Susceptibility of clinical isolates of Staphylococcus aureus to killing by oxacillin

1975 ◽  
Vol 21 (11) ◽  
pp. 1692-1697 ◽  
Author(s):  
Gary K. Best ◽  
Ann V. Koval ◽  
Norma H. Best
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Rate ◽  
Cell Wall ◽  
Minimal Inhibitory Concentration ◽  
Inhibitory Concentration ◽  
Bactericidal Effect ◽  
Clinical Isolates ◽  
Cell Wall Synthesis ◽  
Abnormal Growth ◽  
Killing Action

Sixty clinical isolates of Staphylococcus aureus have been screened for their relative susceptibility to the killing action of oxacillin. Only one of these strains was found to be exceptionally resistant to the bactericidal effect of this and other β-lactam antibiotics. This ability to survive oxacillin inhibition of cell wall synthesis has been called "tolerance." The characteristics of the tolerant organism, which has been designated the Evans strain, in comparison with other isolates of S. aureus indicate that this form of resistance is not apparent from the minimal inhibitory concentration, is not related to an abnormal growth rate, and can be enhanced by treatment with N-methyl-N′-nitro-N-nitrosoguanidine.

scholarly journals Reduced Triclosan Susceptibility in Methicillin-Resistant Staphylococcus epidermidis

2004 ◽  
Vol 48 (4) ◽  
pp. 1397-1399 ◽  
Author(s):  
Molly B. Schmid ◽  
Nachum Kaplan
Keyword(s):  
Staphylococcus Aureus ◽  
Minimal Inhibitory Concentration ◽  
Staphylococcus Epidermidis ◽  
Inhibitory Concentration ◽  
Clinical Isolates ◽  
Methicillin Resistant

ABSTRACT Triclosan MIC determination showed that recent Staphylococcus aureus clinical isolates (n = 100) were highly susceptible to triclosan, with a 50% minimal inhibitory concentration (MIC50) of 0.12 μg/ml and a MIC90 of 0.25 μg/ml. Staphylococcus epidermidis isolates (n = 96) were less susceptible, with a MIC50 of 0.12 μg/ml and a MIC90 of 8 μg/ml. Decreased susceptibility to triclosan was more prevalent among methicillin-resistant S. epidermidis than among methicillin-sensitive S. epidermidis isolates.

Antibiotic resistance of glycine-resistant variants of Staphylococcus aureus

1968 ◽  
Vol 14 (7) ◽  
pp. 811-812
Author(s):  
Joseph T. Parisi ◽  
William J. Suling
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Antibiotic Resistance ◽  
Cross Resistance ◽  
Cell Wall Synthesis ◽  
Minimal Inhibitory Concentrations

Glycine-resistant variants of Staphylococcus aureus were obtained by successive cultivation of parent strains in increasing concentrations of glycine, and the minimal inhibitory concentrations of glycine of the parents and variants were determined. Although it has been reported that growth in glycine or certain antibiotics causes the accumulation of nucleotides involved in cell wall synthesis, a lack of cross resistance of the variants to some of these antibiotics was observed.

scholarly journals A Staphylococcus aureus clpX Mutant Used as a Unique Screening Tool to Identify Cell Wall Synthesis Inhibitors that Reverse β-Lactam Resistance in MRSA

2021 ◽  
Vol 8 ◽  
Author(s):  
Kristoffer T. Bæk ◽  
Camilla Jensen ◽  
Maya A. Farha ◽  
Tobias K. Nielsen ◽  
Ervin Paknejadi ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
High Throughput Screening ◽  
Bacterial Infections ◽  
Screening Tool ◽  
Acquired Resistance ◽  
Teichoic Acid ◽  
Acid Synthesis ◽  
Biologically Active ◽  
Cell Wall Synthesis

Staphylococcus aureus is a leading cause of bacterial infections world-wide. Staphylococcal infections are preferentially treated with β-lactam antibiotics, however, methicillin-resistant S. aureus (MRSA) strains have acquired resistance to this superior class of antibiotics. We have developed a growth-based, high-throughput screening approach that directly identifies cell wall synthesis inhibitors capable of reversing β-lactam resistance in MRSA. The screen is based on the finding that S. aureus mutants lacking the ClpX chaperone grow very poorly at 30°C unless specific steps in teichoic acid synthesis or penicillin binding protein (PBP) activity are inhibited. This property allowed us to exploit the S. aureus clpX mutant as a unique screening tool to rapidly identify biologically active compounds that target cell wall synthesis. We tested a library of ∼50,000 small chemical compounds and searched for compounds that inhibited growth of the wild type while stimulating growth of the clpX mutant. Fifty-eight compounds met these screening criteria, and preliminary tests of 10 compounds identified seven compounds that reverse β-lactam resistance of MRSA as expected for inhibitors of teichoic acid synthesis. The hit compounds are therefore promising candidates for further development as novel combination agents to restore β-lactam efficacy against MRSA.

