Mean Minimum Inhibitory Concentration Research Articles

Antimicrobial activity of Southern African medicinal plants on Helicobacter pylori and Lactobacillus species

Ethnopharmacological relevanceNumerous medicinal plants have been used traditionally in South Africa for gastric ulcer treatment. Helicobacter pylori is known for causing inflammation and the onset of gastric ulcers. While several studies explored medicinal plants against H. pylori, investigation of medicinal plants used for gastric ulcers has been neglected, as well as the effects these plants would have on bacteria occurring naturally in the gut microbiome. Aim of the studyThis study aimed to investigate Southern African medicinal plants used traditionally for treating gastric ulcers against H. pylori , as well as the effects that these plants have when combined with Lactobacillus species and tested against H. pylori. MethodologyBased on evidence from the ethnobotanical literature, 21 plants were collected. Their antimicrobial activity was assessed against five clinical H. pylori strains, and in combination with each of three Lactobacillus species, using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) broth microdilution assays. Toxicity was assessed using the brine shrimp lethality assay. ResultsNoteworthy activity was observed against at least one H. pylori strain for 12 plant species. The lowest mean MICs were from organic extracts of Carissa edulis Vahl (0.18 mg/mL) and Chironia baccifera L. (0.20 mg/mL), and aqueous extracts of Sansevieria hyacinthoides (L.) Druce (0.26 mg/mL) and Dodonaea viscosa Jacq. (0.30 mg/mL). Aqueous extracts of the investigated plants were combined with Lactobacillus species, and the majority of combinations showed increased antimicrobial activity compared with the extracts alone. Combinations of Lactobacillus rhamnosus with 18 of the 21 aqueous plant extracts showed at least a two-fold decrease in the mean MBC against all H. pylori strains tested. Lactobacillus acidophilus combined with either Protea repens L., Carpobrotus edulis (L.) L. Bolus or Warburgia salutaris (Bertol.f.) Chiov. aqueous extracts had the best anti-H. pylori activity (mean MBCs of 0.10 mg/mL for each combination). Only four organic and one aqueous extract(s) were considered toxic. ConclusionThese results highlight the potential of medicinal plants to inhibit H. pylori growth and their role in traditional treatments for the management of ulcers. The results also indicate that aqueous extracts of these plants do not hinder the growth of bacteria that occur naturally in the gut microbiome and play a role in maintaining gut health, as well as show the potential benefit of including Lactobacillus species as potentiators of H. pylori activity.

The fly route of extended-spectrum-β-lactamase-producing Enterobacteriaceae dissemination in a cattle farm: from the ecosystem to the molecular scale

IntroductionThis study aimed to understand the origin and to explain the maintenance of extended-spectrum β-lactamase (ESBL) Enterobacteriaceae isolated from food-producing animals in a third-generation cephalosporin (3GC)-free farm.MethodsCulture and molecular approaches were used to test molecules other than 3GC such as antibiotics (tetracycline and oxytetracycline), antiparasitics (ivermectin, flumethrin, fenbendazol, and amitraz), heavy metal [arsenic, HNO3, aluminum, HNO3, cadmium (CdSO4), zinc (ZnCl2), copper (CuSO4), iron (FeCl3), and aluminum (Al2SO4)], and antioxidant (butylated hydroxytoluene) as sources of selective pressure. Whole-genome sequencing using short read (Illumina™) and long read (Nanopore™) technologies was performed on 34 genomes. In silico gene screening and comparative analyses were used to characterize the genetic determinants of resistance, their mobility, and the genomic relatedness among isolates.ResultsOur analysis unveiled a low diversity among the animal ESBL-producing strains. Notably, E. coli ST3268 was recurrently isolated from both flies (n = 9) and cattle (n = 5). These E. coli ST3268/blaCTX-M-15/blaTEM-1B have accumulated multiple plasmids and genes, thereby representing a reservoir of resistance and virulence factors. Our findings suggest that flies could act as effective mechanical vectors for antimicrobial gene transfer and are capable of transporting resistant bacteria across different environments and to multiple hosts, facilitating the spread of pathogenic traits. A significantly higher mean minimum inhibitory concentration of oxytetracycline (841.4 ± 323.5 mg/L vs. 36.0 ± 52.6 mg/L, p = 0.0022) in ESBL E. coli than in non-ESBL E. coli and blaCTX-M-15 gene overexpression in oxytetracycline-treated vs. untreated ESBL E. coli (RQOxy = 3.593, p = 0.024) confirmed oxytetracycline as a source of selective pressure in ESBL E. coli.DiscussionThe occurrence of ESBL E. coli in a farm without 3GC use is probably due to an as yet undefined human origin of Enterobacteriaceae blaCTX-M-15 gene transmission to animals in close contact with cattle farm workers and the maintenance of the local ESBL E. coli reservoir by a high fly diversity and oxytetracycline selective pressure. These findings highlight the critical need for stringent vector control to mitigate antimicrobial resistance spread for preserving public health. Addressing this issue necessitates a multifaceted approach combining microbial genetics, vector ecology, and farm management practices.

