Vancomycin Minimum Inhibitory Concentration Research Articles

Colonization of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci and its associated factors in cancer patients at the University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia.

Cancer patients are predisposed to methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci colonization. However, the prevalence of these pathogens among cancer cases in Northwestern Ethiopia remains underreported. To determine the prevalence of colonization of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci and associated factors among cancer patients at the University of Gondar Comprehensive Specialized Hospital, Northwestern Ethiopia. A cross-sectional study enrolled 288 confirmed cancer participants through stratified systematic random sampling, gathering socio-demographic and clinical data via pretested structured questionnaires from May 1 to July 30, 2023. Each participant provided two specimens: a nasal swab and a fecal sample. Nasal swabs were collected using sterile swabs, inserted at least 1 cm into each nostril, and rotated against the nasal membrane for 10 to 15 seconds, which were then placed in Amies transport medium. Fecal specimens were collected in leak-proof plastic containers, swabbed, and transferred to Cary Blair transport medium. Nasal swabs and fecal specimens were cultured on Mannitol salt agar at 37°C for Staphylococcus aureus identification, which was confirmed by coagulase testing and Gram staining. Enterococci were cultured on Bile esculin agar at 43°C and identified at the genus level by cultural characteristics, with confirmation through Gram reaction and catalase tests. Antibiotic susceptibility was evaluated using the Kirby-Bauer disk diffusion method, with minimum inhibitory concentrations for vancomycin determined via E-test strips. To detect methicillin-resistant Staphylococcus aureus, a cefoxitin disk was used. Inducible clindamycin resistance in Staphylococcus aureus was determined by the D test. Epi-info version 7 and SPSS version 27 were used for data entry and data analysis, respectively. The Pearson Chi-Square test was initially used to evaluate the association between factors and outcomes as the preliminary analysis, with a significance threshold of p < 0.05. Variables meeting this criterion underwent bivariable and multivariable logistic regression analyses, using p-value cutoffs of < 0.2 for bivariable and < 0.05 for multivariable analyses. The study involved 288 participants, with 51.0% being men and a mean age of 45.6 years. The prevalence of methicillin-resistant Staphylococcus aureus was 11.1% (95% CI: 7.5-14.7%), while vancomycin-resistant Enterococci had a prevalence of 2.8% (95% CI: 0.9-4.7%). Inducible clindamycin-resistant Staphylococcus aureus comprised 13.5% of the isolates. The multidrug-resistant proportion of Staphylococcus aureus and Enterococci were 56.2% and 55.2%, respectively. Both organisms exhibited the highest resistance to the antibiotic classes of penicillin and tetracycline. Significant associations were identified between methicillin-resistant Staphylococcus aureus colonization and low absolute neutrophil count (AOR = 13.050, 95% CI: 1.362-125.00, P = 0.026), and between vancomycin-resistant Enterococci colonization and having undergone an invasive procedure (AOR = 8.648, 95% CI: 1.870-39.992, P = 0.006). The study reveals a significant prevalence of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci colonization among cancer patients, raising public health concerns. High antibiotic resistance rates complicate treatment and may impact patient outcomes. Notably, the high inducible clindamycin resistance report, highlights the need for D-testing. Screening for methicillin-resistant Staphylococcus aureus is recommended as an important antibiotic stewardship measure, while early detection of vancomycin-resistant Enterococci colonization is crucial to reduce complications.

Vancomycin-resistant Enterococcus – a study on its prevalence from different clinical samples in a rural medical college hospital

Background: Vancomycin-resistant Enterococcus (VRE) is an important cause of nosocomial infection with Enterococcus faecium causing most of the VRE infections. Widespread use of glycopeptides in health care facilities has led to the development of VRE and enterococcal infections with high-level resistance to aminoglycosides, beta-lactamase production and glycopeptide (including vancomycin) resistance are difficult to treat and often pose a therapeutic challenge to health care facilities. Aims and Objectives: This study aimed to determine the antibiotic susceptibility pattern of Enterococcus species from various clinical specimens and to find out the occurrence rate of vancomycin-resistant enterococci. Materials and Methods: This study was conducted at the Department of Microbiology of Tamralipto Government Medical College and Hospital, East Midnapore, West Bengal. A total of 688 clinical samples were the total sample size taken. Isolation and identification of Enterococcus spp. were done by standard microbiological procedures such as culture, Gram staining, and suitable biochemical tests were conducted. Antibiotic susceptibility testing was done by the Kirby–Bauers disc diffusion method on Mueller–Hinton agar and results were interpreted according to Clinical and Laboratory Standards Institute (CLSI) guidelines 2023. Teicoplanin sensitivity was performed for those isolates showing resistance to vancomycin. For strains showing resistance to vancomycin by the Kirby–Bauers disc diffusion method, vancomycin minimum inhibitory concentrations (MIC) were performed by E-test (Hi media) with MIC breakpoints between 4 and 32 as per CLSI criteria. This was compared with the control strain of American Type Culture Collection Enterococcus faecalis 29212 as per CLSI 2023 guidelines. Results: A total of 48 Enterococcus isolates were obtained from 688 clinical samples; 31 (8.05%) were detected from 385 urine samples, 9 (6.72%) were detected from 134 blood samples, 5 (5.15%) were detected from 97 pus/wound swab, and 3 (4.17%) were detected from 72 bronchoalveolar lavage fluid samples. Among the 48 Enterococcus isolates, 13 (27.08%) were vancomycin-resistant out of which nine were E. faecalis and four were E. faecium. Enterococcus species showed maximum resistance toward ciprofloxacin followed by ampicillin and maximum sensitivity toward teicoplanin and linezolid. Conclusion: Implementation of strict infection control measures, antimicrobial policies, and proper surveillance are required to identify, contain, and treat VRE infections to reduce mortality and morbidity.

