A Mini-Review of In Vitro Data for Candida Species, Including C. auris, Isolated during Clinical Trials of Three New Antifungals: Fosmanogepix, Ibrexafungerp, and Rezafungin

This mini-review summarizes the clinical outcomes and antifungal susceptibility results, where available, for three new antifungals, including fosmanogepix, ibrexafungerp, and rezafungin, against Candida isolates cultured from patients in clinical trials. When reported, most of the data were generated by the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method or by both the CLSI and European Committee on Antimicrobial Susceptibility Testing (EUCAST) methodologies. For fosmanogepix, we summarize the in vitro data for C. auris isolates from 9 patients and for Candida spp. cultured from 20 patients in two clinical trials. Ibrexafungerp has also been evaluated in several clinical trials. From conference proceedings, a total of 176 Candida isolates were evaluated in the FURI and CARES studies, including 18 C. auris isolates (CARES study). However, MIC data are not available for all clinical isolates. Results from the ReSTORE rezafungin phase 3 clinical study also included in vitro results against Candida spp., but no patients with C. auris infections were included. In conclusion, this mini-review summarizes insights regarding clinical outcomes and the in vitro activity of three new antifungals against Candida spp. cultured from patients in clinical trials.

In Vitro Antibacterial Activity of Ceftobiprole and Comparator Compounds against Nation-Wide Bloodstream Isolates and Different Sequence Types of MRSA

Bloodstream infections by bacteria, especially multidrug-resistant bacteria, remain a worldwide public health concern. We evaluated the antibacterial activity of ceftobiprole and comparable drugs against different bloodstream isolates and different sequence types of methicillin-resistant Staphylococcus aureus (MRSA) in China. We found that MRSA, methicillin-susceptible Staphylococcus aureus (MSSA), and methicillin-susceptible coagulase-negative Staphylococcus (MSCNS) displayed ceftobiprole sensitivity rates of >95%, which are similar to the rates for linezolid, daptomycin, and vancomycin. Of the tested MRCNS strains, 90.4% were sensitive to ceftobiprole. The sensitivities of ST59, ST398, and ST22 MRSA to ceftobiprole were higher than that of ST239. Ceftobiprole's MIC50/90 value against Enterococcus faecalis was 0.25/2 mg/L, whereas Enterococcus faecium was completely resistant to this drug. Ceftobiprole exhibited no activity against ESBL-positive Enterobacterales, with resistance rates between 78.6% and 100%. For ESBL-negative Enterobacterales, excluding Klebsiella oxytoca, the sensitivity to ceftobiprole was comparable to that of ceftazidime, ceftriaxone, and cefepime. The MIC50/90 value of ceftobiprole against Pseudomonas aeruginosa was 2/16 mg/L, and for Acinetobacter baumannii, it was 32/>32 mg/L. Thus, ceftobiprole shows excellent antimicrobial activity against ESBL-negative Enterobacterales and Pseudomonas aeruginosa (comparable to that of ceftazidime, ceftriaxone, and cefepime); however, it is not effective against ESBL-positive Enterobacterales and Acinetobacter baumannii. These results provide important information to clinicians.

Role of Fisetin in Selected Malignant Neoplasms in Women

A promising therapeutic window and cost-effectiveness are just two of the potential advantages of using naturally derived drugs. Fisetin (3,3',4',7-tetrahydroxyflavone) is a natural flavonoid of the flavonol group, commonly found in fruit and vegetables. In recent years, fisetin has gained wide attention across the scientific community because of its broad spectrum of pharmacological properties, including cytotoxic activity against most abundant cancers. By stimulating or inhibiting selected molecular targets or biochemical processes, fisetin could affect the reduction of metastasis or cancer progression, which indicates its chemotherapeutic or chemopreventive role. In this review, we have summarized the results of studies on the anticancer effects of fisetin on selected female malignancies, both in in vitro and in vivo tests, i.e., breast, cervical, and ovarian cancer, published over the past two decades. Until now, no article dedicated exclusively to the action of fisetin on female malignancies has appeared. This review also describes a growing number of nanodelivery systems designed to improve the bioavailability and solubility of this natural compound. The reported low toxicity and activity of fisetin on cancer cells indicate its valuable potential, but large-scale clinical trials are urgently needed to assess real chemotherapeutic efficacy of this flavonoid.

A US-based national surveillance study for the susceptibility and epidemiology of Clostridioides difficile isolates with special reference to ridinilazole: 2020-2021

We have previously reported on the susceptibility and epidemiology of Clostridioides difficile isolates from six geographically dispersed medical centers in the United States. This current survey was conducted with isolates collected in 2020-2021 from six geographically dispersed medical centers in the United States, with specific attention to susceptibility to ridinilazole as well as nine comparators. C. difficile isolates or stools from patients with C. difficile antibiotic-associated diarrhea were collected and referred to a central laboratory. After species confirmation of 300 isolates at the central laboratory, antibiotic susceptibilities were determined by the agar dilution method [M11-A9, Clinical and Laboratory Standards Institute (CLSI)] against the 10 agents. Ribotyping was performed by PCR capillary gel electrophoresis on all isolates. Ridinilazole had a minimum inhibitory concentration (MIC) 90 of 0.25 mcg/mL, and no isolate had an MIC greater than 0.5 mcg/mL. In comparison, fidaxomicin had an MIC 90 of 0.5 mcg/mL. The vancomycin MIC 90 was 2 mcg/mL with a 0.7% resistance rate [both CLSI and European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria]. The metronidazole MIC 90 was 1 mcg/mL, with none resistant by CLSI criteria, and a 0.3% resistance rate by EUCAST criteria. Among the 50 different ribotypes isolated in the survey, the most common ribotype was 014-020 (14.0%) followed by 106 (10.3%), 027 (10%), 002 (8%), and 078-126 (4.3%). Ridinilazole maintained activity against all ribotypes and all strains resistant to any other agent tested. Ridinilazole showed excellent in vitro activity against C. difficile isolates collected between 2020 and 2021 in the United States, independent of ribotype.

Novel diamides inspired by protein kinase inhibitors as anti-Trypanosoma cruzi agents: in vitro and in vivo evaluations

Background: Chagas disease is a life-threatening illness caused by Trypanosoma cruzi. The involvement of serine-/arginine-rich protein kinase in the T. cruzi life cycle is significant. Aims: To synthesize, characterize and evaluate the trypanocidal activity of diamides inspired by kinase inhibitor, SRPIN340. Material & Methods: Synthesis using a three-step process and characterization by infrared, nuclear magnetic resonance and high-resolution mass spectrometry were conducted. The selectivity index was obtained by the ratio of CC50/IC50 in two in vitro models. The most active compound, 3j, was evaluated using in vitro cytokine assays and assessing in vivo trypanocidal activity. Results: 3j activity in the macrophage J774 lineage showed an anti-inflammatory profile, and mice showed significantly reduced parasitemia and morbidity at low compound dosages. Conclusion: Novel diamide is active against T. cruzi in vitro and in vivo.

The Spicy Science of Dendrimers in the Realm of Cancer Nanomedicine: A Report from the COST Action CA17140 Nano2Clinic

COST Action CA17140 Cancer Nanomedicine-from the bench to the bedside (Nano2Clinic,) is the first, pan-European interdisciplinary network of representatives from academic institutions and small and medium enterprises including clinical research organizations (CROs) devoted to the development of nanosystems carrying anticancer drugs from their initial design, preclinical testing of efficacy, pharmacokinetics and toxicity to the preparation of detailed protocols needed for the first phase of their clinical studies. By promoting scientific exchanges, technological implementation, and innovative solutions, the action aims at providing a timely instrument to rationalize and focus research efforts at the European level in dealing with the grand challenge of nanomedicine translation in cancer, one of the major and societal-burdening human pathologies. Within CA17140, dendrimers in all their forms (from covalent to self-assembling dendrons) play a vital role as powerful nanotheranostic agents in oncology; therefore, the purpose of this review work is to gather and summarize the major results in the field stemming from collaborative efforts in the framework of the European Nano2Clinic COST Action.

In Vitro Activity of Finafloxacin against Panels of Respiratory Pathogens

This study determined the in vitro activity of finafloxacin against panels of bacterial strains, representative of those associated with infection in cystic fibrosis patients and predominately isolated from clinical cases of respiratory disease. Many of these isolates were resistant to various antimicrobials evaluated including the aminoglycosides, cephalosporins, carbapenems and fluoroquinolones. Broth microdilution assays were performed at neutral and acidic pH, to determine antimicrobial activity. Finafloxacin demonstrated superior activity at reduced pH for all of the bacterial species investigated, highlighting the requirement to determine the activity of antimicrobials in host-relevant conditions.