In Vitro Assessment of Antifungal and Antibiofilm Efficacy of Commercial Mouthwashes against Candida albicans.

Candida albicans is the most critical fungus causing oral mycosis. Many mouthwashes contain antimicrobial substances, including antifungal agents. This study aimed to investigate the in vitro activity of 15 commercial mouthwashes against 12 strains of C. albicans. The minimal inhibitory concentrations (MICs), minimal fungicidal concentrations (MFCs), and anti-biofilm activity were studied. MICs were determined by the micro-dilution method using 96-well plates, and MFCs were determined by culturing MIC suspensions on Sabouraud dextrose agar. Anti-biofilm activity was evaluated using the crystal violet method. The mouthwashes containing octenidine dihydrochloride (OCT; mean MICs 0.09-0.1%), chlorhexidine digluconate (CHX; MIC 0.12%), and CHX with cetylpyridinium chloride (CPC; MIC 0.13%) exhibited the best activity against C. albicans. The active compound antifungal concentrations were 0.5-0.9 µg/mL for OCT products and 1.1-2.4 µg/mL for CHX rinses. For mouthwashes with CHX + CPC, concentrations were 1.56 µg/mL and 0.65 µg/mL, respectively. Products with polyaminopropyl biguanide (polyhexanide, PHMB; MIC 1.89%) or benzalkonium chloride (BAC; MIC 6.38%) also showed good anti-Candida action. In biofilm reduction studies, mouthwashes with OCT demonstrated the most substantial effect (47-51.1%). Products with CHX (32.1-41.7%), PHMB (38.6%), BAC (35.7%), Scutellaria extract (35.6%), and fluorides + essential oils (33.2%) exhibited moderate antibiofilm activity. The paper also provides an overview of the side effects of CHX, CPC, and OCT. Considering the in vitro activity against Candida albicans, it can be inferred that, clinically, mouthwashes containing OCT are likely to offer the highest effectiveness. Meanwhile, products containing CHX, PHMB, or BAC can be considered as promising alternatives.

Antimicrobial activity of selected nutraceutical plants used in Northern Uganda

Background: Nutraceutical plants (NP) play a vital role as supportive treatment with antiretroviral drugs (ARVs). However, there is limited  scientific evidence on the efficacy of NP to justify their extensive use. This study aimed to evaluate the antibacterial activity of three nutraceutical plants which are commonly used as antimicrobials.
 Methodology: Leaves of Cajanus cajan L. Millsp. and Eucalyptus globulus Labill., and stem bark of Mangifera indica L. were collected from  Northern Uganda. The three samples of each NP were extracted with acetone and the minimum inhibitory concentration (MIC) values of  the extracts against Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa and Klebsiella pneumoniae were determined using the serial broth microdilution technique [1]. The mean MIC values of the extracts against each bacterial species were  recorded.
 Results: The three NP extracts were active against all the four bacteria species with MIC ranging from 0.08 to 2.5 mg/ml. The extract of  Cajanus cajan was very active against Klebsiella pneumoniae with the lowest recorded MIC value of 0.08 mg/ml. The extract of Mangifera  indica bark was very active against Pseudomonas aeruginosa with the lowest MIC of 0.08 mg/ml.
 Conclusion: The results of the present  study support the traditional use of the nutraceutical plants as antimicrobials. 

In-vitro Antimicrobial Effects and Phytochemical Contents of Stingless Bee Meliponula beccarii Honey and Pollen from Baringo County, Kenya

