Detection Of Methicillin-resistant S. Aureus Research Articles

Seizing the Hidden Assassin: Current Detection Strategies for Staphylococcus aureus and Methicillin-Resistant S. aureus.

Staphylococcus aureus (S. aureus) is a kind of pathogenic bacteria which can lead to food poisoning, hospital, and community infections. S. aureus and methicillin-resistant S. aureus (MRSA) have become headaches for public health worldwide. Therefore, strengthening the detection of S. aureus and MRSA is a critical step to prevent and control its spread and infection. This review summarized multiple detection methods (electrochemical, optical, and other biosensors) for sensitive and efficient detection of nonresistant and resistant S. aureus. First, we have introduced the principle and methods of detection platform for S. aureus and MRSA. We also contrasted various detection strategies. Finally, the current situation and prospect of S. aureus and MRSA detection in the future are explored in depth, and its development direction of detection methods is also predicted. In this review, we found that although biosensors have shown tremendous brilliance in the field of monitoring, they are currently in the experimental stage. It can be certain that we are very close to entering the commercialization stage. The point-of care testing available to nonprofessionals will become a new direction. We firmly believe that the monitoring system will be more perfect and stable and public life will be healthier and safer.

A novel extraction-free dual HiFi-LAMP assay for detection of methicillin-sensitive and methicillin-resistant Staphylococcus aureus.

Staphylococcus aureus (S. aureus) is a leading cause of bacteremia and blood stream infections. Methicillin-resistant S. aureus (MRSA) that first appeared in 1961 often caused hospital-acquired infections (HAIs) and community-acquired infections (CAIs) and was associated with high mortality rate. Accurate and rapid point-of-care testing (POCT) of MRSA is crucial for clinical management and treatment of MRSA infections, as well as the prevention and control of HAIs and CAIs. Here, we reported a novel extraction-free dual HiFi-LAMP assay for discriminative detection of methicillin-susceptible S. aureus and MRSA. The dual HiFi-LAMP assay can detect 30 copies/reaction of nuc and mecA genes with detection limits of 147 and 158 copies per 25 µL reaction, respectively. A retrospective clinical evaluation with 107 clinical S. aureus isolates showed both sensitivity and specificity of 100%. A prospective clinical evaluation with 35 clinical samples revealed a specificity of 100% and a sensitivity of 92.3%. The dual HiFi-LAMP assay can detect almost all S. aureus samples (141/142; 99.3%) within 20 min, implying that the entire HiFi-LAMP assay (including sample process) can be completed within 40 min, extremely significantly shorter than 3-5 days by the traditional clinical microbial culture and antibiotic susceptibility testing. The novel extraction-free dual HiFi-LAMP assay can be used as a robust POCT tool to promote precise diagnosis and treatment of MRSA infections in hospitals and to facilitate surveillance of MRSA at hospital and community settings.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) was associated with high mortality rate and listed as a "priority pathogen" by the World Health Organization. Accurate and rapid point-of-care testing (POCT) of MRSA is critically required for clinical management and treatment of MRSA infections. Some previous LAMP-based POCT assays for MRSA might be questionable due to their low specificity and the lack of appropriate evaluation directly using clinical samples. Furthermore, they are relatively tedious and time-consuming because they require DNA extraction and lack multiplex detection capacity. Here, we reported a novel extraction-free dual HiFi-LAMP assay for discriminative detection of MRSA and methicillin-susceptible S. aureus. The assay has high specificity and sensitivity and can be completed within 40 min. Clinical evaluation with real clinical samples and clinical isolates showed excellent performance with 100% specificity and 92.3%-100% sensitivity. The novel extraction-free assay may be a robust POCT tool to promote precise diagnosis of MRSA infections and facilitate surveillance of MRSA at hospital and community settings.

Development of fluorescence-linked immunosorbent assay for rapid detection of Staphylococcus aureus.

