Epidemiological cut-off values for Vibrio anguillarum MIC and disc diffusion data generated by standardised methods.

The characterization of wild-type minimum inhibitory concentration (MIC) and zone diameter distributions with the setting of epidemiological cut-off values (ECOFFs or ECVs) provides a reference for the otherwise relative MIC values in the international system for antimicrobial susceptibility testing. Distributions of MIC values for a species and an agent follow a log-normal distribution, which in the absence of resistance mechanisms is monomodal and designated wild type (WT). The upper end of the WT distribution, the ECOFF, can be identified with statistical methods. In the presence of phenotypically detectable resistance, the distribution has at least one more mode (the non-WT), but despite this, the WT is most often identifiable using the same methods. The ECOFF provides the most sensitive measure of resistance development in a species against an agent. The WT and non-WT modes are independent of the organism´s response to treatment, but when the European Committee on Antimicrobial Susceptibility Testing (EUCAST) determines the clinical breakpoints, the committee avoids breakpoints that split WT distributions of target species. This is to avoid the poorer reproducibility of susceptibility categorization when breakpoints split major populations but also because the EUCAST has failed to identify different clinical outcomes for isolates with different MIC values inside the wild-type distribution. In laboratory practice, the ECOFF is used to screen for and exclude resistance and allows the comparison of resistance between systems with different breakpoints from different breakpoint organizations, breakpoints evolving over time, and different breakpoints between human and animal medicine. The EUCAST actively encourages colleagues to question MIC distributions as presented on the website (https://www.eucast.org/mic_and_zone_distributions_and_ecoffs) and to contribute MIC and inhibition zone diameter data.

Evaluation of the correlation between minimum inhibitory concentrations (MIC) and disk diffusion data of Flavobacterium psychrophilum isolated from outbreaks occurred in Chilean salmonid farms

Epidemiological cut-off values (ECVs) based on minimal inhibitory concentration (MIC) distribution have been recently proposed for some antifungal drug/Cryptococcus neoformans combinations. However, these ECVs vary according to the species studied, being serotypes and the geographical origin of strains, variables to be considered. The aims were to define the wild-type (WT) population of the C. neoformans species complex (C. neoformans) isolated from patients living in Argentina, and to propose ECVs for six antifungal drugs. A total of 707 unique C. neoformans isolates obtained from HIV patients suffering cryptococcal meningitis were studied. The MIC of amphotericin B, flucytosine, fluconazole, itraconazole, voriconazole and posaconazole was determined according to the EDef 7.2 (EUCAST) reference document. The MIC distribution, MIC50 , MIC90 and ECV for each of these drugs were calculated. The highest ECV, which included ≥95% of the WT population modelled, was observed for flucytosine and fluconazole (32 μg ml(-1) each). For amphotericin B, itraconazole, voriconazole and posaconazole, the ECVs were: 0.5, 0.5, 0.5 and 0.06 μg ml(-1) respectively. The ECVs determined in this study may aid in identifying the C. neoformans strains circulating in Argentina with decreased susceptibility to the antifungal drugs tested.

Infections that are commonly happened in developing countries such as Indonesia are skin infection that caused by Staphylococcus aureus and Staphylococcus epidermidis , and digestive infection that caused by Bacillus subtilis and Bacillus cereus . The ethanol extract of Bambusa vulgaris leaves contained metabolite compounds that potential to have antibacterial activity. This study aimed to determine MIC (Minimum Inhibitory Concentration) value of ethanol extract of Bambusa vulgaris leaves against those four bacteria. The research was conducted by Kirby-Bauer disc diffusion method using ethanol extract of Bambusa vulgaris leaves with concentration variations of 80 mg/mL, 40 mg/mL, 20 mg/mL, 10 mg/mL, 5 mg/mL, 2.5 mg/mL, and 1.25 mg/mL. The results showed that ethanol extract of Bambusa vulgaris leaves can inhibit the growth of all four bacteria with MIC value against Staphylococcus aureus and Bacillus subtilis is 20 mg/mL, with inhibition zone diameter of 7,33 ± 0,416 mm and 6,32 ± 0,057 mm respectively. While the MIC value against Staphylococcus epidermidis and Bacillus cereus is 10 mg/mL, with inhibitory zone diameter obtained respectively 7,33 ± 0,416 mm and 6,07 ± 0,029 mm. The conclusion of this research was that ethanol extract of Bambusa vulgaris leaves had inhibition zone with MIC value 20 mg/mL against Staphylococcus aureus and Bacillus subtilis , and 10 mg/mL against Staphylococcus epidermidis and Bacillus cereus . Keywords: Ethanol extract of Bambusa vulgaris leaves, antibacterial, disc diffusion, MIC (Minimum Inhibitory Concentration)