Background: Afro-tropical stingless bees produce several products including honey, propolis, cerumen and pollen, which are widely used as traditional medicine and food. In Baringo County, Kenya stingless bee honey in particular is widely used as a traditional remedy for respiratory disorders, stomach disorders and oral thrush, commonly associated with bacterial and fungal infections. However, scientific data on the antimicrobial activities and phytochemical content of stingless bee products from Baringo is scarce. Objectives: The objective of this study was to investigate the in vitro antimicrobial activities and phytochemical content of Meliponula beccarii stingless bee honey and pollen from Baringo County. Materials and methods: Eleven honey and pollen samples were conveniently sampled from eleven wild occurring stingless bee nests in three ecologically distinct areas. Increasing concentrations of honey and pollen samples were then prepared and tested against H. influenzae, E. coli, MRSA and C. albicans using agar well diffusion assay. The broth microdilution test was further performed to determine the Minimum Inhibitory Concentrations (MICs) and Minimum Bactericidal Concentrations (MBCs). Standard qualitative methods were used to analyse the phytochemical contents of the honey and pollen samples. Data was analysed by two-way ANOVA and Tukey’s post-hoc tests. Results: in comparison to distilled water (negative control), the honey samples had a significantly higher mean zones of inhibition at concentration of 100% v/v against E. coli (9.0±4.7 mm vs 0 mm, p<0.0001, N=11), H. influenzae (11.1±5.0 mm vs 0 mm, p<0.0001, N=11), and MRSA (10.8±5.9 mm vs 0 mm, p>0.0001, N=11). However, compared to ciprofloxacin standard (30ug/ml), all the concentrations of honey samples had significantly lower mean zones of inhibition against H. influenzae (8.8±2.4 mm vs 25±0.58 mm, p<0.0001, N=11), E. coli (5.7±3.4 mm vs 31.7±1.5 mm, p<0.0001, N=11) and MRSA (8.1±2.8 mm vs 27±0 mm). All the honey samples did not exhibit activity against C. albicans even at 100% (v/v). The mean MICs against E. coli, H. influenzae and MRSA were 9.38% (v/v), 18.75% (v/v) and 18.75% (v/v), respectively. Notably, the honey samples exhibited bactericidal activity, only against MRSA with a mean MBC of 60.94% (v/v). All the pollen samples showed no antibacterial and antifungal activities against the tested micro-organisms. Qualitative analyses revealed that the honey and pollen samples of Meliponula beccarii contain alkaloids, phenolics, triterpenoids, flavonoids, saponins, tannins, glycosides and steroids, but not terpenoids. Conclusion: Some but not all Meliponula beccarii honey samples from Baringo County has antibacterial activities. The honey and pollen are rich in various phytochemical compounds. Our findings validate the use of Meliponula beccarii honey in traditional treatment of bacterial infections and its further investigation as a potential source of novel agents against drug resistant pathogenic bacteria.

Anti-fungal Activity of 4 Herbal Mouthwashes vs. Chlorhexidine Against Candida albicans and C. glabrata: A Preliminary Study

Anti-fungal Activity of 4 Herbal Mouthwashes vs. Chlorhexidine Against Candida albicans and C. glabrata: A Preliminary Study

Bioactivities and Phenolic Profiles of Honeys Derived from Plants of the Goldfields, Esperance and Wheatbelt Regions of Western Australia.

The aim of this study was to examine a collection of 79 honeys derived from plants endemic to several Western Australian unique bioregions for bioactivity and physicochemical characteristics. For physicochemical analyses, total phenolic content, high performance thin layer chromatography (HPTLC) fingerprints, pH, Brix, colour and hydrogen peroxide generation were examined. Brix (82.6±1.3) and pH (4.34±0.24) values were within expected ranges, whereas hydrogen peroxide levels determined using an o-dianisidine/horseradish peroxidase assay were relatively low, ranging from 0-244 μM. Antibacterial activity determined by the broth microdilution assay showed that Moort (Eucalyptus platypus) and Yate (Eucalyptus occidentalis) honeys had the highest overall activity with mean minimum inhibitory concentrations of 24.8 % and 25.1 % (w/v) honey, respectively. Yate honey also had the highest overall antioxidant activity (4.38±0.58 mmol Fe2+ /kg of honey), followed by Mallee honeys from various eucalypts, as determined by FRAP (Ferric reducing antioxidant power) and DPPH⋅ (2,2-Diphenyl-1-picrylhydrazyl) assays. This study identified new sources of honeys with potentially useful therapeutic properties from bioregions within Western Australia.

682. Novel rpoB mutations and trends in clinical Clostridioides difficile isolates with reduced fidaxomicin susceptibility