Comparison of In Vitro Activity of Ceftazidime-Avibactam and Imipenem-Relebactam against Clinical Isolates of Pseudomonas aeruginosa

The role of novel β-lactam/β-lactamase inhibitor combinations in ceftazidime-nonsusceptible (CAZ-NS) and imipenem-nonsusceptible (IPM-NS) Pseudomonas aeruginosa has not been fully elucidated. This study evaluated the in vitro activity of novel β-lactam/β-lactamase inhibitor combinations against Pseudomonas aeruginosa clinical isolates, determined how avibactam restored ceftazidime activity, and compared the activity of ceftazidime-avibactam (CZA) and imipenem-relebactam (IMR) against KPC-producing P. aeruginosa. Similar high susceptibility rates for CZA, IMR, and ceftolozane-tazobactam (88.9% to 89.8%) were found for 596 P. aeruginosa clinical isolates from 11 hospitals in China, and a higher susceptibility rate to ceftazidime than imipenem was observed (73.5% versus 63.1%). For CAZ-NS and IPM-NS isolates, susceptibility rates for CZA, ceftolozane-tazobactam, and IMR were 61.5% (75/122), 54.9% (67/122), and 51.6% (63/122), respectively. For CAZ-NS, IPM-NS but CZA-susceptible isolates, 34.7% (26/75) harbored acquired β-lactamases with KPC-2 predominant (n = 19), and 45.3% (34/75) presented overexpression of chromosomal β-lactamase ampC. Among 22 isolates carrying KPC-2 carbapenemase alone, susceptibility rates to CZA and IMR were 86.4% (19/22) and 9.1% (2/22), respectively. Notably, 95% (19/20) of IMR-nonsusceptible isolates had an inactivating mutation of oprD gene. In conclusion, CZA, ceftolozane-tazobactam, and IMR exhibit high activity against P. aeruginosa, and CZA is more active than IMR against CAZ-NS and IPM-NS isolates as well as KPC-producing P. aeruginosa. Avibactam overcomes ceftazidime resistance engendered by KPC-2 enzyme and overexpressed AmpC. IMPORTANCE The emergence of antimicrobial resistance poses a particular challenge globally, and the concept of P. aeruginosa with "difficult-to-treat" resistance (DTR-P. aeruginosa) was proposed. Here, P. aeruginosa clinical isolates were highly susceptible to three β-lactamase inhibitor combinations, CZA, IMR, and ceftolozane-tazobactam. The combination of KPC-2 enzyme and nonfunctional porin OprD contributed to IMR resistance in P. aeruginosa, and CZA was more active than IMR in fighting against KPC-2-producing P. aeruginosa. CZA also showed good activity against CAZ-NS and IPM-NS P. aeruginosa, primarily by inhibiting KPC-2 enzyme and overproduced AmpC, supporting the clinical use of CZA in the treatment of infections caused by DTR-P. aeruginosa.

In Vitro Activity of Cefiderocol Compared to Other Antimicrobials against a Collection of Metallo-Beta-Lactamase-Producing Gram-Negative Bacilli from Southern Spain

In this study, we aimed to comparatively evaluate the in vitro activity of cefiderocol versus other antimicrobials against a well-characterized collection of metallo-beta-lactamase (MBL)-producing Gram-negative bacilli (MBL-GNB) isolates from hospitals in Andalusia, Spain. We recovered 232 MBL-GNB from Andalusian hospitals, including 160 Enterobacterales and 72 nonfermenting Gram-negative bacilli belonging to 44 different clones (2015 to 2020). Cefiderocol and comparator MICs were determined with commercial methods (UMIC [Bruker] and EUMDROXF [Sensititre; Thermo Fisher], respectively). EUCAST breakpoints were used for all antimicrobials tested, and CLSI also was used for cefiderocol. Control strains used were E. coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. Cefiderocol showed potent in vitro activity against isolates tested, regardless of breakpoint (susceptibility rates, 85.3% for EUCAST versus 96.6% for CLSI, P < 0.001). MIC ranges for Enterobacterales and nonfermenting Gram-negative bacilli (NF-GNB) were ≤0.03 to 1 mg/L and 0.06 to 2 (IMP), 0.06 to 8 mg/L and 0.06 to 16 (VIM), 0.25 to 16 mg/L and 2 to 16 mg/L (NDM), respectively, and 0.25 to 8 mg/L for double MBL-producing Enterobacterales. By species, all cefiderocol-susceptible rates were over 90%, except Klebsiella oxytoca, Enterobacter cloacae, Escherichia coli, and Acinetobacter spp. Significant differences were observed comparing resistant isolates between Enterobacterales and NF-GNB by EUCAST (19.4% versus 4.2%, P < 0.01), but not by CLSI (4.4% versus 1.4%, P = 0.2). Cefiderocol was the most active antimicrobial tested. Cefiderocol showed excellent in vitro activity against MBL-GNB, especially NF-GNB; almost all isolates resistant to comparators were susceptible. IMPORTANCE This article demonstrates the efficacy of cefiderocol against a large collection of well-characterized metallo-beta-lactamase-producing isolates, some of them even producing double carbapenemases. Furthermore, cefiderocol activity is compared to other novel broad-spectrum antimicrobials with activity against carbapenemases.

High expression of antimicrobial peptides cathelicidin-BF in Pichia pastoris and verification of its activity

Antibacterial peptides are endogenous polypeptides produced by multicellular organisms to protect the host against pathogenic microbes, they show broad spectrum antimicrobial activities against various microorganisms and possess low propensity for developing resistance. The purpose of this study is to develop recombinant antibacterial peptide cathelicidin-BF by genetic engineering and protein engineering technology, and study its antibacterial activity in vitro and in vivo, so as to provide reference for the production and application of recombinant antibacterial peptide cathelicidin-BF. In this study, on account of Pichia pastoris eukaryotic expression system, we expressed and prepared antibacterial peptide cathelicidin-BF. Then, the minimum inhibitory concentration of antibacterial peptide cathelicidin-BF and the comparison with the antibacterial activity of antibiotics were determined through the antibacterial experiment in vitro. Chickens as infection model were used to verify the antibacterial peptide activity in vivo. The results show that the bacteriostatic ability of antibacterial peptide cathelicidin-BF is similar to that of antibiotics in certain concentration, and can reach the treatment level of antibiotics. Although the mode of administration of antibacterial peptide is still limited, this study can provide reference for the future research of antibacterial peptide.

In Vitro Activity of Novel Topoisomerase Inhibitors against Francisella tularensis and Burkholderia pseudomallei

Antimicrobial resistance is a global issue, and the investigation of alternative therapies that are not traditional antibiotics are warranted. Novel bacterial type II topoisomerase inhibitors (NBTIs) have recently emerged as a novel class of antibiotics with reduced potential for cross-resistance to fluoroquinolones due to their novel mechanism of action. This study investigated the in vitro activity of a series of cyclohexyl-oxazolidinone bacterial topoisomerase inhibitors against type strains of Francisella tularensis and Burkholderia pseudomallei. Broth microdilution, time-kill, and cell infection assays were performed to determine activity against these biothreat pathogens. Two candidates were identified that demonstrated in vitro activity in multiple assays that in some instances was equivalent to ciprofloxacin and doxycycline. These data warrant the further evaluation of these novel NBTIs and future iterations in vitro and in vivo.

In Vitro and In Vivo Properties of CUO246, a Novel Bacterial DNA Gyrase/Topoisomerase IV Inhibitor

CUO246, a novel DNA gyrase/topoisomerase IV inhibitor, is active in vitro against a broad range of Gram-positive, fastidious Gram-negative, and atypical bacterial pathogens and retains activity against quinolone-resistant strains in circulation. The frequency of selection for single step mutants of wild-type S. aureus with reduced susceptibility to CUO246 was <4.64 × 10^-9 at 4× and 8× MIC and remained low when using an isogenic QRDR mutant (<5.24 × 10^-9 at 4× and 8× MIC). Biochemical assays indicated that CUO246 had potent inhibitory activity against both DNA gyrase (GyrAB) and topoisomerase IV (ParCE). Furthermore, CUO246 showed rapid bactericidal activity in time-kill assays and potent in vivo efficacy against S. aureus in a neutropenic murine thigh infection model. These results suggest that CUO246 may be useful in treating infections by various causative agents of acute skin and skin structure infections, respiratory tract infections, and sexually transmitted infections.

In Vitro Antiparasitic Activities of Monovalent Ionophore Compounds for Human and Canine Leishmaniases

The leishmaniases are vector-borne parasitic diseases affecting humans and animals, with high mortality rates in endemic countries. Infected dogs represent the main reservoir of infection. Disease control is mainly based on chemotherapy, which, at present, shows serious drawbacks both in humans and dogs. Therefore, the discovery or repurposing of new treatments is mandatory. Here, three monovalent ionophores (salinomycin, monensin, nigericin) were tested against promastigotes of Leishmania (L.) infantum, Leishmania tropica, and Leishmania braziliensis, and against amastigotes of L. infantum within human and, for the first time, canine macrophages. All three drugs were leishmanicidal against all Leishmania spp. promastigotes with IC50 values between 7.98 and 0.23 µM. Monensin and nigericin showed IC50 values < 1 µM, whereas salinomycin was the least active compound (IC50 > 4 µM). Notably, the ionophores killed L. infantum amastigotes within human THP-1 cells with IC50 values ranging from 1.67 to 1.93 µM, but they only reduced by 27−37% the parasite burden in L. infantum-infected canine macrophages, showing a host-specific efficacy. Moreover, a selective higher toxicity against canine macrophages was observed. Overall, repurposed ionophores have the potential to be further investigated as anti-Leishmania agents, but different drug options may be required to tackle human or canine leishmaniases.

Simultaneous separation of glycyrrhizic acid, baicalein and wogonin from Radix Glycyrrhizae and Radix Scutellariae using foam fractionation and in vitro activity evaluation

BACKGROUND

In this study, the optimal conditions for the extraction and purification of glycyrrhizic acid from Radix Glycyrrhizae (RG) and baicalein and wogonin from Radix Scutellariae (RS) by foam fractionation were studied on the basis of central composite design (CCD) and response surface methodology.

