Antibiotic Resistance Mechanisms Research Articles

Mobile genetic elements profiling, gene flow, and antimicrobial susceptibility profiles, among Pseudomonas aeruginosa isolates, isolated from Al Muthanna hospitals' wound and burn units in Iraq

The prevalence assessment of integrons among multidrug-resistant strains of Pseudomonas aeruginosa receives much-needed attention from this study, as we achieved our desired objective by conducting a thorough analysis on one hundred swabs obtained from burn and clinical cases at the hospitals present in Al Muthanna governorate during November of the year 2021 through to March of the year 2022. By implementing various methodologies encompassing the scrutiny of growth traits and cellular composition as well as executing biochemical assays, a total of 55 isolates were determined to exhibit the existence of P. aeruginosa.When cultured in Hifluoro agar media, Pseudomonas aeruginosa produced diverse hues; particularly noticeable was its blue-green colour. It was discovered through investigation that there were no intI2 and inti3 genes present in those isolated. Findings from this research disclosed that about one-fifth, or precisely twelve out of fifty-five P. aeruginosa strains screened, had an actively expressed Integrase I gene. The association between elevated rates of resistance to multiple antimicrobial agents and the existence of integrons is worth mentioning. Furthermore, the assemblage of isolates that were efficacious in the presence of integrons demonstrated an augmented resistance towards several frequently employed antibiotics like rifampicin and ceftazidime. In conclusion, it can be stated with confidence that a considerable occurrence of integrons can be observed in Pseudomonas aeruginosa strains that display resistance to numerous pharmaceutical agents. Additionally, the discovery of the intI1 gene in a considerable proportion of isolates underscores the effectiveness of integrons in conferring resistance to a variety of antimicrobial agents. These revelations supplement our insight into antibiotic-resistant mechanisms while also underscoring the necessity for viable strategies aimed at halting and preventing bacterial drug resistance.

Multidrug Resistance Profiles and Resistance Mechanisms to β-Lactams and Fluoroquinolones in Bacterial Isolates from Hospital Wastewater in Bangladesh.

Multidrug resistance (MDR) is one of the deadliest public health concerns of the 21st century, rendering many powerful antibiotics ineffective. The current study provides important insights into the prevalence and mechanisms of antibiotic resistance in hospital wastewater isolates. In this study, we determined the MDR profile of 68 bacterial isolates collected from five different hospitals in Dhaka, Bangladesh. Of them, 48 bacterial isolates were identified as Enterobacteriaceae. Additionally, we investigated the prevalence and distribution of five beta-lactam resistance genes, as well as quinolone resistance mechanisms among the isolates. The results of this study showed that 87% of the wastewater isolates were resistant to at least three different antibiotic classes, as revealed using the disc diffusion method. Resistance to β-lactams was the most common, with 88.24% of the isolates being resistant, closely followed by macrolides (80.88% resistant). Polymyxin was found to be the most effective against wastewater isolates, with 29.41% resistant isolates. The most common β-lactam resistance genes found in wastewater isolates were blaTEM (76.09%), blaCTX-M1 (71.74%), and blaNDM (67.39%). Two missense mutations in the quinolone resistance-determining region (QRDR) of gyrA (S83L and D87N) and one in both parC (S80I) and parE (S458A) were identified in all isolates, and one in parE (I529L), which had not previously been identified in Bangladesh. These findings suggest that hospital wastewater acts as an important reservoir of antibiotic-resistant bacteria wherein resistance mechanisms to β-lactams and fluoroquinolones are obvious. Our data also emphasize the need for establishing a nationwide surveillance system for antibiotic resistance monitoring to ensure that hospitals sanitize their wastewater before disposal, and regulation to ensure hospital wastewater is kept away from community settings.

