Effect of Meconium Components on Haemophilus influenzae Growth by Surfactant

Kim, Min Hee; Chung, Sang In

Abstract

PURPOSE
Meconium is a complex mixture with a potential variable composition, it is difficulty to determine which components of meconium are responsible for the surfactant inhibition. We previous reported that Surfactant-TA and Exosurf almost completely inhibited the growth of Haemophilus influenzae at the concentration of 100% without apparent difference in the efficiency. In this study, We have determined the effect of Surfactant-TA on H. influenzae growth by meconium and futher investigated if this effect is caused by methanol or chloroform soluble meconium component.
METHODS
Approximately 20gm of meconium was collected from 5 healthy full term newborn infants. That was suspended in distilled water at a concentration of 25mg/ml and filtered by Whatmann filter paper No.3. The filtrate was pooled, lyophilized and stored at-15degrees C. Filtered meconium was extracted with chloroform-methanol (2:1,v/v). Exponential growing H. Influenzae (2.7x 107cells in 0.1ml of PBS) were mixed with 0.2ml of Surfactant-TA (30mg/ml) at serial dilutions ranging from 0.1% to 100%. Mixed solution of bacteria, Surfactant-TA, and meconium (0.1ml) or it's subfractions were incubated at 37degrees C for 90 min. After incubation, the mixtures was serially diluted with PBS. Each diluted mixture were cultivated on chocolate agar plate. Volumes of inoculation were 0.1ml of mixture. Number of viable bacteria were estimated by colony counting after 18hours culture. For transmission electronmicroscopic finding, mixture of bacteria 100% surfactant-TA were proceeded to prepare.
RESULTS
1) Surfactant-TA almost completely inhibited the growth of H. influenzae at the concentration of 100%. 2) The meconium, methanol and chloroform meconium all did not affected the H. influenzae growth inhibition effect of Surfactant-TA. 3) Surfactant destroyed H. influenzae with disruption of cell membranes and leakage of intracellular organelles.
CONCLUSIONS
The meconium and it's subfraction all did not affected the H. influenzae growth inhibition effect of Surfactant-TA. So, We speculated that using Surfactant-TA in meconium aspiration pneumonia will be beneficial to reducing severity of respiratory symptom. But more extensive controlled in vivo test need before surfactant therapy can be considered as a treatment modality for like this condition.