Minimum Inhibitory Concentration Range Research Articles

Determination of chemical compositions and antibacterial effects of selected essential oils against human pathogenic strains.

Increasing the rates of drug resistant bacteria, having adverse effects and also high costs of antibiotics lead to essential oils (EOs) with antibacterial properties have gained importance. The present study was predicted to evaluate antibacterial activity of cinnamon, lavender, tea tree, lemon, coconut, oregano, mint, laurel and eucalyptus EOs alone and in combination. Chemical components of effective EOs were examined through gas chromatography/mass spectrometry (GC/MS). Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays were used to identify antibacterial effects of EOs against bacterial strains. The Fractional Inhibitory Concentration index (FICI) of the binary combinations of EOs was determined by checkerboard method. Carvacrol, linalool, linalyl acetate, 1,8-cineole, cinnamaldehyde, terpinen-4-ol and p-cymene were found main components of EOs. Oregano, cinnamon and tea tree EOs exhibited the strongest antibacterial activity with the MIC range between 0.03125-1.00% (v/v). Tea tree/lavender and cinnamon/lavender mixtures showed a synergistic effect against Streptococcus pyogenes and Streptococcus agalactiae. Oregano with tea tree and laurel exhibited a synergistic effect against Staphylococcus aureus. Oregano showed a synergistic effect when combined with cinnamon, lavender and tea tree against S.agalactiae. Our findings indicated that EOs either alone or in combination against pathogens should be preferred as potential antibacterial agents.

Antifungal Susceptibility Testing of Five Antifungal Agents against Clinically Isolated Dermatophytes Species from a Tertiary Care Hospital in Northern India

Introduction: Dermatophytosis form approximately 15-75% of all the mycological infections. Dermatophytes are closely related keratinolytic fungi with ability to degrade keratin and invade the skin, hair and nails causing dermatophytosis. Aim: To evaluate the Minimum Inhibitory Concentration (MIC) of antifungal drug against the isolated dermatophytes by broth microdilution method. Materials and Methods: The present cross-sectional study was conducted in the Department of Microbiology, Muzaffarnagar Medical College, Muzaffarnagar, Uttar Pradesh, India. The duration of the study was August 2018-August 2020. A 10-20% KOH mount was prepared from the skin scrapings, nail clippings, and hair bits to look for fungal elements. The specimens were also inoculated on Mycosel media and Sabouraud Dextrose Agar (SDA) with chloramphenicol. The dermatophytes were identified on the basis of colony characteristics, Lacto Phenol Cotton Blue (LPCB) mount, nutritional requirement, temperature tolerance, urease production, and in-vitro hair perforation test. Antifungal susceptibility testing was done for all fungal isolates and performed by broth microdilution method. The descriptive statistics were reported as means with their Standard Deviation (SD). Data were statistically evaluated with International Business Machines (IBM) Statistical Package for the Social Sciences (SPSS) Statistics for Mac, Version 25.0., IBM Corp., Chicago IL. Results: In this study, the MIC range for all the 165 isolates for dermatophytes tested for antifungal susceptibility showed that itraconazole, terbinafine and voriconazole showed the lowest MIC range of 0.0019-0.5 μg/mL followed by griseofulvin and fluconazole at MIC range of 0.125-32 μg/mL. The MIC50 of itraconazole and terbinafine was seen lowest at 0.0313 μg/mL followed by voriconazole at 0.0625 μg/mL, griseofulvin at 0.25 μg/mL for all isolated dermatophytes. Highest MIC50 with 4 μg/ mL was found for fluconazole against T. mentagrophytes and T. violaceum. MIC90 of terbinafine, itraconazole and voriconazole was seen lowest at 0.25 μg/mL followed by griseofulvin at 1 μg/ mL for all isolated dermatophytes. Highest MIC90 of fluconazole was recorded at 16 μg/mL for all isolated dermatophytes. Conclusion: Highest MIC50 with 8 μg/mL was found for fluconazole against all isolated dermatophytes. MIC90 of terbinafine, itraconazole and voriconazole was seen lowest at 0.25 μg/mL followed by gresiofulvin at 1 μg/mL for all isolated dermatophytes. Highest MIC90 of fluconazole was recorded at 16 μg/mL for all isolated dermatophytes.