Abstract Background Fidaxomicin use is increasing to treat Clostridioides difficile infection (CDI) following clinical treatment guideline updates placing it as first-line therapy. This puts a selection pressure on the development of fidaxomicin resistance, which has been associated with in vitro fitness costs compared to wildtype isolates. Here we aimed to assess the epidemiology of reduced susceptibility (RS) to fidaxomicin and prevalence of rpoB mutations in a clinical cohort. Methods Stool samples from patients with CDI were collected from two different healthcare systems in Houston, TX between 2016-21. Fidaxomicin minimum inhibitory concentrations (MIC) were determined via agar dilution susceptibility testing following CLSI standards. RS was defined as MIC > 0.5 mg/L based on the EUCAST [T]ECOFF. A subgroup of 40 isolates with RS underwent Sanger sequencing to detect rpoB single nucleotide polymorphisms (SNPs). Results Of 535 patients included, 114 (21.3%) had infecting strains with fidaxomicin RS (MIC50 = 0.5 mg/L, MIC90 = 1.0 mg/L). Fidaxomicin RS was more common in RT 027 (49.4%, 41/83) compared to non-027 strains (16%, 68/425; P < 0.001). There were no differences in the proportions demonstrating RS across collection years (P=0.18) or based on location in or out of the Texas Medical Center (P=0.29). Mean MICs were similar between isolates collected before and after the IDSA/SHEA guideline update in 2018 (P =0.1). rpoB SNP mutations were detected in 12.5% (5/40) of isolates at 7 novel base positions; no SNPs were detected at previously reported position 3428. Conclusion RS to fidaxomicin occurred in one fifth of clinical isolates with no changes in incidence between 2016-21. Several new rpoB SNPs were observed in isolates with RS. Studies are needed to determine potential association(s) between fidaxomicin exposure and MIC changes. Disclosures Anne J. Gonzales-Luna, PharmD, BCIDP, Cidara Therapeutics: Grant/Research Support|Ferring Pharmaceuticals: Personal Fees|Paratek Pharmaceuticals: Grant/Research Support|Seres Therapeutics: Grant/Research Support Kevin Garey, PharmD, MS, BCIDP, Acurx Pharmaceuticals: Grant/Research Support|Cidara Therapeutics: Grant/Research Support|Ferring Pharmaceuticals: Advisor/Consultant|Paratek Pharmaceuticals: Grant/Research Support|Seres Therapeutics: Grant/Research Support|Vedanta Therapeutics: Grant/Research Support

Synergistic Antibacterial Efficacy of Melittin in Combination with Oxacillin against Methicillin-Resistant Staphylococcus aureus (MRSA).

Methicillin-resistant Staphylococcus aureus (MRSA) often cause infections with high mortality rates. Antimicrobial peptides are a source of molecules for developing antimicrobials; one such peptide is melittin, a fraction from the venom of the Apis mellifera bee. This study aimed to evaluate the antibacterial and antibiofilm activities of melittin and its association with oxacillin (mel+oxa) against MRSA isolates, and to investigate the mechanisms of action of the treatments on MRSA. Minimum inhibitory concentrations (MICs) were determined, and synergistic effects of melittin with oxacillin and cephalothin were assessed. Antibiofilm and cytotoxic activities, as well as their impact on the cell membrane, were evaluated for melittin, oxacillin, and mel+oxa. Proteomics evaluated the effects of the treatments on MRSA. Melittin mean MICs for MRSA was 4.7 μg/mL and 12 μg/mL for oxacillin. Mel+oxa exhibited synergistic effects, reducing biofilm formation, and causing leakage of proteins, nucleic acids, potassium, and phosphate ions, indicating action on cell membrane. Melittin and mel+oxa, at MIC values, did not induce hemolysis and apoptosis in HaCaT cells. The treatments resulted in differential expression of proteins associated with protein synthesis and energy metabolism. Mel+oxa demonstrated antibacterial activity against MRSA, suggesting a potential as a candidate for the development of new antibacterial agents against MRSA.

Antibacterial activity of <i>Citrullus lanatus</i> seed extract against clinical isolates of <i>Klebsiella pneumoniae</i> and <i>Staphylococcus aureus</i>

As a result of increased emergence of bacterial resistance to the conventionally used antibiotics, it is necessary to search for alternatives from other sources like plant materials. This study was aimed at evaluating the in vitro antibacterial activity of Citrullus lanatus seed extract against isolates of Klebsiella pneumoniae from urine and Staphylococcus aureus from wound. The seeds were extracted using distilled water and methanol via cold maceration and then analysed for the presence of phytochemicals using standard methods. Tannins, steroids, cardiac glycosides and carbohydrates were present in both extracts. Only the aqueous extract contained alkaloids. The antibacterial activity of the two extracts was determined by agar well diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using broth dilution method. The aqueous extract had better activity than the methanol extract, having inhibition zones of 20 mm and 23 mm at 200 mg/mL and, 10 mm and 11 mm at 25 mg/mL against Klebsiella pneumoniae isolates respectively, and mean zone of inhibition between 27.50 mm to 29.33 mm at 200 mg/mL and, 16.50 mm to 17.33 mm at 25 mg/mL against Staphylococcus aureus isolates with MIC and MBC values of 0.195 mg/mL and 0.39 mg/mL against Klebsiella pneumoniae and, mean MIC and MBC values ranging from 0.30 mg/mL to 0.39 mg/mL and 0.78 mg/mL to 2.73 mg/mL against Staphylococcus aureus isolates. The results obtained reveal the potential use of Citrullus lanatus seeds in the development of standard antibiotics.