Staphylococcus aureus is a major pathogen that causes infections and life-threatening diseases. Although antibiotics, such as methicillin, have been used, methicillin-resistant S. aureus (MRSA) causes high morbidity and mortality rates, and conventional detection methods are difficult to be used because of time-consuming process. To control the spread of S. aureus, a development of a rapid and simple detection method is required. In this study, we generated a fluorescent anti-S. aureus antibody, and established a novel fluorescence-linked immunosorbent assay (FLISA)-based S. aureus detection method. The method showed high sensitivity and low limit of detection toward MRSA detection. The assay time for FLISA was 5h, which was faster than that of conventional enzyme-linked immunosorbent assay (ELISA) or rapid ELISA. Moreover, the FLISA-based detection method was applied to diagnose clinically isolated MRSA samples that required only 5.3h of preincubation. The FLISA method developed in this study can be widely applied as a useful tool for convenient S. aureus detection. KEY POINTS: • A fluorescence-linked immunosorbent assay-based S. aureus detection method • Simultaneous quantification of a maximum of 96 samples within 5h • Application of the novel system to diagnosis clinical isolates.

Variations In The Genotypic And Phenotypic Characteristics Of Methicillin-Resistant Staphylococcus Aureus (Mrsa) From Students Attending Poultry Farms In Umuahia, Abia State, Nigeria

Staphylococcus aureus causes significant epidemiologic and therapeutic challenges with various skin and soft tissue infections, the main forms of disease manifestation. The public health importance of this organism has been heightened by the emergence and spread of species that are resistant to treatment usually referred to as methicillin-resistant S. aureus (MRSA). This study was carried out to detect mecA and mecC genes in phenotypically determined MRSA isolates. Nasal swab samples of the subjects were cultured on mannitol salt agar and the isolates were identified as S. aureus using a combined morphological and biochemical characteristic. Antibiotic susceptibility profile was performed using the disk diffusion susceptibility method whilst phenotypic detection of MRSA isolates was by Cefoxitin disk diffusion method as per CLSI guidelines. Genomic DNA was extracted from the isolates using commercial kits. The extracted DNA was subjected to multiplex PCR to amplify the 163-bp and 188-bp fragment of the mecA and mecC genes respectively in a Pielter thermal cycler. The susceptibility pattern of MRSA isolates showed that the organisms were highly resistant to Augmentin 29 (93.5%), ceftazidime 18 (58.1%), Streptomycin 19 (76%) whilst high levels of susceptibility were seen for Ofloxacin 27 (87.1%), Levofloxacin 28 (90.3%), and Gentamicin 24 (77.4%). The antibiotic resistance profiles in MRSA isolates were recorded as follows: ciprofloxacin 6 (16.2%), Augmentin 32 (86.4%), erythromycin 13 (35.1%), Ceftazidime 22 (59.4%). Of the 10 MRSA isolates that were subjected to PCR, one isolate was found to harbor the 188-bp of mecC gene whilst mecA was absent from the screened isolates. The detection of mecC MRSA in the present study highlights the diagnostic importance of screening for mecC in mecA negative MRSA. We suggest that surveillance for MRSA should include screening for mecC gene where mecA is not detected in resistant isolates. Stamford Journal of Microbiology, 2023. Vol. 13, Issue 1, p. 6-10

Prospective Evaluation of the BD MAX StaphSR Assay for the Screening of Methicillin-Susceptible and -Resistant Staphylococcus aureus from Nasal Swabs Taken in Intensive Care Unit Patients.

Screening patients for S. aureus nasal carriage has proved effective in preventing cross-contamination and endogenous infection with this bacterium. The aim of this study was to assess the performance of the BD MAX StaphSR assay with liquid Amies elution swabs, taken during routine care of intensive care unit patients. Direct and pre-enriched cultures were used as reference methods to screen for S. aureus and methicillin-resistant S. aureus (MRSA). Discrepant results between the BD MAX StaphSR assay and cultures were resolved by using the Xpert SA Nasal Complete assay. A total of 607 nasal swabs taken from 409 patients were included in this study. Compared to culture methods, the sensitivity and specificity of the BD MAX StaphSR assay were 92.5% and 91.7% for S. aureus screening, and 94.7% and 98.3% for MRSA screening, respectively. In 52 (8.6%) specimens, there was a discrepancy between the results of cultures and the BD MAX StaphSR assay, including 13 (25%) where the results of the BD MAX StaphSR assay were confirmed by the Xpert SA Nasal Complete test. This prospective study showed that the BD MAX StaphSR assay is reliable for S. aureus and MRSA detection from nasal samples taken with liquid Amies elution swabs.

