scholarly journals Novel Determinants of Antibiotic Resistance: Identification of Mutated Loci in Highly Methicillin-Resistant Subpopulations of Methicillin-Resistant Staphylococcus aureus

mBio ◽  
2014 ◽  
Vol 5 (2) ◽  
Author(s):  
Janina Dordel ◽  
Choonkeun Kim ◽  
Marilyn Chung ◽  
María Pardos de la Gándara ◽  
Matthew T. J. Holden ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Chromosomal Dna ◽  
Minimum Concentration ◽  
Methicillin Resistant ◽  
Content Type ◽  
Wide Range ◽  
Intergenic Sequences ◽  
Resistance Protein ◽  
Resistant Cells

ABSTRACTWe identified mutated genes in highly resistant subpopulations of methicillin-resistantStaphylococcus aureus(MRSA) that are most likely responsible for the historic failure of the β-lactam family of antibiotics as therapeutic agents against these important pathogens. Such subpopulations are produced during growth of most clinical MRSA strains, including the four historically early MRSA isolates studied here. Chromosomal DNA was prepared from the highly resistant cells along with DNA from the majority of cells (poorly resistant cells) followed by full genome sequencing. In the highly resistant cells, mutations were identified in 3 intergenic sequences and 27 genes representing a wide range of functional categories. A common feature of these mutations appears to be their capacity to induce high-level β-lactam resistance and increased amounts of the resistance protein PBP2A in the bacteria. The observations fit a recently described model in which the ultimate controlling factor of the phenotypic expression of β-lactam resistance in MRSA is a RelA-mediated stringent response.IMPORTANCEIt has been well established that the level of antibiotic resistance (i.e., minimum concentration of a β-lactam antibiotic needed to inhibit growth) of a methicillin-resistantStaphylococcus aureus(MRSA) strain depends on the transcription and translation of the resistance protein PBP2A. Here we describe mutated loci in an additional novel set of genetic determinants that appear to be essential for the unusually high resistance levels typical of subpopulations of staphylococci that are produced with unique low frequency in most MRSA clinical isolates. We propose that mutations in these determinants can trigger induction of the stringent stress response which was recently shown to cause increased transcription/translation of the resistance protein PBP2A in parallel with the increased level of resistance.

scholarly journals Methicillin-Resistant Staphylococcus aureus in Hospitals: Latest Trends and Treatments Based on Bacteriophages

2019 ◽  
Vol 57 (12) ◽  
Author(s):  
Andrea Álvarez ◽  
Lucía Fernández ◽  
Diana Gutiérrez ◽  
Beatriz Iglesias ◽  
Ana Rodríguez ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Pathogenic Bacteria ◽  
World Health ◽  
Natural Phenomenon ◽  
Methicillin Resistant ◽  
Content Type ◽  
Wide Range ◽  
Mrsa Strains ◽  
Health Organization

ABSTRACT Even though antibiotic resistance in bacteria is a natural phenomenon, the alarming increase in pathogenic bacteria refractory to a wide range of antimicrobials is attracting attention worldwide. Indeed, the World Health Organization (WHO) has recently published a list of priority pathogens for which new antimicrobial alternatives are urgently needed. Among these pathogens, methicillin-resistant Staphylococcus aureus (MRSA) strains are perhaps the best known by the general public. In addition to its potential to acquire antibiotic resistance, S. aureus can produce a large number of virulence factors, such as hemolysins, enterotoxins, and proteases, and exhibits the ability to form biofilms as well as to evolve into different clones that can spread and colonize new environments. This review provides a brief overview of the latest options in antibacterial therapies, mainly focusing on phage therapy. In this regard, the current stage of research about antimicrobial compounds based on bacteriophages and endolysins against MRSA infections is shown and discussed.

Evaluation of antibiotic resistance pattern and mecA gene frequency in methicillin-resistant Staphylococcus aureus strains collected from clinical specimens in Marand hospital and treatment centers, Iran

2021 ◽  
Author(s):  
Abolfazl Jafari-Sales ◽  
Zahra Sadeghi Deylamdeh ◽  
Afsoon Shariat
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Meca Gene ◽  
Disk Diffusion ◽  
Diffusion Method ◽  
Disk Diffusion Method ◽  
Methicillin Resistant ◽  
Medical Centers ◽  
Wide Range

