Mechanisms of resistance and clinical relevance of resistance to β-lactams, glycopeptides, and fluoroquinolones

Clinical Characteristics and Risk Factors for Infection and Death in Critically Ill Patients with Pulmonary Infection with Elizabethkingia Spp

Purpose

Elizabethkingia spp. infections have recently increased, and they are difficult to treat because of intrinsic antimicrobial resistance. This study aimed to investigate the clinical characteristics of patients with pulmonary infection with Elizabethkingia spp. and reveal the risk factors for infection and death.

Patients and Methods

In this retrospective case-control study, patients were divided into infection and control groups based on the bacterial identification results. Patients in the infection group were further divided into survival and death groups according to their hospital outcomes. Clinical characteristics between different groups were compared. We further analyzed antimicrobial susceptibility testing results of the isolated strains.

Results

A total of the 316 patients were divided into infection (n = 79), 23 of whom died, and control (n = 237) groups. Multivariate logistic regression analysis showed that glucocorticoid consumption (OR: 2.35; 95% CI: 1.14-4.81; P = 0.02), endotracheal intubation (OR: 3.74; 95% CI: 1.62-8.64; P = 0.002), and colistin exposure (OR: 2.50; 95% CI: 1.01-6.29; P = 0.046) were significantly associated with pulmonary infection with Elizabethkingia spp. Advanced age (OR: 1.07, 95% CI: 1.00-1.15; P = 0.046), high acute physiology and chronic health evaluation (APACHE) II score (OR: 1.21; 95% CI: 1.01-1.45; P = 0.037), and low albumin level (OR: 0.73, 95% CI: 0.56-0.96; P = 0.025) were significantly associated with in-hospital mortality of infected patients. Elizabethkingia spp. was highly resistant to cephalosporins, carbapenems, macrolides, and aminoglycoside, and was sensitive to fluoroquinolones, minocycline, and co-trimoxazole in vitro.

Conclusion

Glucocorticoid consumption, tracheal intubation, and colistin exposure were associated with pulmonary infection with Elizabethkingia spp. for critically ill patients. Patients with advanced age, high APACHE II score, and low albumin level had higher risk of death from infection.

Dual site reactivity of indole-3-Schiff bases with S/Se/Cl substituted ketenes for stereoselective C-4 substituted indole-β-lactams, biological evaluations, magic chloro effect and molecular docking studies

A convenient methodology for C-4 indole-β-lactam hybrids with chloro, sulphur and seleno substitutions through dual site reactivity of indole-3-Schiff bases towards ketenes has been developed. The reaction proceeded in a stereospecific manner with the exclusive formation of trans-β-lactams assigned with respect to C3-H and C4-H. The synthesized novel β-lactams have been characterized with the help of elemental analysis (CHNS) and spectroscopic techniques viz.1H NMR, 13C NMR, DEPT 135, HSQC and IR. The trans configuration was further estabilished based on X-ray crystallographic data. Examination of antibacterial properties unveiled that only derivatives 5a and 5b, featuring chloro substitution, exhibited potent activities, underscoring the emergence of the recently coined term "magic chloro effect". Molecular docking analysis provided additional support for the observed in vitro antibacterial activities of compounds 5a-b.

Decoding antimicrobial resistance: unraveling molecular mechanisms and targeted strategies

Antimicrobial resistance poses a significant global health threat, necessitating innovative approaches for combatting it. This review explores various mechanisms of antimicrobial resistance observed in various strains of bacteria. We examine various strategies, including antimicrobial peptides (AMPs), novel antimicrobial materials, drug delivery systems, vaccines, antibody therapies, and non-traditional antibiotic treatments. Through a comprehensive literature review, the efficacy and challenges of these strategies are evaluated. Findings reveal the potential of AMPs in combating resistance due to their unique mechanisms and lower propensity for resistance development. Additionally, novel drug delivery systems, such as nanoparticles, show promise in enhancing antibiotic efficacy and overcoming resistance mechanisms. Vaccines and antibody therapies offer preventive measures, although challenges exist in their development. Non-traditional antibiotic treatments, including CRISPR-Cas systems, present alternative approaches to combat resistance. Overall, this review underscores the importance of multifaceted strategies and coordinated global efforts to address antimicrobial resistance effectively.

Novel spore-forming species exhibiting intrinsic resistance to third- and fourth-generation cephalosporins and description of Tigheibacillus jepli gen. nov., sp. nov

A comprehensive microbial surveillance was conducted at NASA's Mars 2020 spacecraft assembly facility (SAF), where whole-genome sequencing (WGS) of 110 bacterial strains was performed. One isolate, designated 179-BFC-A-HST, exhibited less than 80% average nucleotide identity (ANI) to known species, suggesting a novel organism. This strain demonstrated high-level resistance [minimum inhibitory concentration (MIC) >256 mg/L] to third-generation cephalosporins, including ceftazidime, cefpodoxime, combination ceftazidime/avibactam, and the fourth-generation cephalosporin cefepime. The results of a comparative genomic analysis revealed that 179-BFC-A-HST is most closely related to Virgibacillus halophilus 5B73CT, sharing an ANI of 78.7% and a digital DNA-DNA hybridization (dDDH) value of 23.5%, while their 16S rRNA gene sequences shared 97.7% nucleotide identity. Based on these results and the recent recognition that the genus Virgibacillus is polyphyletic, strain 179-BFC-A-HST is proposed as a novel species of a novel genus, Tigheibacillus jepli gen. nov., sp. nov (type strain 179-BFC-A-HST = DSM 115946T = NRRL B-65666T), and its closest neighbor, V. halophilus, is proposed to be reassigned to this genus as Tigheibacillus halophilus comb. nov. (type strain 5B73CT = DSM 21623T = JCM 21758T = KCTC 13935T). It was also necessary to reclassify its second closest neighbor Virgibacillus soli, as a member of a novel genus Paracerasibacillus, reflecting its phylogenetic position relative to the genus Cerasibacillus, for which we propose Paracerasibacillus soli comb. nov. (type strain CC-YMP-6T = DSM 22952T = CCM 7714T). Within Amphibacillaceae (n = 64), P. soli exhibited 11 antibiotic resistance genes (ARG), while T. jepli encoded for 3, lacking any known β-lactamases, suggesting resistance from variant penicillin-binding proteins, disrupting cephalosporin efficacy. P. soli was highly resistant to azithromycin (MIC >64 mg/L) yet susceptible to cephalosporins and penicillins.

IMPORTANCE

The significance of this research extends to understanding microbial survival and adaptation in oligotrophic environments, such as those found in SAF. Whole-genome sequencing of several strains isolated from Mars 2020 mission assembly cleanroom facilities, including the discovery of the novel species Tigheibacillus jepli, highlights the resilience and antimicrobial resistance (AMR) in clinically relevant antibiotic classes of microbes in nutrient-scarce settings. The study also redefines the taxonomic classifications within the Amphibacillaceae family, aligning genetic identities with phylogenetic data. Investigating ARG and virulence factors (VF) across these strains illuminates the microbial capability for resistance under resource-limited conditions while emphasizing the role of human-associated VF in microbial survival, informing sterilization practices and microbial management in similar oligotrophic settings beyond spacecraft assembly cleanrooms such as pharmaceutical and medical industry cleanrooms.

Assessment of Antibiotic Resistance among Clinical Isolates of Enterobacteriaceae in Nepal

Clinicians face a global challenge treating infections caused by Enterobacteriaceae because of the high rate of antibiotic resistance. This cross-sectional study from the Nepal Armed Police Force Hospital, Kathmandu, Nepal, characterized resistance patterns in Enterobacteriaceae across different antimicrobial classes and assessed incidences of multidrug-resistant (MDR) and extensively drug-resistant (XDR) infections. Enterobacteriaceae from clinical samples were isolated on blood and MacConkey agar, except for urine samples on cysteine lactose electrolyte-deficient agar. To determine antimicrobial susceptibility patterns, including MDR and XDR, the Kirby-Bauer disc diffusion method was used. Statistics were performed using SPSS, v. 17.0. Members of the family were identified in 14.5% (95% CI: 16.2-12.8%) of the total samples (N = 1,617), primarily in urine (54.7%, 128/234), blood (19.7%, 46/234), and sputum (15.0%, 35/234). Escherichia coli (n = 118, 44.2%) was the most predominant bacteria, followed by Citrobacter freundii (n = 81, 30.3%). As much as 95.6% (392/410) of the isolates were penicillin-resistant, whereas only 36.2% (290/801) were carbapenem-resistant. A total of 96 (36.0%) MDR and 98 (36.7%) XDR Enterobacteriaceae were identified. Proteus mirabilis (44.4%, 8/18) predominated MDR cultures, whereas C. freundii (53.1%, 43/81) predominated XDR cultures. Multidrug resistant (38.4%, 71/154) and XDR Enterobacteriaceae (22.7%, 35/154) were chiefly uropathogens. Fluoroquinolone resistance rates in non-MDR, MDR, and XDR isolates were 19.9%, 63.2%, and 96.2%, respectively, whereas cephalosporin resistance rates were 28.6%, 72.9%, and 95.4% and penicillin resistance rates were 67.0%, 97.4%, and 98.0%. One-seventh of patients visiting the hospital were found to be infected with Enterobacteriaceae, and of these patients, at least one-fourth were infected with MDR strains.