Clinical characteristics and genomic changes of recurrent Methicillin‐Resistant Staphylococcus aureus bacteremia

BackgroundRecurrent or persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia presents significant clinical challenges. Comprehensive genomic-scale studies on the genetic changes in MRSA that correspond to refractory bacteremia are lacking. MethodFrom 2011 to 2019, MRSA blood isolates were collected from patients with persistent or recurrent bacteremia at a teaching hospital in southern Taiwan. Whole-genome sequencing (WGS) captured the genomic changes in strains responsible for refractory bacteremia, and the altered susceptibilities to specific antimicrobial agents were assessed through measurements of minimal inhibitory concentrations (MICs). ResultA total of 35 MRSA blood isolates from 15 patients with recurrent or persistent bacteremia were analyzed. Reduced susceptibilities to at least one anti-MRSA agent developed in strains from seven (46.7 %) patients. Of them, a non-synonymous mutation on a global regulator mgrA was associated with reduced daptomycin susceptibility, while an increase in vancomycin MIC was linked to mutations in genes encoding LCP family protein. A 16-fold increase in MIC to fusidic acid was connected to a mutation in the elongation factor G. These recurrent strains commonly exhibited a loss or acquisition of adhesion genes that were involved in biofilm formation, including fnbA, fnbB, and sdrD, and easG series genes of type VII secretion system. ConclusionChanges in the susceptibility of successive strains to common anti-MRSA agents were frequently observed in recurrent MRSA bacteremia. These changes were linked to modifications in genes of regulatory cascade, peptidoglycan binding, adhesion, and type VII secretion system.

MIC trends of vancomycin and teicoplanin among methicillin resistant CoNS isolates from new born blood cultures in a tertiary care centre in Southern India.

Coagulase-negative-Staphylococci (CoNS) are important etiological agent of bacteraemia in newborn babies. Methicillin resistant CoNS infections have only limited treatment options. The antimicrobial susceptibility pattern of Methicillin Resistant CoNS isolates from newborn blood cultures was studied with special reference to MICs of Vancomycin and Teicoplanin. The study population included Methicillin Resistant Coagulase Negative Staphylococcal isolates (MRCoNS) from newborn blood cultures, during a one-year period. Minimum inhibitory concentration (MIC) of Vancomycin and Teicoplanin in Methicillin resistant CoNS isolates was determined by macrobroth dilution method as per CLSI guidelines and by automated methods. Coagulase Negative Staphylococci were the etiological agent in 73.7% (n=56) cases of neonatal bacteremia. Methicillin resistance in newborn CoNS was found to be 58.9%. All the MRCoNS isolates had vancomycin and teicoplanin MICs in the susceptible range. There were MRCoNS isolates with MICs in the upper limit of susceptible range for both vancomycin and teicoplanin, which can result in poor clinical response. Continuous large scale multi-centre surveillance studies with special attention to study the MIC pattern of the high-end anti-MRSA agents like vancomycin, teicoplanin, linezolid are to be carried out. This will help the clinicians to judiciously prescribe the antibiotics, which is very essential for antimicrobial stewardship.

