Background and Goal of Study: Ventilator associated pneumonia (VAP) is the most common pneumonia in the surgical intensive care units (SICU). Studies in patients suggest that oral care can reduce the incidence of VAP in the SICU up to 90 %. Modern pharmacology confirms numerous biological effects of Neem, including its antibacterial effect. The study was aimed to determine the effect of methanol extract of Neem leaves on the most common oral bacterial pathogens which cause VAP and therefore the rationale of its use for oral care at SICU patients on mechanical ventilation and the prevention of VAP. 

Materials and methods: The agar dilution method was used and the methanol extract of Neem leaves (FNWL, Natural Sourcing, Oxford, CT, USA) in the concentrations of 0,25%, 0,50%, 1%, 2%, 5% and 10% was added to Müller-Hinton agar before its solidification. The dry matter in the extract was 4,31±0,19 g/100mL. The effect of extract on bacterial growth was studied on the suspension of clinically isolated bacteria: Staphylococcus aureus, MRSA (SCCmec I-V), Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa and Stenotrophomonas maltophilia (quantity 10 µL, density 105 and 108 CFU/mL), after the incubation of 24 h in the aerobic conditions at 37 oC. The results were read off as the smallest dilution concentrations of the extract which have had inhibitory effect on bacterial growth with microdilution method with automatic record. All experiments were done in triplicate, and as the control served the plates with 96 % methanol. 

Results and discussion: Methanol leaf extract of the Azadirachta indica (Neem) inhibited growth of the Staphylococcus aureus and MRSA at concentrations of 10 % and 5 %, respectively, while there was no bacteriostatic effect on the other bacteria in this experiment. This difference could be explained by the distinction in the characteristic lipopolysaharide wall layer of Gram negative bacteria so the Neem extract could take the effect through the periplasmatic space. Considering its effect on MRSA, Neem could be a promising source of a new antiMRSA drug and further research is required. 

Conclusion: Methanol extract of the plant Azadirachta indica (Neem) has no effect on the majority of the most common oral bacterial causes of VAP, except for Staphylococcus aureus and MRSA and therefore is not suitable for oral care of SICU patients on mechanical ventilation and thus the prevention of VAP.

The effect of the methanol leaf extract of the plant Azadirachta indica (Neem) on the most common bacterial causes of ventilator associated pneumonia