A genome-wide association study of antibiotic resistance in dairy products-associated Enterococcus faecium isolates

Food-associated Enterococcus faecium are commonly used as food starters and probiotics. However, their use is controversial due to the increasing multidrug resistance. This study aimed to investigate the phenotype-genotype association of antibiotic resistance in 50 dairy products-associated Enterococcus faecium isolates. The antibiotic-resistant phenotype of these isolates was determined based on the minimum inhibitory concentration of 15 antibiotics. The isolates were variably resistant to most tested antibiotics (12/15) but were sensitive to vancomycin, ampicillin, and linezolid. They were subjected to comparative genomic analysis along with 11 and 15 fecal isolates from patients and healthy individuals, respectively. The dairy isolates have a significantly smaller genome size and coding sequence number than the fecal isolates from patients (P < 0.05). A Comprehensive Antibiotic Resistance Database search spotted 47 antibiotic resistance genes, but only four were identified in the dairy-associated isolates. A genome-wide association study was performed to uncover hidden antibiotic resistance genes, identifying 122 potential resistance-linked genes associated with three antibiotics, i.e., chloramphenicol, ciprofloxacin, and rifampicin. Ninety-one genes encoded defined biological functions, while the other genes encoded hypothetical proteins. Although their phenotype-specific role remains to be investigated, our results have provided interesting targets for further elucidating the antibiotic resistance mechanism in Enterococcus faecium.

Analysis of the dynamics of &lt;i&gt;Neisseria gonorrhоeaе&lt;/i&gt; resistance to antimicrobial drugs in the Russian Federation for the period 2005–2021

Background. Neisseria gonorrhoeae can rapidly develop resistance to antimicrobial agents due to innate mechanisms for the acquisition of antimicrobial resistance genes. Because of the rapid formation of resistance mechanisms of N. gonorrhoeae to the antimicrobial agents used in gonococcal therapy, the risk of incurable forms of the disease is high. The purpose of the study is to to summarize the results of RU-GASP over a 16-year period and assess the trends of N. gonorrhoeae resistance to antimicrobials used in the regimens of antibiotic therapy of gonococcal infection in Russia.&#x0D; Materials and methods. Study Objective. The study included 5356 isolates of N. gonorrhoeae received from January 2005 to December 2021 in State Scientific Center of Dermatovenerology and Cosmetology, Moscow of the Ministry of Health of Russia under the RU-GASP program from specialized medical organizations of dermatovenerological profile of 37 subjects of the Russian Federation. Primary identification of N. gonorrhoeae was performed using bacterioscopic and bacteriological methods. The cultures identified as N. gonorrhoeae were frozen in a cryogenic medium and transported to SSCDC. Received cultures were verified by biochemical criteria on a VITEK 2 Compact analyzer. For cultures identified as N. gonorrhoeae with less than 99% probability, a time-of-flight ionization mass spectrometer MALDI Microflex (Bruker Daltonics GmbH, Germany) was used for mass spectrometric analysis.&#x0D; Antimicrobial susceptibility testing. Sensitivity testing of N. gonorrhoeae to six antimicrobials penicillin, spectinomycin, ceftriaxone, tetracycline, azithromycin and ciprofloxacin was performed by serial dilution in agar with determination of minimum suppressive concentrations (MSC, mg/L). N. gonorrhoeae sensitivity to antibacterial agents was evaluated according to EUCAST criteria (The European Committee on Antimicrobial Susceptibility Testing, 2022, http://www.eucast.org).&#x0D; Results. The study showed the absence of significant changes in the ratio of sensitive and resistant to the action of antimicrobial drugs strains of N. gonorrhoeae that is a consequence of the effectiveness of the RU-GASP program, which allowed to exclude in time from therapeutic use the drugs for which a high proportion of the identified resistant strains was observed.&#x0D; Conclusion. Analysis of RU-GASP results over a 16-year period confirms the use of third-generation cephalosporins (Ceftriaxone, Cefixime) as the drugs of choice for therapy of gonococcal infection, and the aminocyclic antibiotic spectinomycin as an alternative drug. The continued evolution of the molecular mechanisms of antibiotic resistance of N. gonorrhoeae dictates the need to continue the RU-GASP program.

Antibiotic Resistance: The Threat of Public Health

The discovery of antibiotics is one of the most significant medical achievements of modern medicine as these agents have become a vital component of clinical practice. Overuse and misuse of these medications lead to the emergence of antibiotic resistance, becoming less effective and has led to the emergence of "superbugs". As superbugs become increasingly common, superbug caused infections are very difficult and sometimes impossible to treat. Patients with and multidrug-resistant organisms infection have an increased risk of death compared to patients with infection due to susceptible strain. The financial risks associated with specific multidrug-resistant organisms are also varying greatly. The current review's main objective is to summarise recent research on the mechanism of antibiotic resistance, therapeutic approaches, and potential new antibiotics being developed to combat superbugs.

