Outcome of Acute Prosthetic Joint Infections Due to Gram-Negative Bacilli Treated with Open Debridement and Retention of the Prosthesis

Antimicrobial Agents and Chemotherapy  1 Nov 2009  V.53  N.11  p.4772-4777

Juan C. Martínez-Pastor,1 Ernesto Muñoz-Mahamud,1 Félix Vilchez,1 Sebastián García-Ramiro,1 Guillem Bori,1 Josep Sierra,2 José A. Martínez,2 Lluis Font,1 Josep Mensa,2 and Alex Soriano2*

Department of Orthopaedics of Hospital Clinic of Barcelona,1 Department of Infectious Diseases of Hospital Clínic of Barcelona, Hospital Clínic Universitari, IDIBAPS, Barcelona, Spain2

The aim of our study was to evaluate the outcome of acute prosthetic joint infections (PJIs) due to gram-negative bacilli (GNB) treated without implant removal. Patients with an acute PJI due to GNB diagnosed from 2000 to 2007 were prospectively registered. Demographics, comorbidity, type of implant, microbiology data, surgical treatment, antimicrobial therapy, and outcome were recorded. Classification and regression tree analysis, the Kaplan-Meier survival method, and the Cox regression model were applied. Forty-seven patients were included. The mean age was 70.7 years, and there were 15 hip prostheses and 32 knee prostheses. The median number of days from the time of arthroplasty was 20. The most frequent pathogens were members of the Enterobacteriaceae family in 41 cases and Pseudomonas spp. in 20 cases. Among the Enterobacteriaceae, 14 were resistant to ciprofloxacin, while all Pseudomonas aeruginosa isolates were susceptible to ciprofloxacin. The median durations of intravenous and oral antibiotic treatment were 14 and 64 days, respectively. A total of 35 (74.5%) patients were in remission after a median follow-up of 463 days (interquartile range, 344 to 704) days. By use of the Kaplan-Meier survival curve, a C-reactive protein (CRP) concentration of 15 mg/dl (P = 0.03) and receipt of a fluoroquinolone, when all GNB isolated were susceptible (P = 0.0009), were associated with a better outcome. By use of a Cox regression model, a CRP concentration of 15 mg/dl (odds ratio [OR], 3.57; 95% confidence interval [CI], 1.05 to 12.5; P = 0.043) and receipt of a fluoroquinolone (OR, 9.09; 95% CI, 1.96 to 50; P = 0.005) were independently associated with better outcomes. Open debridement without removal of the implant had a success rate of 74.5%, and the factors associated with good prognosis were a CRP concentration at the time of diagnosis 15 mg/dl and treatment with a fluoroquinolone.

abstract

http://aac.asm.org/cgi/content/abstract/53/11/4772

 

Penetration of Colistin into Cerebrospinal Fluid

Antimicrobial Agents and Chemotherapy  1 Nov 2009  V.53  N.11  p.4907-4910

S. L. Markantonis,1* N. Markou,2 M. Fousteri,1 N. Sakellaridis,3 S. Karatzas,4 I. Alamanos,2 E. Dimopoulou,2 and G. Baltopoulos4

University of Athens, Faculty of Pharmacy, Laboratory of Biopharmaceutics and Pharmacokinetics, 157.71 Athens, Greece,1 ICU-B, KAT Hospital, 2 Nikis Str. Kifissia, 145.61 Athens, Greece,2 Department of Neurosurgery, KAT Hospital, 2 Nikis Str. Kifissia, 145.61 Athens, Greece,3 University of Athens School of Nursing ICU, KAT Hospital, 2 Nikis Str. Kifissia, 145.61 Athens, Greece4

Colistin penetration into the cerebrospinal fluid (CSF) was studied in five critically ill adult patients receiving colistin methanesulfonate for infections by multiresistant gram-negative bacilli. Colistin concentrations were determined in paired serum and CSF samples, with the latter taken by lumbar puncture, with the exception of one patient with an external ventriculostomy. CSF-to-serum ratios (0.051 to 0.057) for all study patients coincided at all sampling times. The low level (5%) of penetration suggests inadequate bactericidal colistin concentrations in the CSF.

abstract

http://aac.asm.org/cgi/content/abstract/53/11/4907

 

VanA-Type Vancomycin-Resistant Staphylococcus aureus

Antimicrobial Agents and Chemotherapy  1 Nov 2009  V.53  N.11

MINIREVIEW

Bruno Périchon and Patrice Courvalin*

Institut Pasteur, Unité des Agents Antibactériens, Paris, France

Since 2002, nine methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) strains that are also resistant to vancomycin (VRSA) have been reported in the United States, including seven clinical isolates from Michigan. The strains harbor a plasmid-borne Tn1546 element following conjugation from a glycopeptide-resistant Enterococcus strain. In the second step, Tn1546 transposed to a resident plasmid in five strains; the acquired plasmid behaved as a suicide gene delivery vector, and the incoming DNA had been rescued by illegitimate recombination. Surprisingly, combination of a glycopeptide with a β-lactam has a strong synergistic effect against VRSA, both in vitro and in an animal model, despite resistance of the strains to both drug classes when administered separately. This results from the fact that the late peptidoglycan precursors ending in D-alanine-D-lactate (D-Ala-D-Lac) that are mainly synthesized in the presence of glycopeptide inducers are not substrates for PBP2′, which is the only transpeptidase that remains active in the presence of oxacillin. One VRSA strain is partially dependent on vancomycin for growth due to a mutation in the host D-Ala:D-Ala ligase, thus having to rely on the inducible resistance pathway for cell wall synthesis. Competition growth experiments in the absence of inducer between the MRSA recipient and isogenic VRSA transconjugant revealed a disadvantage for the transconjugant, accounting, in part, for the low level of dissemination of the VRSA clinical isolates. The association of multiple molecular and environmental factors has been implicated in the regional emergence of VRSA in Michigan.

abstract

http://aac.asm.org/cgi/content/abstract/53/11/4580