Assessment of three antibiotic combination regimens against Gram-negative bacteria causing neonatal sepsis in low- and middle-income countries.

Gram-negative bacteria (GNB) are a major cause of neonatal sepsis in low- and middle-income countries (LMICs). Although the World Health Organization (WHO) reports that over 80% of these sepsis deaths could be prevented through improved treatment, the efficacy of the currently recommended first- and second-line treatment regimens for this condition is increasingly affected by high rates of drug resistance. Here we assess three well known antibiotics, fosfomycin, flomoxef and amikacin, in combination as potential antibiotic treatment regimens by investigating the drug resistance and genetic profiles of commonly isolated GNB causing neonatal sepsis in LMICs. The five most prevalent bacterial isolates in the NeoOBS study (NCT03721302) are Klebsiella pneumoniae, Acinetobacter baumannii, E. coli, Serratia marcescens and Enterobacter cloacae complex. Among these isolates, high levels of ESBL and carbapenemase encoding genes are detected along with resistance to ampicillin, gentamicin and cefotaxime, the current WHO recommended empiric regimens. The three new combinations show excellent in vitro activity against ESBL-producing K. pneumoniae and E. coli isolates. Our data should further inform and support the clinical evaluation of these three antibiotic combinations for the treatment of neonatal sepsis in areas with high rates of multidrug-resistant Gram-negative bacteria.

Assessment of bacterial profile, antimicrobial susceptibility status, and associated factors of isolates among hospitalized patients at Dessie Comprehensive Specialized Hospital, Northeast Ethiopia.

BACKGROUND: Antimicrobial resistant bacteria among hospitalized patients are becoming a major public health threat worldwide, mainly in developing countries. Infections by these multidrug resistant pathogens cause high rate of mortality, prolong hospital stays, and affect individual and country economies in greater amounts. Thus, this study aimed to assess the bacterial profile, antimicrobial susceptibility status, and associated factors of isolates from hospitalized patients at the Dessie Comprehensive Specialized Hospital. METHODOLOGY: This hospital-based cross-sectional study was conducted between February and April 2021. Consecutive sampling was used to select the study participants. All bacterial isolates were identified using standard bacteriological techniques. Antibiotic susceptibility testing was performed using disk diffusion technique. The data was analyzed using SPSS version 25. Descriptive statistics and logistic regression were used. A P-value of less than 0.05 was considered statistically significant. RESULTS: Of 384 clinical samples (blood, urine, stool, wound, vaginal discharge, and ear discharge) processed 180 (46.9%) were culture positive. Overall, Escherichia coli was the predominant isolate (41; 22.8%), followed by Staphylococcus aureus (36; 20%). Most of the isolates were from blood (70; 38.9%). The level of overall drug resistance of the gram-negative bacteria isolates for ampicillin, tetracycline, and cotrimoxazole was (104; 88.1%), (79; 75.9%), and (78; 75.0%), respectively. The overall multidrug rate of isolates was 143 (79.4%). Variables such as history of invasive procedures, chronic underlying diseases, history of hospitalization, and habit of eating raw animal products were statistically significant for the acquisition of bacterial infection. CONCLUSIONS AND RECOMMENDATION: E. Coli and S. aureus were the most common isolates. Most of the isolates were resistant to commonly prescribed antibiotics. And also, consumption of raw animal products, chronic underlying disease, previous hospitalization, history of invasive procedures, and educational status were associated with the acquisition of bacterial infections. Therefore, routine antimicrobial susceptibility testing, proper patient management, wise use of antibiotics in clinical settings and health education are recommended.

Reducing Hospitalizations and Multidrug-Resistant Organisms via Regional Decolonization in Hospitals and Nursing Homes.

