Possible contaminant organisms:
(1) coagulase negative staphylococci
(2) aerobic and anaerobic diphtheroids
(3) Micrococcus species
(4) Bacillus species
(5) viridans group streptococcus
Questions:
(1) number of blood culture sets collected within a 48 hour period
(2) number of blood culture sets positive for the same organism
(3) organism isolated
where:
• The timing of blood cultures was based on the time of collection.
• The number of bottles in culture set was not utilized in the algorithm.
• The approach differs from the of Weinstein in that coagulase negative staphylococci are not handled differently.
The isolate was worked up based on an evaluation of the clinical and laboratory features performed by a pathology resident if:
(1) only 1 blood culture set was taken
(2) more than 1 blood culture set was taken within a 48 hour period, more than 1 blood culture set was positive for the same organism, and the isolate was a contaminant other than viridans streptococcus.
If more than 1 blood culture set was taken within a 48 hour period, more than 1 blood culture set was positive for the same organism, and the isolate was viridans streptococcus, then the identification and antibiotic susceptibility testing is done.
If more than 1 blood culture set was taken within a 48 hour period, and if these are not positive for the same organism (only 1 culture set is positive OR different isolates are seen) then:
(1) the isolate is considered a contaminant and
(2) the identification and antibiotic susceptibility testing is done only if requested by the patient's physician.