Antimicrobial activity of Rhus Coriaria L. and Salvia Urmiensis bunge against some food-borne pathogens and identification of active components using molecular networking and docking analyses

This research aimed to evaluate the in vitro antibacterial activity of methanol extracts of Rhus coriaria L. (sumac) and Salvia urmiensis Bunge against some food-borne pathogens, survey the phytochemical constituents of the extracts, and their activity against some drug targets in pathogens. The antibacterial activity of the extracts was evaluated against six pathogens using agar well diffusion and broth microdilution methods. Both extracts exhibited antibacterial activity and the highest activity was obtained by sumac against Staphylococcus aureus (27.7 ± 0.8 mm). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of sumac against tested bacteria were in the range of 0.125-0.5 and 0.25-1 mg/mL, respectively. S. urmiensis showed weaker antimicrobial activity with a MIC range of 2-4 mg/mL. A molecular networking analysis of extracts resulted in annotation of 18 and 12 compounds from the methanol extracts of S. urmiensis and sumac respectively, which mainly were related to flavonoids. Molecular docking analysis could effectively characterize some glycosylated flavonoids with a high binding affinity to the studied enzymes. This study confirmed the efficacy of sumac and S. urmiensis extracts as natural antimicrobial agents and introduced a wide range of compounds, which can be used in food preservation to control foodborne pathogens in food.

Comparison of Vancomycin MICs by Broth Microdilution Method, E-Test and Vitek 2C among MRSA Isolates in Tertiary Care Centre, Hyderabad, India

Introduction: The most important pathogen isolated from Skin and Soft Tissue Infections (SSTIs) is a Gram positive organism, Staphylococcus aureus (S.aureus). Wide range of emerging Methicillin Resistant Staphylococcus aureus (MRSA) infections is leading to global threat causing Community Acquired-MRSA (CA-MRSA) or Hospital Acquired MRSA (HA-MRSA). Minimum Inhibitory Concentration (MIC) is done to ensure that antibiotics are chosen efficiently in the clinical settings by Vitek 2, Epsilometer- test (E-test) and Broth Microdilution (BMD) method. Aim: To determine the clinical spectrum of MRSA and comparison of Vancomycin MICs obtained by E-test, Vitek 2C and BMD method. Materials and Methods: This was a cross-sectional study that was conducted at Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India during the period of November 1st 2019 to December 31st, 2020 from Inpatient Department (IPD) and Outpatient Department (OPD). Among 464 SSTIs, 132 were S.aureus, out of which 38 isolates were MRSA. Identification and sensitivity of the isolates such as pus, wound swabs, and tissues were identified through Vitek 2 compact system. Statistical analysis of the demographic and clinical characteristics was represented as frequency and percentages. Results: A total of 464 SSTIs, S.aureus were 132 of which MRSA were 38 (29%) and Methicillin sensitive Staphylococcus aureus (MSSA) were 94 (71%) with male predominance of 29 (76.3%) with MRSA. Most of the patients were in the age group of 21- 30 years (26%). Amongst the total 38 patients analysed,25 were from IPD and 13 were from OPD. A 23/38 wound swabs (60%) 12/38 of pus (28%) and 3/38 (7%) were tissues. The predominant risk factor observed was Surgical Site Infections (SSI) in 19 cases (50%) followed by prior antibiotic therapy in 17 (44%) cases. The median duration of hospitalisation was 31.5 days. Vancomycin susceptibility by all three methods with an MIC range of 0.5-2μg/ ml by all three methods, except for one isolate where the MIC was >32ug/ml by Vitek 2C and 8 ug/mL by E-test, which was sensitive by BMD with an MIC of 0.25 μg/mL. Conclusion: Implementing infection control practices and controlling the risk factors will help in management of MRSA infections. Drug resistance to Glycopeptides can be avoided by regular screening of vancomycin creeps by different susceptibility methods in order to avoid treatment failures.

Detection of Heteroresistant Vancomycin-Intermediate Staphylococcus aureus among Methicillin-Resistant Staphylococcus aureus

Background: The testing of heteroresistance vancomycin-intermediate Staphylococcus aureus (hVISA) by the population analysis profile-area under the curve (PAP-AUC) is tedious and laborious. The goal of this study was to determine the prevalence of hVISA among methicillin-resistant S. aureus (MRSA) and compare two screening tests: brain heart infusion agar with vancomycin 4 mg/L (BHIV4) and macromethod E-test (MET) with PAP-AUC as the gold standard. Materials and Methods: Antibiotic sensitivity test and detection of MRSA were performed according to the CLSI guidelines. PAP-AUC, BHIV4, and MET were used to detect hVISA. Results: A total of 288 MRSA isolates were tested for hVISA, with 48 (16.66%) being detected by PAP-AUC. With PAP-AUC, BHIV4's sensitivity, specificity, positive predictive value, and negative predictive value were 70.83%, 96.66%, 80.95%, and 94.3%, respectively. The majority of hVISA isolates were found in the vancomycin minimum inhibitory concentration range 1–2 mg/L. Conclusions: hVISA was found to be 16.6% in this investigation. When compared to MET, BHIV4 had a higher sensitivity, and teicoplanin and linezolid were found to be the most effective drug against hVISA.