Importance: Infections due to multidrug-resistant organisms (MDROs) are associated with increased morbidity, mortality, length of hospitalization, and health care costs. Regional interventions may be advantageous in mitigating MDROs and associated infections. Objective: To evaluate whether implementation of a decolonization collaborative is associated with reduced regional MDRO prevalence, incident clinical cultures, infection-related hospitalizations, costs, and deaths. Design, Setting, and Participants: This quality improvement study was conducted from July 1, 2017, to July 31, 2019, across 35 health care facilities in Orange County, California. Exposures: Chlorhexidine bathing and nasal iodophor antisepsis for residents in long-term care and hospitalized patients in contact precautions (CP). Main Outcomes and Measures: Baseline and end of intervention MDRO point prevalence among participating facilities; incident MDRO (nonscreening) clinical cultures among participating and nonparticipating facilities; and infection-related hospitalizations and associated costs and deaths among residents in participating and nonparticipating nursing homes (NHs). Results: Thirty-five facilities (16 hospitals, 16 NHs, 3 long-term acute care hospitals [LTACHs]) adopted the intervention. Comparing decolonization with baseline periods among participating facilities, the mean (SD) MDRO prevalence decreased from 63.9% (12.2%) to 49.9% (11.3%) among NHs, from 80.0% (7.2%) to 53.3% (13.3%) among LTACHs (odds ratio [OR] for NHs and LTACHs, 0.48; 95% CI, 0.40-0.57), and from 64.1% (8.5%) to 55.4% (13.8%) (OR, 0.75; 95% CI, 0.60-0.93) among hospitalized patients in CP. When comparing decolonization with baseline among NHs, the mean (SD) monthly incident MDRO clinical cultures changed from 2.7 (1.9) to 1.7 (1.1) among participating NHs, from 1.7 (1.4) to 1.5 (1.1) among nonparticipating NHs (group × period interaction reduction, 30.4%; 95% CI, 16.4%-42.1%), from 25.5 (18.6) to 25.0 (15.9) among participating hospitals, from 12.5 (10.1) to 14.3 (10.2) among nonparticipating hospitals (group × period interaction reduction, 12.9%; 95% CI, 3.3%-21.5%), and from 14.8 (8.6) to 8.2 (6.1) among LTACHs (all facilities participating; 22.5% reduction; 95% CI, 4.4%-37.1%). For NHs, the rate of infection-related hospitalizations per 1000 resident-days changed from 2.31 during baseline to 1.94 during intervention among participating NHs, and from 1.90 to 2.03 among nonparticipating NHs (group × period interaction reduction, 26.7%; 95% CI, 19.0%-34.5%). Associated hospitalization costs per 1000 resident-days changed from $64 651 to $55 149 among participating NHs and from $55 151 to $59 327 among nonparticipating NHs (group × period interaction reduction, 26.8%; 95% CI, 26.7%-26.9%). Associated hospitalization deaths per 1000 resident-days changed from 0.29 to 0.25 among participating NHs and from 0.23 to 0.24 among nonparticipating NHs (group × period interaction reduction, 23.7%; 95% CI, 4.5%-43.0%). Conclusions and Relevance: A regional collaborative involving universal decolonization in long-term care facilities and targeted decolonization among hospital patients in CP was associated with lower MDRO carriage, infections, hospitalizations, costs, and deaths.

Antibiotic resistance begets more resistance: chromosomal resistance mutations mitigate fitness costs conferred by multi-resistant clinical plasmids.

Plasmids are the primary vectors of horizontal transfer of antibiotic resistance genes among bacteria. Previous studies have shown that the spread and maintenance of plasmids among bacterial populations depend on the genetic makeup of both the plasmid and the host bacterium. Antibiotic resistance can also be acquired through mutations in the bacterial chromosome, which not only confer resistance but also result in changes in bacterial physiology and typically a reduction in fitness. However, it is unclear whether chromosomal resistance mutations affect the interaction between plasmids and the host bacteria. To address this question, we introduced 13 clinical plasmids into a susceptible Escherichia coli strain and three different congenic mutants that were resistant to nitrofurantoin (ΔnfsAB), ciprofloxacin (gyrA, S83L), and streptomycin (rpsL, K42N) and determined how the plasmids affected the exponential growth rates of the host in glucose minimal media. We find that though plasmids confer costs on the susceptible strains, those costs are fully mitigated in the three resistant mutants. In several cases, this results in a competitive advantage of the resistant strains over the susceptible strain when both carry the same plasmid and are grown in the absence of antibiotics. Our results suggest that bacteria carrying chromosomal mutations for antibiotic resistance could be a better reservoir for resistance plasmids, thereby driving the evolution of multi-drug resistance.IMPORTANCEPlasmids have led to the rampant spread of antibiotic resistance genes globally. Plasmids often carry antibiotic resistance genes and other genes needed for its maintenance and spread, which typically confer a fitness cost on the host cell observed as a reduced growth rate. Resistance is also acquired via chromosomal mutations, and similar to plasmids they also reduce bacterial fitness. However, we do not know whether resistance mutations affect the bacterial ability to carry plasmids. Here, we introduced 13 multi-resistant clinical plasmids into a susceptible and three different resistant E. coli strains and found that most of these plasmids do confer fitness cost on susceptible cells, but these costs disappear in the resistant strains which often lead to fitness advantage for the resistant strains in the absence of antibiotic selection. Our results imply that already resistant bacteria are a more favorable reservoir for multi-resistant plasmids, promoting the ascendance of multi-resistant bacteria.

