Methicillin-resistant Research Articles

Genomic epidemiology and resistant genes of Acinetobacter baumannii clinical strains in Vietnamese hospitals.

Introduction. Acinetobacter baumannii is a common cause of multidrug-resistant (MDR) nosocomial infections worldwide, including Vietnam.Hypothesis. Analysis of crucial genetic factors may link to epidemiological characteristics and antibiotic resistance of A. baumannii clinical strains in Vietnamese hospitals.Methodology. Fifty-one A. baumannii clinical strains from six different tertiary hospitals in Vietnam were analysed using whole genome sequencing (WGS), between 2017 and 2019.Results. Eleven sequence types (STs) were identified, including four STs reported for the first time in Vietnam based on the PubMLST database and three new STs not previously documented. ST1336, ST1260 and ST575 were found exclusively in Vietnam. These STs were widely distributed in all hospitals in Vietnam, with ST2 and ST571 being the most dominant. Resistant rates to eight antibiotics, belonging to four antibiotic groups, were very high (72.5-94.1 %) with high MIC values, while resistance to colistin was 29.4%. Fifty-one isolates were identified as MDR, with 100% (51/51) isolates carrying antimicrobial-resistant (AMR) genes, and 52 antibiotic-resistant genes were detected among these strains, including β-lactam (22 genes), chloramphenicol (5 genes), lincosamide (2 genes), aminoglycoside (11 genes), rifampicin (1 gene), quinolone (2 genes), sulfonamide and trimethoprim (4 genes) and tetracycline (5 genes) resistance. The most commonly found mobile structures carried partial or complete transposons: ISaba24/ISEc29/ISEc35 contains a series of antibiotic-resistant genes.Conclusion. The WGS results of the 51 strains of A. baumannii provided important information regarding the distribution of STs and associated antibiotic-resistant genes among A. baumannii strains.

Bacterial etiology, antibiotic susceptibility pattern, and treatment modality of surgical site infections among post-caesarean delivery women: A 2019 cross-sectional study conducted in Iringa, Tanzania

Background: Surgical site infection (SSI) is a common complication after cesarean section in Tanzania, with high rates of infection and multidrug-resistant isolates reported. Understanding bacterial etiology and antibiotic susceptibility patterns is crucial for effective treatment and prevention. Therefore, this study aimed to determine the bacterial etiology, antibiotic susceptibility patterns, and treatment modalities of SSI among post-cesarean delivery women in the Iringa region. Methods: A cross-sectional study involving 162 women with SSI was conducted across five hospitals in Iringa. Data on demographics were collected using a structured questionnaire, and wound discharge samples were taken for culture and sensitivity testing. Definitive treatment modalities were identified from patients’ files. Data analysis was performed using SPSS version 20, with chi-square tests used to identify associations, and a p-value < 0.05 considered significant. Results: Among 162 participants, 59.7% had superficial SSIs and 35.2% had deep SSIs. Culture positivity was 96.3%, with 53.2% being gram-positive and 37.2% gram-negative. Staphylococcus aureus was the most commonly isolated pathogen (40.1%), with 64.6% of cases being methicillin-resistant (MRSA). Resistance to vancomycin and chloramphenicol among gram-positive isolates was 3.1% and 13.8%, respectively. Non-surgical management was provided to 58% of the participants, while Staphylococcus aureus infections were significantly associated with surgical intervention (OR = 1.38, p = 0.001). Conclusion: Staphylococcus aureus, particularly MRSA, was the most prevalent pathogen in post-cesarean SSIs. Antibiotic resistance was common, and surgical intervention was significantly associated with Staphylococcus aureus infections.

Genomic characterization of a clonal emergent Salmonella Minnesota lineage in Brazil reveals the presence of a novel megaplasmid of resistance and virulence.

