Median Minimum Inhibitory Concentration Research Articles

Diagnostic Performance of Genotype MTBDRsl Assay (Version 2) for Detecting 2nd Line Drug Resistance TB Compared to Sensititre MycoTBI MIC in MDR-TB Patients

Objective: The diagnostic test aimed to compare the GenoType MTBDRsl assay (version 2) and minimum inhibitory concentration (MIC) using a Sensititre MycoTBI MIC plate to detect quinolone and aminoglycoside resistance. Materials and Methods: One hundred thirty-three remaining samples from individuals diagnosed with multidrug-resistance tuberculosis (MDR-TB) and having tested positive for TB cultures between September 2016 and August 2021 were included in the present study. Results: The sensitivity, specificity, PPV, and NPV using GenoType MTBDRsl version 2 compared to MIC of levofloxacin at greater than 0.5 μg/mL were 87.5% (95% CI of 67.6 to 97.3), 98.16% (93.5 to 99.8), 91.30% (72.0 to 98.9), and 97.2% (92.2 to 99.4). Similarly, for moxifloxacin at 2 mg/dL or greater for resistance, the values were 95.4% (95% CI of 77.2 to 99.9), 98.2% (93.6 to 99.8), 91.3% (72.0 to 98.9), and 99.0% (95.0 to 100). The sensitivity, specificity, and diagnostic performances of GenoType MTBDRsl version 2 compared to the MIC of amikacin of greater than 4 μg/mL and kanamycin of greater than 5 μg/mL were 100% (95% CI of 54.1 to 100), 99.2% (95.7 to 100), 99.2% (42.1 to 99.6), and 85.7% (97.1 to 100). Two location mutations at D94G and D94 N/Y were related to a high level of fluoroquinolone with median MIC values of 8 μg/mL of levofloxacin and greater than 4 of moxifloxacin. The mutation at C-14T did not cause resistance in phenotypic patterns. Conclusion: GenoType MTBDRsl (version 2) and MIC determination using Sensititre MycoTBI MIC plate are consistent with each other. Keywords: Sensititre MycoTBI MIC plate; MTBDRsl assay (version 2); Quinolone resistance; Aminoglycoside resistance

Non-pathogenic Neisseria species of the oropharynx as a reservoir of antimicrobial resistance: a cross-sectional study.

Commensal Neisseria species of the oropharynx represent a significant reservoir of antimicrobial resistance determinants that can be transferred to Neisseria gonorrhoeae. This aspect is particularly crucial in 'men having sex with men' (MSM), a key population in which pharyngeal co-colonization by N. gonorrhoeae and non-pathogenic Neisseria species is frequent and associated with the emergence of antimicrobial resistance. Here, we explored the antimicrobial susceptibility of a large panel of non-pathogenic Neisseria species isolated from the oropharynx of two populations: a group of MSM attending a 'sexually transmitted infection' clinic in Bologna (Italy) (n=108) and a group of males representing a 'general population' (n=119). We collected 246 strains, mainly belonging to N. subflava (60%) and N. flavescens (28%) species. Their antimicrobial susceptibility was evaluated assessing the minimum inhibitory concentrations (MICs) for azithromycin, ciprofloxacin, cefotaxime, and ceftriaxone using E-test strips. Overall, commensal Neisseria spp. showed high rates of resistance to azithromycin (90%; median MICs: 4.0 mg/L), and ciprofloxacin (58%; median MICs: 0.12 mg/L), whereas resistance to cephalosporins was far less common (<15%). Neisseria strains from MSM were found to have significantly higher MICs for azithromycin (p=0.0001) and ciprofloxacin (p<0.0001) compared to those from the general population. However, there was no significant difference in cephalosporin MICs between the two groups. The surveillance of the antimicrobial resistance of non-pathogenic Neisseria spp. could be instrumental in predicting the risk of the spread of multi-drug resistant gonorrhea. This information could be an early predictor of an excessive use of antimicrobials, paving the way to innovative screening and prevention policies.

Correlation of antifungal susceptibility and sequence types within Cryptococcus neoformans VNI from HIV patients, and ERG11 gene polymorphism.

