Evaluation of a commercial immunochromatographic assay for rapid routine identification of PBP2a-positive Staphylococcus aureus and coagulase-negative staphylococci

Rapid visualization molecular fluorescence detection of methicillin-resistant Staphylococcus aureus using the multiplex MIRA-qPCR method

Multidrug-resistant (MDR) bacterial infections constitute a major public health problem worldwide. A rapid method for the detection of methicillin-resistant Staphylococcus aureus (MRSA) is critical for the timely prevention of bacterial infections and the accurate clinical use of drugs. The nuc and mecA genes are potentially indicative of MRSA infection and in this study, a multiplex molecular fluorescence multi-enzyme isothermal rapid amplification visual assay was proposed and established. The method is capable of detecting MRSA at 17 min, 40°C amplification, and is well differentiated from common clinical bacteria in specific assays, with 500 colony-forming units (CFU) mL-1 of MRSA detected under optimal conditions. This method has excellent diagnostic capabilities versus classical methods to detect clinical samples and shows potential in the identification of pathogenic microorganisms in a clinical setting.

A risk assessment framework for multidrug-resistant Staphylococcus aureus using machine learning and mass spectrometry technology

The emergence of multidrug-resistant bacteria is a critical global crisis that poses a serious threat to public health, particularly with the rise of multidrug-resistant Staphylococcus aureus. Accurate assessment of drug resistance is essential for appropriate treatment and prevention of transmission of these deadly pathogens. Early detection of drug resistance in patients is critical for providing timely treatment and reducing the spread of multidrug-resistant bacteria. This study aims to develop a novel risk assessment framework for S. aureus that can accurately determine the resistance to multiple antibiotics. The comprehensive 7-year study involved ˃20 000 isolates with susceptibility testing profiles of six antibiotics. By incorporating mass spectrometry and machine learning, the study was able to predict the susceptibility to four different antibiotics with high accuracy. To validate the accuracy of our models, we externally tested on an independent cohort and achieved impressive results with an area under the receiver operating characteristic curve of 0. 94, 0.90, 0.86 and 0.91, and an area under the precision-recall curve of 0.93, 0.87, 0.87 and 0.81, respectively, for oxacillin, clindamycin, erythromycin and trimethoprim-sulfamethoxazole. In addition, the framework evaluated the level of multidrug resistance of the isolates by using the predicted drug resistance probabilities, interpreting them in the context of a multidrug resistance risk score and analyzing the performance contribution of different sample groups. The results of this study provide an efficient method for early antibiotic decision-making and a better understanding of the multidrug resistance risk of S. aureus.

Prevalence, Mechanism, Genetic Diversity, and Cross-Resistance Patterns of Methicillin-Resistant Staphylococcus Isolated from Companion Animal Clinical Samples Submitted to a Veterinary Diagnostic Laboratory in the Midwestern United States

Methicillin-resistant Staphylococcus (MRS) is a leading cause of skin and soft tissue infections in companion animals, with limited treatment options available due to the frequent cross-resistance of MRS to other antibiotics. In this study, we report the prevalence, species distribution, genetic diversity, resistance mechanism and cross-resistance patterns of MRS isolated from companion animal (mostly dog and cat) clinical cases submitted to Iowa State University Veterinary Diagnostic Laboratory (ISU VDL) between 2012 and 2019. The majority of isolates were identified as Staphylococcus pseudintermedius (68.3%; 2379/3482) and coagulase-negative Staphylococcus (CoNS) (24.6%; 857/3482), of which 23.9% and 40.5% were phenotypically resistant to methicillin, respectively. Cross resistance to other β-lactams (and to a lesser extent to non-β-lactams) was common in both methicillin-resistant S. pseudintermedius (MRSP) and CoNS (MRCoNS), especially when oxacillin MIC was ≥4 μg/mL (vs. ≥0.5−<4 μg/mL). The PBP2a protein was detected by agglutination in 94.6% (521/551) MRSP and 64.3% (146/227) MRCoNS. A further analysis of 31 PBP2a-negative MRS isolates (all but one MRCoNS) indicated that 11 were mecA gene-positive while 20 were negative for mecA and other mec genes by PCR. The resistance to last-resort anti-staphylococcal human drugs (e.g., tigecycline, linezolid, vancomycin) among the MRS tested was none to very low. Even though genotyping indicated an overall high level of genetic diversity (87 unique PFGE patterns and 20 MLST types) among a subset of MRSP isolates tested (n = 106), certain genotypes were detected from epidemiologically connected cases at the same or different time points, suggesting persistence and/or nosocomial transmission. These results indicate a relatively high prevalence of MRS from companion animals in the Midwestern US; therefore, it is important to perform routine susceptibility testing of Staphylococcus in veterinary clinical settings for the selection of appropriate antimicrobial therapy.

Rapid MRSA detection via tandem mass spectrometry of the intact 80 kDa PBP2a resistance protein

Treatment of antibiotic-resistant infections is dependent on the detection of specific bacterial genes or proteins in clinical assays. Identification of methicillin-resistant Staphylococcus aureus (MRSA) is often accomplished through the detection of penicillin-binding protein 2a (PBP2a). With greater dependence on mass spectrometry (MS)-based bacterial identification, complementary efforts to detect resistance have been hindered by the complexity of those proteins responsible. Initial characterization of PBP2a indicates the presence of glycan modifications. To simplify detection, we demonstrate a proof-of-concept tandem MS approach involving the generation of N-terminal PBP2a peptide-like fragments and detection of unique product ions during top-down proteomic sample analyses. This approach was implemented for two PBP2a variants, PBP2amecA and PBP2amecC, and was accurate across a representative panel of MRSA strains with different genetic backgrounds. Additionally, PBP2amecA was successfully detected from clinical isolates using a five-minute liquid chromatographic separation and implementation of this MS detection strategy. Our results highlight the capability of direct MS-based resistance marker detection and potential advantages for implementing these approaches in clinical diagnostics.

