Search Results (176)

Listeria monocytogenes biofilms on surfaces that come into contact with food create ongoing challenges in produce-processing environments, highlighting the necessity for effective surface sanitation. This research examined the effectiveness of chlorine (200 ppm), quaternary ammonium compound (QAC, 400 ppm), and UV-C light (0.85 J/cm²) against L. monocytogenes biofilms developed on stainless steel, polyethylene terephthalate (PET), and silicone rubber materials frequently used in apple packing settings. Biofilms were cultivated using a mixture of LCDC and V7 strains in diluted apple juice and evaluated after 1 and 7 days of growth. The type of surface material and the age of the biofilm had a significant impact on the performance of the sanitizing agents (p < 0.05). Chlorine achieved a reduction of 2.84 ± 0.06 log CFU/coupon on 1-day-old biofilms on stainless steel, although its effectiveness dropped to 1.90 ± 0.07 log CFU/coupon on biofilms aged 7 days. Similar trends were noted for QAC (2.42 ± 0.05 to 1.73 ± 0.06 log CFU/coupon) and UV-C (2.71 ± 0.05 to 1.57 ± 0.08 log CFU/coupon) over time. PET and silicone rubber consistently exhibited lower log reductions than stainless steel for all treatments. The presence of organic matter from apple juice reduced the efficacy of sanitizers on all surfaces. These results emphasize the significant role of surface material, biofilm age, and organic load on sanitation effectiveness, offering practical recommendations for enhancing the control of L. monocytogenes in produce-processing facilities. Full article

Background: Effective cetylpyridinium chloride (CPC)-based mouthwashes critically depend on maintaining maximum levels of bioavailable CPC to deliver optimum antimicrobial benefits. While this is traditionally assessed using cellulose-based methods, from economic and efficiency perspectives, there remains a need to identify other potential methods of assessing bioavailable CPC. Here, we explored whether quaternary ammonium compound (QAC) test strips are sensitive to CPC-based formulations, and if so, whether there might exist a possible correlation with glycolysis outcomes. Methods: Quantitative color parameters were obtained using spectrophotometric assessments of QAC test strips immersed in simple CPC solutions and eight commercial CPC-based mouthwashes available in the USA. Then, using our established glycolysis model, we assessed the glycolytic response of both the simple CPC solutions and commercial CPC-based mouthwashes, and compared these data sets. Results: Significant differences (p < 0.05) among the CPC simple solutions were found. Importantly, spectrophotometric assessments and glycolysis trials produced good correlations. Evaluations of the commercial mouthwashes further underlined this correlation, even though those that comprise zinc salts may impact QAC-based color. Conclusions: Based on these results, we believe the use of QAC test strips provides an attractive option to formulators and brands specializing in the development and/or testing of CPC-based oral care formulations. Full article

Benzalkonium chloride (BC) is widely used as a disinfectant in the food industry; however, increasing reports of Listeria innocua isolates exhibiting tolerance to this compound highlight the need to better understand their adaptive mechanisms. This study aimed to evaluate BC tolerance in 51 L. innocua isolates originating from raw and processed meat products (n = 32) and meat-processing environments in Poland (n = 19). Phenotypic tolerance was assessed using the agar diffusion method on two media: Brain Heart Infusion (BHI) agar and Mueller–Hinton (M-H) agar supplemented with 1.2% sheep blood, across BC concentrations of 0, 5, 10, 15, 20, 25, 30, 35, 40, and 45 µg/mL, allowing the determination of minimum inhibitory concentrations (MICs). Genotypic analysis of tolerance determinants (brcABC, ermC, qacE, qacF, qacG, qacH, and qacJ) was performed by PCR. On BHI agar, MIC values ranged from 15 to 30 µg/mL, with 15 µg/mL most frequently observed, whereas on blood-supplemented M-H agar, MICs were lower (5–20 µg/mL), most commonly 10 µg/mL. Among tolerance-associated genes, qacH was the most prevalent (29% of isolates), followed by brcABC (4%) and ermC (2%), while the remaining genes were absent. These findings suggest that food products may serve as a reservoir for L. innocua isolates harboring tolerance to BC and contribute to a deeper understanding of how this species adapts to quaternary ammonium compounds. Full article