RESULTS

The results showed that herbal proportion (RG:RS), gas flow and ethanol concentration were the main factors guiding the foam fractionation of RG and RS. The optimum technological parameters were obtained as follows: herbal proportion (RG:RS), 1.86:1.14; gas flow, 109 mL min^-1 ; and ethanol concentration, 53%. Under the optimal operating conditions, the maximal extraction yields of baicalein, glycyrrhizic acid and wogonin were 56.67, 13.25 and 9.51 mg g^-1 , respectively, which were 2.32-, 1.22- and 1.84-fold higher than those of ultrasonic extraction and 17.28-, 1.15- and 9.91-fold higher than those of ultrasonic extraction without hydrolysis, respectively. Investigations on the antioxidant activity showed that the foam-fractionated extract exhibited better free radical scavenging activity (IC₅₀ 13.80 μg mL^-1 ) than that of the ultrasonic extract (IC₅₀ 223.00 μg mL^-1 ). Antibacterial activity showed that the minimum inhibitory concentrations of the foam fractionated extract against Staphylococcus aureus, Candida albicans, Group A Streptococcus and Pseudomonas aeruginosa were 1.38, 1.38, 0.69 and 5.50 mg mL^-1 , respectively.

CONCLUSION

The results indicate that the foam fractionated extract exhibited better extraction yields and free radical scavenging activity than did the ultrasonic extract. Therefore, this fast and eco-friendly method was established and could be a basis for the extraction and separation of other active constituents from herbal medicines. © 2022 Society of Chemical Industry.

In Vitro Evaluation of the Activity of Aztreonam-Avibactam against 341 Recent Clinical Isolates of Anaerobes

Aztreonam-avibactam is under clinical development for multidrug-resistant Gram-negative infections. We evaluated in vitro activity against 341 recent clinical isolates. The addition of avibactam to aztreonam had no effect on the anaerobic activity of aztreonam. IMPORTANCE This work shows that aztreonam-avibactam lacks activity against anaerobic organisms.

Comparison of Anti-Microbic and Anti-Biofilm Activity Among Tedizolid and Radezolid Against Linezolid-Resistant Enterococcus faecalis Isolates

Background

The emergence and spread of linezolid-resistant Enterococcus faecalis (E. faecalis) have emerged as a serious threat to human health globally. Therefore, this study aims to compare the anti-microbic as well as the anti-biofilm activity of linezolid, tedizolid, and radezolid against linezolid-resistant E. faecalis.

Methods

A total of 2128 E. faecalis isolates were assessed from the First Affiliated Hospital of Wenzhou Medical University from 2011 to 2019. Antibiotic sensitivity was evaluated using the micro broth dilution method. Oxazolidinone-resistant chromosomal and plasmid-borne genes such as cfr, cfr(A), cfr(B), cfr(C), cfr(D), optrA, and poxtA were detected by PCR and then sequenced to detect the presence of mutations in the domain V of the 23S rRNA and the ribosomal proteins L3, L4, and L22. Conjugation experiments were conducted using the broth method. The inhibition and eradication of biofilm were evaluated through crystal violet staining, whereas the efflux pump activities were detected by agar dilution.

Results

Out of 2128 isolated E. faecalis, 71 (3.34%) were linezolid-resistant isolates in which the MICs of tedizolid and radezolid ranged from 1 to 4 μg/mL and 0.5–1 μg/mL, respectively. The MIC₅₀/MIC₉₀ of tedizolid and radezolid were 4 and 8-fold lower than the linezolid, respectively. Out of 71 resistant isolates, 57 (80.28%) carried optrA, 1 (1.41%) carried cfr, 4 (5.63%) carried optrA and cfr, and 6 (8.45%) carried optrA and cfr(D), with no mutations of 23S rRNA gene and ribosomal proteins L3, L4, and L22. Besides, the transfer rate of the optrA, cfr, and cfr(D) was 17.91%, 0% and 0%, respectively. Radezolid showed more effectiveness in eradicating biofilm (8 × MIC). However, tedizolid was more effective than radezolid and linezolid in inhibiting the biofilm formation (1/4 MIC, 1/8MIC, and 1/16MIC). Additionally, in combination with CCCP, the MICs of radezolid in all linezolid-resistant isolates decreased ≥4-fold.

Conclusion

Radezolid showed greater antimicrobial activity than tedizolid and linezolid against linezolid-resistant E. faecalis. However, both tedizolid and radezolid showed differential activity on biofilm inhibition, eradication, and efflux pump compared to linezolid. Thus, our study might bring important clinical value in the application of these drugs for resistant pathogenic strains.

Sulfonamide-salicylaldehyde imines active against methicillin- and trimethoprim/sulfonamide-resistant Staphylococci

Background: Increasing resistance has resulted in an urgent need for new antimicrobial drugs. A systematic me-too approach was chosen to modify clinically used sulfonamides to obtain their imines. Methods & results: Twenty-five compounds were synthesized and evaluated for their antibacterial activity. The most active compounds were also investigated against methicillin- and trimethoprim/sulfamethoxazole (SMX)-resistant Gram-positive species. Staphylococci shared the highest susceptibility including resistant strains with minimum inhibitory concentrations from 3.91 μM (≥2.39 μg ml^-1). Crucially, the compounds inhibit MRSA and trimethoprim/SMX-resistant Staphylococci without any cross-resistance. Modification of parent sulfonamides turned a bacteriostatic effect into a bactericidal effect. Toxicity for HepG2 and hemolytic properties were also determined. Conclusions: The presence of a dihalogenated salicylidene moiety is required for optimal activity. Based on toxicity, promising derivatives for further investigation were identified.

In vitro Activity of Meropenem-Vaborbactam versus Other Antibiotics Against Carbapenem-Resistant Escherichia coli from Southeastern China

Purpose

This study aimed to evaluate the in vitro activity of meropenem-vaborbactam (MVB) against a collection of carbapenem-resistant Escherichia coli (CREC) isolates and to compare the activity with other antibiotics with regard to different separation sites, carbapenem-resistant mechanisms, and sequence types (STs).

Methods

A total of 58 CREC strains were used as the experimental strains from the First Affiliated Hospital of Wenzhou Medical University in southeastern China. The minimum inhibitory concentrations of MVB, ceftazidime-avibactam, and tigecycline against all the experimental strains were determined by the microdilution broth method.

Results

MVB exhibited higher antimicrobial activity (83% susceptibility) than that of other antibiotics, except for colistin and tigecycline. The susceptibility of CREC strains towards MVB varied with regard to carbapenem-resistant mechanisms and STs, especially in Klebsiella pneumoniae carbapenemase (KPC)-positive isolates and ST8 isolates.

Conclusion

MVB exhibited considerably high activity against KPC-producing and ST8 CREC isolates. It has the great potential to be an alternative for the treatment of infections caused by CREC after determining the type of carbapenemase, the susceptibility to MVB and/or STs.

Synthesis, structural characterization and antimycobacterial evaluation of several halogenated non-nitro benzothiazinones

8-Nitro-1,3-benzothiazin-4-ones (BTZs), with BTZ043 and PBTZ169 as the most advanced compounds, represent a new class of potent antitubercular agents, which irreversibly inhibit decaprenylphosphoryl-β-d-ribose-2'-epimerase (DprE1), an enzyme crucial for cell wall synthesis in the pathogen Mycobacterium tuberculosis. Synthesis, structural characterization and in vitro testing against Mycobacterium aurum DSM 43999 and M. tuberculosis H₃₇Rv of halogenated 2-(4-ethoxycarbonylpiperazin-1-yl)-1,3-benzothiazin-4-ones lacking a nitro group are reported. X-ray crystallography reveals that the structure of the BTZ scaffold can significantly deviate from planarity. In contrast to recent reports, the results of the present study indicate that further investigation of halogenated non-nitro BTZs for antitubercular activity is less than a promising approach.

Manogepix, the Active Moiety of the Investigational Agent Fosmanogepix, Demonstrates In Vitro Activity against Members of the Fusarium oxysporum and Fusarium solani Species Complexes

We evaluated the in vitro activity of manogepix against Fusarium oxysporum and Fusarium solani species complex (FOSC and FSSC, respectively) isolates per CLSI document M38 broth microdilution methods. Manogepix demonstrated activity against both FOSC (MEC [minimum effective concentration] range, ≤0.015 to 0.03 μg/ml; MIC₅₀ range, ≤0.015 to 0.125 μg/ml) and FSSC (MEC, ≤0.015 μg/ml; MIC₅₀, ≤0.015 to 0.25 μg/ml). Amphotericin B was also active (MIC, 0.25 to 4 μg/ml), whereas the triazoles (MIC, 1 to >16 μg/ml) and micafungin (MEC, ≥8 μg/ml) had limited activity.