Salmonella Minnesota has emerged in Brazil as the predominant serovar in poultry and poultry products, along with Salmonella Heidelberg. To understand the emergence of Salmonella Minnesota over the last few years in Brazil, we performed a comparative analysis between 69 selected S. Minnesota genomes from Pathogen Detection database and 65 clonal emergent genomes isolated from Brazil. We demonstrate the presence of multidrug resistance genes against tetracycline [tet(A)], sulfonamide (sul2), and AmpC beta-lactamase (blaCMY-2) in emergent genomes, along with the carriage of a megaplasmid of resistance and virulence (~210 kb), designated pESM (plasmid for emergent Salmonella Minnesota). pESM is an IncC/A2 plasmid predicted to increase S. Minnesota environmental tolerance to mercury (mer operon) and provide resistance to tetracycline and ampicillin due to the presence of tet(A) and blaCMY-2, respectively. Moreover, pESM carries the yersiniabactin siderophore (high-pathogenicity island of Yersinia) related to the iron uptake. The temporal inference demonstrated that the most recent common ancestor dated from ~1978 and that the clonal emergent genomes carrying the pESM belong to a completely different lineage of S. Minnesota. Our results indicate that the presence of pESM likely contributes to the emergence of S. Minnesota and is precisely related to the successful spread of this particular clonal lineage in Brazil.IMPORTANCESalmonella Minnesota has emerged in Brazil as one of the leading serovars related to human and animal infection, presenting high virulence and antibiotic resistance to drugs classified as the highest priority for clinical treatment in humans. This study performed whole-genome sequencing, temporal analysis, and phylogenetics to understand the genetic insights related to the emergence of Salmonella Minnesota in Brazil. Long-read sequencing has led to the identification and characterization of a unique megaplasmid carrying virulence, antibiotic resistance, and heavy-metal tolerance genes, which may play a central role in S. Minnesota's successful emergence in Brazil and possibly worldwide. The potentially high transmissibility of this plasmid between clones and serovars represents a risk to public health since its acquisition may increase Salmonella's fitness, virulence, resistance, and persistence. Understanding the genetic aspects related to the emergence of serovars can help devise measures to mitigate the spread of hazardous multidrug-resistant strains.

Self-assembly antimicrobial peptide for treatment of multidrug-resistant bacterial infection

The wide-spreading of multidrug resistance poses a significant threat to human and animal health. Although antimicrobial peptides (AMPs) show great potential application, their instability has severely limited their clinical application. Here, self-assembled AMPs composed of multiple modules based on the principle of associating natural marine peptide N6 with ß-sheet-forming peptide were designed. It is noteworthy that one of the designed peptides, FFN could self-assemble into nanoparticles at 35.46 µM and achieve a dynamic transformation from nanoparticles to nanofibers in the presence of bacteria, resulting in a significant increase in stability in trypsin and tissues by 1.72–57.5 times compared to that of N6. Additionally, FFN exhibits a broad spectrum of antibacterial activity against multidrug-resistant (MDR) gram-positive (G+) and gram-negative (G−) bacteria with Minimum inhibitory concentrations (MICs) as low as 2 µM by membrane destruction and complemented by nanofiber capture. In vivo mouse mastitis infection model further confirmed the therapeutic potential and promising biosafety of the self-assembled peptide FFN, which can effectively alleviate mastitis caused by MDR Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and eliminate pathogenic bacteria. In conclusion, the design of peptide-based nanomaterials presents a novel approach for the delivery and clinical translation of AMPs, promoting their application in medicine and animal husbandry.Graphical

Anti-quorum sensing activity of essential oils against multidrug-resistant Klebsiella pneumoniae: a novel approach to control bacterial virulence.

The increasing resistance of microbes to conventional drugs is a serious problem worldwide that has increased the need for alternative antimicrobial compounds. Naturally occurring essential oils (EOs) are considered an important component of traditional pharmacopeia because of their antimicrobial and antioxidant properties. This has attracted researchers to identify novel therapeutic anti-pathogenic agents that could act as non-toxic quorum sensing inhibitors, thus controlling infections without encouraging the development of bacterial resistance. This prompted to undertake the current investigation to unravel the efficacy of EOs as QS modulators in reducing the virulence of multidrug resistant (MDR) strains ofKlebsiella pneumoniae. The study highlighted the anti-QS activity of fifteen EOs in modulating the QS-related traits by a reduction in capsular polysaccharide, exopolysaccharide and siderophore production in addition to inhibition of biofilm formation. The overall results suggest using EOs to develop alternate intervention strategies to mitigate infections caused by MDR strains ofK. pneumoniae.