Coagulase-negative staphylococci (CNS) are one of the primer agents of blood stream infections (BSI) and catheter-related bloodstream infections (CR-BSI) which are associated mostly with the usage of central venous catheters and, important causes of morbidity and mortality despite the usage of antibacterial and supportive treatment. It is important to determine the properties of these causative microorganisms in order to make appropriate treatment of such infections. The aims of our study were to evaluate the biofilm formation of coagulase negative staphylococci (CNS) which were causative agents of bloodstream (BSI) and catheter related bloodstream infections (CR-BSI), to determine the minimum inhibitory concentration (MIC) of planktonic forms and minimal biofilm eradication concentration (MBEC) of sessile forms for vancomycin and daptomycin and to evaluate the efficacy of these antibiotics in infections with biofilm-forming isolates in vitro. A total of 65 CoNS (n= 26 catheter colonizers, n= 28 CR-BSI, n= 11 BSI agents) were identified by conventional methods and also with BD Phoenix (Becton Dickinson, USA) and Bruker Microflex MS (Bruker Daltonics, Germany) systems. Methicillin resistance was determined by the presence of mecA gene with PCR. MIC values of vancomycin and daptomycin were investigated by broth microdilution, for daptomycin medium containing 25 and 50 μg/ml Ca++ were used. Assessment of biofilm formation and detection of MBEC were determined by microplate method. The clonal relationship was investigated by the PFGE method. A total of 65 isolates; 26 catheter colonizers, 28 CR-BSI agents and 11 BSI agents were evaluated and identified as Staphylococcus epidermidis (n= 33), Staphylococcus haemolyticus (n= 16), Staphylococcus hominis (n= 15), and Staphylococcus capitis (n= 1). 81.5% of the isolates were found to be methicillin resistant and all of them were found to be sensitive to vancomycin (MIC= 0.125-4 μg/ml) and daptomycin (MIC= 0.062-0.25 μg/ml in 25 μg/ml Ca++ and MIC= 0.031-0.50 μg/ml in 50 μg/ml Ca++ containing medium). MIC values were lower in medium containing 50 μg/ml Ca++ for daptomycin. As it is known that the efficacy of daptomycin depends on the physiological levels of Ca++, which causes conformational changes in the structure of these antibacterials. Our findings also suggested that high levels of Ca++ are needed to ensure the efficacy of daptomycin. All of the isolates produced biofilm at different strengths of positivity (n= 12/18.5% weak, n= 35/%53.8 moderate, n= 18/%27.7 strong). MBEC and MBEC/MIC values for vancomycin were found to be higher than daptomycin (p< 0.001). Strong biofilm producers had higher MBEC and MBEC/MIC, MBEC50/MIC50 ve MBEC90/MIC90 values (p< 0.05). Especially in infections with biofilm forming isolates, the detection of only MIC values are not always sufficient in the treatment of biofilm-related infections as they reflect the sensitivity of planktonic bacteria. The inconsistency between the MIC and MBEC values and the high rates of MBEC/MIC found in our study supported this prediction.The lower detection of MBEC and MBEC/MIC values of daptomycin compared to the same values of vancomycin suggested that daptomycin might be effective at lower doses than vancomycin in the treatment of biofilm infections.

