scholarly journals Vancomycin MIC Distribution among Methicillin-Resistant Staphylococcus Aureus. Is Reduced Vancomycin Susceptibility Related To MIC Creep?

2018 ◽  
Vol 7 (1) ◽  
pp. 12-18 ◽  
Author(s):  
Hala B. Othman ◽  
Rania M. Abdel Halim ◽  
Fatma Alzahraa M. Gomaa ◽  
Malaka Z. Amer
Keyword(s):  
Staphylococcus Aureus ◽  
Treatment Failure ◽  
Detection Rate ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Broth Microdilution ◽  
Microdilution Method ◽  
Creep Analysis ◽  
Broth Microdilution Method ◽  
Vitek 2 ◽  
Vancomycin Treatment

AIM: To determine the distribution of vancomycin MIC and the frequency of S. aureus strains with reduced vancomycin susceptibility among Methicillin-Resistant Staphylococcus aureus (MRSA) isolates. METHODS: MRSA isolates (n = 100) were tested for reduced susceptibility to vancomycin using  MIC broth microdilution method (BMD), vancomycin screening agar with different vancomycin concentrations with and without casein, and Vitek 2 system. RESULTS: BMD detected (22%) vancomycin-intermediate S. aureus (VISA) and (78%) vancomycin-susceptible S. aureus (VSSA) but couldn’t detect nine (Heterogeneous VISA) (hVISA)   isolates (9%) with MIC ≤ 2 µg/ml that grew on screening agar 4 µg/ml or 6 µg/ml. Adding casein to vancomycin screening agar increased detection rate of VISA by 4.5%.  Screening agar with 6 µg/ml vancomycin overall detection rate for VISA was 95.45%. Probable ‘pre-hVISA’isolates (17%) showed growth on vancomycin screening agar 2 µg/ml with casein. Vitek 2 system failed to detect any VISA isolates. CONCLUSION: Vancomycin screening agar; 2 µg/ml and (4 and 6 µg/ml) were able to detect; probable “pre hVISA and (hVISA and VISA) isolates respectively based on their BMD MIC values. Decreased vancomycin susceptibility in MRSA isolates might be related to MIC creep. Analysis of vancomycin MIC values over longer periods is recommended to further study this phenomenon and its impact on vancomycin treatment failure.   ABSTRACT Aims: Determine the distribution of vancomycin MIC and the frequency of S. aureus strains with reduced vancomycin susceptibility among MRSA isolates.  Methods:  MRSA isolates (n =100) were tested for reduced susceptibility to vancomycin using  MIC broth microdilution method(BMD), vancomycin screening agar with different vancomycin concentrations with and without casein, and Vitek 2 system.  Results: BMD detected (22%) vancomycin intermediate S. aureus(VISA) and (78%) vancomycin susceptible S. aureus(VSSA) but failed to detect nine (Heterogeneous VISA) (hVISA)  isolates (9%) with MIC ≤2ug/ml that grew on screening agar 4ug/ml or 6 ug/ml. Adding casein to vancomycin screening agar increased detection rate of VISA by 4.5%.  Screening agar with 6 ug/ml vancomycin over all detection rate for VISA was 95.45%. Probable ‘pre-hVISA’isolates (17%) showed growth on vancomycin screening agar 2µg/ml with casein. Vitek 2 system failed to detect any VISA isolates. Conclusion: vancomycin screening agar; 2 µg/ml and (4 and 6 µg/ml) were able to detect; probable “pre hVISA and (hVISA and VISA) isolates respectively based on their BMD MIC values. Decreased vancomycin susceptibility in MRSA isolates might be related to MIC creep. Analysis of vancomycin MIC values over longer periods of time is recommended to further study this phenomenon and its impact on vancomycin treatment failure.    

scholarly journals In VitroAntistaphylococcal Effects ofEmbelia schimperiExtracts and Their Component Embelin with Oxacillin and Tetracycline

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Johana Rondevaldova ◽  
Olga Leuner ◽  
Alemtshay Teka ◽  
Ermias Lulekal ◽  
Jaroslav Havlik ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Medicinal Plants ◽  
Bacterial Infections ◽  
Inhibitory Concentration ◽  
Developed Countries ◽  
Positive Interactions ◽  
Fractional Inhibitory Concentration ◽  
Broth Microdilution ◽  
Microdilution Method ◽  
Broth Microdilution Method

Bacterial infections are in less-developed countries traditionally treated by remedies prepared from medicinal plants.Embelia schimperi(Vatke) is a plant used as a taenicide or disinfectant in Ethiopia, very often taken mixed with another plant species. In the present study, we examined two extracts prepared from seeds and twigs with leaves ofE. schimperiand its main present secondary metabolite embelin for their antibacterial combinatory effect with oxacillin and tetracycline against sensitive and resistantStaphylococcus aureusstrains. Minimum inhibitory concentrations were determined through the broth microdilution method, whereas the combinatory effect was evaluated through fractional inhibitory concentration sum (ΣFIC) indices. Results show many positive interactions and synergy occurring in embelin and oxacillin combinations against 4 out of 9 strains (ΣFIC 0.203–0.477) and for embelin and tetracycline combination against 3 out of 9 strains (ΣFIC 0.400–0.496). Moreover, the resistance to oxacillin has been overcome in 2 strains and to tetracycline in 3 strains. According to our knowledge, this is the first study showing antimicrobial combinatory effect ofE. schimperias well as of embelin. These findings can be used for the further research targeted on the development of new antistaphylococcal agents.