Increase of multidrug-resistant bacteria after the COVID-19 pandemic in a major teaching Hospital in Sicily (2018-2021).

INTRODUCTION: The COVID-19 pandemic has further highlighted the continuing threat of antimicrobial resistance (AMR) to global health and economic development. In the last two decades, AMR has raised increasing concern, with an estimated 4.95 million deaths globally due to bacterial AMR in 2019 alone. The aim of this study was to analyse the impact of the pandemic on the spread of multidrug-resistant organisms (MDROs) using data from the Hospital "P. Giaccone" in Palermo, comparing pre-pandemic and pandemic periods. METHODS: This observational study involved adult patients who were discharged from the hospital between 01 January 2018 and 31 December 2021. Hospital Discharge Cards were linked with microbiological laboratory reports to assess MDRO isolations. SARS-CoV-2 positivity during hospitalisation was evaluated using the National Institute of Health surveillance system. RESULTS: A total of 58 427 hospitalisations were evaluated in this study. Half the patients were aged over 65 years (N=26 984) and most admissions were in the medical area (N=31 716). During the hospitalisation period, there were 2681 patients (5%) with MDROs isolations, and 946 patients (2%) were positive for SARS-CoV-2. Multivariable analyses showed that during 2020 and 2021, there was a significantly increased risk of isolation of Staphylococcus aureus, Acinetobacter baumannii, and Klebsiella pneumoniae. Age, weight of the Diagnosis-Related Group (DRG), wards with higher intensity of care, and length-of-stay were associated with a higher risk of MDRO isolation. CONCLUSION: This study provides new insights into the impact of the COVID-19 pandemic on MDRO isolation and has important implications for infection control and prevention efforts in healthcare facilities. Age, DRG-weight, and longer hospital stays further increased the risk of MDRO isolation. Thus, it is imperative to improve and follow hospital protocols to prevent healthcare-associated infections.

Assessment of Antibiotic Resistance among Clinical Isolates of Enterobacteriaceae in Nepal.

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

Assessment of the potential of phage-antibiotic synergy to induce collateral sensitivity in Salmonella Typhimurium.

This study was designed to evaluate the synergistic effect of phage and antibiotic on the induction of collateral sensitivity in Salmonella Typhimurium. The synergistic effects of Salmonella phage PBST32 combined with ciprofloxacin (CIP) against S. Typhimurium KCCM 40253 (STKCCM) were evaluated using a fractional inhibitory concentration (FIC) assay. The CIP susceptibility of STKCCM was increased when combined with PBST32, showing 16-fold decrease at 7 log PFU/mL. The combination of 1/2 × MIC of CIP and PBST32 (CIP[1/2]+PBST32) effectively inhibited the growth of STKCCM up to below the detection limit (1.3 log CFU/mL) after 12 h of incubation at 37 °C. The significant reduction in bacterial swimming motility was observed for PBST32 and CIP[1/4]+PBST32. The CIP[1/4]+PBST32 increased the fitness cost (relative fitness = 0.57) and decreased the cross-resistance to different classes of antibiotics. STKCCM treated with PBST32 alone treatment exhibited the highest coefficient of variation (90%), followed by CIP[1/4]+PBST32 (75%). These results suggest that the combination of PBST32 and CIP can be used to control bacterial pathogens.

Rapid cross-border emergence of NDM-5-producing Escherichia coli in the European Union/European Economic Area, 2012 to June 2022.