Sewage sludge is increasingly recognized as a major reservoir for pharmaceuticals and emerging contaminants that are only partially removed by conventional wastewater treatment. This study provides the first comprehensive assessment of these contaminants in biosolids generated from ten major wastewater treatment plants (WWTPs) across Jordan. Different pharmaceuticals were quantified in the sludge samples generated. The results revealed concentrations ranging from 10 to over 2000 µg kg⁻¹, with antibiotics typically showing the highest enrichment (e.g., ciprofloxacin up to 2165 µg kg⁻¹, ofloxacin up to 303 µg kg⁻¹). Anti-inflammatory compounds such as diclofenac reached 196 µg kg⁻¹, while the antimicrobial triclosan exceeded 4700 µg kg⁻¹ in some sludge samples. Carbamazepine, a recalcitrant antiepileptic drug, ranged between 50 and 223 µg kg⁻¹, reflecting both widespread use and strong persistence. Elevated levels of quaternary ammonium compounds (QACs) were also detected. The highest levels were generally associated with large urban WWTPs and plants receiving industrial discharges. Environmental risk assessment (ERA) indicated that the risk for soil biota was acceptable for most cases for low application doses (5–10 t/ha) except for WWTP6-MD, WWTP8-S, and WWTP9-IC, where the risk was non-acceptable. Severe limitations in the risk assessment were noted: reliable toxicity endpoints in terrestrial soil organisms such as microbiota, collembola, and earthworms are few, while deriving endpoints via aquatic available data is not always reliable. Overall, the findings demonstrate that Jordanian sewage sludge contains environmentally relevant levels of pharmaceuticals and QACs and that risk assessment is, therefore, pertinent before any stabilization and realistic land application scenarios are chosen. Full article

Background/Objectives: The mammalian microbiota constitutes a reservoir of antimicrobial resistance genes (ARGs), which can be shaped by environmental and anthropogenic factors. Although bat-associated bacteria have been reported to harbor diverse ARGs globally, the ecological and evolutionary determinants driving this diversity remain unclear. Methods: To characterize ARG diversity in wildlife exposed to contrasting levels of human influence, we analyzed homologs of resistance mechanisms from the Comprehensive Antibiotic Resistance Database in shotgun metagenomes of bat guano. Samples were collected from a colony exposed to continuous anthropogenic activity in Spain (Salamanca) and from a wild, non-impacted bat community in China (Guangdong). Metagenomic analyses revealed marked differences in taxonomic and resistome composition between sites. Results: Salamanca samples contained numerous hospital-associated genera (e.g., Mycobacterium, Staphylococcus, Corynebacterium), while Guangdong was dominated by Lactococcus, Aeromonas, and Stenotrophomonas. β-lactamases and MurA transferase homologs were the most abundant ARGs in both datasets, yet Salamanca exhibited higher richness and functional diversity (median Shannon index = 1.5; Simpson = 0.8) than Guangdong (Shannon = 1.1; Simpson = 0.66). Salamanca also showed enrichment of clinically relevant ARGs, including qacG, emrR, bacA, and acrB, conferring resistance to antibiotics critical for human medicine. In contrast, Guangdong exhibited a more restricted resistome dominated by β-lactamase and MurA homologs. Beta diversity analysis confirmed significant compositional differences between resistomes (PERMANOVA, R² = 0.019, F = 1.33, p = 0.001), indicating ecological rather than stochastic structuring. Conclusions: These findings suggest that anthropogenic exposure enhances the diversity and evenness of resistance mechanisms within bat-associated microbiomes, potentially increasing their role as reservoirs of antimicrobial resistance. Full article

Cationic surfactants from the group of quaternary ammonium compounds (QACs) are widely used in disinfectants, cosmetics, and household and industrial products. Their strong antimicrobial activity and chemical stability make them valuable in applications but also highly persistent and toxic when released into aquatic environments. This problem has become increasingly relevant during and after the COVID-19 pandemic, when global use of QAC-based disinfectants increased drastically, resulting in their frequent detection in municipal, hospital, and industrial effluents. The concentrations of QACs reported in wastewater range from trace levels to several mg/L, often reaching inhibitory thresholds for biological treatment processes. Although surfactants are not listed in any current European directive, the revised Directive (EU) 2024/1440 classifies micropollutants as a priority group, imposing stricter environmental quality standards and mandatory monitoring requirements. Within this regulatory framework, QACs are recognized as compounds of emerging concern, and their effective removal from wastewater has become a critical challenge. This review summarizes the current knowledge on conventional treatment technologies (coagulation, adsorption, ion exchange, advanced oxidation, and biological processes) and membrane-based methods (ultrafiltration, nanofiltration, reverse osmosis, forward osmosis, and hybrid systems) for the removal of cationic surfactants from water and wastewater. Mechanisms of separation, performance, and operational limitations are discussed. Full article