Resistance to antimicrobial preparations of Enterococcus isolated from milk during infectious mastitis in cows

For successful pharmacotherapy of animals, it is important to identify species of Enterococcus faecalis pathogens isolated from milk in infectious mastitis of cows, analyze the antibiogram and interpret the results, and laboratory control over the mechanisms of antibiotic resistance. This is necessary for veterinarians to rationally select antibacterial drugs and predict their clinical effectiveness. The purpose of the study was to study the resistance to antimicrobial drugs of Enterococcus faecalis bacteria isolated from milk in infectious mastitis of cows. In the period from 2021 to 2022, 100 strains of microorganisms were isolated from the mastitis milk of cows. The obtained strains were identified as gram-negative bacteria in 32% of isolation cases, gram-positive bacteria - 68%, of which 14% were Enterococcus faecalis. When interpreting the antibiogram, most isolates of Enterococcus faecalis are sensitive to tetracycline in 21.4% of isolation cases, ampicillin, amoxicillin in 100%. It was noted resistant to tetracycline in 78.6% of cases of isolation, gentamicin, cephalexin, cefotaxime, erythromycin, clindamycin, lincomycin, tobramycin, ceftriaxone and streptomycin in 100%. Antibiotic resistance correlates with the clinical failure of antimicrobials in veterinary medicine. Multi-resistance of Enterococcus faecalis to various groups of antibacterial agents leads to limited use of antibiotics, which significantly reduces the possibilities of therapy and affects the economic condition of agriculture.

Mechanism of antibiotic resistance development in an activated sludge system under tetracycline pressure.

The mechanism of antibiotic resistance (AR) development in an activated sludge system under tetracycline (TC) pressure was discussed and analyzed. According to the variation of macro-factors, including TC, COD, TN, TP, NH3-N, pH, heavy metals, and reactor settings, the tet genes respond accordingly. Consequently, the enrichment sites of tet genes form an invisible AR selection zone, where AR microorganisms thrive, gather, reproduce, and spread. The efflux pump genes tetA and tetB prefer anaerobic environment, while ribosome protective protein genes tetM, tetO, tetQ, tetT, and tetW were more concentrated in aerobic situations. As a corresponding micro-effect, different types of tet genes selected the corresponding dominant bacteria such as Thauera and Arthrobacter, suggesting the intrinsic relationship between tet genes and potential hosts. In summary, the macro-response and micro-effect of tet genes constitute an interactive mechanism with tet genes as the core, which is the crucial cause for the continuous development of AR. This study provides an executable strategy to control the development of AR in actual wastewater treatment plants from the perspective of macro-factors and micro-effects.

Antibacterial Resistance. The Challenge of Modernity

Antimicrobial resistance is considered by WHO as one of the most important threats to public health in the twenty-first century. According to forecasts, by 2025, many first-line antimicrobials will lose their effectiveness and the «post-antibiotic era» will begin. Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and representatives of the genus Mycobacterium are classified by the American Society of Infectious Diseases as microorganisms that play a predominant role in the development of infections associated with medical care and leading to fatal consequences. The review highlights the mechanisms of antibiotic resistance and many variants of microbial resistance to antibiotics. Knowledge of the molecular mechanisms of the formation of resistance of microorganisms allows us to develop strategic directions for overcoming it. The search for new ways to prevent and overcome the formation of resistance of pathogens to antibiotics is an extremely important task of modern medical science. The effectiveness of hybrid antibiotics associated with chemical compounds with various specific effects is presented. The use of the main active factor of the bacterial virus, endolysin, both in its pure form and as part of homodimers, for example, lysoprotein, which is a complex of endolysin with human immunoglobulins, is considered promising. Phage therapy of the future is a personalized phage therapy that requires the creation of a library or bank of phages.

Involvement of Acquired Tobramycin Resistance in the Shift to the Viable but Non-Culturable State in Pseudomonas aeruginosa.

