Ciprofloxacin, amoxicillin, and aminoglycosides stimulate genetic and phenotypic changes in uropathogenic Escherichia coli strains

Stress-Induced Constraint on Expression Noise of Essential Genes in E. coli

Gene expression is an inherently noisy process that is constrained by natural selection. Yet the condition dependence of constraint on expression noise remains unclear. Here, we address this problem by studying constraint on expression noise of E. coli genes in eight diverse growth conditions. In particular, we use variation in expression noise as an analog for constraint, examining its relationships to expression level and to the number of regulatory inputs from transcription factors across and within conditions. We show that variation in expression noise is negatively associated with expression level, implicating constraint to minimize expression noise of highly expressed genes. However, this relationship is condition dependent, with the strongest constraint observed when E. coli are grown in the presence of glycerol or ciprofloxacin, which result in carbon or antibiotic stress, respectively. In contrast, we do not observe evidence of constraint on expression noise of highly regulated genes, suggesting that highly expressed and highly regulated genes represent distinct classes of genes. Indeed, we find that essential genes are often highly expressed but not highly regulated, with elevated expression noise in glycerol and ciprofloxacin conditions. Thus, our findings support the hypothesis that selective constraint on expression noise is condition dependent in E. coli, illustrating how it may play a critical role in ensuring expression stability of essential genes in unstable environments.

Designed De Novo α-Sheet Peptides Destabilize Bacterial Biofilms and Increase the Susceptibility of E. coli and S. aureus to Antibiotics

Biofilm-associated microbes are 10-1000 times less susceptible to antibiotics. An emerging treatment strategy is to target the structural components of biofilm to weaken the extracellular matrix without introducing selective pressure. Biofilm-associated bacteria, including Escherichia coli and Staphylococcus aureus, generate amyloid fibrils to reinforce their extracellular matrix. Previously, de novo synthetic α-sheet peptides designed in silico were shown to inhibit amyloid formation in multiple bacterial species, leading to the destabilization of their biofilms. Here, we investigated the impact of inhibiting amyloid formation on antibiotic susceptibility. We hypothesized that combined administration of antibiotics and α-sheet peptides would destabilize biofilm formation and increase antibiotic susceptibility. Two α-sheet peptides, AP90 and AP401, with the same sequence but inverse chirality at every amino acid were tested: AP90 is L-amino acid dominant while AP401 is D-amino acid dominant. For E. coli, both peptides increased antibiotic susceptibility and decreased the biofilm colony forming units when administered with five different antibiotics, and AP401 caused a greater increase in all cases. For S. aureus, increased biofilm antibiotic susceptibility was also observed for both peptides, but AP90 outperformed AP401. A comparison of the peptide effects demonstrates how chirality influences biofilm targeting of gram-negative E. coli and gram-positive S. aureus. The observed increase in antibiotic susceptibility highlights the role amyloid fibrils play in the reduced susceptibility of bacterial biofilms to specific antibiotics. Thus, the co-administration of α-sheet peptides and existing antibiotics represents a promising strategy for the treatment of biofilm infections.

Correlation between antimicrobial resistance, biofilm formation, and virulence determinants in uropathogenic Escherichia coli from Egyptian hospital

BACKGROUND

Uropathogenic Escherichia coli (UPEC) is the main etiological agent behind community-acquired and hospital-acquired urinary tract infections (UTIs), which are among the most prevalent human infections. The management of UPEC infections is becoming increasingly difficult owing to multi-drug resistance, biofilm formation, and the possession of an extensive virulence arsenal. This study aims to characterize UPEC isolates in Tanta, Egypt, with regard to their antimicrobial resistance, phylogenetic profile, biofilm formation, and virulence, as well as the potential associations among these factors.

METHODS

One hundred UPEC isolates were obtained from UTI patients in Tanta, Egypt. Antimicrobial susceptibility was assessed using the Kirby-Bauer method. Extended-spectrum β-lactamases (ESBLs) production was screened using the double disk synergy test and confirmed with PCR. Biofilm formation was evaluated using the microtiter-plate assay and microscopy-based techniques. The phylogenetic groups of the isolates were determined. The hemolytic activity, motility, siderophore production, and serum resistance of the isolates were also evaluated. The clonal relatedness of the isolates was assessed using ERIC-PCR.