Prevalence and factors associated with human colonisation and vancomycin minimum inhibitory concentration of &lt;em&gt;Staphylococcus aureus&lt;/em&gt; in Colombo, Sri Lanka

Introduction: Staphylococcus aureus is known to cause a wide variety of diseases of varying severity in humans. The objectives of this study were to determine the prevalence of S. aureus and methicillin resistant S. aureus (MRSA) colonisation, assess factors associated with MRSA colonisation, identify antibiotic susceptibility patterns of MRSA isolates, determine distribution of vancomycin minimum inhibitory concentrations (MIC) of S. aureus and factors associated with high vancomycin MIC values (≥2 µg/ml). Methods: A descriptive cross sectional study was conducted among 341 participants aged 18 to 84 years selected randomly from the Colombo district from 11th December 2018 to 10th April 2019. Samples were collected from the nose, axilla, groin of participants and identification and sensitivity testing of S. aureus were performed based on standard operation procedures given in the Laboratory manual in microbiology published by the Sri Lanka College of Microbiologists (2011). Results: Prevalence of S. aureus and MRSA colonisation in the sample population was 34.6% and 13.78% respectively. All MRSA isolates were susceptible to linezolid. MRSA susceptibility to gentamicin (86%), co-trimoxazole (88 %), and chloramphenicol (80%) was high. Erythromycin had the lowest susceptibility (20%). Inducible clindamycin resistance was demonstrated in 31% of isolates. Meat consumption and consumption of antibiotics within the previous six months showed a significant association with MRSA colonisation. Vancomycin MIC of S. aureus ranged from ≤ 0.5 to 2 µg/ml. Conclusion: As prevalence of MRSA colonisation is 13.78%, more attention should be paid when managing patients with suspected S. aureus infections presenting from the community. Further research on associated factors and environmental triggers are warranted with a larger sample size and different study design to formulate national regulations and guidelines.

Presence of multiple van genes among glycopeptide non-susceptible Staphylococcus aureus exhibiting in vitro MIC creep phenomenon: A study from north-east India.

Background & objectives The global prevalence of vancomycin-resistant Staphylococcus aureus (VRSA) has increased two fold since 2010, accounting for 2.4 per cent of S. aureus infections. The emerging hVISA isolates and their increasing trends pose a serious therapeutic challenge. The present study investigated in vitro vancomycin and teicoplanin minimum inhibitory concentration (MIC) creep in S. aureus and assessed their revertants. Methods A total of 845 isolates were collected for this study, and 246 were confirmed as S. aureus. Molecular characterization of vancomycin resistance was carried out by PCR assay targeting genes types viz: vanA, vanB, vanC, vanC2/C3, vanD, vanE, and vanG. MIC was determined for vancomycin and teicoplanin by agar dilution method. MIC creep and revertant analysis were done by broth dilution method in the presence and absence of antibiotics. Results PCR assay confirmed 12 isolates were harboured vanA, followed by vanD (n=8) and vanB (n=7). The study showed 69 isolates were screened positive for glycopeptide non-susceptibility. While analyzing vancomycin MIC creep, four isolates showed a significant increase in MIC, whereas no creep phenomenon was observed for the rest. In the case of teicoplanin, seven isolates showed the MIC creep phenomenon. Revertant analysis of all the isolates that showed MIC creep phenomenon for vancomycin and teicoplanin reverted to their original MIC when the antibiotic pressure was withdrawn. Interpretation & conclusions In the present study setting, glycopeptide non-susceptibility was found in eight per cent of the isolates, and the present study found the occurrence of multiple van genes from isolates calculated from a single study center will impose a serious challenge in infection control and antibiotic policy. This study also underscores that heterogenic resistant isolates, upon exposure to vancomycin and teicoplanin at a minimum level, exhibited an increase in MIC, which will impact individuals receiving glycopeptide therapy.

Pharmacokinetic/pharmacodynamic analysis of vancomycin in patients with Enterococcus faecium bacteraemia: a retrospective cohort study

ObjectivesThe trough concentration of vancomycin and the area under the concentration–time curve (AUC)/minimum inhibitory concentration (MIC) ratio are crucial in determining vancomycin efficacy against methicillin-resistant Staphylococcus aureus. However, the use...

Unmasking a looming crisis: Escalating MIC of last resort drugs against MRSA isolates from a tertiary care hospital in Central India