Persistent and viable but non-culturable (VBNC) Pseudomonas aeruginosa cells are mainly responsible for the recurrence and non-responsiveness to antibiotics of cystic fibrosis (CF) lung infections. The sub-inhibitory antibiotic concentrations found in the CF lung in between successive therapeutic cycles can trigger the entry into the VBNC state, albeit with a strain-specific pattern. Here, we analyzed the VBNC cell induction in the biofilms of two CF P. aeruginosa isolates, exposed to starvation with/without antibiotics, and investigated the putative genetic determinants involved. Total viable bacterial cells were quantified by the validated ecfX-targeting qPCR protocol and the VBNC cells were estimated as the difference between qPCR and cultural counts. The isolates were both subjected to whole genome sequencing, with attention focused on their carriage of aminoglycoside resistance genes and on identifying mutated toxin-antitoxin and quorum sensing systems. The obtained results suggest the variable contribution of different antibiotic resistance mechanisms to VBNC cell abundance, identifying a major contribution from tobramycin efflux, mediated by MexXY efflux pump overexpression. The genome analysis evidenced putative mutation hotspots, which deserve further investigation. Therefore, drug efflux could represent a crucial mechanism through which the VBNC state is entered and a potential target for anti-persistence strategies.

In vitro and in silico evidences about the inhibition of MepA efflux pump by coumarin derivatives

The discovery of antibiotics has significantly transformed the outcomes of bacterial infections in the last decades. However, the development of antibiotic resistance mechanisms has allowed an increasing number of bacterial strains to overcome the action of antibiotics, decreasing their effectiveness against infections they were developed to treat. This study aimed to evaluate the antibacterial activity of synthetic coumarins Staphylococcus aureus in vitro and analyze their interaction with the MepA efflux pump in silico. The Minimum Inhibitory Concentration (MIC) determination showed that none of the test compounds have antibacterial activity. However, all coumarin derivatives decreased the MIC of the standard efflux inhibitor ethidium bromide, indicating antibacterial synergism. On the other hand, the C14 derivative potentiated the antibacterial activity of ciprofloxacin against the resistant strain. In silico analysis showed that C9, C11, and C13 coumarins showed the most favorable interaction with the MepA efflux pump. Nevertheless, due to the present in silico and in vitro investigation limitations, further experimental research is required to confirm the therapeutic potential of these compounds in vivo.

Combined metabolomics and transcriptomics analysis reveals the mechanism of antibiotic resistance of Salmonella enterica serovar Typhimurium after acidic stress

Drug-resistant Salmonella is widely distributed in the meat production chain, endangering food safety and public health. Acidification of meat products during processing can induce acid stress, which may alter antibiotic resistance. Our study investigated the effects of acid stress on the antibiotic resistance and metabolic profile of Salmonella Typhimurium, and explored the underlying mechanisms using metabolomic and transcriptomic analysis. We found that acid-stressed 14028s was more sensitive to small molecule hydrophobic antibiotics (SMHA) while more resistant to meropenem (MERO). Metabolomic analysis revealed that enhanced sensitivity to SMHA was correlated with increased purine metabolism and tricarboxylic acid cycle. Transcriptomic analysis revealed the downregulation of chemotaxis-related genes, which are also associated with SMHA sensitivity. We also found a significant downregulation of the ompF gene, which encodes a major outer membrane protein OmpF of Salmonella. The decreased expression of OmpF porin hindered the influx of MERO, leading to enhanced resistance of the bacteria to the drug. Our findings contribute to greatly improve the understanding of the relationship between Salmonella metabolism, gene expression, and changes in drug resistance after acid stress, while providing a structural framework for exploring the relationship between bacterial stress responses and antibiotic resistance.

Collateral sensitivity: An evolutionary trade-off between antibiotic resistance mechanisms, attractive for dealing with drug-resistance crisis.

The discovery and development of antimicrobial drugs were one of the most significant advances in medicine, but the evolution of microbial resistance limited the efficiency of these drugs. This paper reviews the collateral sensitivity in bacteria and its potential and limitation as a new target for treating infections. Knowledge mechanisms of resistance to antimicrobial agents are useful to trace a practical approach to treat and control of resistant pathogens. The effect of a resistance mechanism to certain antibiotics on the susceptibility or resistance to other drugs is a key point that may be helpful for applying a strategy to control resistance challenges. In an evolutionary trade-off known as collateral sensitivity, the resistance mechanism to a certain drug may be mediated by the hypersensitivity to other drugs. Collateral sensitivity has been described for different drugs in various bacteria, but the molecular mechanisms affecting susceptibility are not well demonstrated. Collateral sensitivity could be studied to detect its potential in the battle against resistance crisis as well as in the treatment of pathogens adapting to antibiotics. Collateral sensitivity-based antimicrobial therapy may have the potential to limit the emergence of antibiotic resistance.