RESULTS

Isolates displayed elevated resistance to cephalosporins (90-43%), sulfamethoxazole-trimethoprim (63%), and ciprofloxacin (53%). Ninety percent of the isolates were multidrug-resistant (MDR)/ extensively drug-resistant (XDR) and 67% produced ESBLs. Notably, there was an inverse correlation between biofilm formation and antimicrobial resistance, and 31%, 29%, 32%, and 8% of the isolates were strong, moderate, weak, and non-biofilm producers, respectively. Beta-hemolysis, motility, siderophore production, and serum resistance were detected in 64%, 84%, 65%, and 11% of the isolates, respectively. Siderophore production was correlated to resistance to multiple antibiotics, while hemolysis was more prevalent in susceptible isolates and associated with stronger biofilms. Phylogroups B2 and D predominated, with lower resistance and stronger biofilms in group B2. ERIC-PCR revealed considerable diversity among the isolates.

CONCLUSION

This research highlights the dissemination of resistance in UPEC in Tanta, Egypt. The evident correlation between biofilm and resistance suggests a resistance cost on bacterial cells; and that isolates with lower resistance may rely on biofilms to enhance their survival. This emphasizes the importance of considering biofilm formation ability during the treatment of UPEC infections to avoid therapeutic failure and/or infection recurrence.

Treatment of Helicobacter Pylori İnfection and the Colonization of the Gastrointestinal System by Resistant Bacteria

BACKGROUND AND AIMS

Helicobacter pylori (H. pylori) infections are widely treated with antibiotic regimens such as "Amoxicillin 1 gr 2 × 1 tablet, Clarithromycin 500 mg 2 × 1 tablet, and Lansoprazole 30 mg 2 × 1 tablet" for 14 days. We conducted a prospective observational study to explore whether this treatment protocol serves as a predisposing factor for the colonization of resistant gastrointestinal microflora, namely vancomycin-resistant enterococci (VRE), extended-spectrum beta-lactamase Enterobacterales (ESBL-E), and carbapenem-resistant Enterobacterales (CRE).

MATERIALS AND METHODS

Pre- and post-treatment stool samples from 75 patients diagnosed with H. pylori, without a prior treatment history, were cultured and evaluated based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria.

RESULTS

Of the 75 evaluated patients, a pronounced surge in ESBL-E positivity was observed. Before initiating antibiotic treatment, 12 patients (16%) had ESBL-E-positive strains in their gastrointestinal tract. Notably, this number surged to 24 patients (32%) after the conclusion of the 14-day treatment regimen. The change was statistically significant, with a P value of less than 0.002, indicating a clear association between treatment for H. pylori and heightened ESBL-E colonization. Notably, VRE and CRE remained undetected in patients throughout the study, suggesting that the treatment regimen may specifically amplify the risk of ESBL-E colonization without affecting VRE and CRE prevalence.

CONCLUSIONS

As the inaugural report from Turkey on this issue, our study suggests that antibiotic regimens for H. pylori eradication contribute to the increased risk of ESBL-positive bacterial colonization in the gastrointestinal tract.

Escherichia coli survival in response to ciprofloxacin antibiotic stress correlates with increased nucleoid length and effective misfolded protein management

The evolution of antibiotic resistance is a fundamental problem in disease management but is rarely quantified on a single-cell level owing to challenges associated with capturing the spatial and temporal variation across a population. To evaluate cell biological phenotypic responses, we tracked the single-cell dynamics of filamentous bacteria through time in response to ciprofloxacin antibiotic stress. We measured the degree of phenotypic variation in nucleoid length and the accumulation of protein damage under ciprofloxacin antibiotic and quantified the impact on bacterial survival. Increased survival was correlated with increased nucleoid length and the variation in this response was inversely correlated with antibiotic concentration. Survival time was also increased through clearance of misfolded proteins, an unexpected mechanism of stress relief deployed by the filamentous bacteria. Our results reveal a diverse range of survival tactics employed by bacteria in response to ciprofloxacin and suggest potential evolutionary routes to resistance.

Emergence of microbial infections in some hospitals of Cairo, Egypt: studying their corresponding antimicrobial resistance profiles

BACKGROUND

Antimicrobial resistance is one of the ten major public health threats facing humanity, especially in developing countries. Identification of the pathogens responsible for different microbial infections and antimicrobial resistance patterns are important to help clinicians to choose the correct empirical drugs and provide optimal patient care.

METHODS

During the period from November 2020 to January 2021, one hundred microbial isolates were collected randomly from different specimens from some hospitals in Cairo, Egypt. Sputum and chest specimens were from COVID-19 patients. Antimicrobial susceptibility testing was performed according to CLSI guidelines.