1256. Clinical Response by Minimum Inhibitory Concentrations in Carbapenem-Resistant Pseudomonas aeruginosa Infections under Cefiderocol Compassionate Use Program

BackgroundCefiderocol (CFDC) has been developed for the treatment of serious infections caused by drug-resistant aerobic Gram-negative pathogens, including carbapenem-resistant (CR) Pseudomonas aeruginosa (CRPA). The current CFDC susceptibility breakpoints for P. aeruginosa differ between US Food and Drug Administration (FDA) and Clinical and Laboratory Standards Institute (CLSI) (Table). Data characterizing the impact of CFDC minimum inhibitory concentrations (MICs) on the clinical responses of patients treated with CFDC for CRPA are sparse.MethodsWe reviewed patients treated with compassionate-use CFDC (2 g, q8h or renally adjusted dosages) for infections caused by CRPA with no alternative treatment options. CFDC minimum inhibitory concentrations (MICs) were evaluated according to CLSI guidelines in iron-depleted cation-adjusted Müller–Hinton broth for available CRPA isolates. We then assessed physician-reported clinical responses to CFDC therapy and stratified results by CFDC MIC. ResultsThere were 71 patients overall with CRPA treated with CFDC. Treatment duration ranged from 1 to 132 days. For the subset of 33 patients for whom CFDC MIC values were available, the most common infection sites were the respiratory tract (n=15), blood (n=12), and urinary tract (n=4). Patients could have had an infection at ≥1 sites and in other locations. CFDC MIC range was ≤0.03– >64 µg/mL. The modal MIC value was 2 µg/mL (n=13; Table). CRPA isolates were susceptible to CFDC in 13/33 patients (39.4%) based on the FDA breakpoint (MIC ≤1 µg/mL) and in 31/33 patients (93.9%) based on the CLSI breakpoint (MIC ≤4 µg/mL). Clinical response was reported for 15/18 patients (83.3%) who had infections with CFDC MICs of 2–4 µg/mL, organisms that are considered susceptible by CLSI but not by FDA breakpoints (Table). Clinical response was reported in 6/13 patients (46.1%) with infections with CFDC MIC ≤1 µg/mL and in 1 of 2 patients (50.0%) with CFDC MIC ≥8 µg/mL (Table). 21 (63.6%) patients survived to Day 28 and there were no trends in mortality by CFDC MIC. ConclusionClinical response rate was high for CRPA infections with CFDC MICs of 2–4 µg/mL, supporting the higher CLSI susceptibility breakpoint.Disclosures Michael J. Satlin, MD, MS, Achaogen (Consultant)Allergan (Research Grant or Support)BioFire Diagnostics (Research Grant or Support)Merck (Research Grant or Support)Shionogi (Consultant) David Fam, PharmD, Shionogi (Employee) Roger Echols, MD, Shionogi (Consultant) Christopher Longshaw, PhD, Shionogi (Employee) Miki Takemura, MS, SHIONOGI & CO., LTD. (Employee) Yoshinori Yamano, PhD, Shionogi (Employee)

647. Investigation of Heteroresistance Among Klebsiella pneumoniae (KP) Inner Colonies (IC) Observed During Fosfomycin Disk Diffusion (DD) Testing