Resistance to antimicrobial drugs of staphylococci isolated from milk in infectious mastitis of cows

Аnalysis of antibiograms and interpretation of the results, laboratory monitoring of the mechanisms of antibiotic resistance of Staphylococcus aureus isolated from milk in infectious mastitis of cows is necessary for successful pharmacotherapy of animals.The aim of the study was to study the antibiotic resistance of Staphylococcus aureus bacteria isolated from milk in infectious mastitis of cows.In the period from 2021 to 2022, 100 strains of microorganisms were isolated from milk in infectious mastitis of cows. The strains were identified as gram-positive Staphylococcus aureus - 16%.When interpreting the antibiogram, it was found that strains of Staphylococcus aureus are sensitive to cephalosporins, aminoglycosides, lincosamides, tetracyclines in 100% of isolation cases, and to benzylpenicillins - 81%. and also resistant.

Bacteremia Caused by a Serotype Ob5 Vibrio cholerae Strain in a Cirrhotic Patient in China.

The increasing incidence of non-O1/non-O139 Vibrio cholerae (NOVC) has been observed worldwide. However, septicemia caused by NOVC remains a rare condition that has received limited attention. Currently, there are no established treatment guidelines for bloodstream infections caused by NOVC, and the understanding of this condition mainly relies on individual case reports. Although NOVC bacteremia can be fatal in a small percentage of cases, knowledge about its microbiological features remains limited. Here, we present a case of V. cholerae septicemia caused by NOVC in a 46-year-old man with chronic viral hepatitis and liver cirrhosis. The isolated strain, named V. cholerae VCH20210731 and classified as a new sequence type (ST), ST1553, was found to be susceptible to most of the antimicrobial agents tested. O-antigen serotyping of V. cholerae VCH20210731 revealed that it belonged to serotype Ob5. Interestingly, the ctxAB genes, which are typically associated with V. cholerae, were absent in VCH20210731. However, the strain possessed 25 other potential virulence genes, such as hlyA, luxS, hap, and rtxA. The resistome of V. cholerae VCH20210731 included several genes, including qnrVC4, crp, almG, and parE. Nevertheless, susceptibility testing demonstrated that the isolate was susceptible to most of the antimicrobial agents tested. Phylogenetic analysis indicated that the closest strain to VCH20210731 was strain 120 from Russia, differing by 630 single-nucleotide polymorphisms (SNPs). Our findings contribute to the understanding of the genomic epidemiological characteristics and antibiotic resistance mechanisms of this invasive bacterial pathogen. IMPORTANCE This study highlights the discovery of a novel ST1553 V. cholerae strain in China, providing valuable insights into the genomic epidemiology and global transmission dynamics of V. cholerae. It is important to note that clinical presentations of NOVC bacteremia can vary significantly, and the isolates demonstrate genetic diversity. Consequently, health care professionals and public health experts should remain vigilant about the potential for infection with this pathogen, particularly considering the elevated prevalence of liver disease in China.

Fructose-enabled killing of antibiotic-resistant Salmonella enteritidis by gentamicin: Insight from reprogramming metabolomics

Salmonella enterica is a food-borne pathogen that poses a severe threat to both poultry production and human health. Antibiotics are critical for the initial treatment of bacterial infections. However, the overuse and misuse of antibiotics results in the rapid evolution of antibiotic-resistant bacteria, and the discovery and development of new antibiotics are declining. Therefore, understanding antibiotic resistance mechanisms and developing novel control measures are essential. In the present study, GC-MS-based metabolomics analysis was performed to determine the metabolic profile of gentamicin sensitive (SE-S) and resistant (SE-R) S. enterica. Fructose was identified as a crucial biomarker. Further analysis demonstrated a global depressed central carbon metabolism and energy metabolism in SE-R. The decrease in the pyruvate cycle reduces the production of NADH and ATP, causing a decrease in membrane potential, which contributes to gentamicin resistance. Exogenous fructose potentiated the effectiveness of gentamicin in killing SE-R by promoting the pyruvate cycle, NADH, ATP and membrane potential, thereby increasing gentamicin intake. Further, fructose plus gentamicin improved the survival rate of chicken infected with gentamicin-resistant Salmonella in vivo. Given that metabolite structures are conserved across species, fructose identified from bacteria could be used as a biomarker for breeding disease-resistant phenotypes in chicken. Therefore, a novel strategy is proposed for fighting against antibiotic-resistant S. enterica, including exploring molecules suppressed by antibiotics and providing a new approach to find pathogen targets for disease resistance in chicken breeding.

