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Volume 20, Number 5—May 2014

Letter

Linezolid-Resistant Staphylococcus epidermidis, Portugal, 2012

Mariana Barros, Raquel Branquinho, Filipa Grosso, Luísa Peixe, and Carla NovaisComments to Author 
Author affiliations: Faculdade de Farmácia da Universidade do Porto, Porto, Portugal

Main Article

Table

Epidemiologic features and antimicrobial drug resistance of linezolid -resistant Staphylococcus epidermidis isolates from a hospital, Portugal, 2012*

Characteristic Patient no.†
1 2 3 4 5
Epidemiologic features
Date of isolation 2012 May 8 2012 Aug 7 2012 Oct 23 2012 Nov 7 2012 Nov 11
Hospital ward Men’s surgery Unknown Medicine I Emergency unit‡ Emergency unit‡
Pathology Gastric neoplasia§¶ Unknown Multiple§ Acute lung edema Multiple
Clinical sample Catheter Blood Catheter Blood Blood
Patient sex/age, y M/75 Unknown F/87 M/78 M/87
Previous linezolid Yes Unknown Yes# Yes‡ Yes‡
PFGE type A A A A A
Sequence type 2**
Biofilm production (OD570nm)
Strong (2.33 ± 0.34)**††




Drug resistance
Linezolid (MIC, mg/L) R (32) R (32) R (32) R (32) R (32)
Vancomycin (MIC, mg/L) S (2) S (2) S (2) S (2) S (2)
Cefoxitin R R R R R
Gentamicin R R R R R
Tobramycin R R R R R
Ciprofloxacin R R R R R
Clindamycin R R R R R
Erythromycin S I S I S
Quinupristin–dalfopristin S S S S S
Chloramphenicol R R R R R
Tetracycline S S S S S
Cotrimoxazole
R
R
R
R
R
Molecular features
cfr gene
23S rRNA mutations
T2504A + + + + +
G2631T + + + + +
T2530A + + + + +
L3 ribosomal protein mutations
Leu94Val +**
Gly152Asp +**
Asp159Glu +**
Ala160Pro +**
L4 or L22 ribosomal protein mutations None

*PFGE, pulsed-field gel electrophoresis; OD, optical density; R, resistant; S, susceptible; I, Intermediate resistance; –, negative; +, positive. Blank cells indicate not tested.
†A sixth linezolid-resistant S. epidermidis isolate was detected in December 2012; however, access to this isolate was not possible during this study.
‡Patients 4 and 5 were hospitalized in Medicine II a month before linezolid-resistant S. epidermidis was isolated. Therapy with linezolid was started during this first hospitalization. For patient 4, duration of linezolid therapy was at least 12 d. For patient 5, duration of therapy is unknown.
§Long-stay hospitalization.
¶Followed up in oncology ward since 2011.
#Patient 3 received linezolid for 11 d before linezolid-resistant S. epidermidis was detected.
**Studied in S. epidermidis from patient 1 only, representative isolate of the PFGE type A.
††For the interpretation of the results, the cutoff optical density (ODc) was defined as 3 SDs above the mean OD of the negative control (culture medium). Strains were classified as nonadherent (OD<ODc), weakly adherent (ODc<OD<2×ODc), moderately adherent (2xODc<OD<4×ODc), or strongly adherent (4×ODc<OD).

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