Here we tested the correlation between minimum inhibitory concentrations (MICs) of major antifungal agents and sequence types (STs) within Cryptococcus neoformans VNI isolates, and explored the ERG11 gene of included strains. We analysed 23 C. neoformans strains categorised into two groups according to the distribution of the ST profile in Kinshasa clinics (Democratic Republic of Congo): major ST [ST93 (n=15)], and less common STs [ST659 (n=2), ST5 (n=2), ST4 (n=1), ST 53 (n=1), ST31 (n=1), and ST69 (n=1)]. The MICs of the major antifungal agents [amphotericin B (AMB), 5-fluorocytosine (5FC) and fluconazole (FCZ)] were determined following EUCAST guidelines. ERG11 gene sequences were extracted from whole genome sequence of the isolates and compared with the wild-type gene sequence of the C. neoformans VNI. Although major ST isolates appeared to have lower median MICs for AMB and 5FU than less common ST isolates (0.50 vs. 0.75mg/L for AMB, 2 vs. 4mg/L for 5FU, respectively), FCZ susceptibility was similar in both groups (4mg/L) (p-value >0.05). The susceptibility profile of C. neoformans strains separately considered did not significantly affect the patients' clinical outcomes (p-value >0.05). Furthermore, two structural modalities of the ERG11 gene were observed: (1) that of the reference gene, and (2) that containing two exonic silent point substitutions, and one intronic point substitution located in a sequence potentially involved in pre-mRNA splicing (c.337-22C>T); with no association with the MICs of the isolates (p-value >0.05). The lack of association/correlation found in this study calls for further investigations to better understand the mechanisms of C. neoformans resistance to antifungal agents.

Antimicrobial Resistance and Molecular Typing of Neisseria gonorrhoeae Isolates From the Eastern Cape Province in South Africa.

There is a paucity of Neisseria gonorrhoeae antimicrobial resistance data from resource-constrained settings because of the lack of diagnostic testing and limited scale of surveillance programs. This study aimed to determine the antimicrobial resistance profile of N. gonorrhoeae in the rural Eastern Cape province of South Africa. Specimens for N. gonorrhoeae culture were obtained from men with urethral discharge and women with vaginal discharge attending primary health care facilities. Direct inoculation of the agar plates was performed followed by culture and drug susceptibility testing using the Etest at the laboratory. Whole-genome sequencing of the isolates was performed to identify resistance-determining variants. One hundred N. gonorrhoeae isolates were obtained. Most strains were nonsusceptible to ciprofloxacin (76%), tetracycline (75%), and penicillin G (72%). The gyrA S91F mutation was present in 68 of 72 ciprofloxacin-resistant isolates (94%), with concurrent parC mutations in 47 of 68 (69%); gyrA I250M was the only mutation in 4 other resistant strains. One azithromycin-resistant isolate was identified with a minimal inhibitory concentration (MIC) of 8.0 mg/L and the 23S rDNA gene mutation C2597T. The median MIC of cefixime was 0.016 mg/L (range, 0.016-0.064 mg/L), and that of ceftriaxone was 0.016 mg/L (range, 0.016 mg/L). Whole-genome sequencing showed 58 sequence types as revealed in N. gonorrhoeae sequence typing for antimicrobial resistance and 70 sequence types in N. gonorrhoeae multiantigen sequence typing. This study confirmed high rates of N. gonorrhoeae antimicrobial resistance to ciprofloxacin, penicillin G, and tetracycline in our setting. The MICs of cephalosporins are reassuring for ceftriaxone use in syndromic treatment regimens, but the identification of azithromycin resistance warrants further attention.

Antibacterial activity and bee-derived protein content of honey as important and suitable complementary tools for the assessment of honey quality

Honey possesses health-promoting properties; however, industrial processing and manipulation of raw honey can harm on its biological activities, including antibacterial activity. Therefore, this study aimed to compare the honey’s antibacterial activity, its total protein content, and the abundance of the most dominant bee-derived proteins in honey between raw (n = 92) and supermarket (n = 17) samples. We showed that tested raw honey samples were much more effective in inhibiting the growth of Staphylococcus aureus, a model bacterium, at a median minimal inhibitory concentration (MIC) value of 4.5 % compared to supermarket honey samples ceasing bacterial growth at median MIC value of 36 %. Moreover, raw honey samples, tested in this study, contained significantly higher amounts of total protein as well as the content of particular bee-derived proteins (major royal jelly protein 1 (MRJP1), glucose oxidase (GOX), and α-glucosidase) in contrast to supermarket honey samples. These data hint that some supermarket honey samples exhibited strikingly low protein content. Furthermore, α-amylase (diastase) from Aspergillus oryzae was found in the supermarket sample characterised with the lowest protein content. Our findings highlight the burning need to refine and monitor the specific quality parameters, ensuring the authenticity of honey and maintaining its reputation as a functional food.

Antifungal Activity of Glucosinolate-Derived Nitriles and Their Synergistic Activity with Glucosinolate-Derived Isothiocyanates Distinguishes Various Taxa of Brassicaceae Endophytes and Soil Fungi.