Rapid and duplex detection of MRSA using SERS-based molecular beacons

The presence of the mecA gene and penicillin-binding protein 2a (PBP2a) plays an important role in the antibiotic resistance of methicillin-resistant S. aureus (MRSA). We have developed a method for duplex detection of transmembrane PBP2a expression and the mecA gene using the plasmonic decay properties of Surface-enhanced Raman scattering (SERS) and the unique properties of beacon molecules. The duplex SERS-based test was more specific, sensitive, and rapid than polymerase chain reaction for genetic materials or ELISA for PBP2a expression, and it has a limit of detection that can detect as little as 27 PBP2a-expressed S. aureus and 8.5 pM of mecA. The efficacy of the duplexing test was demonstrated by the observed receiver operating characteristics (ROC) with its area under the curve (AUC) of 0.92 for MRSA-spiked samples. Additionally, the sensor can be developed and integrated with a portable Raman system for on-site detections.

Molecular Detection of mecA gene among Methicillin Resistant Staphylococcus aureus Isolates from Clinical Samples in Sokoto, Nigeria

Methicillin-resistant S. aureus (MRSA) infections have become a common problem in hospital and community-acquired infections. This study was aimed at detecting the presence of mecA gene among Methicillin Resistant Staphylococcus aureus Isolates from clinical samples obtained from 2 major hospitals in Sokoto, Northwestern Nigeria. A total of 95 non duplicate isolates were screened for confirmation using standard microbiological techniques. Antibiotic sensitivity testing was carried out by disc diffusion using Cefoxitin and resistant isolates were tested with different other antibiotics. All MRSA isolates were subjected to molecular analysis by detection of mecA gene based on PCR technique. Showed that, 42/95 (44.2%) were methicillin resistant. The most potent antibiotic was quinupristin/dalfopristin with 83.3% sensitivity followed by rifampicin with 81.0% and clindamycin with a 71.4%. The least activity was shown to be in fluoroquinolone antibiotic ciprofloxacin with 78.6% of the isolates demonstrating resistance followed by, tetracycline and gentamycin with 64.3%, 61.9% and 61.9% respectively. Most of the MRSA isolates were resistant to more than three antibiotics.PCR showed 36(85.7%) harbored the mecA gene. Although, polymerase chain reaction is the gold standard for determining Methicillin resistance through the detection of the mecA gene, the present study phenotypically established the presence of methicillin resistant S. aureus isolates that are mecA negative. Therefore, interpretation of MRSA detection strictly based on mecA detection should be done with care in the study area.

Prevalence and antimicrobial susceptibility pattern of methicillin-resistant Staphylococcus aureus isolates from retail raw meats in Turkey

The transmission of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) through food products of animal origin may pose a public health concern. Therefore, the objectives of the present work were to determine the prevalence of S. aureus and MRSA in raw meat samples (beef, chicken, turkey, and duck) at retail level, and to determine the antimicrobial resistance profile of the MRSA isolates. Between September 2018 and January 2019, a total of 325 raw meat samples were collected from retail stores, and analysed for the presence of S. aureus and MRSA using primary enrichment method as well as using secondary selective enrichment methods for MRSA detection. All the suspected S. aureus and MRSA colonies obtained from the samples were confirmed by both phenotypic and genotypic methods. The MRSA isolates were tested against various antimicrobials, and the minimal inhibitory concentration (MIC) of vancomycin was determined. Macrolide-lincosamide-streptogramin B (MLSB) resistance phenotypes were also screened using the double-disk diffusion test. The overall prevalence of S. aureus was 57.2%, whereas the food-specific prevalence in beef, turkey, duck, and chicken samples was 75, 53, 48, and 46%, respectively. The overall prevalence of MRSA was 1.2%, whereas it was 3, 1, 0, and 0% in beef, turkey, chicken, and duck samples, respectively. All MRSA isolates were detected by the secondary selective enrichment method. These MRSA isolates had a variety of MLSB resistance phenotypes (i.e., iMLSB, cMLSB, and MS-MLSB) with vancomycin MIC values ranging between 1 - 2 µg/mL. These findings are important for developing interventions to reduce raw meat contamination with S. aureus and MRSA, and to improve public health.

