Multidrug-resistant Strains Research Articles

In Silico Design and In Vitro Assessment of Bicyclic Trifluoromethylated Pyrroles as New Antibacterial and Antifungal Agents.

QSAR studies on the number of compounds tested as S. aureus inhibitors were performed using an interactive Online Chemical Database and Modeling Environment (OCHEM) web platform. The predictive ability of the developed consensus QSAR model was q2=0.79±0.02. The consensus prediction for the external evaluation set afforded high predictive power (q2=0.82±0.03). The models were applied to screen a virtual chemical library with anti-S. aureus activity. Six promising new bicyclic trifluoromethylated pyrroles were identified, synthesized and evaluated in vitro against S. aureus, E. coli, and A. baumannii for their antibacterial activity and against C. albicans, C. krusei and C. glabrata for their antifungal activity. The synthesized compounds were characterized by 1H, 19F, and 13C NMR and elemental analysis. The antimicrobial activity assessment indicated that trifluoromethylated pyrroles 9 and 11 demonstrated the greatest antibacterial and antifungal effects against all the tested pathogens, especially against multidrug-resistant strains. The acute toxicity of the compounds to Daphnia magna ranged from 1.21 to 33.39 mg/L (moderately and slightly toxic). Based on the docking results, it can be suggested that the antibacterial and antifungal effects of the compounds can be explained by the inhibition of bacterial wall component synthesis.

Unraveling the genetic basis of antibiotic resistance in Staphylococcus aureus: Focus on mecA and PVL Genes

Background Staphylococcus aureus infections, including Methicillin-Resistant S. aureus (MRSA) and Methicillin-Sensitive S. aureus (MSSA), present significant challenges in healthcare due to rising antimicrobial resistance. This study evaluates the genetic basis of antibiotic resistance in S. aureus, focusing on key resistance-associated genes mecA and PVL. Methods A total of 568 clinical specimens were analyzed for the presence of S. aureus. Demographic data were collected to assess age-dependent prevalence. Antimicrobial susceptibility testing was conducted to evaluate resistance patterns. The prevalence of the mecA and PVL genes was determined using molecular techniques. Results S. aureus was identified in 37.9% of cases, with the highest prevalence (60-79 age group). All S. aureus isolates showed 100% resistance to penicillin. Multidrug-resistant (MDR) strains accounted for 84.19% of isolates, with a significant presence of extensively drug-resistant (XDR) strains. The mecA gene was prevalent in 82.79% of MRSA isolates, indicating its strong association with methicillin resistance. Additionally, 41.86% of all S. aureus isolates were positive for the PVL gene, highlighting its widespread distribution. Conclusions The high prevalence of mecA and PVL genes in S. aureus strains underscores the challenges in managing these infections. These findings emphasize the necessity for judicious antibiotic use and enhanced collaborative efforts to combat antimicrobial resistance. Understanding the genetic basis of resistance can inform more effective diagnostic, therapeutic, and preventive strategies, ultimately improving patient outcomes in S. aureus infections.

Effect of copper nanoparticles green-synthesized using Ocimum basilicum against Pseudomonas aeruginosa in mice lung infection model

Abstract The frequency of lung infection induced by multi-drug resistant strains of Pseudomonas aeruginosa has significantly risen, primarily due to the inadequate effectiveness of powerful chemotherapeutic methods. This study demonstrates that the Ocimum basilicum aqueous extract and copper nanoparticles (CuNPs) exhibited significant antioxidant and anti-infectious properties under in vivo conditions. To analyze the characteristics of the CuNPs synthesized from the reaction between copper nitrate solution and the aqueous O. basilicum extract, various techniques such as energy dispersive X-ray analysis, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, and transmission electron microscopy were employed. The in vivo study encompasses the assessment of P. aeruginosa lethal dose in mice and the disease manifestation analysis, which comprises reduction in body weight, hypothermia, bacteremia, and other parameters, over a 48 h infection period. The infected mice exhibited a notable decrease in body temperature, measuring at 25°C after 48 h, compared to the initial temperature of 39°C. Additionally, a 30% reduction in weight was seen at the conclusion of the study. To assess the effectiveness of CuNPs on lung infection caused by the calculated lethal dose and bacteremia, histopathology analysis was employed. The bacterial load in the CuNPs group was determined to be 0.5 Log10CFU/mL on Day 8, indicating a notable decrease from the initial measurement of 1.5 Log10CFU/mL on Day 1. The histopathological findings revealed a widespread and sporadic buildup of alveolar space inflammatory cells, with infiltrates observed throughout all lung sections in infected mice. Enhanced lung histology was observed in the group of animal treated with reduced exudates noted at 200 µg/kg. CuNPs demonstrated inhibitory effects on the growth of P. aeruginosa at 8 µg/mL, while at 16 µg/mL, they effectively eradicated P. aeruginosa. The research unequivocally demonstrates the efficacy of CuNPs extract in combating lung infections induced by P. aeruginosa at 200 µg/kg. The recent survey aims to further explore the biomedical characteristics of these CuNPs in order to develop a powerful treatment against this dangerous pathogen.