Activity of Cefotaxime versus Ceftriaxone against Pathogens Isolated from Various Systemic Infections: A Prospective, Multicenter, Comparative, In vitro Indian Study

Abstract Objectives To determine the susceptibility of isolated pathogens with different samples collected from patients taking cefotaxime as compared with ceftriaxone. Methods In vitro susceptibility study was conducted at microbiology laboratories of east (Bhubaneshwar), west (Ahmedabad), north (Delhi), and south (Srikakulam) India. Samples of treatment naïve patients with various clinical infections were included if they were positive for bacterial culture. Minimum inhibitory concentration (MIC) and zone of inhibitions (ZoIs) for each isolate were determined using Ezy MIC strip test and disk diffusion methods, respectively. Findings of MIC and ZoI were interpreted as per the Clinical and Laboratory Standards Institute guidelines. Appropriate statistical tests were used. Results Four hundred clinical samples of urinary tract infection (42.75%), lower respiratory tract infection (20.75%), skin and soft tissue infection (16.75%), and sepsis (12.75%) were evaluated. Escherichia coli (47.75%) was the most common organism isolated followed by Klebsiella (26%), Salmonella (7.75%), and Proteus mirabilis (3.75%). The mean MIC values for E. coli, Klebsiella, Staphylococcus, Citrobacter koseri, and Serratia marcescens were found to be lower when treated with cefotaxime compared with ceftriaxone, although the difference was not statistically significant. However, cefotaxime produced significantly (p < 0.05) more ZoI for E. coli, Klebsiella, and Salmonella as compared with ceftriaxone. Conclusion Cefotaxime has shown better sensitivity profile in terms of MIC and ZoI to most of the isolated organisms as compared with ceftriaxone and thus can be preferred for empirical treatment of such patients.

Isoniazid resistance-conferring mutations are associated with highly variable phenotypic resistance

BackgroundHigh-dose isoniazid is recommended in the 9–12 months short-course regimen for multidrug-resistant tuberculosis with inhA mutation. However, there is insufficient evidence to support the assumption of genotypic-phenotypic concordance. This study aimed to identify the genetic mutations associated with high-level phenotypic isoniazid resistance. MethodsClinical isolates from patients with drug-resistant tuberculosis were profiled by whole-genome sequencing and subjected to minimum inhibitory concentration (MIC) testing using MGIT based-method. MICs were performed in concentration ranges based on the mutation present: isolates with no isoniazid resistance-conferring mutations and H37Rv, 0.016–0.256 µg/ml; inhA, 0.256–4.0 µg/ml, katG 1.0–16.0 µg/ml; and inhA + katG, 4.0–64.0 µg/ml. Isolates demonstrating resistance at the upper limit of the concentration range were tested up to the maximum of 64.0 µg/ml. Bootstrap of the mean MICs was performed to increase the robustness of the estimates and an overlap index was used to compare the distributions of the MICs for each mutation profile. ResultsA total of 52 clinical isolates were included in this analysis. Bootstrap MIC means for inhA, katG and inhA + katG were 33.64 (95% CI, 9.47, 56.90), 6.79 (4.45, 9.70) and 52.34 (42.750, 61.66) µg/ml, respectively. There was high overlap between inhA and inhA + katG mutations (eta = 0.45) but not with inhA and katG (eta = 0.19). Furthermore, katG showed poor overlap with inhA + katG mutations (eta = 0.09). Unexpectedly, 4/8 (50.0%) of all InhA mutants demonstrated high-level resistance, while 20/24 (83.3%) of katG mutants demonstrated moderate-level resistance. ConclusionsInhA mutations demonstrated unexpectedly high MICs and showed high overlap with inhA + katG. Contrary to the common belief that katG mutants are associated with high-level resistance, this mutation primarily showed moderate-level resistance.

