Peripheral venous catheter-related bacteremia in a general hospital     

M. DELGADO-CAPEL, A. GABILLO, L. ELIAS, J. C. YÉBENES, G. SAUCA, J. A. CAPDEVILA                                                               

 
Introduction. Catheter sepsis is a constant and serious problem in our hospitals for the cost it generates, both in terms of morbidity and economics. It’s becoming more frequent also in peripherally inserted catheters. Our study aims to know the importance and characteristics of peripheral venous catheter bacteremia in a general hospital.
Material and methods. Prospective and comparative analysis of all episodes of central and peripheral venous catheter-related bacteraemia, in 2009.
Results. Twenty-eight episodes of catheter-related bacteraemia in a total of 25 patients. Sixteen episodes originated in central catheter (57.2%), 11 in peripheral (39.3%) and 1 in peripherally inserted central catheter (3.5%). Two cases of exitus directly related to the peripheral catheter infection. Etiology: 13 episodes of S. aureus (3 MRSA), including 8 in peripheral catheter (8/13, 61.5%), 12 episodes of plasma coagulase negative staphylococcus, including 2 in peripheral catheter (2/12, 16.6%).
Conclusions. Peripheral catheter-related bacteraemia is an emerging health problem with important clinical and prognostic connotations for patients. It is necessary continuous training on correct handling measures to prevent intravascular catheters infections including peripheral catheters in every hospital ward. 

 

Rev Esp Quimioter 2012:25(2):129-133 [pdf]

A combination of tigecycline, colistin, and meropenem against multidrug-resistant Acinetobacter baumannii bacteremia in a renal transplant recipient: pharmacodynamic and microbiological aspects  

F.J. CANDEL, N. CALVO, J. HEAD, A. SÁNCHEZ, M. MATESANZ, E. CULEBRAS, A. BARRIENTOS, J. PICAZO 

 

Acinetobacter baumannii are emerging as the causal agents of healthcare-associated infections. We describe a renal transplant recipient who developed bacteremia caused by multiresistant A. baumannii, which received a combination of tigecycline, colistin, and meropenem in continuous infusion. The clinical outcome was favorable. In this article we made a molecular study of this multiresistant strain. Our analysis reveals the presence of a bla-OXA-72 gene, a class D of oxacillinase belonging to bla-OXA-40-like group, which constitutes the most disseminated familiy of carbapenemases in Spain. Thus, we found different susceptibility patterns of A. baumannii when we used different Mueller-Hinton agars with different manganese concentrations. Lastly, we explain the combination of these three antibiotics administered to increase microbiologic and pharmacodynamic yield.

 
Rev Esp Quimioter 2010:23(2):103-108 [pdf]

In vitro activity of retapamulin against linezolid and methicillin–resistant Staphylococcus aureus isolates       

F. J. CANDEL, G. MORALES, J. J. PICAZO           

 

 

Objectives: To determine the in vitro activity of retapamulin and other topical antibiotics (mupirocin, bacitracin, and fusidic acid) usually employed for nasal decolonization, against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and linezolid and methicillin–resistant S. aureus.
Methods: The minimum inhibitory concentrations (MICs) were determined on Mueller-Hinton agar according to the guidelines of the Clinical and Laboratory Standards Institute and of the European Committee for Antimicrobial Susceptibility Testing. Presence of the cfr gene in linezolid and methicillin–resistant S. aureus isolates was detected using polymerase chain reaction.
Results: Retapamulin inhibited all the isolates of MSSA and MRSA at 0.125 mg/L, but the 18 linezolid-resistant-MRSA strains proved resistant, with MICs over 32 mg/L. Most MSSA isolates (9/10) were susceptible to mupirocin with MICs under 0.19 mg/L, although this value decreased to half against MRSA, and almost all linezolid-resistant MRSA (17/18) strains were resistant to mupirocin with an MIC range of between 8 mg/L and 28 mg/L. The MIC of fusidic acid increased substantially against linezolid-resistant MRSA, whereas that of bacitracin showed no differences.
Conclusions: Retapamulin demonstrated excellent in vitro activity against MSSA and MRSA strains, but not against MRSA isolates harbouring the cfr gene. The results of this in vitro study support cut-off values for retapamulin of ≤ 0.5, 1, and ≥ 2 mg/L for susceptible, intermediate, and resistant strains, respectively.