The glucosinolates of Brassicaceae plants are converted into bioactive isothiocyanates and other volatiles during a challenge by pathogens and other biotic stressors. However, the role of alternative downstream products with weaker potency (e.g., nitriles) is far from being fully understood. This study tested the possible synergistic antifungal interaction between various glucosinolate-derived nitriles and 2-phenylethyl isothiocyanate (PEITC) on 45 fungal strains, including endophytes from horseradish roots (Brassicaceae) and soil fungi, using an airtight system enabling the accurate study of extremely volatile antifungal agents. The median minimal inhibitory concentrations (MICs) were 1.28, 6.10, 27.00 and 49.72 mM for 1H-indole-3-acetonitrile (IAN), 3-phenylpropanenitrile (PPN), 4-(methylsulfanyl)-butanenitrile (MSBN) and 3-butenenitrile (BN, = allyl cyanide), respectively. Thus, nitriles were considerably weaker antifungal agents compared to PEITC with a median MIC of 0.04 mM. For the same nitriles, the median fractional inhibitory concentration indices (FICIs) of the combinations were 0.562, 0.531, 0.562 and 0.625, respectively. Altogether, 47.7%, 56.8%, 50.0% and 27.3% of tested fungal strains showed a synergistic antifungal activity (FICI ≤ 0.5) for the nitrile-isothiocyanate combinations, respectively. Hypocreales strains showed the least sensitivity towards the GSL decomposition products and their combinations. The mean MIC values for PEITC showed 0.0679 ± 0.0358, 0.0400 ± 0.0214, 0.0319 ± 0.0087 and 0.0178 ± 0.0171 mM for Hypocreales, Eurotiales, Glomerellales and Pleosporales, respectively. In addition, nitriles, especially IAN, also showed significant differences. For the same fungi, the median FICI values fell in the ranges of 0.61-0.67, 0.52-0.61, 0.40-0.50 and 0.48-0.67, respectively, depending on the nitrile. Our results suggest that glucosinolate-derived nitriles may enhance isothiocyanate antifungal activity and that they may play an active role in shaping the plant microbiome and contribute to the filtering of microbes by plants.

The inhibitory effect of copper, zinc, and manganese on Legionella longbeachae and other Legionella spp. in vitro.

Legionella longbeachae is an important cause of Legionnaires' disease in Australasia and is associated with exposure to potting soils. Our aim was to identify ways to reduce the load of L. longbeachae in potting soils. Inductively-coupled plasma optical emission spectrometry (ICP-OES) of an all-purpose potting mix showed copper (Cu) concentrations (mg/kg) range from 15.8 to 23.6. Zinc (Zn) and manganese (Mn) were significantly higher than Cu ranging from 88.6-106 to 171-203, respectively. Minimal inhibitory and bactericidal concentrations of 10 salts used in the horticultural industry were determined for Legionella species in buffered yeast extract (BYE) broth. For L. longbeachae (n=9) the median (range) minimum inhibitory concentration (MIC) (mg/L) of copper sulfate was 31.25 (15.6-31.25), zinc sulfate 31.25 (7.81-31.25), and manganese sulfate 31.25 (7.81-62.5). The MIC and minimum bactericidal concentration (MBC) were within one dilution of each other. Susceptibility to Cu and Zn salts increased as the concentration of pyrophosphate iron in the media decreased. The MIC values for these three metals against Legionella pneumophila (n=3) and Legionella micdadei (n=4) were similar. Combinations of Cu, Zn, and Mn were additive. Legionella longbeachae has similar susceptibility to Cu and other metal ions in comparison to L. pneumophila.

Filter sterilized carcass rinsate for recovery of Salmonella species with various concentrations of cetylpyridinium chloride.

Controlling Salmonella in poultry processing continues to be important to processors and consumers. Cetylpyridinium chloride (CPC) has proven to be effective in vitro in controlling Salmonella. This study evaluated the recovery of Salmonella after overnight storage in 4°C filter-sterilized carcass rinsate containing CPC from 0.44 to 909 ppm (μg/mL). Ten Salmonella serotypes (18 strains), of which 6 serotypes are commonly isolated from poultry products, were grown in Bacto-Tryptic Soy Broth overnight at 37°C. Serial dilutions of a CPC/propylene glycol solution were prepared in 24-well tissue culture plates containing filter-sterilized carcass rinsate. Approximately 107 cfu/mL of each Salmonella serotype was added to the appropriate wells. Inoculated plates were stored overnight at 4°C. After storage, triplicate plates of brilliant green agar with sulfapyridine (BGS) were surface inoculated with 10 μL of the contents for each well, streaked for isolation, and incubated at 37°C for 24 h. Three replications were conducted. The presence of typical colonies on BGS plates was recorded as growth and verified through biochemical and serological testing. Of the serotypes chosen, Salmonella Kentucky, Dublin, and Enteritidis were the least resistant to CPC with a median minimum inhibitory concentration (MIC) of 14.22 μg/mL (range from 3.55 to 56.88 μg/mL); S. Typhimurium demonstrated a median MIC of 114.00 μg/mL (range from 28.44 to 114.00 μg/mL). Residual CPC potentially remaining attached to a carcass or in the weep after processing could potentially alter which Salmonella serotype is recovered from a carcass rinse due to different growth patterns during regulatory testing, with a potential for more virulent strains not to be recovered.