Introduction: Staphylococcus aureus causes a wide range of infections and as a multivalent pathogen is one of the causative agents of nosocomial and community infections. Therefore, the aim of this study was to identify and determine the pattern of antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients in hospitals and medical centers in Marand city and also to evaluate the presence of mecA gene. Materials and Methods: In this cross-sectional descriptive study, 385 samples of S. aureus were collected from different clinical samples of patients in hospitals and medical centers of Marand city. S. aureus was identified using standard biochemical methods.  Methicillin resistance was determined by disk diffusion method in the presence of oxacillin and cefoxitin. The pattern of antibiotic resistance of the strains was determined by disk diffusion method and according to CLSI recommendation and also PCR method was used to evaluate the frequency of MecA gene. Results: In the present study, out of 385 samples of S. aureus, 215 (55.84%) samples were methicillin resistant. PCR results for mecA gene showed that 110 samples had mecA gene.  The highest antibiotic resistance was observed against penicillin (100%) and erythromycin (83.63%). Most MRSA were isolated from urine and wound samples. Conclusion: The results of this study indicate the prevalence of methicillin-resistant species and also the increase in antibiotic resistance of MRSA to various antibiotics.  Therefore, in order to prevent increased resistance to other antibiotics, it is recommended to avoid inappropriate use of antibiotics.

scholarly journals Full-Genome Sequencing Identifies in the Genetic Background Several Determinants That Modulate the Resistance Phenotype in Methicillin-Resistant Staphylococcus aureus Strains Carrying the Novel mecC Gene

2017 ◽  
Vol 61 (3) ◽  
Author(s):  
Catarina Milheiriço ◽  
Hermínia de Lencastre ◽  
Alexander Tomasz
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Genetic Background ◽  
Beta Lactam ◽  
Methicillin Resistant ◽  
Content Type ◽  
Resistance Phenotype ◽  
Beta Lactam Antibiotics ◽  
Oxacillin Resistance ◽  
Mrsa Strains

ABSTRACT Most methicillin-resistant Staphylococcus aureus (MRSA) strains are resistant to beta-lactam antibiotics due to the presence of the mecA gene, encoding an extra penicillin-binding protein (PBP2A) that has low affinity for virtually all beta-lactam antibiotics. Recently, a new resistance determinant—the mecC gene—was identified in S. aureus isolates recovered from humans and dairy cattle. Although having typically low MICs to beta-lactam antibiotics, MRSA strains with the mecC determinant are also capable of expressing high levels of oxacillin resistance when in an optimal genetic background. In order to test the impact of extensive beta-lactam selection on the emergence of mecC-carrying strains with high levels of antibiotic resistance, we exposed the prototype mecC-carrying MRSA strain, LGA251, to increasing concentrations of oxacillin. LGA251 was able to rapidly adapt to high concentrations of oxacillin in growth medium. In such laboratory mutants with increased levels of oxacillin resistance, we identified mutations in genes with no relationship to the mecC regulatory system, indicating that the genetic background plays an important role in the establishment of the levels of oxacillin resistance. Our data also indicate that the stringent stress response plays a critical role in the beta-lactam antibiotic resistance phenotype of MRSA strains carrying the mecC determinant.

scholarly journals Evaluation of Ceftaroline, Vancomycin, Daptomycin, or Ceftaroline plus Daptomycin against Daptomycin-Nonsusceptible Methicillin-Resistant Staphylococcus aureus in anIn VitroPharmacokinetic/Pharmacodynamic Model of Simulated Endocardial Vegetations

2014 ◽  
Vol 58 (6) ◽  
pp. 3177-3181 ◽  
Author(s):  
Brian J. Werth ◽  
Katie E. Barber ◽  
Cortney E. Ireland ◽  
Michael J. Rybak
Keyword(s):  
Staphylococcus Aureus ◽  
Bactericidal Activity ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Active Agent ◽  
Minimum Concentration ◽  
Ceftaroline Fosamil ◽  
Methicillin Resistant ◽  
Content Type ◽  
Sustained Activity

ABSTRACTInfective endocarditis (IE) caused by methicillin-resistantStaphylococcus aureus(MRSA) with reduced susceptibility to vancomycin and daptomycin has few adequate therapeutic options. Ceftaroline (CPT) is bactericidal against daptomycin (DAP)-nonsusceptible (DNS) and vancomycin-intermediate MRSA, but supporting data are limited for IE. This study evaluated the activities of ceftaroline, vancomycin, daptomycin, and the combination of ceftaroline plus daptomycin against DNS MRSA in a pharmacokinetic/pharmacodynamic (PK/PD) model of simulated endocardial vegetations (SEVs). Simulations of ceftaroline-fosamil (600 mg) every 8 h (q8h) (maximum concentration of drug in serum [Cmax], 21.3 mg/liter; half-life [t1/2], 2.66 h), daptomycin (10 mg/kg of body weight/day) (Cmax, 129.7 mg/liter;t1/2, 8 h), vancomycin (1 g) q8h (minimum concentration of drug in serum [Cmin], 20 mg/liter;t1/2, 5 h), and ceftaroline plus daptomycin were evaluated against 3 clinical DNS, vancomycin-intermediate MRSA in a two-compartment,in vitro, PK/PD SEV model over 96 h with a starting inoculum of ∼8 log10CFU/g. Bactericidal activity was defined as a ≥3-log10CFU/g reduction from the starting inoculum. Therapeutic enhancement of combinations was defined as ≥2-log10CFU/g reduction over the most active agent alone. MIC values for daptomycin, vancomycin, and ceftaroline were 4 mg/liter, 4 to 8 mg/liter, and 0.5 to 1 mg/liter, respectively, for all strains. At simulated exposures, vancomycin was bacteriostatic, but daptomycin and ceftaroline were bactericidal. By 96 h, ceftaroline monotherapy offered significantly improved killing compared to other agents against one strain. The combination of DAP plus CPT demonstrated therapeutic enhancement, resulting in significantly improved killing versus either agent alone against 2/3 (67%) strains. CPT demonstrated bactericidal activity against DNS, vancomycin-intermediate MRSA at high bacterial densities. Ceftaroline plus daptomycin may offer more rapid and sustained activity against some MRSA in the setting of high-inoculum infections like IE and should also be considered.