Comparative Studies on Clinical Isolates of Hypervirulent and Classical Klebsiella pneumoniae

Hypervirulent Klebsiella pneumonia (hvKP), typically linked with the hypermucoviscous phenotype, has evolved as a clinically significant pathogen responsible for catastrophic disseminated infections including osteomyelitis, pyogenic liver abscesses (PLA), and endophthalmitis in an otherwise younger and healthier population. Methods: Mansoura University Hospitals, Egypt have utilised VITEK® 2 to identify clinical K. pneumoniae isolates. The Kirby Bauer's disc diffusion method was employed to asses sensitivity to antimicrobial. String test for detecting microvasculitis, Serotyping, and Bio-typing are among the phenotypic methods employed. Polymerase chain reaction (PCR) was performed to amplify capsular serotype-specific genes (K1 and K2) as well as virulence-associated genes (rmpA and magA). Results: Over two-years, 100 hypermucoviscous phenotype K. pneumoniae and 100 classical K. pneumoniae strains were isolated and screened by string test. Hypermucoviscosity Serotyping revealed that 76 isolates had K1-type capsules, 19 had K2-type capsules, and 5 were non-K1/K2 isolates. Among the positive hypermucoviscusisolates, the prevalence of rmpA gene was 79 %, and magA gene was 40 %. Although, the prevalence of these two genes in classical Klebsiella pneumoniae (cKP) isolates was very low 11% and 7%, respectively. Aside from that, the occurrence of K capsular genes in hvKP isolates were; K1 gene 66% and K2 gene 63%.However, the occurrence of these genes in cKP isolates were limited. Conclusion: In our geographical area, hypervirulent Klebsiella pneumoniae hvKP isolates were infrequent among K. pneumoniae isolates (El-Mansoura, Egypt). This study summarized and concentrated on the epidemiology, hypervirulence-associated variables, and antibiotic resistance mechanisms of hvKP strains. This was done to let the microbiologist or clinician know that the infecting strain could be hvKP, which is more dangerous than cKP. As a result, detecting these hypervirulent strains, which harbor resistance variants, should be a top goal priority.

Gp05, a Prophage-Encoded Virulence Factor, Contributes to Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections represent a serious public health threat. We recently demonstrated that the presence of a novel prophage ϕSA169 was associated with vancomycin (VAN) treatment failure in experimental MRSA endocarditis. In this study, we assessed the role of a ϕSA169 gene, ϕ80α_gp05 (gp05), in VAN-persistent outcome using gp05 isogenic MRSA strain sets. Of note, Gp05 significantly influences the intersection of MRSA virulence factors, host immune responses, and antibiotic treatment efficacy, including the following: (i) activity of the significant energy-yielding metabolic pathway (e.g., tricarboxylic acid cycle); (ii) carotenoid pigment production; (iii) (p)ppGpp (guanosine tetra- and pentaphosphate) production, which activates the stringent response and subsequent downstream functional factors (e.g., phenol-soluble modulins and polymorphonuclear neutrophil bactericidal activity); and (iv) persistence to VAN treatment in an experimental infective endocarditis model. These data suggest that Gp05 is a significant virulence factor which contributes to the persistent outcomes in MRSA endovascular infection by multiple pathways. IMPORTANCE Persistent endovascular infections are often caused by MRSA strains that are susceptible to anti-MRSA antibiotics in vitro by CLSI breakpoints. Thus, the persistent outcome represents a unique variant of traditional antibiotic resistance mechanisms and a significant therapeutic challenge. Prophage, a critical mobile genetic element carried by most MRSA isolates, provides their bacterial host with metabolic advantages and resistance mechanisms. However, how prophage-encoded virulence factors interact with the host defense system and antibiotics, driving the persistent outcome, is not well known. In the current study, we demonstrated that a novel prophage gene, gp05, significantly impacts tricarboxylic acid cycle activity, stringent response, and pigmentation, as well as vancomycin treatment outcome in an experimental endocarditis model using isogenic gp05 overexpression and chromosomal deletion mutant MRSA strain sets. The findings significantly advance our understanding of the role of Gp05 in persistent MRSA endovascular infection and provide a potential target for development of novel drugs against these life-threatening infections.