This study aims to determine the minimal inhibitory concentration (MIC) distribution and the epidemiological cut-off values (ECVs) of Malassezia pachydermatis and Malassezia furfur isolates for fluconazole (FLZ), itraconazole (ITZ), posaconazole (POS), and voriconazole (VOR). A total of 62 M. pachydermatis strains from dogs with dermatitis and 78 M. furfur strains from humans with bloodstream infections (BSI) were tested by a modified broth microdilution Clinical and Laboratory Standards Institute (CLSI) method. ITZ and POS displayed lower MICs than VOR and FLZ, regardless of the Malassezia species. The MIC data for azoles of M. pachydermatis were four two-fold dilutions lower than those of M. furfur. Based on the ECVs, about 94% of Malassezia strains might be categorized within susceptible population for all azoles, except for FLZ, and azole cross-resistance was detected in association with FLZ in M. pachydermatis but not in M. furfur.The study proposes, for the first time, tentative azole ECVs for M. pachydermatis and M. furfur for monitoring the emergence of isolates with decreased susceptibilities and shows that the azole MIC distribution varied according to the Malassezia species tested, thus suggesting the usefulness of determining the susceptibility profile for effective treatment of each species.

Bacteria have acquired resistance against almost all antibiotics because of the misuse of antibacterial agents and long periods of treatment. Antimicrobial peptides (AMPs) are one of the most encouraging candidates to solve this problem, as they possess high prokaryotic selectivity, and affect the bacteria by a unique mode of action. Novel cyclic undecapeptides (QNRNFYFNRNQ and QNRNFHFNRNQ) and their linear counterparts were investigated for their antibacterial activity against virulent strains. The minimal inhibitory concentration (MIC) values showed that tyrosine and histidine AMPs have promising antibacterial activity against virulent bacteria. The MIC values against the P. aeruginosa PA14, E. coli O157:H7 CR3, S. aureus 209P, and B. subtilis ATCC 6633 bacterial strains were evaluated for the cyclic peptide containing tyrosine, and their values were 6.25, 12.5, 12.5, and 12.5 µM, respectively. Meanwhile, for the linear form, they were 9.3, 12.5, 12.5, and 12.5 µM, respectively. The cyclic-peptide–containing histidines’ MIC values were 6.25, 3.1, 6.25, and 3.1 µM, respectively. Meanwhile, for the linear form, they were 3.1, 3.1, 3.1, and 6.25 µM, respectively. The antibacterial activities of the new AMPs were compared with that of gentamicin sulfate, and showed relatively higher potencies. Time-inhibition studies demonstrated the rapid antibacterial effects of the novel AMPs, which were more likely to be concentration-dependent, rather than time-dependent. At double the MIC concentration, all of the tested peptides exhibited relatively stable antibacterial effects up to 24 h, especially the peptides containing tyrosine, which showed an improved antibacterial effect.

Staphylococcus saprophyticus (S. saprophyticus) is the second most common bacteria causing uncomplicated urinary tract infections (UTIs). It is considered non-susceptible to mecillinam, with no defined breakpoint and only few available minimal inhibitory concentration (MIC) observations. However, this consideration does not correlate with clinical outcome. With this study, we aimed to provide a comprehensive MIC distribution analysis of mecillinam for S. saprophyticus, which could be useful for determining potential breakpoints. We studied 112 isolates of S. saprophyticus from human urine samples from 4 European countries. The broth microdilution and MIC test strip methods were used to determine mecillinam MIC. Broth microdilution MICs ranged from 4 to ≥ 256 mg/L, with a binary clustering at 32 to 64 and ≥ 256 mg/L. The MICs were duplicated for each isolate with similar results. The MIC distribution from the test strip method aligned well with the results from the broth microdilution method. Disc diffusion test yielded an 8 mm inhibitory zone in three isolates with MIC of 32 mg/L. Considering mecillinam concentration in the urine usually reach 200 mg/L in conventional treatment, the clinical success frequently seen with pivmecillinam treatment for UTIs caused by S. saprophyticus may be explained by the MIC cluster of 32 to 64 mg/L. This cluster might be identified by an 8 mm inhibitory zone in disc diffusion tests. Clinical studies with MIC data are needed to examine potential breakpoints. As of now, clinicians should not switch empirical pivmecillinam treatment to other antibiotics based solely on the presence of S. saprophyticus. © 2025 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy.