Methicillin-Resistant Staphylococcusaureus Strains Isolated from Burned Patients in a Tunisian Hospital: Molecular Typing, Virulence Genes, and Antimicrobial Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major causes of a variety of infections in hospitals and the community. Their spread poses a serious public health problem worldwide. Nevertheless, in Tunisia and other African countries, very little molecular typing data on MRSA strains is currently available. In our study, a total of 64 MRSA isolates were isolated from clinical samples collected from burned patients hospitalized in the Traumatology and Burns Center of Ben Arous in Tunisia. The identification of the collection was based on conventional methods (phenotypic and molecular characterization). The characterization of the genetic support for methicillin resistance was performed by amplification of the mecA gene by polymerase chain reaction (PCR), which revealed that 78.12% of S. aureus harbors the gene. The resistance of all the collection to different antibiotic families was studied. Indeed, the analysis of strain antibiotic susceptibility confirmed their multi-resistant phenotype, with high resistance to ciprofloxacin, gentamicin, penicillin, erythromycin, and tetracycline. The resistance to the last three antibiotics was conferred by the blaZ gene (73.43%), the erm(C) gene (1.56%), the msr(A) gene (6.25%), and tet(M) gene (7.81%), respectively. The clonal diversity of these strains was studied by molecular typing of the accessory gene regulator (agr) system, characterization of the SCCmec type, and spa-typing. The results revealed the prevalence of agr types II and III groups, the SCCmec type III and II cassettes, and the dominance of spa type t233. The characterization of the eight enterotoxins genes, the Panton-Valentine leukocidin and the toxic shock syndrome toxin, was determined by PCR. The percentage of virulence genes detected was for enterotoxins (55%), tst (71.88%), leukocidin E/D (79.69%), and pvl (1.56%) factors. Furthermore, our results revealed that the majority of the strains harbor IEC complex genes (94%) with different types. Our findings highlighted the emergence of MRSA strains with a wide variety of toxins, leukocidin associated with resistance genes, and specific genetic determinants, which could constitute a risk of their spread in hospitals and the environment and complicate infection treatment.

Awareness and Knowledge of Antimicrobial Resistance, Antimicrobial Stewardship and Barriers to Implementing Antimicrobial Susceptibility Testing among Medical Laboratory Scientists in Nigeria: A Cross-Sectional Study

Background: Antimicrobial resistance (AMR) is now considered one of the greatest global health threats. This is further compounded by a lack of new antibiotics in development. Antimicrobial stewardship programmes can improve and optimize the use of antibiotics, thereby increasing the cure rates of antibiotic treatment and decreasing the problem of AMR. In addition, diagnostic and antimicrobial stewardships in the pathology laboratories are useful tools to guide clinicians on patient treatment and to stop the inappropriate use of antibiotics in empirical treatment or narrow antibiotics. Medical Laboratory Scientists are at the forefront of performing antibiotics susceptibility testing in pathology laboratories, thereby helping clinicians to select the appropriate antibiotics for patients suffering from bacterial infections. Methods: This cross-sectional study surveyed personal antimicrobial usage, the knowledge and awareness on AMR, and antimicrobial stewardship, as well as barriers to antimicrobial susceptibility testing among medical laboratory scientists in Nigeria using pre-tested and validated questionnaires administered online. The raw data were summarized and exported in Microsoft Excel and further analyzed using IBM SPSS version 26. Results: Most of the respondents were males (72%) and 25-35 years old (60%). In addition, the BMLS degree was the highest education qualification most of the respondents (70%) achieved. Of the 59.2% of the respondents involved in antibiotics susceptibility testing, the disc diffusion method was the most commonly used (67.2%), followed by PCR/Genome-based detection (5.2%). Only a small percentage of respondents used the E-test (3.4%). The high cost of testing, inadequate laboratory infrastructure, and a lack of skilled personnel are the major barriers to performing antibiotics susceptibility testing. A higher proportion of a good AMR knowledge level was observed in male respondents (75%) than females (42.9%). The knowledge level was associated with the respondent's gender (p = 0.048), while respondents with a master's degree were more likely to possess a good knowledge level of AMR (OR: 1.69; 95% CI: 0.33, 8.61). Conclusion: The findings of this study indicate that Nigerian medical laboratory scientists had moderate awareness of AMR and antibiotic stewardship. It is necessary to increase investments in laboratory infrastructure and manpower training, as well as set up an antimicrobial stewardship programme to ensure widespread antibiotics susceptibility testing in hospitals, thereby decreasing empirical treatment and the misuse of antibiotics.

Antibiotics and Bacterial Resistance-A Short Story of an Endless Arms Race

Despite the undisputed development of medicine, antibiotics still serve as first-choice drugs for patients with infectious disorders. The widespread use of antibiotics results from a wide spectrum of their actions encompassing mechanisms responsible for: the inhibition of bacterial cell wall biosynthesis, the disruption of cell membrane integrity, the suppression of nucleic acids and/or proteins synthesis, as well as disturbances of metabolic processes. However, the widespread availability of antibiotics, accompanied by their overprescription, acts as a double-edged sword, since the overuse and/or misuse of antibiotics leads to a growing number of multidrug-resistant microbes. This, in turn, has recently emerged as a global public health challenge facing both clinicians and their patients. In addition to intrinsic resistance, bacteria can acquire resistance to particular antimicrobial agents through the transfer of genetic material conferring resistance. Amongst the most common bacterial resistance strategies are: drug target site changes, increased cell wall permeability to antibiotics, antibiotic inactivation, and efflux pumps. A better understanding of the interplay between the mechanisms of antibiotic actions and bacterial defense strategies against particular antimicrobial agents is crucial for developing new drugs or drug combinations. Herein, we provide a brief overview of the current nanomedicine-based strategies that aim to improve the efficacy of antibiotics.

Recent developments in detection and therapeutic approaches for antibiotic-resistant bacterial infections

Owing to the widespread emergence and proliferation of antibiotic-resistant bacteria, the therapeutic benefits of antibiotics have been reduced. In addition, the ongoing evolution of multidrug-resistant pathogens poses a challenge for the scientific community to develop sensitive analytical methods and innovative antimicrobial agents for the detection and treatment of drug-resistant bacterial infections. In this review, we have described the antibiotic resistance mechanisms that occur in bacteria and summarized the recent developments in detection strategies for monitoring drug resistance using different diagnostic methods in three aspects, including electrostatic attraction, chemical reaction, and probe-free analysis. Additionally, to understand the effective inhibition of drug-resistant bacterial growth by recent nano-antibiotics, the underlying antimicrobial mechanisms and efficacy of biogenic silver nanoparticles and antimicrobial peptides, which have shown promise, and the rationale, design, and potential improvements to these methods are also highlighted in this review. Finally, the primary challenges and future trends in the rational design of facile sensing platforms and novel antibacterial agents against superbugs are discussed.

Isolation, Identification, and Genetic Characterization of Antibiotic Resistance of Salmonella Species Isolated from Chicken Farms

Salmonella is a major cause of foodborne outbreaks. It causes gastroenteritis in humans and animals. This micro-organism causes severe illness in chickens and has a major impact on chicken productivity and the poultry industry. This study aimed to address the prevalence of Salmonella infection in broiler chicken farms in Kafrelsheikh, Gharbia, and Menofeya provinces in Egypt during 2020-2022. This work also aimed to evaluate the genetic characterization and antibiotic resistance of the isolated Salmonella strains. Clinical signs and mortalities were observed and recorded. In total, 832 samples were collected from 52 broiler flocks, including 26 from both one-week-old and 6-week-old chicken farms from different organs (liver, intestinal content, spleen, and gallbladder). The prevalence of Salmonella infections was reported in the study region to be 36.54%. Of the 26 one-week-old farms surveyed, 11 (42.31%) and 8/26 (30.77%) of the six-week-old broiler chicken farms had Salmonella infections. Recovered isolates were serotyped as 9 (47.37%) S. enteritidis O 1,9,12, ad monophasic H: g, m: -, 6 (31.58.%) S. shangani 2, (10.53%) S. gueuletapee 1, (5.26%) S. II (salamae), and 1 (5.26%) untypable. The results showed that Salmonella infection was predominant in one-week-old chicks compared to infection in six-week-old and uninfected flocks. All Salmonella isolates were resistant to ampicillin and erythromycin, while all isolates were sensitive to ciprofloxacin, chloramphenicol, and levofloxacin. The isolates also contained 10.53% (2/19) streptomycin, 10.53% (2/21) gentamicin, 15.79% (3/19) doxycycline, and 26.32% (5/19) lincomycin and colistin. The phenotypically resistant Salmonella samples against ampicillin, erythromycin, and macrolide harbored bla _TEM , bla _SHV , ermB, ereA, mphA, and ermB, respectively. This baseline data on Salmonella spp. prevalence, serotyping, and antibiotic profiles are combined to define the antimicrobial resistance to this endemic disease. Elucidation of the mechanisms underlying this drug resistance should be of general importance in understanding both the treatment and prevention of Salmonella infection in this part of Egypt.

Advances in the screening of antimicrobial compounds using electrochemical biosensors: is there room for nanomaterials?