Rapid detection of methicillin-resistant Staphylococcus aureus in positive blood-cultures by recombinase polymerase amplification combined with lateral flow strip.

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is an important bacterium that causes community and healthcare-related infections throughout the world. However, the current conventional detection methods are time-consuming. We therefore developed and evaluated a recombinase polymerase amplification-lateral flow strip (RPA-LF) approach for detection of MRSA in positive blood-culture samples. Sixty positive blood-cultures from a hospital were tested directly without DNA extraction and purification before the amplification reaction. RPA primers and probes were designed for nuc (encoding thermonuclease) and mecA (encoding penicillin-binding protein 2a) genes to diagnose S. aureus and its methicillin-resistance status. The RPA reaction occurred under isothermal conditions (45°C) within 20 min and a result was provided by the LF strip in a further 5 min at room temperature. The evaluation of RPA-LF using blood-culture samples showed 93.3% (14/15) sensitivity for identifying S. aureus, and no cross-amplification was seen [100% (45/45) specificity]. For detection of methicillin resistance, the RPA-LF test provided 100% (16/16) sensitivity and 97.7% (43/44) specificity. The RPA-LF is rapid, highly sensitive, robust and easy to use. It can be used for direct detection of MRSA with no requirement for special equipment.

Association of PVL Gene in MSSA and MRSA Strains among Diabetic Ulcer Patients from Odisha, India.

Staphylococcus aureus has emerged as an important pathogen among diabetic foot ulcers in patients with diabetes. Infections with S. aureus in diabetic ulcers need surveillance of resistant microbial profile to provide the basis for empirical therapy for the reduction of lower extremities amputation. Panton valentine leucocidin (PVL) is considered as one of the major virulence gene of S. aureus which is responsible for destruction of white blood cells and tissue necrosis. This pore forming cytotoxin gene is carried out by both methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains. The present study described the prevalence of PVL gene in MSSA and MRSA strains isolated from diabetic ulcer patients treated during November, 2019 to January, 2021 from a tertiary care hospital, Odisha. Infected tissue and blood samples from these patients were collected aseptically and sub-cultured using different media and standard techniques. The isolated genomic DNA of MSSA and MRSA strains were subjected to PCR assay for the detection of PVL gene. Two hundred ten S. aureus out of 402 diabetic ulcer patients were isolated having 59.52% MSSA and 40.47% MRSA strains. Wagner's grade III and grade IV ulcers were most prevalent in these ulcer patients. The prevalence of PVL gene in MSSA strains was more in comparison to MRSA strains. Forty five resistance patterns were observed from the antibiogram profiles of S. aureus. The present study highlighted that PVL gene could not be a marker for the detection of MRSA and MSSA strains in diabetic ulcer patients.

Recent Developments in Phenotypic and Molecular Diagnostic Methods for Antimicrobial Resistance Detection in Staphylococcus aureus: A Narrative Review

Staphylococcus aureus is an opportunistic pathogen responsible for a wide range of infections in humans, such as skin and soft tissue infections, pneumonia, food poisoning or sepsis. Historically, S. aureus was able to rapidly adapt to anti-staphylococcal antibiotics and become resistant to several classes of antibiotics. Today, methicillin-resistant S. aureus (MRSA) is a multidrug-resistant pathogen and is one of the most common bacteria responsible for hospital-acquired infections and outbreaks, in community settings as well. The rapid and accurate diagnosis of antimicrobial resistance in S. aureus is crucial to the early initiation of directed antibiotic therapy and to improve clinical outcomes for patients. In this narrative review, I provide an overview of recent phenotypic and molecular diagnostic methods for antimicrobial resistance detection in S. aureus, with a particular focus on MRSA detection. I consider methods for resistance detection in both clinical samples and isolated S. aureus cultures, along with a brief discussion of the advantages and the challenges of implementing such methods in routine diagnostics.

