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Volume 17, Number 6—June 2011

Dispatch

High Vancomycin MIC and Complicated Methicillin-Susceptible Staphylococcus aureus Bacteremia

Jose Maria AguadoComments to Author , Rafael San-Juan, Antonio Lalueza, Francisca Sanz, Joaquin Rodríguez-Otero, Carmen Gómez-Gonzalez, and Fernando Chaves
Author affiliations: Author affiliations: University Hospital 12 de Octubre, Madrid, Spain

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Table 1

Differential characteristics of patients with bacteremia caused by MSSA strains with a MIC to vancomycin >1.5 µg/mL compared with <1.5 µg/mL by Etest, Hospital 12 de Octubre, Madrid, Spain, January 2002–December 2004*

Characteristic MIC <1.5, n = 76 MIC >1.5, n = 23 p value
Mean age, y (SD) 63.55 (16.7) 62.9 (18.8) 0.87
M/F, % 69.7/30.3 56.5/43.5 0.36
Co-morbidity Charlson Index, mean (SD)
2.76 (2.7)
3.4 (3.7)
0.4
Previous valvular prosthesis 1 (1.3) 2 (8.7) 0.23
Other previous endovascular prosthesis 4 (5.3) 1 (4.3) 0.7
Previous osteoarticular prosthesis 3 (3.9) 0 0.79
Previous renal failure requiring hemodialysis
7 (9.2)
4 (17.4)
0.47
Type of IV catheter as the source of bacteremia
Peripheral line 34 (44.7) 9 (39.1) 0.71
Transitory central catheter 34 (44.7) 10 (43.5) 0.82
Permanent central catheter
8 (10.6)
4 (17.4)
0.76
Vancomycin MIC of the first MSSA isolate, median (range)
1.2 (0.5–1.4)
1.5 (1.5–1.7)
<0.0001
Initial treatment with glycopeptides 46 (60.5) 18 (78.3) 0.19
Initial treatment with antistaphylococcal β-lactams† 20 (26.3) 5 (21.7) 0.87
Initial treatment with non–β-lactam anti-staphylococcal agents‡ 7 (9.2) 0 0.29
Delay in initiation of active antibiotic treatment, d,§ mean (SD) 0.85 (1.06) 1.3 (1.6) 0.14
Duration of antibiotic treatment, d, mean (SD)
13.4 (8.24)
18.6 (12)
0.07
Prompt IV catheter removal¶ 62 (81.6) 17 (73.9) 0.45
Conservative IV catheter management#
4 (5.3)
2 (8.7)
0.32
Development of severe sepsis/septic shock
11 (14.5)
5 (21.7)
0.69
Complicated bacteremia 10 (13.2) 18 (78.3) <0.0001
Septic thrombophlebitis 5 (6.6) 8 (34.9) 0.002
Endocarditis 3 (3.9) 4 (17.3) 0.08
Osteoarticular 2 (2.6) 2 (8.7) 0.48
Pulmonary emboli 0 2 (8.7) 0.08
Other
0
2 (8.7)
0.08
Crude 30-day death rate 8 (10.5) 6 (26.1) 0.13
Attributable death rate 3 (3.9) 4 (17.4) 0.083

*Values are no. (%) except as indicated. MSSA, methicillin-susceptible Staphylococcus aureus; IV, intravenous.
†Antistaphylococcal β-lactams refers to parenteral cloxacillin, cefazolin, amoxicillin-clavulanate, piperacillin-tazobactam, or imipenem/meropenem.
‡Including non–β-lactam antibiotics with in vitro activity against MSSA (mostly levofloxacin, moxifloxacin or, clindamycin).
§Delay since isolation of MSSA in blood cultures.
¶Removal of catheter in the first 48 hours since isolation of MSSA in blood cultures.
#Catheter kept at least 7 days since isolation of MSSA in blood cultures.

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