New targets for drug design: importance of nsp14/nsp10 complex formation for the 3'-5' exoribonucleolytic activity on SARS-CoV-2

SARS‐CoV‐2 virus has triggered a global pandemic with devastating consequences. The understanding of fundamental aspects of this virus is of extreme importance. In this work, we studied the viral ribonuclease nsp14, one of the most interferon antagonists from SARS‐CoV‐2. Nsp14 is a multifunctional protein with two distinct activities, an N‐terminal 3’‐to‐5’ exoribonuclease (ExoN) and a C‐terminal N7‐methyltransferase (N7‐MTase), both critical for coronaviruses life cycle, indicating nsp14 as a prominent target for the development of antiviral drugs. In coronaviruses, nsp14 ExoN activity is stimulated through the interaction with the nsp10 protein. We have performed a biochemical characterization of nsp14‐nsp10 complex from SARS‐CoV‐2. We confirm the 3’‐5’ exoribonuclease and MTase activities of nsp14 and the critical role of nsp10 in upregulating the nsp14 ExoN activity. Furthermore, we demonstrate that SARS‐CoV‐2 nsp14 N7‐MTase activity is functionally independent of the ExoN activity and nsp10. A model from SARS‐CoV‐2 nsp14‐nsp10 complex allowed mapping key nsp10 residues involved in this interaction. Our results show that a stable interaction between nsp10 and nsp14 is required for the nsp14‐mediated ExoN activity of SARS‐CoV‐2. We studied the role of conserved DEDD catalytic residues of SARS‐CoV‐2 nsp14 ExoN. Our results show that motif I of ExoN domain is essential for the nsp14 function, contrasting to the functionality of these residues in other coronaviruses, which can have important implications regarding the specific pathogenesis of SARS‐CoV‐2. This work unraveled a basis for discovering inhibitors targeting specific amino acids in order to disrupt the assembly of this complex and interfere with coronaviruses replication.

In vitro activity of olorofim against clinical isolates of the Fusarium oxysporum and Fusarium solani species complexes

BACKGROUND

Invasive fusariosis is associated with marked morbidity and mortality in immunocompromised hosts, and clinical outcomes are poor with conventional therapy. Olorofim (F901318) is an investigational antifungal in the orotomide class that selectively targets fungal dihydroorotate dehydrogenase (DHODH) causing inhibition of pyrimidine biosynthesis.

OBJECTIVE

We evaluated the in vitro activity of olorofim against 61 clinical isolates of the Fusarium oxysporum and F solani species complexes (FOSC and FSSC, respectively), the most prevalent causes of invasive fusariosis.

METHODS

Clinical isolates of FOSC (n = 45) and FSSC (n = 16) were identified using DNA sequence analysis of the translation elongation factor 1-alpha (TEF1α) and RNA polymerase II second largest subunit (RPB2). Antifungal susceptibility testing was performed by CLSI M38 broth microdilution for olorofim, amphotericin B, isavuconazole, posaconazole, voriconazole and micafungin.

RESULTS

Olorofim demonstrated good in vitro activity against both FOSC and FSSC. Against the 45 FOSC isolates, olorofim MICs ranged between 0.03-0.5 mg/L and 0.06->4 mg/L at the 50% and 100% inhibition endpoints, respectively. Against FSSC isolates, olorofim MIC ranged between 0.25-1 mg/L and 1->4 mg/L at 50% and 100% inhibition, respectively. While amphotericin B also demonstrated similar in vitro activity (MIC ranges 1-4 and 0.25-4 mg/L against FOSC and FSSC, respectively), neither the triazoles nor micafungin demonstrated consistent in vitro activity against Fusarium isolates at clinically relevant concentrations.

CONCLUSIONS

The investigational agent olorofim demonstrated good in vitro activity against FOSC and FSSC clinical isolates. Further studies are warranted to determine how well this in vitro activity translates into in vivo efficacy.

In Vitro Activity and In Vivo Efficacy of Cefiderocol against Stenotrophomonas maltophilia

Cefiderocol is a novel siderophore cephalosporin antibiotic with broad coverage against difficult-to-treat Gram-negative bacteria, including those resistant to carbapenems. Its activity against Stenotrophomonas maltophilia was investigated in vitro against clinical isolates and in lung infection models using strains either resistant (SR202006) or susceptible (SR201934, SR200614) to trimethoprim-sulfamethoxazole. Cefiderocol demonstrated potent in vitro activity against all 217 S. maltophilia clinical isolates tested (MIC50, 0.063 μg/ml; MIC90, 0.25 μg/ml). Cefiderocol also demonstrated low MICs against the trimethoprim-sulfamethoxazole-resistant S. maltophilia strains (i.e., SR202006; MIC, 0.125 μg/ml). In a neutropenic mouse lung infection model, cefiderocol (30 mg/kg body weight and 100 mg/kg) demonstrated a significant, dose-dependent reduction in the lung viable bacteria cell count compared with untreated controls in S. maltophilia infection and was the only antibiotic tested to show a similar significant effect in a trimethoprim-sulfamethoxazole-resistant S. maltophilia infection. In immunocompetent rat lung infection models of S. maltophilia, humanized dosing of cefiderocol (2 g every 8 h) and meropenem (1 g every 8 h) revealed pharmacokinetic profiles similar to those in human subjects, and the humanized cefiderocol dosing significantly reduced the lung viable bacteria cell count compared with baseline controls, which received no intervention. Together, the results from these studies suggest that cefiderocol could provide an effective alternative treatment option for S. maltophilia infections in the lower respiratory tract, particularly strains resistant to empirical antibiotics, such as trimethoprim-sulfamethoxazole or minocycline.

Fidaxomicin has high in vitro activity against Mycobacterium tuberculosis

This study aimed to evaluate whether the antibiotic fidaxomicin has in vitro activity against Mycobacterium tuberculosis (Mtb). 38 fully drug-sensitive Mtb strains and 34 multidrug-resistant tuberculosis (MDR-TB) strains were tested using the microplate alamar blue assay (MABA) method to determine the minimum inhibitory concentrations (MICs) for fidaxomicin and rifampicin. Fidaxomicin has high in vitro activity against Mtb and is a potential drug to treat Mtb, and MDR-TB infections in particular.

Tetrahydrophthalazinone Inhibitor of Phosphodiesterase with In Vitro Activity against Intracellular Trypanosomatids

The phosphodiesterase inhibitor tetrahydrophthalazinone NPD-008 was explored by phenotypic in vitro screening, target validation, and ultrastructural approaches against Trypanosoma cruzi NPD-008 displayed activity against different forms and strains of T. cruzi (50% effective concentration [EC₅₀], 6.6 to 39.5 μM). NPD-008 increased cAMP levels of T. cruzi and its combination with benznidazole gave synergistic interaction. It was also moderately active against intracellular amastigotes of Leishmania amazonensis and Leishmania infantum, confirming a potential activity profile as an antitrypanosomatid drug candidate.

Ibrexafungerp: A novel oral glucan synthase inhibitor

Ibrexafungerp is a novel glucan synthase inhibitor currently undergoing phase II and phase III clinical trials. This compound has demonstrated in vitro activity against clinically important fungal pathogens including Candida spp. and Aspergillus spp. It is able to retain activity against many echinocandin-resistant strains of Candida due to differential avidity for the target site compared to echinocandins. In vivo animal models have demonstrated efficacy in murine models of invasive candidiasis, aspergillosis, and pneumocystis. Due to high bioavailability, it can be administered both orally and intravenously. A favorable drug interaction and tolerability profile is observed with this compound. This review summarizes existing data that have either been published or presented at international symposia.

In Vitro Activity of Pentamidine Alone and in Combination with Antibiotics against Multidrug-Resistant Clinical Pseudomonas aeruginosa Strains

Multidrug-resistant (MDR) Pseudomonas aeruginosa is a public health problem causing both community and hospital-acquired infections, and thus the development of new therapies for these infections is critical. The objective of this study was to analyze in vitro the activity of pentamidine as adjuvant in combinations to antibiotics against seven clinical P. aeruginosa strains. The Minimum Inhibitory Concentration (MIC) was determined following standard protocols, and the results were interpreted according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints; however, the gentamicin activity was interpreted according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. The bactericidal in vitro activity was studied at 1×MIC concentrations by time-kill curves, and also performed in three selected strains at 1/2×MIC of pentamidine. All studies were performed in triplicate. The pentamidine MIC range was 400-1600 μg/mL. Four of the strains were MDR, and the other three were resistant to two antibiotic families. The combinations of pentamidine at 1×MIC showed synergistic activity against all the tested strains, except for pentamidine plus colistin. Pentamidine plus imipenem and meropenem were the combinations that showed synergistic activity against the most strains. At 1/2×MIC, pentamidine plus antibiotics were synergistic with all three analyzed strains. In summary, pentamidine in combination with antibiotics showed in vitro synergy against multidrug-resistant P. aeruginosa clinical strains, which suggests its possible use as adjuvant to antibiotics for the therapy of infections from MDR P. aeruginosa.