Managing bacterial infections and the spread of microbial resistance is one of the most critical and complex tasks of modern healthcare infrastructures. Antiseptics and disinfectants such as biocides play a significant role in controlling microbial resistance by reducing the microbial load on surfaces, skin, and environments, thereby limiting the opportunity for pathogens to proliferate and develop resistance. Herein, we tested the different interactions of quaternary ammonium compound (QAC)-based biocide compositions in pursuit of a better antimicrobial performance. An extensive microbiological analysis was conducted for 12 selected compositions of various combinations of mono-QACs, bis-QACs, and alcohols on 17 strains of bacteria of the ESKAPEE group and fungi, including 11 clinical highly resistant varieties, highlighting synergistic or additive dynamics. The evaluation showed noticeable improvements in activity, with up to 16-fold MBC and 32-fold MBEC reductions for alcohol-based compositions of lead QAC. Moreover, synergistic interactions were detected and confirmed via an optimized checkerboard assay for pyridinium QAC combinations against planktonic Gram-positive S. aureus with a fractional inhibitory concentration index (FICI) and fractional bactericidal concentration index (FBCI) of 0.39–0.5 and Gram-negative A. baumannii biofilms. The studied biocides demonstrated the long-term preservation of antimicrobial efficiency without resistance development during a 40-day period and do not induce QAC-associated cross-resistance for four commercially available antibiotics with similar mechanisms of action. Full article

Disinfectant tolerance in bacteria may be related to exposure to subinhibitory concentrations of disinfectants, which may activate efflux pumps capable of expelling antimicrobial compounds. The aim of this study was to evaluate the impact of disinfection on the presence of efflux pump genes and the resistance profile of Escherichia coli from commercial laying farms employing different disinfection protocols. The emrE, qacE, qacEΔ1, qacH, sugE(c), ydgE, ydgF, and class 1 integron (intl1) genes were investigated using PCR. Susceptibility to 17 antibiotics was assessed, including β-lactams, fluoroquinolones, aminoglycosides, and tetracyclines. Disinfectant exposure was significantly associated with higher frequencies of qacE and qacH, and a reduced frequency of ydgF. Moreover, resistance to ampicillin, trimethoprim–sulfamethoxazole, and doxycycline was significantly more frequent in E. coli isolated from chickens exposed to disinfectants. These findings indicate that disinfectant use can select for E. coli carrying efflux pump genes and resistance genes, favoring the survival and dissemination of tolerant and resistant strains in poultry production. Continuous monitoring and the development of disinfection strategies that minimize selective pressures are crucial for limiting the spread of antimicrobial resistance at the animal–human–environment interface. Full article

The global rise of antimicrobial resistance (AMR), exacerbated by the COVID-19 pandemic, has led to a surge in infections caused by multidrug-resistant (MDR) bacteria. A key driver of this phenomenon is co-selection, where exposure to one antimicrobial promotes resistance to others via horizontal gene transfer (HGT) mediated by mobile genetic elements (MGEs). Carbapenem-resistant Enterobacteriaceae, known for their genomic plasticity, are particularly worrisome; yet genomic data from Latin America—especially Ecuador—remain scarce. This study investigated four carbapenem-resistant clinical isolates (two Klebsiella pneumoniae ST1440 and two Serratia marcescens) from tracheal aspirates of three ICU patients during a COVID-19 outbreak at Hospital IESS Quito Sur, Ecuador. Phenotypic profiling and whole-genome sequencing were performed, followed by bioinformatic reconstruction of plasmid content. Nineteen plasmids were identified, carrying 70 resistance-related genes, including antimicrobial resistance genes (ARGs), metal resistance genes (MRGs), integrons, transposons, and insertion sequences. Hierarchical clustering revealed six distinct gene clusters, with several co-localizing ARGs and genes for resistance to disinfectants and heavy metals—suggesting strong co-selective pressure. Conjugative plasmids harboring high-risk elements such as blaKPC-2, qacE, and Tn4401 were found in multiple isolates, indicating potential interspecies dissemination. These findings emphasize the importance of plasmid-mediated resistance during the pandemic and highlight the urgent need to enhance genomic surveillance and infection control, particularly in resource-limited healthcare settings. Full article