Whole genome sequencing data of 874 Escherichia coli isolates carrying bla NDM-5 from 13 European Union/European Economic Area countries between 2012 and June 2022 showed the predominance of sequence types ST167, ST405, ST410, ST361 and ST648, and an increasing frequency of detection. Nearly a third (30.6%) of these isolates were associated with infections and more than half (58.2%) were predicted to be multidrug-resistant. Further spread of E. coli carrying bla NDM-5 would leave limited treatment options for serious E. coli infections.

Assessment of multidrug-resistant profile, multi-locus sequence typing and efflux pump activity in Salmonella Typhimurium isolated from hospital sewage.

Salmonella enterica serovar Typhimurium is becoming a leading cause of gastroenteritis and mortality. The use of antibiotics has increased natural resistance of S. Typhimurium to antibiotics. This study aims to isolate and characterize multi-drug-resistant (MDR) Salmonella strains from hospital sewage samples in Bhopal City, central India. The MDR isolates were characterized by molecular identification, antimicrobial resistance patterns, multi-locus sequence typing, and efflux pump activity. Specific genes (hilA, stn, invA, typh, and iroB) were used to confirm S. Typhimurium isolates. The Kirbey-Bauer method was employed to profile antimicrobial resistance using 20 antibiotics. Multi-locus sequence typing confirmed S. Typhimurium using seven housekeeping genes (aroC, dnaN, hemD, hisD, purE, sucA, and thr). Out of five strains, only four were confirmed as S. Typhimurium during MLST analysis. Efflux pump activity was determined using the ethidium bromide (EtBr) cartwheel test. Of the 160 isolates, 38 were presumptively confirmed as S. Typhimurium based on biochemical characterization, and only five MDR Salmonella strains were selected for their resistance against most antibiotics. Efflux pump activity revealed that five out of the four MDR isolates did not retain EtBr inside the cells, indicating pronounced efflux activity. Additionally, the isolated strains showed a specific correlation between the antimicrobial phenotypes and genotypes. The results of this study provide a better understanding of the characterization of S. Typhimurium serotype in Bhopal City. Future studies should focus on understanding changing antimicrobial resistance patterns, pathogenicity, and the genetic background of Salmonella serotypes. Further surveillance activities for antimicrobial-resistant Salmonella in different environmental sources should be prioritized.

Effect of antimicrobial consumption on Escherichia coli resistance: assessment and forecasting using Dynamic Regression models in a French university hospital (2014-2019).

INTRODUCTION: The aim of this study was to determine the correlation between antimicrobial consumption (AMC) and antimicrobial resistance (AMR) in Escherichia coli at a hospital level, and assess the capacity of dynamic regression (DR) models to predict AMR for their use in deployment of antimicrobial stewardship programs (ASPs). METHODS: A retrospective epidemiological study was conducted in a French tertiary hospital between 2014 and 2019. DR models were used to assess the correlation between AMC and AMR from 2014 to 2018. The predictive abilities of the models were estimated by comparing the predicted data with those observed in 2019. RESULTS: Rates of fluoroquinolone and cephalosporin resistance decreased. AMC increased overall but decreased for fluoroquinolone. DR models highlighted that the decrease in use of fluoroquinolone and the increase in use of anti-pseudomonal activity penicillin with beta-lactamase inhibitor (AAPBI) explained 54% of the decrease in fluoroquinolone resistance and 15% of the decrease in cephalosporin resistance. In addition, penicillin/beta-lactamase inhibitor (PBI) consumption explained 53% of PBI resistance, and beta-lactam use explained 36% of penicillin resistance, with both remaining stable over time. DR models had predictive capabilities with margins of error from 8% to 34%. CONCLUSION: Over a six-year period in a French tertiary hospital, decreasing rates of resistance to fluoroquinolones and cephalosporins were correlated with decreasing use of fluoroquinolone and increasing use of AAPBI, whereas rates of resistance to penicillin remained high and stable. The results indicate that DR models should be used with caution for AMR forecasting and ASP implementation.

Impact of septic episodes caused by Acinetobacter baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa in a tertiary hospital: clinical and economic considerations in years 2018-2020.