Activity of Omadacycline and Other Tetracyclines Against Contemporary Gram-Negative Pathogens from New York City Hospitals

Antibiotic-resistant Enterobacteriaceae and Acinetobacter baumannii are problematic pathogens, with few treatment options for multidrug-resistant (MDR)-A. baumannii and few oral options for extended spectrum β-lactamase (ESBL)-producing and MDR-Enterobacteriaceae. Omadacycline, a newer tetracycline derivative, has activity against some of these pathogens. We tested the in vitro activity of omadacycline against a contemporary collection of over 2,600 consecutive unique clinical isolates of Enterobacteriaceae and A. baumannii, a previous collection of carbapenem-resistant Klebsiella pneumoniae and A. baumannii from a surveillance study in 2013-2014, and a group of K. pneumoniae and A. baumannii isolates with previously defined resistance mechanisms. For the contemporary collection, over 96% of Escherichia coli and 70% of K. pneumoniae isolates were inhibited by omadacycline at ≤4 μg/mL including 95% of E. coli and 49% of K. pneumoniae with presumptive ESBLs. Nearly 90% of A. baumannii were inhibited by omadacycline at ≤4 μg/mL. The omadacycline MIC_50/90 was 1/4 μg/mL, 4/>8 μg/mL, and 0.5/8 for E. coli, K. pneumoniae, and A. baumannii, respectively. For the carbapenem-resistant collection of isolates, 56% of A. baumannii were inhibited by omadacycline at ≤4 μg/mL, but only 30% of Klebsiella pneumoniae carbapenemase (KPC)-possessing K. pneumoniae were susceptible. Expression of the efflux gene adeB appeared to affect the activity of omadacycline against A. baumannii, but could not fully explain resistance to this agent. Omadacycline may prove to be a parenteral or oral option for some infections due to ESBL-producing Enterobacteriaceae and carbapenem-resistant A. baumannii, and clinical studies are warranted.

Rezafungin In Vitro Activity against Contemporary Nordic Clinical Candida Isolates and Candida auris Determined by the EUCAST Reference Method

Rezafungin (formerly CD101) is a novel echinocandin in clinical development. EUCAST epidemiological cutoff values (ECOFFs) have not yet been established. We determined the in vitro activity of rezafungin and comparators against 1,293 Nordic yeast isolates and 122 Indian Candida auris isolates and established single-center wild-type upper limits (WT-UL). The isolates (19 Candida spp. and 13 other yeast species) were identified using Chromagar; matrix-assisted laser desorption ionization-time of flight (MALDI-TOF); and, when needed, internal transcribed spacer sequencing. EUCAST E.Def 7.3.1 susceptibility testing included rezafungin, anidulafungin, micafungin, amphotericin B, and fluconazole. WT-UL were established following EUCAST principles for visual and statistical ECOFF setting. fks target genes were sequenced for rezafungin non-wild-type isolates. EUCAST clinical breakpoints for fungi version 9.0 were adopted for susceptibility classification. Rezafungin had species-specific activity similar to that of anidulafungin and micafungin. On a milligram-per-liter basis, rezafungin was overall less active than anidulafungin and micafungin but equally or more active than fluconazole and amphotericin B against the most common Candida species, except C. parapsilosis We identified 37 (3.1%) rezafungin non-wild-type isolates of C. albicans (1.9%), C. glabrata (3.0%), C. tropicalis (2.7%), C. dubliniensis (2.9%), C. krusei (1.2%), and C. auris (14.8%). Alterations in Fks hot spots were found in 26/26 Nordic and 8/18 non-wild-type C. auris isolates. Rezafungin displayed broad in vitro activity against Candida spp., including C. auris Adopting WT-UL established here, few Nordic strains, but a significant proportion of C. auris isolates, had elevated MICs with mutations in fks target genes that conferred echinocandin cross-resistance. fks1 mutations raised rezafungin MICs notably less than anidulafungin and micafungin MICs in C. auris.

In vitro Activity of a New Fourth-Generation Cephalosporin, Cefoselis, Against Clinically Important Bacterial Pathogens in China

The objective of this study was to systematically evaluate the in vitro activity of cefoselis and other comparators against common bacterial pathogens collected from 18 hospitals across China. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method following Clinical and Laboratory Standards Institute (CLSI) guidelines. Cefoselis showed poor activity against extended-spectrum β-lactamase (ESBL)-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, with susceptibility rates of < 10% each, while the susceptibility rates of this antibiotic against non-ESBL-producing strains of these organisms were 100%, 94.3%, and 97.0%, respectively. Cefoselis exhibited susceptibility rates of 56.7–83.3% against other tested Enterobacteriaceae isolates. For Acinetobacter baumannii and Pseudomonas aeruginosa isolates, the susceptibility rates to cefoselis were 18.7% and 73.3%, respectively. All methicillin-resistant Staphylococcus aureus (MRSA) strains were resistant to cefoselis, while all methicillin-sensitive S. aureus (MSSA) strains were susceptible to this antibiotic. In conclusion, cefoselis showed good activity against non-ESBL-producing E. coli, K. pneumoniae, and P. mirabilis, MSSA, and was also potent against Enterobacteriaceae, P. aeruginosa, and Streptococcus.

Repurposing of Ribavirin as an Adjunct Therapy against Invasive Candida Strains in an In Vitro Study

The use of antifungal agents in clinical settings is limited by the appearance of drug resistance and adverse side effects. There is, therefore, an urgent need to develop new drugs to strengthen the treatment of invasive fungal diseases. The aim of this study is to describe the potential repurposing of ribavirin as an adjunct therapy against Candida spp. Primary screening of a Prestwick Chemical library against Candida albicans ATCC 90028 and fluconazole-resistant Candida albicans strains was performed. Subsequently, we evaluated the responses of 100 Candida sp. strains to ribavirin, an antiviral agent, using the broth microdilution method as recommended by CLSI. We checked the involvement of efflux pump activity in the development of ribavirin resistance. We studied time-kill curves and performed a checkerboard assay for a ribavirin-antifungal combination study. Twenty-one nonstandard antifungal compounds were identified, including ribavirin. Ribavirin had antifungal activity in vitro against 63 Candida strains, including strains of C. albicans, C. parapsilosis, and C. tropicalis, with MICs ranging from 0.37 to 3.02 μg/ml, while MICs for C. krusei, C. glabrata, C. lusitaniae, and some C. albicans strains remained high (≥24.16 μg/ml). No relation was observed between efflux pump activity and ribavirin resistance. Ribavirin exhibited fungistatic activity against multidrug-resistant (MDR) C. albicans and fungicidal activity against a C. parapsilosis strain. In addition, ribavirin acted synergistically with azoles against Candida strains for which ribavirin MICs were <24.4 μg/ml. This study highlights the potential clinical application of ribavirin, alone or in association with other antifungal agents, as an adjunct anti-Candida drug.

Effect of tedizolid on clinical Enterococcus isolates: in vitro activity, distribution of virulence factor, resistance genes and multilocus sequence typing

Enterococcal infections have become one of the most challenging nosocomial problems. Tedizolid, the second oxazolidinone, is 4-fold to 8-fold more potent in vivo and in vitro than linezolid against enterococci. However, the characteristics of tedizolid related to enterococci isolates in China remain elusive. The aim of this study was to evaluate in vitro activity of tedizolid against enterococcal isolates from patients with infections at a teaching hospital in China and to investigate the correlations between in vitro tedizolid activity against enterococci and the distribution of multilocus sequence types (MLST), resistance genes and virulence factors. A total of 289 non-duplicate Enterococcus faecalis strains and 68 E. faecium strains were isolated. Tedizolid inhibited 95.24% of all enterococcal isolates with an MIC ≤ 0.5μg/ml. Seventeen E. faecalis strains had an MIC > 0.5 μg/ml, and all E. faecium were inhibited at MIC ≤ 0.5 μg/ml. The proportion of tedizolid non-susceptible E. faecalis strains with optrA genes was higher than that among tedizolid-susceptible strains. Tedizolid exhibited good in vitro activity against all E. faecium strains, including multidrug-resistant E. faecium carrying tet(M), tet(L), tet(U),erm(A), erm(B) and erm(C) genes. In summary, tedizolid has an advantage (higher sensitivity rate) compared to linezolid among enterococci, except for isolates expressing the plasmid-encoded optrA gene.

Effect of the Plastein Reaction in Presence of Extrinsic Amino Acids on the Protective Activity of Casein Hydrolysate against Ethanol-Induced Damage in HHL-5 Cells

Casein hydrolysates (CH) were prepared using papain and modified by the plastein reaction (CH-P) in the presence of extrinsic phenylalanine (CH-P-Phe) or tryptophan (CH-P-Trp). The in vitro protective activity of CH and its modified products against ethanol-induced damage in HHL-5 cells was investigated. The results showed that the modification by the plastein reaction reduced the amino group content of CH. However, the modification by the plastein reaction in the presence of extrinsic amino acids could enhance the antioxidant, proliferative, cell cycle arresting, and anti-apoptosis activity of CH. Biological activities of CH and its modified products in the HHL-5 cells varied depending on the hydrolysate concentration (1, 2, and 3 mg/mL) and treatment time (24, 48, and 72 h). Generally, higher biological activities were found after cell treatment with CH or its modified products at concentration of 2 mg/mL for 48 h compared to other treatments. In addition, CH modified in the presence of tryptophan (CH-P-Trp) showed higher biological activity than that modified in the presence of phenylalanine (CH-P-Phe). Based on the obtained results, it can be concluded that casein hydrolysates with enhanced biological activity and potential health benefits can be produced by papain and the plastein reaction with the incorporation of extrinsic amino acids.