PurposeThe Centers for Disease Control and Prevention has classified methicillin-resistant S aureus (MRSA) as a serious public health threat. The escalating minimum inhibitory concentration (MIC) of standard anti-methicillin-resistant S aureus (MRSA) drugs within the susceptible range, known as "MIC creep," jeopardizes their effectiveness against MRSA infections, posing additional challenges in managing MRSA infections. This cross-sectional study was conducted in a tertiary care hospital in Central India to assess the susceptibility trends of clinical MRSA isolates against commonly used anti-MRSA drugs and to observe MIC creep, if any, over three years (2020–2022). MethodsThe study included 158 non-repetitive clinical MRSA isolates. The MICs of vancomycin, teicoplanin, and linezolid were determined in MRSA strains using agar dilution, while the MIC of daptomycin was performed by broth microdilution. MIC creep was assessed by calculating MIC50, MIC90, Modal MIC, G-mean MIC, and susceptible and resistant percentages for the fiscal years 2020, 2021, and 2022. ResultsOf the 158 MRSA isolates, none were resistant to vancomycin, teicoplanin, and daptomycin, but two showed resistance to linezolid (LRSA). However, fifteen isolates showed intermediate resistance to vancomycin (VISA), and five showed intermediate resistance to teicoplanin (TISA). MIC of these anti-MRSA drugs increased in 2021 and 2022 compared to 2020. G-mean MIC for vancomycin, teicoplanin, and linezolid in MRSA strains increased significantly over the study period, while daptomycin MIC remained relatively stable, with a slight increase in 2021 and 2022. There was a high resistance rate for clindamycin, doxycycline, and chloramphenicol among VISA, TISA, and LRSA isolates compared to MRSA. ConclusionsDuring the three years of the study, “MIC creep” was observed in vancomycin, teicoplanin, and linezolid and, to some extent, for daptomycin in MRSA strains. The recovery of VISA, TISA, and linezolid-resistant MRSAs is worrisome, suggesting possible MRSA treatment failure and being a forerunner of resistant strains.

The crucial relationship between vancomycin minimum inhibitory concentration and therapeutic efficacy against methicillin-resistant coagulase-negative staphylococci

The area under the curve (AUC)/minimum inhibitory concentration (MIC) ratio was used as an indicator of the clinical efficacy of vancomycin. However, the target AUC/MIC has not been set for methicillin-resistant coagulase-negative staphylococci (MR-CNS), and the effectiveness of vancomycin in strains with high MIC is unknown. Therefore, we aimed to investigate the relationship between the vancomycin MIC and therapeutic efficacy in patients with MR-CNS bacteremia. The primary outcome was the difference in treatment failure rate when the MR-CNS vancomycin MIC was 1 or 2 µg/mL. The treatment failure rate did not significantly differ between the two groups (MIC 1 vs. MIC 2: 27.0% vs. 31.0%; p = 0.779). As a result of multivariate analysis, AUC/MIC0–24 h ≤230 was extracted as risk factor for treatment failure, suggesting the importance of a sufficient initial loading dose and early blood concentration monitoring to increase AUC/MIC0–24 h for successful treatment.

Identification of vancomycin resistance in enterococcus &amp; determination of minimal inhibitory concentration of vancomycin by E-test

Infections due to Enterococcal species is 2 prevalent cause of Nosocomial Infections in health care settings. They are crucial because to their inherent resistance to penicillins, cephalosporins, and low level aminoglycosides &amp; their tendency to develop higher level of aminoglycoside and vancomycin resistance, which leaves few therapeutic alternatives for therapy. Isolation and identification of Enterococci with their Antibiogram &amp; determination of Minimal Inhibitory Concentration (MIC) of Vancomycin by E-test. The antibiogram generated by Kirby Baur disc diffusion method and standard microbiological procedures were used to identify enterococcal isolates from distinct clinical samples. MIC level for Vancomycin was tested for all the isolates using E-test from BIOMERIEUX. Total of 108 isolates (62 E.faecalis and 46 E. faecium) were tested by E-test for MIC of Vancomycin, of which 40 (37.03%) (22 E.faecalis &amp; 18 E. faecium) were Vancomycin Resistant (VRE) strains, having MIC level &amp;#62;32 μg/ml. Nine strains out of 40 (45%) were found to have MIC &amp;#62;256 μg/ml. The enterococcal isolates were observed to be sensitive to Linezolid (80%), Ofloxacin (74%), Amoxyclav (74%) and Cefaperazone (70%). For the Indian medical community, the rise of antibiotic resistance among Enterococcal species has been a significant concern. So this is need of present era that our laboratories must be well-equipped to report the resistance patterns displayed by enterococci in order to practise evidence-based medicine and reduce hospital acquired infections.

Risk factors for vancomycin treatment failure in heterogeneous vancomycin-intermediate Staphylococcus aureus bacteremia.

