Antimicrobial-resistant pathogens in intensive care units in Canada: results of the Canadian National Intensive Care Unit (CAN-ICU) study, 2005-2006

Enhancing outer membrane permeability of tetracycline antibiotics in P. aeruginosa using TOB-CIP conjugates

Pseudomonas aeruginosa is an opportunistic critical 'priority 1' Gram-negative bacterium that poses a severe threat to public healthcare due to rising antibiotic resistance. Particularly, low membrane permeability and overexpression of efflux pumps in P. aeruginosa lead to intrinsic resistance that compromises the antibacterial activity of antibiotics. The broad-spectrum antibiotics class, tetracyclines, are rarely used to treat P. aeruginosa infections. In the present study, we describe a series of tobramycin-ciprofloxacin (TOB-CIP) conjugates in which the carboxylic acid of ciprofloxacin is linked to the aminoglycoside tobramycin using various tethers thereby generating a cationic amphiphile. The emerging amphiphilic conjugates potentiate tetracycline antibiotics including minocycline, doxycycline, tigecycline, and eravacycline against multidrug-resistant P. aeruginosa isolates. The structure-activity relationship investigation indicates that the flexible hydrophobic C12 carbon-chain linker in TOB-CIP conjugate 1a is an optimal potentiator of tetracyclines against tetracycline-resistant and -susceptible strains of P. aeruginosa. Furthermore, conjugate 1a consistently synergized with the 3rd generation tetracycline, eravacycline, in P. aeruginosa PAO1 in the presence of up to 25% fetal bovine serum (FBS).

Multidrug-Resistant Bacterial Infections in Pediatric Patients Hospitalized at King Abdulaziz University Hospital, Jeddah, Western Saudi Arabia

Multidrug-resistant bacterial infections (MDRIs) constitute a major global threat due to increased patient morbidity/mortality and hospital stay/healthcare costs. A few studies from KSA, including our locality, addressed antimicrobial resistance in pediatric patients. This study was performed to recognize the incidence and clinical/microbiologic features of MDRIs in hospitalized pediatric patients. A retrospective cross-sectional study included pediatric patients < 18 years, admitted to King Abdulaziz University Hospital, between October 2021 and November 2022, with confirmed positive cultures of bacteria isolated from blood/body fluids. Patients' medical files provided the required data. MDR organisms (MDROs) were identified in 12.8% of the total cultures. The incidence of MDRIs was relatively high, as it was detected in 42% of patients and in 54.3% of positive bacterial cultures especially among critically ill patients admitted to the NICU and PICU. Pneumonia/ventilator-associated pneumonia was the main type of infection in 37.8% of patients with MDROs. Klebsiella pneumoniae was the most common significantly isolated MDRO in 39.5% of MDR cultures. Interestingly, a low weight for (no need for their as terminology weight for age is standard and well-known) was the only significant risk factor associated with MDROs (p = 0.02). Mortality was significantly higher (p = 0.001) in patients with MDROs (32.4%) than in patients without MDROs (3.9%). Patients who died including 85.7% of patients with MDROs had significantly longer durations of admission, more cultures, and utilized a larger number of antibiotics than the surviving patients (p = 0.02, p = 0.01, p = 0.04, respectively). This study provided a comprehensive update on the seriously alarming problem of MDROs, and its impacts on pediatric patients. The detected findings are crucial and are a helpful guide to decid for implementing effective strategies to mitigate MDROs.

Application of tobramycin benzyl ether as an antibiotic adjuvant capable of sensitizing multidrug-resistant Gram-negative bacteria to rifampicin

The emergence of aminoglycoside resistance has prompted the development of amphiphilic aminoglycoside derivatives which target bacterial membranes. Tobramycin and nebramine ether derivatives initially designed for this purpose were optimized and screened for their potential application as outer membrane (OM) permeabilizing adjuvants. Structure-activity relationship (SAR) studies revealed that the tobramycin benzyl ether was the most optimal OM permeabilizer, capable of potentiating rifampicin, novobiocin, vancomycin, minocycline, and doxycycline against Gram-negative bacteria. The innovative use of this compound as an adjuvant is highlighted by its ability to sensitize multidrug-resistant (MDR) Gram-negative bacteria to rifampicin and restore the susceptibility of MDR Escherichia coli to minocycline.

Guanidinylated Amphiphilic Tobramycin Derivatives Synergize with β-Lactam/β-Lactamase Inhibitor Combinations against Pseudomonas aeruginosa

Carbapenem-resistant Pseudomonas aeruginosa (P. aeruginosa) was designated as a critical priority pathogen by the World Health Organization for which new therapeutic solutions are required. With the rapid dissemination of β-lactamases in P. aeruginosa, β-lactam (BL) antibiotics are used in conjunction with β-lactamase inhibitors (BLI). The effectiveness of the BL/BLI combination could be further enhanced with the inclusion of an outer membrane (OM) permeabilizer, such as aminoglycosides and aminoglycoside-based adjuvants. Thus, the development of seven tobramycin derivatives reported herein focused on improving OM permeabilizing capabilities and reducing associated toxicity. The structure-activity relationship studies emphasized the effects of the nature of the cationic group; the number of polar head groups and positive charges; and flexibility, length, and steric bulk of the hydrophobic moiety. The optimized guanidinylated tobramycin-biphenyl derivative was noncytotoxic and demonstrated the ability to potentiate ceftazidime and aztreonam monotherapy and in dual combinations with avibactam against multidrug-resistant (MDR) and β-lactamase harboring isolates of P. aeruginosa. The triple combination of ceftazidime/avibactam plus guanidinylated tobramycin-biphenyl resulted in rapid bactericidal activity within 4-8 h of treatment, demonstrating the potential application of these guanidinylated amphiphilic tobramycin derivatives in augmenting BL/BLI combinations.

Trimeric Tobramycin/Nebramine Synergizes β-Lactam Antibiotics against Pseudomonas aeruginosa

β-Lactam antibiotics remain one of the most effective therapeutics to treat infections caused by Gram-negative bacteria (GNB). However, since ancient times, bacteria have developed multiple resistance mechanisms toward this class of antibiotics including overexpression of β-lactamases, suppression of porins, outer membrane impermeability, overexpression of efflux pumps, and target modifications. To cope with these challenges and to extend the lifetime of existing β-lactam antibiotics, β-lactamase inhibitors are combined with β-lactam antibiotics to prevent antibiotic inactivation by β-lactamases. The combination therapy of an outer membrane permeabilizer with β-lactam antibiotics is an alternative approach to overcoming bacterial resistance of β-lactams in GNB. This approach is of particular interest for pathogens with highly impermeable outer membranes like Pseudomonas aeruginosa. Previous studies have shown that outer membrane permeabilizers can be designed by linking tobramycin and nebramine units together in the form of dimers or chimeras. In this study, we developed trimeric tobramycin and nebramine-based outer membrane permeabilizers presented on a central 1,3,5-triazine framework. The resultant trimers are capable of potentiating outer membrane-impermeable antibiotics but also β-lactams and β-lactam/β-lactamase inhibitor combinations against resistant P. aeruginosa isolates. Furthermore, the microbiological susceptibility breakpoints of ceftazidime, aztreonam, and imipenem were reached by a triple combination consisting of an outer-membrane permeabilizer/β-lactam/β-lactamase inhibitor in β-lactam-resistant P. aeruginosa isolates. Overall, our results indicate that trimeric tobramycins/nebramines can rescue clinically approved β-lactams and β-lactam/β-lactamase inhibitor combinations from resistance.

Exploring Antibiotic-Potentiating Effects of Tobramycin-Deferiprone Conjugates in Pseudomonas aeruginosa

Metal ions, including Fe3+, affect the target site binding of some antibiotics and control the porin- and siderophore-mediated uptake of antibiotics. Amphiphilic tobramycins are an emerging class of antibiotic potentiators capable of synergizing with multiple classes of antibiotics against Gram-negative bacteria, including Pseudomonas aeruginosa. To study how the antibiotic-potentiating effect of amphiphilic tobramycins is affected by the presence of intermolecular iron chelators, we conjugated the FDA-approved iron chelator deferiprone (DEF) to tobramycin (TOB). Three TOB-DEF conjugates differing in the length of the carbon tether were prepared and tested for antibacterial activity and synergistic relationships with a panel of antibiotics against clinical isolates of P. aeruginosa. While all TOB-DEF conjugates were inactive against P. aeruginosa, the TOB-DEF conjugates strongly synergized with outer-membrane-impermeable antibiotics, such as novobiocin and rifampicin. Among the three TOB-DEF conjugates, 1c containing a C12 tether showed a remarkable and selective potentiating effect to improve the susceptibility of multidrug-resistant P. aeruginosa isolates to tetracyclines when compared with other antibiotics. However, the antibacterial activity and antibiotic-potentiating effect of the optimized conjugate was not enhanced under iron-depleted conditions, indicating that the function of the antibiotic potentiator is not affected by the Fe3+ concentration.