OBJECTIVE: To evaluate incidence, therapy and antibiotic resistance trends in septic episodes caused by three multi-drug resistant bacteria in a tertiary hospital, by also estimating their economic impact. METHODS: An observational, retrospective-cohort analysis was based on data related to patients admitted to the "SS. Antonio e Biagio e Cesare Arrigo" Hospital in Alessandria (Italy) between 2018 and 2020, that developed sepsis from multi-drug resistant bacteria of the examined species. Data were retrieved from medical records and from the hospital's management department. RESULTS: Inclusion criteria led to enrolment of 174 patients. A relative increase in A. baumannii cases (p < 0.0001) and an increasing resistance trend for K. pneumoniae (p < 0.0001) were detected in 2020 compared to 2018-2019. Most patients were treated with carbapenems (72.4%), although the use of colistin rose significantly in 2020 (62.5% vs 36%, p = 0.0005). Altogether, these 174 cases caused 3295 additional hospitalisation days (mean 19 days/patient): the consequent expenditure attained ≈ 3 million Euros, 85% of which (≈2.5 million Euros) due to the cost of extra hospital stay. Specific antimicrobial therapy accounted for 11.2% of the total (≈336,000 €). CONCLUSIONS: Healthcare-related septic episodes cause a considerable burden. Moreover, a trend could be spotted towards higher relative incidence of complex cases recently.

Genome-based risk assessment for foodborne Salmonella enterica from food animals in China: A One Health perspective.

Salmonella is one of the most common causes of foodborne bacterial disease. Animal-borne foods are considered the primary sources of Salmonella transmission to humans. However, genomic assessment of antimicrobial resistance (AMR) and virulence of Salmonella based on One Health approach remains obscure in China. For this reason, we analyzed the whole genome sequencing data of 134 Salmonella isolates recovered from different animal and meat samples in China. The 134 Salmonella were isolated from 2819 samples (4.75 %) representing various sources (pig, chicken, duck, goose, and meat) from five Chinese provinces (Zhejiang, Guangdong, Jiangxi, Hunan, and Qinghai). AMR was evaluated by the broth dilution method using 13 different antimicrobial agents, and results showed that 85.82 % (115/134) of isolates were resistant to three or more antimicrobial classes and were considered multidrug-resistant (MDR). Twelve sequence types (STs) were detected, with a dominance of ST469 (29.85 %, 40/134). The prediction of virulence genes showed the detection of cdtB gene encoding typhoid toxins in one isolate of S. Muenster recovered from chicken, while virulence genes associated with type III secretion systems were detected in all isolates. Furthermore, plasmid-type prediction showed the abundance of IncFII(S) (13/134; 9.7 %) and IncFIB(S) (12/134; 8.95 %) in the studied isolates. Together, this study demonstrated the ability to use whole-genome sequencing (WGS) as a cost-effective method to provide comprehensive knowledge about foodborne Salmonella isolates in One Health surveillance approach.

Highly Sensitive Detection of Complicated Mutations of Drug Resistance in Mycobacterium tuberculosis Using a Simple, Accurate, Rapid, and Low-Cost Tailored-Design Competitive Wild-Type Blocking Assay.

Establishing simple, rapid, and highly sensitive molecular assays is crucial for timely diagnosis and effective treatment of drug-resistant tuberculosis. However, current genotypic drug susceptibility testing (DST) still encounters enormous challenges including lower sensitivity than phenotypic DST and insufficient accuracy. Herein, a simple, low-cost, multiplex real-time polymerase chain reaction-based assay is established to achieve highly sensitive detection of low-abundant mutants through competitive wild-type blocking (COWTB). Analytical performance of the COWTB assay can achieve 1% or even 0.1% mutants under background of 10 000 wild-type genomes/test. Furthermore, clinical practice feasibility is evaluated to identify resistance to rifampicin (RIF), isoniazid (INH), and streptomycin (SM) on 92 actual clinical samples, its sensitivity is 93.8% for RIF and 100% for INH and SM, and specificity is 100% each for RIF, INH, and SM when using DNA sequencing as the reference standard. In comparison, the sensitivity of reverse dot blotting assay commonly used in clinics is 93.8%, 90.0%, and 84.6%, and the specificity is 96.1%, 98.6%, and 100% for RIF, INH, and SM, respectively. Importantly, the COWTB assay can also be applicable for other drug-resistant mutations and pave a promising detection strategy to fill the gap between phenotypic and genotypic DST for detecting low-abundant drug-resistant M. tuberculosis.