In Vitro Activity of Iclaprim against Isolates in Two Phase 3 Clinical Trials (REVIVE-1 and -2) for Acute Bacterial Skin and Skin Structure Infections

Iclaprim, a selective bacterial dihydrofolate reductase inhibitor, and other antibiotics were tested against Gram-positive isolates from two phase 3 studies of acute bacterial skin and skin structure infections (ABSSSIs) (REVIVE-1 and -2). Seven hundred ninety baseline isolates, including Staphylococcus aureus, β-hemolytic streptococci, and Streptococcus anginosus group, underwent antibacterial susceptibility testing. Iclaprim had an MIC₉₀ of 0.12 μg/ml for S. aureus (0.12 μg/ml for methicillin susceptible, 0.25 μg/ml for methicillin resistant), 0.25 μg/ml for β-hemolytic streptococci, and 0.008 μg/ml for S. anginosus group. Iclaprim demonstrated potent activity against these Gram-positive ABSSSI isolates.

Broad Bactericidal Activity of the Myoviridae Bacteriophage Lysins LysAm24, LysECD7, and LysSi3 against Gram-Negative ESKAPE Pathogens

The extremely rapid spread of multiple-antibiotic resistance among Gram-negative pathogens threatens to move humankind into the so-called “post-antibiotic era” in which the most efficient and safe antibiotics will not work. Bacteriophage lysins represent promising alternatives to antibiotics, as they are capable of digesting bacterial cell wall peptidoglycans to promote their osmotic lysis. However, relatively little is known regarding the spectrum of lysin bactericidal activity against Gram-negative bacteria. In this study, we present the results of in vitro activity assays of three putative and newly cloned Myoviridae bacteriophage endolysins (LysAm24, LysECD7, and LysSi3). The chosen proteins represent lysins with diverse domain organization (single-domain vs. two-domain) and different predicted mechanisms of action (lysozyme vs. peptidase). The enzymes were purified, and their properties were characterized. The enzymes were tested against a panel of Gram-negative clinical bacterial isolates comprising all Gram-negative representatives of the ESKAPE group. Despite exhibiting different structural organizations, all of the assayed lysins were shown to be capable of lysing Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Escherichia coli, and Salmonella typhi strains. Less than 50 μg/mL was enough to eradicate growing cells over more than five orders of magnitude. Thus, LysAm24, LysECD7, and LysSi3 represent promising therapeutic agents for drug development.

Prevalence of nontuberculous mycobacteria and high efficacy of d-cycloserine and its synergistic effect with clarithromycin against Mycobacterium fortuitum and Mycobacterium abscessus

Background

The prevalence of pulmonary disease caused by nontuberculous mycobacteria (NTM) is reportedly on the rise in the world. Some of the species are resistant to various antibiotics; hence, limited treatment options are available. The aims of this study were to investigate the prevalence of NTM and to determine the effect of d-cycloserine against Mycobacterium fortuitum and Mycobacterium abscessus isolated from clinical specimens to find out the synergistic effect of d-cycloserine and clarithromycin.

Methods

A total of 95 nonduplicate pulmonary isolates of NTM were collected from three major Regional Tuberculosis (TB) Centers. NTM isolates were identified by conventional tests and PCR sequence analysis of the rpoB gene. PCR sequencing of erm-41 was performed for detecting the inducible resistance to macrolides. In vitro susceptibilities and activities of d-cycloserine-clarithromycin combinations were accessed using the broth microdilution method.

Results

Among 714-positive acid-fast bacilli from TB-suspected cases, 95 isolates were identified as NTM (13.3%). The prevalence of identified isolates was as follows: M. fortuitum 46 (48.4%), Mycobacterium simiae 16 (16.8%), Mycobacterium kansasii 15 (15.7%), M. abscessus 7 (7.3%), Mycobacterium thermoresistibile 4 (4.2%), Mycobacterium elephantis 3 (3.2%), Mycobacterium porcinum 2 (2.1%), and Mycobacterium chimaera 2 (2.1%). In addition, rpoB sequence analysis could identify all NTM isolates. The effect of d-cycloserine was better than that of clarithromycin. The synergistic effect of d-cycloserine with clarithromycin was observed for six (100%) and five (71.5%) strains of M. fortuitum and M. abscessus, respectively.

Conclusion

In the present study, we demonstrated a wide range of NTM in processed samples from different provinces of Iran. Our observations indicated that d-cycloserine was very active against M. abscessus and M. fortuitum; hence, d-cycloserine, either alone or in combination with clarithromycin, may be promising for the treatment of M. abscessus- and M. fortuitum-associated diseases.

In vitro Activity of Pentamidine Alone and in Combination With Aminoglycosides, Tigecycline, Rifampicin, and Doripenem Against Clinical Strains of Carbapenemase-Producing and/or Colistin-Resistant Enterobacteriaceae

Enterobacteriaceae cause different types of community- and hospital-acquired infections. Moreover, the spread of multidrug-resistant Enterobacteriaceae is a public health problem and the World Health Organization pointed them among the pathogens in which the search of new antibiotics is critical. The objective of this study was to analyze the in vitro activity of pentamidine alone and in combination with gentamicin, tobramycin, amikacin, tigecycline, rifampicin, or doripenem against eight clinical strains of carbapenemase-producing and/or colistin-resistant Enterobacteriaceae: five carbapenemase-producing Klebsiella pneumoniae, one carbapenemase-producing Escherichia coli, and two colistin-resistant Enterobacter cloacae. MIC and MBC were determined following standard protocols. MIC results were interpreted for all the antibiotics according to the EUCAST breakpoints but for rifampicin in which the French FSM breakpoint was used. Bactericidal and synergistic activity of pentamidine alone and in combination with antibiotics at concentrations of 1xMIC was measured by time-kill curves. For one selected strain, K. pneumoniae OXA-48/CTX-M-15 time-kill curves were performed also at 1/2xMIC of pentamidine. All studies were performed in triplicate. Pentamidine MIC range was 200-800 μg/mL. The 50, 12.5, 62.5, 87.5, and 62.5% of the strains were susceptible to gentamicin, tobramycin, amikacin, tigecycline, and doripenem, respectively. Only the two E. cloacae strains were susceptible to rifampicin. Pentamidine alone at 1xMIC showed bactericidal activity against all strains, except for the E. cloacae 32 strain. The bactericidal activity of pentamidine alone was also observed in combination. The combinations of pentamidine were synergistic against E. cloacae 32 with amikacin and tobramycin at 24 h and with tigecycline at 8 h. Pentamidine plus rifampicin was the combination that showed synergistic activity against more strains (five out of eight). Pentamidine plus doripenem did not show synergy against any strain. At 1/2xMIC, pentamidine was synergistic with all the studied combinations against the K. pneumoniae OXA-48/CTX-M-15 strain. In summary, pentamidine alone and in combination shows in vitro activity against carbapenemase-producing and/or colistin-resistant Enterobacteriaceae. Pentamidine appears to be a promising option to treat infections caused by these pathogens.

In Vitro Activity of Newer and Conventional Antimicrobial Agents, Including Fosfomycin and Colistin, against Selected Gram-Negative Bacilli in Kuwait

Limited data are available on susceptibilities of these organisms to some of the recently made accessible antimicrobial agents. The in vitro activities of newer antibiotics, such as, ceftolozane/tazobactam (C/T) and ceftazidime/avibactam (CZA) along with some “older” antibiotics, for example fosfomycin (FOS) and colistin (CL) were determined against selected strains (resistant to ≥3 antimicrobial agents) of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Minimum inhibitory concentrations (MIC) were determined by Clinical and Laboratory Standards Institute microbroth dilution. 133 isolates: 46 E. coli, 39 K. pneumoniae, and 48 P. aeruginosa were tested. Results showed that E. coli isolates with MIC_50/90, 0.5/1 μg/mL for CL; 4/32 μg/mL for FOS; 0.25/32 μg/mL for C/T; 0.25/8 μg/mL for CZA, exhibited susceptibility rates of 95.7%, 97.8%, 76.1%, and 89.1%, respectively. On the other hand, K. pneumoniae strains with MIC_50/90, 0.5/1 μg/mL for CL; 256/512 μg/mL for FOS; 2/128 μg/mL for C/T; 0.5/128 μg/mL for CZA showed susceptibility rates of 92.3%, 7.7%, 51.3%, and 64.1%, respectively. P. aeruginosa isolates with MIC_50/90, 1/1 μg/mL for CL; 128/128 μg/mL for C/T; 32/64 μg/mL for CZA presented susceptibility rates of 97.9%, 33.3%, and 39.6%, respectively. Higher MICs were demonstrated against most of the antibiotics. However, CL retained efficacy at low MICs against most of the isolates tested.

