Posts filed under ‘Resistencia bacteriana’

Selective Conditions for a Multidrug Resistance Plasmid Depend on the Sociality of Antibiotic Resistance

Antimicrobial Agents and Chemotherapy April 2016 V.60 N.4 P.2524-2527

Michael J. Bottery, A. Jamie Wood, and Michael A. Brockhurst

aDepartment of Biology, University of York, York, United Kingdom

bDepartment of Mathematics, University of York, York, United Kingdom

Multidrug resistance (MDR) plasmids frequently carry antibiotic resistance genes conferring qualitatively different mechanisms of resistance.

We show here that the antibiotic concentrations selecting for the RK2 plasmid in Escherichia coli depend upon the sociality of the drug resistance: the selection for selfish drug resistance (efflux pump) occurred at very low drug concentrations, just 1.3% of the MIC of the plasmid-free antibiotic-sensitive strain, whereas selection for cooperative drug resistance (modifying enzyme) occurred at drug concentrations exceeding the MIC of the plasmid-free strain.


February 23, 2017 at 7:52 am

Rapid Emergence and Evolution of Staphylococcus aureus Clones Harboring fusC-Containing Staphylococcal Cassette Chromosome Elements

Antimicrobial Agents and Chemotherapy April 2016 V.60 N.4 P.2359-2365

Sarah L. Baines, Benjamin P. Howden, Helen Heffernan, Timothy P. Stinear, Glen P. Carter, Torsten Seemann, Jason C. Kwong, Stephen R. Ritchie, and Deborah A. Williamson

aDoherty Applied Microbial Genomics, Department of Microbiology & Immunology, The University of Melbourne at The Doherty Institute for Infection and Immunity, Melbourne, Australia

bMicrobiological Diagnostic Unit Public Health Laboratory, Department of Microbiology & Immunology, The University of Melbourne at The Doherty Institute for Infection and Immunity, Melbourne, Australia

cInfectious Diseases Department, Austin Health, Melbourne, Australia

dInstitute of Environmental Science and Research, Wellington, New Zealand

eVictorian Life Sciences Computation Initiative, The University of Melbourne, Melbourne, Australia

fSchool of Medical Sciences, University of Auckland, Auckland, New Zealand

The prevalence of fusidic acid (FA) resistance among Staphylococcus aureus strains in New Zealand (NZ) is among the highest reported globally, with a recent study describing a resistance rate of approximately 28%.

Three FA-resistant S. aureus clones (ST5 MRSA, ST1 MSSA, and ST1 MRSA) have emerged over the past decade and now predominate in NZ, and in all three clones FA resistance is mediated by the fusC gene. In particular, ST5 MRSA has rapidly become the dominant MRSA clone in NZ, although the origin of FA-resistant ST5 MRSA has not been explored, and the genetic context of fusC in FA-resistant NZ isolates is unknown.

To better understand the rapid emergence of FA-resistant S. aureus, we used population-based comparative genomics to characterize a collection of FA-resistant and FA-susceptible isolates from NZ. FA-resistant NZ ST5 MRSA displayed minimal genetic diversity and represented a phylogenetically distinct clade within a global population model of clonal complex 5 (CC5) S. aureus.

In all lineages, fusC was invariably located within staphylococcal cassette chromosome (SCC) elements, suggesting that SCC-mediated horizontal transfer is the primary mechanism of fusC dissemination.

The genotypic association of fusC with mecA has important implications for the emergence of MRSA clones in populations with high usage of fusidic acid. In addition, we found that fusC was colocated with a recently described virulence factor (tirS) in dominant NZ S. aureus clones, suggesting a fitness advantage.

This study points to the likely molecular mechanisms responsible for the successful emergence and spread of FA-resistant S. aureus.


February 23, 2017 at 7:51 am

Infectious Complications Following Transrectal Ultrasound–Guided Prostate Biopsy: New Challenges in the Era of Multidrug-Resistant Escherichia coli

Clinical Infectious Diseases July 15, 2013 V.57 N.2 P.267-274


Deborah A. Williamson, Lucinda K. Barrett, Benjamin A. Rogers, Joshua T. Freeman, Paul Hadway, and David L. Paterson

1Faculty of Medical and Health Sciences, University of Auckland

2Department of Clinical Microbiology, Auckland District Health Board, New Zealand

3The University of Queensland, UQ Centre for Clinical Research, Brisbane

4Department of Urology, Royal Brisbane and Women’s Hospital, Herston, Queensland, Australia

Transrectal ultrasound (TRUS)–guided prostate biopsy is currently considered the standard technique for obtaining tissue to make a histological diagnosis of prostatic carcinoma. Infectious complications following TRUS-guided prostate biopsy are well described, and are reportedly increasing in incidence.