The abusive use of antimicrobial compounds and the associated appearance of antimicrobial resistant strains are a major threat to human health. An improved antimicrobial administration involves a faster diagnosis and detection of resistances. Antimicrobial susceptibility testing (AST) are the reference techniques for this purpose, relying mainly in the use of culture techniques. The long time required for analysis and the lack of reproducibility of these techniques have fostered the development of high-throughput AST methods, including electrochemical biosensors. In this review, recent electrochemical methods used in AST have been revised, with particular attention on those used for the evaluation of new drug candidates. The role of nanomaterials in these biosensing platforms has also been questioned, inferring that it is of minor importance compared to other applications.

Prevalence of Antimicrobial Resistance Genes in Salmonella Typhi: A Systematic Review and Meta-Analysis

Salmonella enterica serovar Typhi (S. Typhi) that has developed resistance to many antimicrobials poses a serious challenge to public health. Hence, this study aimed to systematically determine the prevalence of antimicrobial resistance (AMR) in S. Typhi isolated from the environment and humans as well as to ascertain the spread of the selected AMR genes in S. Typhi. This systematic review and meta-analysis were performed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines, and the study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO). A total of 2353 studies were retrieved from three databases, of which 42 studies fulfilled the selection criteria. The pooled prevalence of AMR S. Typhi (using a random-effect model) was estimated at 84.8% (95% CI; 77.3−90.2), with high heterogeneity (I2: 95.35%, p-value < 0.001). The high estimated prevalence indicates that control methods should be improved immediately to prevent the spread of AMR among S. Typhi internationally.

Medicinal Chemistry of Inhibitors Targeting Resistant Bacteria

The discovery of antibiotics was a revolutionary feat that provided countless health benefits. The identification of penicillin by Alexander Fleming initiated the era of antibiotics, represented by constant discoveries that enabled effective treatments for the different classes of diseases caused by bacteria. However, the indiscriminate use of these drugs allowed the emergence of resistance mechanisms of these microorganisms against the available drugs. In addition, the constant discoveries in the 20th century generated a shortage of new molecules, worrying health agencies and professionals about the appearance of multidrug-resistant strains against available drugs. In this context, the advances of recent years in molecular biology and microbiology have allowed new perspectives in drug design and development, using the findings related to the mechanisms of bacterial resistance to generate new drugs that are not affected by such mechanisms and supply new molecules to be used to treat resistant bacterial infections. Besides, a promising strategy against bacterial resistance is the combination of drugs through adjuvants, providing new expectations in designing new antibiotics and new antimicrobial therapies. Thus, this manuscript will address the main mechanisms of bacterial resistance under the understanding of medicinal chemistry, showing the main active compounds against efflux mechanisms, and also the application of the use of drug delivery systems, and finally, the main potential natural products as adjuvants or with promising activity against resistant strains.

Molecular characterization of multidrug-resistant ESKAPEE pathogens from clinical samples in Chonburi, Thailand (2017-2018)

BACKGROUND

ESKAPEE pathogens Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Escherichia coli are multi-drug resistant (MDR) bacteria that present increasing treatment challenges for healthcare institutions and public health worldwide.

METHODS

431 MDR ESKAPEE pathogens were collected from Queen Sirikit Naval Hospital, Chonburi, Thailand between 2017 and 2018. Species identification and antimicrobial resistance (AMR) phenotype were determined following CLSI and EUCAST guidelines on the BD Phoenix System. Molecular identification of antibiotic resistant genes was performed by polymerase chain reaction (PCR), real-time PCR assays, and whole genome sequencing (WGS).

RESULTS

Of the 431 MDR isolates collected, 1.2% were E. faecium, 5.8% were S. aureus, 23.7% were K. pneumoniae, 22.5% were A. baumannii, 4.6% were P. aeruginosa, 0.9% were Enterobacter spp., and 41.3% were E. coli. Of the 401 Gram-negative MDR isolates, 51% were carbapenem resistant, 45% were ESBL producers only, 2% were colistin resistance and ESBLs producers (2%), and 2% were non-ESBLs producers. The most prevalent carbapenemase genes were bla_OXA-23 (23%), which was only identified in A. baumannii, followed by bla_NDM (17%), and bla_OXA-48-like (13%). Beta-lactamase genes detected included bla_TEM, bla_SHV, bla_OXA, bla_CTX-M, bla_DHA, bla_CMY, bla_PER and bla_VEB. Seven E. coli and K. pneumoniae isolates showed resistance to colistin and carried mcr-1 or mcr-3, with 2 E. coli strains carrying both genes. Among 30 Gram-positive MDR ESKAPEE, all VRE isolates carried the vanA gene (100%) and 84% S. aureus isolates carried the mecA gene.

CONCLUSIONS

This report highlights the prevalence of AMR among clinical ESKAPEE pathogens in eastern Thailand. E. coli was the most common MDR pathogen collected, followed by K. pneumoniae, and A. baumannii. Carbapenem-resistant Enterobacteriaceae (CRE) and extended spectrum beta-lactamases (ESBLs) producers were the most common resistance profiles. The co-occurrence of mcr-1 and mcr-3 in 2 E. coli strains, which did not affect the level of colistin resistance, is also reported. The participation of global stakeholders and surveillance of MDR remain essential for the control and management of MDR ESKAPEE pathogens.

The Biochemical Mechanisms of Antimicrobial Photodynamic Therapy

The unbridled dissemination of multidrug-resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological, and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose-dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by 3 different methods and showed a dose-dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community towards the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy.

Insights into structure and activity relationship of clinically mutated PER1 and PER2 class A β-lactamase enzymes

PER1 and PER2 are among the class A β-lactamase enzymes, which have evolved clinically to form antibiotic resistance and have significantly expanded their spectrum of activity. Hence, there is a need to study the clinical mutation responsible for such β-lactamase mediated antibiotic resistance. Alterations in catalytic centre and Ω-loop structure could be the cause of antibiotic resistance in these β-lactamase enzymes. Structural and functional alterations are caused due to mutations on or near the catalytic centre, which results in active site plasticity and are responsible for its expanded spectrum of activity in these class A β-lactamase enzymes. Multiple sequence alignment, structure, kinetic, molecular docking, MMGBSA and molecular dynamic simulation comparisons were done on 38 clinically mutated and wild class A β-lactamase enzymes. This work shows that PER1 and PER2 enzymes contains most unique mutations and have altered Ω-loop structure, which could be responsible for altering the structure-activity relationship and extending the spectrum of activity of these enzymes. Alterations in molecular docking, MMGBSA, kinetic values reveals the modification in the binding and activity of these clinically mutated enzymes with antibiotics. Further, the cause of these alterations can be revealed by active site interactions and H-bonding pattern of these enzymes with antibiotics. Met69Gln, Glu104Thr, Tyr105Trp, Met129His, Pro167Ala, Glu168Gln, Asn170His, Ile173Asp and Asp176Gln mutations were uniquely found in PER1 and PER2 enzymes. These mutations occurs at catalytic important residues and results in altered interactions with β-lactam antibiotics. Hence, these mutations could be responsible for altering the structure-activity of PER1 and PER2 enzymes.

Genomic and resistome analysis of Alcaligenes faecalis strain PGB1 by Nanopore MinION and Illumina Technologies

Background

Drug-resistant bacteria are important carriers of antibiotic-resistant genes (ARGs). This fact is crucial for the development of precise clinical drug treatment strategies. Long-read sequencing platforms such as the Oxford Nanopore sequencer can improve genome assembly efficiency particularly when they are combined with short-read sequencing data.

Results

Alcaligenes faecalis PGB1 was isolated and identified with resistance to penicillin and three other antibiotics. After being sequenced by Nanopore MinION and Illumina sequencer, its entire genome was hybrid-assembled. One chromosome and one plasmid was assembled and annotated with 4,433 genes (including 91 RNA genes). Function annotation and comparison between strains were performed. A phylogenetic analysis revealed that it was closest to A. faecalis ZD02. Resistome related sequences was explored, including ARGs, Insert sequence, phage. Two plasmid aminoglycoside genes were determined to be acquired ARGs. The main ARG category was antibiotic efflux resistance and β-lactamase (EC 3.5.2.6) of PGB1 was assigned to Class A, Subclass A1b, and Cluster LSBL3.

Conclusions

The present study identified the newly isolated bacterium A. faecalis PGB1 and systematically annotated its genome sequence and ARGs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08507-7.

A qnr-plasmid allows aminoglycosides to induce SOS in Escherichia coli

The plasmid-mediated quinolone resistance (PMQR) genes have been shown to promote high-level bacterial resistance to fluoroquinolone antibiotics, potentially leading to clinical treatment failures. In Escherichia coli, sub-minimum inhibitory concentrations (sub-MICs) of the widely used fluoroquinolones are known to induce the SOS response. Interestingly, the expression of several PMQR qnr genes is controlled by the SOS master regulator, LexA. During the characterization of a small qnrD-plasmid carried in E. coli, we observed that the aminoglycosides become able to induce the SOS response in this species, thus leading to the elevated transcription of qnrD. Our findings show that the induction of the SOS response is due to nitric oxide (NO) accumulation in the presence of sub-MIC of aminoglycosides. We demonstrated that the NO accumulation is driven by two plasmid genes, ORF3 and ORF4, whose products act at two levels. ORF3 encodes a putative flavin adenine dinucleotide (FAD)-binding oxidoreductase which helps NO synthesis, while ORF4 codes for a putative fumarate and nitrate reductase (FNR)-type transcription factor, related to an O₂-responsive regulator of hmp expression, able to repress the Hmp-mediated NO detoxification pathway of E. coli. Thus, this discovery, that other major classes of antibiotics may induce the SOS response could have worthwhile implications for antibiotic stewardship efforts in preventing the emergence of resistance.

