Analysis of the effects of storage temperature and contamination on aerobic bacterial culture results of bronchoalveolar lavage fluid

Abstract

Abstract Background Storage temperature of bronchoalveolar lavage fluid (BALF) impacts cytological evaluation. The effect of storage temperature before bacterial culture has not been evaluated. Objectives To assess whether BALF storage temperature alters aerobic bacterial culture results. Animals Eight healthy, male, intact, purpose‐bred Beagles. Methods Prospective, controlled investigation. Samples of BALF were collected sterilely. Half of each sample was reserved for controls, and half was inoculated with 104 colony forming units per milliliter (cfu/mL) Bordetella bronchiseptica and 102 cfu/mL Escherichia coli. Control and inoculated samples each were separated into 4 aliquots (1 plated immediately; 3 stored at 4, 24, or 37°C, respectively, for 24 hours before aerobic bacterial culture). Colony counts were compared across treatments for each organism. Results In inoculated samples, a statistical difference could not be detected in growth of E. coli or B. bronchiseptica between the baseline culture and BALF stored at 4°C for 24 hours before culture. However, for E. coli, growth in cfu/mL at both 24 and 37°C was higher compared to baseline (P < .05) and compared to 4°C (P < .05). For B. bronchiseptica cfu/mL, growth at 37°C was significantly different (P = .003) compared to both baseline and 4°C. Conclusions and Clinical Importance Samples of BALF may be stored at 4°C for 24 hours before culture without substantially altering culture results. Inappropriate storage or shipment temperature (room temperature or exposure to heat) can result in overgrowth of E. coli or B. bronchiseptica, which could alter clinical decisions.

Keywords

• aerobic
• Bordetella bronchiseptica
• contaminant
• Escherichia coli
• infection
• pneumonia