Figure 8. Absence of the principal DsbA analogue (DsbA1) from P. aeruginosa clinical isolates expressing OXA enzymes sensitizes them to existing β-lactam antibiotics and dramatically increases the survival of infected G. mellonella larvae that undergo antibiotic treatment.

(A) Absence of DsbA1 sensitizes the P. aeruginosa PA43417 clinical isolate expressing OXA-198 to the first-line antibiotic piperacillin. (B) Absence of DsbA1 sensitizes the P. aeruginosa PAe191 clinical isolate expressing OXA-19 to aztreonam and results in reduction of the ceftazidime MIC value by over 220 µg/mL. For panels (A) and (B) the graphs show MIC values (μg/ml) from two biological experiments, each conducted as a single technical repeat; red dotted lines indicate the EUCAST clinical breakpoint for each antibiotic. (C) 100% of the G. mellonella larvae infected with P. aeruginosa PAe191 (blue curve) or infected with P. aeruginosa PAe191 and treated with 7.5 µg/mL ceftazidime (red curve) die 18 hr post infection, and only 20% of the larvae infected with P. aeruginosa PAe191 dsbA1 (light blue curve) survive 50 hr post infection. Treatment of larvae infected with P. aeruginosa PAe191 dsbA1 with 7.5 µg/mL ceftazidime (pink curve) results in 83% survival, 50 hr post infection. The graph shows Kaplan-Meier survival curves of infected G. mellonella larvae after different treatment applications; horizontal lines represent the percentage of larvae surviving after application of each treatment at the indicated time point (a total of 30 larvae were used for each curve). Statistical analysis of this data was performed using a Mantel-Cox test; n = 30; p =< 0.0001 (significance) (P. aeruginosa versus P. aeruginosa dsbA1), p > 0.9999 (non-significance) (P. aeruginosa vs P. aeruginosa treated with ceftazidime), p =< 0.0001 (significance) (P. aeruginosa treated with ceftazidime versus P. aeruginosa dsbA1), p =< 0.0001 (significance) (P. aeruginosa dsbA1 versus P. aeruginosa dsbA1 treated with ceftazidime).