Prevalence, risk-factors, and antimicrobial susceptibility profile of methicillin-resistant Staphylococcus aureus (MRSA) obtained from nares of patients and staff of Sokoto state-owned hospitals in Nigeria

Aim: The aim of the study was to determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) obtained from the nasal cavity of participants and investigate the antibiotic resistance profiles of the isolates from Sokoto state, Nigeria.

Methods: Nasal swabs of both nares were obtained from 378 participants across three study centers within the six-month study period. The Staphylococcus aureus isolates recovered were characterized, and their resistance phenotype determined in conjunction with MRSA prevalence.

Results: Phenotypic screening of isolates obtained in this study revealed a total of 131 (17.3%) coagulase-positive Staphylococci out of 756 samples. Of this number, there were 81 (61.8%) S. aureus, 36 (27.5%) Staphylococcus intermedius, 6 (4.5%) Staphylococcus hyicus, and 8 (6.1%) Staphylococcus schleiferi.

Conclusion: This study found a prevalence of 61.8% and 46.9% of S. aureus and MRSA among the studied hospitals in Sokoto state, thus demonstrating that the nares of the hospital populace are not free from S. aureus and MRSA colonization.

Diagnostic tools for bacterial infections in travellers: Current and future options

International travel has increased dramatically over the past 50 years, and travel destinations have diversified. Although physicians are more familiar with the panel of aetiological agents responsible for illnesses of returning travellers, thanks to regular epidemiological studies, the spectrum of pathogens potentially encountered in various travel destinations is nevertheless increasing. In addition, the wide array of approaches currently available and addressed in this paper could render the procedures for microbiological analyses increasingly complex. As the time to result is crucial to adequately manage patients, modern approaches have been developed to shorten diagnosis delays. The syndromic approach, which consists of simultaneously testing a wide panel of microorganisms, substantially increases the diagnostic yield with significant time savings, particularly when coupled with point-of-care laboratories. The tools commonly used for this purpose are immunochromatographic tests, mainly targeting bacterial antigens, and multiplex real-time PCR. The emergence of next-generation sequencing technologies, which enable random amplification of genetic material of any microbe present in a clinical specimen, provides further exciting perspectives in the diagnosis of infectious diseases.

Novel strategies for rapid identification and susceptibility testing of MRSA

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with adverse clinical outcomes and increased morbidity, mortality, length of hospital stay, and health-care costs. Rapid diagnosis of MRSA infections has been associated with positive impact on clinical outcomes.

AREAS COVERED

We searched relevant papers in PubMed for the last 10 years. In major papers, we scanned the bibliographies to ensure that important articles were included. This review describes screening and diagnostic test methods for MRSA and their analytical performances with a focus on rapid molecular-based assays including those that are on the horizon. Future novel technologies will allow more rapid detection of phenotypic resistance. In the case of whole-genome sequencing, detection of mutations may predict resistance, transmission, and virulence.

EXPERT OPINION

Currently there are many diagnostic options for the detection of MRSA in surveillance and clinical samples. In general, these are highly accurate and have resulted in improvements in targeted management and reduction in hospital or intensive care unit length of stay for both MSSA and MRSA. Impact on mortality has been variable. Promising novel technologies will not only accurately identify pathogens and detect their resistance markers but will allow discovery of virulence determinants that might further affect patient management.

Rapid Methods for Detection of MRSA in Clinical Specimens

Traditional antimicrobial susceptibility test methods for detection of S. aureus resistant to oxacillin (MRSA) such as disk diffusion, broth microdilution, and oxacillin screen plate require 18-24 h of incubation after having the organism growing in pure culture. Rapid and accurate identification of MRSA isolates is essential not only for patient care, but also for effective infection control programs to limit the spread of MRSA. In the last few years, several commercial rapid tests for detection of MRSA directly from nasal and wound swabs, as well as from positive blood cultures, have been developed for use in clinical laboratories. Chromogenic agar plates and real-time PCR and other molecular tests are gaining popularity as MRSA screening tests because they have the advantage of a lower turnaround time than that of traditional culture and susceptibility testing and they are capable of detecting MRSA directly from nasal and wound swabs, allowing rapid identification of colonized or infected patients. In addition, molecular methods able to detect and differentiate S. aureus and MRSA (SA/MRSA) directly from blood cultures are becoming a useful tool for rapid detection of bacteremia caused by MSSA and MRSA. This review focuses on the procedures for performing testing using rapid methods currently available for detection of MRSA directly from clinical specimens.

Improved Performance of a Rapid Immunochromatographic Assay for Detection of PBP2a in Non-Staphylococcus aureus Staphylococcal Species

Non-Staphylococcus aureus staphylococcal species (non-SASS) are important pathogens in both animal and human populations. The development of β-lactam resistance in non-SASS through acquisition and expression of penicillin-binding protein 2a (PBP2a) represents a significant clinical and public health threat. Here, we evaluated the diagnostic performance of two versions of a PBP2a immunochromatographic assay with non-SASS. Our data show that the revised version of the assay, the PBP2a SA culture colony test, has superior diagnostic sensitivity compared to the previous version of the assay, the PBP2a culture colony test, 100% (95% confidence interval [CI], 93.3 to 100%) versus 67.9% (95% CI, 53.7 to 80.1%), respectively, while both assays display a specificity of 100% (95% CI, 92.5 to 100%). Therefore, the PBP2a SA culture colony test offers a rapid, accurate, and relatively inexpensive method for detecting PBP2a-mediated β-lactam resistance in clinically relevant non-SASS for the management of infections due to these organisms and for antimicrobial stewardship.