scholarly journals Antibiotic Resistance as a Stress Response: Recovery of High-Level Oxacillin Resistance in Methicillin-Resistant Staphylococcus aureus “Auxiliary” (fem) Mutants by Induction of the Stringent Stress Response

2017 ◽  
Vol 61 (8) ◽  
Author(s):  
Choon Keun Kim ◽  
Catarina Milheiriço ◽  
Hermínia de Lencastre ◽  
Alexander Tomasz
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Stress Response ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Penicillin Binding Protein ◽  
Methicillin Resistant ◽  
Content Type ◽  
Oxacillin Resistance ◽  
Response Recovery ◽  
High Level

ABSTRACT Studies with methicillin-resistant Staphylococcus aureus (MRSA) strain COL have shown that the optimal resistance phenotype requires not only mecA but also a large number of “auxiliary genes” identified by Tn551 mutagenesis. The majority of auxiliary mutants showed greatly increased levels of oxacillin resistance when grown in the presence of sub-MICs of mupirocin, suggesting that the mechanism of reduced resistance in the auxiliary mutants involved the interruption of a stringent stress response, causing reduced production of penicillin-binding protein 2A (PBP 2A).

Comparison of Cell Sizes of Methicillin-Resistant Staphylococcus aureus with Presence and Absence of the MecA Gene

2021 ◽  
Vol 83 (1) ◽  
pp. 68-77
Author(s):  
O. Berhilevych ◽  
◽  
V. Kasianchuk ◽  
M. Kukhtyn ◽  
P. Shubin ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Cell Size ◽  
Meca Gene ◽  
Morphological Characteristics ◽  
Resistance Mechanisms ◽  
The Body ◽  
Diffusion Method ◽  
Methicillin Resistant ◽  
Wide Range

Staphylococcus aureus is a pathogenic microorganism that causes a wide range of infectious diseases of humans and animals. Staphylococcus aureus produces a large number of toxins, in particular enterotoxins, which enter the body together with food and cause disorders in the gastrointestinal tract. Moreover, S. aureus has several mechanisms of antibiotic resistance, which greatly complicates prevention of bacteria spread as community-acquired and nosocomial infections. The aim of the work was to determine and compare the differences in size of methicillin-resistant strains of S. aureus with different resistance mechanisms by scanning electron microscopy (SEM). Methods. Disc diffusion method was used to establish the mechanism of antibiotic resistance of the obtained isolates. After description of antibiotic resistant and selection of S. aureus isolates with resistance to penicillin and oxicilin, an SEM of the strains and a further comparison of their morphological characteristics, in particular cell size, with the help of Djmaizer v.5.1.10 software was carried out. Results. 54 isolates of S. aureus, obtained from various environmental objects, dairy farms and food products, were tested. PCR revealed sequences of the mecA gene, which is responsible for bacteria resistance to beta-lactams. We determined the cells size of S. aureus isolates resistant to penicillin and oxycillin and performed a comparative analysis of their morphological characteristics using SEM. Conclusions. In the course of the study, it was found that S. aureus isolates with mecA gene (mecA+) have smaller cell size than S. aureus isolates without mecA gene (mecA-).

scholarly journals Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant Staphylococcus aureus

mSystems ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Michael J. Salazar ◽  
Henrique Machado ◽  
Nicholas A. Dillon ◽  
Hannah Tsunemoto ◽  
Richard Szubin ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Resistance Mechanisms ◽  
Evolutionary Strategy ◽  
Continuous Exposure ◽  
Adaptive Laboratory Evolution ◽  
Laboratory Evolution ◽  
Methicillin Resistant ◽  
Content Type