The Antimicrobial Properties of Malaysian Propolis as Intracanal Medicament in Endodontics

Numerous studies have shown that propolis, from the sting and stingless bees, possessed antimicrobial, antifungal, antidiabetic, antitumoral and antioxidant properties. Propolis produced by stingless bees, Heterotrigona itama, also possessed these properties but in varying intensity. Exploiting this natural product with antimicrobial properties against Enterococcus faecalis (EF), would be advantageous in endodontics. Particularly where the current synthetic medicament, calcium hydroxide (Ca(OH)2), failed to remove these bacteria, predominantly found in failed root canal-treated (RCT) teeth. The aims of this study are to determine the antimicrobial properties of Malaysian propolis (MP) against Enterococcus faecalis and to compare the antibacterial effect of MP with Ca(OH)2 as an intra-canal medicament. Raw propolis was purchased from Humaira Honey Sdn Bhd, Lenggong, Perak and the ethanolic extraction method was carried out until lyophilization. Antimicrobial susceptibility testing (AST) was done on five samples, namely, MP, Ca(OH)2, 2% chlorhexidine (CHX), 70% ethanol, and sterile normal saline (SDW), where CHX, 70% ethanol and SDW as controls. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) methods were carried out. The MIC and MBC for MP and CHX were done using the micro-dilution method on 96-well, while Ca(OH)2 were performed using the serial macro-dilution method. The results were analysed by Kruskal Wallis test with Mann-Whitney posthoc test and repeated-measures ANOVA with Bonferroni post hoc test (p <0.05). The mean MIC from three trials that were carried out on the samples was CHX (<0.008%) < MP (0.03%) < Ca(OH)2 (0.62%). While the MBC values for three trials were found to be CHX (0.011%) < MP (0.07%) < Ca(OH)2 (1.25%). In conclusion, MP was shown to be antibacterial and effective against Enterococcus faecalis and is more effective when compared to Ca(OH)2, which is commonly used as an intra-canal medicament. Further research is needed to test MP’s clinical efficacy.

High Prevalence of Antiseptic Resistance Encoding Genes and Reduced Phenotypic Antiseptic Susceptibility Among Antibiotic-Resistant Pseudomonas aeruginosa Isolates

Background: Multi-drug resistant (MDR) and extensively drug-resistant (XDR) Pseudomonas aeruginosa isolates are of clinical concern. Objectives: To determine the distribution of antiseptic resistance genes and the associated level of phenotypic antiseptic resistance against quaternary ammonium compounds and biguanide compounds, we studied MDR and XDR P. aeruginosa isolates collected from different infections among patients from a single hospital. Methods: Pseudomonas aeruginosa isolates were investigated in 2020 for in vitro susceptibility to benzethonium chloride (BTC), benzalkonium chloride (BKC), and chlorhexidine digluconate (CHG). The minimum inhibitory concentrations (MICs) against these antiseptic agents were determined using broth microdilution. Also, polymerase chain reaction (PCR)-mediated detection of qacE, qacEΔ1, and blaOXA-23 genes was used. Results: Isolates were largely non-clonal according to their phenotypical and genotypical non-similarity (35 overall data-combination types detected). Most P. aeruginosa infections occurred in intensive care unit (ICU) patients (n = 43, 61.4%). Extensively drug-resistant and MDR phenotypes were detected in 20% and 12.6%, respectively. Among the 70 isolates retained, 53 (75.7%) harbored at least one resistance gene, comprising 11 (20.7%) isolates with solely the qacEΔ1 gene; seven (13.2%) isolates harbored the qacE gene. Both the qacE and qacEΔ1 genes were detected simultaneously in 35 (66%) isolates. The mean MICs for BTC (24.0 versus 10.56 µg/mL), BKC (46.1 versus 17.22 µg/mL), and CHG (107.7 versus 29.4 µg/mL) were statistically significantly higher among antiseptic resistance gene harboring isolates than in other isolates without such genes. Conclusions: The significantly increased MICs against antiseptic agents among antibiotic-resistant P. aeruginosa isolates highlight the importance of monitoring such increases and implementing effective infection control.

In vitro antimicrobial activity of crude propolis extracts and fractions.

The search for antimicrobials in propolis presents a new dimension for addressing the problem of antimicrobial drug resistance. The aim of this study was to determine the antimicrobial activity of extracts of crude propolis collected from different regions in Ghana and their active fractions. The antimicrobial activity of the extracts, as well as that of the chloroform, ethyl acetate, and petroleum ether fractions of the active samples were determined using the agar well diffusion method. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the most active fractions were determined. The various crude propolis extracts frequently produced zones of inhibition against Staphylococcus aureus (17/20) than Pseudomonas aeruginosa (16/20), and Escherichia coli (1/20) test isolates. Chloroform and ethyl acetate solvents produced fractions possessing greater antimicrobial activity than the petroleum ether fraction. The mean MIC range of the most active fractions was greatest for S. aureus (76.0 ± 34.8-48.0 ± 33.0mg/ml) than for P. aeruginosa (40.8 ± 33.3-30.4 ± 6.7mg/ml) and E. coli, as was the mean MBC. Propolis has antimicrobial potential, and hence should be exploited as an alternative for the treatment of bacterial infections.