Chimeric Tobramycin-Based Adjuvant TOB-TOB-CIP Potentiates Fluoroquinolone and β-Lactam Antibiotics against Multidrug-Resistant Pseudomonas aeruginosa

According to the World Health Organization, antibiotic resistance is a global health threat. Of particular importance are infections caused by multidrug-resistant Gram-negative bacteria including Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa for which limited treatment options exist. Multiple and simultaneously occurring resistance mechanisms including outer membrane impermeability, overexpression of efflux pumps, antibiotic-modifying enzymes, and modification of genes and antibiotic targets have made antibiotic drug development more difficult against these pathogens. One strategy to cope with these challenges is the use of outer membrane permeabilizers that increase the intracellular concentration of antibiotics when used in combination. In some circumstances, this approach can rescue antibiotics from resistance or repurpose currently marketed antibiotics. Tobramycin-based hybrid antibiotic adjuvants that combine two outer membrane-active components have been previously shown to potentiate antibiotics by facilitating transit through the outer membrane, resulting in increased antibiotic accumulation within the cell. Herein, we extended the concept of tobramycin-based hybrid antibiotic adjuvants to tobramycin-based chimeras by engineering up to three different membrane-active antibiotic warheads such as tobramycin, 1-(1-naphthylmethyl)-piperazine, ciprofloxacin, and cyclam into a central 1,3,5-triazine scaffold. Chimera 4 (TOB-TOB-CIP) consistently synergized with ciprofloxacin, levofloxacin, and moxifloxacin against wild-type and fluoroquinolone-resistant P. aeruginosa. Moreover, the susceptibility breakpoints of ceftazidime, aztreonam, and imipenem were reached using the triple combination of chimera 4 with ceftazidime/avibactam, aztreonam/avibactam, and imipenem/relebactam, respectively, against β-lactamase-harboring P. aeruginosa. Our findings demonstrate that tobramycin-based chimeras form a novel class of antibiotic potentiators capable of restoring the activity of antibiotics against P. aeruginosa.

Guanidinylated Polymyxins as Outer Membrane Permeabilizers Capable of Potentiating Rifampicin, Erythromycin, Ceftazidime and Aztreonam against Gram-Negative Bacteria

Polymyxins are considered a last-line treatment against infections caused by multidrug-resistant (MDR) Gram-negative bacteria. In addition to their use as a potent antibiotic, polymyxins have also been utilized as outer membrane (OM) permeabilizers, capable of augmenting the activity of a partner antibiotic. Several polymyxin derivatives have been developed accordingly, with the objective of mitigating associated nephrotoxicity. The conversion of polymyxins to guanidinylated derivatives, whereby the L-γ-diaminobutyric acid (Dab) amines are substituted with guanidines, are described herein. The resulting guanidinylated colistin and polymyxin B (PMB) exhibited reduced antibacterial activity but preserved OM permeabilizing properties that allowed potentiation of several antibiotic classes. Rifampicin, erythromycin, ceftazidime and aztreonam were particularly potentiated against clinically relevant MDR Gram-negative bacteria. The potentiating effects of guanidinylated polymyxins with ceftazidime or aztreonam were further enhanced by adding the β-lactamase inhibitor avibactam.

Antimicrobial use and mortality among intensive care unit patients with bloodstream infections: implications for stewardship programs

Background

Bloodstream infections (BSIs) are one of the most critical illnesses requiring intensive care unit (ICU) admission. Antimicrobial therapy (AMT) is one of the vital management strategies for the treatment of BSIs; it should be chosen appropriately to reduce mortality.

Objectives

This is the first study to investigate the types of antimicrobial agents administered in the ICU setting and the predictor variables associated with mortality.

Methods

This retrospective study was conducted at King Abdullah University Hospital (KAUH). All hospitalized patients admitted to the ICU and received at least one antimicrobial agent over 3 years period (January 1, 2017, to December 31, 2019) were included in the study. Electronic patients' medical records were used to collect patients' demographic and clinical characteristics, patient general health status, events that occurred during hospitalization, and events after obtaining the blood culture. Descriptive analysis was done to identify the types of antimicrobials used and the distribution of the microorganisms among the study participants. The susceptibility test of the bloodstream culture was checked for each patient. Moreover, crude mortality and its associated factors were investigated.

Results

A total of 1051 patients were enrolled in the study, where 650 patients (61.84%) were treated with three or more antimicrobial agents. The most frequent antimicrobials used were piperacillin/tazobactam followed by teicoplanin, meropenem, and levofloxacin. About half of the patients died within 30-days of BSI, which was associated with several factors including advanced age, presence of co-morbidities, nosocomial infections or healthcare-associated infections, length of ICU stay, respiratory tract infections, receiving vasopressor during the hospital stay, concurrent positive culture other than blood with BSI, receiving combination antimicrobial therapy, those who were complicated with septic shock or renal failure, receiving total parenteral protein (TPN) nutrition, and inappropriate empiric antimicrobial therapy.

Conclusion

In conclusion, the administration of the antimicrobials among ICU patients was highly based on a combination of three or more agents covering a broad spectrum of microorganisms. The mortality rate was high among patients which were associated with inappropriate empirical therapy. Therefore, the antimicrobial stewardship (ASP) protocol has to be evaluated in the hospital for ICU patients. Moreover, we suggest recommending that hospital policies should apply the ASP protocol, infection control, implement the antimicrobial de-escalation protocol, and do best controlling on the co-morbid conditions, especially for ages 65 years or more to reduce the mortality rate in the ICU.

A Data-Driven Framework for Identifying Intensive Care Unit Admissions Colonized With Multidrug-Resistant Organisms

Background

The rising prevalence of multi-drug resistant organisms (MDROs), such as Methicillin-resistant Staphylococcus aureus (MRSA), Vancomycin-resistant Enterococci (VRE), and Carbapenem-resistant Enterobacteriaceae (CRE), is an increasing concern in healthcare settings.

Materials and Methods

Leveraging data from electronic healthcare records and a unique MDRO universal screening program, we developed a data-driven modeling framework to predict MRSA, VRE, and CRE colonization upon intensive care unit (ICU) admission, and identified the associated socio-demographic and clinical factors using logistic regression (LR), random forest (RF), and XGBoost algorithms. We performed threshold optimization for converting predicted probabilities into binary predictions and identified the cut-off maximizing the sum of sensitivity and specificity.

Results

Four thousand six hundred seventy ICU admissions (3,958 patients) were examined. MDRO colonization rate was 17.59% (13.03% VRE, 1.45% CRE, and 7.47% MRSA). Our study achieved the following sensitivity and specificity values with the best performing models, respectively: 80% and 66% for VRE with LR, 73% and 77% for CRE with XGBoost, 76% and 59% for MRSA with RF, and 82% and 83% for MDRO (i.e., VRE or CRE or MRSA) with RF. Further, we identified several predictors of MDRO colonization, including long-term care facility stay, current diagnosis of skin/subcutaneous tissue or infectious/parasitic disease, and recent isolation precaution procedures before ICU admission.

Conclusion

Our data-driven modeling framework can be used as a clinical decision support tool for timely predictions, characterization and identification of high-risk patients, and selective and timely use of infection control measures in ICUs.

Effects of Lysine N-ζ-Methylation in Ultrashort Tetrabasic Lipopeptides (UTBLPs) on the Potentiation of Rifampicin, Novobiocin, and Niclosamide in Gram-Negative Bacteria

Outer membrane (OM) drug impermeability typically associated with a molecular weight above 600 Da and high hydrophobicity prevents accumulation of many antibiotics in Gram-negative bacteria (GNB). Previous studies have shown that ultrashort tetrabasic lipopeptides (UTBLPs) containing multiple lysine residues potentiate Gram-positive bacteria (GPB)-selective antibiotics in GNB by enhancing OM permeability. However, there is no available information on how N-substitution at the ζ-position of lysine in UTBLPs affects antibiotic potentiation in GNB. To study these effects, we prepared a series of branched and linear UTBLPs that differ in the degree of N-ζ-methylation and studied their potentiating effects with GPB-selective antibiotics including rifampicin, novobiocin, niclosamide, and chloramphenicol against wild-type and multidrug-resistant GNB isolates. Our results show that increasing N-ζ-methylation reduces or abolishes the potentiating effects of UTBLPs with rifampicin, novobiocin, and niclosamide against GNB. No trend was observed with chloramphenicol that is largely affected by efflux. We were unable to observe a correlation between the strength of the antibiotic potentiating effect to the increase in fluorescence in the 1-N-phenylnaphthylamine (NPN) OM permeability assay suggesting that other factors besides OM permeability of NPN play a role in antibiotic potentiation. In conclusion, our study has elucidated crucial structure–activity relationships for the optimization of polybasic antibiotic potentiators in GNB.