The incidence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) infection is increasing and is associated with vancomycin treatment failures. However, studies investigating the risk factors for treatment failure in hVISA infection are limited. Patients with hVISA bacteremia treated with vancomycin over 7 days between August 2008 and June 2020 were enrolled in this study. Clinical and microbiological characteristics were compared between vancomycin treatment failure and success groups to identify the risk factors for vancomycin treatment failure. Among the 180 patients with hVISA bacteremia, 102 patients treated with vancomycin over 7 days were included. Vancomycin treatment failed in 80 (78%) patients. Patients in the vancomycin treatment failure group were older (P < 0.001) and more frequently had solid cancer (P = 0.04) than those in the vancomycin treatment success group. Solid organ transplantation (SOT) was more frequent (P < 0.001) in the vancomycin treatment success group. The Charlson comorbidity index (P = 0.01) and Acute Physiology and Chronic Health Evaluation II scores (P < 0.001) were higher in the vancomycin treatment failure group. In multivariate analysis, independent risk factors for vancomycin treatment failure were old age and severity of bacteremia. SOT and vancomycin minimal inhibitory concentration (MIC) ≤ 1.0 mg/L using the broth microdilution (BMD) method were associated with successful vancomycin treatment. Old age and infection severity were independent risk factors for vancomycin treatment failure. Vancomycin MIC using the BMD method is an important risk factor for vancomycin treatment failure, and its use should be considered in hVISA bacteremia.IMPORTANCEIn this study, we assessed the clinical and microbiological characteristics of heterogeneous vancomycin-intermediated Staphylococcus aureus (hVISA) bacteremia and identified risk factors for vancomycin treatment failure. We found that advanced age and severity of infection were independent risk factors for vancomycin treatment failure. On the other hand, solid organ transplantation and a low vancomycin minimal inhibitory concentration were associated with successful vancomycin treatment. This study highlights the importance of vancomycin minimal inhibitory concentration in hVISA bacteremia.

Antimicrobial susceptibility in Clostridioides difficile varies according to European region and isolate source.

Clostridioides difficile epidemiology is evolving with country-associated emerging and resistant ribotypes (RT). Antimicrobial susceptibility testing of C. difficile isolated from clinical and animal samples collected across Europe in 2018 was performed to provide antimicrobial resistance data and according to C. difficile RTs and source. Samples were cultured for C. difficile and isolates PCR ribotyped. Metronidazole, vancomycin, fidaxomicin, moxifloxacin, clindamycin, imipenem, tigecycline, linezolid, rifampicin and meropenem minimum inhibitory concentrations (MICs) for 280 clinical and 126 animal isolates were determined by Wilkins-Chalgren agar dilution. Fidaxomicin was the most active antimicrobial (all isolates geometric mean MIC = 0.03 mg/L) with no evidence of reduced susceptibility. Metronidazole MICs were elevated among RT027 (1.87 mg/L) and RT181 clinical isolates (1.03 mg/L). RT027 and RT181 had elevated geometric mean moxifloxacin MICs (14.49 mg/L, 16.88 mg/L); clindamycin (7.5 mg/L, 9.1 mg/L) and rifampicin (0.6 mg/L, 21.5 mg/L). Five isolates (RT002, RT010 and RT016) were metronidazole resistant (MIC = 8 mg/L) and 10 (RT027; RT198) had intermediate resistance (4 mg/L). Metronidazole MICs were not elevated in animal isolates. Increased geometric mean vancomycin MICs were observed among RT078, mostly isolated from animals, but there was no resistance (MIC ≥ 4 mg/L). Clinical and animal isolates of multiple RTs showed resistance to moxifloxacin and clindamycin. No resistance to imipenem or meropenem was observed. Increased antimicrobial resistance was detected in eastern Europe and mostly associated with RT027 and related emerging RT181, while clinical isolates from northern and western Europe had the lowest general levels of resistance.

Phytotherapeutic potential against MRSA: mechanisms, synergy, and therapeutic prospects

BackgroundRising resistance to antimicrobials, particularly in the case of methicillin-resistant Staphylococcus aureus (MRSA), represents a formidable global health challenge. Consequently, it is imperative to develop new antimicrobial solutions. This study evaluated 68 Chinese medicinal plants renowned for their historical applications in treating infectious diseases.MethodsThe antimicrobial efficacy of medicinal plants were evaluated by determining their minimum inhibitory concentration (MIC) against MRSA. Safety profiles were assessed on human colorectal adenocarcinoma (Caco-2) and hepatocellular carcinoma (HepG2) cells. Mechanistic insights were obtained through fluorescence and transmission electron microscopy (FM and TEM). Synergistic effects with vancomycin were investigated using the Fractional Inhibitory Concentration Index (FICI).ResultsRheum palmatum L., Arctium lappa L. and Paeonia suffructicosaas Andr. have emerged as potential candidates with potent anti-MRSA properties, with an impressive low MIC of 7.8 µg/mL, comparable to the 2 µg/mL MIC of vancomycin served as the antibiotic control. Crucially, these candidates demonstrated significant safety profiles when evaluated on Caco-2 and HepG2 cells. Even at 16 times the MIC, the cell viability ranged from 83.3% to 95.7%, highlighting their potential safety. FM and TEM revealed a diverse array of actions against MRSA, such as disrupting the cell wall and membrane, interference with nucleoids, and inducing morphological alterations resembling pseudo-multicellular structures in MRSA. Additionally, the synergy between vancomycin and these three plant extracts was evident against MRSA (FICI < 0.5). Notably, aqueous extract of R. palmatum at 1/4 MIC significantly reduced the vancomycin MIC from 2 µg/mL to 0.03 µg/mL, making a remarkable 67-fold decrease.ConclusionsThis study unveil new insights into the mechanistic actions and pleiotropic antibacterial effectiveness of these medicinal plants against resistant bacteria, providing robust evidence for their potential use as standalone or in conjunction with antibiotics, to effectively combat antimicrobial resistance, particularly against MRSA.