Characteristics of multidrug-resistant hypervirulent Klebsiella pneumoniae strains ST29 and K212 harbouring tmexC2-tmexD2-toprJ2

ObjectivesThis study aimed to characterize a tigecycline-resistant hypervirulent Klebsiella pneumoniae (HvKP) strain, identified as KLZT, which carries the tigecycline resistance gene cluster tmexC2-tmexD2-toprJ2 belonging to ST29 and serotype K212. MethodsAntimicrobial susceptibility and virulence phenotypes were assessed, followed by whole-genome sequencing (WGS) using PacBio II and MiSeq sequencers. Genome annotation was carried out using the RAST server and bioinformatics analysis revealed the genetic characteristics of this strain. ResultsAntimicrobial and virulence phenotype testing indicated that K. pneumoniae strain KLZT could be considered as a multidrug-resistant HvKP. WGS analysis showed that KLZT has a single 5,536,506-bp chromosome containing three plasmids 290,963 bp (pKLZT-1), 199,302 bp (pKLZT-2), and 4820 bp (pKLZT-3) in size, and also includes the ST29 and K212 serotypes. Four (blaSHV-187, oqxA, oqxB, and fosA6) and six resistance genes (tmexC2-tmxeD2-toprJ2, blaOXA-1, aac(6′)-Ib-cr, catB3, arr-3, and blaLEN27) were identified from chromosomal and plasmid pKLZT-1, respectively. Gene-based analysis of the resistance genes of plasmid pKLZT-1 showed that the tigecycline resistance gene cluster-carrying region was flanked by umuC and umuD (umuD-hps-IS5-tmexC2-tmexD2-toprJ2-umuC), as well as other resistance genes and virulence factors (ureB, ureC, and ureG), which were carried by IS5075-Tn3-intI1 -aac(6′)-Ib-cr-blaOXA-1-catB3-arr-3-blaLEN27-Tn3-ISkpn26-ureBCG-IS5075. ConclusionsWGS has revealed that a multidrug-resistant strain, HvKP KLZT, belonging to ST29 with capsular serotype K212, contains a multidrug-resistance plasmid.

Humanized Mouse Models of Bacterial Infections.

Bacterial infections continue to represent a significant healthcare burden worldwide, causing considerable mortality and morbidity every year. The emergence of multidrug-resistant bacterial strains continues to rise, posing serious risks to controlling global disease outbreaks. To develop novel and more effective treatment and vaccination programs, there is a need for clinically relevant small animal models. Since multiple bacterial species have human-specific tropism for numerous virulence factors and toxins, conventional mouse models do not fully represent human disease. Several human disease characteristic phenotypes, such as lung granulomas in the case of Mycobacterium tuberculosis infections, are absent in standard mouse models. Alternatively, certain pathogens, such as Salmonella enterica serovar typhi and Staphylococcus aureus, can be well tolerated in mice and cleared quickly. To address this, multiple groups have developed humanized mouse models and observed enhanced susceptibility to infection and a more faithful recapitulation of human disease. In the last two decades, multiple humanized mouse models have been developed to attempt to recapitulate the human immune system in a small animal model. In this review, we first discuss the history of immunodeficient mice that has enabled the engraftment of human tissue and the engraftment methods currently used in the field. We then highlight how humanized mouse models successfully uncovered critical human immune responses to various bacterial infections, including Salmonella enterica serovar Typhi, Mycobacterium tuberculosis, and Staphylococcus aureus.