Typhoid fever, caused by Salmonella enterica subsp. enterica serovar Typhi (S. typhi), remains a major public health concern, particularly in low-resource settings with poor sanitation. The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains have significantly complicated treatment, especially in vulnerable pediatric populations. This study aimed to characterize the genetic profiles of drug resistance in MDR and XDR S. typhi isolates from pediatric patients. Methods: A cross-sectional study was conducted on 800 blood samples from pediatric typhoid patients. S. typhi isolates were identified using the BacT/ALERT 3D system, followed by culture on MacConkey and blood agar. Antimicrobial susceptibility was assessed using the disk diffusion method according to CLSI 2022 guidelines. Whole-genome sequencing (WGS) was performed on 29 isolates using Illumina MiSeq technology, and resistance genes and mutations were analyzed. Results: Antimicrobial susceptibility testing revealed that 68 (48.57%) of S. typhi isolates were XDR and 61 (43.57%) were MDR, exhibiting widespread resistance to ciprofloxacin, ampicillin, chloramphenicol, ceftriaxone, and co-trimoxazole. WGS identified key resistance genes across all 29 isolates, including bla_CTX-M-15, bla_TEM-1B, qnrS1, aac(6′)-Iaa, catA1, dfraA7, sul1, qacEΔ1, and the gyrA-S83F mutation. Notably, gyrA-S83F and qnrS1 were detected in all isolates and strongly correlated with ciprofloxacin resistance. Virulence genes were consistently present in all isolates, indicating a high pathogenic potential. The IncY plasmid, found in four (14%) isolates, was linked to resistance against third-generation cephalosporins, including ceftriaxone. Conclusion: This study underscores the alarming prevalence of MDR and XDR S. typhi isolates among pediatric patients, driven by resistance genes such as bla_CTX-M-15, bla_TEM-1B, and gyrA-S83F. These findings highlight the urgent need for targeted therapeutic strategies and robust surveillance systems to combat the growing threat of drug-resistant typhoid fever. Full article

The genus Corynebacterium is commonly isolated from camel uteri, yet it is rarely identified to the species level. During our routine clinical examination of she-camels brought to the hospital with history of reproductive and systemic health issues, four isolates from the uterus and one isolate from blood could not be assigned to any valid Corynebacterium species. Therefore, we aim to identify these isolates, determine any potential virulence factors, and describe how gene turnover contributed to the evolution of these species. Genome-based and phenotypic identification, along with resistome, mobilome, virulome and phylogenomics analysis, was used to characterize the isolates. The isolates were Gram stain-positive, catalase-positive, and rod-shaped. The isolates were assigned to the genus Corynebacterium based on 16S rRNA gene sequence similarity and phylogenetic analysis. The isolates 3274 and ayman were classified as two new Corynebacterium species based on the average nucleotide identity (ANI) values of 78.46% and 68.88% and digital DNA–DNA hybridization (dDDH) values of 20.9% and 22.4%. The isolates 2581A, 2583C, and 4168A constitute a single Corynebacterium species based on their pairwise ANI value of 99% and dDDH value of more than 90%. In addition, isolates 2581A, 2583C, and 4168A showed ANI values of 75.99%, 75.86%, and 76.04% and dDDH values of 23.1%, 23%, and 22.5% with closely related species, and were designated as single new Corynebacterium species. Genes for mycolic acid and menaquinone biosynthesis were detected in all isolates. The isolates were susceptible to ceftiofur, linezolid, penicillin, erythromycin, and tetracycline. All isolates harbored the antiseptic resistance gene qacA. Moreover, virulence factors involved in cell adhesion and iron acquisition were detected. The evolution of these species is dominated by gene gain rather than gene loss. The majority of these genes are acquired through horizontal gene transfer, mediated by prophages and genomic islands. In summary, we characterized three new Corynebacterium species, expanding the number of new Corynebacterium species from animals. Moreover, we described the mechanism underlying the genome evolution of these new species. The clinical findings and detection of virulence genes highlight the significance of these isolates as possible pathogens, contributing to the development of endometritis in camels. Full article

Due to the growing emergence of bacterial and fungal resistance, there is an urgent need for novel antimicrobial compounds. Cationic surfactants are effective antimicrobial agents; however, traditional quaternary ammonium compounds (QACs) are increasingly scrutinized due to their cytotoxicity, poor biodegradability, and harmful effects on aquatic ecosystems. While the antimicrobial efficacy of many new biocides, including QACs, has been extensively studied, comprehensive experimental strategies that simultaneously assess antimicrobial activity, mammalian cell toxicity, and ecotoxicity remain limited. Recent studies have reported that amino-acid-based surfactants containing arginine-phenylalanine and arginine-tryptophan exhibit excellent antibacterial activity and are biodegradable. This work extends their biological characterization to evaluate their potential applications. Specifically, we examined how variations in the head group architecture and hydrophobic moiety influence antifungal and antibiofilm activity. We also assessed how these structural parameters impact cytotoxicity and ecotoxicity. These compounds demonstrated strong activity against a wide range of Candida strains. Their hydrophobic character primarily influenced both antifungal efficacy and cytotoxicity. Importantly, these surfactants exhibited potent antimicrobial and antibiofilm effects at non-cytotoxic concentrations. Notably, their aquatic toxicity was significantly lower than that of conventional QACs. Full article