Phenotypic and genotypic characteristics of mecA - positive oxacillin-sensitive Staphylococcus aureus isolated from patients with bloodstream infection in a tertiary hospital in Southern Brazil.

Staphylococcus aureus are extremely important microorganisms, either from an epidemiological point of view or as a pathogen, responsible for causing a series of infectious processes, whether simple, restricted to the skin, or invasive infections such as bacteremia. The emergence of Oxacillin Sensitive-Methicillin Resistant S.aureus (OS-MRSA) isolates has imposed difficulties in the treatment of patients with staphylococcal infection, as such isolates can be mistakenly classified as sensitive and lead to failure of the therapy used. Thus, the objective of this study is to evaluate the prevalence, and genotypic and phenotypic characteristics, of OS-MRSA isolates, from bloodstream infections, collected from patients admitted to a hospital in southern Brazil, as well as to evaluate the treatment used. For this, 801 unique isolates of S. aureus, collected from blood cultures, between January 2011 and December 2020 were evaluated. Of these, 96 isolates were classified as sensitive to oxacillin. The isolates were identified and had their sensitivity profile performed by manual and automated methods. The minimum inhibitory concentration for vancomycin, daptomycin, oxacillin, linezolid and teicoplanine was performed by e-test. The mecA, vanA genes, typing of the SCCmec elements, as well as the search for the icaA, tst-1 and pvl virulence genes were performed by PCR. Biofilm formation was performed using the crystal violet technique. The Sequence Type (ST), as well as the Clonal Complex (CC) of the isolates was evaluated by the RTq -PCR. The clinical characteristics of the patients were evaluated through an active search in medical records. After investigating the mecA gene, 27.1% (26/96) of the isolates were considered OS-MRSA, with SCCmec type I being the most prevalent, 46.1% (12/26). Among the evaluated isolates, 41% (9/22) were included in CC5 and ST9. As for virulence, all isolates were positive for the icaA gene and characterized as strong biofilm formers. The pvl gene was found in 92.3% (24/26) of the isolates and the toxic shock syndrome toxin was present in 61.5% of the isolates (16/26). All isolates were negative for the presence of the van A gene. As for the clinical outcome, 73% (19/26) of the patients were discharged from the hospital and 27% (7/26) died. It was possible to observe a high frequency of OS-MRSA isolates causing bloodstream infections. Furthermore, such isolates contain several virulence genes, which may contribute to a worse clinical outcome.

Repeated Exposure of Vancomycin to Vancomycin-Susceptible Staphylococcus aureus(VSSA) Parent Emerged VISA and VRSA Strains with Enhanced Virulence Potentials.

The emergence of resistance against the last-resort antibiotic vancomycin in staphylococcal infections is a serious concern for human health. Although various drug-resistant pathogens of diverse genetic backgrounds show higher virulence potential, the underlying mechanism behind this is not yet clear due to variability in their genetic dispositions. In this study, we investigated the correlation between resistance and virulence in adaptively evolved isogenic strains. The vancomycin-susceptible Staphylococcus aureus USA300 was exposed to various concentrations of vancomycin repeatedly as a mimic of the clinical regimen to obtain mutation(s)-accrued-clonally-selected (MACS) strains. The phenotypic analyses followed by expression of the representative genes responsible for virulence and resistance of MACS strains were investigated. MACS strains obtained under 2 and 8µg/ml vancomycin, named Van2 and Van8, respectively; showed enhanced vancomycin minimal inhibitory concentrations (MIC) to 4 and 16µg/ml, respectively. The cell adhesion and invasion of MACS strains increased in proportion to their MICs. The correlation between resistance and virulence potential was partially explained by the differential expression of genes known to be involved in both virulence and resistance in MACS strains compared to parent S. aureus USA300. Repeated treatment of vancomycin against vancomycin-susceptible S. aureus (VSSA) leads to the emergence of vancomycin-resistant strains with variable levels of enhanced virulence potentials.