scholarly journals Antibacterial Triterpenoids from the Bark of Sonneratia alba (Lythraceae)

2015 ◽  
Vol 10 (2) ◽  
pp. 1934578X1501000
Author(s):  
Harizon ◽  
Betry Pujiastuti ◽  
Dikdik Kurnia ◽  
Dadan Sumiarsa ◽  
Yoshihito Shiono ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Mass Spectrometric ◽  
Broth Microdilution ◽  
Mass Spectrometric Data ◽  
Spectrometric Data ◽  
Gram Positive Bacteria ◽  
Microdilution Method ◽  
Sonneratia Alba ◽  
Broth Microdilution Method

The new lupane-type triterpenoid, 3β-hydroxy-lup-9(11), 12-diene, 28-oic acid (1), along with two known lupane-type triterpenoids, lupeol (2) and lupan-3p-ol (3), were isolated from the bark of Sonnetaria alba. The structure of the new compound was elucidated on the basis of spectroscopic and mass spectrometric data analysis. Using the broth microdilution method, all compounds exhibited antibacterial activity against the Gram-positive bacteria Staphylococcus aureus ATCC 6538 and Streptococcus mutans ATCC 25175, with minimum inhibitory concentrations ranging from 15-33 to 35-55 ng/mL, respectively.

scholarly journals Development, optimization, standardization, and validation of a simple in-house agar gradient method to determine minimum inhibitory concentration of vancomycin for Staphylococcus aureus

2019 ◽  
Vol 11 (03) ◽  
pp. 220-228
Author(s):  
Sumit Rai ◽  
Mukta Tandon ◽  
Narendra Pal Singh ◽  
Vikas Manchanda ◽  
Iqbal Rajinder Kaur
Keyword(s):  
Staphylococcus Aureus ◽  
Gradient Method ◽  
Inhibitory Concentration ◽  
Control Strain ◽  
Broth Microdilution ◽  
Clinical Strains ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Commercial Strip ◽  
Validation Stage

Abstract BACKGROUND: The Clinical and Laboratory Standards Institute recommends reporting minimum inhibitory concentration (MIC) values of vancomycin for Staphylococcus aureus. Commercial MIC strips are expensive, and the traditional broth microdilution method is cumbersome. With this background, we attempted to develop and standardize an in-house agar gradient method to determine MIC values of vancomycin for S. aureus. OBJECTIVES: To develop and validate an in-house vancomycin MIC strip, based on simple agar gradient method for S. aureus as per bioassay development guidelines. MATERIALS AND METHODS: Filter paper gradient strips were made in house and impregnated with varying concentrations of vancomycin to create an antibiotic gradient. During standardization, MICs of ninety clinical strains of S. aureus and ATCC 29213 were tested by the broth microdilution and commercial strip followed by the in-house strip. During the validation stage, MICs of ninety different clinical strains of S. aureus and ATCC 29213 were determined by the in-house strip followed by MIC detection by broth microdilution and commercial strips. A reading of more than ± 1log2 dilution compared with broth microdilution was considered as an outlier. RESULTS: During the initial stage, there were 7/90 outliers in the clinical strains, and no outliers were seen with the ATCC 29213 control strain. Corrective action included increasing precaution during the antibiotic impregnation on the strip. During validation stage, only 4/90 outliers were observed in the clinical strains. The commercial strips had 29/90 among clinical and 15/30 outliers in the control strain during the prevalidation phase. Despite maintaining cold chain during the validation phase, the outliers for commercial strip were 18/90 and 4/30 for clinical and control strains, respectively. CONCLUSION: Reporting vancomycin MIC for S. aureus may be attempted using the in-house method after validating it with a gold standard broth microdilution method and quality control as per protocol.

scholarly journals Baseline Activity of Telavancin against Gram-Positive Clinical Isolates Responsible for Documented Infections in U.S. Hospitals (2011-2012) as Determined by the Revised Susceptibility Testing Method

2014 ◽  
Vol 59 (1) ◽  
pp. 702-706 ◽  
Author(s):  
Rodrigo E. Mendes ◽  
David J. Farrell ◽  
Helio S. Sader ◽  
Robert K. Flamm ◽  
Ronald N. Jones
Keyword(s):  
Staphylococcus Aureus ◽  
Susceptibility Testing ◽  
The United States ◽  
Broth Microdilution ◽  
Content Type ◽  
Testing Method ◽  
Microdilution Method ◽  
Baseline Activity ◽  
Broth Microdilution Method ◽  
Vancomycin Resistant

ABSTRACTTelavancin had MIC50and MIC90values of 0.03 and 0.06 μg/ml (100.0% susceptible), respectively, against methicillin-resistant and -susceptibleStaphylococcus aureus. Telavancin was active against vancomycin-susceptibleEnterococcus faecalis(MIC50/90, 0.12/0.12 μg/ml; 100% susceptible) andEnterococcus faecium(MIC50/90, 0.03/0.06 μg/ml), while higher MIC values were obtained against vancomycin-resistantE. faecium(MIC50/90, 1/2 μg/ml) andE. faecalis(MIC50/90, >2/>2 μg/ml). Streptococci showed telavancin modal MIC results of ≤0.015 μg/ml, except againstStreptococcus agalactiae(i.e., 0.03 μg/ml). This study reestablishes the telavancin spectrum of activity against isolates recovered from the United States (2011-2012) using the revised broth microdilution method.

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