Chemical Space for Peptide-based Antimicrobials.

Multidrug-resistant (MDR) bacteria represent a global public health threat, and antimicrobial peptides (AMPs), derived from naturally occurring linear or cyclic peptides, can provide the solution. However, most AMPs are sensitive to proteases and have poor pharmacokinetics. The EU-funded ERC Advanced Grant SPACE4AMPS aims to identify new AMPs by applying the concepts of chemical space and ligand-based virtual screening, which are well known for small molecule drug discovery, to the world of peptides. We create virtual libraries of peptides and related molecules and use these approaches to select a few tens of compounds for synthesis and detailed. evaluation of antibacterial, toxicity and stability effects. Recent results and prospects of this ongoing project are presented in this review.

Molecular Characterization and Antibiogram of <i>Pseudomonas aeruginosa</i> Isolated from Fish Sold in Markets of Tirupati, India

Pseudomonas aeruginosa is an emerging opportunistic pathogen and is one of the pathogens in the acronym ESKAPE representing a global threat to human health associated with antimicrobial resistance. The present study aimed for molecular characterization, virulence gene profiling and antimicrobial resistance studies of P. aeruginosa isolated from 200 fish samples collected from different fish markets in Tirupati, Andhra Pradesh, India. Of the 200 fish samples screened, 30.5% were confirmed as P. aeruginosa by PCR, targeting the 16S rRNA gene. Among the positive isolates, it was found that 70.4% and 75.4% of the isolates harbored toxA and exoS virulence markers, respectively. All 61 P. aeruginosa isolates recovered were phenotypically characterized for antimicrobial resistance patterns by the disc diffusion method. The study has found 100% resistance against erythromycin followed by 98.4% resistance to amoxicillin, 91.8% resistance against tetracycline, 88.5% resistance to vancomycin and cotrimoxazole, 45.9% resistance to ciprofloxacin, 44.2% resistance against cefepime and 9.9% resistance to gentamicin. The MAR indices were in the range from 0.5 to 1.0. The prevalence of multiple antibiotic resistance of P. aeruginosa harboringvirulence genes in fish can pose a serious threat and hazard to public health through the consumption of raw or undercooked fish.

High prevalence of carbapenem-resistant Enterobacter cloacae complex in a tertiary hospital over a decade.

The emergence and spread of the carbapenem-resistant Enterobacter cloacae complex (CRECC) have become a significant public health problem. CRECC strains frequently harbor multiple drug resistance genes and can be epidemic within healthcare facilities. The study explored the characteristics and prevalence of CRECC strains in the same hospital over a decade, which provides a theoretical basis for epidemiologic surveillance and clinical treatment.

Antibiotic resistance and the search for resistance and virulence genes in Escherichia coli strains isolated from agropastoral farms (Poultry, Cattle, and Fish) In Southern Benin

Resistance of animal-origin enterobacteria to antibiotics is experiencing a concerning global increase, with an escalating impact of extended-spectrum beta-lactamases (ESBL). Finding solutions to this problem requires reliable and diverse data. It is in this context that the present study was initiated to combat infections caused by Escherichia coli in agropastoral farms (poultry, cattle, and fish) in southern Benin. Samples consisting of cattle dung, poultry droppings, as well as water and sludge from fish farms were aseptically collected for various laboratory analyses. A total of 714 E. coli strains were isolated from 1,376 collected samples, with 434 strains from the Atlantique department and 280 strains from the Zou department. The isolation of strains was carried out according to the NF V08-050: 2009 standard. The identified strains were tested against various antibiotics using the Bauer and Kirby disk diffusion method on agar, as recommended by the WHO. Strains resistant to one or more antibiotics were selected for the search for resistance and virulence genes. Furthermore, multidrug resistance of the strains to antibiotics was also observed, particularly in the Beta-lactam class (100% resistance to AMC) and tetracyclines (90% resistance to tetracyclines). Additionally, genotypic detection revealed a total absence of virulence genes, whereas resistance genes such as beta-lactamase Sulfhydryl Variable (bla-SHV), beta-lactamase Temoniera (bla-TEM), and quinolone resistance gene B (qnrB) were more frequently detected at respectively 58%, 82% and 60%.

