BLOOD STREAM INFECTIONS:Definitions and Significance.

Dr Abhijit Chaudhury

Classical Terms

Bacteremia: Presence of Bacteria in blood.

Transient: Manipulation/Surgery in infected/colonized area

Intermittent: Abdominal/Pelvic abscess

Continuous: Endocarditis/Intravascular infections/ First week of Typhoid , Brucellosis.

Septicaemia: Presence of microbes or their toxins in blood.

Recently Introduced Terms

BLOOD STREAM INFECTION: Presence and active multiplication of organisms in blood.

Primary: Point of entry or focus of infection cannot be determined/ Originates from I/V catheters.

Secondary: Distant site (focus) of infection present.

Community acquired BSI: Those Detected within 48 hrs of admission

Nosocomial BSI: Signs and symptoms detected after 48 hrs of admission

SEPSIS SPECTRUMConsensus Committee of American Experts (1992)

Definitions:Systemic Inflammatory Response Syndrome (SIRS)

:Systemic response to a wide range of stresses. Two or more of the following: Temperature : > 380 C or < 360 C Heart Rate > 90/min Tachypnea > 20 /min or Hyperventilation (PaCO2 <32 mm Hg, 4.3kPa) Leukocytes > 12,000 or < 4,000/mm3 or > 10% immature neutrophils

Sepsis Spectrum

Limitations of SIRS Definition

Sepsis Spectrum and Mortality

7-17%Sepsis

400,000

20-53%Severe Sepsis300,000

Septic Shock

53-63%Approximately 200,000 patients have septic shock annually

Balk, R.A. Crit Care Clin 2000;337:52

Incidence Mortality

Bacteremia in the Preantibiotic Era

Streptococcus pneumoniae Group A Streptococcus Staphylococcus aureus Salmonella spp Haemophilus influenzae Neisseria meningitidis

a. Nosocomial BSI

b. Community Acquired BSI

CHANGING TRENDS IN PATHOGEN PATTERN IN BSI.

PRIMARY BLOOD STREAM INFECTION In many cases the primary focus/ route of

entry remains unknown (Appx. 20%) Therapeutic/Diagnostic medical devices

coming in direct contact with blood- (Device Related Bacteremia ,Maki 1977).

Various types of venous catheters, arterial lines - Catheter Related BSI (CR-BSI).

Entry of organisms through: 1. Contamination of Infusate 2. Contamination of Catheter hub and lumen 3. Contamination of Skin at insertion site

CR-BSI, S.aureus Bacteremia

Jensen AG. Journal Hospital Infection 2002;52:29-36

Secondary BSI

Focus of Infection most commonly in LUNGS, URINARY TRACT, ABDOMEN, INFECTED SURGICAL SITE.

Gram negative pathogens more commonly involved.

5-12% cases may be due to fungi, particularly Candida.

Predisposing Conditions and Agents in BSI.

GRAM NEGATIVE PATHOGENS: Diabetes mellitus Lymphoproliferative diseases Liver cirrhosis Burns Invasive procedures or devices Neutropenia Indwelling urinary catheter

Predisposing Conditions--GRAM POSITIVE PATHOGENS: Intravascular Catheters Indwelling mechanical devices Burns Neutropenia Intravenous drug users FUNGI: Neutropenia Broad spectrum antimicrobial therapy

Neonatal BSI Commonly manifests as meningitis, almost

always preceded by bacteremia. Risk Factors: Prematurity, low birth weight,

premature rupture of membrane, prolonged labour.

Mortality: 30-40%, Permanent defects:30% of survivors.

Gram negative bacteria: E.coli, Klebsiella, Enterobacter etc.

Gram Positive: Group B Streptococcus (S.agalactiae), Listeria.

Conclusion Sepsis may be obvious or subtle early in its course. There is a high mortality and morbidity Clinical characteristics

Community-acquired vs. hospital acquired Presence or absence of an apparent primary focus. Role of intravascular catheters: Diagnosis of exclusion or

laboratory criteria Take appropriate cultures Treatment 1.Need to initiate empiric therapy 2.Choice of initial therapy depends on Knowledge of local

organisms / susceptibilities

Aggressive management is crucial in determining the patient’s survival.

THE END