Antifungal activity of miltefosine against both azole-susceptible and -resistant Aspergillus strains

Miltefosine, an alkylphosphocholine, has been approved recently for the treatment of visceral leishmaniasis. Miltefosine has shown promise as a treatment for paracoccidioidomycosis, and has mixed activity against other fungi and yeast. There are limited data on the in-vitro activity of miltefosine against azole-resistant and -susceptible Aspergillus spp. As such, the aim of this study was to determine the in-vitro activity of miltefosine against Aspergillus strains. Miltefosine was tested against 108 azole-susceptible and -resistant Aspergillus strains isolated from Iran and other countries using the broth microdilution method. Miltefosine was found to be effective against azole-resistant Aspergillus isolates, with minimum inhibitory concentrations (MICs) ranging from 1.562 to 6.25 µg/mL. MIC50 and MIC90 were 1.562 and 3.125 µg/mL, respectively. Miltefosine had a higher geometric mean MIC (2.459 µg/mL) for wild-type Aspergillus isolates than itraconazole (0.220 µg/mL) and voriconazole (0.298 µg/mL). No significant difference was found between miltefosine MICs for azole-resistant Aspergillus isolates and azole-susceptible Aspergillus isolates (P>0.05). Miltefosine appears to have good in-vitro activity against azole-resistant Aspergillus strains, according to these findings. Furthermore, the findings suggest that miltefosine could be used to treat infections caused by azole-resistant Aspergillus spp.

Atividade inibitória in vitro de óleos essenciais derivados de especiarias para Aspergillus fumigatus multirresistente obtido de ração de aves

ABSTRACT Aspergillus fumigatus is a respiratory pathogen, which has the potential to cause brooder pneumonia in poultry chicks and aspergillosis in birds and farmers. Frequent and irrational use of antifungals has led to the development of resistance in the fungal species. The present study aimed to evaluate the antifungal activity of essential oils (EOs) from four different spices against multi-drug resistant (MDR) A. fumigatus isolated from 40 poultry feed samples. Twenty fungal isolates were identified to be A. fumigatus based on the macroscopic and microscopic characteristics, which were confirmed by targeting and amplifying the species-specific rodA gene (313 bp). Five (5/20) isolates were found to be MDR by the disk diffusion method. EOs were tested as an alternative strategy for 5 MDR isolates of A. fumigatus. Clove EO provided better activity by 6 log10 reduction for 30-90 min exposure as compared to other EOs, therefore, shortlisted for well-diffusion and minimum inhibitory concentration (MIC) method. Clove EO provided promising results as compared to fluconazole, amphotericin B, ketoconazole, nystatin and voriconazole as its mean ZOI (39.6 ± 6.34) were better than all other commercial antifungals (p< 0.001). Mean MIC was reported to be 0.195 ± 0.11 µl/ml. Safety testing of the EO produced 74-82% cell viability for the range of 0.390 - 0.097 µl/ml as compared to DMSO. Findings of the present study highlight that clove EO can be source of a good therapeutic agent for infections of MDR isolates of A. fumigatus.

Feasibility and Efficacy Study of Spices in Meat Preservation

The systematic application of spices as natural food preservatives could be the key to withstanding different food-borne diseases and the frequent use of antibiotics could be reduced thereby. Eight indigenous spices were tested against six food-borne pathogens. The spice extracts were prepared by drying, grinding, and soaking into 95% ethanol and the antibacterial activity was evaluated by the well-diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by the broth dilution method. The feasibility of spices as natural meat preservatives was then assessed through the application. The ethanol extracts of the spices potentially inhibited the test organisms. Maximum activity (zone of inhibition- ZOI) was recorded for garlic (17.83±2.48 mm) followed by black pepper (17±8.9 mm), black cumin (15.83±10.87 mm), and ginger (15.16±7.68 mm). For pathogens, the most susceptible was B. cereus (19.57±8.05 mm) followed by Acinetobacter sp. (18.14±1.34 mm), E. coli (16.28±1.88 mm), S. aureus (14.28±9.91 mm), V. cholerae (10.85±7.94 mm) and Salmonella enterica ser. Typhi (6.85±8.55 mm). Garlic exhibited the most effective and consistent inhibitory activity whereas black cumin exhibited the highest activity against B. cereus (34 mm). These results were highly comparable to the commercial antibiotics, e.g. Meropenem (28 mm). Against the Salmonella spp., ginger, cumin, and garlic demonstrated moderate inhibition (16 mm) whereas complete resistance was observed against other spices. The lowest MIC and MBC were recorded for black cumin against B. cereus (32 mg/ml and 64 mg/ml, respectively). But garlic was found to be the best candidate due to its lowest mean MIC (85.33±33 mg/ml), and MBC (170.66±66 mg/ml). Black cumin, garlic, and black pepper were efficient in reducing the total viable count of meat at 72 hours and hence could be developed as natural food preservatives. Stamford Journal of Microbiology, Vol.12 (1) 2022: 31-36