Intestinal toxicity and resistance gene threat assessment of multidrug-resistant Shigella: A novel biotype pollutant.

Multidrug-resistant bacteria, especially pathogens, pose a serious threat to disease treatment and recovery, but their potential toxicity to animal development is not entirely clear. As the most important site for nutrient absorption, we studied the intestinal microbiome of Xenopus tropicalis by analyzing the effect of multidrug-resistant Shigella on its intestinal health. Unlike in the control, Shigella intake promoted the secretion of neutral mucus and inhibited intestinal development and weight gain. Following 60 days of exposure, intestinal crypt atrophy, intestinal villus shortening, internal cavity enlargement, and external mucosal muscle disintegration were observed. The circular and longitudinal intestinal muscles became thinner with increasing pathogen exposure. In addition, the presence of Shigella altered the expression of multiple cytokines and classic antioxidant enzyme activities in the gut, which may have caused the intestinal lesions that we observed. 16 S rDNA sequencing analysis of intestinal samples showed that exposure to Shigella destroyed the normal gut microbial abundance and diversity and increased the functional bacterial ratio. Notably, the increased abundance of intestinal antibiotic resistance genes (ARGs) may imply that the resistance genes carried by Shigella easily migrate and transmit within the intestine. Our results expand existing knowledge concerning multidrug-resistant Shigella-induced intestinal toxicity in X. tropicalis and provide new insights for the threat assessment of resistance genes carried by drug-resistant pathogens.

Computational assessment of phytochemicals of medicinal plants from Mexico as potential inhibitors of Salmonella enterica efflux pump AcrB protein.

The AcrAB-TolC efflux pump (EP) confers multidrug resistance to Salmonella enterica, a major etiological agent of foodborne infections. Phytochemicals that inhibit the functions of AcrAB-TolC EP present ideal candidates for reversal of antibiotic resistance. Progressive technological advancements, have facilitated the development of computational methods that offer a rapid low-cost approach to screen and identify phytochemicals with inhibitory potential against EP. In this study, 71 phytochemicals derived from plants used for medicinal purposes in Mexico were screened for their potential as inhibitors of Salmonella AcrB protein using in silico approaches including molecular docking and molecular dynamics (MD) simulation. Consequently, naringenin, 5-methoxypsoralen, and licarin A were identified as candidate inhibitors of AcrB protein. The three phytochemicals bound distal/deep pocket (DP) and hydrophobic trap (HPT) residues of AcrB protein critical for interactions with inhibitors, with estimated binding free energies of -95.5 kJ/mol, -97.4 kJ/mol, and -143.8 kJ/mol for naringenin, 5-methoxypsoralen, and licarin A, respectively. Data from the 50 ns MD simulation study revealed stability of the protein-ligand complex and alterations in the AcrB protein DP conformation upon binding of phytochemicals to the DP and HPT regions. Based on the estimated binding free energy and interactions with three out of five residues lining the hydrophobic trap, licarin A demonstrated the highest inhibitory potential, supporting its further application as a candidate for overcoming drug resistance in pathogens. Communicated by Ramaswamy H. Sarma.

Clinical and economic burden of bacteremia due to multidrug-resistant organisms in Korea: a prospective case control study.