Antimicrobial Activity of Essential-Oil-Based Nanostructured Lipid Carriers against Campylobacter Spp. Isolated from Chicken Carcasses.

Campylobacter is a virulent Gram-negative bacterial genus mainly found in the intestines of poultry. The indiscriminate use of traditional antibiotics has led to drug resistance in these pathogens, necessitating the development of more efficient and less toxic therapies. Despite their complex biologically active structures, the clinical applications of essential oils (EOs) remain limited. Therefore, this study aimed to increase the bioavailability, stability, and biocompatibility and decrease the photodegradation and toxicity of EO using nanotechnology. The diffusion disk test revealed the potent anti-Campylobacter activity of cinnamon, lemongrass, clove, geranium, and oregano EOs (>50 mm). These were subsequently used to prepare nanostructured lipid carriers (NLCs). Formulations containing these EOs inhibited Campylobacter spp. growth at low concentrations (0.2 mg/mL). The particle size, polydispersity index, and zeta potential of these systems were monitored, confirming its physicochemical stability for 210 days at 25 °C. FTIR-ATR and DSC analyses confirmed excellent miscibility among the excipients, and FE-SEM elucidated a spherical shape with well-delimited contours of nanoparticles. The best NLCs were tested regarding nanotoxicity in a chicken embryo model. These results indicate that the NLC-based geranium EO is the most promising and safe system for the control and treatment of multidrug-resistant strains of Campylobacter spp.

Dual phage-incorporated electrospun polyvinyl alcohol-eudragit nanofiber matrix for rapid healing of diabetic wound infected by Pseudomonas aeruginosa and Staphylococcus aureus.

Diabetic wound healing remains a healthcare challenge due to co-occurring multidrug-resistant (MDR) bacterial infections and the constraints associated with sustained drug delivery. Here, we integrate two new species of phages designated as PseuPha1 and RuSa1 respectively lysing multiple clinical MDR strains of P. aeruginosa and S. aureus into a novel polyvinyl alcohol-eudragit (PVA-EU†) nanofiber matrix through electrospinning for rapid diabetic wound healing. PVA-EU† evaluated for characteristic changes that occurred due to electrospinning and subjected to elution, stability and antibacterial assays. The biocompatibility and wound healing ability of PVA-EU† were assessed through mouse fibroblast cell line NIH3T3, followed by validation through diabetic mice excision wound co-infected with P. aeruginosa and S. aureus. The electrospinning resulted in the incorporation of ~ 75% active phages at PVA-EU†, which were stable at 25°C for 30days and at 4°C for 90days. PVA-EU† showed sustained release of phages for 18h and confirmed to be detrimental to both mono- and mixed-cultures of target pathogens. The antibacterial activity of PVA-EU† remained unaltered in the presence of high amounts of glucose, whereas alkaline pH promoted the activity. The matrix exerted no cytotoxicity on NIH3T3, but showed significant (p < 0.0001) wound healing in vitro and the process was rapid as validated through a diabetic mice model. The sustained release, quick wound closure, declined abundance of target MDR bacteria in situ and histopathological signs of recovery corroborated the therapeutic efficacy of PVA-EU†. Taken together, our data signify the potential application of PVA-EU† in the rapid treatment of diabetic wounds without the aid of antibiotics.

Hospitalized COVID-19 Patients with Urinary Tract Infection in Iran: Candida Species Distribution and Antifungal Susceptibility Patterns.