RESULTS

Most microbial infections were more common in males and in elderly people over 45 years of age. They were caused by Gram-negative, Gram-positive bacteria, and yeast isolates that represented 69%, 15%, and 16%, respectively. Uropathogenic Escherichia coli (35%) were the most prevalent microbial isolates and showed high resistance rates towards penicillin, ampicillin, and cefixime, followed by Klebsiella spp. (13%) and Candida spp. (16%). Of all microbial isolates, Acinetobacter spp., Serratia spp., Hafnia alvei, and Klebsiella ozaenae were extremely multidrug-resistant (MDR) and have resisted all antibiotic classes used, except for glycylcycline, in varying degrees. Acinetobacter spp., Serratia spp., and Candida spp. were secondary microbial infections in COVID-19 patients, while H. alvei was a bloodstream infection isolate and K. ozaenae was recorded in most infections. Moreover, about half of Staphylococcus aureus strains were MRSA isolates and reported low rates of resistance to glycylcycline and linezolid. In comparison, Candida spp. showed high resistance rates between 77 and 100% to azole drugs and terbinafine, while no resistance rate towards nystatin was reported. Indeed, glycylcycline, linezolid, and nystatin were considered the drugs of choice for the treatment of MDR infections.

CONCLUSION

The prevalence of antimicrobial resistance in some Egyptian hospitals was high among Gram-negative, Gram-positive bacteria, and candida spp. The high resistance pattern -especially in secondary microbial infections in COVID-19 patients- to most antibiotics used is a matter of great concern, portends an inevitable catastrophe, and requires continuous monitoring to avoid the evolution of new generations.

Molecular Factors and Mechanisms Driving Multidrug Resistance in Uropathogenic Escherichia coli-An Update

The rapid emergence of multidrug-resistant (MDR) bacteria indisputably constitutes a major global health problem. Pathogenic Escherichia coli are listed among the most critical group of bacteria that require fast development of new antibiotics and innovative treatment strategies. Among harmful extraintestinal Enterobacteriaceae strains, uropathogenic E. coli (UPEC) pose a significant health threat. UPEC are considered the major causative factor of urinary tract infection (UTI), the second-most commonly diagnosed infectious disease in humans worldwide. UTI treatment places a substantial financial burden on healthcare systems. Most importantly, the misuse of antibiotics during treatment has caused selection of strains with the ability to acquire MDR via miscellaneous mechanisms resulting in gaining resistance against many commonly prescribed antibiotics like ampicillin, gentamicin, cotrimoxazole and quinolones. Mobile genetic elements (MGEs) such as transposons, integrons and conjugative plasmids are the major drivers in spreading resistance genes in UPEC. The co-occurrence of various bacterial evasion strategies involving MGEs and the SOS stress response system requires further research and can potentially lead to the discovery of new, much-awaited therapeutic targets. Here, we analyzed and summarized recent discoveries regarding the role, mechanisms, and perspectives of MDR in the pathogenicity of UPEC.

Bacteriospermia and Male Infertility: Role of Oxidative Stress

Male infertility is one of the major challenging and prevalent diseases having diverse etiologies of which bacteriospermia play a significant role. It has been estimated that approximately 15% of all infertility cases are due to infections caused by uropathogens and in most of the cases bacteria are involved in infection and inflammation leading to the development of bacteriospermia. In response to bacterial load, excess infiltration of leukocytes in the urogenital tract occurs and concomitantly generates oxidative stress (OS). Bacteria may induce infertility either by directly interacting with sperm or by generating reactive oxygen species (ROS) and impair sperm parameters such as motility, volume, capacitation, hyperactivation. They may also induce apoptosis leading to sperm death. Acute bacteriospermia is related with another clinical condition called leukocytospermia and both compromise male fertility potential by OS-mediated damage to sperm leading to male infertility. However, bacteriospermia as a clinical condition as well as the mechanism of action remains poorly understood, necessitating further research in order to understand the role of individual bacterial species and their impact in male infertility.

Characterization of Escherichia coli isolated from urinary tract infection and association between virulence expression and antimicrobial susceptibility

BACKGROUND

The capacity of antibiotics to modulate bacterial virulence has raised concerns over the appropriateness of antibiotic therapies, including when dosing strategies fall below sub-therapeutic levels. In this work, we investigated the ability of antibiotics to influence virulence in Escherichia coli isolated from urinary tract infection (UTI).