Seven-year overview of antimicrobial resistance in diarrheagenic Escherichia coli from sporadic human diarrhea cases in 20 Chinese provinces

Diarrheagenic Escherichia coli is one of the most prevalent foodborne pathogens and poses significant clinical challenges due to increasing rates of antibiotic resistance. In this study, 9,068 diarrheagenic E. coli isolates from sporadic diarrhea cases across 20 provinces of China from 2016 to 2022 were systematically analyzed to determine the prevalence and distribution of resistance. A total of 14 antibiotics were included in the antimicrobial resistance surveillance. Antimicrobial susceptibility testing indicated that the majority of the isolates (89.3%) were resistant to at least one antimicrobial agent, with a significant proportion (60.3%) demonstrating multidrug resistance. Isolates showed high levels of resistance to ampicillin (68.2%) and high sensitivity to imipenem (97.0%). Over the 7 years, an increasing trend in resistance to cefoxitin and chloramphenicol among the isolates was found. Enteroaggregative E. coli was identified as the predominant pathotype. Furthermore, antimicrobial resistance rates were higher among the isolates from infants under 1 year of age compared to other populations and resistance levels differed among pathotypes. In summary, our findings revealed the detailed resistance characteristics of diarrheagenic E. coli strains isolated from human sporadic diarrhea cases in China, offering valuable insights that can inform clinical antibiotic treatment strategies and priorities.

A Case Report on Multi Drug Resistance in Community Acquired Pneumonia Due to Escherichia coli with Cholangiocarcinoma

Escherichia coli is an important cause of severe community acquired pneumonia with mortality higher than pneumococcal pneumonia but like other gram-negative pneumonia. Antibiotics are the treatment of choice in treating pneumonia. When it comes to bacterial community-acquired pneumonia, multidrug resistant Escherichia coli (MDR E. Coli) is a less common cause than Staphylococcus aureus and Streptococcus pneumoniae. The majority of patients with community-acquired pneumonia (CAP) respond well to typical antibiotic regimens consisting of either a fluoroquinolone or a macrolide plus cephalosporin. We present a case where patient diagnosed with E. coli causing pneumonia showed MDR to various empirical antibiotics and managed with culture sensitive antibiotics. Antibiotic resistance has become a major issue for healthcare providers, where the effective management of patients will be more challenging which necessitates the need for optimising the use of antibiotics. Keywords: Multi Drug Resistance, Community Acquired Pneumonia, Escherichia Coli, Cholangiocarcinoma.

The Hope Therapy Effect Toward Depression, Anxiety, and Stress of Tuberculosis Patients with Multi-Drug Resistance at Jayapura’s Healthcare Center, Papua

Background: Indonesia is the third country with a high-rate case of tuberculosis with multi-drug resistance, for a percentage of 5% per 100.000 population. In Papua, TB-MDR becomes the main problem of health with a successful percentage of medication at 68.7%, an indicator of WHO higher than 85%. The complexity and the prolonged occurrence make the patients to have mental health illnesses, such as depression, anxiety, and stress. The field data of depression cases consisted of 65 patients. 50% with had mild depression, 20% with moderate, and 25.55 with severe. Patients with anxiety ranged from 16.7% to 37.29%. Patients with severe stress consisted of 20%. The mental illness health problems for TB-MDR patients required the roles of the nurses, such as counseling based on HOPE therapy. Purpose: Analyzed the effects of HOPE therapy to manage depression, anxiety, and stress levels. Methods: Quasi-experimental research applied a systematically assigned control group. The population consisted of patients with TB-MDR receiving medication at Jayapura's healthcare center, 40 individuals. Results: HOPE therapy effects for depression, stress, and anxiety levels applied the Wilcoxon test. The obtained result was a p-value lower than 0.05. The results indicated the effect of HOPE therapy medication on depression, stress, and anxiety levels. The intervention group had decreased depression, stress, and anxiety levels with p-values of 0.043 and 0.012. The results contradicted the control group. The obtained p-value was higher than 0.05, indicating no effect. The p-values were 0.721, 0.532, and 0.670. Conclusion: HOPE therapy was useful for TB-MDR patients with mental illness. The administered HOPE therapy for patients could improve their confidence and hopes to live better and recover.

