Functional Nanostructured Oligochitosan–Silica/ Carboxymethyl Cellulose Hybrid Materials: Synthesis and Investigation of Their Antifungal Abilities

Functional hybrid materials were successfully synthesized from low-cost waste products, such as oligochitosan (OCS) obtained from chitosan (one of the main components in crab shells) and nanosilica (nSiO2) obtained from rice husk, in a 1:1 ratio (w/w), and their dispersion in the presence of carboxymethyl cellulose at pH 7 was stable for over one month without aggregation. The molecular weights, chemical structures, morphologies, and crystallinities of the obtained materials were characterized by GPC, FTIR, TEM, and XRD, respectively. The antifungal effects of OCS, nSiO2, and the OCS/nSiO2 hybrid materials were investigated via a disk-diffusion method. The results showed that the nanohybrid materials had better resistance to Phytophthora infestans fungus than the individual components, and a concentration of the OCS2/nSiO2 hybrid material of 800 mg L−1 was the lowest concentration where the material completely inhibited Phytophthora infestans growth, as measured via an agar dilution method. This study not only creates a novel environmentally friendly material with unique synergistic effects that can replace current toxic agrochemicals but also can be considered a new platform for further research in green agricultural applications.

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Comparison of methods for the determination of antimicrobial resistance in Campylobacter spp. human and the food chain isolates

Veterinární Medicína ◽

10.17221/2030-vetmed ◽

2008 ◽

Vol 52 (No. 4) ◽

pp. 169-174

Author(s):

M. Holasova ◽

R. Karpiskova ◽

S. Karpiskova ◽

V. Babak ◽

J. Schlegelova

Keyword(s):

Nalidixic Acid ◽

Antimicrobial Agents ◽

Disk Diffusion ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

Disk Diffusion Method ◽

Microdilution Method ◽

Study Results ◽

Agar Dilution

With a microdilution method, using the commercial diagnostic test Sensititre Susceptibility Plates for Campylobacter MIC (Trek Diagnostic Systems, Cleveland, OH, USA), disk diffusion and agar dilution method, resistance to six antimicrobial agents were examined in a reference strain Campylobacter jejuni ATCC 33560 and 73 thermo-tolerant isolates of Campylobacter spp. For the microdilution method and all tested antimicrobial agents, our determined values of microbiological breakpoints of resistant strains were suggested as the minimum inhibitory concentration (MICR) for ciprofloxacin ≥ 0.5, erythromycin ≥ 4, gentamicin ≥ 4, nalidixic acid ≥ 32 and tetracycline ≥ 4 μg/ml. On the basis of our study results, strains resistant to clindamycin were MICR ≥ 2 μg/ml for the dilution methods and a zone diameter R Ã¢ÂÂ¤ 16 mm for the disk diffusion method. Comparison of the results of the resistance examination, a microdilution method and disk diffusion method with the reference agar dilution method, showed that all compared methods yielded identical results with the exception of the resistance determination in erythromycin and nalidixic acid. The errors were mostly the result of the interpretation criteria for MICR of agar dilution method and different conditions of cultivation used. However, the compared methods, provide results comparable with the reference method having greater convenience of measurement.

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Inaccuracy of the Disk Diffusion Method Compared with the Agar Dilution Method for Susceptibility Testing of Campylobacter spp.

Journal of Clinical Microbiology ◽

10.1128/jcm.01090-11 ◽

2011 ◽

Vol 50 (1) ◽

pp. 52-56 ◽

Cited By ~ 31

Author(s):

Mirva Lehtopolku ◽

Pirkko Kotilainen ◽

Pauli Puukka ◽

Ulla-Maija Nakari ◽

Anja Siitonen ◽

...

Keyword(s):

Susceptibility Testing ◽

Disk Diffusion ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

Disk Diffusion Method ◽

Agar Dilution ◽

Campylobacter Spp

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In vitro efficacy of synergistic antibiotic combinations in imipenem resistant Pseudomonas aeruginosa strains

Bangladesh Journal of Medical Microbiology ◽

10.3329/bjmm.v9i1.31332 ◽

2017 ◽

Vol 9 (1) ◽

pp. 3-8

Author(s):

Aleya Farzana ◽

S. M. Shamsuzzaman

Keyword(s):

