body sites 5.6 bloodstream

what is septicemia

bacteria is actively living in and multiplying in the blood stream

life threatening

bug has overcome the body’s defenses

what is the marker for septicemia

serum lactate

what is bacteremia

bacteria is in the blood but its not constant; transient or intermittent

transient bacteremia

usually insignificant

can occur after blood is exposed to a wound, like a tooth extraction

body defenses will clear the bacteria in 30 mins in normal, immunosufficient people

intermittent bacteremia

going into the blood from another site, like an abscess, catheter, meningitis, typhoid fever, brucellosis, SBE, prosthetic heart valves

may ir may not be cleared, but usually require and antibiotic

symptoms of bacteremia

fever of unknown origin

chills

shock

tachycardia

malaise

what is subacute bacterial endocarditis

an infection of the heart valves by a non-pathogenic or low virulence bacteria

characteristics of SBE

insidious onset

102 F fever

progressive anemia, ACD

heart murmur

valvular disease

fatal if untreated

endotoxins

in the cell wall of a gram negative bacteria that gets released when it lyses

decreases granulocytes, causes fever, activates complement and clotting system and can lead to DIC

exotoxins

in some gram pos

can also lead to DIC

timing of blood collection

need 2-4 different cultures at least an hour apart before antibiotics are given

skin flora that might be seen in blood culture

diphtheroids

alpha strep

propionibacterium

routine blood culture media

BHI or TS broth base

additives in a blood culture

CO2 in the headspace

sodium polyanethol sulfonate as an anticoagulant, counteracts bactericidal effects, but inhibits GC and meningococcus

add gelatin for GC and meningococcus

sucrose to increase growth and given osmotic support

resin neutralizes antibiotics

how long are blood cultures kept

examine daily for 1 week

if brucella, keep 3-4 weeks

physical evidence of bacterial growth

septi-chek → colonies on media on paddles

routine bottles: rbc hemolysis, gas bubbles, turbidity, colonies on RBC layer

what do you do when a blood culture bottle is positive

gram stain or acridine orange

ID

AST

blind subcultures

6-12 hours after inoculation of the bottle its subbed to CHOC

increases recovery even if no growth is seen yet

incubate in CO2 for 48 hours and check

BD Speti-Chek

biphasic system

bottle has broth and attached to something with a solid media

faster detection time

Wampole isolator

lysis centrifuge

red blood cells lysed, then centrifuged, and sediment is plated

for intracellular bacteria and fungi

how long do you keep a blood culture for an automated system?

5 days

brucella, HACEK, NV strep, and FUO keep for 21 days

BACTEC

old models detect radioactive carbon

new models detect CO2 with infrared spectroscopy or fluorescence of decreased H ions, decreased pH

BacT/Alert

bottle has a CO2 sensor to detect growth with pH hanges

membrane color change measured with reflectometers

VersaTREK

only blood culture system to monitor the pressure changes in a bottle’s head space

can also be used for other sterile body fluids

what does a true positive culture look like

same organism from several bottles

clinical picture suggests a positive culture is likely

immunosuppressed or patient with prosthesis with commensal flora is possible

growth of typical isolates like group a strep, strep pneumo, enterics, GN anaerobes

what does a false positive blood culture look like

growth of skin flora in only one bottle like propi(cutie), bacillus, diphtheroids, coag negative staph

several organisms isolated in only one bottle

different isolate from initial infecction site than from blood culture

highly resistant organisms in immunosuppressed patients

serratia marcescens

enterobacter

pseudomonas aeruginosa

corynebacterium jeikeium

isolates from SBE

viridans strepto: s. sanguis, intermedius, mutans

enterococci

group d strep

coag neg staph

haemophilus parainfluenzae, a. aphrophilus

sources of s. aureus in acute sepsis

abscesses, wounds, pneumonia

pneumococcal sepsis

occurs in 25% of pneumonia

important to subculture early as the organism has an autolytic enzyme and might not grow if you wait too long

haemophilus septicemia

from h. influenzae meningitis or h. parainfluenzae SBE

grow sparsely in a blood culture and may not look positive, may need to do a blind subculture

neisseria sepsis

either meningitis or gonorrhea

can lead to DIC especially meningococcus

listeria monocytogenes septicemia

in immunosuppressed, alcoholics, newborns, pregnant women, and elderly

GNR septicemia

high mortality and can lead to DIC

most common anaerobe septicemia

bacteroides fragilis

bacteroides fragilis septicemia

a bowel NF and common wound isolate

brucella septicemia

uncommon isolate, needs 4 week incubation time and needs venting

yersinia pestis and francisella tularensis

need special media and longer incubation

severe biohazards

if suspected, inform doctor immediately and send blood cultures to public health lab

mycobacteria

need special media, liquid, with Tween-80

seperate blood culture instrument

fungi

need venting and agitation

better isolation with biphasic or lysis centrifugation systems

nutritionally variant streptococci

granulicatella and abiotrophia need vitamin B6 for growth and satellite around Staph colonies or B6 disc

contamination rates of blood culture bottles

should be <3.0%

PCT

procalcitonin

new analyte for detection of septicemia