The emergence of extensively drug-resistant (XDR) foodborne pathogens poses grave threats to food safety. This study characterizes the genome of an XDR Salmonella Kentucky isolate (Sal23C1) co-harboring cfr, mcr-1 and tet(A) from Shanghai chicken meat in 2022, which was the only isolate co-harboring these three key resistance genes among 502 screened Salmonella isolates. Genomic analysis revealed that the multidrug resistance gene cfr, which confers resistance to phenicols, lincosamides, oxazolidinones, pleuromutilins and streptogramin A, was identified within a Tn3-IS6-cfr-IS6 structure on the transferable plasmid p3Sal23C1 (32,387 bp), showing high similarity to the Citrobacter braakii plasmid pCE32-2 (99% coverage, 99.98% identity). Concurrently, the mcr-1 gene resided in a pap2-mcr-1 structure on the transferable IncI2 plasmid p2Sal23C1 (63,103 bp). Notably, both genes could be co-transferred to recipient bacteria via conjugative plasmids at frequencies of (1.15 ± 0.98) × 10⁻⁶. Furthermore, a novel ~79 kb multidrug resistance region (MRR) chromosomally inserted at the bcfH locus was identified, carrying fosA3, mph(A), rmtB, qnrS1 and bla_CTX-M-55. Additionally, a novel Salmonella Genomic Island 1 variant (SGI1-KI) harbored aadA7, qacEΔ1, sul1 and the tet(A) variant. The acquisition of these antibiotic resistance genes in this isolate enhanced bacterial resistance to 21 antimicrobials, including resistance to the critical last-resort antibiotics tigecycline and colistin, which left virtually no treatment options for potential infections. Taken together, this is the first comprehensive genomic report of an XDR poultry-derived Salmonella Kentucky isolate co-harboring cfr, mcr-1 and the tet(A) variant. The mobility of these resistance genes, facilitated by IS6 elements and conjugative plasmids, underscores significant public health risks associated with such isolates in the food chain. Full article

Mobile genetic elements such as integrons are key drivers of microbial evolution, enabling rapid adaptation to environmental pressures through the acquisition and rearrangement of gene cassettes. In this study, we explored the structural diversity and synteny of class 1 integrons (intI1) across a set of agroecosystem-related environments, including digestate, compost, and rhizosphere soils from wheat crops (Triticum durum and T. aestivum). Our results reveal distinct gene cassette architectures shaped by the origin of the samples: digestate harbored the most diverse and complex arrays, while compost displayed streamlined structures. Rhizosphere soils exhibited intermediate configurations, reflecting a dynamic balance between environmental exposure and host influence. Genes associated with resistance to antibiotics and heavy metals, such as qacEΔ1 and ebrA, were differentially distributed, suggesting site-specific selective pressures. The observed patterns of cassette organization and diversity underscore the role of integron synteny as a molecular fingerprint of microbial adaptation. These findings position class 1 integrons as promising bioindicators of soil health and functional resilience, supporting a One Health approach to sustainable agriculture and microbial risk monitoring. Full article

Background: The increasing prevalence of antibiotic-resistant bacterial strains highlights the urgent need for new membrane-targeting antimicrobial agents. Bisquaternary ammonium compounds (bisQACs) have attracted attention for their ability to disrupt bacterial membranes more effectively than monoquaternary analogs. Quinuclidine, known for its health-beneficial properties, has previously been explored for monoQAC derivatization, but studies using natural scaffolds to generate bisQACs remain limited. Methods: Here, we synthesized twelve novel quinuclidine-based bisQACs, systematically varying alkyl chain and linker lengths to investigate structure–activity relationships. Results: Several compounds, including 2(QC₁₆)₃, 2(QC₁₆)₄, 2(QC₁₄)₆, and 2(QC₁₆)₆, exhibited strong activity against Staphylococcus aureus (including MRSA), Listeria monocytogenes, and Escherichia coli, with 2(QC₁₆)₆ being the most potent (MICs 5–38 µM). While cytotoxicity was observed on human RPE1 and HEK293 cells, selectivity indices indicated a favorable therapeutic window relative to reference QACs. Conclusions: These compounds also inhibited biofilm formation and induced rapid bacterial killing through a membrane-disruptive mode of action. Molecular docking showed that alkyl chain and linker variations modulate binding to the QacR efflux regulator, revealing a lower potential for efflux-mediated resistance. Overall, quinuclidine-based bisQACs represent promising leads for potent, selectively active next-generation antimicrobials with a reduced likelihood of resistance development. Full article