Pseudomonas Aeruginosa ◽

Carbapenem Resistance ◽

Multidrug Resistant ◽

Diffusion Method ◽

Considerable Proportion ◽

Dilution Method ◽

Agar Dilution Method ◽

Disk Diffusion Method ◽

New Antibiotics

The increase in antibiotic resistance coincided with the decline in production of new antibiotics. Combination antibiotic treatment is preferred in nosocomial infections caused by multidrug resistant Pseudomonas aeruginosa. In vitro synergism test by agar dilution method were used to choose the combinations which might be used in clinic. The aim of this study was to investigate the synergistic efficacy of antibiotic combinations in imipenem resistant P. aeruginosa strains. Carbapenem resistance (imipenem and meropenem) wasdetermined by disk diffusion method. Among isolated P. aeruginosa 44.9% were cabapenem resistant. The MIC of drugs among 25 imipenem resistant isolates ranged from >_ 256 mg/L to <_ 8 mg/L for imipenem, >_ 1024 mg/L to <_ 64 mg/L for ceftriaxone, >_ 256 mg/L to <_ 8 mg/L for amikacin, >_ 16 mg/L to <_ 2 mg/L for colistin, >_ 512 mg/L to <_ 16 mg/L for piperacillin/tazobactam. Among antibiotic combinations, piperacillin /tazobactam- amikacin was most effective with 80% synergism next to which was imipenem-amikacin with 60% synergism, then imipenem-colistin with 50% synergism, imipenem-ceftriaxone with 30% synergism. Only one combination (piperacillin/tazobactum -imipenem showed 20% antagonism. All these combinations had considerable proportion of additive effect which is also desirable for these multi drug resistant isolates.Bangladesh J Med Microbiol 2015; 9 (1): 3-8

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Detection of Plasmid-Mediated Colistin Resistant mcr-1 Gene in Escherichia coli Isolated from Infected Chicken Livers in Nepal

Animals ◽

10.3390/ani10112060 ◽

2020 ◽

Vol 10 (11) ◽

pp. 2060

Author(s):

Sayara Bista ◽

Upendra Thapa Shrestha ◽

Binod Dhungel ◽

Pragya Koirala ◽

Tulsi Ram Gompo ◽

...

Keyword(s):

Escherichia Coli ◽

Conventional Polymerase Chain Reaction ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

Human Pathogens ◽

Colistin Resistance ◽

Disk Diffusion Method ◽

E Coli ◽

Agar Dilution

Background: Plasmid-mediated resistance to the colistin in poultry is considered as an emerging problem worldwide. While poultry constitutes the major industry in Nepal, there is a paucity of evidence on colistin resistance in Escherichia coli isolates causing natural infections in poultry. This study aimed to explore the prevalence of plasmid-mediated colistin resistance gene, mcr-1 in E. coli isolated from liver samples of dead poultry suspected of E. coli infections. Methods: A total of two hundred and seventy liver samples (227 broilers and 43 layers) from dead poultry suspected of colibacillosis were collected from post-mortem in the Central Veterinary Laboratory (CVL), Kathmandu, between 1 February and 31 July 2019. The specimens were processed to isolate and identify E. coli; an antimicrobial susceptibility test (AST) using disk diffusion method was performed with 12 different antibiotics: Amikacin (30 µg), ampicillin (10 µg), ciprofloxacin (5 µg), chloramphenicol (30 µg), cefoxitin (30 µg), ceftazidime (30 µg), ceftriaxone (30 µg), cotrimoxazole (25 µg), gentamicin (10 µg), imipenem (10 µg), levofloxacin (5 µg) and tetracycline (30 µg). Colistin resistance was determined by agar dilution method and colistin-resistant strains were further screened for plasmid-mediated mcr-1 gene, using conventional polymerase chain reaction (PCR). Results: Out of 270 liver samples, 53.3% (144/270) showed growth of E. coli. The highest number (54%; 109/202) of E. coli isolates was obtained in the liver samples from poultry birds (of both types) aged less than forty days. In AST, 95.1% (137/144) and 82.6% (119/144) of E. coli isolates were resistant against tetracycline and ciprofloxacin, respectively, while 13.2% (19/144) and 25.7% (37/144) isolates were resistant to cefoxitin and imipenem, respectively. In the same assay, 76.4% (110/144) E. coli isolates were multi-drug resistant (MDR). The phenotypic prevalence of colistin resistance was 28.5% (41/144). In the PCR assay, 43.9% (18/41) of colistin-resistant isolates were screened positive for plasmid-mediated mcr-1. Conclusion: The high prevalence of mcr-1 in colistin-resistant E. coli isolates in our study is a cause of concern for the probable coming emergence of colistin resistance in human pathogens, due to horizontal transfer of resistant genes from poultry to human isolates.

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Department of Microbiology, Bangladesh Agricultural University, Mymensingh

Bangladesh Journal of Medical Microbiology ◽

10.3329/bjmm.v2i2.28839 ◽

2016 ◽

Vol 2 (2) ◽

pp. 3-6

Author(s):

Nahida Akther Zahan ◽

Md. Akram Hossain ◽

AKM Shamsuzzaman ◽

AKM Musa ◽

Md. Chand Mahamud ◽

...