RESULTS

Out of 120 isolates, 32.5% carried pap, 21.7% carried hlyA, and 17.5% carried cnf. The predominant B2 phylogroup was significantly associated with the quinolone-resistant isolates. A significant association was seen between the presence of hlyA hemolysin and susceptibility to ceftriaxone and ciprofloxacin (P < 0.05). Sub-inhibitory concentrations of both antibiotics reduced the levels of hlyA expression and hemolysis in isolates treated with antibiotics compared to untreated isolates (P < 0.05). Growth rate assay showed that the decrease in hlyA expression was not an effect of decreased growth rate.

CONCLUSION

Our study indicated the inhibitory effect of ciprofloxacin and ceftriaxone on the level of hemolysis, suggesting that the sub-inhibitory concentrations of these antibiotics may affect the outcome of infections. Further studies, including animal models may elucidate the outcome of virulence modulation by these antibiotics in UTI pathogenesis.

Extraintestinal Pathogenic Escherichia coli: Beta-Lactam Antibiotic and Heavy Metal Resistance

Multiple-antibiotic-resistant (MAR) extra-intestinal pathogenic Escherichia coli (ExPEC) represents one of the most frequent causes of human nosocomial and community-acquired infections, whose eradication is of major concern for clinicians. ExPECs may inhabit indefinitely as commensal the gut of humans and other animals; from the intestine, they may move to colonize other tissues, where they are responsible for a number of diseases, including recurrent and uncomplicated UTIs, sepsis and neonatal meningitis. In the pre-antibiotic era, heavy metals were largely used as chemotherapeutics and/or as antimicrobials in human and animal healthcare. As with antibiotics, the global incidence of heavy metal tolerance in commensal, as well as in ExPEC, has increased following the ban in several countries of antibiotics as promoters of animal growth. Furthermore, it is believed that extensive bacterial exposure to heavy metals present in soil and water might have favored the increase in heavy-metal-tolerant microorganisms. The isolation of ExPEC strains with combined resistance to both antibiotics and heavy metals has become quite common and, remarkably, it has been recently shown that heavy metal resistance genes may co-select antibiotic-resistance genes. Despite their clinical relevance, the mechanisms underlining the development and spread of heavy metal tolerance have not been fully elucidated. The aim of this review is to present data regarding the development and spread of resistance to first-line antibiotics, such as beta-lactams, as well as tolerance to heavy metals in ExPEC strains.

Boosting antibiotics performance by new formulations with deep eutectic solvents

The critical scenario of antimicrobial resistance to antibiotics highlights the need for improved therapeutics and/or formulations. Herein, we demonstrate that deep eutectic solvents (DES) formulations are very promising to remarkably improve the solubility, stability and therapeutic efficacy of antibiotics, such as ciprofloxacin. DES aqueous solutions enhance the solubility of ciprofloxacin up to 430-fold while extending the antibiotic stability. The developed formulations can improve, by 2 to 4-fold, the susceptibility of Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria to the antibiotic. They also improve the therapeutic efficacy at concentrations where bacteria present resistance, without promoting tolerance development to ciprofloxacin. Furthermore, the incorporation of DES decreases the toxicity of ciprofloxacin towards immortalized human epidermal keratinocytes (HaCat cells). The results herein reveal the pioneering use of DES in fluoroquinolone-based formulations and their impact on the antibiotic's characteristics and on its therapeutic action.

Recurrent Urinary Tract Infections and Asymptomatic Bacteriuria in Adults

Purpose of review

Our goal was to summarize recent evidence regarding recurrent urinary tract infections and asymptomatic bacteriuria in different adult populations.

Recent findings

Several research groups are focused on the description of resident bacterial flora in the bladder and urinary dysbiosis in the microbiome era. Even the definitions might change in light of these discoveries. However, the role of urinary microbiome and bacterial interference has still to be determined.

Summary

Systematic treatment of asymptomatic bacteriuria is not recommended and even classic indications such as asymptomatic bacteriuria in pregnant women are controversial. In fact, its treatment is associated with a higher probability of symptomatic UTI and a higher prevalence of antibiotic-resistant bacteria. Improving the diagnosis of asymptomatic bacteriuria and optimizing the management of recurrent urinary tract infections, especially through non-antibiotics measures, are needed in order to minimise antimicrobial resistance.