Antimicrobial Effect of Oxazolidinones and Its Synergistic Effect with Bedaquiline Against Mycobacterium abscessus Complex.

Unsatisfactory efficacies of currently recommended anti-Mycobacterium abscessus complex (MABC) treatment regimens have led to development of novel drugs to combat MABC infections. In this study, we evaluated in vitro antimicrobial activities of bedaquiline (BDQ) and four oxazolidinones against MABC isolates. The resazurin microplate assay was performed to determine minimum inhibitory concentrations (MICs) of BDQ and four oxazolidinones, including tedizolid (TZD), sutezolid (SZD), delpazolid (DZD), and linezolid (LZD), against 65 MABC isolates. A checkerboard method was used to investigate efficacies of various antimicrobial drug combinations. BDQ MICs for MABC isolates ranged from <0.031 to 1 µg/mL, while MIC50 and MIC90 values were 0.125 µg/mL and 0.25 µg/mL, respectively. TZD MIC50 and MIC90 values for MABC isolates were 1 µg/mL and 4 µg/mL, respectively, which were fourfold lower than corresponding LZD values (P < 0.001). DZD MIC90 values for MABC isolates was 8 µg/mL, which were 0.5-fold lower than corresponding LZD values (P < 0.01). MICs of BDQ, SZD, and LZD for M. abscessus subspecies massiliense isolates were significantly lower than corresponding MICs for M. abscessus subspecies abscessus isolates (P < 0.05). Notably, use of oxazolidinones (DZD, SZD, LZD, or TZD) with BDQ against MABC isolates led to reduction of the oxazolidinone median MIC range from 4 to 0.125 µg/mL to 1-0.031 µg/mL. These results demonstrated excellent BDQ inhibitory activity against MABC isolates. TZD exhibited stronger antimicrobial efficacy against MABC isolates as compared to efficacies of DZD, SZD, and LZD. Importantly, MICs of oxazolidinones were markedly decreased when they were combined with BDQ, thus suggesting that combinations of BDQ and oxazolidinones may be effective treatments for MABC infections.

Analysis of fks1 and fks2 gene mutations in invasive Candida glabrata strains from Pakistan.

The gradual increase in caspofungin usage in Pakistan raises a concern of emergence of echinocandin resistance in local Candida glabrata strains. We sequenced and determined mutations in fks1 and fks2 genes in invasive Candida glabrata strains from Pakistan. Thirty-six invasive C.glabrata strains were selected with median (min-max) minimum inhibitory concentrations (MICs) of 0.06 (0.015-0.25)mg/L for caspofungin, 0.015 (0.008-0.06)mg/L for micafungin and 0.06 (0.015-0.12)mg/L for anidulafungin. fks1 and fks2 gene fragments were sequenced using Sanger methodology. Sequences were analysed with MEGA-6 software to identify specific single-nucleotide polymorphisms (SNP) against wild-type sequences of C.glabrata. In fks1 gene, non-synonymous mutation D632H was observed in one isolate with caspofungin MIC of 0.25 mg/L. Synonymous mutation at position A742 was observed in 26/36 (72%) of the isolates. 34/36 (94.5%) isolates analysed for fks2 gene were observed as wild type. A novel non-synonymous mutation at I661T was observed in fks2 gene in one isolate with caspofungin MIC of 0.12 mg/L and anidulafungin and micafungin MIC of 0.06 and 0.015 mg/L, respectively. Novel fks2 synonymous mutations at position T647, K652 and I706 were observed in 16/36 (44%), 25/36 (69%) and 23/36 (63%) isolates, respectively. Low frequencies of both non-synonymous and synonymous polymorphisms were observed in invasive C.glabrata strains. Since S663P in fks2 gene is associated with caspofungin resistance, a novel mutation at 661 codon identified in our study needs correlation with treatment outcome data and mandates periodic genomic surveillance.