Photodynamic inactivation (PDI) as a promising alternative to current pharmaceuticals for the treatment of resistant microorganisms

Although the whole world is currently observing the global battle against COVID-19, it should not be underestimated that in the next 30 years, approximately 10 million people per year could be exposed to infections caused by multi-drug resistant bacteria. As new antibiotics come under pressure from unpredictable resistance patterns and relegation to last-line therapy, immediate action is needed to establish a radically different approach to countering resistant microorganisms. Among the most widely explored alternative methods for combating bacterial infections are metal complexes and nanoparticles, often in combination with light, but strategies using monoclonal antibodies and bacteriophages are increasingly gaining acceptance. Photodynamic inactivation (PDI) uses light and a dye termed a photosensitizer (PS) in the presence of oxygen to generate reactive oxygen species (ROS) in the field of illumination that eventually kill microorganisms. Over the past few years, hundreds of photomaterials have been investigated, seeking ideal strategies based either on single molecules (e.g., tetrapyrroles, metal complexes) or in combination with various delivery systems. The present work describes some of the most recent advances of PDI, focusing on the design of suitable photosensitizers, their formulations, and their potential to inactivate bacteria, viruses, and fungi. Particular attention is focused on the compounds and materials developed in our laboratories that are capable of killing in the exponential growth phase (up to seven logarithmic units) of bacteria without loss of efficacy or resistance, while being completely safe for human cells. Prospectively, PDI using these photomaterials could potentially cure infected wounds and oral infections caused by various multidrug-resistant bacteria. It is also possible to treat the surfaces of medical equipment with the materials described, in order to disinfect them with light, and reduce the risk of nosocomial infections.

In vitro activity of the orally bioavailable ceftibuten/VNRX-7145 (VNRX-5236 etzadroxil) combination against a challenge set of Enterobacterales pathogens carrying molecularly characterized β-lactamase genes

Objectives

This study assessed the activity of ceftibuten, ceftibuten combined with the active form (VNRX-5236) of the β-lactamase inhibitor VNRX-7145 and comparators against a challenge set of Gram-negative pathogens.

Methods

Two hundred and five Enterobacterales carrying plasmid AmpC (53 isolates), ESBL (50), KPC (50), OXA-48-like (49) or OXA-48-like with KPC (3) encoding genes were selected. Susceptibility was determined by broth microdilution. VNRX-5236 and avibactam were tested at a fixed concentration of 4 mg/L.

Results

Ceftibuten/VNRX-5236 (MIC_50/90 0.12/1 mg/L) MIC values were 256-fold lower than those of ceftibuten (MIC_50/90 32/256 mg/L) for all Enterobacterales and 2- to 4-fold lower than those of ceftazidime/avibactam (MIC_50/90 0.5/2 mg/L). For isolates producing a plasmid-encoded AmpC, VNRX-5236 decreased ceftibuten MIC (MIC_50/90 0.12/1 mg/L) by at least 512-fold compared with ceftibuten (MIC_50/90 128/>256 mg/L). Ceftibuten/VNRX-5236 (MIC_50/90 0.06/0.12 mg/L) and meropenem (MIC_50/90 ≤0.03/0.06 mg/L; 100% susceptible) showed comparable activities against ESBL isolates and these agents had MIC₉₀ values 4- to 8-fold lower than that of ceftazidime/avibactam (MIC_50/90 0.25/0.5 mg/L; 100% susceptible). Ceftibuten/VNRX-5236 (MIC_50/90 0.12/0.5 mg/L) had the lowest MIC for KPC producers, followed by ceftazidime/avibactam (MIC_50/90 2/4 mg/L; 98.0% susceptible). The same MIC₉₀ values were obtained for ceftibuten/VNRX-5236 (MIC_50/90 0.25/1 mg/L) and ceftazidime/avibactam (MIC_50/90 1/1 mg/L; 100.0% susceptible) for isolates carrying bla_OXA-48-like. VNRX-5236 decreased the ceftibuten MIC at least 16-fold for three isolates carrying bla_OXA-48-like and bla_KPC.

Conclusions

VNRX-5236 rescued the in vitro activity of ceftibuten against Enterobacterales carrying common serine β-lactamases, including ESBL, AmpC and the KPC and OXA-48-like carbapenemases. Ceftibuten/VNRX-5236 may have potential as an oral treatment for infections caused by resistant Enterobacterales, while sparing carbapenems.

Efficacy Profiles of Antimicrobials Evaluated against Staphylococcus Species Isolated from Canine Clinical Specimens

Simple Summary

Clinical cases associated with staphylococci infections are common among dogs and cats. There is evidence to suggest that staphylococci infections are increasingly becoming unresponsive to commonly used antimicrobials. This negatively impacts the ability of these infections to be treated successfully. Although resistance among these organisms has been linked to several factors, including sharing the same mechanism of action or belonging to the same group, there is evidence to suggest that cross resistance can occur between unrelated antimicrobials. The findings of this study not only confirm that antimicrobials that belong to the same group share the same mechanism of resistance and similar antimicrobial efficacy against staphylococcal infections, but also show that cross resistance occurs between unrelated antimicrobials. This should be taken into consideration when selecting antimicrobials for inclusion in the susceptibility testing panel as well as for the treatment of staphylococci infections.

Abstract

Cross-resistance occurs between antimicrobials with either similar mechanisms of action and/or similar chemical structures, or even between unrelated antimicrobials. This study employed a multivariate approach to investigate the associations between the efficacy profile of antimicrobials and the clustering of eleven different antimicrobial agents based on their efficacy profile. Records of the susceptibility of 382 confirmed Staphylococcus species isolates against 15 antimicrobials based on the disc diffusion method were included in this study. Tetrachoric correlation coefficients were computed to assess the correlations of antimicrobial efficacy profiles against Staphylococcus aureus. Principal components analysis and factor analysis were used to assess the clustering of antimicrobial susceptibility profiles. Strong correlations were observed among aminoglycosides, penicillins, fluroquinolones, and lincosamides. Three main factors were extracted, with Factor 1 dominated by the susceptibility profile of enrofloxacin (factor loading (FL) = 0.859), gentamicin (FL = 0.898), tylosin (FL = 0.801), and ampicillin (FL = −0.813). Factor 2, on the other hand, was dominated by the susceptibility profile of clindamycin (FL = 0.927) and lincomycin-spectinomycin (FL = 0.848) and co-trimazole (FL = −0.693). Lastly, Factor 3 was dominated by the susceptibility profile of amoxicillin-clavulanic acid (FL = 0.848) and cephalothin (FL = 0.824). Antimicrobials belonging to the same category or class of antimicrobial, tended to exhibit similar efficacy profiles, therefore, laboratories must choose only one of the antimicrobials in each group to help reduce the cost of antimicrobial susceptibility tests.

A Comprehensive Computer Aided Vaccine Design Approach to Propose a Multi-Epitopes Subunit Vaccine against Genus Klebsiella Using Pan-Genomics, Reverse Vaccinology, and Biophysical Techniques

Klebsiella is a genus of nosocomial bacterial pathogens and is placed in the most critical list of World Health Organization (WHO) for development of novel therapeutics. The pathogens of the genus are associated with high mortality and morbidity. Owing to their strong resistance profile against different classes of antibiotics and nonavailability of a licensed vaccine, urgent efforts are required to develop a novel vaccine candidate that can tackle all pathogenic species of the Klebsiella genus. The present study aims to design a broad-spectrum vaccine against all species of the Klebsiella genus with objectives to identify the core proteome of pathogen species, prioritize potential core vaccine proteins, analyze immunoinformatics of the vaccine proteins, construct a multi-epitopes vaccine, and provide its biophysical analysis. Herein, we investigated all reference species of the genus to reveal their core proteome. The core proteins were then subjected to multiple reverse vaccinology checks that are mandatory for the prioritization of potential vaccine candidates. Two proteins (TonB-dependent siderophore receptor and siderophore enterobactin receptor FepA) were found to fulfill all vaccine parameters. Both these proteins harbor several potent B-cell-derived T-cell epitopes that are antigenic, nonallergic, nontoxic, virulent, water soluble, IFN-γ producer, and efficient binder of DRB*0101 allele. The selected epitopes were modeled into a multi-epitope peptide comprising linkers and Cholera Toxin B adjuvant. For docking with innate immune and MHC receptors and afterward molecular dynamics simulations and binding free energy analysis, the vaccine structure was modeled for tertiary structure and refined for structural errors. To assess the binding affinity and presentation of the designed vaccine construct, binding mode and interactions analysis were performed using molecular docking and molecular dynamics simulation techniques. These biophysical approaches illustrated the vaccine as a good binder to the immune receptors and revealed robust interactions energies. The vaccine sequence was further translated to nucleotide sequence and cloned into an appropriate vector for expressing it at high rate in Escherichia coli K12 strain. In addition, the vaccine was illustrated to generate a good level of primary, secondary, and tertiary immune responses, proving good immunogenicity of the vaccine. Based on the reported results, the vaccine can be a good candidate to be evaluated for effectiveness in wet laboratory validation studies.