Abstract Background During fosfomycin DD testing, the frequent occurrence of non-susceptible IC within the zone of inhibition of susceptible isolates has been noted. The Clinical & Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) have contradicting recommendations on how IC should be interpreted; CLSI recommends considering IC when interpreting DD results whereas EUCAST recommends ignoring them. This study sought to identify the susceptibility of these IC and to understand whether heteroresistance contributes to the appearance of IC during fosfomycin DD. Methods This study included a convenience sample of 71 KP clinical isolates from 3 United States locations. During DD testing, 58 (81.7%) of these isolates displayed at least one IC. Broth microdilution (BMD) minimal inhibitory concentration (MIC) testing, using extrapolated CLSI Escherichia coli breakpoints, was performed on a subset (n=32) of the IC in duplicate for comparison to the corresponding parent MIC values. This was followed by a modified disk elution screening test for heteroresistance to compare the frequency of low level resistance (LLR) and high level resistance (HLR) between the susceptible isolates that produced resistant IC (n=6) and those that did not produce any IC (n=3). Results The MIC range for the IC isolates (128 to > 1024 μg/mL) increased as compared to the parent isolates (< 2 to > 256 μg/mL) and MIC50/90 increased from the parent (128/ > 256 μg/mL) to IC (1024/ > 1024 μg/mL) isolates. All IC isolates had a resistant MIC value vs. 46.5% of parent isolates, and over 90% of IC isolates had an MIC at least 2 dilutions higher than their corresponding parent isolate. Heteroresistance screening found all tested isolates to be positive for LLR, and 8 of 9 positive for HLR, while the one HLR-negative isolate was IC-producing. Conclusion IC were frequent during fosfomycin DD testing and were commonly more resistant than their corresponding KP parent isolates. A small subset of these isolates tested via a modified disk elution test displayed either LLR or HLR regardless of the absence of IC. These results call for further investigation among a larger isolate set to understand what mechanisms are responsible for the frequency of IC and their increased fosfomycin resistance. Disclosures All Authors: No reported disclosures

In Vitro Activity of Vancomycin, Teicoplanin, Linezolid and Daptomycin Against Methicillin-Resistant Staphylococcus aureus Isolates Collected from Chinese Hospitals in 2018-2020.

IntroductionVancomycin, teicoplanin, linezolid and daptomycin are four major antibacterials used for methicillin-resistant Staphylococcus aureus (MRSA) infection treatment. However, with the increasing failure of clinical MRSA anti-infective treatment, it is urgent to investigate the status of MRSA sensitivity to these four drugs.MethodsIn the present study, 407 non-duplicated MRSA isolates from 6 provinces in China were collected from January 2018 to August 2020. The minimum inhibitory concentrations (MICs) of vancomycin, teicoplanin, linezolid and daptomycin were determined by broth microdilution method, and their MIC50, MIC90, and geometric mean MIC were calculated.ResultsAll 407 MRSA strains were sensitive to these four antibacterials. MIC range of vancomycin, teicoplanin, linezolid and daptomycin was 0.25 to 2 mg/L, 0.125 to 4 mg/L, 0.25 to 4 mg/L and 0.06 to 1 mg/L, respectively. Between 2018 and 2020, there was no “MIC creep” in vancomycin, teicoplanin and daptomycin. The geometric mean MIC of linezolid was not increased, but both MIC50 and MIC90 in 2019 and 2020 MRSA isolates were higher than 2018 isolates.ConclusionAll MRSA isolates remained sensitivity to vancomycin, teicoplanin, linezolid and daptomycin. The linezolid MIC50 and MIC90 increased have been found in this study.

In vitro evaluation of the antibacterial activity of nemonoxacin against Mycobacterium abscessus

Objective: To evaluate the in vitro antibacterial activity of nemonoxacin against clinical isolates of Mycobacterium abscessus (M. abscessus). Methods: A total of 194 clinical strains of M. abscessus were collected from 2014 to 2017 in Shanghai Pulmonary Hospital. The minimum inhibitory concentrations (MICs) of nemonoxacin and other quinolones commonly used (moxifloxacin, levofloxacin and ciprofloxacin) against M. abscessus in clinic was determined by the micro-broth dilution method. Synergy between nemonoxacin and frequently used anti-M. abscessus drugs (clarithromycin, amikacin, imipenem, cefoxitin, tigecycline and linezolid) was assessed in vitro. Results: The MIC range of nemonoxacin to M. abscessus was 0.25-64.00 mg/L. The MIC50 and MIC90 were 4 and 16 mg/L, respectively. Most M. abscessus isolates demonstrated an MIC of ≤ 4 mg/L against nemonoxacin, with a percentage of 68.0% (132/194), which was significantly higher than that against moxifloxacin (51.0%, 99/194; χ2 = 11.651, P<0.01), ciprofloxacin (46.4%, 90/194; χ2 = 18.572, P<0.01) and levofloxacin (25.8%, 50/194; χ2 = 69.586, P<0.01), respectively. Nemonoxacin showed no antagonistic effect with commonly used anti-M. abscessus drugs, except imipenem. Conclusions: Nemonoxacin showed moderate in vitro antibacterial activity against M. abscessus, which was better than that of other fluoroquinolones commonly used in clinic at present. Therefore, nemonoxacin may be one of the options for combined treatment of M. abscessus infection.

Therapeutic Drug Monitoring of Moxifloxacin to Guide Treatment of Mycoplasma hominis Meningitis in an Extremely Preterm Infant.