People have been ailing regularly nowadays and conventional antibiotics have become less potent due to drug resistance. The molecular architecture of the antibiotics issued to patients has only marginally changed since their discovery, thus this has caused microorganisms to adapt or survive the repeated administration of the same drugs over time, causing medication to be less effective, and people becoming sicker because the lack of new, different and potent antibiotic structures has enabled bacteria to mutate. This presented the pressing need to develop pyrazole compounds because they suit the category of being structurally different and have been reported to exhibit excellent antibacterial activities. To obtain pyrazole derivatives, Microwave-Assisted Organic Synthesis (MAOS) was utilized to synthesize ten novel compounds of (4Z)-4-arylidene-4,5-dihydro-3-methyl-5-oxopyrazole-1-carbothioamide derivatives (4a-4j) by a one-pot multicomponent reaction (MCR) methodology that is ecofriendly and adhering to green chemistry principles, occurring by catalyst-free in a waterethanol solvent system. The methodology to access novel pyrazoles (4a-4j) in this study is superior to conventional pyrazole synthesis because it requires harsh reaction conditions and expensive catalysts, which deviates from green chemistry. All synthesized compounds (4a-4j) were fully characterized and confirmed by 1H NMR, 13C NMR, 2D NMR, FTIR and TOF-MS. Antimicrobial study was performed against two Gram-negative and two Gram-positive strains viz. Escherichia Coli (E.Coli), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus Aureus (S. Aureus), and Streptococcus pneumoniae (S. pneumoniae), respectively, and amoxicillin was used as the reference drug. It was found that only 4c and 4j exhibited activity against E. coli and their Minimum Inhibitory Concentration ( MIC) values were 1.38 and 2.50 mg/mL, respectively. In contrast, Amoxicillin displayed a lower MIC value of 0.0306 mg/mL, thereby suggesting that amoxicillin is more effective than the synthesized pyrazoles against E. coli. Pyrazoles 4a, 4d, and 4g showed no antibacterial activity against P. aeruginosa. Compounds 4b, 4c, 4e, 4f, 4h, 4i, and 4j displayed varying MIC values ranging from 0.212 to 0.625 mg/mL against S. aureus, 4i being 0.212 mg/mL the lowest MIC value. Amoxicillin displayed a lower MIC value than all the pyrazoles against P. aeruginosa. Against S. pneumoniae, 4j demonstrated an excellent antibacterial potential with a lower MIC value of 0.0156 mg/mL compared to that of amoxicillin (0.0306 mg/mL). The other pyrazoles displayed marginally higher MIC values than amoxicillin; 4g showed no activity for S. aureus. However, 4i displayed the lowest MIC value, suggesting its potential as an antibacterial agent. It was percieved that the unsubstituted phenyl ring in 4i contributed to its enhanced potency against test bacteria. Molecular docking studies were performed to predict the binding sites and affinities of the pyrazoles, revealing that they primarily target Penicillin Binding Proteins (PBPs) in the test bacteria. Docking scores for E. coli ranged from -6.7 to -7.9 kcal/mol and compound 4f exclusively exhibited the best docking score of -8.1 kcal/mol against E. coli better than amoxicillin’s docked score of -7.0 kcal/mol. Docking scores for P. aeruginosa ranged from - 6.8 to -7.7 kcal/mol. Compounds 4g and 4j displayed the highest negative docking scores of - 7.7 kcal/mol, outperforming amoxicillin thereby suggesting their potential as inhibitors, however 4b and 4f were comparable. Furthermore, in silico simulation, Molecular Dynamics (MD) studies were conducted for 4g and 4j. Docking scores for S. pneumoniae range from - 7.2 to -8.1 kcal/mol. Compound 4j displayed the highest negative docking score. Agreement between docking and in vitro results reinforces 4j as a potential inhibitor. The pyrazoles exhibited docking scores between -5.5 and -6.6 kcal/mol for S. aureus with 4j showing potential as an inhibitor. While lower than other PBPs, some pyrazoles are comparable to amoxicillin. Furthermor, the pyrazoles exhibited LogP (Lipophilicity) values oscillating between 1 and 2.5, indicating better bioavailability. Amoxicillin, partitioned close to an aqueous phase, showed by a negative LogP value of -0.29. Amoxicillin’s LD50 (lethal dose for killing 50% of the bacteria) is 15 g/kg, suggesting non-toxicity orally. Among pyrazoles, only compound 4c shares this safety profile as amoxicillin, qualifying 4c to be an orally administered antibacterial agent. Other pyrazoles fall into toxicity class 4, necessitating alternative administration routes, such as IV (Intravenous) or IM (Intramuscular). All studied compounds showed no affinity for BBB (Blood-Brain Barrier) permeability or P-glycoprotein binding, indicating they can traverse the system without hindrance from nonspecific enzymes or tissues. Compound 4d does not inhibit any CYP (Cytochrome P450) isoenzymes, similar to amoxicillin. Compound 4e selectively inhibits CYP 3A4, relevant for drug metabolism.