Let-7b-5p in vesicles secreted by human airway cells reduces biofilm formation and increases antibiotic sensitivity of P. aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen that forms antibiotic-resistant biofilms, which facilitate chronic infections in immunocompromised hosts. We have previously shown that P. aeruginosa secretes outer-membrane vesicles that deliver a small RNA to human airway epithelial cells (AECs), in which it suppresses the innate immune response. Here, we demonstrate that interdomain communication through small RNA-containing membrane vesicles is bidirectional and that microRNAs (miRNAs) in extracellular vesicles (EVs) secreted by human AECs regulate protein expression, antibiotic sensitivity, and biofilm formation by P. aeruginosa Specifically, human EVs deliver miRNA let-7b-5p to P. aeruginosa, which systematically decreases the abundance of proteins essential for biofilm formation, including PpkA and ClpV1-3, and increases the ability of beta-lactam antibiotics to reduce biofilm formation by targeting the beta-lactamase AmpC. Let-7b-5p is bioinformatically predicted to target not only PpkA, ClpV1, and AmpC in P. aeruginosa but also the corresponding orthologs in Burkholderia cenocepacia, another notorious opportunistic lung pathogen, suggesting that the ability of let-7b-5p to reduce biofilm formation and increase beta-lactam sensitivity is not limited to P. aeruginosa Here, we provide direct evidence for transfer of miRNAs in EVs secreted by eukaryotic cells to a prokaryote, resulting in subsequent phenotypic alterations in the prokaryote as a result of this interdomain communication. Since let-7-family miRNAs are in clinical trials to reduce inflammation and because chronic P. aeruginosa lung infections are associated with a hyperinflammatory state, treatment with let-7b-5p and a beta-lactam antibiotic in nanoparticles or EVs may benefit patients with antibiotic-resistant P. aeruginosa infections.

A global metagenomic map of urban microbiomes and antimicrobial resistance

We present a global atlas of 4,728 metagenomic samples from mass-transit systems in 60 cities over 3 years, representing the first systematic, worldwide catalog of the urban microbial ecosystem. This atlas provides an annotated, geospatial profile of microbial strains, functional characteristics, antimicrobial resistance (AMR) markers, and genetic elements, including 10,928 viruses, 1,302 bacteria, 2 archaea, and 838,532 CRISPR arrays not found in reference databases. We identified 4,246 known species of urban microorganisms and a consistent set of 31 species found in 97% of samples that were distinct from human commensal organisms. Profiles of AMR genes varied widely in type and density across cities. Cities showed distinct microbial taxonomic signatures that were driven by climate and geographic differences. These results constitute a high-resolution global metagenomic atlas that enables discovery of organisms and genes, highlights potential public health and forensic applications, and provides a culture-independent view of AMR burden in cities.

Evolution of β-lactamases and enzyme promiscuity

β-Lactamases represent one of the most prevalent resistance mechanisms against β-lactam antibiotics. Beyond their clinical importance, they have also become key models in enzymology and evolutionary biochemistry. A global understanding of their evolution and sequence and functional diversity can therefore aid a wide set of different disciplines. Interestingly, β-lactamases have evolved multiple times from distinct evolutionary origins, with ancestries that reach back billions of years. It is therefore no surprise that these enzymes exhibit diverse structural features and enzymatic mechanisms. In this review, we provide a bird's eye view on the evolution of β-lactamases within the two enzyme superfamilies-i.e. the penicillin-binding protein-like and metallo-β-lactamase superfamily-through phylogenetics. We further discuss potential evolutionary origins of each β-lactamase class by highlighting signs of evolutionary connections in protein functions between β-lactamases and other enzymes, especially cases of enzyme promiscuity.

Photodynamic Antimicrobial Chemotherapy: Advancements in Porphyrin-Based Photosensitize Development

The reduction of available drugs with effectiveness against microbes is worsening with the current global crisis of antimicrobial resistance. This calls for innovative strategies for combating antimicrobial resistance. Photodynamic Antimicrobial Chemotherapy (PACT) is a relatively new method that utilizes the combined action of light, oxygen, and a photosensitizer to bring about the destruction of microorganisms. This technique has been found to be effective against a wide spectrum of microorganisms, including bacteria, viruses, and fungi. Of greater interest is their ability to destroy resistant strains of microorganisms and in effect help in combating the emergence of antimicrobial resistance. This manuscript reviews porphyrins and porphyrin-type photosensitizers that have been studied in the recent past with a focus on their structure-activity relationship.

Green synthesized Silver Nanoparticles as Silver Lining in Antimicrobial Resistance: A Review

Unprincipled use of antibiotics has led to the antimicrobial resistance (AMR) against mostly available compounds and now become a major cause of concern for the scientific community. However, in the past decade, green synthesized silver nanoparticles (AgNPs) have received greater attention for the development of newer therapies as antimicrobials by virtue of their unique physico-chemical properties. Unlike traditional antibiotics, AgNPs exert their action by acting on multiple mechanisms which make them potential candidates against AMR. Green synthesis of AgNPs using various medicinal plants has demonstrated broader spectrum of action against several microbes in a number of attempts. The present paper provides an insight into the scientific studies that have elucidated the positive role of plant extracts/phytochemicals during green synthesis of AgNPs and their future perspectives. The studies conducted so far seem promising still, a few factors like, the precise mechanism of action of AgNPs, their synergistic interaction with biomolecules, and industrial scalability need to be explored further till effective drug development using green synthesized AgNPs in healthcare systems against AMR is established.

The effect of EDTA in combination with some antibiotics against clinical isolates of gram negative bacteria in Mansoura, Egypt

Extensive use of antibiotics in clinical practice has been associated with increasing frequency of resistant microorganisms. So new strategy is needed to treat the resistant pathogens. Hence this study was conducted to determine the effect of Ethylenediaminetetraacetic acid (EDTA) in increasing the inhibition effect of some antibiotics on multi-drug resistant (MDR) gram-negative bacteria. For this purpose, 40 E. coli isolates, 40 K. pneumoniae isolates and 50 P. aeruginosa isolates were collected from different University's hospitals in Mansoura, Egypt. Antibacterial susceptibility pattern against 9 different antimicrobials were studied by disc diffusion method. Also the effect of two sub-inhibitory concentrations of EDTA (1 and 2 mM) on the inhibition zones of antibiotic discs against the highly multidrug resistant (MDR) isolates was determined. Checkerboard method was used for testing the activity of gentamicin/EDTA and cefotaxime/EDTA combinations on the highly MDR isolates. Additionally, the effect of EDTA on the expression of efflux pump genes was tested by real time-PCR. Most of the clinical isolates were found to be resistant to the tested antibiotics except imipenem and high prevalence of MDR isolates was recorded. 34 isolates were selected as those showed the highest multi-drug resistance and were tested to specify their MIC for EDTA as EDTA showed strong antibacterial activity with MIC ranging 4-8 mM. The addition of sub-MIC of EDTA (1or 2 mM) to the agar plate resulted in changing the 11 tested E. coli isolates from resistant to sensitive to ceftazidime, gentamicin, rifampin, ampicillin, erythromycin and vancomycin, the tested K. pneumoniae isolates were turned also from resistant to sensitive to gentamicin and ceftazidime, additionally the tested P. aeruginosa isolates became sensitive to gentamicin, ceftazidime and ciprofloxacin. Indifference to additive activity was observed for tested combinations and MIC value of cefotaxime or gentamicin in combination with EDTA was less than antibiotic alone in the most tested isolates. Moreover, significant reduction (P < 0.01) in the expression of all tested efflux pump genes in treated E. coli, K. pneumoniae and P. aeruginosa isolates with EDTA compared to untreated isolates was observed. In conclusion, these results suggest that the combination of antibiotic especially gentamicin with EDTA may be fruitful for management of resistant gram negative infections.

Study of indiscriminate distribution of restrained antimicrobial resistome of different environmental niches

Prophylactic usage and high persistent nature of several antibiotics have put selective pressure on the native microbial population that led to the emergence, propagation, and persistence of antibiotic resistance in nature. The surveillance of antibiotic resistome pattern and identification of points of intervention throughout the different environmental habitats will help to break the flow of antibiotic resistance from environmental bacteria to human pathogens. The present study compares the occurrence, diversity, and abundance of ARGs in industrial sludge, wetland sludge, and sediment sample contaminated with pharmaceutical discharge. Metagenomes were mined for the presence of ARGs against the ResFinder 3.2 database using BLASTn program. Pharmaceutical sample (2.52%) showed high degree of ARG abundance and richness as compared with ETP sludge (2.28%) and wetland sludge samples (1.29%). The modern resistome pattern represented by critically important resistance genes against tetracycline (tetA, tetC, tetW, tetT, and tetS/M) and quinolone (qnrS, qnrVC, and qnrD) was identified in pharmaceutical sediment sample. However, effluent treatment plant (ETP) sludge sample showed abundance of multidrug efflux pumps indicating the presence of primitive resistome profile. In conclusion, the indiscriminate distribution pattern of antibiotic resistance genes in three selected environmental sites suggests enrichment and distribution of environmental niche-driven resistance. The study also suggests effluent discharge site from pharmaceutical industries and ETPs as pivotal points of intervention for the mitigation of antibiotic resistance.