Dioctanoyl Ultrashort Tetrabasic β-Peptides Sensitize Multidrug-Resistant Gram-Negative Bacteria to Novobiocin and Rifampicin

Recently reported peptidomimetics with increased resistance to trypsin were shown to sensitize priority multidrug-resistant (MDR) Gram-negative bacteria to novobiocin and rifampicin. To further optimize proteolytic stability, β-amino acid-containing derivatives of these compounds were prepared, resulting in three dioctanoyl ultrashort tetrabasic β-peptides (dUSTBβPs). The nonhemolytic dUSTBβP 3, comprised of three β³-homoarginine residues and two fatty acyl tails eight carbons long, enhanced the antibacterial activity of various antibiotics from different classes. Notably, compound 3 retained the ability to potentiate novobiocin and rifampicin in wild-type Gram-negative bacteria against MDR clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae. dUSTBβP 3 reduced the minimum inhibitory concentration of novobiocin and rifampicin below their interpretative susceptibility breakpoints. Furthermore, compound 3 exhibited improved in vitro stability (86.8 ± 3.7% remaining) relative to its α-amino acid-based counterpart (39.5 ± 7.4% remaining) after a 2 h incubation in human plasma.

A niclosamide-tobramycin hybrid adjuvant potentiates cefiderocol against P. aeruginosa

There is an urgent need for new therapies to overcome antimicrobial resistance (AMR) especially against Gram-negative bacilli (GNB). Multicomponent therapy combining antibiotics with enhancer molecules known as adjuvants is an emerging strategy to combat AMR. We have previously reported tobramycin-based adjuvants which are able to potentiate various antibiotics. In order to expand the repertoire of tobramycin hybrid adjuvants, a new hybrid containing niclosamide, an FDA approved anthelmintic which has recently demonstrated a variety of interesting biological effects, was synthesized. It was found that this conjugate can potentiate several antibiotics against multidrug-resistant GNB, including the recently approved siderophore cephalosporin cefiderocol. 8 μg ml^-1 of the niclosamide-tobramycin hybrid in combination therapy against a pandrug-resistant strain of P. aeruginosa was able to lower the cefiderocol MIC 32-fold, from 8 μg ml^-1 to 0.25 μg ml^-1 in iron-rich media where siderophore uptake is reduced. These results indicate that a niclosamide-tobramycin hybrid adjuvant can serve to potentiate a newly approved antibiotic.

Nosocomial sepsis and drug susceptibility pattern among patients admitted to adult intensive care unit of Ayder Comprehensive Specialized Hospital, Northern Ethiopia

OBJECTIVE

Developing nosocomial sepsis within intensive care unit (ICU) is associated with increased mortality, morbidity, and length of hospital stay. But information is scarce regarding nosocomial sepsis in intensive care units of Northern Ethiopia. Hence, this study aims to determine the incidence of nosocomial sepsis, associated factors, bacteriological profile, drug susceptibility pattern, and outcome among patients admitted to the adult ICU of Ayder Comprehensive Specialized Hospital (ACSH), which is the largest tertiary hospital in Northern Ethiopia.

METHOD

Facility-based longitudinal study was conducted by following 278 patients who were admitted for more than 48 h to adult ICU of ACSH, from October 2016 to October 2017. Data were collected from charts, electronic medical records, and microbiology registration book using a checklist. The collected data were subjected to descriptive statistics and multivariable logistic regression using SPSS version 25. Statistical significance was declared at p < 0.05.

RESULT

Of all the patients, 60 (21.6%) of them acquired nosocomial sepsis. The risk of mortality was about two times higher among adult ICU patients who acquired nosocomial sepsis (RR = 2.2; 95% CI of RR = 1.3-3.5; p = 0.003). The odds of acquiring nosocomial sepsis among those who were on a mechanical ventilator (MV) and stayed more than a week were 5.7 and 9.3 times higher, respectively, than their corresponding counterparts. Among 48 isolates, Klebsiella was the most common pathogen. The isolates had a broad antibiotic resistance pattern for cephalosporins, penicillins, and methicillin.

CONCLUSION

The incidence of nosocomial sepsis in the adult ICU patients of ACSH was higher when compared to the incidence reported from some African and Asian countries. Mortality was higher among patients who acquired nosocomial sepsis. Use of MV and longer length of ICU stay were the significant predictors of nosocomial sepsis. The isolates were resistant to several antibiotics. Therefore, strict application of infection prevention strategies and appropriate use of antibiotics is so crucial. As well, priority should be given to patients who develop nosocomial sepsis in ICU.

Early β-lactam concentrations and infectious complications after lung transplantation

Antibiotic underdosing in prophylactic antibiotic regimes after lung transplantation (LTx) can increase the risk of infection. We aimed to study whether β-lactam concentrations achieved desirable pharmacodynamic targets in the early phase after LTx and the association between drug concentrations and the development of early infections or the acquisition of multidrug-resistant (MDR) strains. We reviewed patients in whom broad-spectrum β-lactam levels were measured after LTx during antibiotic prophylaxis. β-Lactam concentrations were considered "insufficient" if drug levels remained below four times the clinical breakpoint of the minimal inhibitory concentration for Pseudomonas aeruginosa. The primary outcome was the occurrence of an infection and/or acquisition of MDR pathogens in the first 14 days after transplantation. A total of 70 patients were included. "Insufficient" drug concentrations were found in 40% of patients. In 27% of patients, an early MDR pathogen was identified and 49% patients were diagnosed with an early posttransplant infection. Patients with "insufficient" drug concentrations acquired more frequently MDR bacteria and/or developed an infection than others (22/28, 79% vs. 20/42, 48% - p = .01). β-Lactam levels were often found to be below the desired drug targets in the early phase after transplantation and may be associated with the occurrence of early infectious complications.

A Novel Device-Integrated Drug Delivery System for Local Inhibition of Urinary Tract Infection

Background: Catheter-associated urinary tract infection (CAUTI) is a frequent community-acquired infection and the most common nosocomial infection. Here, we developed a novel antimicrobial catheter concept that utilizes a silicone-based interpenetrating polymer network (IPN) as balloon material to facilitate a topical slow-release prophylaxis of antibacterial agents across the balloon to the urinary bladder.

Methods: The balloon material was achieved by modifying low shore hardness silicone tubes with a hydrogel interpenetrating polymer in supercritical CO₂ using the sequential method. Release properties and antibacterial efficacy of the IPN balloon treatment concept was investigated in vitro and in a porcine CAUTI model developed for the study. In the latter, Bactiguard Infection Protection (BIP) Foley catheters were also assessed to enable benchmark with the traditional antimicrobial coating principle.

Results: Uropathogenic Escherichia coli was undetectable in urinary bladders and on retrieved catheters in the IPN treatment group as compared to control that revealed significant bacteriuria (>10⁵ colony forming units/ml) as well as catheter-associated biofilm. The BIP catheters failed to prevent E. coli colonization of the bladder but significantly reduced catheter biofilm formation compared to the control.

Conclusion: The IPN-catheter concept provides a novel, promising delivery route for local treatment in the urinary tract.

Development of Phenalenone-Triazolium Salt Derivatives for aPDT: Synthesis and Antibacterial Screening

The increasing number of hospital-acquired infections demand the development of innovative antimicrobial treatments. Antimicrobial photodynamic therapy (aPDT) is a versatile technique which relies on the production of reactive oxygen species (ROS) generated by light-irradiated photosensitizers (PS) in the presence of oxygen (O₂). 1H-Phenalen-1-one is a very efficient photosensitizer known for its high singlet oxygen quantum yield and its antimicrobial potential in aPDT when covalently bound to quaternary ammonium groups. Triazolium salts are stable aromatic quaternary ammonium salts that recently appeared as interesting moieties endowed with antimicrobial activities. The coupling between phenalenone and triazolium groups bearing various substituents was realized by copper-catalyzed azide-alkyne cycloaddition followed by alkylation with methyl iodide or 2-(bromomethyl)-1H-phenalen-1-one. As expected, most of the compounds retained the initial singlet oxygen quantum yield, close to unity. Minimum inhibitory concentrations (MIC) of 14 new phenalenone-triazolium salt derivatives and 2 phenalenone-triazole derivatives were determined against 6 bacterial strains (Gram-negatives and Gram-positives species). Most of these PS showed significant photoinactivation activities, the strongest effects being observed against Gram-positive strains with as low as submicromolar MIC values.

Occurrence and Phenotypic Characterization of Multidrug-Resistant Bacterial Pathogens Isolated from Patients in a Public Hospital in Mogadishu, Somalia

Purpose

This study reports a cross-sectional investigation to determine the antimicrobial resistance pattern of the common bacterial contaminants isolated from hospitalized patients in Mogadishu, Somalia.

Materials and Methods

A total of 328 clinical samples comprising urine, blood, vaginal swab, pus aspirates, and stool were collected from a public hospital located in Mogadishu the capital city of Somalia between October 2019 to March 2020. The isolation and biochemical characterization of the bacterial isolates were performed using the conventional culture and biochemical assay tests. Similarly, antimicrobial susceptibility was determined using the Kirby–Bauer disk diffusion.