Resistance profiles of Neisseria gonorrhoeae isolates in Vienna, Austria: a phenotypic and genetic characterization from 2013 to 2020

International surveillance data show a constant rise in the number of Neisseria gonorrhoeae infections and an increase in drug resistance of N. gonorrhoeae. As recent N. gonorrhoeae surveillance data in Austria are scarce, this study investigated phenotypic and genotypic antimicrobial resistance in N. gonorrhoeae isolates. In total, 440 N. gonorrhoeae samples were collected at the Medical University of Vienna, and the minimal inhibitory concentrations (MICs) for a range of different antibiotics were determined. Sampling sites and treatments were recorded, and whole-genome sequencing of N. gonorrhoeae isolates was performed using allele libraries to determine genotypic resistance. The median MICs for ceftriaxone, cefixime, azithromycin, ciprofloxacin, tetracycline and penicillin were <0.002 µg/mL, <0.016 µg/mL, 0.25 µg/mL, 2.0 µg/mL, 1.5 µg/mL and 0.25 µg/mL, respectively. Annual comparison showed that MICs were generally stable for all antimicrobial agents except azithromycin, for which an increase in median MIC was observed from 2017 (0.25 µg/mL). There was no genetic resistance to ceftriaxone; 8% of samples displayed resistance mutations against cefixime, primarily located in the penA gene. Resistance to azithromycin increased from 2% in 2013 to 12% in 2020. MtrD mosaic had the highest impact on azithromycin susceptibility; 47% of the resistant isolates showed this mutation. The majority of cases of gonorrhoea were treated successfully with either ceftriaxone or a ceftriaxone/azithromycin regime. Two treatment failures occurred under monotherapy with doxycycline. Overall, genotypic resistance corresponded significantly to all respective MICs. The resistance rate of N. gonorrhoeae to antibiotics has remained stable in Vienna over the last decade, except for azithromycin. The strong correlation found between genetic and phenotypic patterns in this study holds promise for future diagnostics of N. gonorrhoeae resistance based on genotypes.

Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii in the United States, 2013-2017.

Healthcare-associated carbapenem-resistant Acinetobacter baumannii (CRAB) infections are a serious threat associated with global epidemic clones and a variety of carbapenemase gene classes. In this study, we describe the molecular epidemiology, including whole-genome sequencing analysis and antimicrobial susceptibility profiles of 92 selected, nonredundant CRAB collected through public health efforts in the United States from 2013 to 2017. Among the 92 isolates, the Oxford (OX) multilocus sequence typing scheme identified 30 sequence types (STs); the majority of isolates (n = 59, 64%) represented STs belonging to the international clonal complex 92 (CC92OX). Among these, ST208OX (n = 21) and ST281OX (n = 20) were the most common. All isolates carried an OXA-type carbapenemase gene, comprising 20 alleles. Ninety isolates (98%) encoded an intrinsic OXA-51-like enzyme; 67 (73%) harbored an additional acquired blaOXA gene, most commonly blaOXA-23 (n = 45; 49%). Compared with isolates harboring only intrinsic oxacillinase genes, acquired blaOXA gene presence was associated with higher prevalence of resistance and a higher median minimum inhibitory concentration to the carbapenem imipenem (64 μg/mL vs. 8 μg/mL), and antibiotics from other drug classes, including penicillin, aminoglycosides, cephalosporins, and polymyxins. These data illustrate the wide distribution of CC92OX and high prevalence of acquired blaOXA carbapenemase genes among CRAB in the United States.

Eumycetoma causative agents are inhibited in vitro by luliconazole, lanoconazole and ravuconazole.

IntroductionEumycetoma is a subcutaneous mutilating disease that can be caused by many different fungi. Current treatment consists of prolonged itraconazole administration in combination with surgery. In many centres, due to their slow growth rate, the treatment for eumycetoma is often started before the causative agent is identified. This harbours the risk that the causative fungus is not susceptible to the given empirical therapy. In the open‐source drug program MycetOS, ravuconazole and luliconazole were promising antifungal agents that were able to inhibit the growth of Madurella mycetomatis, the most common causative agent of mycetoma. However, it is currently not known whether these drugs inhibit the growth of other eumycetoma causative agents.Materials and methodsHere, we determined the in vitro activity of luliconazole, lanoconazole and ravuconazole against commonly encountered eumycetoma causative agents. MICs were determined for lanoconazole, luliconazole and ravuconazole against 37 fungal isolates which included Madurella species, Falciformispora senegalensis, Medicopsis romeroi and Trematosphaeria grisea and compared to those of itraconazole.ResultsRavuconazole, luliconazole and lanoconazole showed high activity against all eumycetoma causative agents tested with median minimal inhibitory concentrations (MICs) ranging from 0.008–2 µg/ml, 0.001–0.064 µg/ml and 0.001–0.064 µg/ml, respectively. Even Ma. fahalii and Me. romeroi, which are not inhibited in growth by itraconazole at a concentration of 4 µg/ml, were inhibited by these azoles.ConclusionThe commonly encountered eumycetoma causative agents are inhibited by lanoconazole, luliconazole and ravuconazole. These drugs are promising candidates for further evaluation as potential treatment for eumycetoma.