Pseudomonas aeruginosaandStaphylococcus aureusare known as important nosocomial infectious agents also their co-infections are commonly seen in some patient groups. It is well known that host factors such as hormones have roles in modulation of growth, pathogenesis and susceptibilities to antimicrobials. In our study, the influences of norepinephrine (NE) and melatonin (MEL) on antibiotic susceptibilities were examined in mono and co-culture conditions. Methicilin resistantStaphylococcus aureus(MRSA) ATCC 43300 andPseudomonas aeruginosaATCC 27853 were investigated to determine the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of ciprofloxacin and gentamicin in the absence/presence of NE (0.0017 and 0.04μg/mL) and MEL (6 and 60 pg/mL) by microdilution method in mono and co-culture. It was found that hormones decreased (among 2-64 fold) MIC and MBC values of both antibiotics for MRSA. However, it was shown that hormones had no effect on MIC values of both antibiotics forP. aeruginosa.MIC and MBC values of both antibiotics for co-culture were found to be reduced compared to monoculture of MRSA; were found to be increased compared to monoculture ofP. aeruginosa.Whereas, hormones decreased MIC values of both antibiotics in co-culture conditions. Our results suggest that both hormones decreased MIC values and it seems that hormones could influence antibiotic susceptibilities in a strain-dependent manner.

bjective: The purpose of this study was to determine the exact values of MBC (Minimum Bactericidal Concentration) and MIC (Minimum Inhibitory Concentration) of beluntas leaf extract against Streptococcus mutans colonies.&#x0D; Material and Methood: This study used Streptococcus mutans ATCC 25175 and ethanol extract of beluntas leaves with concentrations: 250 g/ml, 125 g/ml, 62.5 g/ml, 31.3 g/ml, 15.6 g/ml, 7.8 g /ml, 3.9 g/ml and 1.95μg/ml. This study used two methods, Broth Microdilution and Total Plate Count techniques as the designated method for the purpose of counting bacteria. Furthermore, the data analysis test was carried out to analyze normality using the Kolmogorov-Smirnov test. If the data distribution shows normal, then one way ANOVA parametric test is performed to determine the significance between the beluntas leaf extract and the number of streptococcus mutans bacteria, which will then be further examined using the Post-Hoc Test with the Tuckey method to find out which dataset is the most significantly different in among others.&#x0D; Results: The beluntas leaf extract showed significant bacterial properties against Streptococcus mutans (P-Value = 0.00) which was expressed through definite MBC and MIC values. The results showed that the MIC and MBC values were 62.5 g/ml and 125 g/ml, respectively against Streptococcus mutans colonies.&#x0D; Conclusion: The conclusion of this study was that the ethanol extract of the leaves of beluntas (Pluchea Indica L) showed antibacterial properties as indicated by the MIC value at a concentration of 62.5μg/ml and the MBC at a concentration of 125μg/ml against streptococcus mutans.

