Introduction. We recently demonstrated the potential of engineered live bacteria against Pseudomonas aeruginosa ex vivo biofilms grown in endotracheal tubes (ETT) from patients with ventilator-associated pneumonia (VAP)^1,2 (Fig.1A).

Aim. To test the in vivo efficacy of the genetically modified Mycoplasma pneumoniae strain (CV8_HA_P1) against P. aeruginosa ETT-biofilms in mechanically ventilated pigs with VAP.

Methods. Fourteen pigs previously infected with P. aeruginosa VAP³ were treated with PBS (Control, n=3), CV8 (non-pathogenic strain, n=6), or CV8_HA_P1 (non-pathogenic strain with antibiofilm and antimicrobial activity, n=5). At extubation, ETTs were analyzed for P. aeruginosa load, biofilm thickness (?m) and microbiome diversity.

Results. After 39.0 [24.0-39.0] hours of mechanical ventilation, no significant differences were found in P. aeruginosa load between Control, CV8 and CV8_HA_P1 groups (p=0.32) (Fig.1B). However, a significant reduction in the ETT biofilm thickness was detected in the CV8_HA_P1 group compared to others (p<0.001) (Fig.1C, 1D). No significant microbiome diversity disbalances among groups were observed (p_Observed=0.38, p_Shannon=0.78, p_Simpson=0.87).

Conclusions. Although genetically modified M. pneumoniae CV8_HA_P1 showed a reduction in biofilm thickness, further investigation is needed to determine its effectiveness in reducing the P. aeruginosa load in ETT biofilms.