Results

A total of 275 pathogenic bacteria that include Staphylococcus aureus, Escherichia coli, Pseudomonas aeroginosa, Proteus vulgare, Klebsiella pneumonia, and Salmonella spp. were detected with an overall detection rate of 78.4% (257/328). Among the bacterial pathogens isolated from clinical specimens, 152 (46.3%) were Staphylococcus aureus, 60 (18.3%) were E. coli, 10 (3.1%) Proteus vulgaris, 6 (1.8%) Klebsiella pneumonia, and 1 (0.3%) isolate was found to be Salmonella sp. The antimicrobial susceptibility assay revealed variable resistance pattern with clindamycin (40%), ampicillin (27%), vancomycin (26%), levofloxacin (23%), amoxicillin (20%), ciprofloxacin (18%) and nitrofurantoin (12%) showing the highest rate of resistance. Moreover, evaluation of multidrug resistance showed that Staphylococcus aureus had the highest multidrug resistance rate, with 19 isolates showing resistance to more than two drugs, followed by E. coli with three isolates. In contrast, each of Proteus vulgare, Salmonella sp. and Klebsiella pneumonia had one isolate each that exhibited multidrug resistance characteristics.

Conclusion

The findings of this study showed the occurrence of a number antimicrobial-resistant bacterial pathogens whose prevalence varies with age and sex. Therefore, there is a need for comprehensive antimicrobial profiling of bacterial isolates during the management of patients in the hospital.

Magnitude of Multidrug Resistance among Bacterial Isolates from Surgical Site Infections in Two National Referral Hospitals in Asmara, Eritrea

Background

The World Health Organization has emphasized the importance of understanding the epidemiology of MDR organisms from a local standpoint. Here, we report on a spectrum of bacteria associated with surgical site infections in two referral hospitals in Eritrea and the associated antibiotic susceptibility patterns.

Methods

This survey was conducted between February and May 2017. A total of 83 patients receiving treatment for various surgical conditions were included. Swabs from infected surgical sites were collected using Levine technique and processed using standard microbiological procedures. In vitro antimicrobial susceptibility testing was performed on Mueller–Hinton Agar by the Kirby-Bauer disk diffusion method following Clinical and Laboratory Standards Institute guidelines. The data were analyzed using SPSS version 20.

Results

A total of 116 isolates were recovered from 83 patients. In total, 67 (58%) and 49 (42%) of the isolates were Gram-positive and Gram-negative bacteria, respectively. The most common isolates included Citrobacter spp., Klebsiella spp., Escherichia coli, Proteus spp., Pseudomonas aeruginosa, Salmonella spp., Enterobacter spp., and Acinetobacter spp. In contrast, Staphylococcus aureus, CONS, and Streptococcus viridians were the predominant Gram-positive isolates. All the Staphylococcus aureus isolates were resistant to penicillin. MRSA phenotype was observed in 70% of the isolates. Vancomycin, clindamycin, and erythromycin resistance were observed in 60%, 25%, and 25% of the isolates, respectively. Furthermore, a high proportion (91%) of the Gram-negative bacteria were resistant to ampicillin and 100% of the Pseudomonas aeruginosa and Escherichia coli isolates were resistant to >5 of the tested antibiotics. The two Acinetobacter isolates were resistant to >7 antimicrobial agents. We also noted that 4 (60%) of the Klebsiella isolates were resistant to >5 antimicrobial agents. Possible pan-drug-resistant (PDR) strains were also isolated.

Conclusion

Due to the high frequency of MDR isolates reported in this study, the development and implementation of suitable infection control policies and guidelines is imperative.

Multidrug-Resistant and Extensively Drug-Resistant Enterobacteriaceae: Prevalence, Treatments, and Outcomes - A Retrospective Cohort Study

Background

Drug-resistant gram-negative bacteria (GNB) are a global public health threat, especially in intensive care units (ICU). This study explored the prevalence of drug-resistant Enterobacteriaceae infections in an ICU in Saudi Arabia. The appropriateness of the antibiotic therapies used and their ability to improve the clinical outcomes were also assessed.

Methods

A retrospective study was conducted from 2015 to 2018 in the different ICUs of a tertiary-care hospital in Saudi Arabia. Positive cultures for multidrug-resistant (MDR), extensively drug-resistant (XDR), and pandrug-resistant (PDR) Enterobacteriaceae, including Klebsiella pneumoniae, Escherichia coli, and Enterobacter sp., were included. The primary outcomes involved microbiological cure and 30 days in-hospital mortality rate, while the secondary outcome included the length of hospital stay (LOS). Regression models were used to assess the relationship between appropriateness of the antibiotic therapy and clinical outcomes.

Results

Of the 227 Enterobacteriaceae cultures included in this study, 60% were either MDR (n= 130) or XDR (n= 8) infections; no PDR Enterobacteriaceae cultures were identified. Majority of the patients were female (54%), and the average age was 60.1 ± 17.7 years. MDR/XDR cultures primarily comprised E. coli (51.4%), followed by K. pneumoniae (33%) and Enterobacter sp. (16%). Most commonly used antibiotics were piperacillin/tazobactam (53%), carbapenems (47%), and cephalosporins (21.3%). Antibiotic therapy was considered appropriate in only 85 of 138 (61.59%) patients. Microbiological cure rate was achieved in 40% of the cases, and in-hospital death rate was 84%. The average LOS was 27 days. Appropriateness of the antibiotic therapy prescribed could not predict any of the study outcomes.

Conclusion

The study revealed a high prevalence of drug-resistant Enterobacteriaceae infections, which were associated with a high mortality rate. Therefore, it is essential to assess the effectiveness of antimicrobial stewardship program and infection prevention and control practices, particularly in critically ill patients.

Knowledge, perceptions and experiences of nurses in antimicrobial optimization or stewardship in the intensive care unit

There is an urgent and recognized need for an interprofessional collaborative approach to support global action in addressing antimicrobial resistance (AMR). Antimicrobial stewardship (AMS) refers to systematic approaches for antimicrobial optimization within healthcare organizations. In areas with high antimicrobial utilization such as intensive care units (ICUs), specific roles for nurses in AMS are not clearly defined. This review aimed to identify and to critically evaluate primary studies that examined knowledge, perspectives and experiences of nurses associated with antimicrobial use and optimization in ICUs. A systematic search of Medline, CINAHL, PsychINFO, EMBASE, PubMed, SCOPUS, Cochrane Library and Web of Science databases for primary studies published from 1^st January 2000 to 20^th March 2020 was performed. A convergent synthesis design was used to synthesize quantitative and qualitative data. Of the 898 studies initially screened, 26 were included. Most (18/26) studies were quantitative. All qualitative studies (6/26) were of high methodological quality. Studies where interventions were used (10/26) identified significant potential for ICU nurses to reduce antimicrobial use, time-to-antibiotic administration, and error rates. Barriers to nursing engagement included knowledge deficits in antimicrobial use, interprofessional dissonance and the culture of deference to physicians. Enhancing education, technology utilization, strong nursing leadership and robust organizational structures that support nurses were perceived as enablers to strengthen their roles in optimizing antimicrobial use. This review showed that nursing initiatives have significant potential to strengthen antimicrobial optimization in ICUs. Barriers and enablers to active engagement were identified.

Overcoming β-Lactam resistance in Pseudomonas aeruginosa using non-canonical tobramycin-based antibiotic adjuvants

β-Lactam antibiotics have for long been a mainstay in antimicrobial chemotherapy. However, due to its ubiquitous usage, bacteria have evolved multiple concerted pathways to evade its actions, underscoring the complexity of resistance to this class of drug. Current strategies to mitigate this problem are geared towards developing inhibitors that can shield the β-lactam core from enzymatic hydrolysis. In reality, a combination of factors including porin loss, overexpressed efflux pumps, expression of β-lactamases, reduced outer membrane permeability, and target modifications are characteristics of phenotypes that are microbiologically resistant to β-lactam antibiotics, especially Pseudomonas aeruginosa. Herein, we describe a strategy that may simultaneously address multiple mechanisms of resistance to β-lactams. A triple combination with β-lactam/β-lactamase inhibitors offers better microbiological response against carbapenem-resistant P. aeruginosa than the current standard of care. The observed interactions are also unaffected by efflux pumps. We conclude that a multicomponent combination therapy may be the way forward in addressing the myriads of emerging therapy failure associated with β-lactam resistance.

Potentiation of β-lactam antibiotics and β-lactam/β-lactamase inhibitor combinations against MDR and XDR Pseudomonas aeruginosa using non-ribosomal tobramycin-cyclam conjugates

OBJECTIVES

To develop a multifunctional adjuvant molecule that can rescue β-lactam antibiotics and β-lactam/β-lactamase inhibitor combinations from resistance in carbapenem-resistant Pseudomonas aeruginosa clinical isolates.