Detection of Heteroresistant Vancomycin-Intermediate Staphylococcus aureus among Methicillin-Resistant Staphylococcus aureus

Background: The testing of heteroresistance vancomycin-intermediate Staphylococcus aureus (hVISA) by the population analysis profile-area under the curve (PAP-AUC) is tedious and laborious. The goal of this study was to determine the prevalence of hVISA among methicillin-resistant S. aureus (MRSA) and compare two screening tests: brain heart infusion agar with vancomycin 4 mg/L (BHIV4) and macromethod E-test (MET) with PAP-AUC as the gold standard. Materials and Methods: Antibiotic sensitivity test and detection of MRSA were performed according to the CLSI guidelines. PAP-AUC, BHIV4, and MET were used to detect hVISA. Results: A total of 288 MRSA isolates were tested for hVISA, with 48 (16.66%) being detected by PAP-AUC. With PAP-AUC, BHIV4's sensitivity, specificity, positive predictive value, and negative predictive value were 70.83%, 96.66%, 80.95%, and 94.3%, respectively. The majority of hVISA isolates were found in the vancomycin minimum inhibitory concentration range 1–2 mg/L. Conclusions: hVISA was found to be 16.6% in this investigation. When compared to MET, BHIV4 had a higher sensitivity, and teicoplanin and linezolid were found to be the most effective drug against hVISA.

Phenotypic Detection of Biofilm Formation in Clinical Isolates of Methicillin-Resistant Staphylococcus aureus

Background: Staphylococcus aureus is one of the common pathogens which causes mild-to-severe diseases. Moreover, its ability to produce biofilm along with drug resistance makes it more notorious and difficult to treat; therefore, early biofilm detection can help in better management of diseases caused by methicillin-resistant S. aureus (MRSA). Materials and Methods: All clinically isolated S. aureus were screened for their antibiotic susceptibility pattern followed by MRSA status by cefoxitin disk-diffusion method. Evaluation of biofilm-producing nature of biofilm was accessed by tissue culture plate (TCP), tube adhesion (TA), and Congo red agar (CRA) methods. Results: Of all S. aureus isolates, 57% had MRSA status. TCP method showed that 68% of MRSA were biofilm producers. TA method showed 55% and CRA method showed 46% biofilm production. Conclusion: Early detection of MRSA and biofilm could be very beneficial to control S. aureus infection. Of all three biofilm detection methods, TCP method was effective in detecting biofilm, followed by TA and CRA methods.

1. The Relationship Between Chlorhexidine Skin Concentration and Multidrug-Resistant Organism (MDRO) Colonization in ICU Patients