Comparison of the Areas Under the Curve of Vancomycin Continuous vs. Intermittent Infusion in Critically Ill Pediatrics: A Randomized Clinical Trial.

Providing data on the superior efficacy of vancomycin administered based on the area under the curve over 24 hours to the minimum inhibitory concentration of vancomycin (AUC24/MIC) is crucial. However, data on dosing and monitoring of vancomycin pharmacokinetics in the pediatric population are limited. Previous findings have showed that intermittent infusion of vancomycin (IIV) may not achieve the desired levels, continous infusions of vancomycin (CIV) reach the desired serum concentration faster than IIV and are associated with reduced nephrotoxicity. This study aimed to compare the serum concentrations, AUC24, clinical variables, and adverse effects of two vancomycin administration methods in the pediatric population. This study was a double-blind, randomized, controlled clinical trial conducted at a tertiary children's teaching hospital. Inclusion criteria were age between 2 months and 15 years and weight less than 67 kilograms, with exclusion criteria including renal impairment. Participants were divided into CIV and IIV groups following distinct administration protocols. Demographic, clinical, and laboratory data, including vancomycin serum concentrations, were compiled. Assessments included pediatric mortality risk, pediatric sequential organ failure assessment, and regular temperature monitoring. Pharmacokinetic analysis was conducted using Monolix software 2023R1. Primary endpoints were vancomycin serum levels and AUC24 between cohorts on day three, with nephrotoxicity and additional adverse drug responses evaluated. Sixty-eight patients in the pediatric intensive care unit (PICU) were allocated to either CIV (33) or IIV (35) for vancomycin treatment. In the CIV group, 82% of patients achieved an AUC24 ≥ 400 mg.h/L, compared to 23% in the IIV group. Continuous infusions of vancomycin demonstrated a greater AUC24 (587.7 ± 184.4 mg.h/L vs. 361.9 ± 113.2 mg.h/L, P < 0.05) compared to IIV. Two cases of nephrotoxicity were reported, one in each group, with mortality and adverse events being comparable between the two groups. This study demonstrated that continuous vancomycin infusion has a higher success rate in safely achieving therapeutic vancomycin levels in PICU patients compared to intermittent vancomycin infusion.

Silencing of Resistance Mechanism in Vancomycin-Resistance Enterococci Using Antisense RNA of vanA Gene

The World Health Organization has included the problem of antibiotic resistance among the top 10 important health problems in the world. Treatment of infectious diseases has become more difficult due to the spread of antibiotic resistance between bacteria via transposable elements. Vancomycin-resistant enterococci (VRE) are of critical medical and public health importance due to their association with serious nosocomial infections and high risk of death. One of the most important features of VREs is that they have multiple antibiotic resistance and treatment options are reduced. Therefore, new treatment methods are needed. The vanA gene constitutes the building block of the vancomycin resistance mechanism and causes high resistance to vancomycin. In this study, it was aimed to investigate the neutralization of the vancomycin resistance mechanism by creating vanA antisense RNA (asRNA). The vanA positive VRE50 strain in our culture collection which was isolated from the clinical sample, was used to amplify the vanA gene by polymerase chain reaction (PCR). The amplified vanA amplicon was inserted inversely into the pUC19 plasmid by means of the enzyme cutting sites in the primers used. The resulting plasmid was combined with the pAT392 plasmid which can replicate in gram-positive bacteria and a fusion plasmid was created. The fusion plasmid whose orientation was confirmed, was transferred to the wild strain VRE50 by electroporation method. Minimum inhibitory concentration (MIC) values of transformed VRE (tVRE50) and wild type VRE50 strains used as control were determined by the E-Test method. The vancomycin MIC value of the wild type VRE50 strain was determined as 1024 µg/mL and that of the tVRE50 strain was 32 µg/mL and it was determined that the vancomycin resistance of the tVRE50 strain decreased with asRNA (antisense RNA). Antisense RNA technology is an important method for neutralizing the expression of genes. This study showed that neutralization of the vancomycin resistance gene may provide a lower MIC value in a vancomycin-resistant enterococcus strain and lead to increased susceptibility. This new approach provides a new method for VRE treatment by neutralizing the vancomycin resistance mechanism. The result obtained in this study needs to be supported by in vivo tests.

Association of Vancomycin AUC/MIC and Trough Concentration With Early Clinical Response in Enterococcus or Coagulase-Negative Staphylococcus Infection: A Prospective Study.