In Vitro Activity of Ceftazidime-Avibactam against Isolates from Patients in a Phase 3 Clinical Trial for Treatment of Complicated Intra-abdominal Infections

The increasing prevalence of multidrug-resistant Gram-negative pathogens has generated a requirement for new treatment options. Avibactam, a novel non-β-lactam-β-lactamase inhibitor, restores the activity of ceftazidime against Ambler class A, C, and some class D β-lactamase-producing strains of Enterobacteriaceae and Pseudomonas aeruginosa The in vitro activities of ceftazidime-avibactam versus comparators were evaluated against 1,440 clinical isolates obtained in a phase 3 clinical trial in patients with complicated intra-abdominal infections (cIAI; ClinicalTrials.gov identifier NCT01499290). Overall, in vitro activities were determined for 803 Enterobacteriaceae, 70 P. aeruginosa, 304 Gram-positive aerobic, and 255 anaerobic isolates obtained from 1,066 randomized patients at baseline. Susceptibility was determined by broth microdilution. The most commonly isolated Gram-negative, Gram-positive, and anaerobic pathogens were Escherichia coli (n = 549), Streptococcus anginosus (n = 130), and Bacteroides fragilis (n = 96), respectively. Ceftazidime-avibactam was highly active against isolates of Enterobacteriaceae, with an overall MIC₉₀ of 0.25 mg/liter. In contrast, the MIC₉₀ for ceftazidime alone was 32 mg/liter. The MIC₉₀ value for ceftazidime-avibactam (4 mg/liter) was one dilution lower than that of ceftazidime alone (8 mg/liter) against isolates of Pseudomonas aeruginosa The ceftazidime-avibactam MIC₉₀ for 109 ceftazidime-nonsusceptible Enterobacteriaceae isolates was 2 mg/liter, and the MIC range for 6 ceftazidime-nonsusceptible P. aeruginosa isolates was 8 to 32 mg/liter. The MIC₉₀ values were within the range of susceptibility for the study drugs permitted per the protocol in the phase 3 study to provide coverage for aerobic Gram-positive and anaerobic pathogens. These findings demonstrate the in vitro activity of ceftazidime-avibactam against bacterial pathogens commonly observed in cIAI patients, including ceftazidime-nonsusceptible Enterobacteriaceae (This study has been registered at ClinicalTrials.gov under identifier NCT01499290.).

Anti-mycobacterium tuberculosis activity of polyherbal medicines used for the treatment of tuberculosis in Eastern Cape, South Africa

BACKGROUND

The emergence of drug-resistant strains of Mycobacterium tuberculosis has become a global public health problem. Polyherbal medicines offer great hope for developing alternative drugs for the treatment of tuberculosis.

OBJECTIVE

To evaluate the anti-tubercular activity of polyherbal medicines used for the treatment of tuberculosis.

METHODS

The remedies were screened against Mycobacterium tuberculosis H37Rv using Middlebrook 7H9 media and MGIT BACTEC 960 system. They were liquid preparations from King Williams Town site A (KWTa), King Williams Town site B (KWTb), King Williams Town site C (KWTc), Hogsback first site (HBfs), Hogsback second site (HBss), Hogsback third site (HBts), East London (EL), Alice (AL) and Fort Beaufort (FB).

RESULTS

The susceptibility testing revealed that all the remedies contain anti-tubercular activity with KWTa, KWTb, KWTc, HBfs, HBts, AL and FB exhibiting more activity at a concentration below 25 µl/ml. Furthermore, MIC values exhibited inhibitory activity with the most active remedies from KWTa, HBfs and HBts at 1.562 µg/ml. However, isoniazid showed more inhibitory activity against M. tuberculosis at 0.05 µg/ml when compare to the polyherbal remedies.

CONCLUSION

This study has indicated that these remedies could be potential sources of new anti-mycobacterial agents against M. tuberculosis. However, the activity of these preparations and their active principles still require in vivo study in order to assess their future as new anti-tuberculosis agents.

Do bacteria isolated from ICU patients 'ESKAPE' antibiotic treatment? In vitro susceptibility of the Enterobacteriaceae family to tigecycline

BACKGROUND

Enterobacteriaceae are currently causing the majority of healthcare-associated infections (HAI) and simultaneously expressing increasing levels of antibiotic resistance. The purpose of this study is to assess the in vitro sensitivity of MDR strains from the family Enterobacteriaceae to tigecycline in relation to their origin from patients hospitalized in intensive care units (ICUs) and non-ICUs.

METHODS

The study involved 156 clinically significant strains of the Enterobacteriaceae family isolated from patients with complicated intraabdominal infections (cIAIs) and/or complicated skin and skin structure infections (cSSSIs) hospitalized in ICUs and other surgical departments. Tigecycline MICs were determined by Etest.

RESULTS

The highest percentage of tigecycline non-susceptible (intermediate + resistant strains) in vitro strains among the Enterobacteriaceae species were observed for Serratia spp. 77.3%, followed by Citrobacter spp. (76.9%) and Enterobacter spp. (70%); whereas K. pneumoniae and E. coli showed 73-73.8% tigecycline susceptibility rates.

CONCLUSION

Tigecycline demonstrates a high level of antimicrobial in vitro activity when tested against E. coli and K. pneumoniae, even those with the ESBL-phenotype. Tigecycline retained activity against merely 22-30% of Enterobacter, Citrobacter and Serratia genera.

Ravuconazole self-emulsifying delivery system: in vitro activity against Trypanosoma cruzi amastigotes and in vivo toxicity

Self-emulsifying drug delivery systems (SEDDSs) are lipid-based anhydrous formulations composed of an isotropic mixture of oil, surfactant, and cosurfactants usually presented in gelatin capsules. Ravuconazole (Biopharmaceutics Classification System [BCS] Class II) is a poorly water-soluble drug, and a SEDDS type IIIA was designed to deliver it in a predissolved state, improving dissolution in gastrointestinal fluids. After emulsification, the droplets had mean hydrodynamic diameters <250 nm, zeta potential values in the range of −45 mV to −57 mV, and showed no signs of ravuconazole precipitation. Asymmetric flow field-flow fractionation with dynamic and multiangle laser light scattering was used to characterize these formulations in terms of size distribution and homogeneity. The fractograms obtained at 37°C showed a polydisperse profile for all blank and ravuconazole–SEDDS formulations but no large aggregates. SEDDS increased ravuconazole in vitro dissolution extent and rate (20%) compared to free drug (3%) in 6 h. The in vivo toxicity of blank SEDDS comprising Labrasol^® surfactant in different concentrations and preliminary safety tests in repeated-dose oral administration (20 days) showed a dose-dependent Labrasol toxicity in healthy mice. Ravuconazole–SEDDS at low surfactant content (10%, v/v) in Trypanosoma cruzi-infected mice was safe during the 20-day treatment. The anti-T. cruzi activity of free ravuconazole, ravuconazole–SEDDS and each excipient were evaluated in vitro at equivalent ravuconazole concentrations needed to inhibit 50% or 90% (IC₅₀ and IC₉₀), respectively of the intracellular amastigote form of the parasite in a cardiomyocyte cell line. The results showed a clear improvement of the ravuconazole anti-T. cruzi activity when associated with SEDDS. Based on our results, the repurposing of ravuconazole in SEDDS dosage form is a strategy that deserves further in vivo investigation in preclinical studies for the treatment of human T. cruzi infections.

Novel Sulfamethoxazole Ureas and Oxalamide as Potential Antimycobacterial Agents

Infections caused by Mycobacterium tuberculosis (Mtb.) and nontuberculous mycobacteria (NTM) are considered to be a global health problem; current therapeutic options are limited. Sulfonamides have exhibited a wide range of biological activities including those against mycobacteria. Based on the activity of 4-(3-heptylureido)-N-(5-methylisoxazol-3-yl)benzenesulfonamide against NTM, we designed a series of homologous sulfamethoxazole-based n-alkyl ureas (C₁–C₁₂), as well as several related ureas and an oxalamide. Fifteen ureas and one oxalamide were synthesized by five synthetic procedures and characterized. They were screened for their activity against Mtb. and three NTM strains (M. avium, M. kansasii). All of them share antimycobacterial properties with minimum inhibitory concentration (MIC) values starting from 2 µM. The highest activity showed 4,4′-[carbonylbis(azanediyl)]bis[N-(5-methylisoxazol-3-yl)benzenesulfonamide] with MIC of 2–62.5 µM (i.e., 1.07–33.28 µg/mL). Among n-alkyl ureas, methyl group is optimal for the inhibition of both Mtb. and NTM. Generally, longer alkyls led to increased MIC values, heptyl being an exception for NTM. Some of the novel derivatives are superior to parent sulfamethoxazole. Several urea and oxalamide derivatives are promising antimycobacterial agents with low micromolar MIC values.

Nanostructured lipid carriers for incorporation of copper(II) complexes to be used against Mycobacterium tuberculosis

Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis. Cessation of treatment before the recommended conclusion may lead to the emergence of multidrug-resistant strains. The aim of this study was to develop nanostructured lipid carriers (NLCs) for use in the treatment of M. tuberculosis. The NLCs comprised the following lipid phase: 2.07% polyoxyethylene 40 stearate, 2.05% caprylic/capric triglyceride, and 0.88% polyoxyl 40 hydrogenated castor oil; the following aqueous phase: 3.50% poloxamer 407 (F1-F6), and 0.50% cetyltrimethylammonium bromide (F7-F12); and incorporated the copper(II) complexes [CuCl₂(INH)₂]·H₂O (1), [Cu(NCS)₂(INH)₂]·5H₂O (2), and [Cu(NCO)₂(INH)₂]·4H₂O (3) to form compounds F11.1, F11.2, and F11.3, respectively. The mean diameter of F11, F11.1, F11.2, and F11.3 ranged from 111.27±21.86 to 134.25±22.72 nm, 90.27±12.97 to 116.46±9.17 nm, 112.4±10.22 to 149.3±15.82 nm, and 78.65±6.00 to 122.00±8.70 nm, respectively. The polydispersity index values for the NLCs ranged from 0.13±0.01 to 0.30±0.09. The NLCs showed significant changes in zeta potential, except for F11.2, with F11, F11.1, F11.2, and F11.3 ranging from 18.87±4.04 to 23.25±1.13 mV, 17.03±1.77 to 21.42±1.87 mV, 20.51±1.88 to 22.60±3.44 mV, and 17.80±1.96 to 25.25±7.78 mV, respectively. Atomic force microscopy confirmed the formation of nanoscale spherical particle dispersions by the NLCs. Differential scanning calorimetry determined the melting points of the constituents of the NLCs. The in vitro activity of copper(II) complex-loaded NLCs against M. tuberculosis H₃₇R_v showed an improvement in the anti-TB activity of 55.4, 27.1, and 41.1 times the activity for complexes 1, 2, and 3, respectively. An in vivo acute toxicity study of complex-loaded NLCs demonstrated their reduced toxicity. The results suggest that NLCs may be a powerful tool to optimize the activity of copper(II) complexes against M. tuberculosis.

