'Junk' blood tests may offer life-saving information

Contaminated blood tests that are usually tossed into the bin can be used by clinicians to provide more targeted antibiotics to the patients, scientists say.
Some 30 per cent of all positive hospital blood culture samples are discarded every day because they're "contaminated" - they reflect the presence of skin germs instead of specific disease-causing bacteria, researchers said.
Rather than toss these compromised samples into the trash, clinicians may be able to use the resistance profiles of skin bacteria identified by these tests to treat patients with antibiotics appropriate to their ailment, Tel Aviv University researchers say.
Dr Gidi Stein and Dr Danny Alon of TAU's Sackler Faculty of Medicine and the Department of Internal Medicine B at Beilinson Hospital, Rabin Medical Center, and Professor Lilach Hadany and Uri Obolski of the Department of Molecular Biology and Ecology of Plants at TAU's Faculty of Life Sciences conducted a retrospective study on more than 2,500 patients.

Their test results demonstrate the unique diagnostic value of "erroneous" cultures.
The more resistant the skin germs, the higher the risk of the infecting bacteria to be resistant, the researchers found.

"These results can certainly be used for on-site clinical decisions. Once a contaminated sample has been found to be highly resistant, it is likely that the blood-borne pathogens will have a similar resistance pattern," said Hadany.
"Thus antibiotic treatment may be better targeted for the actual pathogens," said Hadany.
In the study, the researchers processed the demographic information, hospital records, blood culture results, and date of death of all patients at the Rabin Medical Center with positive blood cultures from 2009-12.

They found that out of 2,518 patients, 1,664 blood cultures drawn from 1,124 patients reflected the presence of a common skin contaminant, coagulase-negative staphylococci (CoNS).
High overall CoNS resistance predicted high overall resistance of the bacteria causing disease or infection. Highly resistant CoNS isolates were found to be associated with higher short-term mortality.
"Because we have found a direct correlation between resistance profiles of CoNS contaminants and those of the actual infecting bacteria isolated from the same patient, the results of these 'junk' samples can be used to predict patient mortality and correct empirical antibiotic therapy," said Stein.
The study was published in the Journal of Antimicrobial Chemotherapy.