Keyword(s):

Clinical Laboratory ◽

Methicillin Resistance ◽

Meca Gene ◽

Toxin Production ◽

Latex Agglutination ◽

Diffusion Method ◽

National Committee ◽

Dilution Method ◽

Agar Dilution Method ◽

Disk Diffusion Method

The study was done to detect different exotoxins among the strains of Staphylococcus aureus isolated in the department of Microbiology, Mymensingh Medical College in collaboration with the Department of Medicine under the Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh between the periods from July, 2006 to June, 2007. A total of 40 S. aureus isolates investigated in this study were identified by standard microbiological techniques. Antimicrobial susceptibility of the isolates to Oxacillin was carried out by disk diffusion method as per recommendation of the National Committee for Clinical Laboratory Standards. Any isolate showing resistance to Oxacillin was tested again by agar dilution method to determine minimum inhibitory concentration (MIC) of Methicillin. All strains were also tested for mecA gene by Polymerase Chain Reaction (PCR) for confirmation of Methicillin resistance. Enterotoxin (A-D) and Toxic Shock Syndrome Toxin-1 (TSST-1) were detected by Reverse Passive Latex Agglutination (RPLA) test. Out of 40 S. aureus isolates, 7 (17.5%) Methicillin Resistant S. aureus (MRSA), 1 (2.5%) Methicillin Sensitive S. aureus (MSSA) produced Staphylococcal Enterotoxin A (SE-A) and 1 MRSA isolate was positive for TSST-1. In case of combined toxin production among the S. aureus isolates, 2 (5%) MSSA were found to produce SE-A and SE-B, 2 (5%) MSSA produced SE-C and SE-D, and 1 (2.5%) MRSA, 1 (2.5%) MSSA produced SE-C and TSST-1.Bangladesh J Med Microbiol 2008; 02 (02): 3-6

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Characterization of plasmid-mediated qnrA and qnrB genes among Enterobacteriaceae strains: quinolone resistance and ESBL production in Ismailia, Egypt

Egyptian Journal of Medical Human Genetics ◽

10.1186/s43042-019-0026-1 ◽

2019 ◽

Vol 20 (1) ◽

Author(s):

Samaa A. Taha ◽

Hanan Hassan Omar ◽

wafaa Hassan Hassan

Keyword(s):

Resistance Genes ◽

Quinolone Resistance ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

University Hospitals ◽

Disk Diffusion Method ◽

Extended Spectrum Beta Lactamase ◽

Tract Infections ◽

Resistance Rates

Abstract Background Plasmid-mediated quinolone resistance genes (PMQR) are mainly associated with clinical isolates of Enterobacteriaceae and complicate treatment of infections caused by these isolates worldwide. Extended-spectrum-beta-lactamase (ESBL)-producing bacteria are resistant to common antibiotics and also through many mechanisms, ESBL could be disabling other types of antibiotics. This study aimed to assess the prevalence of quinolone resistance and ESBL among Enterobacteriaceae strains and investigated the presence of qnrA and qnrB genes in these strains which were isolated from urinary tract infections in Ismailia, Egypt. Ninety-four Enterobacteriaceae isolates were collected from cases of UTIs admitted to the intensive care unit, Suez-Canal University Hospitals, between October 2017 and January 2018. Antibacterial susceptibility was determined by the disk diffusion method. A polymerase chain reaction assay was used to detect qnrA and qnrB resistance genes in quinolone- and fluoroquinolone-resistant and ESBL strains. Also, ciprofloxacin MIC was determined by the agar dilution method. Results Resistance rates were 59.6%, 54.3%, 53.2%, 53.2%, and 53.2% to NA, LEV, NOR, CIP, and FX, respectively. Of 56 NA-resistant isolates, 7 (12.5%) and 6 (10.7%) were positive for qnrA and qnrB, respectively, with only one isolate co-harboring both genes. ESBL-producing bacteria was 66.2% of isolates. The MICs for ciprofloxacin ranged from 32–256 μg/ml in ciprofloxacin-resistant isolates. Conclusion Our study shows high resistance rates of Enterobacteriaceae to quinolones and ESBL in our hospital which necessitate appropriate use of these antibiotics to reserve their application for therapy. The prevalence of quinolone-resistant and ESBL-producing Enterobacteriaceae was approximately 60% and 70% respectively.