Genotypic and phenotypic situation of antimicrobial drug resistance of Escherichia coli in water and manure between biogas and non-biogas swine farms in central Thailand

Currently, Thai livestock is rapidly expanding, especially the production of ruminants, chicken, and swine. The improper use of antibiotics will probably lead to an antimicrobial resistance problem. It has long been suspected that wastewater released from swine farms is a crucial aspect of the spread of antimicrobial resistance to the environment. Biogas systems are wastewater treatment systems commonly used on swine farms; however, little is known about the roles they play in the occurrence and transmission of resistant bacteria between biogas and non-biogas systems. This study collected pooled water, wastewater, and feces samples from five biogas farms and three non-biogas farms in Central Thailand. The samples were isolated to hemolytic E. coli (HEC) and non-hemolytic E. coli (NHEC) to test the drug resistance by using VITEK® 2 Compact (BioMérieux, USA) and detect resistant genes by using the polymerase chain reaction (PCR) technique to correlate the determined phenotypic and genotypic patterns. The results demonstrated that enumeration levels of E. coli ranged from 20.1 to 70.4 (MPN/100 ml), 10⁵ to 10⁷ (cfu/ml), and 10⁵ to 10⁹ (cfu/g), while they were 0-148.7 (MPN/100 ml), 10⁵ to 10⁷ (cfu/ml) and 10⁵ to 10⁹ (cfu/g) for water, wastewater and manure from biogas and non-biogas swine farms, respectively. The amount of E. coli in the sow feces samples was higher than the samples of nursery piglets on biogas farms at a 0.05 significant level (p < 0.05). The antimicrobial resistance indicated the relevant resistance characteristics of E. coli: the highest antimicrobial resistance was for ampicillin (AMP), followed by amoxicillin (AMX), tetracyclines (TET), chloramphenicol (C), and piperacillin (PIP), respectively. Multidrug resistance (MDR) of E. coli was 15 drugs: AMP-AMX-AMC-PIP-CEX-CEV-CPD-XNL-GM-IMP-SXT-C-TE (11.9%) and AMP-AMX-AMC-PIP-CEX-CEV-CPD-XNL-GM-IMP-SXT-C-ENR-MBR-TE (18.55%), which were the most commonly found in biogas and non-biogas swine farms, respectively. The bla_TEM, tetA, sul2, and sul3 were dominantly resistant genes isolated from the water from both types of farm; while, bla_TEM, aadA1, tetA, dfrA12, sul2, sul3, and cmlA were isolated from feces. The amount of E. coli in the final effluent from biogas swine farms was higher than the non-biogas swine farms; however, it was not significantly different at (p > 0.05). Furthermore, the findings of study found that genotypic characteristic of HEC showed similarity 100%. Thus, it was concluded that the levels of E. coli were accelerated in biogas wastewater treatment systems, and isolated E. coli demonstrated multidrug resistance. Even though E. coli was found in different locations, it showed relevant resistance characteristics. Therefore, regular monitoring of antimicrobial resistance on livestock farms is necessary for efficient management and drug uses on farms.

Natural variants modify Klebsiella pneumoniae carbapenemase (KPC) acyl-enzyme conformational dynamics to extend antibiotic resistance

Class A serine β-lactamases (SBLs) are key antibiotic resistance determinants in Gram-negative bacteria. SBLs neutralize β-lactams via a hydrolytically labile covalent acyl-enzyme intermediate. Klebsiella pneumoniae carbapenemase (KPC) is a widespread SBL that hydrolyzes carbapenems, the most potent β-lactams; known KPC variants differ in turnover of expanded-spectrum oxyimino-cephalosporins (ESOCs), for example, cefotaxime and ceftazidime. Here, we compare ESOC hydrolysis by the parent enzyme KPC-2 and its clinically observed double variant (P104R/V240G) KPC-4. Kinetic analyses show that KPC-2 hydrolyzes cefotaxime more efficiently than the bulkier ceftazidime, with improved ESOC turnover by KPC-4 resulting from enhanced turnover (kcat), rather than altered KM values. High-resolution crystal structures of ESOC acyl-enzyme complexes with deacylation-deficient (E166Q) KPC-2 and KPC-4 mutants show that ceftazidime acylation causes rearrangement of three loops; the Ω, 240, and 270 loops, which border the active site. However, these rearrangements are less pronounced in the KPC-4 than the KPC-2 ceftazidime acyl-enzyme and are not observed in the KPC-2:cefotaxime acyl-enzyme. Molecular dynamics simulations of KPC:ceftazidime acyl-enyzmes reveal that the deacylation general base E166, located on the Ω loop, adopts two distinct conformations in KPC-2, either pointing "in" or "out" of the active site; with only the "in" form compatible with deacylation. The "out" conformation was not sampled in the KPC-4 acyl-enzyme, indicating that efficient ESOC breakdown is dependent upon the ordering and conformation of the KPC Ω loop. The results explain how point mutations expand the activity spectrum of the clinically important KPC SBLs to include ESOCs through their effects on the conformational dynamics of the acyl-enzyme intermediate.

Wound dressing of chitosan-based-crosslinked gelatin/ polyvinyl pyrrolidone embedded silver nanoparticles, for targeting multidrug resistance microbes

Wound dressing composed of chitosan, based crosslinked gelatin/ polyvinyl pyrrolidone, embedded silver nanoparticles were fabricated using solution casting method. The membrane was characterized by FTIR, SEM and TGA. Glutaraldehyde (0.5 %) was used for the crosslinking of membrane components and associated with 7-folds boosted mechanical performance, 28 % more hydrolytic stability, 3-folds thickness reduction and morphological roughness. Silver nanoparticles were characterized by UV-vis, XRD and TEM for an average size of 9.9 nm. The membrane with higher concentration of silver nanoparticles showed maximum antibacterial activity against human pathogenic bacteria; and the measured inhibition zones ranged from 1.5 to 3 cm. The activity of the particles ranged from severe to complete reduction in Penicillin, Erythromycin and Macrolide family's resistance genes expression such as β-Lactamase, mecA and erm. This developed membrane can serve as promising and cost-effective system against severe diabetic and burn wound infections.

Antimicrobial resistance three ways: healthcare crisis, major concepts and the relevance of biofilms

Worldwide, infections are resuming their role as highly effective killing diseases, as current treatments are failing to respond to the growing problem of antimicrobial resistance (AMR). The social and economic burden of AMR seems ever rising, with health- and research-related organizations rushing to collaborate on a worldwide scale to find effective solutions. Resistant bacteria are spreading even in first-world nations, being found not only in healthcare-related settings, but also in food and in the environment. In this minireview, the impact of AMR in healthcare systems and the major bacteria behind it are highlighted. Ecological aspects of AMR evolution and the complexity of its molecular mechanisms are explained. Major concepts, such as intrinsic, acquired and adaptive resistance, as well as tolerance and heteroresistance, are also clarified. More importantly, the problematic of biofilms and their role in AMR, namely their main resistance and tolerance mechanisms, are elucidated. Finally, some of the most promising anti-biofilm strategies being investigated are reviewed. Much is still to be done regarding the study of AMR and the discovery of new anti-biofilm strategies. Gladly, considerable research on this topic is generated every day and increasingly concerted actions are being engaged globally to try and tackle this problem.

Risk Factors for Mortality in Patients with Elizabethkingia Infection and the Clinical Impact of the Antimicrobial Susceptibility Patterns of Elizabethkingia Species

Elizabethkingia species (spp.), which can colonize hospital environments, are emerging nosocomial pathogens presenting high mortality. Due to their intrinsic resistance to a broad range of antibiotics, optimal antibiotic dosage has yet to be determined against infections caused by Elizabethkingia spp. This study aimed to investigate the risk factors for the mortality of infections caused by Elizabethkingia spp. and assess the clinical implications of their antimicrobial susceptibility patterns. Data from 210 patients affected by Elizabethkingia-induced pneumonia and bacteremia between 1 November 2005 and 31 May 2016, were analyzed. Further antimicrobial susceptibility tests for moxifloxacin, rifampin, and vancomycin using Elizabethkingia isolates were performed to compensate for the Elizabethkingia spp. susceptibility panel in patients affected after 2013. The mean age of the patients was 66.5 ± 18 years and the 28-day mortality rate was 25.2% (53/210). In the univariate analysis, history of prior stay in an intensive care unit, central venous catheter use, presented thrombocytopenia, immunocompetent status, a high simplified acute physiology score II (SAPS II score), a high C-reactive protein (CRP)/albumin ratio on the day of isolation and seven days later, and a high minimum inhibitory concentration (MIC) value of rifampin were significantly associated with a higher mortality rate. In the multivariate logistic regression analysis, the MIC values of rifampin (odds ratio (OR): 1.045; 95% confidence interval (CI): 1.006–1.085; p = 0.023), SAPS II score (OR: 1.053; 95% CI: 1.022–1.084; p = 0.001), and initial CRP/albumin ratio (OR: 1.030; 95% CI: 1.009–1.051; p = 0.004) were significantly associated with 28-day mortality. To reduce the mortality associated with Elizabethkingia infections, prediction of the clinical course using initial CRP/albumin ratio and SAPS II and early intervention are essential. Rifampin is a promising candidate as the drug of choice in treating Elizabethkingia infections.