OBJECTIVES: The socioeconomic and clinical burden of multidrug-resistant organisms (MDRO), including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), multidrug-resistant Acinetobacter baumannii (MRAB), multidrug-resistant Pseudomonas aeruginosa (MRPA), and carbapenem-resistant Enterobacteriaceae (CRE) have not yet been adequately addressed. METHODS: We prospectively searched for MDRO bacteremia cases with matched controls from 10 hospitals across Korea during a 6-month period in 2017. Patients were classified into the MDRO, susceptible organism, and no-infection groups. The corresponding susceptible or no-infection controls had been selected according to predefined criteria. We collected clinical information and estimated the total additional medical cost due to MDRO infections using the multistate model. RESULTS: During the 6-month period, a total of 486 MDRO bacteremia cases (260, 87, 18, 20, and 101 cases of MRSA, MRAB, MRPA, CRE, and VRE, respectively) were identified. The 90-d mortality rates were 30.4%, 63.2%, 16.7%, 55.0%, and 47.5%, respectively. The additional costs caused by bacteremia were $15 768, $35 682, $39 908, $72 051, and $33 662 per MDRO type, respectively. Based on these 6-month data, the estimated annual number of bacteremia cases due to these five MDRO in Korea were 7979 (4070, 1396, 218, 461, and 1834 cases, respectively). Overall, this caused an estimated 3280 (1237, 882, 36, 254, and 871, respectively) deaths and cost $294 505 002 ($84 707 359, $74 387 364, $10 344 370, $45 850 215, and $79 215 694, respectively) (range $170,627,020-$416,094,679) in socioeconomic loss. CONCLUSIONS: A tremendous clinical and economic burden is caused by MDRO bacteremia compared with antibiotic-susceptible and no-infection groups. Substantial investment and efforts by related government agencies and medical staffs are needed.

Pharmacokinetics and pharmacodynamics of polymyxin B and proposed dosing regimens in elderly patients with multi-drug-resistant Gram-negative bacterial infections.

There are limited data on the pharmacokinetics (PK) and pharmacodynamics (PD) of polymyxin B in the elderly population. The objective of this study was to develop a population PK model of polymyxin B in elderly patients, determine factors that affect its PK parameters, and propose alternative dosing regimens. Critically ill elderly patients (age ≥65 years) who received intravenous polymyxin B for multi-drug-resistant Gram-negative bacterial infections were enrolled. A population PK model was developed using Phoenix NLME software. Monte Carlo simulations were performed to optimize regimens attaining the PK/PD target of AUC24h/MIC >50 and target exposure of 50-100 mg‧h/L. Clinical efficacy and nephrotoxicity of polymyxin B treatment were also assessed. A total of 142 polymyxin B concentrations from 23 patients were available. A two-compartment model with first-order elimination was developed, and albumin was the significant covariate of PK parameters. However, albumin had only a slight effect on polymyxin B exposure. Simulation results indicated that two fixed regimens of 50 mg and 75 mg would be sufficient to reach the PK/PD targets when the minimum inhibitory concentrations was ≤0.5 mg/L. With the exception of 1.25 mg/kg for 58 kg, other weight-based regimens (1.25-1.5 mg/kg for 70 kg and 80 kg; twice daily) may result in at least 40% of predicted AUCss,24h >100 mg‧h/L. In conclusion, fixed maintenance dosing of 50 mg and 75 mg for polymyxin B may maximize efficacy while balancing nephrotoxicity concerns for elderly patients.

Identification and assessment of antimicrobial resistance bacteria in a hemodialysis water treatment system.

The water treatment process is a vital factor for hemodialysis (HD) patients. This study aimed to assess the degree of contamination of HD water by bacteria at the HD center of Mohammedia, Morocco, in addition to evaluating the antimicrobial resistance of isolated bacteria. Fifty-four water samples were taken, the appropriate cultures were used to isolate the pathogenic bacteria, which were identified biochemically and molecularly by 16S RNA sequencing. Their susceptibility to antimicrobial drugs was determined by the disk diffusion method. Approximately 5.5% of water samples were above the norm. The isolated bacteria that colonized the HD systems were mostly Gram-negative bacilli, such as Stenotrophomonas maltophilia, Pseudomonas spp., and Burkholderia cepacian. Results of the antibiotics test showed remarkable resistance levels. Among Pseudomonas spp. and S. maltophilia, 10 strains were classified as multidrug-resistant (MDR), and 4 as extensively drug-resistant (XDR). The diversity of bacterial strains isolated in the water used for HD treatments, and their worrying resistance levels pose a significant risk to patients. For these reasons, an urgent need for periodic microbiological monitoring of water after each treatment step must be applied, and the treatment process should also be optimized.

Comparative assessment of the mouse immune responses to colistin-resistant and colistin-sensitive isolates of Acinetobacter baumannii.

