[Linezolid, the first oxazolidinone antibiotic]

Staphylococcus capitis: insights into epidemiology, virulence, and antimicrobial resistance of a clinically relevant bacterial species

SUMMARYStaphylococcus capitis is divided into two subspecies, S. capitis subsp. ureolyticus (renamed urealyticus in 1992; ATCC 49326) and S. capitis subsp. capitis (ATCC 27840), and fits with the archetype of clinically relevant coagulase-negative staphylococci (CoNS). S. capitis is a commensal bacterium of the skin in humans, which must be considered an opportunistic pathogen of interest particularly as soon as it is identified in a clinically relevant specimen from an immunocompromised patient. Several studies have highlighted the potential determinants underlying S. capitis pathogenicity, resistance profiles, and virulence factors. In addition, mobile genetic element acquisitions and mutations contribute to S. capitis genome adaptation to its environment. Over the past decades, antibiotic resistance has been identified for S. capitis in almost all the families of the currently available antibiotics and is related to the emergence of multidrug-resistant clones of high clinical significance. The present review summarizes the current knowledge concerning the taxonomic position of S. capitis among staphylococci, the involvement of this species in human colonization and diseases, the virulence factors supporting its pathogenicity, and the phenotypic and genomic antimicrobial resistance profiles of this species.

Antibiotics and Bacterial Resistance-A Short Story of an Endless Arms Race

Despite the undisputed development of medicine, antibiotics still serve as first-choice drugs for patients with infectious disorders. The widespread use of antibiotics results from a wide spectrum of their actions encompassing mechanisms responsible for: the inhibition of bacterial cell wall biosynthesis, the disruption of cell membrane integrity, the suppression of nucleic acids and/or proteins synthesis, as well as disturbances of metabolic processes. However, the widespread availability of antibiotics, accompanied by their overprescription, acts as a double-edged sword, since the overuse and/or misuse of antibiotics leads to a growing number of multidrug-resistant microbes. This, in turn, has recently emerged as a global public health challenge facing both clinicians and their patients. In addition to intrinsic resistance, bacteria can acquire resistance to particular antimicrobial agents through the transfer of genetic material conferring resistance. Amongst the most common bacterial resistance strategies are: drug target site changes, increased cell wall permeability to antibiotics, antibiotic inactivation, and efflux pumps. A better understanding of the interplay between the mechanisms of antibiotic actions and bacterial defense strategies against particular antimicrobial agents is crucial for developing new drugs or drug combinations. Herein, we provide a brief overview of the current nanomedicine-based strategies that aim to improve the efficacy of antibiotics.

Antimicrobial stewardship and linezolid

BACKGROUND

Since 2002, linezolid, the first representative of the oxazolidinone class, has been widely prescribed, sometimes outside of approved indications. However, several cases of clinical outbreaks due to linezolid-resistant organisms have been reported, and its relatively high cost represents an economic challenge for hospital settings.

OBJECTIVES

The aim of this study was to assess the impact of different actions conducted by an antimicrobial stewardship team (AST) to control over-prescription of linezolid with regard to the defined daily dose (DDD) per 1,000 inhabitants per day.

SETTING

This work was conducted in a 1,495-bed hospital from 2009 to 2013. An AST, gathering the departments of pharmacy, microbiology, and infectious diseases, assessed the pertinence of linezolid use and associated effect on the prescriber.

METHOD

A retrospective study was conducted throughout 2009. Three different evaluations were prospectively carried out, each for 3 months, between 2011 and 2013.

MAIN OUTCOME MEASURE

The indicators chosen to monitor the consumption of linezolid were the DDD per 1,000 inhabitants per day, which enabled a comparison to be made between hospitals from 2004 to 2012, and of the pertinence of its prescription by different departments.

RESULTS

From 2009 to 2013, 239 patients were evaluated through three 3-month stages. Prescriptions were for off-label use in 45 % of cases. Prescriptions were considered appropriate in 60 % of cases. Unsuitable treatment was either modified or discontinued (62 and 38 % of cases, respectively). Mean duration of linezolid treatment was 8 days, i.e. below the national mean duration reported in the literature. To highlight the impact of action taken by the team, a consensual strategy to treat ventilator-acquired pneumonia was elaborated with principal prescribers. Throughout the study, the mean DDD per 1,000 inhabitants per day increased very slowly and was lower than the eleven other French hospitals, which were secondarily included in this study.

CONCLUSION

The multidisciplinary approach that was adopted for therapeutic education and delivery control led to an improvement in the proper use of linezolid. Similar strategy should be extended to other antimicrobial agents, such as carbapenems, for which both cost and risk of resistance emergence are of major concern.

[Proper use of antibiotics: a prospective study on the use of linezolid in a French university hospital]

AIM OF THE STUDY

To describe clinical use of a new antibiotic: linezolid, in a French university hospital, on a population of patients different from the one studied during the clinical trials for the marketing authorisation.

PATIENTS AND METHODS

An observational, prospective cohort study performed in patients treated by linezolid between November 2005 and June 2006 at Saint André hospital (Bordeaux University Hospital). The following data were collected: sources of infection, isolated pathogens, patient's background, antibiotherapy strategies, duration of therapy and evolution.

RESULTS

Fifty patients (intensive care, internal medicine) were included. The absence of local guidelines on proper use of linezolid led to various prescriptions as well in infections listed in the marketing authorisation: nosocomial pneumonia and ventilator associated pneumonia (48%), skin and soft tissue infections (11%), as in endocarditis (7%), intra-abdominal infections (13%), bone and joint infections (2%), catheter infections (13%) and febrile neutropenic patients (6%). The main justification for using linezolid was worsening renal dysfunction (66%), which contra indicated glycopeptides use. Isolated pathogens were for the major part staphylococcus.

CONCLUSION

In the context of proper use of antibiotics, it would be advisable to add new recommendations on the use of linezolid to the hospital's antibiotherapy guide which would constitute a tool for the prescribing clinicians, and to re-evaluate the impact during a second evaluation.

[Use of linezolid for the treatment of lung infections in adults with cystic fibrosis]

INTRODUCTION

Linezolid, a new antistaphylococcal agent for oral or intravenous administration is active against Staphylococcus aureus with limited sensitivity to glycopeptides. The purpose of the present work was to compare data in the literature with practical clinical experience with the use of linezolid for lung infections in adult cystic fibrosis patients with the objective of developing local guidelines for use.

MATERIAL AND METHODS

This retrospective clinical study was conducted in the adult pneumology department of a university hospital.

RESULTS

The main clinical signs leading to prescription of linezolid were aggravating cough, bronchial obstruction, and exercise-induced fatigue. Among 42 cystic fibrosis patients, six aged 24+/-3 years were given 22 treatments of linezolid. Two patients were given the drug once and the others 2, 4, 5, and 9 times, 600 mg b.i.d. Mean duration of treatment with linezolid was 16+/-5 days. Among the six patients, two presented meti-R S. aureus infection. For twelve cases, clinical improvement was observed; and in two others the situation worsened leading to interruption of linezolid.

CONCLUSIONS

There are few reports in the literature on use of linezolid in cystic fibrosis patients. Writing internal guidelines for our department has enabled standardized use: 600 mg b.i.d. p.o. for 14 days as second-line treatment for bronchial exacerbation of S. aureus infection.