METHODS

Preparation of adjuvant was guided by structure-activity relationships, following standard protocols. Susceptibility and chequerboard studies were assessed using serial 2-fold dilution assays. Toxicity was evaluated against porcine erythrocytes, human embryonic kidney (HEK293) cells and liver carcinoma (HepG2) cells via MTS assay. Preliminary in vivo efficacy was evaluated using a Galleria mellonella infection model.

RESULTS

Conjugation of tobramycin and cyclam abrogates the ribosomal effects of tobramycin but confers a potent adjuvant property that restores full antibiotic activity of meropenem and aztreonam against carbapenem-resistant P. aeruginosa. Therapeutic levels of susceptibility, as determined by CLSI susceptibility breakpoints, were attained in several MDR clinical isolates, and time-kill assays revealed a synergistic dose-dependent pharmacodynamic relationship. A triple combination of the adjuvant with ceftazidime/avibactam (approved), aztreonam/avibactam (Phase III) and meropenem/avibactam enhances the efficacies of β-lactam/β-lactamase inhibitors against recalcitrant strains, suggesting rapid access of the combination to their periplasmic targets. The newly developed adjuvants, and their combinations, were non-haemolytic and non-cytotoxic, and preliminary in vivo evaluation in G. mellonella suggests therapeutic potential for the double and triple combinations.

CONCLUSIONS

Non-ribosomal tobramycin-cyclam conjugate mitigates the effect of OprD/OprF porin loss in P. aeruginosa and potentiates β-lactam/β-lactamase inhibitors against carbapenem-resistant clinical isolates, highlighting the complexity of resistance to β-lactam antibiotics. Our strategy presents an avenue to further preserve the therapeutic utility of β-lactam antibiotics.

Examination of Blood and Tracheal Aspirate Culture Results in Intensive Care Patients: 5-year analysis

Objective:

Majority of nosocomial infections are seen in intensive care units (ICUs) and they course with higher rates of mortality, and morbidity rates. In this study, we aimed to investigate the distribution of microorganisms isolated from the tracheal aspirate and blood cultures of ICU hospitalized patients, and their antibiotic resistance profiles.

Method:

Tracheal aspirate and blood cultures sent from ICU patients were evaluated retrospectively between 2014-2018. Antimicrobial susceptibility tests were performed on microorganism cultures that were identified by conventional methods and using an automated system.

Results:

A total of 23.275 samples were accepted during the study period. The microorganisms isolated from tracheal aspirate cultures were Gram-negative (89.7%), Gram-positive (9.3%) and yeasts (1%). The most common Gram (-) microorganisms were A.baumannii (%25.7). The rates of meropenem resistance were documented as 98.3% for A.baumannii in 2014, 95.7% in 2018, 69.2% for P.aeruginosa. in 2014, and 35.6% in 2018, 45.55 for K.pneumoniae in 2014, and 5.8% in 2018 and 8% for E.coli in 2014, and 2% in 2018. The rates of methicillin resistance in S.aureus were documented as 28.0% in 2018, and 67.7% in 2015. The rates of penicillin resistance for S. pneumonia was documented as 76.8% in 2018, and 13.4% in 2015. The microorganisms isolated from blood culture were Gram (-) (31.4%), Gram (+) (57.9%) and yeasts (10.6%). The most frequently isolated Gram (-) bacteria were K.pneumonia (9.3%) and A.baumannii (8.8%). The rates of meropenem resistance were documented as 97.3% for A.baumannii. in 2014 and 79.2% in 2018, as 76.9% for K.pneumoniae in 2014 and 37.3% in 2018 and 79.2% for P.aeruginosa in 2014 and 26.1% in 2018. The artes of methicillin resistance were documented as 89.2% in 2018, and 78.5% for CNS in 2015, and 42.6% in 2018 while it was 92.4% for S. aureus in 2015

Conclusions:

Our study showcased a drop throughout the year in rates of carbapenem resistance against Gram (-) microorganisms and methicillin resistance in S.aureus. However, the persistently high carbapanem resistance in A.baumannii isolates demonstrates the crucial need to continue with infection control measures.

Dilipid Ultrashort Tetrabasic Peptidomimetics Potentiate Novobiocin and Rifampicin Against Multidrug-Resistant Gram-Negative Bacteria

The development of new antibacterial agents and therapeutic approaches is of high importance to address the global problem of antibiotic resistance. Although antimicrobial peptides are known to synergize with certain antibiotics, their clinical application is limited by their systemic toxicity, protease instability, and high production cost. To overcome these problems, nine dilipid ultrashort tetrabasic peptidomimetics (dUSTBPs) were prepared consisting of three basic amino acids separated by a molecular scaffold, bis(3-aminopropyl)glycine, and were ligated to two fatty acids. Several nonhemolytic dUSTBPs were shown to enhance the activity of several antibiotics against pathogenic Gram-negative bacteria. More importantly, dUSTBP 8, consisting of three l-arginine units and a dilipid of 8 carbons long, potentiated novobiocin and rifampicin consistently against multidrug-resistant (MDR) clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae. Preliminary studies suggested that dUSTBPs were likely to potentiate antibiotics through outer membrane permeabilization and/or disruption of active efflux and that dUSTBP 8 exhibited enhanced resistance to trypsin in comparison to the previously described di-C₉-KKKK-NH₂ antibiotic potentiator. The antibacterial activity of rifampicin and novobiocin was enhanced by dUSTBP 8 comparable to other known outer membrane permeabilizing potentiators including the gold standard polymyxin B nonapeptide. Our results indicate that ultrashort tetrabasic peptidomimetics are potent adjuvants that repurpose novobiocin and rifampicin as potent agents against priority MDR Gram-negative pathogens.

Antimicrobial-resistant pathogens in Canadian ICUs: results of the CANWARD 2007 to 2016 study

OBJECTIVES

To describe the microbiology and antimicrobial resistance patterns of cultured samples acquired from Canadian ICUs.

METHODS

From 2007 to 2016, tertiary care centres from across Canada submitted 42938 bacterial/fungal isolates as part of the CANWARD surveillance study. Of these, 8130 (18.9%) were from patients on ICUs. Susceptibility testing guidelines and MIC interpretive criteria were defined by CLSI.

RESULTS

Of the 8130 pathogens collected in this study, 58.2%, 36.3%, 3.1% and 2.4% were from respiratory, blood, wound and urine specimens, respectively. The top five organisms collected from Canadian ICUs accounted for 55.4% of all isolates and included Staphylococcus aureus (21.5%), Pseudomonas aeruginosa (10.6%), Escherichia coli (10.4%), Streptococcus pneumoniae (6.5%) and Klebsiella pneumoniae (6.4%). MRSA accounted for 20.7% of S. aureus collected, with community-associated (CA) MRSA genotypes increasing in prevalence over time (P < 0.001). The highest susceptibility rates among MRSA were 100% for vancomycin, 100% for ceftobiprole, 100% for linezolid, 99.7% for ceftaroline, 99.7% for daptomycin and 99.7% for tigecycline. The highest susceptibility rates among E. coli were 100% for tigecycline, 99.9% for meropenem, 99.7% for colistin and 94.2% for piperacillin/tazobactam. MDR was identified in 26.3% of E. coli isolates, with 10.1% producing an ESBL. The highest susceptibility rates among P. aeruginosa were 97.5% for ceftolozane/tazobactam, 96.1% for amikacin, 94.7% for colistin and 93.3% for tobramycin.

CONCLUSIONS

The most active agents against Gram-negative bacilli were the carbapenems, tigecycline and piperacillin/tazobactam. Against Gram-positive cocci, the most active agents were vancomycin, daptomycin and linezolid. The prevalence of CA-MRSA genotypes and ESBL-producing E. coli collected from ICUs increased significantly over time.

Homodimeric Tobramycin Adjuvant Repurposes Novobiocin as an Effective Antibacterial Agent against Gram-Negative Bacteria

Low permeability across the outer membrane is a major reason why most antibiotics are ineffective against Gram-negative bacteria. Agents that permeabilize the outer membrane are typically toxic at their effective concentrations. Here, we report the development of a broad-spectrum homodimeric tobramycin adjuvant that is nontoxic and more potent than the gold standard permeabilizing agent, polymyxin B nonapeptide. In pilot studies, the adjuvant confers potent bactericidal activity on novobiocin against Gram-negative bacteria, including carbapenem-resistant and colistin-resistant strains bearing plasmid-borne mcr-1 genes. Resistance development to the combination was significantly reduced, relative to novobiocin alone, and there was no induction of cross-resistance to other antibiotics, including the gyrase-acting fluoroquinolones. Tobramycin homodimer may allow the use of lower doses of novobiocin, overcoming its twin problem of efficacy and toxicity.

Enterococcus hirae, Enterococcus faecium and Enterococcus faecalis show different sensitivities to typical biocidal agents used for disinfection

BACKGROUND

Enterococcus faecium and E. faecalis are known nosocomial pathogens. The bactericidal activity of biocidal agents used for disinfection, however, is determined with E. hirae.