Global priority pathogens: virulence, antimicrobial resistance and prospective treatment options

Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Salmonella spp. are part of a group of pathogens that pose a major threat to human health due to the emergence of multidrug-resistant strains. Moreover, these bacteria have several virulence factors that allow them to successfully colonize their hosts, such as toxins and the ability to produce biofilms, resulting in an urgent need to develop new strategies to fight these pathogens. In this review, we compile the most up-to-date information on the epidemiology, virulence and resistance of these clinically important microorganisms. Additionally, we address new therapeutic alternatives, with a focus on molecules with antivirulence activity, which are considered promising to combat multidrug-resistant bacteria.

Factors that predict recurrent spontaneous bacterial peritonitis in cirrhotic patients

BACKGROUND

The recurrence rate of spontaneous bacterial peritonitis (SBP) is increasing in cirrhotic patients. Antibiotic prophylaxis should be prescribed in all cirrhotic patients after the first episode of SBP. However, antibiotics promote the development of antibiotic-resistant bacteria.

OBJECTIVE

To identify the factors that predict the recurrence of SBP after the first episode in cirrhotic patients to optimise the stratification for secondary antibiotic prophylaxis.

METHODS

This retrospective study included 145 cirrhotic patients who had their first SBP episode during 2011-2015. The 86 patients who survived were divided into either the SBP recurrence or non-recurrence group according to patient SBP outcome during the 2-year follow-up. Demographical, clinical and laboratory parameters were recorded at SBP diagnosis and before hospital discharge. SBP recurrence rate, recurrence-free survival and in-hospital mortality were also analysed.

RESULTS

The recurrence rate of SBP after the first episode was 69.8% (60/86), and the median recurrence-free survival time was 142 days. The in-hospital mortality rate was 40.7% (59/145). The significant predictive factors for recurrence of SBP were serum potassium ≥4 mEq/L (HR: 1.89; P = .028), serum albumin ≤2 g/dL (HR: 2.5; P = .003) at diagnosis of SBP and platelet count before discharge ≤100 000/microliter (HR: 1.93; P = .029).

CONCLUSION

SBP frequently recurs in cirrhotic patients. Serum potassium ≥4 mEq/L, serum albumin ≤2g/dL at SBP diagnosis and platelet count ≤100 000/microliter before discharge were identified as factors that may predict the recurrence of SBP after the first episode.

Virulence and Resistance Determinants of Uropathogenic Escherichia coli Strains Isolated from Pregnant and Non-Pregnant Women from Two States in Mexico

BACKGROUND/PURPOSE

Uropathogenic E. coli (UPEC) is the main cause of urinary tract infection (UTI) and it is known that pregnant women have a higher risk for UTI. UPEC has a variety of virulence and antibiotic resistance factors that facilitate its pathogenic success and it is crucial to know which are the susceptibility patterns, Extended-Spectrum-β-Lactamase (ESBL) production, virulence genes, pathogenicity islands (PAI), phylogenetic groups and serotypes among strains isolated from pregnant and non-pregnant women.

METHODS

One hundred fifty UPEC strains were isolated from pregnant and non-pregnant women from two different Mexican states (Sonora and Puebla). Strains were analyzed using the Kirby-Bauer method for the determination of antibiotic susceptibility and ESBL. Virulence genes, PAIs and phylogenetic groups were determined using a multiplex PCR. Strains were serotyped by an agglutination assay. Blood agar and CAS agar were used for phenotypic assays.

RESULTS

92.7% of UPEC strains showed multidrug-resistant (MDR), 6.7% extremely-resistant (XDR) and 0.6% pandrug-resistant (PDR). The highest resistance was determined to be for β-lactam antibiotics (>72% in both states) and 44.5% of the UPEC strains were ESBL+. The predominant virulence genes found were fimH (100%), iucD (85%) and iha (60%). The strains isolated from pregnant women from Puebla presented a large percentage of genes associated with upper urinary tract infections. PAIs were found in 51% and 68% of the strains from Sonora and Puebla, respectively. All the strains were siderophores producers and 41.5% produced hemolysis. The serotypes found were diverse and belonged to phylogroups A, B2 and C.

CONCLUSION

The UPEC strains from this study are MDR with tendency to XDR or PDR, they can cause upper UTIs and are serotypically and phylogenetically diverse, which supports the need to develop new strategies for UTI treatment in pregnant and non-pregnant Mexican women.

High-quality treated wastewater causes remarkable changes in natural microbial communities and intI1 gene abundance

We carry out a mesocosms experiment to assess the impact of high-quality treated wastewater intended for agricultural reuse (HQWR) on freshwater bacteria seldom exposed to anthropogenic pollution. Effects were assessed by comparing the abundance and composition of bacterial communities as well as their resistance profile under control (source water from an unpolluted lake) and treatment conditions (source water mixed 1:1 with HQWR, with and without 5 μg L^-1 of cefotaxime). We investigated the effect of the different conditions on the abundance of genes encoding resistance to β-lactams and carbapenems (bla_TEM, bla_CTX-M, bla_OXA, and bla_KPC), fluoroquinolones (qnrS), tetracyclines (tetA), sulfonamides (sul2), macrolides (ermB), arsenic and cadmium (arsB and czcA, respectively), and on the gene encoding the Class 1 integron integrase (intI1). Bacterial communities exposed to HQWR showed a significant higher abundance of tetA, arsB, czcA, and intI1 genes, whereas those exposed to Cefotaxime-amended HQWR did not. Genes conferring resistance to carbapenems, β-lactams, fluoroquinolones, and macrolides were below detection limit in all treatments. Besides, the higher availability of nutrients under treatment conditions favored bacterial growth in comparison to those exposed to control conditions. Particularly, Acinetobacter spp. and Pseudomonas spp. were significantly enriched after 22 days of treatment exposure. The presence of cefotaxime (a third generation cephalosporine) in the feeding medium caused an enrichment of bacterial communities in sequences affiliated to Acinetobacter thus suggesting that these resistant forms may possess resistance genes other than those studied here (bla_CTX-M, bla_OXA, and bla_KPC). Although derived from a mesocosm experiment in continuous cultures, our results call attention to the need of refined regulations regarding the use of reclaimed water in agriculture since even high-quality treated wastewater may lead to undesired effects on receiving bacterial communities in terms of composition and dissemination of antibiotic resistance genes.

Comparison of the inoculum size effects of antibiotics on IMP-6 β-lactamase-producing Enterobacteriaceae co-harboring plasmid-mediated quinolone resistance genes

Almost all cases of carbapenemase-producing Enterobacteriaceae infections in Japan are caused by blaIMP-positive Enterobacteriaceae (especially blaIMP-6) and infections caused by other types of carbapenemase-producing Enterobacteriaceae are quite rare. We examined drug resistance genes co-harboring with blaIMP-6 and their inoculum size effects. We screened β-lactamase genes, plasmid-mediated quinolone resistance (PMQR) genes, and aminoglycoside-modifying enzyme genes by PCR and performed sequencing for 14 blaIMP-6-positive Enterobacteriaceae. Further, all PMQR-positive isolates were submitted to conjugation and inoculum effect evaluation. Our data showed that 13 of the 14 isolates harbored CTX-M-2 and one co-harbored CTX-M-2 and CTX-M-1 as extended-spectrum β-lactamases. All isolates carried one or more PMQRs; aac(6')-Ib-cr was the most prevalent (92.8%), and was followed by oqxA (64.3%), qnrS (50%), oqxAB (21.4%), and qnrB (14.3%). However, Klebsiella pneumoniae contains chromosomal OqxAB. Inoculum size effects were significant in all strains for meropenem, 13 strains for imipenem, 7 for levofloxacin, and 3 for amikacin. We observed that 11 of the experimental strains (100%), 8 strains (72.7%), and 1 strain showed inoculum size effects for meropenem, imipenem, and amikacin, respectively. However, four strains harbored qnr genes and two strains harbored qnr genes and QRDR mutations concurrently; no inoculum size effect was seen for levofloxacin. The blaIMP-6-positive Enterobacteriaceae that we studied was found to harbor at least one plasmid-mediated drug resistance gene. The inoculum size effect for carbapenems was thought to be mainly due to IMP-6-type metallo-β-lactamase; however qnrB and qnrS also had a minimal impact on the inoculum size effect for levofloxacin.