406. Vancomycin Activity against Clostridioides difficile Over Three Decades in Chicago

Abstract Background In 2017, the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiologist of America (SHEA) updated the C. difficile (CD) treatment guidelines recommending vancomycin as the preferred therapy for C. difficile infections (CDI). We assessed the in vitro vancomycin minimum inhibitory concentration (MIC) against CD across three decades to determine if the vancomycin MIC had increased since these guidelines were published. Methods We performed antimicrobial agar dilution susceptibility testing on 89 clinically relevant CD isolates collected within Chicagoland area. These isolates were selected from 3 separate timeframes: 2005 – 2007, 2013 – 2015, and 2021. Isolates were selected based on the prevalence of restriction endonuclease analysis (REA) strain types within each time cohort. Treatment response to vancomycin was reviewed for patients from the 2021 cohort if CD isolates had a vancomycin MIC of ≥ 16 μg/ml. Results The in vitro vancomycin geometric mean MIC against all 89 CD isolates was 2.53 μg/ml with a MIC50 of 2 μg/ml and MIC90 of 4 μg/ml. Comparing the 3 timeframes, the geometric mean vancomycin MICs from 2005-2007, 2013-2015, and 2021 were 2.35, 2.27, and 2.91, respectively (p=0.11). Comparison of the isolates collected from 2005 – 2015 to 2021, the in vitro vancomycin geometric mean MICs were 2.31 and 2.91, respectively (p = 0.037). REA group BI was the most common strain group to have an increased in vitro vancomycin MIC within the 2021 cohort as 4 of the 5 isolates tested had a MIC of 16 μg/ml. All 4 of the patients infected with these strains with an elevated vancomycin MICs were treated vancomycin. All 4 patients had a resolution of symptoms on vancomycin and 2 suffered from a recurrent infection within ≤4 weeks of completing vancomycin. Conclusion The vancomycin MIC against CD has trended upwards slightly over the past 20 years. The most notable change occurred between 2015 and 2021. We hypothesize that this increase is due to increased use of oral vancomycin for the treatment of CDI. However, these data indicate that most isolates still have a MIC of ≤4 μg/ml and an elevated MIC does not appear to impact clinical outcomes. Further study is required to determine if this upward trend in vancomycin MIC continues and if this could have any potential clinical implications. Disclosures Stuart Johnson, M.D., Ferring Pharmaceuticals: Membership on Ferring Publication Steering Committee|Ferring Pharmaceuticals: Employee|Summit Plc: Advisor/Consultant.

In Vitro Antifungal Susceptibility of Candida Albicans Isolated from Yemeni Patients with Denture Stomatitis

Background and aims: Candida-associated denture stomatitis (CADS) is a common fungal infection in people who wear dentures. The main objectives of this study were to identify the causative agents of CADS and in vitro antifungal susceptibility testing (AFST) for Candida albicans in Yemeni patients with denture stomatitis. Methods: A total of 88 Candida spp. obtained from patients with denture stomatitis. Candida spp were identified using standard microbiological methods. The in-vitro antifungal susceptibility of Candida albicans. to fluconazole (FCZ), itraconazole (ICZ), voriconazole (VCZ), and amphotericin B (AMB) was evaluated using the E test strips. Interpretive sensitivity criteria for antifungal breakpoints were adapted from the Clinical and Laboratory Standards Institute (CLSI). Results: Overall, C. albicans was the most commonly isolated species (𝑛 = 60; 68.2%), followed by C. glabrata (𝑛 = 9; 10.2%), C. tropicalis (𝑛 = 7; 8%), and C. parapsilosis (𝑛 = 3; 3.4%). Voriconazole had the lowest geometric mean minimum inhibitory concentration which was 0.0418 𝜇g/ml for MIC50, and 0.957 𝜇g/ml for MIC90; followed by amphotericin B (AMB) in which MIC50 was 0.518 𝜇g/ml and for MIC90 was 1.06 𝜇g/ml. Conclusion: Our study showed that Candida albicans was the most prevalent Candida species in Yemeni patients with CADS and was susceptible to both azoles and amphotericin B. In addition, voriconazole could be a suitable alternative to antifungal agents currently used in the treatment of CADS, as well as in the treatment of recurrent Candidasis.