AIM

To find out whether E. hirae is a suitable species to evaluate the efficacy of biocidal agents against the clinically relevant species E. faecalis and E. faecium.

METHODS

The bactericidal activity was determined in suspension tests according to EN 13727 using E. faecium ATCC 6057, E. faecalis ATCC 47077 and E. hirae ATCC 10541. Glutaraldehyde, ethanol, benzalkonium chloride, peracetic acid and sodium hypochlorite were used with three exposure times per biocide. When major differences in the sensitivity of the three enterococcal species to the respective substance was found, two more replicates were performed. The number of colony-forming units (cfu) was transformed into decimal logarithms. Results from replicate experiments were described with means and standard deviations.

FINDINGS

At a 5-min exposure time, E. hirae was found to be more tolerant to 0.2% glutaraldehyde and 0.0125% peracetic acid compared to E. faecium and E. faecalis, whereas it was more susceptible to 40% ethanol and 3% sodium hypochlorite. Only with 0.00125% benzalkoniumchloride (15 min) was the susceptibility of E. hirae between that of E. faecium and E. faecalis.

CONCLUSIONS

E. hirae is a suitable species when a bactericidal activity should be determined against enterococci with glutaraldehyde and peracetic acid. E. hirae may not be a suitable species for ethanol or sodium hypochlorite if the bactericidal activity should include the clinical pathogens E. faecium and E. faecalis.

Development of a nebramine-cyclam conjugate as an antibacterial adjuvant to potentiate β-lactam antibiotics against multidrug-resistant P. aeruginosa

The β-lactams are the most widely used class of antibiotics due to their safety, effectiveness, and spectrum of activity. As a result of their ubiquitous usage, there has been a steady rise in β-lactam resistant Gram-negative bacteria, especially Pseudomonas aeruginosa, resulting in limited treatment options. P. aeruginosa can develop multidrug-resistant phenotypes using a multifaceted approach of β-lactamase expression, decreased porin production and increased efflux. Current β-lactamase inhibitors address drug hydrolyzing enzymes but may not be as effective in phenotypes with reduced permeability and/or overexpressed efflux pumps. Herein, we present the synthesis and biological evaluation of a nebramine-cyclam conjugate molecule that is able to potentiate β-lactam antibiotics, as well as other legacy antibiotics, against P. aeruginosa in vitro. Combination studies show that this adjuvant is able to synergize with β-lactams such as aztreonam and ceftazidime against multidrug-resistant and extremely drug-resistant clinical isolates through a hypothesized mechanism of outer membrane permeabilization. Importantly, the addition of low concentrations (8 µM) of the nontoxic nebramine-cyclam conjugate is able to further potentiate existing β-lactam/β-lactamase inhibitor combinations in β-lactamase-harboring P. aeruginosa strains. These data support a potential application of the nebramine-cyclam conjugate as an adjuvant for treating infections caused by P. aeruginosa strains that utilize multiple mechanisms of resistance.

Antimicrobial resistance trends in methicillin-resistant and methicillin-susceptible Staphylococcus aureus and Staphylococcus epidermidisisolates obtained from patients admitted to intensive care units. 2010-2015

Introducción. La aparición y la diseminación de cepas resistentes en hospitales, principalmente en unidades de cuidado intensivo (UCI), se han convertido en un serio problema de salud pública.Objetivo. Analizar la tendencia de los fenotipos de resistencia de Staphylococcus aureus y Staphylococcus epidermidis resistentes y susceptibles a meticilina aislados en pacientes atendidos en UCI de un hospital de alta complejidad de Cartagena, Colombia, del 2010 al 2015.Materiales y métodos. Estudio analítico transversal realizado entre enero de 2010 y diciembre de 2015. Se utilizaron aislamientos de S. aureus y S. epidermidis meticilino-susceptibles y meticilino-resistentes (SARM, SASR, SERM y SESM). La técnica de susceptibilidad empleada fue el método microdilución en caldo para la detección de la concentración mínima inhibitoria.Resultados. Se identificaron 313 aislamientos de Staphylococcus spp., la mayoría resistentes a meticilina (63.6%). Las cepas SARM y SERM correspondieron al 13.7% y al 27.8% del total de aislamientos, respectivamente. Los mayores porcentajes de resistencia en SARM y SERM correspondieron a eritromicina (57.6% y 81.2%, respectivamente), clindamicina (54.6% y 71.0%), ciprofloxacina (48.4% y 36.4%) y trimetoprima-sulfametoxazol (36.4% y 51.4%).Conclusión. Los resultados encontrados sugieren el replanteamiento de las estrategias de control de la resistencia antimicrobiana en el hospital objeto de estudio.

Recent Advances in Investigation, Prevention, and Management of Healthcare-Associated Infections (HAIs): Resistant Multidrug Strain Colonization and Its Risk Factors in an Intensive Care Unit of a University Hospital

Active screening for resistant multidrug strain carriers remains an important component of infection control policy in any healthcare setting indifferent of financial and logistical costs. The objective of our study was to determine the spectrum of bacterial colonization individually among intensive care unit patients. A retrospective observational study was performed in the Intensive Care Unit of Emergency Clinical County Hospital of Oradea during 2017. Medical records of the patients were used for evaluation of source of ICU admission, previous antibiotic therapy, comorbidities, and length of hospital stay. Nasal and groin swabs for MRSA detection and rectal swabs for ESBL, VRE, and CRE detection were collected upon ICU admission of all patients in the first 24 hours and after 7 days. Swab samples were processed for isolation and identification of these resistant multidrug strains. Bacterial colonization on admission was detected in a quarter of patients included in the study. Carbapenemase-producing bacteria were the most common colonizers (21.16%). On admission, 12.06% of patients have been colonized by ESBL-producing members of the family Enterobacterales. Risk factors for colonization on admission to the ICU were chronic liver diseases and chronic renal failure for ESBL infection and chronic liver disease for CRE in male patients. Evaluation of Carmeli's score for male patients showed association only with CRE colonization. Chronic renal failure was found as risk factor for ESBL colonization in female patients. The prevalence of MRSA was 5.23% and less than 1% for VRE. There was no association between any risk factors studied and the presence of S. aureus or VRE upon admission. The 7-day ICU stay also proved to be an increased risk for ESBL and CRE infection.

Heterodimeric Rifampicin-Tobramycin conjugates break intrinsic resistance of Pseudomonas aeruginosa to doxycycline and chloramphenicol in vitro and in a Galleria mellonella in vivo model

Intrinsic resistance in Pseudomonas aeruginosa, defined by chromosomally encoded low outer membrane permeability and constitutively over-expressed efflux pumps, is a major reason why the pathogen is refractory to many antibiotics. Herein, we report that heterodimeric rifampicin-tobramycin conjugates break this intrinsic resistance and sensitize multidrug and extensively drug-resistant P. aeruginosa to doxycycline and chloramphenicol in vitro and in vivo. Tetracyclines and chloramphenicol are model compounds for bacteriostatic effects, but when combined with rifampicin-tobramycin adjuvants, their effects became bactericidal at sub MIC levels. Potentiation of tetracyclines correlates with the SAR of this class of drugs and is consistent with outer membrane permeabilization and efflux pump inhibition. Overall, this strategy finds new uses for old drugs and presents an avenue to expand the therapeutic utility of legacy antibiotics to recalcitrant pathogens such as P. aeruginosa.

Polybasic peptide-levofloxacin conjugates potentiate fluoroquinolones and other classes of antibiotics against multidrug-resistant Gram-negative bacteria

To address the rising threat of multidrug-resistant (MDR) bacteria, new therapeutic strategies must be developed. Efficacious drug combinations consisting of existing antibiotics and enhancer biomolecules called adjuvants offers a viable strategy. We have previously reported antibiotic hybrids consisting of tobramycin appended to different fluoroquinolones that possess potential as stand-alone antimicrobials as well as adjuvants. Herein, we report the synthesis of polybasic peptide-levofloxacin conjugates based on these tobramycin-fluoroquinolone hybrids. It was found that conjugating polybasic peptides to the fluoroquinolone levofloxacin, along with the addition of an aliphatic hydrocarbon tether, resulted in the ability of these compounds to potentiate fluoroquinolones and other antibiotics against MDR Gram-negative bacteria. The conjugates were able to potentiate ciprofloxacin, levofloxacin and moxifloxacin against MDR clinical isolates of Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and to a lesser extent, Acinetobacter baumannii. Preliminary data revealed that the conjugates interfered with active efflux of fluoroquinolones in P. aeruginosa. In addition, synergy was observed with a wide array of other antibiotics against P. aeruginosa, including those that suffered from restricted outer membrane penetration, suggesting that in addition to blocking active efflux, the polybasic peptide-levofloxacin conjugates possessed the ability to disrupt and permeabilize the outer membrane of Gram-negative bacteria.

