Accuracy of delayed cultures of plugged telescoping catheter samples for diagnosing bacterial pneumonia

It is not always feasible to culture immediately bacteriologic samples of protected pulmonary specimens on a 24-hr basis before starting antibiotic treatment. We have evaluated the effect of delaying the culture of immediate plugged telescoping catheter (PTC) samples performed before starting antibiotherapy.

Prospective paired comparisons study.

Intensive care unit in a university hospital.

Ninety-nine PTCs were performed on 68 intensive care unit patients suspected of nosocomial or community- acquired bacterial pneumonia.

PTC samples were divided into two aliquots: one for immediate (H0) analysis and one for storage at 4 degrees C (H24) for 24 hrs before being cultured.

The results from these delayed cultures (H24) were compared with those from immediate ones (H0). All negative H0 samples (n = 59) were also negative at H24. Forty PTCs yielded one or more microorganisms, with a total of 69 microorganisms in one or both samples. H0 and H24 cultures were concordant in 119 of 128 (97.9%) cases (kappa coefficient value 0.79) with a threshold of 103 colony-forming units (cfu)/mL. Agreement between paired cultures was very good. The bias calculated as the mean difference between paired culture results was 0.128 +/- 1.024 (Deltalog). Concordance using the 103 cfu/mL threshold (102/107 cases, kappa coefficient value 0.82) and agreement were enhanced (0.067 +/- 0.645) when possible contaminants were excluded (n = 21).

Storing PTC specimens for 24 hrs at 4 degrees C is an acceptable alternative when culturing cannot be performed immediately. This allows starting antibiotic treatment without any delay.