ABSTRACT Antimicrobial susceptibility testing standards driving clinical decision-making have centered around the use of cation-adjusted Mueller-Hinton broth (CA-MHB) as the medium with the notion of supporting bacterial growth, without consideration of recapitulating the in vivo environment. However, it is increasingly recognized that various medium conditions have tremendous influence on antimicrobial activity, which in turn may have major implications on the ability of in vitro susceptibility assays to predict antibiotic activity in vivo. To elucidate differential growth optimization and antibiotic resistance mechanisms, adaptive laboratory evolution was performed in the presence or absence of the antibiotic nafcillin with methicillin-resistant Staphylococcus aureus (MRSA) TCH1516 in either (i) CA-MHB, a traditional bacteriological nutritionally rich medium, or (ii) Roswell Park Memorial Institute (RPMI), a medium more reflective of the in vivo host environment. Medium adaptation analysis showed an increase in growth rate in RPMI, but not CA-MHB, with mutations in apt, adenine phosphoribosyltransferase, and the manganese transporter subunit, mntA, occurring reproducibly in parallel replicate evolutions. The medium-adapted strains showed no virulence attenuation. Continuous exposure of medium-adapted strains to increasing concentrations of nafcillin led to medium-specific evolutionary strategies. Key reproducibly occurring mutations were specific for nafcillin adaptation in each medium type and did not confer resistance in the other medium environment. Only the vraRST operon, a regulator of membrane- and cell wall-related genes, showed mutations in both CA-MHB- and RPMI-evolved strains. Collectively, these results demonstrate the medium-specific genetic adaptive responses of MRSA and establish adaptive laboratory evolution as a platform to study clinically relevant resistance mechanisms. IMPORTANCE The ability of pathogens such as Staphylococcus aureus to evolve resistance to antibiotics used in the treatment of infections has been an important concern in the last decades. Resistant acquisition usually translates into treatment failure and puts patients at risk of unfavorable outcomes. Furthermore, the laboratory testing of antibiotic resistance does not account for the different environment the bacteria experiences within the human body, leading to results that do not translate into the clinic. In this study, we forced methicillin-resistant S. aureus to develop nafcillin resistance in two different environments, a laboratory environment and a physiologically more relevant environment. This allowed us to identify genetic changes that led to nafcillin resistance under both conditions. We concluded that not only does the environment dictate the evolutionary strategy of S. aureus to nafcillin but also that the evolutionary strategy is specific to that given environment.

scholarly journals High Prevalence of Biocide Resistance Determinants in Staphylococcus aureus Isolates from Three African Countries

2015 ◽  
Vol 60 (1) ◽  
pp. 678-681 ◽  
Author(s):  
Teresa Conceição ◽  
Céline Coelho ◽  
Hermínia de Lencastre ◽  
Marta Aires-de-Sousa
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Resistance Genes ◽  
African Countries ◽  
Methicillin Resistant ◽  
Content Type ◽  
Resistance Determinants ◽  
Biocide Resistance ◽  
High Prevalence ◽  
Very High

ABSTRACTWe assessed the prevalence of six biocide resistance genes among 82 methicillin-resistantStaphylococcus aureus(MRSA) and 219 methicillin-susceptibleS. aureus(MSSA) isolates from three African countries; the prevalence was very high forsepA(95.3%),mepA(89.4%), andnorA(86.4%), intermediate forlmrS(60.8%) andqacAB(40.5%), and low forsmr(3.7%). A significant association between biocide resistance genes and antibiotic resistance was observed, and a new cutoff MIC of ≥1 mg/liter for chlorhexidine nonsusceptibility was defined.

scholarly journals The Recombinant Bacteriophage Endolysin HY-133 ExhibitsIn VitroActivity against Different African Clonal Lineages of the Staphylococcus aureus Complex, Including Staphylococcus schweitzeri

2016 ◽  
Vol 60 (4) ◽  
pp. 2551-2553 ◽  
Author(s):  
Evgeny A. Idelevich ◽  
Frieder Schaumburg ◽  
Dennis Knaack ◽  
Anna S. Scherzinger ◽  
Wolfgang Mutter ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Bactericidal Activity ◽  
Methicillin Resistant ◽  
Content Type ◽  
Bacteriophage Endolysin ◽  
Strain Background

ABSTRACTHY-133 is a recombinant bacteriophage endolysin with bactericidal activity againstStaphylococcus aureus. Here, HY-133 showedin vitroactivity against major African methicillin-susceptible and methicillin-resistantS. aureuslineages and ceftaroline/ceftobiprole- and borderline oxacillin-resistant isolates. HY-133 was also active againstStaphylococcus schweitzeri, a recently described species of theS. aureuscomplex. The activity of HY-133 on the tested isolates (MIC50, 0.25 μg/ml; MIC90, 0.5 μg/ml; range, 0.125 to 0.5 μg/ml) was independent of the species and strain background or antibiotic resistance.

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