## 3 Results
### Pseudomonas aeruginosa ATCC 31461
#### 3.3.2 Combination of Agents  
\(N\)-acetylcysteine 25.0 mg/mL in combination with 25.0 mg/mL bromelin displayed the highest biofilm dissolution value (85%) amongst all combinations. The combinations of NAC 15 mg/mL + 25 mg/mL bromelin, 25.0 mg/mL NAC + 12.5 mg/mL Bromelain, and 50 mg/mL NAC + 25 mg/mL bromelin showed good biofilm dissolution rates of about 80% in a synergistic manner, as indicated by the CI values below 0.5 (Figure 3A and Table 2).  
Hence, in this particular strain of bacteria, the combination of bromelin with NAC performs very well at four different concentrations, as shown in Table 2 (with highlight).  
Comparison of Maximum Biofilm Dissolution (BD MAX) Values of the Two Different Agents on Different Strains of Pseudomonas aeruginosa  
Amongst the three strains of _Pseudomonas aeruginosa_, bromelin at 100 mg/mL was most active in the dissolution of biofilm in ATCC 31461, whilst being slightly less active in ATC 27853 (75% vs. 66%, respectively). Bromelain was least active in PA01 3981, with BE MAX value of 45% (Table 3).  
Figure 3: **(A)** Dissolution of biofilm formed by _Pseudomonas aeruginosa_ ATCC 31461 by bromelin and \(N\)-acetylcysteine. The graph shows that with the addition of 15, 25, and 50 mg/mL \(N\)-acetylcysteine (NAC) to bromelin, the biofilm dissolution (BD) values were above 80%, indicating good dissolution of biofilm. Bromelain alone showed a maximum biofilm dissolution (BD MAX) of 75% at 100 mg/mL. **(B)** Dissolution effect of \(N\)-acetylcysteine on biofilm secreted by _Pseudomonas aeruginosa_ ATCC 31461. The graph indicates that NAC below 25 mg/mL had a negative effect (enhancement) on biofilm growth, while at 50 and 100 mg/mL NAC showed about 40–57% BD MAX values, indicating that it had a dissolution effect on biofilm.  
NAC at 100 mg/mL resulted in negative dissolution (enhancement of biofilm formation) in ATCC 27853, whilst it had a very minor effect (3%) in PA01 3981. On the contrary, it was comparatively very active with 57% dissolution in ATCC 31461 (Table 3).  
The biofilms generated by all three strains of _Pseudomonas aeruginosa_ reacted very well to the dissolution treatment of a combination of bromelain and \(N\)-acetylcysteine (BromAc), with BD MAX values ranging from 79 to 97%, indicating good efficacy (Table 4).  
There was a slight individual variation between the biofilms generated by the strains, with PA01 3981 being slightly more receptive and with the highest BD MAX value range of 88-97% depending on the concentrations of the two agents used. A combination of 25 mg/mL NAC with 25 mg/mL bromelain produced the highest % of biofilm dissolution (BD MAX) in PA01 3981. The biofilms formed by the other two strains ATCC 27853 and ATCC 31461 appeared to be almost equally affected by the treatment at equivalent combinations, i.e., 15.0 mg/mL NAC + 25 mg/mL bromelain had BD MAX values of 87% vs. 81%. Similarly, with a combination of 50 mg/mL NAC with 12.5 mg/mL bromelain, the BD MAX values were 80.5% vs. 79%. Overall, the combination of bromelain and NAC (BromAc) gave dissolution values (BD MAX) of 80% and above in the three strains of _Pseudomonas aeruginosa_, indicating the efficacy of BromAc (Table 4).