Acinetobacter baumannii is known as the most frequent species in clinical samples that is responsible for a large number of nosocomial infection outbreaks. The colistin-resistance of this bacterium has been found to be increasing. This study aimed to evaluate the immune response to colistin-susceptible and colistin-resistant A. baumannii isolates in a mouse model. Samples were prepared from the wounds of patients suspected of A. baumannii admitted to the intensive care unit of Namazi Hospital in Shiraz. Antibiotic susceptibility was studied by disk diffusion and broth microdilution according to CLSI and EUCAST criteria. Among the isolates, one colistin-sensitive isolate and one colistin-resistant isolate were injected intraperitoneally to BALB/C mice. Blood samples were collected after 4 h and cytokines (IL1-ß, IL-12, IFN γ, and IL-10) and surface markers (CD4, CD8, CD3, and CD45) were determined by ELISA and flow cytometry. Then, hematologic and histopathological factors were analyzed, and colony count in lung, liver, kidney, and spleen tissues were also performed. The results showed that levels of cytokines (IL1-ß, IL-12, IFN γ, and IL-10) and markers (CD4, CD8, CD3 and CD45) were higher in mice receiving colistin-resistant A. baumannii isolates than in mice receiving colistin-sensitive A. baumannii isolates, indicating that colistin-resistant isolates 4 h following the intraperitoneal injection stimulated host innate immune system better and produced a stronger immune response. On the other hand, histopathological findings showed inflammatory cell infiltration, hyperemia, and tissue damage. In addition, the bacterial load and tissue damage in the lung was higher than other tissues. The results of this study can have promising potential for the development of a prevention and treatment strategy based on cellular immune response for infection caused by colistin-sensitive and colistin-resistant A. baumannii.

Development and Assessment of a Novel Whole-Gene-Based Targeted Next-Generation Sequencing Assay for Detecting the Susceptibility of Mycobacterium tuberculosis to 14 Drugs.

Targeted next-generation sequencing (tNGS) has emerged as an alternative method for detecting drug-resistant tuberculosis (DR-TB). To provide comprehensive drug susceptibility information and to address mutations missed by available commercial molecular diagnostics, we developed and evaluated a tNGS panel with 22 whole-gene targets using the Ion Torrent platform to predict drug resistance to 14 drugs, namely, rifampicin (RIF), isoniazid (INH), ethambutol (EMB), pyrazinamide (PZA), moxifloxacin (MFX), levofloxacin (LFX), amikacin (AMK), capreomycin (CM), kanamycin (KM), streptomycin (SM), bedaquiline (BDQ), clofazimine (CFZ), linezolid (LZD), and delamanid (DLM). We selected 50 and 35 Mycobacterium tuberculosis isolates with various DR profiles as the training set and the challenge set, respectively. Comparative variant analyses of the DR genes were performed using Sanger sequencing and whole-genome sequencing (WGS). Phenotypic drug susceptibility testing (pDST) results were used as gold standards. Regarding the limit of detection, the tNGS assay detected 2.9 to 3.8% minority variants in 4% mutant mixtures. The sensitivity and specificity of tNGS were 97.0% (95% confidence interval [CI] = 93.1 to 98.7%) and 99.1% (95% CI = 97.7 to 99.7%), respectively. The concordance of tNGS with pDST was 98.5% (95% CI = 97.2 to 99.2%), which was comparable to that of WGS (98.7%, 95% CI = 97.4 to 99.3%) and better than that of Sanger sequencing (96.9%, 95% CI = 95.3 to 98.0%). The agreement between tNGS and pDST was almost perfect for RIF, INH, EMB, MFX, LFX, AMK, CM, KM, SM, BDQ, and LZD (kappa value = 0.807 to 1.000) and substantial for PZA (kappa value = 0.791). Our customized novel whole-gene-based tNGS panel is highly consistent with pDST and WGS for comprehensive and accurate prediction of drug resistance in a strengthened and streamlined DR-TB laboratory program. IMPORTANCE We developed and validated a tNGS assay that was the first to target 22 whole genes instead of regions of drug resistance genes and comprehensively detected susceptibility to 14 anti-TB drugs, with great flexibility to include new or repurposed drugs. Notably, we demonstrated that our custom-designed Ion AmpliSeq TB research panel platform had high concordance with pDST and could significantly reduce turnaround time (by approximately 70%) to meet a clinically actionable time frame. Our tNGS assay is a promising DST solution for providing needed clinical information for precision medicine-guided therapies for DR-TB and allows the rollout of active pharmacovigilance.