LL-37_Renalexin hybrid peptide exhibits antimicrobial activity at lower MICs than its counterpart single peptides

An alarming global public health and economic peril has been the emergence of antibiotic resistance resulting from clinically relevant bacteria pathogens, including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species constantly exhibiting intrinsic and extrinsic resistance mechanisms against last-resort antibiotics like gentamycin, ciprofloxacin, tetracycline, colistin, and standard ampicillin prescription in clinical practices. The discovery and applications of antimicrobial peptides (AMPs) with antibacterial properties have been considered and proven as alternative antimicrobial agents to antibiotics. In this study, we have designed, produced, and purified a recombinant novel multifunctional hybrid antimicrobial peptide LL-37_Renalexin for the first time via the application of newly designed flexible GS peptide linker coupled with the use of our previously characterized small metal-binding proteins SmbP and CusF3H+ as carrier proteins that allow for an enhanced bacterial expression, using BL21(DE3) and SHuffle T7(DE3) Escherichia coli strains, and purification of the hybrid peptide via immobilized metal affinity chromatography. The purified tag-free LL-37_Renalexin hybrid peptide exhibited above 85% reduction in bacteria colony-forming units and broad-spectrum antimicrobial effects against Staphylococcus aureus, Escherichia coli, Methicillin-resistant Staphylococcus aureus (MRSA), and Klebsiella pneumoniae bacteria clinical isolates at a lower minimum inhibition concentration level (10-33 μM) as compared to its counterpart single-AMPs LL-37 and Renalexin (50-100 μM). KEY POINTS: • The hybrid antimicrobial peptide LL-37_Renalexin has been designed using a GS linker. • The peptide was expressed with the carrier proteins SmbP and CusF3H+. • The hybrid peptide shows antibacterial potency against clinical bacterial isolates.

Echinacoside, a promising sortase A inhibitor, combined with vancomycin against murine models of MRSA-induced pneumonia

Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogenic bacterium responsible for a range of severe infections, such as skin infections, bacteremia, and pneumonia. Due to its antibiotic-resistant nature, current research focuses on targeting its virulence factors. Sortase A (SrtA) is a transpeptidase that anchors surface proteins to the bacterial cell wall and is involved in adhesion and invasion to host cells. Through fluorescence resonance energy transfer (FRET), we identified echinacoside (ECH), a natural polyphenol, as a potential SrtA inhibitor with an IC50 of 38.42 μM in vitro. It was demonstrated that ECH inhibited SrtA-mediated S. aureus fibrinogen binding, surface protein A anchoring, and biofilm formation. The fluorescence quenching assay determined the binding mode of ECH to SrtA and calculated the KA-binding constant of 3.09 × 105 L/mol, demonstrating the direct interaction between the two molecules. Molecular dynamics simulations revealed that ECH-SrtA interactions occurred primarily at the binding sites of A92G, A104G, V168A, G192A, and R197A. Importantly, the combination of ECH and vancomycin offered protection against murine models of MRSA-induced pneumonia. Therefore, ECH may serve as a potential antivirulence agent against S. aureus infections, either alone or in combination with vancomycin.

Maurice A, Dogan TL, Ceesay B, Umukoro S, Okomo U, Nwakanma D, Roca A, Secka O, Forrest K, Garner OB. Using an Antibiogram Profile to Improve Infection Control and Rational Antimicrobial Therapy in an Urban Hospital in The Gambia, Strategies and Lessons for Low- and Middle-Income Countries

Antimicrobial resistance is a global health threat and efforts to mitigate it is warranted, thus the need for local antibiograms to improve stewardship. This study highlights the process that was used to develop an antibiogram to monitor resistance at a secondary-level health facility to aid empirical clinical decision making in a sub-Saharan African county. This retrospective cross-sectional descriptive study used 3 years of cumulative data from January 2016 to December 2018. Phenotypic data was manually imputed into WHONET and the cumulative antibiogram constructed using standardized methodologies according to CLSI M39-A4 guidelines. Pathogens were identified by standard manual microbiological methods and antimicrobial susceptibility testing was performed using Kirby-Bauer disc diffusion method according to CLSI M100 guidelines. A total of 14,776 non-duplicate samples were processed of which 1163 (7.9%) were positive for clinically significant pathogens. Among the 1163 pathogens, E. coli (n = 315) S. aureus (n = 232), and K. pneumoniae (n = 96) were the leading cause of disease. Overall, the susceptibility for E. coli and K. pneumoniae from all samples were: trimethoprim-sulfamethoxazole (17% and 28%), tetracycline (26% and 33%), gentamicin (72% and 46%), chloramphenicol (76 and 60%), and ciprofloxacin (69% and 59%), and amoxicillin/clavulanic (77% and 54%) respectively. Extended spectrum beta-lactamase (ESBL) resistance was present in 23% (71/315) vs. 35% (34/96) respectively. S. aureus susceptibility for methicillin was 99%. This antibiogram has shown that improvement in combination therapy is warranted in The Gambia.