Identification of Multiple Low-Level Resistance Determinants and Coselection of Motility Impairment upon Sub-MIC Ceftriaxone Exposure in Escherichia coli

Resistance to third-generation cephalosporins among Gram-negative bacteria is a rapidly growing public health threat. Among the most commonly used third-generation cephalosporins is ceftriaxone. Bacterial exposure to sublethal or sub-MIC antibiotic concentrations occurs widely, from environmental residues to intermittently at the site of infection. Quality of ceftriaxone is also a concern, especially in low- and middle-income countries, with medicines having inappropriate active pharmaceutical ingredient (API) content or concentration. While focus has been largely on extended-spectrum β-lactamases and high-level resistance, there are limited data on specific chromosomal mutations and other pathways that contribute to ceftriaxone resistance under these conditions. In this work, Escherichia coli cells were exposed to a broad range of sub-MICs of ceftriaxone and mutants were analyzed using whole-genome sequencing. Low-level ceftriaxone resistance emerged after as low as 10% MIC exposure, with the frequency of resistance development increasing with concentration. Genomic analyses of mutants revealed multiple genetic bases. Mutations were enriched in genes associated with porins (envZ, ompF, ompC, and ompR), efflux regulation (marR), and the outer membrane and metabolism (galU and pgm), but none were associated with the ampC β-lactamase. We also observed selection of mgrB mutations. Notably, pleiotropic effects on motility and cell surface were selected for in multiple independent genes, which may have important consequences. Swift low-level resistance development after exposure to low ceftriaxone concentrations may result in reservoirs of bacteria with relevant mutations for survival and increased resistance. Thus, initiatives for broader surveillance of low-level antibiotic resistance and genomic resistance determinants should be pursued when resources are available.

IMPORTANCE Ceftriaxone is a widely consumed antibiotic used to treat bacterial infections. Bacteria, however, are increasingly becoming resistant to ceftriaxone. Most work has focused on known mechanisms associated with high-level ceftriaxone resistance. However, bacteria are extensively exposed to low antibiotic concentrations, and there are limited data on the evolution of ceftriaxone resistance under these conditions. In this work, we observed that bacteria quickly developed low-level resistance due to both novel and previously described mutations in multiple different genes upon exposure to low ceftriaxone concentrations. Additionally, exposure also led to changes in motility and the cell surface, which can impact other processes associated with resistance and infection. Notably, low-level-resistant bacteria would be missed in the clinic, which uses set breakpoints. While they may require increased resources, this work supports continued initiatives for broader surveillance of low-level antibiotic resistance or their resistance determinants, which can serve as predictors of higher risk for clinical resistance.

Virulence Genes Profile and Antimicrobial Susceptibility of Community-Acquired Bacterial Urinary Tract Infections in a Brazilian Hospital

Urinary tract infections (UTI) are one of the most common diseases worldwide and Escherichia coli is the most common causative bacteria. Empirical treatment is challenging due to antimicrobial or multidrug-resistance. The aims of this study were to determine the uropathogens and their antimicrobial susceptibility profile, as well as to identify the phylogroups and virulence genes of E. coli strains, associated with community-acquired UTI in outpatients admitted at a Brazilian Hospital in southeast Brazil. In total, 47 bacterial strains were isolated from 47 patients, 44 women and 2 men (no gender record from one patient). The age of the patients whose urine culture were positive varied from 0 (less than one month) to 104 years. Most of the isolates were E. coli (41/47), followed by Klebsiella pneumoniae (2/47), Klebsiella variicola/Klebsiella aerogenes (1/47), Pseudomonas aeruginosa (1/47), Proteus mirabilis (1/47), and Citrobacter koseri (1/47). Most E. coli strains were classified as phylogroup B2 (15/41 = 36.59%) and B1 (12/41 = 29.27%) and the most common virulence genes among E. coli strains were fimH (31/41 = 75.61%), iutA (21/41 = 51.22%), and tratT (16/41 = 39.02%). Among the E. coli strains, 59% were multidrug-resistance and strains that were ampicillin, sulfamethoxazole/trimethoprim, or tetracycline-resistant exhibited more chance to be multidrug-resistance, with an odds ratio of 100.00 [95% confidence interval (CI) 9.44-1059.26], 22.50 (95% CI 3.95-128.30), and 12.83 (95% CI 2.68-61.45), respectively. Our results showed that E. coli was the main etiological agent identified and demonstrated high frequency of multidrug-resistance and virulence factors in bacterial strains isolated from UTIs.