Minimum Contact Time of 1.25%, 2.5%, 5%, and 10% Benzoyl Peroxide for a Bactericidal Effect Against Cutibacterium acnes.

PurposeBenzoyl peroxide (BPO) is an effective acne treatment and has been used as a cleanser and short contact therapy. However, data on the minimum contact time of BPO needed to kill Cutibacterium acnes are lacking. Thus, the aim of this study was to determine the minimum contact time of commonly used BPO concentrations for bactericidal effects on C. acnes.Materials and MethodsAn in vitro experimental study of clinically isolated C. acnes was performed to determine the minimal inhibitory concentration (MIC) of BPO using the broth microdilution method. Subsequently, the minimum contact times of various concentrations of BPO were evaluated, and their bactericidal effects were assessed by the plate count method.ResultsThe median MIC of BPO was 9375 µg/mL, which did not significantly differ between antibiotic-resistant and nonresistant C. acnes. The minimum contact time of BPO with C. acnes was significantly different among the BPO concentrations. For bactericidal activity against all isolates, 1.25%, 2.5%, 5%, and 10% BPO required 60 min, 15 min, 30 sec, and 30 sec, respectively.ConclusionBPO demonstrated bactericidal activity against both antibiotic-resistant and antibiotic-susceptible C. acnes. The in vitro contact time needed to kill C. acnes was almost immediate with 5% or more BPO, but ≤ 2.5% BPO required longer contact times for bactericidal effects.

Automated Susceptibility Testing With Vitek 2 Compared to MicroScan Reduces Vancomycin Alternative Therapy For Methicillin-Resistant Staphylococcus Aureus Bacteremia

Variability in minimum inhibitory concentration (MIC) with automated susceptibility testing instruments may influence methicillin-resistant Staphylococcus aureus (MRSA) treatment. The purpose of this study was to evaluate the difference in vancomycin MIC values and the impact on vancomycin alternative therapy for MRSA bacteremia using the MicroScan and VITEK 2 automated systems. This was a retrospective multicenter cohort study of adult patients with MRSA bacteremia. Patients were stratified by susceptibility testing with MicroScan (May 2013-December 2016) or VITEK 2 (June 2017-February 2020). The primary outcome was vancomycin alternative therapy use. Secondary endpoints included MRSA MIC, 30-day mortality, 30- and 90-day readmission, and hospital length of stay (LOS). A total of 193 patients were included for analysis: 89 in the MicroScan group and 104 in the VITEK 2 group. Vancomycin alternative therapy use was higher in the MicroScan group than the VITEK 2 group (56.2% vs 20.2%; p <0.001). Median MIC value was 2 mg/L and 1 mg/L for MicroScan and VITEK 2, respectively (p <0.001). Median hospital LOS was shorter in the VITEK 2 period (16 vs 12 days; p=0.02). Thirty-day mortality (10.1% vs 7.7%; p=0.555) and 90-day readmission (34.8% vs 29.8%; p=0.457) did not significantly differ between MicroScan and VITEK 2 groups. VITEK 2 use was associated with lower reported vancomycin MICs and less use of vancomycin alternative therapy.

β-Lactam Resistance in Upper Respiratory Tract Pathogens Isolated from a Tertiary Hospital in Malaysia.

The rise of antimicrobial resistance (AMR) among clinically important bacteria, including respiratory pathogens, is a growing concern for public health worldwide. Common causative bacteria for upper respiratory tract infections (URTIs) include Streptococcus pneumoniae and Haemophilus influenzae, and sometimes Staphylococcus aureus. We assessed the β-lactam resistant trends and mechanisms of 150 URTI strains isolated in a tertiary care hospital in Kuala Lumpur Malaysia. High rates of non-susceptibility to penicillin G (38%), amoxicillin-clavulanate (48%), imipenem (60%), and meropenem (56%) were observed in S. pneumoniae. Frequent mutations at STMK and SRNVP motifs in PBP1a (41%), SSNT motif in PBP2b (32%), and STMK and LKSG motifs in PBP2x (41%) were observed in S. pneumoniae. H. influenzae remained highly susceptible to most β-lactams, except for ampicillin. Approximately half of the ampicillin non-susceptible H. influenzae harboured PBP3 mutations (56%) and only blaTEM was detected in the ampicillin-resistant strains (47%). Methicillin-susceptible S. aureus (MSSA) strains were mostly resistant to penicillin G (92%), with at least two-fold higher median minimum inhibitory concentrations (MIC) for all penicillin antibiotics (except ticarcillin) compared to S. pneumoniae and H. influenzae. Almost all URTI strains (88–100%) were susceptible to cefcapene and flomoxef. Overall, β-lactam antibiotics except penicillins remained largely effective against URTI pathogens in this region.