Pattern and Sensitivity of Bacterial Colonization on the Tip of Non-Tunneled Temporary Hemodialysis Catheters: Results of a Tertiary Hospital in Somalia

Introduction

Bacterial colonization on the tip of non-tunneled temporary hemodialysis catheters (NTHCs) and associated catheter-related infections (CRI) is a common complication in hemodialysis (HD) patients. In this study, we aimed to investigate the pattern of bacterial colonization formed on the tip of non-tunneled temporary hemodialysis catheters and their antibiotic sensitivity.

Methods

This retrospective analysis was performed in the HD unit of an Education and Research Hospital that follows up a universe of approximately 300 patients, primarily from Mogadishu, Somalia. From September 2020 to September 2021, a total of 137 temporary HD catheters were removed and their tips were sent for culture after there was a suspicion of CRI and other sources of infection were excluded. HD Catheter tips were cultured semi-quantitatively, and the antibiogram of the positive cultures was studied.

Results

Gram-positive cocci were found to be the most predominant bacterial organisms in positive cultures with 27 (31.0%) for Staphylococcus aureus, 9 (10.3%) for Staphylococcus haemolyticus and 5 (5.7%) for Staphylococcus epidermidis. We found Enterococci to be 5.7% of the isolated microorganisms. Gram-negative pathogens isolated included Escherichia coli 13 (14.9%) as the most common, followed by Klebsiella pneumoniae 10 (11.5%) and Acinetobacter baumannii (4.6%). Methicillin-resistant Staphylococcus aureus (MRSA) was found to be 9.4%. Gram-positive isolates showed high sensitivity (100%) to Linezolid, Daptomycin, Vancomycin, and Tigecycline, but a low sensitivity rate to Oxacillin (41.2%). Gram-negative isolates had the highest sensitivity to Tigecycline (100%), Imipenem (88.9%), and Amikacin (87%) but low sensitivity to Ampicillin (4.8%), Trimethoprim/Sulfamethoxazole (TMP-SMX) (23.1%), and Ceftazidime (7.1%).

Conclusion

We conclude that each institution should have its own antibiogram in the management of HD CRIs. According to our findings in this study, we recommend intravenous Vancomycin and Imipenem as empirical therapy in patients with suspected HD CRIs.

Use of Local Antibiogram Data and Antimicrobial Importance Ratings to Select Optimal Empirical Therapies for Urinary Tract Infections in Dogs and Cats

International and Australian veterinary antimicrobial use guidelines recommend amoxicillin or trimethoprim-sulfonamide (TMS) for the empirical treatment of sporadic urinary tract infections (UTIs) in dogs and cats. However, in practice, these antibiotics are rarely used, and no large-scale analyses have examined the antibiograms of bacteria isolated from UTIs to validate these recommendations in Australia. We analyzed five years of urine culture and antimicrobial susceptibility data from an Australian veterinary laboratory. The analysis included 6196 urinary isolates from dogs and cats, 78% of which were from samples submitted by first-opinion veterinary clinics. Escherichia coli, Enterococcus faecalis, Staphylococcus pseudintermedius and Proteus spp. were the most prevalent organisms. More than 80% of all isolated cocci were susceptible to amoxicillin, and more than 80% of bacilli were susceptible to TMS. A total of 94% of isolates were susceptible to at least one antimicrobial drug categorized as low-importance in Australia. The prevalence of multi-drug resistance (MDR) was highest in E. coli, at 9.7%; 84% of these MDR isolates were susceptible to amoxicillin-clavulanate. We performed population-level antimicrobial treatment simulations and proposed a novel method for integrating antimicrobial importance ratings with antibiogram data to optimize the selection of empirical therapy. Our findings support current guideline recommendations to use amoxicillin or TMS. We also found that bacterial morphology assisted with selection; amoxicillin was a better choice for cocci and TMS for bacilli.

Antibiotic Use by Pediatric Residents: Identifying Opportunities and Strategies for Antimicrobial Stewardship

OBJECTIVES

To determine the antibiotic prescribing practices of pediatric residents and assess how they acquire knowledge leading to prescribing behaviors.

METHODS

We performed a cross-sectional electronic survey of all pediatric residents at the Children's National Medical Center and Nicklaus Children's Hospital, assessing antibiotic prescribing patterns for common pediatric infections, use of antibiograms, and factors influencing antibiotic choice.

RESULTS

Eighty-five surveys (45%) were returned complete and included in the analysis. Increased deviations from clinical guideline recommendations were observed for antibiotic treatments of sinusitis and community-acquired pneumonia as compared with otitis media and group A streptococcal pharyngitis. Only 57% of residents reported having used antibiograms. General pediatric inpatient attending physicians were identified as the most influential source for house staff antibiotic knowledge.