Candida species, typically part of the human skin and mucous membrane flora, can cause opportunistic fungal infections, notably urinary tract infections (UTIs), which are on the rise among hospitalized COVID-19 patients. The lack of understanding of UTIs in this population, coupled with the emergence of multidrug-resistant strains, poses significant challenges for effective treatment and further investigations. In this study, urine samples were collected from 70 COVID-19 patients with UTIs in sterile containers for microbiology examination. After microscopic observation, the isolates were identified both by phenotypic and molecular techniques such as multiplex PCR. Antifungal susceptibility testing (AFST) against fluconazole (Flu), itraconazole (Itr), and amphotericin B (AMB) was performed according to CLSI M27/S4 standard methods, with the frequency of isolates including Candida albicans (n = 20, 51.3%), Candida tropicalis (n = 15, 38.4%), Nakaseomyces glabrata (previously Candida glabrata) (n = 2, 5.1%), Pichia kudriavzevii (previously Candida krusei), and Candida parapsilosis (n = 1, 2.5%). All isolates of C. albicans, C. tropicalis, C. glabrata, and C. parapsilosis were sensitive to amphotericin B, while C. kruzei was resistant to AMB. Around 70% of C. albicans isolates were sensitive to Flu; 20% of C. tropicalis were resistant to itraconazole, while 33% were resistant to fluconazole. C. albicans and C. tropicalis were the main causes of candiduria in infected cases and both Flu and AMB showed good results in AFST in these species. Performing drug susceptibility testing for clinical isolates of Candida spp. provided guidance for appropriate management and control, and timely antifungal treatment.

Emergence of genetic diversity and multi-drug resistant Clostridium perfringens from wild birds

BackgroundClostridium perfringens (C. perfringens) is an important zoonotic microorganism that can cause animal and human infections, however information about the prevalence status in wild birds of this pathogenic bacterium is currently limited.ResultIn this study, 57 strains of C. perfringens were isolated from 328 fecal samples of wild birds. All the isolates were identified as type A and 70.18% of the isolates carried the cpb2 gene. Antimicrobial susceptibility testing showed that and 22.80% of the isolates were classified as multidrug-resistant strains. The MLST analysis of the 57 isolates from wild birds was categorized into 55 different sequence types (STs) and clustered into eight clonal complexes (CCs) with an average of 20.1 alleles and the Simpson Diversity index (Ds) of 0.9812, and revealed a high level of genetic diversity within the C. perfringens populations. Interestingly, the isolates from swan goose were clustered in the same CC while isolates from other bird species were more scattered suggesting that a potential difference in genetic diversity among the C. perfringens populations associated with different bird species.ConclusionC. perfringens exhibits a wide range of host adaptations, varying degrees of antimicrobial resistance, and a high degree of genetic diversity in wild birds. Understanding the prevalence, toxin type, antimicrobial resistance, and genetic diversity of C. perfringens in wildlife populations is essential for developing effective strategies for disease control and management.

Extended Drug Resistant Typhoid Fever; A Case Report

Enteric fever is a potentially fatal multisystem illness caused primarily by Salmonella typhi and, to a lesser extent, by Para typhi A, B, and C. Decades of indiscriminate usage of Antibiotics has led to emergence of multiple resistant strains. Multi drug resistant strains against Salmonella typhi has made treatment options limited and costly. According to WHO an estimated 11–20 million people get sick from typhoid all over the world. In the year 2022 an outbreak of Enteric fever emerged in April and spread all over Pakistan. This created a great concern as the causative organism were mostly Multi drug resistant. We recently have documented a case of extended drug resistant (XDR) Enteric Fever with a complicated clinical course, responding only to Carbapenem (Meropenem/Imipenem). The purpose of reporting this case was to highlight the morbidity, cost and therapeutic challenges which are associated with severe XDR S. typhi infection in Pakistan

Extended Drug Resistant Typhoid Fever; A Case Report

Enteric fever is a potentially fatal multisystem illness caused primarily by Salmonella typhi and, to a lesser extent, by Para typhi A, B, and C. Decades of indiscriminate usage of Antibiotics has led to emergence of multiple resistant strains. Multi drug resistant strains against Salmonella typhi has made treatment options limited and costly. According to WHO an estimated 11–20 million people get sick from typhoid all over the world. In the year 2022 an outbreak of Enteric fever emerged in April and spread all over Pakistan. This created a great concern as the causative organism were mostly Multi drug resistant. We recently have documented a case of extended drug resistant (XDR) Enteric Fever with a complicated clinical course, responding only to Carbapenem (Meropenem/Imipenem). The purpose of reporting this case was to highlight the morbidity, cost and therapeutic challenges which are associated with severe XDR S. typhi infection in Pakistan