BackgroundDaily bathing of ICU patients with chlorhexidine gluconate (CHG) is an important method for healthcare-associated infection prevention. We set out to understand the relationship between CHG concentrations and MDRO colonizationMethodsIn our trauma/surgical ICU at a large urban medical center, we performed CHG concentrations 2 days/week at 4 times points relative to CHG bathing (Medline, Northfiled, IL) application: 30 min. prior, and 30 min., 6 hrs., and 12 hrs. after application. CHG testing was done at 4 body sites: lateral neck, anterior chest, arm, and inguinal fold. On the contralateral side we tested the presence of the following 4 MDROs: methicillin resistant S. aureus (MRSA), and 3 enteric bacteria--extended spectrum beta-lactamase (ESBL)+ gram-negative rods, vancomycin resistant enterococcus (VRE), and carbapenem resistant enterobacteriaceae (CRE).ResultsWe performed testing for 256 patient-days total, of which 42 were swabbed 1 time, 38 swabbed twice, 79 swabbed 3 times, and 97 swabbed 4 times (patient movement for tests, ICU transfer were limitations). Mean CHG skin concentrations were above the MICs of pathogens at all post-CHG application time points at all body sites at all times points (Figure) and decreased during the time points after bathing. In a logistic regression model controlling for patient characteristics, MRSA detection was inversely associated with CHG concentration with an 18% increase in odds of recovery for each 2-fold decrease in CHG concentration, as well as presence of a GI device and lack of ability to sit and roll. In a logistic regression model controlling for patient characteristics, resistant enteric bacteria detection was inversely associated with CHG concentration with an 11% increase in odds of recovery for each 2-fold decrease in CHG concentration, as well as mechanical ventilation, GI device, central line, and ICU duration. ConclusionIn our large study of CHG use and its association with MDRO detection, CHG concentrations decreased during the 24 hours after application, but were typically above concentrations considered adequate to kill MDROs. CHG concentration were inversely associated with the presence of MRSA and resistant enterics, suggesting that CHG application quality is a key component of the CHG bathing process.Disclosures Loren G. Miller, MD, MPH, Medline (Grant/Research Support, Other Financial or Material Support, Contributed product) Stryker (Other Financial or Material Support, Contributed product) Xttrium (Other Financial or Material Support, Contributed product) James A. McKinnell, MD, Medline (Grant/Research Support)

Staphylococcus Aureus Bacteremia Due to Central Venous Catheter Infection: A Clinical Comparison of Infections Caused by Methicillin-Resistant and Methicillin-Susceptible Strains.

Objectives: Staphylococcus aureus bacteremia has a mortality rate of 20-40% and is mainly caused by central venous catheter (CVC) infection. We aimed to investigate differences between patients with methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) bacteremia due to CVC infection.Methods: This retrospective study, of data collected between August 2004 and March 2016 at a single Tokyo hospital, compared the clinical background characteristics, complications, and 60-day mortality rates with positive peripheral blood cultures and positive semiquantitative cultures. MRSA carrier is defined as those with a history of MRSA detection by skin, urine, or sputum culture.Results: The median ages for the 17 MRSA and 19 MSSA patients were 72 and 55 years, respectively (P < 0.01). The occurrences of baseline disease (MRSA vs. MSSA) were 59% vs. 16% (P = 0.01), respectively, while those of complications, including septic shock, were 48% vs. 16% (P = 0.07), respectively. Catheter placement duration, time from fever onset to CVC removal, and time from fever onset to antimicrobial therapy initiation were similar in both groups. Sixty-day mortality rates were 35% and 5.3% (P = 0.04) in the MRSA and MSSA groups, respectively.Conclusion: MRSA carriers and older patients were at higher risks of CVC infection than MSSA bacteremia patients. Patients with MRSA bacteremia had higher septic shock and 60-day mortality rates despite appropriate antimicrobial therapy.

Prevalence and Antimicrobial Susceptibility Profile of Staphylococcus aureus in Milk and Traditionally Processed Dairy Products in Addis Ababa, Ethiopia.

Staphylococcus aureus is a contagious pathogen that can cause various diseases in both humans and animals. Antimicrobial-resistant S. aureus is becoming an extremely important global health problem. A cross-sectional study was conducted from December 2019 to May 2020 to assess the occurrence of S. aureus and its antimicrobial susceptibility profiles in milk and traditionally processed dairy products in selected subcities of Addis Ababa. A total of 255 dairy product samples (175 raw milk and 80 traditionally processed dairy products) were collected from farms and retail markets. Samples were cultured for S. aureus according to standard microbiology techniques, and the Kirby–Bauer disk diffusion method was used to assess antimicrobial susceptibility of isolates to a panel of 12 antimicrobials. Susceptibility to methicillin was determined based on the sensitivity of isolates to cefoxitin, and resistant isolates were investigated for the presence of mecA and mecC genes using PCR. Staphylococcus aureus was isolated from 43 (24.6%) of milk, 7 (17.5%) of yogurt, and 2 (5%) of cottage cheese. A significantly higher rate of contamination with S. aureus was recorded among milk samples compared to yogurt and cottage cheese (p = 0.019). Out of 52 S. aureus isolates investigated for susceptibility to 12 antimicrobials, 49 (94.2%) of the isolates were resistant to ampicillin and 42 (80.8%) to amoxicillin+clavulanic acid. Twenty (38.5%) of the isolates were methicillin-resistant S. aureus (MRSA) based on susceptibility to cefoxitin. However, only one of these isolates (5%) was positive for mecA gene, and none of them were positive for the mecC gene. There was no significant difference (p > 0.05) in the rate of occurrence of MRSA among isolates from different sources. In conclusion, this study demonstrated a significant level of contamination of milk and dairy products with S. aureus and most isolates were multidrug resistant. The occurrence of MRSA in raw milk and dairy products signifies a serious public health threat as the practice of consuming raw dairy products in the study area is widespread. The lack of agreement between phenotypic and genotypic detection of MRSA suggests the need for further study to identify the genetic basis for the observed resistance phenotype.

