Antimicrobial resistance--a 'rising tide' of national (and international) risk

Infection Prevention Control Strategies of New Delhi Metallo-β-lactamase Producing Klebsiella pneumoniae

The spread of multi-drug resistant organisms (MDROs) is increasing at an alarming rate worldwide. Among these, Carbapenemase-producing New Delhi Metallo-β-lactamase (NDM) poses a significant clinical threat, and appropriate measures must be taken to prevent or limit its penetration into still-free territories. The present report describes two independent cases of patients from Ukraine colonized by NDM-producing Klebsiella pneumoniae and admitted to two separate wards of an acute university hospital in a territory not yet affected by Carbapenemase producers of this class. Moreover, this report illustrates the infection prevention control (IPC) strategies promptly implemented by the IPC operational team to verify the possible spread of the microorganism in the ward and avoid any possible further contamination. The identification of genes coding for Carbapenemases, performed using real-time PCR, revealed no other cases within the wards involved. These cases emphasize the importance of early case recognition of multidrug-resistant bacteria, the necessity of effective inter-hospital communication, the need for effective antimicrobial stewardship protocol, and the importance of adequate IPC policies. Additionally, we highlight the need to improve screening procedures in the case of patients from countries with a high prevalence of MDRO, as essential measures to prevent potential nosocomial outbreaks and/or endemization.

Healthcare-associated infections by multidrug-resistant bacteria in Andalusia, Spain, 2014 to 2021

BackgroundMultidrug-resistant (MDR) bacteria are among chief causes of healthcare-associated infections (HAIs). In Spain, studies addressing multidrug resistance based on epidemiological surveillance systems are lacking.AimIn this observational study, cases of HAIs by MDR bacteria notified to the epidemiological surveillance system of Andalusia, Spain, between 2014-2021, were investigated. Notified cases and their spatiotemporal distribution were described, with a focus on social determinants of health (SDoH).MethodsNew cases during the study period of HAIs caused by extended-spectrum β-lactamase (ESBL)-/carbapenemase-producing Enterobacterales, MDR Acinectobacter baumannii, MDR Pseudomonas aeruginosa or meticillin resistant Staphylococcus aureus were considered. Among others, notification variables included sex and age, while socio-economic variables comprised several SDoH. Cases' spatial distribution across municipalities was assessed. The smooth standardised incidence ratio (sSIR) was obtained using a Bayesian spatial model. Association between municipalities' sSIR level and SDoH was evaluated by bivariate analysis.ResultsIn total, 6,389 cases with a median age of 68 years were notified; 61.4% were men (n = 3,921). The most frequent MDR bacteria were ESBL-producing Enterobacterales (2,812/6,389; 44.0%); the main agent was Klebsiella spp. (2,956/6,389; 46.3%). Between 2014 and 2021 case numbers appeared to increase. Overall, up to 15-fold differences in sSIR between municipalities were observed. In bivariate analysis, there appeared to be an association between municipalities' sSIR level and deprivation (p = 0.003).ConclusionThis study indicates that social factors should be considered when investigating HAIs by MDR bacteria. The case incidence heterogeneity between Andalusian municipalities might be explained by SDoH, but also possibly by under-notification. Automatising reporting may address the latter.

Risk Factors for Multidrug-Resistant Gram-Negative Bacteria Carriage upon Admission to the Intensive Care Unit

Multidrug-resistant Gram-negative bacteria (MDR-GNB) are microorganisms that have acquired resistance to extended-spectrum antibacterials and constitute an emerging threat to public health. Although carriers are an important source of transmission in healthcare settings, data about risk factors for MDR-GNB carriage are limited. Therefore, we aimed to identify risk factors for MDR-GNB carriage upon intensive care unit (ICU) admission and to optimise screening strategies. We conducted a case–control study. Admissions of adult patients to the ICU of a 1000-bed hospital during a year were included. We collected sociodemographic, clinical and microbiological data and performed a multivariate logistic regression model. A total of 1342 patients resulted in 1476 episodes of ICU admission, 91 (6.2%) of whom harboured MDR-GNB (38.5% women; median age 63.9 years). The most frequently isolated pathogens were Escherichia coli (57%) and Klebsiella pneumoniae (16%). The most frequent resistance mechanism was production of extended-spectrum beta lactamases. MDR-GNB carriage was associated to liver cirrhosis (OR 6.54, 95% CI 2.17–19.17), previous MDR-GNB carriage (OR 5.34, 1.55–16.60), digestive surgery (OR 2.83, 1.29–5.89) and length of hospital stay (OR 1.01 per day, 1.00–1.03). Several risk factors for MDR-GNB carriage upon admission to a high-risk setting were identified; the main comorbidity was liver cirrhosis.

