Selection and Identification of a DNA Aptamer for Multidrug-Resistant Acinetobacter baumannii Using an In-House Cell-SELEX Methodology

Infections caused by multidrug-resistant A. baumannii are a worldwide health concern with high mortality rates. Rapid identification of this infectious agent is critical as it can easily spread with difficult or no options for treatment. In this context, the development of reliable and economically viable detection and therapeutic methodologies are still challenging. One of the promising solutions is the development of nucleic acid aptamers capable of interacting with bacteria. These aptamers can be used for specific recognition of infectious agents as well as for blocking their functions. Cell-SELEX technology currently allows the selection and identification of aptamers and is flexible enough to target molecules present in an entire bacterial cell without their prior knowledge. However, the aptamer technology is still facing many challenges, such as the complexity of the screening process. Here, we describe the selection and identification of a new aptamer A01, using an in-house whole-cell SELEX-based methodology, against multi-resistant Acinetobacter baumannii, with rapid execution and low cost. In addition, this protocol allowed the identification of the aptamer A01 with the whole A. baumannii cell as a target. The aptamer A01 demonstrated a binding preference to A. baumannii when compared to K. pneumoniae, C. albicans, and S. aureus in fluorescence assays. Although the time-kill assay did not show an effect on bacterial growth, the potential bactericidal or bacteriostatic cannot be totally discarded. The new categorized aptamer (A01) displayed a significant binding affinity to MDR A. baumannii.

Prevalence of methicillin-resistant Staphylococcus aureus colonization in individuals from the community in the city of Sao Paulo, Brazil

Staphylococcus aureus (SA) is a commensal habitant of nasal cavities and skin. Colonization by community-acquired methicillin-resistant SA (CA-MRSA) is associated with infections in patients who have not been recently hospitalized. The aim of this study is to determine the prevalence of MRSA colonization in an outpatient population, currently unknown in Brazil. Three-hundred patients or caregivers from two teaching hospitals were included. A questionnaire was applied and nasal swabs were obtained from patients. Swabs were inoculated in brain heart infusion (BHI) with 2.5% NaCl and seeded in mannitol. Suspicious colonies were subjected to MALDI-TOF MS Microflex™ identification. Antimicrobial susceptibility test for oxacillin was performed for SA-positive samples by microdilution. Polymerase chain-reactions for detection of mecA and coA genes were performed for resistant samples. Data about MRSA carriers were compared with non-carriers. There were 127 S. aureus isolates, confirmed by MALDI-TOF. Only seven (2.3%) were MRSA and positive for mecA and coA genes. Factors associated with MRSA carriage were African ethnicity, skin diseases or antibiotic use. The majority of them were from Dermatology clinics. Prevalence of MRSA colonization in individuals from the community was low in our study (2.3%). This finding raises the hypothesis of inter-household transmission of SA, although we did not find any association between MRSA-colonization and the shared use of personal objects. Given the low prevalence of MRSA carriers observed, empirical antimicrobial coverage for MRSA in community-acquired infections should be not necessary.

Susceptibility to chlorhexidine and mupirocin among methicillin-resistant Staphylococcus aureus clinical isolates from a teaching hospital

Despite the widespread use of chlorhexidine (CHX) to prevent infection, data regarding the in vitro action of CHX against methicillin-resistant Staphylococcus aureus(MRSA) are limited. Clinical isolates from Hospital das Clinicas, Sao Paulo, Brazil, identified during 2002/2003 and 2012/2013 were studied to describe the susceptibility to CHX and mupirocin, molecular characteristics, and virulence profile of MRSA. Susceptibility test to Mupirocin was performed by the disk diffusion method and to CHX by the agar dilution technique. PCR for virulence genes, mecA gene and Staphylococcal Cassette Chromosome mec (SCCmec) types were investigated as well. Mupirocin- and CHX-resistant isolates were sequenced using the Illumina^TM plataform. Two hundred and sixteen MRSA clinical isolates were evaluated: 154 from infected and 62 from colonized patients. Resistance to mupirocin was observed in four isolates assigned as SCCmec type III and STs (ST05; ST239 and ST105) carrying mupA and blaZ, two of them co-harboring the ileS gene. Only one isolate assigned as SCCmec type III was resistant to CHX (MIC of 8.0 μg.mL^-1) and harbored the qacA gene. Resistance to chlorhexidine and mupirocin were found in isolates carrying qacA and mupA in our hospital. Since these genes are plasmid-mediated, this finding draws attention to the potential spread of resistance to mupirocin in our hospital.

