Table 2.
Change in MDR rates in selected species of Gram-negative rods applying CLSI 2009 and EUCAST 2011 AST guidelines in two adjacent 17-month periods
| Species | Total isolates |
MDR isolatesa |
|||||
|---|---|---|---|---|---|---|---|
| CLSI 2009 period (n) | EUCAST 2011 period (n) | CLSI 2009 period (n, %) | EUCAST 2011 period (n, %) | Difference EUCAST/CLSI (%) | Cases due to EUCAST 2011 increased CBP (n, %)b | Difference without EUCAST increased CBP (%) | |
| E. coli | 3,303 | 3,295 | 43 (1.3) | 58 (1.8) | 0.5 | 12 (0.4, 21) | 0.1 |
| K. pneumoniae | 767 | 830 | 25 (3.3) | 23 (2.8) | –0.5 | 5 (2.2, 22) | –2.7 |
| E. cloacae | 420 | 448 | 6 (1.4) | 9 (2.0) | 0.6 | 5 (1.1, 56) | –0.5 |
| Total | 4,490 | 4,573 | 74 (1.6) | 90 (2.0) | 0.3 | 22 (0.5, 24) | –0.2 |
| P. aeruginosa | 783 | 977 | 57 (7.3) | 59 (6.0) | –1.3 | 7 (0.7, 12) | –2.0 |
| A. baumannii group | 84 | 137 | 13 (15.5) | 16 (11.7) | –3.8 | 0 (0, 0) | –3.8 |
| Total | 901 | 1,114 | 87 (9.7) | 75 (6.7) | –2.9 | 7 (0.6, 9) | –3.5 |
n, Number of isolates. Where applicable, the percentage(s) is indicated in parentheses.
Not including the piperacillin-tazobactam DCC and the extended-spectrum cephalosporin DCC since EUCAST 2011 uses different disk contents than CLSI 2009 for piperacillin-tazobactam and ceftazidime. The increase in MDR rate may therefore be underestimated, in particular for P. aeruginosa, since ceftazidime and cefepime alone define the extended-spectrum cephalosporin DCC, and therefore ceftazidime has a higher impact on MDR reporting rates compared to the Enterobacteriaceae. The first number in parentheses gives the absolute increase in the percentage of the total number of isolates in the EUCAST period; the second number gives the relative increase in the percentage of all MDR classified isolates in the EUCAST period.