This study was condcuted to examine the association of area under the curve (AUC)/minimum inhibitory concentration (MIC) and trough concentration (Ctrough) of vancomycin with treatment outcome and nephrotoxicity in infections caused by Enterococcus spp. and coagulase-negative Staphylococci (CoNS). Peak and trough concentrations were used to calculate AUC in 89 patients receiving vancomycin for infections with Enterococcus spp. (n = 65) or CoNS (n = 24). Correlations between Ctrough,AUC/MIC, early clinical response (ECR), and nephrotoxicity were assessed and cutoff values were determined. Sixty-three (70.8%) patients showed improvement in ECR and 10 (11.2%) experienced nephrotoxicity. Enterococcus spp. infections displayed correlations between AUC/MIC and ECR for AUC0-24 h/MIC (r2 = 0.27, P ≤ .05) and AUC24-48 h/MIC (r2 = 0.28, P ≤ .05), but not for Ctrough (r2 = 0.21, P > .05). There were no correlations between Ctrough (r2 = 0.26, P > .05), AUC0-24 h/MIC (r2 = -0.12, P > .05), AUC24-48 h/MIC (r2 = 0.01, P > .05) and ECR for CoNS. In the CoNS group, a moderate correlation was found between ECR and Ctrough at a cutoff value of 6.9 μg/mL. In addition, nephrotoxicity is also moderately associated with AUC0-24 h and AUC24-48 h at 505.7 and 667.1 μg•h/mL, respectively. A strong correlation between nephrotoxicity and Ctrough was observed when the cutoff value was 18.9 μg/mL. AUC/MIC during the first 48 h was a determinant of vancomycin efficacy in Enterococcus infections but not for CoNS. Ctrough was not correlated with clinical outcome. Nephrotoxicity could be predicted using Ctrough and AUC for infections with both pathogens.

Comparison of broth microdilution and E-test for susceptibility of MRSA to vancomycin

Introduction: Healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) developed soon after the introduction of methicillin. These bacteria have shown resistance to multiple drugs and therefore vancomycin became the antibiotic of choice for treatment of MRSA infections. Vancomycin is a bactericidal antibiotic that acts by inhibiting bacterial cell wall synthesis. This study aimed to compare broth microdilution (BMD) and E-test in determining vancomycin minimum inhibitory concentration (MIC) against MRSA.Methods: A total of 30 clinical isolates of MRSA were acquired from Colombo South Teaching Hospital, Sri Lanka. These MRSA strains were identified by cefoxitin disk diffusion and the vancomycin MIC was determined through BMD and E-test. The Kruskal-Wallis test was applied to test if the samples originated from the same distribution with post hoc determination of the correlation between methods using the Mann-Whitney U test.Results: All 30 MRSA isolates were 100% vancomycin susceptible (≤2 μg/mL) irrespective of methodology, according to the Clinical and Laboratory Standards Institute (CLSI) established breakpoints. However, the E-test MIC values were 1 to 2 dilutions higher than those of BMD. A statistically significant difference between vancomycin MICs of BMD and E-test (p = &lt;0.00001) was calculated which indicated a difference in accuracy.Conclusion: Due to cost, convenience, and the ability to detect vancomycin intermediate Staphylococcus aureus (VISA), exploring the possibility of using E-test as an alternative to BMD is worthwhile.

Study of the sensitivity of methicillin-resistant &lt;i&gt;Staphylococcus aureus&lt;/i&gt; to antibiotics and bacteriophage preparations

Objective. To evaluate the sensitivity of methicillin-resistant Staphylococcus aureus strains to antibiotics and therapeutic and prophylactic preparations of bacteriophages. Materials and methods. The antibiotic sensitivity of strains of methicillin-resistant S.aureus was studied by the disco-diffusion method, the determination of the minimum inhibitory concentrations of vancomycin and linezolid by broth microdilution method, and ceftaroline by E-tests. The sensitivity of methicillin-resistant S.aureus to bacteriophage preparations was studied. Results. It has been established that linezolid and vancomycin are quite active drugs against methicillin-resistant S.aureus (MRSA), however, resistance to them begins to develop. MRSA resistance to fluoroquinolones and cefoxitin was the highest of all antibiotics tested; the results obtained with cefoxitin can be interpreted for other cephalosporins (except ceftaroline) and all penicillins. Only 67.9% of MRSA strains retained sensitivity to ceftaroline, but ceftaroline-resistant strains had low levels of minimal inhibitory concentration. The preparations of the bacteriophages “Sextaphage” and “Piobacteriophage Phagio” showed their lytic activity only in relation to 35.8% and 18.9% of MRSA isolates, respectively. Conclusion. Monitoring the development of antibiotic resistance in methicillin-resistant S.aureus is an important part of the strategy of rational antibiotic therapy for staphylococcal infections. Only taking into account the preliminary step-by-step determination of the phage sensitivity of the causative agent of the disease, bacteriophage preparations can be considered as a completely possible alternative to antibiotics for the treatment of purulent inflammatory diseases caused by MRSA.