Gold-Platinum Nanodots with High-Peroxidase-like Activity and Photothermal Conversion Efficiency for Antibacterial Therapy

Combined therapeutic strategies for bacterial infection have attracted worldwide attention owing to their faster and more effective therapy with fewer side effects compared with monotherapy. In this work, gold-platinum nanodots (AuPtNDs) are simply and quickly synthesized by a one-step method. They not only exhibit powerful peroxidase-like activity but also confer a higher affinity for hydrogen peroxide (H2O2), which is 3.4 times that of horseradish peroxidase. Under 808 nm laser irradiation, AuPtNDs also have excellent photothermal conversion efficiency (50.53%) and strong photothermal stability. Excitingly, they can combat bacterial infection through the combination of chemodynamic and photothermal therapy. In vitro antibacterial results show that the combined antibacterial strategy has a broad-spectrum antibacterial property against both Escherichia coli (Gram negative, 97.1%) and Staphylococcus aureus (Gram positive, 99.3%). Animal experiments further show that nanodots can effectively promote the healing of bacterial infection wounds. In addition, owing to good biocompatibility and low toxicity, they are hardly traceable in the main organs of mice, which indicates that they can be well excreted through metabolism. These results reveal the application potential of AuPtNDs as a simple and magic multifunctional nanoparticle in antibacterial therapy and open up new applications for clinical anti-infective therapy in the near future.

Impact of inappropriate empirical antibiotic treatment on clinical outcomes of urinary tract infections caused by Escherichia coli: a retrospective cohort study

OBJECTIVES

We aimed to determine the clinical impact of inappropriate empirical antibiotic treatment (IEAT) compared with appropriate empirical antibiotic treatment (AEAT) in hospitalised patients with urinary tract infections (UTIs) caused by Escherichia coli (E. coli).

METHODS

This retrospective cohort study included adult patients with a primary diagnosis of UTI who were treated with empirical antibiotics at a tertiary hospital in southern China over a 2-year period. Clinical data of patients who received IEAT were compared with those of patients receiving AEAT. We used multivariable logistic regression to identify the predictors for receiving IEAT and the risk factors affecting clinical outcomes.

RESULTS

A total of 213 patients were enrolled (median age, 61 years), of whom 103 (48.4%) received IEAT. IEAT was associated with empirical use of fluoroquinolones, male sex and age-adjusted Charlson comorbidity index (aCCI) score >6. Hospital length of stay (LOS) was longer for patients who received IEAT than for those who received AEAT (13.6 ± 8.6 days vs. 10.8 ± 7.9 days; P = 0.008). IEAT was an independent risk factor for longer LOS along with aCCI score ≥2, lung disease and cardiac disease.

CONCLUSION

Empirical use of fluoroquinolones for UTIs should be avoided, especially in male patients with aCCI score >6. Improved empirical antimicrobial therapy may have a beneficial impact in reducing bacterial resistance and healthcare costs by decreasing the LOS. Therefore, interventions to promote in-depth antibiotic stewardship programmes in China are needed.

Risk Factors for Amoxicillin-Clavulanate Resistance in Community-Onset Urinary Tract Infections Caused by Escherichia coli or Klebsiella pneumoniae: The Role of Prior Exposure to Fluoroquinolones

Background: High rates of amoxicillin-clavulanate (AMC) resistance among Enterobacterales isolated from urinary tract infections (UTIs) were observed in our area. The aim of this study was to identify risk factors associated with AMC resistance in patients with community-onset UTI in emergency departments (EDs). Methods: A retrospective study was performed of all ED patients with positive urine cultures for Escherichia coli or Klebsiella pneumoniae in a Spanish tertiary-care hospital. Results: 330 urine cultures in all were included: 261 (79.1%) for E. coli and 69 (20.90%) for K. pneumonia. Rates of AMC resistance were 14.94% and 34.78%, respectively. UTI was clinically confirmed in 212 (64.24%) cases. Previous antimicrobial exposure was independently associated with AMC resistance development in E. coli and K. pneumoniae urinary isolates (OR = 2.94, 95% CI = 1.55–5.58). Analyses of infected patients revealed that previous exposure to fluoroquinolones (OR = 3.33, 95% CI = 1.10–10.12, p = 0.034) and to AMC (OR = 5.68, 95% CI = 1.97–16.44, p = 0.001) was significantly associated with isolation of AMC-resistant strains. Conclusions: Prior antibiotic exposure, particularly to AMC or fluoroquinolones, was the only independent risk factor associated with development of AMC resistance in E. coli and K. pneumoniae urinary isolates from patients attending the ED.