Mycoplasma hominis (M hominis) is a rare cause of neonatal bacterial meningitis. Treatment can be challenging because of M hominis' intrinsic antibiotic resistance and the difficulty in accessing antimicrobial susceptibility testing. In this report, we describe an extremely preterm male infant with seizures who had a subsequent diagnosis of M hominis meningitis. Because of severity of illness, doxycycline (4 mg/kg IV every 24 hours) and moxifloxacin (5 mg/kg IV every 24 hours) were started empirically. Repeat cerebrospinal fluid cultures were negative and showed decreasing pleiocytosis. Given the concentration-dependent killing of moxifloxacin and concern for endovascular infection from a concomitant cerebral venous sinus thrombosis, serum concentrations of moxifloxacin were obtained to estimate pharmacokinetic and pharmacodynamic parameters. These were compared to the targets described in other case reports of M hominis meningitis. The maximum serum concentration (Cmax) was 2.5 mg/L, volume of distribution was 2.2 L/kg, clearance was 0.18 L/kg/hr, terminal half-life was 8.6 hours, and area-under-the-concentration-time curve (AUC) was 28.1 mg•hr/L. Using the range of minimum inhibitory concentrations (MICs) reported in the literature, the estimated Cmax/MIC for this patient was 21 to 158 (target Cmax/MIC: >10) and AUC/MIC was 234 to 1757 (target AUC/MIC: ≥100). Doxycycline and moxifloxacin were continued for 6 weeks. No adverse events to moxifloxacin or doxycycline were observed in the NICU. This report describes the successful treatment of M hominis neonatal meningitis and adds to the knowledge of pharmacokinetic and pharmacodynamic parameters of moxifloxacin in neonates. Additional data will help to confirm the role for routine therapeutic drug monitoring of moxifloxacin in neonates.

In vitro activity of the antimicrobial peptides h-Lf1-11, MSI-78, LL-37, fengycin 2B, and magainin-2 against clinically important bacteria.

We investigated the antibacterial activity of the antimicrobial peptides h-Lf1-11, MSI-78, LL-37, fengycin 2B, and magainin-2. The minimum inhibitory concentration (MIC) was determined by microdilution technique according to CLSI (M07-A9, 2012) against Escherichia coli, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, carbapenem-resistant Klebsiella pneumoniae, and Acinetobacter baumannii. The MSI-78 showed potent bactericidal activity with MIC range of 1.25-40mg/L against all bacterial strains. The h-Lf1-11, magainin-2, and LL-37 exhibited moderate activity (MIC range of 40-160, 80-160, and 40-160mg/L, respectively) while the fengycin 2B did not show significant activity against all bacterial strains tested. These results revealed that MSI-78, h-Lf1-11, magainin-2, and LL-37 have great potential as antibacterial agents and their activity deserves to be more explored in further studies for the treatment of antibiotic-resistant bacteria.

Pre-clinical Impact of the Synergistic Mechanism of Daptomycin and Ceftaroline on Patients with Methicillin-resistant Staphylococcus aureus Bacteremia Infections.

Our study aims at assessing the pre-clinical impact of the synergistic mechanism of Daptomycin (DAP) and Ceftaroline (CFT) on patients with Methicillin-Resistant Staphylococcus aureus Bacteremia infections (MRSAB). A systematic overview was conducted by searching PubMed, Oxford academic, and Cochrane library up to June 2020. All English- language clinical trials, in vitro studies, and case reports related to the synergistic drug therapy for MRSAB. In the case of MRSAB infections, we examined two different in vitro studies that showed effective synergism with DAP and CFT. The Minimum Inhibitory Concentration (MIC) range observed for each is as follow: DAP 0.125-1 mg/L, CFT 0.38-1 mg/L, DAP + CFT 0.094-0.5 mg/L, vancomycin (VAN) 0.75-2 mg/L, VAN + CFT 0.25-2 mg/L. DAP + CFT combination displayed the most efficacy with the lowest MIC. The statistical analysis performed showed that DAP + CFT obtained significantly lower fractional inhibitory concentration (FIC) values (0.941 ± 0.328) compared with VAN + CFT. In vitro activities of regimens tested on DAP non-susceptibility and VAN intermediate after 96 hours showed DAP 8.29 ± 0.03a log10 CFU/mL, VAN 6.82 ± 0.04a log10 Colony Forming Unit (CFU)/mL, CFT 4.63 ± 0.19a log10 CFU/mL, DAP + CFT 1.15 ± 0.20b log10 CFU/mL, VAN + CFT 3.18 ± 0.49a log10 CFU/mL. (a meaning significantly different than DAP plus CFT, P< equal to 0.001b meaning therapeutic enhancement combination was defined as ≥ 2 log10 CFU/ml reduction over the most active single agent). Based on these results, although DAP was not susceptible, the Colony Forming Unit (CFU) for DAP and CFT had the best therapeutic results. In vitro studies have shown that a combination DAP and CFT is more efficacious than the combination of VAN and CFT in MRSA bacteremia infections. The synergic effects of DAP (bactericidal) and CFT (bactericidal) is statistically significant, in recent trials, warranting promising evidence for its use in complicated bacteremia infection.