Nasal Carriage of Staphylococcus aureus in Different Age Groups among Healthy School Children and its Antimicrobial Susceptibility Pattern

Introduction: Staphylococcus aureus (S.aureus) is associated with increased risk for acquiring invasive disease. There exists an increasing prevalence of resistant community acquired S.aureus infections due to the nasal colonisation of S.aureus and Methicillin-Resistant S.aureus (MRSA) worldwide. Aim: To evaluate the prevalence rate of S.aureus and MRSA nasal colonisation among healthy school children and to determine its antibiotic susceptibility rate of the S.aureus isolates. Materials and Methods: The community based cross-sectional study was conducted among 344 school going children of 5-16 years of age. Samples were obtained from the anterior nares from each child and cultured on Blood Agar (BA) and Mannitol Salt Agar (MSA). Antibiotic susceptibility pattern of S.aureus was done by Kirby-Bauer disc diffusion method. MRSA detection was done through Cefoxitin 30 μg discs along with MIC for Oxacillin and Vancomycin simultaneously according to Clinical Laboratory Standard Institute (CLSI). Results: Of the 344 children, 26 (7.55%) were found to be with nasal carriage for S.aureus of which MRSA was found to be in 12 (3.48%) isolates. S.aureus isolates exhibited resistance to multiple classes of antibiotics including Penicillin (100%), Co- trimoxazole (50%), Ciprofloxacin (15.4%), Vancomycin (7.7%), Clindamycin (7.7%), Gentamycin (7.7%). No resistance to Linezolid was observed. Conclusion: A relatively high rate of nasal carriage of S.aureus in children of age group 5-10 years was observed when compared to children of age group 11-15 years. With the risk involved transmission of infection and resistance to many classes of antibiotics among S.aureus strains exists and hence, emphasis needs to be laid to design control measures, continued surveillance and its eradication.

First report of meticillin-resistant Staphylococcus aureus harboring mecC gene in milk samples from cows with mastitis in southeastern Brazil.

MRSA infection and colonization have been reported in both companion and food-chain animals, highlighting MRSA as an important veterinary and zoonotic pathogen. Another mec allele, the mecC gene, also confers beta-lactam resistance in Staphylococcus aureus and shows 69% nucleotide identity to mecA. The main aim of this study was to investigate the genotypic and clonal profile of methicillin-resistant S. aureus (MRSA) from cows with mastitis in dairy herds. Thirty-five samples suggestive of bovine subclinical mastitis were evaluated, and S. aureus were detected in all of them using both phenotypic and molecular approaches. According to the multilocus sequence typing (MLST), the S. aureus isolates were assigned in five different STs, 21 (60%) showed ST 742, 6 (17%) ST97, 4 (11%) ST1, 2 (6%) ST30, and 2 (6%) ST126. The presence of mecA was not observed in any of these isolates whereas mecC was detected in nine of them (9/35; 26%). The Panton-Valentine leukocidin (PVL) genes were detected in a total of 4 isolates. Among the 35 isolates analyzed, 26 showed resistance to penicillin. Changes in the S. aureus epidemiology due to the detection of MRSA in milk samples from cows presenting with bovine subclinical mastitis may have consequences for public health in Brazil, challenging the empirical therapy and animal management, with potential medical and social outcomes. To the best of our knowledge, this is the first report describing mecC MRSA in Southeastern Brazil.