Extended Drug Resistant Typhoid Fever; A Case Report

Enteric fever is a potentially fatal multisystem illness caused primarily by Salmonella typhi and, to a lesser extent, by Para typhi A, B, and C. Decades of indiscriminate usage of Antibiotics has led to emergence of multiple resistant strains. Multi drug resistant strains against Salmonella typhi has made treatment options limited and costly. According to WHO an estimated 11–20 million people get sick from typhoid all over the world. In the year 2022 an outbreak of Enteric fever emerged in April and spread all over Pakistan. This created a great concern as the causative organism were mostly Multi drug resistant. We recently have documented a case of extended drug resistant (XDR) Enteric Fever with a complicated clinical course, responding only to Carbapenem (Meropenem/Imipenem). The purpose of reporting this case was to highlight the morbidity, cost and therapeutic challenges which are associated with severe XDR S. typhi infection in Pakistan

Assessment of Antibacterial Activity of Various Solvent Extracts of Dictyota Dichotoma Against Multidrug Resistant Bacterial Strain

Assessment of Antibacterial Activity of Various Solvent Extracts of Dictyota Dichotoma Against Multidrug Resistant Bacterial Strain

Atom-economical synthesis, antimicrobial assessment, and molecular dynamics of indole-derived peptidomimetics for improved therapeutic insights

The emergence of multi-drug resistant strains spanning bacteria, fungi, viruses, and parasites poses a severe threat to public health and the economy. Tackling antimicrobial resistance requires swiftly identifying new agents with unique mechanisms. Multicomponent reactions offer a vital method to produce diverse analogs in various heterocyclic compounds, with broad medicinal applications. This study synthesized a range of peptidomimetics using isocyanide-based multicomponent Ugi reactions. These analogs were screened for antimicrobial efficacy against both Gram-negative (Escherichia coli, Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Staphylococcus aureus IGMS-01), with ampicillin as a reference antibiotic, and for antifungal activity against Candida albicans, using fluconazole as a reference. The compounds showed moderate but significant efficacy across all tests. Docking analysis with microbial proteins revealed notable binding affinities for peptidomimetics 5h (N-(2-(1H-indol-3-yl)ethyl)-N-(1-(4-chlorophenyl)-2-(cyclohexylamino)-2-oxoethyl)stearamide) and 5i (N-(2-(1H-indol-3-yl)ethyl)-N-(1-(4-chlorophenyl)-2-(cyclohexylamino)-2-oxoethyl)oleamide). Molecular dynamics simulations confirmed stable interactions between the ligands and proteins. Furthermore, the long alkyl chain analogs demonstrated the ability to form organo/hydrogels, facilitating the incorporation of silver sulfadiazine for controlled antimicrobial release. This innovative approach enhances drug dispersion within the gel structure, effectively inhibiting microbial growth. These findings highlight the potential of these adaptable materials to advance drug development efforts in the foreseeable future.

Gonococcal Mimitope Vaccine Candidate Forms a Beta-Hairpin Turn and Binds Hydrophobically to a Therapeutic Monoclonal Antibody.

The spread of multidrug-resistant strains of Neisseria gonorrhoeae, the etiologic agent of gonorrhea, represents a global health emergency. Therefore, the development of a safe and effective vaccine against gonorrhea is urgently needed. In previous studies, murine monoclonal antibody (mAb) 2C7 was raised against gonococcal lipooligosaccharide (LOS). mAb 2C7 elicits complement-dependent bactericidal activity against gonococci, and its glycan epitope is expressed by almost every clinical isolate. Furthermore, we identified a peptide, cyclic peptide 2 (CP2) that mimicked the 2C7 LOS epitope, elicited bactericidal antibodies in mice, and actively protected in a mouse vaginal colonization model. In this study, we performed structural analyses of mAb 2C7 and its complex with the CP2 peptide by X-ray crystallography, NMR spectroscopy, and molecular dynamics (MD) simulations. The crystal structure of Fab 2C7 bound to CP2 showed that the peptide adopted a beta-hairpin conformation and bound the Fab primarily through hydrophobic interactions. We employed NMR spectroscopy and MD simulations to map the 2C7 epitope and identify the bioactive conformation of CP2. We also used small-angle X-ray scattering (SAXS) and native mass spectrometry to obtain further information about the shape and assembly state of the complex. Collectively, our new structural information suggests strategies for humanizing mAb 2C7 as a therapeutic against gonococcal infection and for optimizing peptide CP2 as a vaccine antigen.

Physicochemical Compatibility of Ceftolozane-Tazobactam with Parenteral Nutrition.

