Table 1.
Antibiotic susceptibility profiles and characteristics of the K. pneumoniae strains isolated throughout the patient’s hospital course
| Isolate #, source and hospital day of isolation |
|||||||
|---|---|---|---|---|---|---|---|
| #1 blood (day 1) | #2 sputum (day 3); #5 renal abscess (day 32); #6 renal abscess (day 32) | #3 sputum (day 8); #4 sputum (day 24); #10 blood (day 56) | #7 renal abscess (day 39) | #8 and #9 stool surveillance (day 45); #11 and #12 environmental isolates | E. coli transformant with ColKP3 plasmid bearing OXA-181 | electrocompetent NEB 5-alpha E. coli with no plasmid | |
| String test | positive | positive | negative | positive | negative | negative | negative |
| MLST | ST23 | ST23 | ST147 | ST23 | ST147 | NA | NA |
| mCIM | negative | negative | positive | positive | positive | positive | negative |
| AST results - MIC (mg/L) and breakpoint interpretation or epidemiological cut-off value | |||||||
| ampicillin/sulbactam | 8/4 (S) | 8/4 (S) | >16/8 (R) | >16/8 (R) | >16/8 (R) | >16/8 (R) | 4/2 (S) |
| piperacillin/tazobactam | 4/4 (S) | 4/4 (S) | >64/4 (R) | >64/4 (R) | >64/4 (R) | 32/4 (I) | ≤2/4 (S) |
| cefazolin | ≤1 (S) | 4 (I) | >16 (R) | >16 (R) | >16 (R) | >16 (R) | 2 (S) |
| cefoxitin | ≤4 (S) | 16 (I) | >16 (R) | >16 (R) | >16 (R) | ≤4 (S) | ≤4 (S) |
| ceftriaxone | ≤1 (S) | ≤1 (S) | >32 (R) | 2 (I) | >32 (R) | ≤1 (S) | ≤1 (S) |
| ceftazidime | ≤0.5 (S) | ≤0.5 (S) | >16 (R) | >16 (R) | >16 (R) | ≤0.5 (S) | ≤0.5 (S) |
| cefepime | ≤1 (S) | ≤1 (S) | >16 (R) | ≤1 (S) | >16 (R) | ≤1 (S) | ≤1 (S) |
| aztreonam | ≤2 (S) | ≤2 (S) | >16 (R) | ≤2 (S) | >16 (R) | ≤2 (S) | ≤2 (S) |
| meropenem | ≤0.5 (S) | ≤0.5 (S) | >8 (R) | 4 (R) | >8 (R) | ≤0.5 (S) | ≤0.5 (S) |
| ertapenem | ≤0.25 (S) | ≤0.25 (S) | >1 (R) | >1 (R) | >1 (R) | 1 (I) | ≤0.25 (S) |
| imipenem | 0.25 (S) | 0.25 (S) | >32 (R) | ND | >32 (R) | 0.25 (S) | 0.25 (S) |
| trimethoprim/sulfamethoxazole | ≤0.5/9.5 (S) | 1/19 (S) | >2/38 (R) | >2/38 (R) | >2/38 (R) | ≤0.5/9.5 (S) | ≤0.5/9.5 (S) |
| tetracycline | ≤2 (S) | 8 (I) | >8 (R) | 8 (I) | >8 (R) | ≤2 (S) | ≤2 (S) |
| gentamicin | ≤2 (S) | ≤2 (S) | >8 (R) | ≤2 (S) | >8 (R) | ≤2 (S) | ≤2 (S) |
| tobramycin | ≤2 (S) | ≤2 (S) | >8 (R) | ≤2 (S) | >8 (R) | ≤2 (S) | ≤2 (S) |
| amikacin | ≤8 (S) | ≤8 (S) | >128 (R) | ≤8 (S) | >128 (R) | ≤8 (S) | ≤8 (S) |
| ciprofloxacin | ≤0.5 (S) | 1 (S) | >2 (R) | 2 (I) | >2 (R) | ≤0.5 (S) | ≤0.5 (S) |
| tigecycline | 0.5 (S) | 2 (S) | 2 (S) | 2 (S) | 2 (S) | 0.125 (S) | 0.125 (S) |
| colistin | 0.5 (WT) | 0.5 (WT) | 0.25 (WT) | 0.25 (WT) | >16 (NWT) | 0.06 (WT) | 0.06 (WT) |
| chloramphenicol | 8 (S) | >256 (R) | >256 (R) | >256 (R) | >256 (R) | 16 (I) | 8 (S) |
| ceftazidime/avibactam | 0.125 (S) | 0.125 (S) | 2 (S) | 0.5 (S) | 1 (S) | 0.125 (S) | 0.125 (S) |
S, susceptible; I, intermediate; R, resistant; NWT, non-WT; NA, not applicable; ND, not determined.
Isolates 3, 4 and 8–12 were identified as XDR due to resistance to all antimicrobial categories tested with the exception of polymyxins (colistin; isolates 8, 9, 11 and 12 did acquire resistance and were defined as non-WT) and glycylcyclines (tigecycline). Ceftazidime/avibactam was not included in the definition in accordance with Magiorakos et al.8
Isolate 7 was identified as MDR as the isolate was resistant to at least one agent in nine categories (a minimum of three categories are required to meet the MDR definition).8 The AST profile at the time of obtaining the clinical culture was repeated due to the unusual profile (i.e. reduced susceptibility to certain cephalosporins but resistant to the carbapenems). The AST profile was confirmed upon repeat.