Transcriptomic Analysis of the Activity and Mechanism of Action of a Ruthenium(II)-Based Antimicrobial That Induces Minimal Evolution of Pathogen Resistance

Increasing concern over rising levels of antibiotic resistance among pathogenic bacteria has prompted significant research into developing efficacious alternatives to antibiotic treatment. Previously, we have reported on the therapeutic activity of a dinuclear ruthenium(II) complex against pathogenic, multi-drug-resistant bacterial pathogens. Herein, we report that the solubility properties of this lead are comparable to those exhibited by orally available therapeutics that in comparison to clinically relevant antibiotics it induces very slow evolution of resistance in the uropathogenic, therapeutically resistant, E. coli strain EC958, and this resistance was lost when exposure to the compound was temporarily removed. With the aim of further investigating the mechanism of action of this compound, the regulation of nine target genes relating to the membrane, DNA damage, and other stress responses provoked by exposure to the compound was also studied. This analysis confirmed that the compound causes a significant transcriptional downregulation of genes involved in membrane transport and the tricarboxylic acid cycle. By contrast, expression of the chaperone protein-coding gene, spy, was significantly increased suggesting a requirement for repair of damaged proteins in the region of the outer membrane. The complex was also found to display activity comparable to that in E. coli in a range of other therapeutically relevant Gram-negative pathogens.

In vitro effects of sub-inhibitory concentrations of amoxicillin on physiological responses and virulence determinants in a commensal strain of Escherichia coli

AIMS

The goal was to study the effects of sub-minimum inhibitory concentrations (sub-MICs) of amoxicillin (AMX) on various physiological responses and virulence determinants in a commensal strain of Escherichia coli.

MATERIALS AND RESULTS

The commensal strain was passaged under various sub-MICs of AMX and its effect on bacterial growth, motility, biofilm formation, expression of outer membrane proteins (OMPs) and cell adhesion was analysed. Bacterial growth was diminished at 1/2 and 1/4 MICs of AMX with significant reduction in growth rate. Using crystal violet (CV) assays and quantification of surface polysaccharides we observed strong biofilm formation, together with reduced swimming motility in E. coli at 1/2 MIC of AMX. Differential OMP expression upon AMX sub-MIC exposure coincided with enhanced cell adhesion to HT-29 cells in vitro. The results demonstrated that sub-MICs of AMX can stimulate unpredictable changes in commensal bacterial strains which can be a potent source for the propagation of antibiotic resistance.

CONCLUSIONS

The study reports that AMX at 1/2 MIC significantly compromised bacterial growth and swimming motility, alongside inducing biofilm formation. This was also accompanied by upregulation of a single OMP which subsequently increased cell adhesion capabilities in E. coli at 1/2 MIC, thereby enhancing its colonization and survival abilities within the gut microsphere.

SIGNIFICANCE AND IMPACT OF THE STUDY

For the first time, the effects of AMX sub-MICs on a commensal E. coli strain were described. The results corroborate on how antibiotics can act as stimulatory molecules and determine the pathogenicity of commensal bacteria in vivo that can disseminate resistance to other intestinal pathogens or microbes.

Revealing antibiotic cross-resistance patterns in hospitalized patients through Bayesian network modelling

OBJECTIVES

Microbial resistance exhibits dependency patterns between different antibiotics, termed cross-resistance and collateral sensitivity. These patterns differ between experimental and clinical settings. It is unclear whether the differences result from biological reasons or from confounding, biasing results found in clinical settings. We set out to elucidate the underlying dependency patterns between resistance to different antibiotics from clinical data, while accounting for patient characteristics and previous antibiotic usage.

METHODS

Additive Bayesian network modelling was employed to simultaneously estimate relationships between variables in a dataset of bacterial cultures derived from hospitalized patients and tested for resistance to multiple antibiotics. Data contained resistance results, patient demographics and previous antibiotic usage, for five bacterial species: Escherichia coli (n = 1054), Klebsiella pneumoniae (n = 664), Pseudomonas aeruginosa (n = 571), CoNS (n = 495) and Proteus mirabilis (n = 415).

RESULTS

All links between resistance to the various antibiotics were positive. Multiple direct links between resistance of antibiotics from different classes were observed across bacterial species. For example, resistance to gentamicin in E. coli was directly linked with resistance to ciprofloxacin (OR = 8.39, 95% credible interval 5.58-13.30) and sulfamethoxazole/trimethoprim (OR = 2.95, 95% credible interval 1.97-4.51). In addition, resistance to various antibiotics was directly linked with previous antibiotic usage.