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The study of reduced susceptibility of methicillin resistant Staphylococcus aureus to various antibiotics with special reference to glycopeptides in a tertiary care hospital in central India

International Journal of Community Medicine and Public Health ◽

10.18203/2394-6040.ijcmph20191132 ◽

2019 ◽

Vol 6 (4) ◽

pp. 1426

Author(s):

Swati S. Kale ◽

Ashwini Patil

Keyword(s):

Staphylococcus Aureus ◽

Tertiary Care ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

Care Hospital ◽

Diagnostic Laboratory ◽

Disk Diffusion Method ◽

Methicillin Resistant ◽

Agar Dilution

Background: Staphylococcus aureus has emerged over the past several decades as a leading cause of hospital-associated and community acquired infections. Methicillin resistant S. aureus (MRSA), which are often resistant to several classes of antibiotics, is the most common cause of nosocomial infections and pose a great threat to the world. Vancomycin is regarded as the first-line drug for treatment of MRSA but resistance to this drug is being reported now a day.Methods: It was carried out for a period between January 2014 to June 2017 in the microbiology diagnostic laboratory. MRSA detection was performed by cefoxitin disk diffusion method. Screening for the vancomycin intermediate and the vancomycin resistant S. aureus (VISA and VRSA respectively) was carried out by using vancomycin screen. MIC (minimum inhibitory concentration) of vancomycin was tested by agar dilution method and E strip on all MRSA isolates.Results: A total of 287 S. aureus clinical isolates were included in the study. All MRSA were inoculated on vancomycin screen agar. Visible growth was present in 8 isolates. Five (3.73%) MRSA isolates with MIC of 4 were termed VISA (vancomycin intermediate S. aureus) by agar dilution method. Six isolates had the MIC of 4 and were termed as VISA.Conclusions: As disc diffusion method is not recommended by CLSI for S. aureus, vancomycin screen agar and MIC determination by either of the methods viz. agar dilution or E test can be used.

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Antimicrobial Resistance in Salmonella Typhi Isolated From a Referral Hospital of Kathmandu, Nepal

Microbiology Insights ◽

10.1177/11786361211056350 ◽

2021 ◽

Vol 14 ◽

pp. 117863612110563

Author(s):

Saroj Khadka ◽

Basudha Shrestha ◽

Anil Pokhrel ◽

Sachin Khadka ◽

Rajesh Dhoj Joshi ◽

...

Keyword(s):

Typhoid Fever ◽

Antibiotic Susceptibility ◽

Large Scale ◽

Salmonella Typhi ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

First Line ◽

Disk Diffusion Method

Purpose: The morbidity and mortality due to typhoid fever can be significantly reduced with the use of effective antibiotics. At present, fluoroquinolones, third generation cephalosporins, and azithromycin are widely used to treat typhoid fever. However, changing antibiotic susceptibility among Salmonella Typhi and Salmonella Paratyphi poses a particular challenge to the therapeutic management of enteric fever. The objective of this study was to assess the antibiotic susceptibility pattern of Salmonella Typhi isolates. Patients and Methods: A total of 706 blood specimens were collected from febrile patients attending the outpatient department of Kathmandu Model Hospital during June to September, 2018. The antibiotic susceptibility testing for 11 different antibiotics (nalidixic acid, ciprofloxacin, ofloxacin, levofloxacin, cefixime, ceftriaxone, cefotaxime, azithromycin, cotrimoxazole, chloramphenicol, and amoxicillin) was performed by disk diffusion method. Furthermore, minimum inhibitory concentration (MIC) values of ciprofloxacin, ofloxacin, and azithromycin were determined by agar dilution method. Mutation at gyrA ser83 associated with reduced susceptibility to fluoroquinolones was determined by PCR-RFLP. Results: Out of 706 blood samples, 6.94% (n = 49) were culture positive for Salmonella enterica (S. Typhi, n = 46). It was revealed that 97.8% S. Typhi isolates were susceptible to conventional first-line antibiotics (ampicillin, chloramphenicol, and cotrimoxazole), 97.3% to cephalosporins and 95.7% to azithromycin. S. Typhi were either resistant or intermediately susceptible to fluoroquinolones: 97.8% to ciprofloxacin, 91.3% to ofloxacin, and 89.1% to levofloxacin. The MIC of ciprofloxacin, ofloxacin, and azithromycin for S. Typhi ranged from 0.008 to 32, 0.03 to 16, and 2 to 8 μg/mL, respectively. Out of 46 S. Typhi isolates, 44 (95.65%) had gyrA ser83 mutation. Conclusion: Fluoroquinolones have poor activity against Salmonella Typhi. The trends of increasing azithromycin MIC value among S. Typhi might limit its use for the treatment of typhoid fever. Effectiveness of conventional first-line antibiotics in vitro suggests considering their clinical use after large-scale studies.