 
Rev Esp Quimioter 2011:24(3):127-130 [pdf]

Rifampin breakpoint for Acinetobacter baumannii based on pharmacokinetic-pharmacodynamic models with Monte Carlo simulation     

J. A LEPE, E. GARCÍA-CABRERA, M.V. GIL-NAVARRO, J. AZNAR                                                                

 
Objective: The aim of this study is to develop a pharmacokinetic–pharmacodynamic (PK–PD) rifampin breakpoint for Acinetobacter baumannii based on Monte Carlo simulation and to compare it with the reference value establish by the French Society for Microbiology (SFM).
Methods: A 10,000 subject’s Monte Carlo simulation for rifampin with intravenous dose of 10 mg/Kg/day and 20 mg/Kg/day was performed. The distribution of MIC was calculated using unique clinical isolates of A. baumannii. The PK–PD parameter calculated was Cmax_free/MIC.
Results: The isolates rifampin MIC₅₀ and MIC₉₀ were 2 and 32 mg/L respectively, ranging between 0.023-32 mg/L. According to interpretive criteria established by the SFM: 468 (75.8%) isolates were susceptible (MIC ≤ 4 mg/L) and 150 (24.2%) were non susceptible (MIC > 4 mg/L).
For 10 mg/Kg/day dose: the probability (%) of attaining Cmax_free/ MIC ratio values = 8 by Monte Carlo simulation in the study population was 0.4%, the rifampin MIC cut off value obtained from an optimal treatment (target ≥ 90%), was 0.125 mg/L. The probability of obtaining a Cmax_free/MIC ratio equal to 10 was 0.2% and the MIC cut off value obtained <0.125 mg/L.
At doses of 20 mg/kg/day: the probability of obtaining a Cmax_free/MIC ratio equal to 8 was 0.8%, the rifampin MIC cut off value obtained was 0.25 mg/L. For a Cmax_free/MIC = 10, it was 0.6% and 0.125 mg/L, respectively. The percentage of susceptible isolates ranging 0% to 1%, depending on the dose and therapeutic target used.
Conclusion: the rifampin breakpoints obtained from our PK/PD Monte Carlo simulation differ from those established by SFM, although further clinical studies in patients are needed to confirm our findings and improve the use of this antibiotic. 

 

Rev Esp Quimioter 2012:25(2):134-138 [pdf]

Colonial architecture and growth dynamics of Staphylococcus aureus resistant to methicillin

F. GÓMEZ-AGUDO, M. L. GÓMEZ-LUS, M. T. CORCUERA, L. ALOU, M. J. ALONSO, D. SEVILLANO, D. VAL, A. PALMEIRO, N. IGLESIAS, J. PRIETO

 

The aim of the study was to explore the structure and growth dynamics of Staphylococcus aureus resistant to methicillin (MRSA) colonies using semithin sections visualized by light microscope. One S. aureus susceptible to methicillin (MSSA) and one MRSA clinical strains were studied. Colonies in agar plates were embedded in epoxy resin after each incubation period (24 h and 48 h) at 37ºC. Semithin sections of 0.5µm were stained with toluidine blue and visualized by light microscope. Microscopically, no structural differences were observed between SASM and SARM colonies but differences were observed in both strains between 24 and 48 h incubation periods. Colonies showed two layers clearly differentiated at24 h independently of the resistance to methicillin: (A) one basal layer with high density of population in contact with culture media, and (B) one superficial layer with a lower density of population. Colonies showed four layers at 48 h:(A) one basal layer with high density of population; (B) one clear layer constituted by very degraded bacterial remains in which can be observed cocci dispersed with their dyeing properties; (C) one mixed layer constituted by viable bacteria and little degraded bacterial remains (D) one superficial layer with a lower density of population than basal layer. Colonial architecture is a complex and time-dependent process.

 
Rev Esp Quimioter 2009:22(4):224-227 [pdf]