Deriving a parsimonious cardiac endpoint for use in epidemiological studies of Chagas disease: results from the Retrovirus Epidemiology Donor Study-II (REDS-II) cohort

Chagas cardiomyopathy (ChCM) is a severe consequence of Trypanosoma cruzi infection and has a range of electrocardiographic (ECG) and echocardiographic (ECHO) manifestations. There is a need for a standard and parsimonious research cardiac end point that does not rely on expert panel adjudication, and it is not intended to change the ChCM definition. We use data from the REDS-II cohort to propose a simplified cardiac endpoint. A total of 499 T. cruzi-seropositive blood donors were included. All participants underwent a 12-lead ECG, echocardiogram and clinical examination, and those with abnormal findings were reviewed by a panel of cardiologists who classified cases as having Chagas cardiomyopathy or not. We created an exhaustive set of ECG and ECHO finding combinations and compared these with the panel's classification. We selected the simplest combination that most accurately reproduced the panel's results. Individual ECG and ECHO variables had low sensitivity for panel-defined cardiomyopathy. The best performing combination was right bundle branch block and/or ECHO evidence of left ventricular hypocontractility. This combination had 98% specificity and 85% sensitivity for panel-defined ChCM. It was not possible to improve the overall accuracy by addition of any other ECG or ECHO variable. Substituting right bundle branch block for the more inclusive finding of QRS interval > 120 ms produced similar results. The combination of prolonged QRS interval and/or left ventricular hypocontractility closely reproduced the REDS-II expert panel classification of Chagas ChCM. In conclusion, the simple and reproducible research endpoint proposed here captures most of the spectrum of cardiac abnormalities in Chagas disease.

Evaluating long-term MRSA colonization and household spread: Insights from a community-based study

Methicillin-Resistant Staphylococcus Aureus (MRSA) is commonly transmitted among hospitalized patients through direct contact or contaminated objects. However, the dynamics of household transmission of MRSA remain unclear, posing challenges for effective prevention. This study evaluates the persistence of MRSA colonization in asymptomatic carriers over a period of at least 17-months and examines the potential for intra-household transmission. We conducted home visits to seven families, each with at least one MRSA-colonized member, to collect nasal swabs from all household members. Phenotypic and genotypic profiles of the isolates were determined through culture, antimicrobial susceptibility testing, and PCR. We compared these new samples with previous samples from a recent study involving the same individuals to assess spontaneous clearance of MRSA. A total of 25 samples were collected, with 56 % (14) identified as S. aureus and 44 % (11) as non-S. aureus; among the S. aureus isolates, four were MRSA. We observed spontaneous clearance of MRSA in six of the original cases. Unexpectedly, there was limited intra-household transmission of MRSA, although all families with MRSA colonization had at least one member with a history of skin disease. In the family where colonization persisted, one individual had recurrent cutaneous abscesses, suggesting a possible link to sustained colonization.

Video-observed therapy (VOT) vs directly observed therapy (DOT) for tuberculosis treatment: A systematic review on adherence, cost of treatment observation, time spent observing treatment and patient satisfaction

INTRODUCTION

Tuberculosis (TB) treatment demands strict adherence to multidrug regimens. Directly Observed Therapy (DOT) poses challenges, especially regarding adherence. With the popularization of smartphones, Video-Observed Therapy (VOT) has emerged as a promising alternative, allowing healthcare providers to remotely supervise patients taking their medications via video calls.

OBJECTIVES

This systematic review critically assesses VOT's effectiveness compared to DOT, focusing on adherence, treatment costs, time spent supervising treatment, and patient satisfaction, aiming to optimize TB supervision methods worldwide.

METHODS

Only studies that met the following criteria were eligible for inclusion in the systematic review: randomized trials; studies that compared VOT to DOT; studies involving patients diagnosed with pulmonary or extrapulmonary tuberculosis; studies that reported any of the desired outcomes; full-text articles available for review; and studies conducted in the English language. We excluded studies with the following attributes: studies that lacked a control group; case series or case reports; and previous systematic reviews. The search engines and databases MEDLINE, Embase, and Cochrane were used to find studies comparing Video-Observed Therapy (VOT) to Directly Observed Therapy (DOT). The following search phrases were used to look for papers that contained them in their title or abstract: ("Electronic Directly Observed Therapy" OR "Video-observed therapy" OR "Telemedicine" OR "Wirelessly observed therapy" OR "Smartphone-enabled video-observed") AND ("TUBERCULOSIS").

