Evaluación de una PCR multiplex en tiempo real para la detección de patógenos en el tejido valvular de pacientes con endocarditis

Identification and Antibiotic-Susceptibility Profiling of Infectious Bacterial Agents: A Review of Current and Future Trends

Antimicrobial resistance is one of the most worrying threats to humankind with extremely high healthcare costs associated. The current technologies used in clinical microbiology to identify the bacterial agent and profile antimicrobial susceptibility are time-consuming and frequently expensive. As a result, physicians prescribe empirical antimicrobial therapies. This scenario is often the cause of therapeutic failures, causing higher mortality rates and healthcare costs, as well as the emergence and spread of antibiotic resistant bacteria. As such, new technologies for rapid identification of the pathogen and antimicrobial susceptibility testing are needed. This review summarizes the current technologies, and the promising emerging and future alternatives for the identification and profiling of antimicrobial resistance bacterial agents, which are expected to revolutionize the field of clinical diagnostics.

Contemporary approaches to the rapid molecular diagnosis of sepsis

INTRODUCTION

Although the administration of appropriate antimicrobials within the very first hour remains the mainstay of sepsis management, the correct selection of antimicrobials is hampered by the delay of conventional microbiology providing results after at least 48 hours. Methods of rapid detection of pathogens are an approach to overcome these difficulties. Areas covered: This review analyzes the advantages and the disadvantages of these approaches with major emphasis on technologies based on multiplex PCR for the rapid detection of pathogens using whole blood. The most broadly studied platform is SeptFast. Sensitivity ranges between 42% and 73% and specificity between 50% and 97%. The main disadvantages are high cost, the risk of contamination and the lack of information for the presence of resistance genes. A brief review of the use of PCR techniques for the diagnosis of endocarditis and of the recognition of the bacterial proteome for the rapid identification of grown colonies (MALDI-TOF) is also provided. Expert commentary: More randomized clinical trials are necessary to validate the use of molecular techniques for decision-making for patients' outcomes, taking into consideration the cost-benefit for the patient.

Beyond Blood Culture and Gram Stain Analysis: A Review of Molecular Techniques for the Early Detection of Bacteremia in Surgical Patients

BACKGROUND

Sepsis from bacteremia occurs in 250,000 cases annually in the United States, has a mortality rate as high as 60%, and is associated with a poorer prognosis than localized infection. Because of these high figures, empiric antibiotic administration for patients with systemic inflammatory response syndrome (SIRS) and suspected infection is the second most common indication for antibiotic administration in intensive care units (ICU)s. However, overuse of empiric antibiotics contributes to the development of opportunistic infections, antibiotic resistance, and the increase in multi-drug-resistant bacterial strains. The current method of diagnosing and ruling out bacteremia is via blood culture (BC) and Gram stain (GS) analysis.

METHODS

Conventional and molecular methods for diagnosing bacteremia were reviewed and compared. The clinical implications, use, and current clinical trials of polymerase chain reaction (PCR)-based methods to detect bacterial pathogens in the blood stream were detailed.

RESULTS

BC/GS has several disadvantages. These include: some bacteria do not grow in culture media; others do not GS appropriately; and cultures can require up to 5 d to guide or discontinue antibiotic treatment. PCR-based methods can be potentially applied to detect rapidly, accurately, and directly microbes in human blood samples.

CONCLUSIONS

Compared with the conventional BC/GS, particular advantages to molecular methods (specifically, PCR-based methods) include faster results, leading to possible improved antibiotic stewardship when bacteremia is not present.