Genetic description of VanD phenotype vanA genotype in vancomycin-resistant Enterococcus faecium isolates from a Bone Marrow Transplantation Unit.

Vancomycin-resistant Enterococcus faecium (VREfm) is an important agent of hospital-acquired infection. VanA phenotype is characterized by resistance to high levels of vancomycin and teicoplanin and is encoded by the vanA gene, whereas VanD phenotype is characterized by resistance to vancomycin and susceptibility or intermediate resistance to teicoplanin; however, some isolates carry a VanD phenotype with a vanA genotype, but there are many gaps in the knowledge about the genetic mechanisms behind this pattern. To characterize the genetic structure, clonality, and mobile genetic elements of VRE isolates that display a VanD-vanA phenotype. All vanA VRE-fm isolates displayed minimum inhibitory concentration (MIC) for vancomycin > 32µg/mL and intermediate or susceptible MIC range for teicoplanin (8-16µg/mL). The isolates were not clonal, and whole-genome sequencing analysis showed that they belonged to five different STs (ST478, ST412, ST792, ST896, and ST1393). The absence of some van complex genes were observed in three isolates: Ef5 lacked vanY and vanZ, Ef2 lacked vanY, and Ef9 lacked orf1 and orf2; moreover, another three isolates had inverted positions of orf1, orf2, vanR, and vanS genes. IS1542 was observed in all isolates, whereas IS1216 in only five. Moreover, presence of other hypothetical protein-encoding genes located downstream the vanZ gene were observed in six isolates. VRE isolates can display some phenotypes associated to vanA genotype, including VanA and VanB, as well as VanD; however, further studies are needed to understand the exact role of genetic variability, rearrangement of the transposon Tn1546, and presence of insertion elements in isolates with this profile.

Predicting a therapeutic cut-off serum level of itraconazole in recalcitrant tinea corporis and cruris-A prospective trial.

With rising resistance to terbinafine, and consistently high MICs to fluconazole and griseofulvin, itraconazole is being increasingly used as a first line drug for tinea corporis/cruris. However, inadequate clinical responses are often seen with it in spite of in vitro susceptibility. This is possibly related to a variable pharmacokinetic profile of itraconazole. The drug serum levels associated with the therapeutic outcome have not been defined in dermatophytic infections. Forty treatment naïve patients with tinea corporis/cruris were randomised to one of the three dose groups (100, 200 and 400mg/day) of itraconazole. The drug serum levels of 21 of these patients were obtained after 2weeks of treatment and correlated with the final clinical outcome and in vitro antifungal susceptibility data. Trichophyton indotineae was identified by sequencing of ITS region of rDNA and TEF1α. All isolates were sensitive to itraconazole (Minimum Inhibitory Concentration (MICs) range: 0.06-0.5µg/ml), while MICs to terbinafine were uniformly high (range 8-32µg/ml). Thirty-seven patients (92.5%) achieved complete cure, while three failed treatment. Serum levels achieved with 400mg/day were significantly higher than levels with 100 or 200mg dose. All patients with itraconazole serum levels of >0.2µg/ml were cured, while two out of the 10 patients with serum levels <0.2µg/ml failed treatment. Therapeutic failures are uncommon with itraconazole, and the prevalent strain in India has low itraconazole MICs. Treatment failure is likely with itraconazole serum levels of <0.2µg/ml, while levels >0.2µg/ml are consistently associated with a positive therapeutic outcome.