Antimicrobial Activity of N,N'-bis(decylmethyl)- α,ω-alkanediamine Dioxides [1]

1983 ◽  
Vol 38 (1-2) ◽  
pp. 151-152 ◽  
Author(s):  
Ferdinand Devínsky ◽  
Ivan Lacko ◽  
Ludovít Krasnec ◽  
Dušan Mlynarčík
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Antimicrobial Activity ◽  
Candida Albicans ◽  
Minimal Inhibitory Concentration ◽  
Inhibitory Concentration

Antimicrobial activity of N,N′-bis(decylmethyl)-α,ω-alkanediamine dioxides determined on Staphylococcus aureus, Escherichia coli, and Candida albicans is presented as minimal inhibitory concentration (MIC). The effect of the length of linking alkylene chain on this activity has been followed.

scholarly journals Vancomycin, linezolid and daptomycin susceptibility pattern among clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) from Sub- Himalyan Center

2018 ◽  
Vol 10 (02) ◽  
pp. 145-148 ◽  
Author(s):  
Afzal Husain ◽  
Vinita Rawat ◽  
Mukesh Kumar ◽  
Pankaj Kumar Verma ◽  
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Inhibitory Concentration ◽  
Geometric Mean ◽  
Clinical Isolates ◽  
Susceptibility Pattern ◽  
Methicillin Resistant ◽  
Therapeutic Advantage ◽  
Drug Of Choice ◽  
Alternative Agent

ABSTRACT INTRODUCTION: The efficacy of vancomycin, drug of choice for methicillin-resistant Staphylococcus aureus (MRSA), has become questionable due to the emergence of MRSA isolates with reduced susceptibility. The present study was conducted to determine the vancomycin, linezolid, and daptomycin susceptibility pattern in clinical isolates of MRSA and to observe minimum inhibitory concentration (MIC) creep over 2 years if any. MATERIALS AND METHODS: MIC of vancomycin, linezolid, and daptomycin were determined by E-test in 198 MRSA isolates and their MIC 50, MIC 90, and geometric mean MIC were calculated. RESULTS: While all isolates were sensitive to vancomycin, linezolid, and daptomycin, MIC 90 of vancomycin increased from 1.5 µg/ml in 2015 to 2 µg/ml in 2016. The percentage of isolates with vancomycin MIC >2 µg/ml doubled in 2016 (12.9%) as compared to 2015 (6.1%). MIC 90 for linezolid remained steady as 3 µg/ml, but geometric mean MIC increased from 2.20 µg/ml in 2015 to 2.29 µg/ml in 2016, and more than 40% isolates showed MIC 3 µg/ml. MIC 90 and geometric mean MIC of daptomycin decreased from 0.75 µg/ml to 0.5 µg/ml and 0.50 µg/ml to 0.36 µg/ml in 2015 and 2016, respectively. CONCLUSION: MIC creep was observed with vancomycin. Although linezolid MIC was within the susceptible zone, more than 40% strains showing MIC 3 µg/ml may herald the future development of either resistant or heteroresistant. Daptomycin showed good sensitivity against MRSA isolates. Therefore, it could be considered as an alternative agent for the treatment of infections caused by MRSA. However, it should be reserved where this class has a clear therapeutic advantage over other anti-MRSA drugs.

scholarly journals Effect of Vancomycin Minimal Inhibitory Concentration on the Outcome of Methicillin-Susceptible Staphylococcus aureus Endocarditis

2014 ◽  
Vol 58 (12) ◽  
pp. 1668-1675 ◽  
Author(s):  
C. Cervera ◽  
X. Castaneda ◽  
C. G. de la Maria ◽  
A. del Rio ◽  
A. Moreno ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Minimal Inhibitory Concentration ◽  
Inhibitory Concentration ◽  
Staphylococcus Aureus Endocarditis

scholarly journals Inhibition of Penicillinase by Epigallocatechin Gallate Resulting in Restoration of Antibacterial Activity of Penicillin against Penicillinase-Producing Staphylococcus aureus

2002 ◽  
Vol 46 (7) ◽  
pp. 2266-2268 ◽  
Author(s):  
Wei-Hua Zhao ◽  
Zhi-Qing Hu ◽  
Yukihiko Hara ◽  
Tadakatsu Shimamura
Keyword(s):  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Inhibitory Concentration ◽  
Epigallocatechin Gallate ◽  
Clinical Isolates ◽  
Main Constituent ◽  
Tea Catechins ◽  
Dose Dependent Fashion ◽  
Dose Dependent

ABSTRACT The combination of epigallocatechin gallate (EGCg, a main constituent of tea catechins) with penicillin showed synergism against 21 clinical isolates of penicillinase-producing Staphylococcus aureus. Besides binding directly to peptidoglycan, the inhibition of penicillinase activity by EGCg is responsible for the synergism. EGCg inhibited the penicillinase activity in a dose-dependent fashion, with a 50% inhibitory concentration of 10 μg/ml.

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