CONCLUSIONS

Robust relationships among resistance to antibiotics belonging to different classes, as well as resistance being linked to having taken antibiotics of a different class, exist even when taking into account multiple covariate dependencies. These relationships could help inform choices of antibiotic treatment in clinical settings.

Nitrofurantoin Combined With Amikacin: A Promising Alternative Strategy for Combating MDR Uropathogenic Escherichia coli

Urinary tract infections (UTI) are common infections that can be mild to life threatening. However, increased bacterial resistance and poor patient compliance rates have limited the effectiveness of conventional antibiotic therapies. Here, we investigated the relationship between nitrofurantoin and amikacin against 12 clinical MDR uropathogenic Escherichia coli (UPEC) strains both in vitro and in an experimental Galleria mellonella model. In vitro synergistic effects were observed in all 12 test strains by standard checkerboard and time-kill assays. Importantly, amikacin or nitrofurantoin at half of the clinical doses were not effective in the treatment of UPEC infections in the G. mellonella model but the combination therapy significantly increased G. mellonella survival from infections caused by all 12 study UPEC strains. Taken together, these results demonstrated synergy effects between nitrofurantoin and amikacin against MDR UPEC.

Pathogenic Factors Correlate With Antimicrobial Resistance Among Clinical Proteus mirabilis Strains

Proteus mirabilis is the third most common etiological factor of urinary tract infection. It produces urease, which contributes to the formation of a crystalline biofilm, considered to be one of the most important virulence factors of P. mirabilis strains, along with their ability to swarm on a solid surface. The aim of this study was to analyze the pathogenic properties of two selected groups of clinical P. mirabilis isolates, antimicrobial susceptible and multidrug resistant (MDR), collected from hospitals in different regions in Poland. The strains were examined based on virulence gene profiles, urease and hemolysin production, biofilm formation, and swarming properties. Additionally, the strains were characterized based on the Dienes test and antibiotic susceptibility patterns. It turned out that the MDR strains exhibited kinship more often than the susceptible ones. The strains which were able to form a stronger biofilm had broader antimicrobial resistance profiles. It was also found that the strongest swarming motility correlated with susceptibility to most antibiotics. The correlations described in this work encourage further investigation of the mechanisms of pathogenicity of P. mirabilis.

In-vitro Investigation of Antibiotics Efficacy Against Uropathogenic Escherichia coli Biofilms and Antibiotic Induced Biofilm Formation at Sub-Minimum Inhibitory Concentration of Ciprofloxacin

BACKGROUND

Community-acquired urinary tract infections are associated with significant morbidity, and uropathogenic Escherichia coli (UPEC) alone causes 90% of urinary tract infections. This bacterium retains a diverse armament of virulence factors including fimbria, hemolysins, and siderophores production. In a post invasion scenario, formation of intracellular communities mimic biofilm-like characteristics and are linked to recurrent urinary tract infections. We investigated the effects of different frontline antibiotics on the formation, inhibition, and eradication of biofilms of virulent UPEC strains.

MATERIALS AND METHODS

A total of 155 UPEC strains were scrutinized for various virulence factors including gelatinase, cell surface hydrophobicity, hemagglutination, and serum bactericidal activity. Biofilm formation was confirmed by three different methods: Congo red agar, test tube, and tissue culture plate method. Biofilm inhibition and eradication assays were performed according to the standard protocols. Topographical analysis of biofilms was done by scanning electronic microscopy (SEM).

RESULTS

Out of 155 strains, 113 (73%) were strong biofilm formesr, while 37 (24%) produced biofilms at moderate level. Significant differences were observed between MICs of planktonic cells (MIC-p) and MICs of UPEC biofilms (MIC-b). Among tested frontline antibiotics, levofloxacin successfully inhibited biofilms at a concentration of 32 µg/mL, while trimethoprim eradicated biofilms at higher concentrations (512-1024 µg/mL). Ciprofloxacin treatment at sub-MIC level significantly enhanced biofilm formation (P<0.05).

CONCLUSION

The majority of UPEC strains are strong biofilm formers and show higher tolerance towards frontline antibiotics in biofilm form. We observed significant inhibitory effects of levofloxacin (32 µg/mL) on UPEC biofilms, while treatment with sub-minimal concentrations of ciprofloxacin significantly enhanced biofilm formation. Out of all tested antibiotics, trimethoprim (512-1024 µg/mL) eradicated UPEC biofilms.