Minimum inhibitory concentrations of commercial essential oils against common chicken pathogenic bacteria and their relationship with antibiotic resistance.

AimsWe investigated the antibacterial effect of seven essential oils (EOs) and one EO‐containing liquid phytogenic solution marketed for poultry and pigs (‘Product A’) on chicken pathogens, as well as the relationship between minimum inhibitory concentration (MIC) in EOs and antibiotics commonly administered to chicken flocks in the Mekong Delta (Vietnam).Methods and ResultsMicellar extracts from oregano (Origanum vulgare), cajeput (Melaleuca leucadendra), garlic (Allium sativum), black pepper (Piper nigrum), peppermint (Mentha × piperita L.), tea tree (Melaleuca alternifolia), cinnamon (Cinnamomum zeylanicum) EOs and Product A were investigated for their MIC against Avibacterium endocarditidis (N = 10), Pasteurella multocida (N = 7), Ornitobacterium rhinotracheale (ORT) (N = 10), Escherichia coli (N = 10) and Gallibacterium anatis (N = 10). Cinnamon EO had the lowest median MIC across strains (median 0.5 mg/ml [IQR, interquartile range 0.3–2.0 mg/ml]), followed by Product A (3.8 mg/ml [1.9–3.8 mg/ml]), oregano EO (30.4 mg/ml [7.6–60.8 mg/ml]) and garlic 63.1 mg/ml [3.9 to >505.0 mg/ml]. Peppermint, tea tree, cajeput and pepper EOs had all MIC ≥219 mg/ml. In addition, we determined the MIC of the 12 most commonly used antibiotics in chicken flocks in the area. After accounting for pathogen species, we found an independent, statistically significant (p < 0.05) positive correlation between MIC of 10 of 28 (35.7%) pairs of EOs. For 67/96 (69.8%) combinations of EOs and antibiotics, the MICs were correlated. Of all antibiotics, doxycycline was positively associated with the highest number of EOs (peppermint, tea tree, black pepper and cajeput, all p < 0.05). For cinnamon, the MICs were negatively correlated with the MICs of 11/12 antimicrobial tested (all except colistin).ConclusionsIncreases in MIC of antibiotics generally correlates with increased tolerance to EOs. For cinnamon EO, however, the opposite was observed.Significance and Impact of the StudyOur results suggest increased antibacterial effects of EOs on multi‐drug resistant pathogens; cinnamon EO was particularly effective against bacterial poultry pathogens.

Detection of Cross-Resistance Between Methotrexate and Azoles in Candida albicans and Meyerozyma guilliermondii: An In Vitro Study

Abstract In recent years, there has been a rapid increase in the incidence of Candida infections. The different species of the genus Candida vary in their virulence abilities and susceptibility to antifungal agents, depending on several external factors. The result of such modifications may be cross-resistance, which is understood as an acquired resistance to a certain antimicrobial agent after exposure to another drug. The aim of this study was to determine the possibility of cross-resistance between fluconazole, voriconazole, itraconazole, and methotrexate in Candida albicans and Meyerozyma guilliermondii (syn. Candida guilliermondii ). Fifteen strains of M. guilliermondii and eight strains of C. albicans , including the standard strains, were tested. For all strains, the minimum inhibitory concentrations (MICs) for fluconazole, voriconazole, and itraconazole were determined before and after stimulation with methotrexate. The median MICs in M. guilliermondii before and after stimulation were 9.333 and 64 mg/L ( p = 0.005) for fluconazole; 0.917 and 1.667 mg/L ( p = 0.001) for itraconazole, respectively. No significant change in MIC was observed for voriconazole. For C. albicans strains, the median MICs before and after stimulation were 0.917 and 64 mg/L ( p = 0.012) for fluconazole; 0.344 and 1.135 mg/L ( p = 0.018) for voriconazole, respectively. There was no significant change in MIC values for itraconazole. Thus, this study demonstrates the presence of cross-resistance between voriconazole, itraconazole, fluconazole, and methotrexate for the selected strains. Methotrexate exposure induces different responses when certain drugs are used for various species. Therefore, if a patient was previously exposed to methotrexate, there may be a higher risk of treatment failure with fluconazole than with other azoles such as voriconazole for fungemia caused by M. guilliermondii or itraconazole for C. albicans infection.