Computational prediction of a phage cocktail active against multidrug-resistant bacteria

Background Antibiotic misuse and overuse have contributed to the emergence of multi-drug resistant (MDR) bacteria, posing a serious public health problem across the globe. Phage cocktails, which combine multiple phages, provide an efficient method to combat multidrug-resistant bacterial infections. This study integrated a computational pipeline to design a phage cocktail against the bacterial strains Acinetobacter baumannii AB0057, Klebsiella pneumoniae subsp. pneumoniae HS11286, and Pseudomonas aeruginosa UCBPP-PA14. Methods The whole genome sequences of selected multidrug-resistant bacteria were accessed. Prophage sequences were identified from them which could be expressed to produce viable lytic phages against MDR bacterial strains, thereby reducing the severity of infection. Prophages were annotated for open reading frames (ORFs), putative promoters, virulence factors, transcriptional terminators, ribosomal RNAs, and transfer RNAs. A dot plot was also generated to investigate similar phages and phylogenetic analysis was performed. Results A total of 11 prophages were predicted from the bacterial genomes. About 472 open reading frames were predicted along with 3 transfer RNAs. Additionally, the presence of 754 putative promoters and 281 transcription terminator sequences was also detected. Comparative genomic and phylogenetic analyses provided insight into the diversity, relatedness, and lytic potential of the phages. The final designed phage cocktail consisted of five selected prophages including Acinetobacter baumannii prophages (2759376-2809756) and (3311844-3364667), and Klebsiella pneumoniae prophages (1288317-1338719), (1778306-1808606), and (2280703-2325555). Conclusion The phage cocktail designed in this study might be useful against MDR Acinetobacter baumannii and Klebsiella pneumoniae infections, especially where conventional antibiotics fail. Sequence similarity analysis suggested that the phage cocktail may also be effective against other carbapenemase-producing K. pneumoniae strains.

Novel plasmid-mediated CMY variant (CMY-192) conferring ceftazidime-avibactam resistance in multidrug-resistant Escherichia coli.

The rapid rise of multidrug resistance (MDR) among Gram-negative bacteria has accelerated the development of novel therapies. Ceftazidime-avibactam (CZA) is a novel β-lactam/β-lactamase inhibitor recently approved for the treatment of limited infectious diseases. Here, we describe a novel CMY variant, CMY-192, that confers high-level resistance to CZA. This gene was detected in a clinical MDR Escherichia coli strain (Ec73552) isolated from an outpatient with a community-acquired urinary tract infection who had not received prior CZA treatment. Ec73552 was typed as O101:H9-ST10, a high-risk clone associated with human and animal diseases. Ec73552 was able to colonize the bladder in a mouse model, suggesting that this strain was uropathogenic. CMY-192 shared the highest amino acid identity (98.95%) with CMY-172 and conferred at least a 32-fold increase in CZA MIC (from ≤0.125/4 to 8/4 mg/L) when cloned into a CZA-susceptible E. coli DH5α strain. Knockout of CMY-192 in Ec73552 resulted in a 256-fold reduction in CZA MIC (from 64/4 to 0.25/4 mg/L). CMY-192 was encoded on an IncB/O/K/Z-type plasmid (pCMY192). Conjugation assays confirmed that pCMY192 was self-transmissible, resulting in a 256-fold increase in the CZA MIC of the recipient. Notably, pCMY192 cured in Ec73552 did not confer a growth advantage, while the conjugant exhibited reduced biomass and growth rate, indicating that fitness costs imposed by pCMY192 may have been compensated in Ec73552. Our findings highlight the importance of continuous monitoring of CZA susceptibility to prevent the spread of resistance in clinical settings.

Antimicrobial activity of α/β hybrid peptides incorporating tBu-β3,3Ac6c against methicillin-resistant Staphylococcus aureus.