Structural optimization of natural product nordihydroguaretic acid to discover novel analogues as AcrB inhibitors

Drug efflux pumps confer multidrug resistance to dangerous bacterial pathogens which makes these proteins promising drug targets. Herein, we present initial chemical optimization and structure-activity relationship (SAR) data around a previously described efflux pump inhibitor, nordihydroguaretic acid (NDGA). Four series of novel NDGA analogues that target Escherichia coli AcrB were designed, synthesized and evaluated for their ability to potentiate the activity of antibiotics, to inhibit AcrB-mediated substrate efflux and reduce off-target activity. Nine novel structures were identified that increased the efficacy of a panel of antibiotics, inhibited drug efflux and reduced permeabilization of the bacterial outer and inner membranes. Among them, WA7, WB11 and WD6 possessing broad-spectrum antimicrobial sensitization activity were identified as NDGA analogues with favorable properties as potential AcrB inhibitors, demonstrating moderate improvement in potency as compared to NDGA. In particular, WD6 was the most broadly active analogue improving the activity of all four classes of antibacterials tested.

Evaluation of essential oil obtained from Mentha×piperita L. against multidrug-resistant strains

Background

Bacterial multidrug resistance currently poses an increasingly serious threat, with important clinical consequences regarding treatment options. In 2017, the WHO released a global list of resistant bacteria, identifying multidrug-resistant (MDR) Gram-negative bacteria such as carbapenem-resistant Enterobacteriaceae, Pseudomonas aeruginosa or Acinetobacter baumannii, extended-spectrum cephalosporin-resistant Enterobacteriaceae as critical priorities for developing new strategies of treatment.

Purpose

The novelty presented in this study refers to the evaluation of the volatile oil obtained from the leaves of Mentha×piperita L., on MDR strains from hospitalized patients.

Material and methods

The essential oil was extracted by steam distillation and tested on six reference bacterial strains and also on the MDR strains collected from patients of the “Pius Brînzeu” Emergency Clinical County Hospital Timișoara. The in vitro antibacterial activity was evaluated by agar disk diffusion method and microdilution method.

Results

Testing the antibacterial activity of peppermint oil on both reference strains and isolated MDR strains from hospitalized patients demonstrated its bactericidal effect. Minimum inhibitory concentration (MIC) was lower (20 mg/mL) for Staphylococcus aureus, Escherichia coli and Proteus mirabilis and higher (40 mg/mL) for Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii strains. Minimum bactericidal concentration (MBC) was equal to MIC, with the exception of Pseudomonas aeruginosa strains, where MBC was the double of MIC.

Conclusion

The present study highlights the bactericidal activity of Mentha×piperita L. essential oil on all tested MDR or extensively drug-resistant Gram-positive and Gram-negative strains of Staphylococcus aureus, Escherichia coli, Klebsiellapneumoniae, Proteus mirabilis, Pseudomonas aeruginosa and Acinetobacter baumannii. This oil may be a therapeutic option in the near future for many infectious diseases produced by MDR bacteria.