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Clonal dissemination ofPseudomonas aeruginosaST235 carryingblaIMP-6and emergence ofblaGES-24andblaIMP-10on novel genomic islands PAGI-15 and -16 in Korea

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01601-16 ◽

2016 ◽

pp. AAC.01601-16 ◽

Cited By ~ 11

Author(s):

Jun Sung Hong ◽

Eun-Jeong Yoon ◽

Hyukmin Lee ◽

Seok Hoon Jeong ◽

Kyungwon Lee

Keyword(s):

Genetic Relatedness ◽

Genomic Islands ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

Disk Diffusion Method ◽

Class 1 Integrons ◽

Carbapenemase Gene ◽

Class 1 ◽

Clonal Spread

A total of 431Pseudomonas aeruginosa(PA) clinical isolates were collected from 29 general hospitals in Korea in 2015. Antimicrobial susceptibility was tested by the disk diffusion method and MICs of carbapenems were determined by agar dilution method. Carbapenemase genes were amplified by PCR and sequenced and the structures of class 1 integrons surrounding the carbapenemase gene cassettes were analyzed by PCR mapping. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed for strain typing. Whole-genome sequencing was carried out to analyze PA genomic islands (PAGIs) carrying theblaIMP-6,blaIMP-10, andblaGES-24genes. The rates of carbapenem-non-susceptible and carbapenemase-producing PA isolates were 34.3% (148/431) and 9.5% (41/431), respectively. IMP-6 was the most prevalent carbapenemase type, followed by VIM-2, IMP-10, and GES-24. All carbapenemase genes were located on class 1 integrons showing 6 different types in chromosome. All isolates harboring carbapenemase genes exhibited genetic relatedness by PFGE (similarity >80%); moreover, all isolates were identified as sequence type 235 (ST235), with the exception of two ST244 isolates by MLST. TheblaIMP-6,blaIMP-10, andblaGES-24genes were found to be located on two novel PAGIs, designated PAGI-15 and PAGI-16. Our data support the clonal spread of an IMP-6-producing PA ST235 strain and the emergence of IMP-10 and GES-24 demonstrates the diversification of carbapenemases in PA in Korea.

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Comparative Analysis of Gradient Diffusion and Disk Diffusion with Agar Dilution for Susceptibility Testing of Elizabethkingia anophelis

Antibiotics ◽

10.3390/antibiotics10040450 ◽

2021 ◽

Vol 10 (4) ◽

pp. 450

Author(s):

Chien-Tung Chiu ◽

Chung-Hsu Lai ◽

Yi-Han Huang ◽

Chih-Hui Yang ◽

Jiun-Nong Lin

Keyword(s):

Antimicrobial Agents ◽

Susceptibility Testing ◽

Disk Diffusion ◽

Diffusion Method ◽

Dilution Method ◽

Agar Dilution Method ◽

Disk Diffusion Method ◽

Gradient Diffusion ◽

Minimum Requirements ◽

Agar Dilution

Elizabethkingia anophelis has recently emerged as a cause of life-threatening infections. This study compared the results of antimicrobial susceptibility testing (AST) conducted for E. anophelis through different methods. E. anophelis isolates collected between January 2005 and June 2019 were examined for their susceptibility to 14 antimicrobial agents by using disk diffusion, gradient diffusion (Etest; (bioMérieux S.A., Marcy l’Etoile, France), and agar dilution methods. The agar dilution method was the reference assay. According to the agar dilution method, the isolates exhibited the highest susceptibility to minocycline (100%), doxycycline (97.6%), rifampin (95.2%), and levofloxacin (78.6%). A very major error rate of >1.5% was observed for nine antibiotics tested using the disk diffusion method. The overall categorical agreement rate between the disk diffusion and agar dilution methods was 74.8%, and ceftazidime, minocycline, levofloxacin, and rifampin met the minimum requirements for discrepancy and agreement rates. The Etest method tended to produce lower log2 minimum inhibitory concentrations for the antibiotics, except for trimethoprim–sulfamethoxazole and rifampin; the method resulted in very major errors for nine antibiotics. The overall essential and categorical agreement rates between the Etest and agar dilution methods were 67.3% and 76.1%, respectively. The Etest method demonstrated acceptable discrepancy and agreement rates for ceftazidime, minocycline, doxycycline, levofloxacin, and rifampin. AST results obtained through the disk diffusion and Etest methods for multiple antibiotics differed significantly from those obtained using the agar dilution method. These two assays should not be a routine alternative for AST for E. anophelis.

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