Integrating Culture-based Antibiotic Resistance Profiles with Whole-genome Sequencing Data for 11,087 Clinical Isolates

Emerging antibiotic resistance is a major global health threat. The analysis of nucleic acid sequences linked to susceptibility phenotypes facilitates the study of genetic antibiotic resistance determinants to inform molecular diagnostics and drug development. We collected genetic data (11,087 newly-sequenced whole genomes) and culture-based resistance profiles (10,991 out of the 11,087 isolates comprehensively tested against 22 antibiotics in total) of clinical isolates including 18 main species spanning a time period of 30 years. Species and drug specific resistance patterns were observed including increased resistance rates for Acinetobacter baumannii to carbapenems and for Escherichia coli to fluoroquinolones. Species-level pan-genomes were constructed to reflect the genetic repertoire of the respective species, including conserved essential genes and known resistance factors. Integrating phenotypes and genotypes through species-level pan-genomes allowed to infer gene-drug resistance associations using statistical testing. The isolate collection and the analysis results have been integrated into GEAR-base, a resource available for academic research use free of charge at https://gear-base.com.

Nosocomial Pathogens: An In-Depth Analysis of the Vectorial Potential of Cockroaches

Nosocomial or healthcare-associated infections are regarded as the most frequent adverse event that threatens patients' safety and has serious economic and social consequences. Cockroach infestation is common in many hospitals, especially in the developing world. Common nosocomial pathogens isolated from cockroaches include Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae. Cockroaches also harbor epidemiologically significant antibiotic-resistant organisms, such as carbapenem-resistant Enterobacteriaceae, which complicate nosocomial infections. Therefore, cockroaches constitute an important vector for nosocomial pathogens, and there should be zero tolerance for their presence in healthcare facilities. This paper aims to elucidate the possible role of cockroaches in nosocomial infections by reviewing the relevant research publications.

Prevalence of vancomycin resistance among isolates of enterococci in Iran: a systematic review and meta-analysis

Introduction

Enterococcus is responsible for 10% of hospital-acquired infections. The purpose of this review was to evaluate the prevalence of vancomycin-resistant Enterococcus (VRE) isolates in Iran using a meta-analysis method.

Materials and methods

Iranian databases, including Magiran and IranDoc, and international databases, including PubMed and MedLib, were examined carefully, and a total of 20 articles published between 2000 and 2011 were extracted. The data were subjected to meta-analysis and random-effects models. In addition, heterogeneous studies were assessed using the I ² index. Finally, the data were analyzed using R and STATA software.

Results

The results showed that the strain of Enterococcus faecalis had been more common than Enterococcus faecium in clinical infection (69% vs 28%). However, resistance to vancomycin was higher among strains of E. faecium compared with strains of E. faecalis (33% vs 3%). The complete resistance, intermediate resistance, and sensitivity to vancomycin among Enterococcus isolates were 14% (95% CI: 11, 18), 14% (95% CI: 5, 23), and 74% (95% CI: 65, 83), respectively. The resistance patterns, depending on the sample type, did not show a significant difference. In addition, the resistance of isolated strains to vancomycin in outpatients was significantly higher than that in inpatients (16% vs 1%). Moreover, 80%-86% of resistant strains were genotype van A and 14%-20% of resistant strains were genotype van B.

Conclusion

The findings of the present review show that there is a high frequency of resistant Enterococcus in Iran. Therefore, consideration of the prevalence and frequency of subjected resistant strains can be helpful for decision makers to implement proper health policies in this direction.

Dilipid ultrashort cationic lipopeptides as adjuvants for chloramphenicol and other conventional antibiotics against Gram-negative bacteria

The necessity to develop therapeutic agents and strategies to abate the spread of antibiotic-resistant pathogens is prominent. Antimicrobial peptides (AMPs) provide scaffolds and inspiration for antibiotic development. As an AMP of shorter scaffold, eight dilipid ultrashort cationic lipopeptides (dUSCLs) were prepared consisting of only four amino acids and varying dilipids. Lipids were acylated at the peptide N-terminus and the ε-amine side chain of the N-terminal L-lysine. Compounds that possess aliphatic dilipids of ≥ 11 carbons-long showed significant hemolysis and therefore limited therapeutic application. Several non-hemolytic dUSCLs were identified to enhance the activity of chloramphenicol and other conventional antibiotics against Gram-negative bacteria. Compounds 2 and 6 have a short peptide sequence of KKKK and KKGK, respectively, and are both acylated with an aliphatic dilipid of nine carbons-long potentiated chloramphenicol against MDR clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae. Both dUSCLs showed comparable adjuvant potency in combination with chloramphenicol. However, dUSCL 2 synergized with a wider span of antibiotic classes against P. aeruginosa relative to dUSCL 6 that included rifampicin, trimethoprim, minocycline, fosfomycin, piperacillin, ciprofloxacin, levofloxacin, moxifloxacin, linezolid and vancomycin. Our data revealed that dUSCLs can indirectly disrupt active efflux of chloramphenicol in P. aeruginosa. This along with their membrane-permeabilizing properties may explain the dUSCLs synergistic combination with conventional antibiotics against Gram-negative bacteria.

Development of dilipid polymyxins: Investigation on the effect of hydrophobicity through its fatty acyl component

Continuous development of new antibacterial agents is necessary to counter the problem of antimicrobial resistance. Polymyxins are considered as drugs of last resort to combat multidrug-resistant Gram-negative pathogens. Structural optimization of polymyxins requires an in-depth understanding of its structure and how it relates to its antibacterial activity. Herein, the effect of hydrophobicity was explored by adding a secondary fatty acyl component of varying length onto the polymyxin structure at the amine side-chain of l-diaminobutyric acid at position 1, resulting to the development of dilipid polymyxins. The incorporation of an additional lipid was found to confer polymyxin activity against Gram-positive bacteria, to which polymyxins are inherently inactive against. The dilipid polymyxins showed selective antibacterial activity against Pseudomonas aeruginosa. Moreover, dilipid polymyxin 1 that consists of four carbon-long aliphatic lipids displayed the ability to enhance the antibacterial potency of other antibiotics in combination against P. aeruginosa, resembling the adjuvant activity of the well-known outer membrane permeabilizer polymyxin B nonapeptide (PMBN). Interestingly, our data revealed that dilipid polymyxin 1 and PMBN are substrates for the MexAB-OprM efflux system, and therefore are affected by efflux. In contrast, dilipid polymyxin analogs that consist of longer lipids and colistin were not affected by efflux, suggesting that the lipid component of polymyxin plays an important role in resisting active efflux. Our work described herein provides an understanding to the polymyxin structure that may be used to usher the development of enhanced polymyxin analogs.

Intravenous Fosfomycin: An Assessment of Its Potential for Use in the Treatment of Systemic Infections in Canada

Fosfomycin is a bactericidal agent that inhibits cell wall synthesis using a mechanism of action distinct from β-lactams or other antimicrobial agents. It is a broad-spectrum agent that is frequently active against antimicrobial-resistant bacterial pathogens including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), multidrug-resistant (MDR) Enterobacteriaceae, and some isolates of MDR Pseudomonas aeruginosa. Intravenous fosfomycin has been prescribed for a wide variety of infections in many countries for >40 years. It is most frequently used in combination with other antimicrobial agents (e.g., β-lactams, carbapenems, and aminoglycosides) and has an excellent safety profile, including in neonates and children, even with long-term administration (weeks). Fosfomycin achieves extensive tissue distribution including difficult to reach compartments such as aqueous humor, vitreous humor, abscess fluid, and CSF. Available data, to date, suggest no clinically relevant pharmacological interactions between fosfomycin and other agents, including drugs, stimulants, or food. Intravenous fosfomycin's role in therapy in Canada is likely as an agent used alone or in combination for complicated urinary tract infections in hospitalized patients as well as hospitalized patients with MDR infections who have not responded to first-, and potentially, second-line antimicrobials or in patients who cannot tolerate (due to adverse effects) first- and second-line antimicrobials.

Tobramycin-Linked Efflux Pump Inhibitor Conjugates Synergize Fluoroquinolones, Rifampicin and Fosfomycin against Multidrug-Resistant Pseudomonas aeruginosa

In this study, we examined the in vitro effect of tobramycin-efflux pump inhibitor (TOB-EPI) conjugates in combinations with fluoroquinolones, rifampicin and fosfomycin on the growth of multi-drug resistant (MDR) and extremely-drug resistant (XDR) Pseudomonas aeruginosa. The TOB-EPI conjugates include tobramycin covalently linked to 1-(1-naphthylmethyl)-piperazine (NMP) (1), paroxetine (PAR) (2) and a dibasic peptide analogue of MC-04,124 (DBP) (3). Potent synergism was found for combinations of TOB-NMP (1), TOB-PAR (2) or TOB-DBP (3) with either fluoroquinolones (moxifloxacin, ciprofloxacin), rifampicin or fosfomycin against a panel of multidrug-resistant/extensively drug-resistant (MDR/XDR) P. aeruginosa clinical isolates. In the presence of ≤8 mg/L (6.1–7.2 µM) (≤¼ × MIC_adjuvant) concentration of the three conjugates, the MIC₈₀ of moxifloxacin, ciprofloxacin, rifampicin and fosfomycin were dramatically reduced. Furthermore, the MIC₈₀ of rifampicin (0.25–0.5 mg/L) and fosfomycin (8–16 mg/L) were reduced below their interpretative susceptibility breakpoints. Our data confirm the ability of TOB-NMP (1), TOB-PAR (2) and TOB-DBP (3) conjugates to strongly synergize with moxifloxacin, ciprofloxacin, rifampicin and fosfomycin against MDR/XDR P. aeruginosa. These synergistic combinations warrant further studies as there is an urgent need to develop new strategies to treat drug-resistant P. aeruginosa infections.