Limited data are available regarding the in vitro activity of SPR719, a derivative of benzimidazole, against diverse nontuberculous mycobacteria (NTM) species. We investigated the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of SPR719 against clinical NTM isolates, including clarithromycin- and amikacin-resistant strains. NTM isolates were obtained from patients with NTM-pulmonary disease caused by various NTM species, including Mycobacterium avium complex, M. abscessus (subspecies abscessus and massiliense), M. kansasii, and M. fortuitum. Regardless of clarithromycin or amikacin resistance, the MIC and MBC values of SPR719 were comparable among these major pathogenic NTM species. In over 70% of the isolates, the MIC values were ≤2 μg/mL with MBC values of ≤4 μg/mL. The MIC and MBC values of M. kansasii were relatively lower than those of the other species with little difference between them, demonstrating the bactericidal properties of SPR719. The in vitro activity of SPR719 against major clinical NTM species suggests that SPR719 can serve as a novel treatment option for NTM-pulmonary disease.

The extra-hospital epidemiology of Acinetobacter infections is a subject of debate. In recent years, the prevalence of animal multidrug-resistant Acinetobacter infections has increased considerably. The goal of the present study was to specify Acinetobacter species isolated from laboratory mice and to test them for their antimicrobial susceptibility. During routine microbiological monitoring of laboratory mice, 12 Acinetobacter spp. were isolated. By means of 16S rRNA and rpoB gene sequencing, seven of the isolates were identified as Acinetobacter radioresistens, three isolates belonged to Acinetobacter genomospecies 14BJ, one isolate was classified as Acinetobacter pitii and one as Acinetobacter sp. ANC 4051. The distribution of the minimal inhibitory concentration (MIC) values was uniform for 21 of the 23 antimicrobial agents tested, whereas a broad MIC distribution was recorded for tulathromycin and streptomycin. The MIC values recorded were low for the majority of the antibiotics tested. Nevertheless, very high MIC values, which will probably render a therapeutic approach using these substances unsuccessful, were recorded for florfenicol, tiamulin, tilmicosin and cephalothin in most of the isolates. In conclusion, we document colonization of laboratory mice with different Acinetobacter species, displaying similar antibiotic susceptibility profiles, with possible implications in the Acinetobacter epidemiology as well as in the husbandry and experimentation of the colonized animals.

Eumycetoma is a neglected tropical disease. It is a chronic inflammatory subcutaneous infection characterised by painless swellings which produce grains. It is currently treated with a combination of itraconazole and surgery. In an ongoing clinical study, the efficacy of fosravuconazole, the prodrug of ravuconazole, is being investigated. For both itraconazole and ravuconazole, no clinical breakpoints or epidemiological cut-off values (ECV) to guide treatment are currently available. To determine tentative ECVs for itraconazole and ravuconazole in Madurella mycetomatis, the main causative agent of eumycetoma. Minimal inhibitory concentrations (MICs) for itraconazole and ravuconazole were determined in 131 genetically diverse clinical M. mycetomatis isolates with the modified CLSI M38 broth microdilution method. The MIC distributions were established and used to determine ECVs with the ECOFFinder software. CYP51A sequences were sequenced to determine whether mutations occurred in this azole target gene, and comparisons were made between the different CYP51A variants and the MIC distributions. The MICs ranged from 0.008 to 1mg/L for itraconazole and from 0.002 to 0.125 mg/L for ravuconazole. The M. mycetomatis ECV for itraconazole was 1mg/L and for ravuconazole 0.064 mg/L. In the wild-type population, two CYP51A variants were found for M. mycetomatis, which differed in one amino acid at position 499 (S499G). The MIC distributions for itraconazole and ravuconazole were similar between the two variants. No mutations linked to decreased susceptibility were found. The proposed M. mycetomatis ECV for itraconazole is 1mg/L and for ravuconazole 0.064 mg/L.

Variable tellurite resistance profiles of clinically-relevant Shiga toxin-producing Escherichia coli (STEC) influence their recovery from foodstuffs