The incorporation of β-amino acids into peptides is a promising approach to develop proteolytically stable therapeutic agents. Short α/β hybrid peptidescontaining tBu-β3,3Ac6cː H2N-Lys-tBu-β3,3Ac6c-PEA, P1; H2N-Orn-tBu-β3,3Ac6c-PEA, P2; H2N-Arg-tBu-β3,3Ac6c-PEA, P3; LA-Lys-tBu-β3,3Ac6c-PEA, P4; LA-Orn-tBu-β3,3Ac6c-PEA, P5; LA-Arg-tBu-β3,3Ac6c-PEA, P6; LAu-Lys-tBu-β3,3Ac6c-PEA, P7; LAu-Orn-tBu-β3,3Ac6c-PEA, P8; and LAu-Arg-tBu-β3,3Ac6c-PEA, P9 were prepared. The antimicrobial efficacies of all the peptides were evaluated against ESKAPE pathogens, along with a small panel of multi-drug resistant (MDR) clinical isolates of S. aureus. Among all the peptides, P4, P6, and P7 showed significant efficacies against P. aeruginosa, S. aureus, and MRSA with an MIC value ranging from 6.25 to 12.5 μM. Further, in vitro, anti-staphylococcal assessment with their antimicrobial synergy of the peptides P4, P6, and P7 was carried out against MRSA, due to its better efficacy. The peptides P6 and P7 exhibited MRSA biofilm inhibition of 70% and 77%, respectively, at 4×MIC concentration. At its MIC concentration, about 19% hemolysis was observed for P4, P6, and P7.

Injecting drug use is a risk factor for methicillin resistance in patients with Staphylococcus aureus bloodstream infections.

We investigated whether injecting drug use was a risk factor for methicillin resistance among inpatients with Staphylococcus aureus bloodstream infections (SABSIs) at an Australian health service. In 273 inpatients, 46 (16.9%) of SABSIs were methicillin-resistant S. aureus (MRSA). MRSA was more frequent in those who had injected drugs in the past 6 months (20.6%) compared with other inpatients (15.7%). Injecting drug use was associated with a 4.82-fold (95% confidence interval = 1.54-16.29) increased odds of MRSA after accounting for confounders.

A recent update on the antibacterial effects ofdistinct bioactive molecules derived from theCannabis plant.

The number of human infections with multidrug-resistant (MDR) bacteria is increasing worldwide and constitutes a serious threat to human health. Given the lack of novel antibiotic compounds worsening this dilemma, alternative antibiotic-independent treatment and prevention strategies of infectious diseases applying natural compounds appear highly appreciable. Given the long-known health-beneficial and disease-alleviating properties of Cannabis, we performed a literature search summarizing current knowledge regarding the antibacterial effects of extracts from different parts of the Cannabis sativa plant and of defined Cannabis-derived molecules and their potential mode of action. Theincluded studies revealed that various extracts and essential oils of C. sativa as well as major cannabinoids exerted potent activities against a broad spectrum of Gram-positive bacteria and against some Gram-negative bacterial species including MDR strains. Particularly the disruption of the bacterial cytoplasmic membrane by some cannabinoids resulted in potent antibacterial effects against Gram-positivebacteria including methicillin-resistant Staphylococcus aureus. Furthermore, defined cannabinoids inhibited the formation of and eradicated existing bacterial biofilms. In conclusion, given their antibacterial properties distinct Cannabis-derived molecules expand the repertoire of antibiotics-independent treatment options in the combat of bacterial infectious diseases which should be further addressed in future studies including clinical trials.

