Table 2. Comparison of NaCl Minimal Inhibitory Concentration (MIC), Minimal Bactericidal Concentration (MBC) and Killing quotient (KQ) distributions for subgroups of P. aeruginosa CF isolates according to mucoid characteristic, antimicrobial susceptibility pattern, ability to form biofilm and patient under HTS treatment.
| NaCl MIC values (in %) | ||||||||||||||||||
| Agar dilution method | Broth dilution method | NaCl MBC values (in %) | Killing quotient (KQ)a | |||||||||||||||
| Population | Subgroup | Isolate type (n) | MIC50 | MIC90 | Range | P value d | MIC50 | MIC90 | Range | P value d | MBC50 | MBC90 | Range | P valued | KQ50 | KQ90 | Range | P value d |
| Total CF isolates | Mucoid characteristic | Mucoid (25) | 3 | 4 | 2–4 | <0.0001 | 3 | 5 | 0.9–5 | <0.0001 | 7 | 9 | 6–>10 | 0.01 | 2.3 | 3.5 | 1.4–7.8 | 0.0002 |
| Non-mucoid (60) | 5 | 5 | 2–6 | 5 | 6 | 2–6 | 8 | 10 | 4–>10 | 1.6 | 2.3 | 1.2–4 | ||||||
| Antimicrobial susceptibility pattern | Multidrug resistance (22) | 3 | 4 | 2–5 | <0.0001 | 3 | 5 | 2–5 | 0.0005 | 8 | >10 | 7–>10 | 0.3 | 2.3 | 3.5 | 1.4–4 | 0.002 | |
| Non-multidrug resistance (63) | 4 | 5 | 2–6 | 5 | 6 | 0.9–6 | 8 | 9 | 4–>10 | 1.8 | 2.3 | 1.2–7.8 | ||||||
| Ability to form biofilm | No (9 of which 3 mucoid) | 3 | 5 | 2–5 | <0.0001 Rs = 0.44 | 3 | 5 | 2–5 | <0.0001 Rs = 0.48 | 7 | 9 | 4–9 | 0.14 | 2.3 | 4 | 1.4–4 | 0.0009 Rs = –0.37 | |
| Weak (42 of which 16 mucoid) | 4 | 5 | 2–5 | 4 | 5 | 0.9–6 | 8 | 10 | 5–>10 | 1.8 | 3.5 | 1.2–7.8 | ||||||
| Moderate (18 of which 3 mucoid) | 5 | 5 | 2–5 | 5 | 6 | 2–6 | 8 | >10 | 7–>10 | 1.8 | 2.3 | 1.2–3.5 | ||||||
| Strong (16 of which 3 mucoid) | 5 | 6 | 3–6 | 5 | 6 | 3–6 | 8 | 9 | 6–10 | 1.5 | 2 | 1.2–2.7 | ||||||
| Patient under HTS treatment | Yes (5) b | 2 | 3 | 2–3 | ND | 3 | 3 | 2–3 | ND | >10 | >10 | 8–>10 | ND | ND | ND | ND | ND | |
| No (80) | 4 | 5 | 2–6 | 5 | 6 | 0.9–6 | 8 | 9 | 4–>10 | 1.8 | 2.7 | 1.2–7.8 | ||||||
| One isolate per type, per patient c | Mucoid characteristic | Mucoid (18) | 3 | 4 | 2–4 | <0.0001 | 3 | 5 | 2–5 | 0.0003 | 7 | 9 | 7–>10 | 0.07 | 2.3 | 3.5 | 1.4–4.5 | 0.0008 |
| Non-mucoid (30) | 5 | 5 | 2–6 | 5 | 6 | 2–6 | 8 | 9 | 5–>10 | 1.5 | 2.3 | 1.2–3.3 | ||||||
| Antimicrobial susceptibility pattern | Multidrug resistance (11) | 3 | 4 | 2–5 | 0.002 | 3 | 5 | 2–5 | 0.005 | 8 | 10 | 7–>10 | 0.6 | 2 | 3.5 | 1.6–3.5 | 0.001 | |
| Non-multidrugresistance (29) | 5 | 5 | 2–6 | 5 | 6 | 0.9–6 | 8 | 9 | 5–>10 | 1.5 | 2.3 | 1.2–7.8 | ||||||
| Ability to form biofilm | No (7 of which 1 mucoid) | 3 | 5 | 2–5 | <0.0001 Rs = 0.5 | 3 | 5 | 2–5 | 0.0004 Rs = 0.46 | 7 | 9 | 4–9 | 0.12 | 2.3 | 4 | 1.4–4 | 0.056 | |
| Weak (24 of which 8 mucoid) | 4 | 5 | 2–5 | 4 | 6 | 2–6 | 8 | 10 | 5–>10 | 1.6 | 2·5 | 1.3–3.5 | ||||||
| Moderate (15 of which 3 mucoid) | 5 | 5 | 2–5 | 5 | 6 | 2–6 | 8 | >10 | 7–>10 | 1.8 | 2·3 | 1.3–3.5 | ||||||
| Strong (11 of which 2 mucoid) | 5 | 6 | 4–6 | 5 | 6 | 4–6 | 9 | 9 | 7–10 | 1.5 | 2 | 1.3–2 | ||||||
| Patient under HTS treatment | Yes (1) | ND | ND | 2 | ND | ND | ND | 3 | ND | ND | ND | >10 | ND | ND | ND | ND | ND | |
| No (33) | 5 | 5 | 2–6 | 5 | 6 | 2–6 | 8 | 9 | 5– >10 | 1.6 | 2.5 | 1.2–3.5 | ||||||
MIC50 and MIC90 values were defined as the lowest concentration of NaCl at which 50% and 90% of the isolates were inhibited, respectively.
Only isolates exhibiting MBC values within tested range were considered.
5 isolates recovered in one patient.
isolates were randomly selected.
Comparison of MIC, MBC and KQ distribution between subgroups was performed with Mann-Whitney’s test, with the exception of the evaluation depending on biofilm producer groups, assessed by the Kruskal-Wallis’ test, and Spearman correlation coefficient (Rs) when Kruskal-Wallis’ test was positive. A P value ≤0.05 was considered to reflect significance and was indicated in bold type.
ND, not determined either because only one isolate or one patient was included in the sub-population, or because one isolate exhibiting a MBC value within the tested range.