooked as contaminant
Source of contamination
 Microbiologists can not make this determination(true
pathogen or contaminant) in the laboratory: Physician
input and patient history is needed.
Prevention:
 Hemoculture : education of nurses for sampling !
HEMOCULTURE (BLOOD
CULTURE)
Upon opening the bottle if it’s contaminated
Disinfect the rubber cap with alcohol swab. Let it
dry at least 30 seconds.
the puncture site antisepsis