Early investigational antibiotics for the treatment of acute exacerbations of chronic bronchitis

INTRODUCTION

Acute exacerbations in patients with chronic bronchitis are a leading cause of hospitalizations and death. Bacteria contribute significantly to such exacerbations. The aim of this review was to explore the potential role of investigational antibiotics in the treatment of these episodes. Areas covered: The available literature in PubMed database, in websites related to investigational drugs and in websites of the producing companies has been searched. The in vitro activity against pathogens involved in acute exacerbations of chronic bronchitis and the pharmacokinetic profile of antibiotics currently under development were taken into consideration for inclusion in the review. Expert opinion: Several novel antimicrobial agents have completed preclinical and Phase I studies and were well-tolerated. Further investigation is mandatory in order to evaluate their future in treatment of chronic bronchitis exacerbations and discover potential advantages compared to already approved antimicrobials.

In Vitro Activity of Ceftazidime-Avibactam against Isolates in a Phase 3 Open-Label Clinical Trial for Complicated Intra-Abdominal and Urinary Tract Infections Caused by Ceftazidime-Nonsusceptible Gram-Negative Pathogens

The in vitro activity of ceftazidime-avibactam was evaluated against 341 Gram-negative isolates from 333 patients in a randomized, phase 3 clinical trial of patients with complicated urinary tract or intra-abdominal infections caused by ceftazidime-nonsusceptible pathogens (NCT01644643). Ceftazidime-avibactam MIC₉₀ values against Enterobacteriaceae and Pseudomonas aeruginosa (including several class B or D enzyme producers that avibactam does not inhibit) were 1 and 64 μg/ml, respectively. Overall, the ceftazidime-avibactam activity against ceftazidime-nonsusceptible isolates was comparable to the activity of ceftazidime-avibactam previously reported against ceftazidime-susceptible isolates. (This study has been registered at ClinicalTrials.gov under identifier NCT01644643.).

Thioridazine: A Non-Antibiotic Drug Highly Effective, in Combination with First Line Anti-Tuberculosis Drugs, against Any Form of Antibiotic Resistance of Mycobacterium tuberculosis Due to Its Multi-Mechanisms of Action

This review presents the evidence that supports the use of thioridazine (TZ) for the therapy of a pulmonary tuberculosis infection regardless of its antibiotic resistance status. The evidence consists of in vitro and ex vivo assays that demonstrate the activity of TZ against all encountered Mycobacterium tuberculosis (Mtb) regardless of its antibiotic resistance phenotype, as well as in vivo as a therapy for mice infected with multi-drug resistant strains of Mtb, or for human subjects infected with extensively drug resistant (XDR) Mtb. The mechanisms of action by which TZ brings about successful therapeutic outcomes are presented in detail.

In vitro activity of Brucella melitensis isolates to various antimicrobials in Turkey

BACKGROUND

Brucellosis is a systemic infectious disease caused by Brucella bacteria. A successful treatment requires antibiotics that can penetrate into the cell at high concentrations. The aim of this study was to assess the biotype and in vitro activity of 80 Brucella isolates obtained from blood against various antimicrobials for human brucellosis in Turkey.

METHODS

Identification of the types of the species designated Brucella species was made using the polymerase chain reaction (PCR), with type-specific primers. Serotyping was performed using mono-specific A and M antisera. The minimum inhibitory concentrations (MICs) of antibiotics known to have good intracellular penetration (doxycycline, rifampicin, ofloxacin, levofloxacin, moxifloxacin, clarithromycin, and azithromycin) were determined by the agar dilution method.

RESULTS

All of the 80 Brucella isolates were determined to be Brucella melitensis: 75 B. melitensis biotype 3 (93.7%) and 5 B. melitensis biotype 1 (6.3%). Doxycycline was the most effective among the tested antibiotics against Brucella species (MIC(50)-MIC(90), 0.25-0.5 μg/ml), and it was followed by levofloxacin (MIC(50)-MIC(90), 0.5-1 μg/ml), moxifloxacin (MIC(50)-MIC(90), 1-1 μg/ml), ofloxacin (MIC(50)-MIC(90), 1-1 μg/ml), rifampicin (MIC(50)-MIC(90), 2-4 μg/ml), azithromycin (MIC(50)-MIC(90), 4-8 μg/ml), and clarithromycin (MIC(50)-MIC(90), 8-32 μg/ml), respectively.

CONCLUSIONS

The in vitro activity of doxycycline and rifampicin, which are used in the classic treatment of brucellosis, was found to be very good. Quinolones were found to have in vitro activity against Brucella isolates. Among the macrolides, azithromycin had a higher level of activity compared with clarithromycin. A combination of quinolones and azithromycin could be an alternative to doxycycline and rifampicin in the treatment of brucellosis.

In vitro evaluation of antiplasmodial activity of extracts of Acanthospermum hispidum DC (Asteraceae) and Ficus thonningii Blume (Moraceae), two plants used in traditional medicine in the Republic of Congo

The aim of this study was to evaluate extracts from two medicinal plants, Acanthospermum hispidum and Ficus thonningii, used in traditional medicine in Congo Brazzaville, for in vitro antiplasmodial activities against two laboratory strains of Plasmodium falciparum: the chloroquine sensitive 3D7 and the chloroquine resistant Dd2. ELISA HRP2 assay was used to evaluate the in vitro inhibitory activity of the extracts alone or in combination with chloroquine. Cytotoxicity was assessed on human HeLa cell line and reflected by the selectivity index. Methanolic extract of Acanthospermum hispidum exhibited a strong and a moderate inhibitory activity on the growth of Dd2 and 3D7 at 2.8 µg/ml and 9.2 µg/ml concentrations respectively with a selectivity index >10. The combination of the most active extract (methanolic extract of Acanthospermum hispidum) with chloroquine showed a synergistic interaction on both strains. The good selectivity index of Acanthospermum hispidum on HeLa cells reflects the safety of this plant. Extracts from Ficus thonningii did not show any promising antiplasmodial activity on both 3D7 and Dd2. Except the methanolic extract which exhibited a slight antiplasmodial activity with inhibitory concentration and selectivity index corresponding to 9.61 µg/ml and 11.16 respectively. Methanolic extract of Acanthospermum hispidum exhibited moderate to high inhibitory activity on 3D7 and Dd2 laboratory strains and a synergistic antimalarial effect when combined with chloroquine. Ficus thonningii seems to have no antimalarial activity. Phytochemical analysis, in vivo investigations using animal models and later clinical trials in collaboration with traditional practitioners are necessary to clarify the potential antimalarial activity of both plants.

Integrated analysis of three bacterial conjunctivitis trials of besifloxacin ophthalmic suspension, 0.6%: etiology of bacterial conjunctivitis and antibacterial susceptibility profile

Background

The purpose of this paper is to report on the bacterial species isolated from patients with bacterial conjunctivitis participating in three clinical trials of besifloxacin ophthalmic suspension, 0.6%, and their in vitro antibacterial susceptibility profiles.

Methods

Microbial data from three clinical studies, conducted at multiple clinical sites in the US and Asia were integrated. Species were identified at a central laboratory, and minimum inhibitory concentrations were determined for various antibiotics, including β-lactams, fluoroquinolones, and macrolides.

Results

A total of 1324 bacterial pathogens representing more than 70 species were isolated. The most common species were Haemophilus influenzae (26.0%), Streptococcus pneumoniae (22.8%), Staphylococcus aureus (14.4%), and Staphylococcus epidermidis (8.4%). H. influenzae was most frequently isolated among patients aged 1–18 years, while S. aureus was most prevalent among those >65 years. Drug resistance was prevalent: Of H. influenzae isolates, 25.3% were β-lactamase positive and 27.2% of S. pneumoniae isolates were penicillin-intermediate/ resistant; of S. aureus isolates, 13.7% were methicillin-resistant (MRSA), and of these, 65.4% were ciprofloxacin-resistant, while 45.9% of S. epidermidis isolates were methicillin-resistant (MRSE), and, of these, 47.1% were ciprofloxacin-resistant. Besifloxacin was more potent than comparator fluoroquinolones overall, and particularly against Gram-positive bacteria. Against ciprofloxacin-resistant MRSA and MRSE, besifloxacin was four-fold to ≥ 128-fold more potent than other fluoroquinolones.

Conclusions

While the pathogen distribution in bacterial conjunctivitis has not changed, drug resistance is increasing. Patient age and local antibiotic resistance trends should be considered in the treatment of this ocular infection. Besifloxacin showed broad-spectrum in vitro activity and was particularly potent against multidrug-resistant staphylococcal isolates.