Comparative Epidemiology and Resistance Trends of Common Urinary Pathogens in a Tertiary-Care Hospital: A 10-Year Surveillance Study

Background and Objective: Urinary tract infections (UTIs) are common in human medicine, affecting large patient populations worldwide. The principal cause of UTIs is uropathogenic Escherichia coli (UPEC) and Klebsiella, both in community and nosocomial settings. The assessment of local data on prevalence and resistance is essential to evaluate trends over time and to reflect on the national situation, compared to international data, using the methods of analytical epidemiology. Materials and Methods: The aim of this study was to assess resistance trends and epidemiology of UTIs caused by E. coli and Klebsiella species in inpatients and outpatients at a tertiary-care hospital in Hungary, using microbiological data. To evaluate resistance trends, several antibiotics were chosen as indicator drugs, based on local utilization data. Results: E. coli was the most prevalent isolate, representing 56.75 ± 4.86% for outpatients and 42.29 ± 2.94% for inpatients. For E. coli, the ratio of resistant strains for several antibiotics was significantly higher in the inpatient group, while in Klebsiella, similar trends were only observed for gentamicin. Extended-spectrum β-lactamase (ESBL)-producing isolates were detected in 4.33-9.15% and 23.22-34.22% from outpatient, 8.85-38.97% and 10.89-36.06% from inpatient samples for E. coli and Klebsiella, respectively. Conclusions: Resistance developments in common UTI pathogens (especially to fosfomycin, sulfamethoxazole-trimethoprim, fluoroquinolones, and 3rd generation cephalosporins), seriously curb therapeutic options, especially in outpatient settings.

Occurrence of Antibiotics and Antibiotic-Resistant Bacteria in Landfill Sites in Kumasi, Ghana

The incidence of antimicrobial resistance among microbial communities is a major threat to global health care and security. Landfills, which are reservoirs for many pharmaceuticals, provide a conducive habitat for antimicrobial-resistant microbes and resistant gene transfer and are therefore a major contributor to the phenomenon of antimicrobial resistance. Hence, this study determined the levels of three widely used antibiotics, metronidazole, penicillin, and amoxicillin, and the occurrence of antimicrobial resistance amongst microbes in soil and leachate samples from active and abandoned landfill sites in Kumasi, Ghana. Soil samples were collected from one active and four abandoned landfills, while leachate specimen was collected only from the active landfill. Sonication and solid-phase extraction (SPE) were used for sample preparation, followed by analysis via an HPLC-PDA method. Isolation and characterization of bacteria were done using standard bacteriological techniques. Antibiotic susceptibility testing was determined following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Antibiotics were detected at very high concentrations in the specimen collected from both active and abandoned landfill sites. For leachate samples obtained from Dompoase, penicillin was present at the highest concentration (67.42 ± 5.35 μg/mL, p<0.05) followed by metronidazole (18.25 ± 7.92 μg/mL) and amoxicillin (10.96 ± 6.93 μg/mL). In general, the levels of antibiotics in soil samples were similar at both active and abandoned landfill sites. Nonetheless, as with leachates, penicillin levels were much higher (p<0.05) than levels of amoxicillin and metronidazole within any particular site. When screened against some antibiotics, Enterobacteriaceae and some Bacillus and Listeria species isolated from the soil and leachate samples proved to be resistant. The high levels of antibiotics coupled with the presence of resistant microbes at these landfills sites call for immediate measures to halt the disposal of pharmaceuticals in the environment so as to avert any possible public health setback.

Rapid detection and molecular survey of blaVIM, blaIMP and blaNDM genes among clinical isolates of Acinetobacter baumannii using new multiplex real-time PCR and melting curve analysis

Background

Acinetobacter baumannii is a cosmopolitan bacterium that is frequently reported from hospitalized patients, especially those patients who admitted in the intensive care unit. Recently, multiplex real-time PCR has been introduced for rapid detection of the resistance genes in clinical isolates of bacteria. The current study aimed to develop and evaluate multiplex real-time PCR to detect common resistance genes among clinical isolates of A. baumannii.

Results

Multiplex real-time PCR based on melting curve analysis showed different T_m corresponding to the amplified fragment consisted of 83.5 °C, 93.3 °C and 89.3 °C for blaIMP, blaVIM and blaNDM, respectively. Results of multiplex real-time PCR showed that the prevalence of blaIMP, blaVIM and blaNDM among the clinical isolates of A. baumannii were 5/128(3.9%), 9/128(7.03%) and 0/128(0%), respectively. Multiplex real-time PCR was able to simultaneously identify the resistance genes, while showed 100% concordance with the results of conventional PCR.

Conclusions

The current study showed that blaVIM, was the most prevalent MBL gene among the clinical isolates of A. baumannii while no amplification of blaNDM was seen. Multiplex real-time PCR can be sensitive and reliable technique for rapid detection of resistance genes in clinical isolates.

Variations of antibiotic resistance profiles in chickens during administration of amoxicillin, chlortetracycline and florfenicol

AIM

To assess the effect of antibiotics administered in feed on the resistance phenotypes and genotypes of Escherichia coli in the chicken intestine.

METHOD AND RESULTS

Chickens were administered amoxicillin, chlortetracycline and florfenicol in feed and 203 intestinal E. coli were examined for their susceptibility to 11 antimicrobial agents and for the presence of antibiotic resistance genes (ARG) using PCR. DNA was extracted from chicken stool samples in 15, 20, 30 and 40 day old chickens. We found that while antibiotic resistance rates increased with time, the relative gene abundance of tet(W), tet(A), cmlA, cfr and sul1 decreased. In contrast, the relative abundance of gene blaTEM and mcr-1 increased over the experimental period. Pearson correlation analysis indicated that sul1 was correlated with tet(W) (R = 0·630, P < 0·01) and cmlA was correlated with cfr (R = 0·587, P < 0·01). Interestingly, mcr-1 correlated with tet(W) (R = -0·546, P < 0·05).

CONCLUSIONS

Administration of different antibiotic reduced the relative abundance of ARG in chickens but did not halt the expansion of antibiotic resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

Changing the pattern of antibiotic types used to prevent antibiotic resistance in chickens is not a viable method to prevent the spread of ARG.

Temporal trends and predictors of antimicrobial resistance among Staphylococcus spp. isolated from canine specimens submitted to a diagnostic laboratory

Background

Resistance to commonly used antimicrobials is a growing concern in both human and veterinary medicine. Understanding the temporal changes in the burden of the problem and identifying its determinants is important for guiding control efforts. Therefore, the objective of this study was to investigate temporal patterns and predictors of antimicrobial resistance among Staphylococcus spp. isolated from canine specimens submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) between 1993 and 2009.

Methods

Retrospective data of 4,972 Staphylococcus isolates assessed for antimicrobial susceptibility using the disk diffusion method at the UKVDL between 1993 and 2009 were included in the study. Temporal trends were assessed for each antimicrobial using the Cochran-Armitage trend test. Logistic regression models were used to investigate predictors of antimicrobial resistance (AMR) and multidrug resistance (MDR).

Results

A total of 68.2% (3,388/4,972) Staphylococcus isolates were S. intermedius group (SIG), 18.2% (907/4,972) were coagulase-negative staphylococci (CoNS), 7.6% (375/4,972) were S. aureus, 5.8% (290/4,972) were S. hyicus, and S. schleiferi subsp. coagulans comprised 0.2% (12/4,972) of the isolates. The overall percentage of AMR and MDR were 77.2% and 25.6%, respectively. The highest levels of AMR were seen in CoNS (81.3%; 737/907), S. aureus (80.5%; 302/375), and SIG (77.6%; 2,629/3388). The lowest levels of AMR were observed in S. hyicus (57.9%; 168/290) and S. schleiferi subsp. coagulans (33.3%; 4/12). Overall, AMR and MDR showed significant (p<0.001) decreasing temporal trends. Significant temporal trends (both increasing and decreasing) were observed among 12 of the 16 antimicrobials covering 6 of the 9 drug classes assessed. Thus, significant increasing temporal trends in resistance were observed to β-lactams (p<0.001) (oxacillin, amoxicillin-clavulanate, cephalothin, and penicillin (p = 0.024)), aminoglycosides (p<0.001) (gentamicin, and neomycin), bacitracin (p<0.001), and enrofloxacin (p<0.001). In contrast, sulfonamide (p<0.001) (sulfadiazin) and tetracycline (p = 0.010) resistant isolates showed significant decreasing temporal trends in AMR. Staphylococcus spp., geographic region, and specimen source were significant predictors of both AMR and MDR.

Conclusions

Although not unexpected nor alarming, the high levels of AMR to a number of antimicrobial agents and the increasing temporal trends are concerning. Therefore, continued monitoring of AMR among Staphylococcus spp. is warranted. Future studies will need to identify local factors responsible for the observed geographic differences in risk of both AMR and MDR.

New β-lactam - Tetramic acid hybrids show promising antibacterial activities

β-Lactams are the most important class of antibiotics, for which the emergence of resistance threatens their utility. As such, we explored the extent to which the tetramic acid motif, frequently found in naturally occurring antibiotics, can be used to generate novel β-lactam antibiotics with improved antibacterial activity. We synthesized new ampicillin - tetramic acid, cephalosporin - tetramic acid, and cephamycin - tetramic acid analogs and evaluated their activities against problematic Gram-positive and Gram-negative pathogens. Amongst the analogs, a 7-aminocephalosporanic acid analog, 3397, and a 7-amino-3-vinyl cephalosporanic acid, 3436, showed potent activities against S. aureus NRS 70 (MRSA) with MICs of 6.25 μg/mL and 3.13 μg/mL respectively. These new analogs were ≥16-fold more potent than cefaclor and cephalexin. Additionally, a Δ² cephamycin - tetramic acid analog 3474 which contained a basic guanidinium substituent at the 5-position of the tetramic acid core displayed potent activity against several clinical strains of K. pneumoniae and E. coli.