Minimum inhibitory concentration of essential oils against Staphylococcus aureus isolated from dogs with external otitis

Canine otitis externa is a disease that affects the external acoustic meatus of about 20% of dogs at some point in life, without predilection for race, age, or sex. It is a multifactorial disease whose etiology involves several microorganisms, detaching Staphylococcus aureus. Antimicrobials are the basis for treating this illness; however, due to the increase in antimicrobial resistance, conventional drugs have become ineffective, requiring the search for alternative therapies. In this context, essential oils (EOs) have great therapeutic potential due to their broad antimicrobial action. This study aimed to evaluate the minimum inhibitory concentration (MIC) in order to measure the MIC50 and MIC90 of gentamicin and EOs of Eugenia caryophyllata, Thymus vulgaris, Cymbopogon winterianus, Cymbopogon citratus, and Cinnamomum cassia against 62 Staphylococcus aureus strains isolated from the external acoustic meatus of dogs. All EOs showed antibacterial action against the studied microorganisms, and their MIC50 and MIC90 were as follows: Eugenia caryophyllata, 2.42 mg mL-1 and 7.25 mg mL-1; Thymus vulgaris, 9.51 mg mL-1 and 22.94 mg mL-1; Cymbopogon winterianus, 26.78 mg mL-1 and 157.79 mg mL-1; Cinnamomum cassia and Cymbopogon citratus, lower than 16.48 and 27.81 mg mL-1, with the same MIC for all isolates. The MIC50 and MIC90 found for gentamicin were 1μg mL-1 and 8 μg mL-1. The MIC range found to antibiotic in this assay was 0.5 μg mL-1 to 128 μg mL-1, and the isolates were classified as susceptible [48 strains (77.41%) - MIC range of 0.5-4.0 μg mL-1], intermediate [eight strains (12.90%) - (MIC = 8.0 μg mL-1], or resistant [six strains (9.68%) - MIC ≥ 16 μg mL-1]. The results, according to the in vitro assays, showed that resistance to gentamicin, one of the antimicrobials most commonly used to treat canine otitis, is present in the Staphylococcus aureus population evaluated. Additionally, the tested EOs have great potential for therapeutic use, however future studies should be carried out to evaluate their in vivo efficacy.

Evidence of Resistance of Heavy Metals from Bacteria Isolated from Natural Waters of a Mining Area in Mexico

This study focuses on identifying relationships between the content of heavy metals in water and the resistance patterns of different bacteria. Samples from watercourses in one of the most important mining areas in Mexico were collected. Seventy-one bacteria were isolated, and their resistance to Cr, Zn, Cu, Ag, Hg, and Co was studied. The Minimum Inhibitory Concentration range was determined, and a Multiple Metal Resistant index was calculated. After that, 11 isolated bacteria were chosen to estimate kinetic parameters. The obtained results show differences in the behavior of the studied bacteria concerning the presence of heavy metals in the media: (1) without effect, (2) inhibited growth; and (3) considerable inhibited growth. Finally, a Performance Index was proposed to select adequate bacteria for heavy metals removal; five bacteria were selected. Among them, Pseudomonas koreensis was identified as a good candidate for a future biosorption system since these bacteria can stimulate growth in the presence of all the metals tested.

Antimicrobial Susceptibility of Ertapenem in Neisseria gonorrhoeae Isolates Collected Within the China Gonococcal Resistance Surveillance Programme (China-GRSP) 2018

PurposeThis study aimed to determine the minimum inhibitory concentrations (MICs) of ertapenem on Neisseria gonorrhoeae collected from eight Chinese provinces in 2018.MethodsThe MICs of ertapenem on 503 Neisseria gonorrhoeae isolates (415 isolates selected randomly and 88 isolates selected with preference) were measured using the agar dilution method. For comparison, the MICs of ceftriaxone and azithromycin were detected.ResultsAmong 415 randomly selected isolates, the MIC range for ertapenem was from ≤0.008 mg/L to 0.5 mg/L. The corresponding MIC50 and MIC90 were 0.06 and 0.125 mg/L, respectively. Twelve of 415 isolates (2.9%) exhibited MIC values ≥0.25 mg/L, and only one isolate (0.2%) had a MIC of 0.5 mg/L. By comparing all 503 tested isolates, a correlation of r = 0.487 (P <0.001) between ertapenem and ceftriaxone MIC was observed, and the correlation between MICs of ertapenem and azithromycin was low (r = −0.12, P = 0.007). In 24 ceftriaxone-decreased susceptibility isolates, four isolates (16.7%) showed a MIC ≥0.25 mg/L for ertapenem. In 85 azithromycin resistant isolates, three isolates (3.5%) showed a MIC ≥0.25 mg/L for ertapenem.ConclusionThe in vitro results suggest that ertapenem has satisfactory susceptibility in isolates collected from eight provinces in China; hence, it might be a promising treatment option for resistant gonococcal infections.

Bioactivity of medicinal plant extracts against human fungal pathogens and evaluation of toxicity using Vero cells.