RESULTS

A systematic review of the literature revealed the following findings: in all Randomized Controlled Trials (RCTs), video-observed therapy (VOT) demonstrated non-inferiority in terms of treatment adherence compared to traditional directly observed therapy (DOT); VOT reduced costs where these outcomes were assessed in the RCTs; the use of VOT reduced the amount of time healthcare professionals spent supervising treatment in RCTs evaluating this aspect; VOT contributed to higher treatment satisfaction in RCTs where this outcome was measured.

CONCLUSION

In this systematic review we emphasize the importance of Video-Observed Therapy (VOT) in the digital age for patients that have access to internet. Our findings show that VOT is comparable to DOT in terms of treatment adherence, but it is also cost-effective, improves patient satisfaction and takes less time for healthcare professionals to supervise.

Conjugative transfer of plasmid p_8N_qac(MN687830.1) carrying qacA gene from Staphylococcus aureus to Escherichia coli C600: potential mechanism for spreading chlorhexidine resistance

The methicillin resistant Staphylococcus aureus (MRSA) is recognized by its ability to acquire and transferring resistance genes through interspecies conjugative plasmids. However, transference of plasmids from Gram-positive cocci to Gram-negative bacilli is not well characterized. In this report, we describe the transfer of a conjugative plasmid carrying qacA from MRSA to Escherichia coli C600. We performed a conjugation experiment using a chlorhexidine resistant MRSA isolate (ST-105/SCCmec type III) carrying the gene qacA and qacC as the donor and a chlorhexidine susceptible E. coli C600 isolate as the receptor. Transconjugants were selected using MacConkey agar plates containing chlorhexidine in concentrations ranging from 0.25 to 16 g.L^-1. To genotypically confirm the transfer of the resistance gene, the transconjugants were screened by Polymerase Chain Reaction (PCR) and submitted to Sanger’s sequencing. MRSA isolates successfully transferred the chlorhexidine resistance gene (qacA) to the recipient E. coli strain C600. The E. coli transconjugant exhibited an important reduction of chlorhexidine susceptibility, with MICs increasing from ≤ 0.25 to ≥ 16 g.L^-1 after conjugation. The qacA gene was detected by PCR as well as in the Sanger’s sequencing analysis of DNA from transconjugant plasmids. To the best of our knowledge, this is the first report of the plasmid p_8N_qac(MN687830.1) carrying qacA and its transfer by conjugation from a MRSA to an E. coli. These findings increase concerns on the emergence of resistance dissemination across the genus and emphasizes the importance of continuous antiseptic stewardship.

Conventional endotracheal tubes versus polymer-coated tubes in ventilator-associated pneumonia development: A systematic review and meta-analysis

Introduction

Endotracheal tubes (ETT) are used in patients who require ventilatory support. Colonization of ETTs by microorganisms is associated with developing ventilator-associated pneumonia (VAP). Thus, this meta-analysis aims to compare conventional endotracheal tubes with those made using materials designed to prevent colonization.

Methods

This analysis was conducted according to the PRISMA guidelines. During May 2024, we searched multiple databases (PubMed, Cochrane and Embase) for randomized controlled trials (RCT) comparing the incidence of ventilator-associated pneumonia between conventional and coated tubes. Studies with patients with less than 48 h of intubation were excluded. Our primary endpoint was the incidence of VAP in patients intubated with either conventional or coated endotracheal tubes. Statistical analysis was performed using Review Manager Software, and a The Mantel-Haenszel test was performed using a random effects model, and risk ratios (RR) were calculated for binary outcomes. Subgroup analyses were conducted using a fixed effects model when heterogeneity was low. Risk assessment was carried out using the Risk of Bias 2 tool.

Results

Our search identified 6 RCTs eligible in our inclusion criteria, enrolling 2680 patients, with 1361 (50,78 %) undergoing intubation using a polymer-coated tube. The statistical data indicated that coated endotracheal tubes perform better in preventing pneumonia than conventional tubes (RR 0.57 Cl 95 % 0.45-0.90; p < 0.001; I2 0 %). Additionally, conventional tubes were also associated with higher bacterial colonization (47.02 CI 95 % 26.88-68.18; p < 0.01; I2 81 %) compared to coated tubes.

Conclusions

These findings indicate that utilizing a silver-coated endotracheal tube for intubation is more efficacious than conventional tubes, presenting it as a strategy to combat ventilator-associated pneumonia.