The role of antibiotic prophylaxis in reducing post–TRUS biopsy infections is now established, and many guidelines suggest that fluoroquinolone antimicrobials are the prophylactic agents of choice.

Of note, however, recent reports suggest an emerging association between TRUS biopsy and subsequent infection with fluoroquinolone-resistant Escherichia coli.

Against this background, we provide an overview of the epidemiology, prevention, and treatment of infectious complications following TRUS biopsy, in the wider context of increasing global antimicrobial resistance.


We provide an overview of the published literature relating to the epidemiology, prevention, and treatment of infections following transrectal ultrasound–guided prostate biopsy in the wider context of increasing antimicrobial resistance.


February 20, 2017 at 3:21 pm

Editorial Commentary – Combination Therapy for Pseudomonas aeruginosa Bacteremia: Where Do We Stand?

Clinical Infectious Diseases July 15, 2013 V.57 N.2 P.217-220

Mical Paul and Leonard Leibovici

Correspondence: Mical Paul, MD, Unit of Infectious Diseases, Rambam Healthcare Campus, 6 Ha’Aliya Street, Haifa 31096, Israel (

Substantial evidence from randomized controlled trials (RCTs) refutes an advantage to β-lactam–aminoglycoside combination therapy for sepsis [1]. However, there are gaps in this body of evidence. The number of patients with gram-negative bacteremia evaluated for mortality in all trials to date amounts to fewer than 200 [1]; patients with Pseudomonas aeruginosa bacteremia have not been evaluated separately; and patients with septic shock are usually excluded from RCTs [2]. In general, patients included in RCTs are not representative of the patient population seen in general practice [3]. In this issue of Clinical Infectious Diseases, Peña et al present the first large prospective study of P. aeruginosa bacteremia, specifically addressing the issue of combination therapy versus monotherapy [4]. Special reasons exist for the focus on P. aeruginosa, including the paucity of treatment options, in vitro data suggesting synergy [5], and the high mortality associated with P. aeruginosa bacteremia [6]. Indeed, in Peña’s contemporary cohort, the 30-day mortality following P. aeruginosa bacteremia was 30%.


The 2 main reasons quoted in favor of combination therapy for P. aeruginosa bacteremia are to increase the probability of appropriate empirical coverage and to improve overall the antibiotics’ activity through synergism. Peña et al’s study addresses the question of synergy. The authors examined the association of combination therapy with survival among patients when all antibiotics were covering. Both in the empirical and definitive stages of treatment, no significant advantage to combination therapy was observed in this largest cohort to date including 632 episodes of P. aeruginosa …


February 19, 2017 at 11:42 am

Effect of Adequate Single-Drug vs Combination Antimicrobial Therapy on Mortality in Pseudomonas aeruginosa Bloodstream Infections: A Post Hoc Analysis of a Prospective Cohort

Clinical Infectious Diseases July 15, 2013 V.57 N.2 P.208-216

Carmen Peña, Cristina Suarez, Alain Ocampo-Sosa, Javier Murillas, Benito Almirante, Virginia Pomar, Manuela Aguilar, Ana Granados, Esther Calbo, Jesús Rodríguez-Baño, Fernando Rodríguez, Fe Tubau, Antonio Oliver, Luis Martínez-Martínez, and for the Spanish Network for Research in Infectious Diseases (REIPI)

1Servicio de Enfermedades Infecciosas, Hospital Universitario de Bellvitge–IDIBELL, Barcelona

2Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla–IFIMAV, Santander

3Servicio de Microbiología y Unidad de Enfermedades Infecciosas, Hospital Universitario de Son Espases, Palma de Mallorca

4Servicio de Enfermedades Infecciosas, Hospital Universitario Vall d’Hebrón

5Unidad de Enfermedades Infecciosas, Hospital Santa Creu i Sant Pau, Barcelona

6Servicio de Enfermedades Infecciosas, Hospital Universitario Virgen del Rocío, Sevilla

7Sección de Enfermedades Infecciosas, Consorci Hospitalari Parc Taulí, Sabadell

8Sección de Enfermedades Infecciosas, Hospital Mutua de Terrasa

9Sección de Enfermedades Infecciosas, Hospital Universitario Virgen Macarena, Sevilla

10Servicio de Microbiología Infecciosas, Hospital Universitario Reina Sofía–IMIBIC, Córdoba

11Departamento de Biología Molecular, Universidad de Cantabria, Santander, Spain


Empirical combination therapy is recommended for patients with known or suspected Pseudomonas aeruginosa (PA) infection as a means to decrease the likelihood of administering inadequate antimicrobial treatment, to prevent the emergence of resistance, and to achieve a possible additive or even synergistic effect.


We performed a post hoc analysis of patients with PA bloodstream infections from a published prospective cohort. Mortality was compared in patients treated with adequate empirical and definitive combination therapy (AECT, ADCT), and adequate empirical and definitive single-drug therapy (AESD, ADSD). Confounding was controlled by Cox regression analysis, and a propensity score for receiving AECT or ADCT was also used.