Is gentamicin a viable therapeutic option for treating resistant Neisseria gonorrhoeae in New South Wales?

The key issues with Neisseria gonorrhoeae infections, in Australia and elsewhere, are coincident increases in disease rates and in antimicrobial resistance (AMR), although these factors have not been shown to be correlated. Despite advances in diagnosis, control of this disease remains elusive, and incidence in Australia continues to increase. Of the Australian jurisdictions, New South Wales (NSW) has the highest N. gonorrhoeae notifications, and over the five-year period 2015-2019, notifications in NSW have increased above the national average (by 116% versus 85%, respectively). Gonococcal disease control is reliant on effective antibiotic regimens. However, escalating AMR in N. gonorrhoeae is a global health priority, as the collateral injury of untreated infections has substantive impacts on sexual and newborn health. Currently, our first-line therapy for gonorrhoea is also our last line, with no ideal alternative identified. Despite some limitations, gentamicin is licensed and readily available in Australia, and is proposed for treatment of resistant N. gonorrhoeae in national guidelines; however, supportive published microbiological data are lacking. Analysis of gonococcal resistance patterns within Australia for the period 1991-2019, including 35,000 clinical isolates from NSW, illustrates the establishment and spread of population-level resistance to all contemporaneous therapies. An analysis of gentamicin susceptibility on 2,768 N. gonorrhoeae clinical isolates from NSW, for the period 2015-2020, demonstrates that the median minimum inhibitory concentration (MIC) for gentamicin in NSW has remained low, at 4.0 mg/L, and resistance was not detected in any isolate. There has been no demonstration of MIC drift over time (p = 0.91, Kruskal-Wallis test), nor differences in MIC distributions according to patients' sex or site of specimen collection. This is the first large-scale evaluation of gentamicin susceptibility in N. gonorrhoeae in Australia. No gentamicin resistance was detected in clinical isolates, 2015-2020, hence this is likely to be an available treatment option for resistant gonococcal infections in NSW.

310. The Impact of Microscan versus Vitek-2 for Automated Susceptibility Testing on the Utilization of Vancomycin Alternatives for the Treatment of Methicillin-Resistant Staphylococcus aureus Bacteremia

BackgroundAutomated susceptibility testing (AST) provides minimum inhibitory concentrations (MIC) to guide effective antibiotic therapy. AST is critical for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, as susceptible MIC values ≥ 1.5 µg/mL are associated with vancomycin (VAN) failure. The Microscan (MS) instrument may report elevated MIC values compared to Vitek-2 (VTK), thus impacting treatment. This study aimed to evaluate the impact of MS versus VTK on VAN alternative use in the treatment of MRSA bacteremia in a Texas health system.MethodsThis was a retrospective cohort study of patients admitted to the Ascension Seton health system in Austin, TX. Patient eligibility included: age ≥18 years, ≥1 positive MRSA blood culture, ≥72 hours of MRSA therapy, and VAN use within 48 hours of positive culture. Patients were stratified into the MS group (May 2013-Dec 2016) and VTK group (Jun 2017-Mar 2020). The primary outcome was therapy switch from VAN to VAN alternatives. Secondary endpoints include S. aureus MIC, 30-day all-cause mortality, 30 and 90-day readmission, and length of hospital stay (LOS). Outcomes were compared between groups using appropriate bivariable comparisons, as well as multivariable logistic regression and propensity score-adjusted logistic regression.ResultsA total of 199 patients were included: 91 in the MS group and 108 in the VTK group. Switch to VAN alternative was 56% vs. 19% (p< 0.0001) for MS and VTK, respectively. The median (interquartile range) MIC value reported was 2 μg/mL (2 – 2) and 1 μg/mL (0.5 – 1) for MS and VTK, respectively (p< 0.0001). Thirty-day readmission (19% vs. 20%, p=0.7647) and 30-day mortality (10% vs. 9%, p=0.5262) were comparable between MS and VTK groups, respectively. Hospital LOS significantly decreased in the VTK period (16 days vs. 12 days, p=0.0153). The MS group was the only independent positive predictor of VAN alternative therapy: logistic regression, OR 5.64 (95% CI 1.67–18.99) and propensity score adjusted, OR 4.21 (95% CI 1.32–13.48).ConclusionSince implementation of VTK from MS, Ascension Seton hospitals experienced a decreased median VAN MIC for MRSA bacteremia as well as therapy switches from VAN to VAN alternatives without affecting other patient health outcomes.Disclosures All Authors: No reported disclosures