Ceftolozane-tazobactam (CT) is used for the treatment of complicated infections and for multidrug-resistant strains of Pseudomonas aeruginosa and extended-spectrum beta-lactamase-producing enterobacteria. In certain cases, simultaneous administration of CT and parenteral nutrition (PN) may be required, but compatibility of Y-site co-administration is unknown. The aim of this study was to analyse the physicochemical compatibility of CT Y-site administered with PN. We evaluated a protocolized PN approach for critical patients in our center. We studied both bolus infusion (2 g ceftolozane/1 g tazobactam in 1 h) and continuous infusion (CI) (6 g ceftolozane/3 g tazobactam) strategies. Samples were visually observed against light, microscopically inspected, and pH was analysed using a pH meter. The mean lipid droplet diameter (MDD) was determined via dynamic light scattering. CT concentration was quantified using HPLC-HRMS. No alterations were observed through visual or microscopic inspection. Changes in pH were ≤0.2, and changes in osmolarity were less than 5%. MDD remained below 500 nm (284.5 ± 2.1 for bolus CT and 286.8 ± 7.5 for CI CT). CT concentrations at t = 0 h and t = 24 h remained within prespecified parameters in both infusion strategies. CT is physiochemically compatible with PN during simulated Y-site administration at the tested concentration and infusion rates.

Biological potential, chemical profiling, and molecular docking study of Morus alba L. extracts

Morus alba L. is a plant with a long history of dietary and medicinal uses. We hypothesized that M. alba possesses a significant biological potential. In that sense, we aimed to generate the chemical, antimicrobial, toxicological, and molecular profile of M. alba leaf and fruit extracts. Our results showed that extracts were rich in vitamin C, phenols, and flavonoids, with quercetin and pterostilbene concentrated in the leaf, while fisetin, hesperidin, resveratrol, and luteolin were detected in fruit. Extracts exhibited antimicrobial activity against all tested bacteria, including multidrug-resistant strains. The widest inhibition zones were in Staphylococcus aureus ATCC 33591. The values of the minimum inhibitory concentration ranged from 15.62 μg/ml in Enterococcus faecalis to 500 μg/ml in several bacteria. Minimum bactericidal concentration ranged from 31.25 μg/ml to 1000 μg/ml. Extracts impacted the biofilm formation in a concentration-dependent and species-specific manner. A significant difference in the frequency of nucleoplasmic bridges between the methanolic extract of fruit (0.5 μg/ml, 1 μg/ml, 2 μg/ml), as well as for the frequency of micronuclei between ethanolic extract of leaf (2 μg/ml) and the control group was observed. Molecular docking suggested that hesperidin possesses the highest binding affinity for multidrug efflux transporter AcrB and acyl-PBP2a from MRSA, as well as for the SARS-CoV-2 Mpro. This study, by complementing previous research in this field, gives new insights that could be of great value in obtaining a more comprehensive picture of the Morus alba L. bioactive potential, chemical composition, antimicrobial and toxicological features, as well as molecular profile.

Risk factors for dairy cows mastitis in Algeria, antibiotic resistance and molecular typing of the causative Staphylococcus aureus.

Adoption of a rational management in dairy farms would improve the milk quality and farmers' income. In the current study, we aimed to describe bovine mastitis in 32 dairy herds, identify the main cow- and herd-associated risk factors, and analyze both epidemiological along with molecular characteristics of Staphylococcus aureus infecting udders. Based on Californian Mastitis Test and clinical examination, the prevalence of mastitis in cows was 52.25% (116/222), of which 6.3% was clinical mastitis and 45.94% was subclinical mastitis. Overall, 218 (24.54%) quarters suffered from mastitis, whose 29.81% (65/218) infected with S. aureus. Mastitis was lowest in mid-lactation with OR = 0.371 with 95% confidence interval (CI) of 0.141-0.976, and in cows separated from their calves (OR = 0.164, 95% CI 0.056-0.477) than suckler cows. Similar results were obtained from S. aureus related mastitis. To assess the genetic lineages of S. aureus isolates, we determined clonal complexes (CC) using DNA microarray hybridization profiles and performed spa typing. The strains were assigned to nine clonal complexes, and 19 spa types; with CC97 (44.77%), and CC22 (40.29%) were the most predominant lineages and t223 (40.29%), t7136 (10.44%), t359 (8.95%) and t267 (5.97%) were the most common spa types. A total of 88.05% (n = 59) isolates were resistant to at least one tested antibiotic while only 4.47% were multi-drug resistant strains. Higher rates of resistance were observed for penicillin (86.5%) and tetracycline (14.9%) respectively. Our results show the need for adoption of feasible mastitis program with special emphasis on sub-clinical mastitis and associated risk factors.