Bloodstream Infections Caused by S. aureus: Daptomycin Nonsusceptibility and Clinical Aspects

Background:Staphylococcus aureus is one of the leading pathogens isolated from bloodstream infections (BSIs), and vancomycin has been the main choice to treat MRSA (methicillin-resistant S. aureus) infections. Vancomycin-intermediate S. aureus (VISA) and heteroresistant-VISA (hVISA) have been described, limiting this antibiotic use. We evaluated aspects associated with the resistance and its clonality of the S. aureus isolated from BSIs, and we determined their association with clinical aspects of patients attended at Rio de Janeiro between 2016 and 2018. The detection of MRSA and trimethoprim-sulfamethoxazole resistant isolates was performed using the disk diffusion test, while the minimum inhibitory concentrations (MICs) were evaluated for 5 antimicrobials using the broth microdilution method. The MICs for ceftaroline and vancomycin of the MRSA isolates were determined using the E test. The presence of hVISA isolates was evaluated for isolates with vancomycin MICs of 1 and 2 μg/mL by screening on BHI agar added with vancomycin. The population profile was divided by the area under the curve (ie, PAP/AUC test). SCC mec was evaluated by PCR and the clonal profile by PFGE method. Among 123 S. aureus isolates from BSI, 31% were MRSA. MIC50 and MIC90 were daptomycin 2 and 2 μg/mL; linezolid, 1 and 1 μg/mL; oxacillin 1 and 256 μg mL; teicoplanin, 0.5 and 0.5 μg/mL and vancomycin 1 and 1 μg/ml. MIC values for ceftaroline and vancomycin were 0.75 and 2 μg/mL. The frequency of isolates not susceptible to daptomycin was 75%. The clonal lineages and SCCmec types found were USA100/ST5-II (50%), USA800/ST5-IV (22%), USA300/ST8-IV (15.8%), USA1100/ST30-IV (5.3%), BEC/ST239-III (5.3%), and 1 isolate carrying SCCmecV/ST1. We found 1 VISA isolate, and the PAP/AUC analysis detected 3 hVISA isolates that were associated with the USA100 and USA300 lineages. Overall, 85% of patients had a vascular catheter. More advanced age was associated with MRSA infection as was higher mortality. Patients with end-stage renal disease were more affected by MSSA infection. Daptomycin nonsusceptibility and VISA and hVISA phenotypes associated with prevalent clonal lineages were described. In addition, MRSA infections presented higher mortality, which emphasizes the importance of epidemiological studies.Funding: NoneDisclosures: None

A novel copper-based 3D porous nanocomposite for electrochemical detection and inactivation of pathogenic bacteria

An economical and reliable theranostic unit is essential for the detection and treatment of bacterial infections. MRSA is one of the most prevalent superbugs in the world at present, hence requires urgent attention. Here, we present a novel copper-based 3-D porous nanocomposite modified with vancomycin (Van) for simultaneous detection and treatment of methicillin-resistant S. aureus (MRSA). The composite contains copper/copper oxide nanoparticles which are reduced by the hydroxyl groups of β-cyclodextrin (β-CD). On addition of graphene oxide (GO), it achieves a porous structure due to π-π stacking and formation of hydrogen bonds between β-cyclodextrin (β-CD) and reduced graphene oxide sheets. Conjugation of Van to the composite provides highly specific binding towards gram-positive bacteria. Differential pulse voltammetry (DPV) was used to carry out the electrochemical detection of MRSA and achieved a very low limit of detection (LOD) 5 CFU mL−1 along with a minimum inhibitory concentration (MIC) value of 1.93 μg mL−1. The low LOD and MIC values are due to the good electrochemical response of the composite and the synergetic antibacterial effect of vancomycin and copper/copper oxide nanoparticles, respectively. The current work provides a more effective and economic unit as electrode modifier simultaneous detection and powder for the elimination of pathogenic bacteria.