Liposomal formulation with thiazolic compounds against bacterial efflux pumps

This study aimed to evaluate the effects of liposome-encapsulated eugenol-based thiazolic derivatives against efflux pump-carrying bacteria. The Minimum Inhibitory Concentration (MIC) was determined to evaluate the antibacterial activity and antibiotic potentiation against Pseudomonas aeruginosa and Staphylococcus aureus, as well as to analyze the inhibition of efflux pumps in S. aureus strains 1199B and K2068 in the ethidium bromide assay. The direct antibacterial activity analysis showed no clinically relevant results since the compounds presented MICs ≥1024 µg/mL. Regarding the analysis of antibiotic potentiation against multidrug-resistant (MDR) strains of S. aureus, compound LF16 reduced norfloxacin MIC from 128 µg/mL to 64 µg/mL. All associated with gentamicin caused a significant antibiotic MIC reduction. None of the compounds could potentate the activity of norfloxacin against P. aeruginosa. However, all of them potentiated the activity of gentamicin against the same strain. Only the LF 26 caused a significant MIC reduction in the ethidium bromide assay, suggesting efflux inhibition in the S. aureus 1199B strain. Similar results were observed with the K2068 strain. Observing antibiotic MIC reduction S. aureus strains carrying the NorA and MepA proteins brought additional evidence of efflux pump inhibition. Our results indicate that while eugenol-based thiazoles didn't exhibit direct activity, they can potentiate the antibiotics activity against MDR strains of P. aeruginosa and S. aureus. Among them, compound LF 26 potentiated the inhibitory effects of ethidium bromide and antibiotics against S. aureus strains carrying the NorA and MepA proteins, indicating a potential role of this class of compounds as efflux pump inhibitors.

Multidrug tolerance conferred by loss-of-function mutations in anti-sigma factor RshA of Mycobacterium abscessus.

Low-level drug resistance in noncanonical pathways can constitute steppingstones toward acquisition of high-level on-target resistance mutations in the clinic. To capture these intermediate steps in Mycobacterium abscessus (Mab), we performed classic mutant selection experiments with moxifloxacin at twofold its minimum inhibitory concentration (MIC) on solid medium. We found that low-level resistance emerged reproducibly as loss-of-function mutations in RshA (MAB_3542c), an anti-sigma factor that negatively regulates activity of SigH, which orchestrates a response to oxidative stress in mycobacteria. Since oxidative stress is generated in response to many antibiotics, we went on to show that deletion of rshA confers low to moderate resistance-by measure of MIC-to a dozen agents recommended or evaluated for the treatment of Mab pulmonary infections. Interestingly, this moderate resistance was associated with a wide range of drug tolerance, up to 1,000-fold increased survival of a ΔrshA Mab mutant upon exposure to several β-lactams and DNA gyrase inhibitors. Consistent with the putative involvement of the SigH regulon, we showed that addition of the transcription inhibitor rifabutin (RBT) abrogated the high-tolerance phenotype of ΔrshA to representatives of the β-lactam and DNA gyrase inhibitor classes. In a survey of 10,000 whole Mab genome sequences, we identified several loss-of-function mutations in rshA as well as non-synonymous polymorphisms in two cysteine residues critical for interactions with SigH. Thus, the multidrug multiform resistance phenotype we have uncovered may not only constitute a step toward canonical resistance acquisition during treatment but also contribute directly to treatment failure.

Activity of protegrin-1 against mouse Ehrlich ascites carcinoma <i>in vitro</i> and <i>in vivo</i>

BACKGROUND: The problem of multidrug resistance in cancer treatment creates an urgent demand for developing new effective antitumor agents. Due to the unusual mechanism of recognizing and damaging tumor cells, antimicrobial peptides are considered as possible prototypes for designing such therapeutics. AIM: This work was aimed to compare the antitumor potential of the promising membranolytic antimicrobial peptide protegrin-1 in vitro and in vivo in Ehrlich ascites carcinoma mice model. MATERIALS AND METHODS: We used two variants of the model by inducing a tumor in solid or ascites form. In the first case, the mice were injected with the peptide twice a week for three weeks, and in the second injections were provided every other day for six days. The activity of antimicrobial peptides against isolated Ehrlich ascites carcinoma cells in vitro was analyzed using MTT-test. RESULTS: Protegrin-1 demonstrated high activity against Ehrlich ascites carcinoma cells in vitro, but had no significant effect on the lifespan of mice bearing solid or ascites form of Ehrlich tumor at the dosing and administration regimens we used. However, treatment with protegrin-1 caused a decrease in the ascites volume and in the number of cells in the ascites fluid. CONCLUSIONS: Protegrin-1 retains its antitumor properties in vivo, but it may be presumed, that to effectively suppress tumor growth it requires a more frequent and prolonged administration compared with conventional antitumor antibiotics, of which we adopted the administration regimen for protegrin-1 in this study.