Genetic characterization of blaCTX-M-65 in Salmonella Infantis and blaCMY-2 in Salmonella Heidelberg isolated from fresh ground turkey meat sold in supermarkets in Los Andes and San Felipe, Chile

Annually, food poisoning caused by non-typhoidal Salmonella (NTS) accounts for 40 million foodborne infections worldwide. Outbreaks due to multidrug-resistant NTS strains are associated with the consumption of poultry products. We aimed to determine the proportion of NTS in ground turkey meat available at supermarkets in two locations in Chile, characterizing their serovars, virulence traits, and antimicrobial resistance profiles. Between September and December 2018, we analyzed 47 samples of packed ground turkey meat purchased at 13 supermarkets. NTS were identified by MALDI-TOF, and antimicrobial susceptibility was determined by the disk-diffusion agar method. Whole genome sequencing was performed with MiSeq (Illumina) followed by Nullarbor analysis. NTS was detected in 6 out of 47 samples (12.8 %, 95 %CI: 6.0–25.1 %), identifying S. enterica serovar Infantis (n=4 isolates), serovar Agona (n=1 isolate), and serovar Heidelberg (n=1 isolate), respectively. S. Infantis belonged to sequence type (ST)32, differentiating two clones, whereas the S. Agona was ST13 and S. Heidelberg was ST15. S. Infantis strains were multidrug antibiotic resistant, harboring blaCTX-M-65, tetA, and mutations that confer fosfomycin resistance. Serovars Agona and Heidelberg showed tetracycline (tetB) and fosfomycin resistance (fosA7). Additionally, serovar Heidelberg showed resistance to sulfamethoxazole-trimethoprim, aminoglycosides, and carried the blaCMY-2 gene. This is the first report in Chile about NTS detected in raw ground turkey meat available in supermarkets. S. Infantis and S. Agona strains showed a phylogenetic relationship with strains of the same serovars isolated from the environment in our country. This situation would impact food poisoning and the dissemination of bacterial resistance between animals, humans, and the environment.

The transcriptional regulation of the horizontally acquired iron uptake system, yersiniabactin and its contribution to oxidative stress tolerance and pathogenicity of globally emerging salmonella strains

ABSTRACT The bacterial species Salmonella enterica (S. enterica) is a highly diverse pathogen containing more than 2600 distinct serovars, which can infect a wide range of animal and human hosts. Recent global emergence of multidrug resistant strains, from serovars Infantis and Muenchen is associated with acquisition of the epidemic megaplasmid, pESI that augments antimicrobial resistance and pathogenicity. One of the main pESI’s virulence factors is the potent iron uptake system, yersiniabactin encoded by fyuA, irp2-irp1-ybtUTE, ybtA, and ybtPQXS gene cluster. Here we show that yersiniabactin, has an underappreciated distribution among different S. enterica serovars and subspecies, integrated in their chromosome or carried by different conjugative plasmids, including pESI. While the genetic organization and the coding sequence of the yersiniabactin genes are generally conserved, a 201-bp insertion sequence upstream to ybtA, was identified in pESI. Despite this insertion, pESI-encoded yersiniabactin is regulated by YbtA and the ancestral Ferric Uptake Regulator (Fur), which binds directly to the ybtA and irp2 promoters. Furthermore, we show that yersiniabactin genes are specifically induced during the mid-late logarithmic growth phase and in response to iron-starvation or hydrogen peroxide. Concurring, yersiniabactin was found to play a previously unknown role in oxidative stress tolerance and to enhance intestinal colonization of S. Infantis in mice. These results indicate that yersiniabactin contributes to Salmonella fitness and pathogenicity in vivo and is likely to play a role in the rapid dissemination of pESI among globally emerging Salmonella lineages.