Multidrug-Resistant Gram-Negative Bacilli: A Retrospective Study of Trends in a Tertiary Healthcare Unit

Background and objective: Bacterial multidrug resistance is particularly common in Gram-negative bacilli (GNB), with important clinical consequences regarding their spread and treatment options. The aim of this study was to investigate the trend of multidrug-resistant GNB (MDR-GNB) in high-risk hospital departments, between 2000–2015, in intervals of five years, with the intention of improving antibiotic therapy policies and optimising preventive and control practices. Materials and methods: This is an observational, retrospective study performed in three departments of the most important tertiary healthcare unit in the southwestern part of Romania: the Intensive Care Unit (ICU), the General Surgery Department (GSD), and the Nutrition and Metabolic Diseases Department (NMDD). MDR was defined as acquired resistance to at least one agent in three or more antimicrobial categories. Trends over time were determined by the Cochran–Armitage trend test and linear regression. Results: During the study period, a total of 2531 strains of MDR-GNB were isolated in 1999 patients: 9.20% in 2000, 18.61% in 2005, 37.02% in 2010, and 35.17% in 2015. The most significant increasing trend was recorded in the ICU (gradient = 7.63, R² = 0.842, p < 0.001). The most common MDR-GNB in the ICU was isolated from bronchoalveolar aspiration samples. Concerning the proportion of different species, most of the changes were recorded in the ICU, where a statistically significant increasing trend was observed for Proteus mirabilis (gradient = 2.62, R² = 0.558, p < 0.001) and Acinetobacter baumannii (gradient = 2.25, R² = 0.491, p < 0.001). Analysis of the incidence of the main resistance phenotypes proportion identified a statistically significant increase in carbapenem resistance in the ICU (Gradient = 8.27, R² = 0.866, p < 0.001), and an increased proportion of aminoglycoside-resistant strains in all three departments, but more importantly in the ICU and GSD. Conclusion: A statistically significant increasing trend was observed in all three departments; the most significant one was recorded in the ICU, where after 2010, carbapenem-resistant strains were isolated.

Proton pump inhibitor use as a risk factor for Enterobacteriaceal infection: a case-control study

BACKGROUND

Gastric acid suppressants increase the risk of gastroenteritis by allowing ingested pathogens to survive passage through the stomach. It is not known whether the same mechanism affects transmission of Enterobacteriaceae. A case-control study was undertaken to answer this question.

AIM

To determine whether use of proton pump inhibitors (PPIs) increases the risk of infection with Enterobacteriaceae in hospital patients.

METHODS

Retrospective case-control study in a teaching hospital in South West England. Cases were 126 patients infected with extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae between April 2014 and March 2015. Use of PPIs, H2 receptor antagonists or antacids at the time of admission or in the preceding six months was compared with 126 demographically matched controls infected with non-ESBL-producing Enterobacteriaceae and 126 uninfected controls, matched by primary diagnosis.

FINDINGS

Sixty-six of 126 ESBL cases, 62 of 126 non-ESBL controls and 34 of 126 uninfected controls were prescribed PPIs on or within six months of admission. Multi-variable logistic regression analysis gave an odds ratio of 3.37 [95% confidence interval (CI) 1.84-6.18] for PPI exposure vs uninfected controls and 1.15 (95% CI 0.68-1.95) for ESBL infection vs non-ESBL infection. H2 receptor antagonists and antacids were not significantly associated with infection.

CONCLUSION

PPI exposure within the previous six months is significantly associated with infection with both ESBL- and non-ESBL-producing bacteria. Reducing inappropriate use of PPIs may be a novel way to reduce transmission, which might reduce antibiotic use and help control antimicrobial resistance.

Multiple entry pathways within the efflux transporter AcrB contribute to multidrug recognition

AcrB is the major multidrug exporter in Escherichia coli. Although several substrate-entrances have been identified, the specificity of these various transport paths remains unclear. Here we present evidence for a substrate channel (channel 3)  from the central cavity of the AcrB trimer, which is connected directly to the deep pocket without first passing the switch-loop and the proximal pocket . Planar aromatic cations, such as ethidium, prefer channel 3 to channels 1 and 2. The efflux through channel 3 increases by targeted mutations and is not in competition with the export of drugs such as minocycline and erythromycin through channels 1 and 2. A switch-loop mutant, in which the pathway from the proximal to the deep pocket is hindered, can export only channel 3-utilizing drugs. The usage of multiple entrances thus contributes to the recognition and transport of a wide range of drugs with different physicochemical properties.

Multidrug transporters possess several drug binding sites. Here the authors describe a transport path specific for planar aromatic cations in the E. coli multi-drug transporter AcrB.