Inhibitors for metallo-β-lactamases from the B1 and B3 subgroups provide an avenue to combat a major mechanism of antibiotic resistance

Metallo-β-lactamases (MBLs) are a group of Zn(II)-dependent enzymes that pose a major threat to global health. They are linked to an increasing number of multi-drug resistant bacterial pathogens, but no clinically useful inhibitor is yet available. Since β-lactam antibiotics, which are inactivated by MBLs, constitute ∼65% of all antibiotics used to treat infections, the search for clinically relevant MBL inhibitors is urgent. Here, derivatives of a 2-amino-1-benzyl-4,5-diphenyl-1H-pyrrole-3-carbonitrile (1a) were synthesised and their inhibitory effects assessed against prominent representatives of the MBL family. Several compounds are potent inhibitors of each MBL tested, making them promising candidates for the development of broad-spectrum drug leads. In particular, compound 5f is highly potent across the MBL family, with Ki values in the low µM range. Furthermore, this compound also appears to display synergy in combination with antibiotics such as penicillin G, cefuroxime or meropenem. This molecule thus represents a promising starting point to develop new drugs to inhibit a major mechanism of antibiotic resistance.

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside.

Sepsis is a life-threatening condition and a significant cause of preventable morbidity and mortality globally. Among the leading causative agents of sepsis are bacterial pathogens Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, along with fungal pathogens of the Candida species. Here, we focus on evidence from human studies but also include in vitro and in vivo cellular and molecular evidence, exploring how bacterial and fungal pathogens are associated with bloodstream infection and sepsis. This review presents a narrative update on pathogen epidemiology, virulence factors, host factors of susceptibility, mechanisms of immunomodulation, current therapies, antibiotic resistance, and opportunities for diagnosis, prognosis, and therapeutics, through the perspective of bloodstream infection and sepsis. A list of curated novel host and pathogen factors, diagnostic and prognostic markers, and potential therapeutical targets to tackle sepsis from the research laboratory is presented. Further, we discuss the complex nature of sepsis depending on the sepsis-inducing pathogen and host susceptibility, the more common strains associated with severe pathology and how these aspects may impact in the management of the clinical presentation of sepsis.

Antibacterial Activity of the Essential Oil of Piper tuberculatum Jacq. Fruits against Multidrug-Resistant Strains: Inhibition of Efflux Pumps and β-Lactamase.

Antimicrobial resistance has become a growing public health concern in recent decades, demanding a search for new effective treatments. Therefore, this study aimed to elucidate the phytochemical composition and evaluate the antibacterial activity of the essential oil obtained from the fruits of Piper tuberculatum Jacq. (EOPT) against strains carrying different mechanisms of antibiotic resistance. Phytochemical analysis was performed using gas chromatography-mass spectrometry (GC/MS). The antibacterial activity of EOPT and its ability to inhibit antibiotic resistance was evaluated through the broth microdilution method. The GC-MS analysis identified 99.59% of the constituents, with β-pinene (31.51%), α-pinene (28.38%), and β-cis-ocimene (20.22%) being identified as major constituents. The minimum inhibitory concentration (MIC) of EOPT was determined to assess its antibacterial activity against multidrug-resistant strains of Staphylococcus aureus (IS-58, 1199B, K2068, and K4100). The compound showed a MIC of ≥ 1024 μg/mL, suggesting a lack of intrinsic antibacterial activity. However, when the EOPT was associated with antibiotics and EtBr, a significant decrease in antibiotic resistance was observed, indicating the modulation of efflux pump activity. This evidence was corroborated with the observation of increased fluorescent light emission by the bacterial strains, indicating the involvement of the NorA and MepA efflux pumps. Additionally, the significant potentiation of ampicillin activity against the S. aureus strain K4414 suggests the β-lactamase inhibitory activity of EOPT. These results suggest that the essential oil from P. tuberculatum fruits has antibiotic-enhancing properties, with a mechanism involving the inhibition of efflux pumps and β-lactamase in MDR S. aureus strains. These findings provide new perspectives on the potential use of EOPT against antibiotic resistance and highlight the importance of Piper species as sources of bioactive compounds with promising therapeutic activities against MDR bacteria. Nevertheless, further preclinical (in vivo) studies remain necessary to confirm these in vitro-observed results.