Medicinal plants are a potential source of new antifungal agents to combat the development of drug-resistant fungi. This study aims to investigate the aerial parts of Alternanthera sessilis (Amaranthaceae) and Ipomoea aquatica (Convolvulaceae), and the leaves of Catunaregam spinosa (Rubiaceae) and Tradescantia spathacea (Commelinaceae) for antifungal activity and cytotoxicity. The plant materials were extracted sequentially using hexane, chloroform, ethyl acetate, ethanol, methanol, and distilled water. The antifungal activity was evaluated against four species of yeasts and two species of filamentous fungi using a colorimetric broth microdilution method. The toxicity of the extracts was assessed using African monkey kidney epithelial (Vero) cells. All 24 extracts from the four medicinal plants showed inhibitory activity against all fungal species, except Aspergillus fumigatus, with a minimum inhibitory concentration range of 0.04-2.50 mg/mL. The antifungal activity of these plants was more prominent on the yeasts than the filamentous fungi. Generally, the less polar extracts (hexane, chloroform, and ethyl acetate) of the plants had stronger antifungal activity than the more polar extracts (ethanol, methanol, and water). In contrast, toxicity assessment revealed that the less polar extracts showed relatively higher toxicity towards the Vero cells than the more polar extracts. The lowest median cytotoxic concentration was shown by the chloroform extract of A. sessilis (17.4 ± 0.4 μg/mL). All water extracts, the methanol extract of I. aquatica, and the ethyl acetate, ethanol, and methanol extracts of T. spathacea did not show significant toxicity (P>0.05) towards the Vero cells. The results suggested that Tradescantia spathacea has the most promising potential for pharmaceutical developments due to its broad spectrum and selective activity against human fungal pathogens.

Broad-spectrum antifungal activity of lipopeptide brevilaterin B and its inhibition effects against Fusariumoxysporum and Penicillium chrysogenum.

Brevilaterin B is a natural antimicrobial lipopeptide produced by Brevibacillus laterosporus S62-9. However, its antifungal spectrum and modes of action are still unclear. Herein, we investigated the detailed antifungal activity of brevilaterin B against 33 pathogenic fungi and the antifungal effects against two sensitive fungi in vitro and in vivo. Brevilaterin B exhibited inhibitory activity against 33 pathogenic fungi involved in plant disease and food spoilage at the minimum inhibitory concentrations (MICs) range of 16-128μgml-1 . The antifungal effects were further studied by Fusarium oxysporum and Penicillium chrysogenum. Both spore germination and mycelium growth were inhibited by brevilaterin B at sub-MIC. Transmission electron microscopy and fluorescent dye staining assays indicated brevilaterin B damaged cell integrity and induced apoptosis. In vivo tests, brevilaterin B inhibited the infection of F. oxysporum to Dendrobium officinale and P. chrysogenum to mandarin (Citrus reticulata) at 500μgml-1 , respectively. Brevilaterin B showed broad-spectrum antifungal activity against 33 pathogenic fungi. And its antifungal modes of action were proposed as damaging cell integrity and inducing cell apoptosis. The lipopeptide is promising to control F. oxysporum in the D. officinale and P. chrysogenum in the mandarin. The research provided insights into antifungal modes of action of brevilaterin B. The lipopeptide brevilaterin B is potential to be developed as a broad-spectrum antifungal agent for agricultural biocontrol and postharvest storage.

Investigation of in vitro activity of colistin and tygecyclin against Stenotrophomonas maltophilia isolates

Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen, causing infections whose management is often problematic due to its inherent resistance to many antibiotics. In this study, we aimed to investigate the antimicrobial susceptibility of colistin and tygecyclin as an alternative treatment options for S. maltophilia infections. A total of 122 S. maltophilia isolates were tested. Minimum inhibitory concentration (MIC) values of colistin and tygecycline were determined by broth microdilution method. Susceptibility of TMP/SMX and levofloxacin (LVX) were determined by disc diffusion method and MIC value of ceftazidime (CAZ) was determined by using E-test. Out of 122 S. maltophilia isolates, 5 (4%) of them were resistant to TMP-SXM. MIC range was 0.125- &gt;512 μg/ml and MIC50 64 μg/ml, MIC90 512 μg/ml for colistin. MIC range for tygecyclin was detected as 0.5- &gt;8, MIC50 2 μg/ml and MIC90 8 μg/ml. Tygecyclin resistance was detected as 66.4% according to the EUCAST guideline and 13.1% according to the USA-FDA breakpoints. And colistin resistance was determined as 86.9% according to both guidelines.