Multiplex PCR performed of bronchoalveolar lavage fluid increases pathogen identification rate in critically ill patients with pneumonia: a pilot study

Background

In critically ill patients with pneumonia, accurate microorganism identification allows appropriate antibiotic treatment. In patients undergoing bronchoalveolar lavage (BAL), direct examination of the fluid using Gram staining provides prompt information but pathogen identification accuracy is low. Culture of BAL fluid is actually the reference, but it is not available before 24 to 48 h. In addition, pathogen identification rate observed with direct examination and culture is decreased when antibiotic therapy has been given prior to sampling. We therefore assessed, in critically ill patients with suspected pneumonia, the performance of a multiplex PCR (MPCR) to identify pathogens in BAL fluid. This study is a prospective pilot observation.

Methods

We used a MPCR detecting 20 types of microorganisms. Direct examination, culture, and MPCR were performed on BAL fluid of critically ill patients with pneumonia suspicion. The final diagnosis of infective pneumonia was retained after the medical chart was reviewed by two experts. Pathogen identification rate of direct examination, culture, and MPCR in patients with confirmed pneumonia was compared.

Results

Among the 65 patients with pneumonia suspicion, the diagnosis of pneumonia was finally retained in 53 cases. Twenty nine (55%) were community-acquired pneumonia and 24 (45%) were hospital acquired. Pathogen identification rate with MPCR (66%) was greater than with culture (40%) and direct examination (23%) (p =0.01 and p <0.001, respectively). When considering only the microorganisms included in the MPCR panel, the pathogen identification rate provided by MPCR reached 82% and was still higher than with culture (35%, p <0.001) and direct examination (21%, p <0.001). Pathogen identification rate provided by MPCR was not modified in the case of previous antibiotic treatment (66% vs. 64%, NS) and was still better than with culture (23%, p <0.001).

Conclusions

The results of this pilot study suggest that in critically ill patients, MPCR performed on BAL fluid could provide higher identification rate of pathogens involved in pneumonia than direct examination and culture, especially in patients having received antimicrobial treatment.

Use of multiplex PCR in diagnosis of bloodstream infections in kidney patients

The LightCycler® SeptiFast Test (Roche Diagnostics GmbH, Mannheim, Germany) was prospectively compared with the standard blood culture technique in a series of 86 kidney patients. The sensitivity of the PCR compared with the culture was 71%, and the specificity was 88%. All the species identified by culture in these patients were in the SeptiFast panel. The median time to results was 1 day for the PCR, 3 days for positive cultures, and 5 days for negative cultures.

Nonculture techniques for the detection of bacteremia and fungemia

ABSTRACT: 

Bacteremia and fungemia account for a substantial proportion of all cases of severe sepsis. Antibiotic resistance is a contributing factor in many hospital-acquired infection deaths. Traditional phenotypic methods for the identification of bacteria and yeasts from positive blood cultures and determining antimicrobial susceptibility require 48–72 h, delaying optimal therapy and negatively impacting patient outcomes. Molecular methods, including nonamplified DNA probe panels and peptide nucleic acid probes, and nucleic acid amplification methods such as PCR, proteomic methods (matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry) and direct biochemical tests provide more rapid identification of bacteria and fungi, and in some cases antimicrobial resistance markers, from positive blood cultures, as well as directly from whole blood. These methods vary in the breadth of organisms that they detect, and equally important, their ease of use. This article examines the principles, performance and practicality of the various rapid, nonculture techniques for the detection of bacteremia and fungemia.

PCR-electrospray ionization time-of-flight mass spectrometry: a new tool for the diagnosis of infective endocarditis from heart valves

A polymerase chain reaction with an injection of the amplicons in an electrospray ionization mass spectrometry (PCR-ESI-MS) technique was evaluated for the diagnosis of bacterial and yeast pathogens on 13 cardiac valves with suspected endocarditis. At the moment of surgery, 3/13 PCR-ESI-MS results matched with microbiological documentation. Nine PCR-ESI-MS results correlated with Duke's criteria, leukocytes, C-reactive protein and blood cultures before surgery. The PCR-ESI-MS result of the last valve failed to confirm the blood culture result obtained fifteen days before. With speed and accuracy, this method may be useful to assert microbiological identification and adapt treatment.