Short Proline-Rich Lipopeptide Potentiates Minocycline and Rifampin against Multidrug- and Extensively Drug-Resistant Pseudomonas aeruginosa

A series of 16 short proline-rich lipopeptides (SPRLPs) were constructed to mimic longer naturally existing proline-rich antimicrobial peptides. Antibacterial assessment revealed that lipopeptides containing hexadecanoic acid (C16) possess optimal antibacterial activity relative to others with shorter lipid components. SPRLPs were further evaluated for their potential to serve as adjuvants in combination with existing antibiotics to enhance antibacterial activity against drug-resistant Pseudomonas aeruginosa Out of 16 prepared SPRLPs, C12-PRP was found to significantly potentiate the antibiotics minocycline and rifampin against multidrug- and extensively drug-resistant (MDR/XDR) P. aeruginosa clinical isolates. This nonhemolytic C12-PRP is comprised of the heptapeptide sequence PRPRPRP-NH2 acylated to dodecanoic acid (C12) at the N terminus. The adjuvant potency of C12-PRP was apparent by its ability to reduce the MIC of minocycline and rifampin below their interpretative susceptibility breakpoints against MDR/XDR P. aeruginosa An attempt to optimize C12-PRP through peptidomimetic modification was performed by replacing all l- to d-amino acids. C12-PRP demonstrated that it was amenable to optimization, since synergism with minocycline and rifampin were retained. Moreover, C12-PRP displayed no cytotoxicity against human liver carcinoma HepG2 and human embryonic kidney HEK-293 cell lines. Thus, the SPRLP C12-PRP is a lead adjuvant candidate that warrants further optimization. The discovery of agents that are able to resuscitate the activity of existing antibiotics against drug-resistant Gram-negative pathogens, especially P. aeruginosa, is of great clinical interest.

Polymyxin B3-Tobramycin Hybrids with Pseudomonas aeruginosa-Selective Antibacterial Activity and Strong Potentiation of Rifampicin, Minocycline, and Vancomycin

There is an urgent need to develop novel antibacterial agents able to eradicate drug-resistant Gram-negative pathogens such as Pseudomonas aeruginosa. Antimicrobial hybrids have emerged as a promising strategy to combat bacterial resistance, as a stand-alone drug but also as an adjuvant in combination with existing antibiotics. Herein, we report for the first time the synthesis and biological evaluation of polymyxin-aminoglycoside heterodimers composed of polymyxin B₃ covalently linked to tobramycin via an aliphatic hydrocarbon linker. The polymyxin B₃-tobramycin hybrids demonstrate potent activity against carbapenem-resistant as well as multidrug- or extensively drug-resistant (MDR/XDR) P. aeruginosa clinical isolates. Furthermore, the most potent hybrid was able to synergize with currently used antibiotics against wild-type and MDR/XDR P. aeruginosa but also against Acinetobacter baumannii as well. The promising biological activity described herein warrants additional studies into design and development of new antimicrobial hybrids able to surmount the problem of antimicrobial resistance.

Amphiphilic lysine conjugated to tobramycin synergizes legacy antibiotics against wild-type and multidrug-resistant Pseudomonas aeruginosa

Peptidomimetic modification is a common route of optimization for biologically active peptides. Previous studies in our group have shown that conjugation of amphiphilic tobramycin to other antibacterials enhance their latent outer membrane permeabilizing and efflux blocking activity toward Gram-negative pathogens including Pseudomonas aeruginosa. Herein, we describe the antimicrobial adjuvant properties of amphiphilic lysine ligated to tobramycin. The most potent amphiphilic lysine-tobramycin conjugate 3 potentiated the antibacterial efficacy of 8 clinically used antibiotics against wild type, multidrug- and extensively drug-resistant P. aeruginosa isolates from Canadian hospitals whereas amphiphilic lysine 4 did not. Antibiotics that are synergistic with conjugate 3 included moxifloxacin, ciprofloxacin, erythromycin, chloramphenicol, trimethoprim, novobiocin, linezolid, and fosfomycin. Out of these 8 antibiotics, novobiocin showed highest synergy.

MexXY efflux pump overexpression and aminoglycoside resistance in cystic fibrosis isolates of Pseudomonas aeruginosa from chronic infections

In this study, we analyzed 15 multidrug-resistant cystic fibrosis isolates of Pseudomonas aeruginosa from chronic lung infections for expression of 4 different multidrug efflux systems (MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY), using quantitative reverse transcriptase PCR. Overexpression of MexXY pump was observed in all of the isolates tested. Analysis of regulatory genes that control the expression of these 4 efflux pumps revealed a number of previously uncharacterized mutations. Our work shows that MexXY pump overexpression is common in cystic fibrosis isolates and could be contributing to their reduced aminoglycoside susceptibility. Further, we also identified novel mutations in the regulatory genes of the 4 abovementioned Resistance-Nodulation-Division superfamily pumps that may be involved in the overexpression of these pumps.

Predictive utility of swab screening for vancomycin-resistant Enterococcus in selection of empiric antibiotics for Enterococcus sterile-site infections: a retrospective cohort study

BACKGROUND

Swab screening for vancomycin-resistant Enterococcus (VRE) is used to identify VRE carriers and thus prevent transmission of this organism. We tested whether screening results could have unintended benefits in predicting the vancomycin susceptibility of subsequent Enterococcus infections experienced by these patients.

METHODS

We conducted a retrospective cohort study of all patients admitted to a large tertiary care hospital between 2010 and 2015 who underwent swab screening for VRE before experiencing an Enterococcus sterile-site infection. We derived test characteristics using the screening result as the test variable predicting the presence or absence of vancomycin resistance in the sterile-site Enterococcus species.

RESULTS

Culture results for sterile-site samples were positive for Enterococcus for 619 patients during the study period. Of these, 488 (79%) had previously undergone VRE screening. A total of 19 (4%) of the 488 screening results were positive for VRE, and 10 (2%) of the sterile-site Enterococcus isolates were resistant to vancomycin. The overall specificity of VRE swabs was 97% (95% confidence interval [CI] 96%-99%), sensitivity was 70% (95% CI 35%-93%), the positive likelihood ratio was 28 (95% CI 14-56), and the negative likelihood ratio was 0.31 (95% CI 0.12-0.79). The post-test probability of vancomycin resistance in a sterile-site culture, given a positive result with VRE screening swab, was 37% using study data and 83% using published aggregate prevalence data for VRE in the United States.

INTERPRETATION

Prior VRE screening swab results represent a useful tool for predicting vancomycin resistance in sterile-site Enterococcus infections. Patients with a positive result for VRE screening swab and Enterococcus identified by culture of sterile-site samples should receive empiric treatment with linezolid or daptomycin until sensitivity results are available.

Nosocomial bacterial infections and their antimicrobial susceptibility patterns among patients in Ugandan intensive care units: a cross sectional study

Background

The intensive care unit (ICU) admits critically ill patients requiring advanced airway, respiratory, cardiac and renal support. Despite the highly-specialized interventions, the mortality and morbidity is still high due to a number of reasons including nosocomial infections, which are the most likely complications in hospitalized patients with the rates being highest among ICU patients.

Methods

In this cross-sectional study of 111 adult patients admitted to 2 of the ICUs in Uganda, we set out to describe the commonest bacterial infections, their antimicrobial susceptibility patterns and factors associated with development of a nosocomial infection.

Results

Klebsiella pneumoniae (30%), Acinetobacter species (22%) and Staphylococcus aureus (14%) were the most frequently isolated bacteria. The prevalence of multidrug resistant bacterial species was 58%; 50% Escherichia coli and 33.3% Klebsiella pneumoniae were extended spectrum beta lactamase or AmpC beta lactamase producers and 9.1% Acinetobacter species were extensive drug resistant. Imipenem was the antibiotic with the highest susceptibility rates across most bacterial species. Institution of ventilator support (P 0.003) and severe traumatic brain injury (P 0.035) were highly associated with the development of nosocomial infections.

Conclusion

Due to the high prevalence of multi drug resistant (MDR) and extensive drug resistant bacterial species, there is a need for development of strong policies on antibiotic stewardship, antimicrobial surveillance and infection control to help guide empirical antibiotic therapy and prevent the spread of MDR bacteria and antibiotic drug resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2695-5) contains supplementary material, which is available to authorized users.