The final cohort comprised 593 patients with a single episode of PA bacteremia. The 30-day mortality was 30% (176 patients); 76 patients (13%) died during the first 48 hours. The unadjusted probabilities of survival until day 30 were 69.4% (95% confidence interval [CI], 59.1–81.6) for the patients receiving AECT, 73.5% (95% CI, 68.4%–79.0%) for the AESD group, and 66.7% (95% CI, 61.2%–72.7%) for patients who received inadequate empirical therapy (P = .17, log-rank test). After adjustment for confounders, the AESD group (adjusted hazard ratio [AHR], 1.17; 95% CI, .70–1.96; P = .54) and patients who received ADSD (AHR, 1.34; 95% CI, .73–2.47; P = .35) showed no association with 30-day mortality compared with the AECT and ADCT groups, respectively.


These results suggests that treatment with combination antimicrobial therapy did not reduce the mortality risk compared with single-drug therapy in PA bloodstream infections. Empirical combination therapy is recommended for patients with known or suspected Pseudomonas aeruginosa (PA). A post hoc analysis of patients with PA bloodstream infections suggests that treatment with combination antimicrobial therapy did not reduce the mortality risk compared with single-drug therapy.


February 19, 2017 at 11:40 am

Discontinuation of Contact Precautions for Methicillin-Resistant Staphylococcus aureus: A Randomized Controlled Trial Comparing Passive and Active Screening With Culture and Polymerase Chain Reaction

Clinical Infectious Diseases July 15, 2013 V.57 N.2 P.176-184

Erica S. Shenoy, JiYeon Kim, Eric S. Rosenberg, Jessica A. Cotter, Hang Lee, Rochelle P. Walensky, and David C. Hooper

1Harvard Medical School

2Division of Infectious Diseases, Department of Medicine

3Biostatistics Center

4Center for AIDS Research

5Department of Pathology

6Infection Control Unit, Massachusetts General Hospital, Boston, Massachusetts


There have been no randomized controlled trials comparing active and passive screening for documenting clearance of colonization with methicillin-resistant Staphylococcus aureus (MRSA). We compared the efficacy of active and passive screening using both culture and commercial polymerase chain reaction (PCR) for documentation of MRSA clearance and discontinuation of MRSA contact precautions (CPs).


Inpatients with a history of MRSA infection or colonization enrolled between December 2010 and September 2011 were randomized to either passive (nonintervention arm; n = 202; observation with local standard of care) or active screening (intervention arm; n = 405; study staff screened using culture and commercial PCR). The primary outcome was discontinuation of CPs by trial arm based on 3 negative cultures. In the intervention arm, sensitivity, specificity, and positive and negative predictive values of the first PCR were compared to cultures.


CPs were discontinued significantly more often (rate ratio [RR], 4.1; 95% confidence interval [CI], 2.3%–7.1%) in the intervention arm, including in an intent-to-screen analysis (RR, 2.6; 95% CI, 1.5%–4.7%). The first PCR, compared to 3 cultures, detected MRSA with a sensitivity of 93.9% (95% CI, 85.4%–97.6%), a specificity of 92.0% (95% CI, 85.9%–95.6%), a positive predictive value of 86.1% (95% CI, 75.9%–93.1%), and a negative predictive value of 96.6% (95% CI, 91.6%–99.1%).


Compared to passive screening using culture methods, active screening resulted in discontinuation of MRSA CPs at a significantly higher frequency. Active screening with a single PCR would significantly increase the completion of the screening process. In this randomized controlled trial, active screening was superior to passive screening for discontinuation of contact precautions for methicillin-resistant Staphylococcus aureus, and a single negative nasal swab processed by polymerase chain reaction had a high negative predictive value compared to 3 nasal cultures. Clinical Trials Registration. NCT01234831.


February 19, 2017 at 11:35 am

Diagnosis and management of prosthetic joint infection: clinical practice guidelines by the Infectious Diseases Society of America

Clin Infect Dis. 2013 Jan;56(1):e1-e25.

Osmon DR1, Berbari EF, Berendt AR, Lew D, Zimmerli W, Steckelberg JM, Rao N, Hanssen A, Wilson WR; Infectious Diseases Society of America.

Author information

1Division of Infectious Diseases, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.


These guidelines are intended for use by infectious disease specialists, orthopedists, and other healthcare professionals who care for patients with prosthetic joint infection (PJI). They include evidence-based and opinion-based recommendations for the diagnosis and management of patients with PJI treated with debridement and retention of the prosthesis, resection arthroplasty with or without subsequent staged reimplantation, 1-stage reimplantation, and amputation.


February 14, 2017 at 8:09 am

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