CONCLUSIONS

Results illustrate the need for better promotion and integration of clinical guidelines with antibiograms when developing antibiotic education programs for residents in training. In addition, pediatric hospitalists should play an active role in the implementation of these programs and can provide valuable insight into the development of educational programs in conjunction with graduate medical education divisions.

Antibiogram for haemodialysis catheter-related bloodstream infections

Background. Haemodialysis (HD) catheter-related bloodstream infections (CRBSIs) are a major complication of long-term catheter use in HD. This study identified the epidemiology of HD CRBSIs and to aid in the choice of empiric antibiotics therapy given to patients with HD CRBSIs. Methods. Patients with HD CRBSIs were identified. Their blood cultures were performed according to standard sterile technique. Specimens were sent to the microbiology lab for culture and sensitivity testing. Results were tabulated in antibiograms. Results. 18 patients with a median age of 61.0 years (IQR: 51.5-73.25) were confirmed to have HD CRBSIs based on our study criteria. Eight (44.4%) patients had gram-negative infections, 7 (38.9%) patients gram-positive infections, and 3 (16.7%) patients had polymicrobial infections. We noted that most of the gram-negative bacteria were sensitive to ceftazidime. Unfortunately, cloxacillin resistance was high among gram-positive organisms. Coagulase-negative Staphylococcus and Bacillus sp. were the most common gram-positive organisms and they were sensitive to vancomycin. Conclusion. Our study revealed the increased incidence of gram-negative organism in HD CRBSIs. Antibiogram is an important tool in deciding empirical antibiotics for HD CRBSIs. Tailoring your antibiotics accordingly to the antibiogram can increase the chance of successful treatment and prevent the emergence of bacterial resistance.

Influence of antibiotic susceptibility patterns on empiric antibiotic prescribing for children hospitalized with community-acquired pneumonia

OBJECTIVE

The aim of this study was to determine the influence of pneumococcal penicillin-nonsusceptibility patterns on individual antibiotic prescription among 33 children's hospitals using a multilevel, random- intercept, logistic regression analysis.

METHODS

It was a multilevel cross-sectional study. The participants were children, 1-18 years of age, with community-acquired pneumonia (CAP) who were discharged in 2006. Hospital antibiotic susceptibility data were collected from surveys, and patient data were obtained from an administrative database. The primary exposure was the proportion of penicillin-nonsusceptible pneumococcal isolates reported in 2005 by each hospital. A secondary exposure included using the proportion of penicillin-resistant pneumococcal isolates to determine whether a threshold of susceptibility existed. Receipt of broad-spectrum empiric antibiotic therapy in 2006 (ie, antibiotics other than penicillins or aminopenicillins) was the main outcome measure.

RESULTS

Four thousand eight hundred eighty-eight children diagnosed with CAP were eligible. The proportion of penicillin-nonsusceptible isolates ranged from 9% to 70% across hospitals whereas the proportion of penicillin-resistant isolates ranged from 0% to 60%. Broad-spectrum antibiotics were prescribed to 93% of patients; 45% of patients received cephalosporin class antibiotics alone. There was no significant association between the proportion of pencillin-nonsusceptible pneumococcal isolates at individual hospitals and narrow-spectrum prescribing. However, every 10% increase in penicillin-resistant pneumococcal isolates was associated with a 39% increase in broad-spectrum antibiotic prescribing (adjusted odds ratio: 1.39; 95% confidence interval: 1.08-1.69).

CONCLUSIONS

There was substantial variability in empiric antibiotic prescribing for CAP among children's hospitals in the United States. High-levels (ie, resistant) but not modest-levels (ie, intermediate susceptibility) of penicillin resistance were associated with broad-spectrum antibiotic prescribing.

Real-time validation and presentation of the cumulative antibiogram and implications of presenting a standard format using a novel in-house software: ABSOFT

BACKGROUND

Antibiograms must use a standard format to present microbiologic data.

OBJECTIVE

When antibacterials are selected for the treatment of infections, knowledge of the locally most likely causative organisms and the prevalence of resistant pathogens to antibacterial agents are essential. This involves generating a cumulative antibiogram. We designed an in-house novel software to prepare our antibiogram, validate data, and analyze results and assessed the performance of this technology. It should be noted that analysis of specific antibiotic resistance patterns were not a focus of this study.

SETTING

The study was conducted at Al Khor Hospital, Hamad Medical Corporation, a 110-bed acute care hospital that serves patients in the northern area of Qatar. Positive microbiology cultures excluding surveillance samples, isolated in the microbiology laboratory from January 2008 to December 2008, were entered into an in-house software, ABSOFT, designed by one of the authors.

RESULTS

The software produced the antibiogram in a fixed format. Epidemiologic data and comparison of our data to the National Nosocomial Infection Surveillance benchmark for multidrug-resistant organism distribution were also presented real time. Automatic color-coded results in tabular format were printed instantaneously without errors, thus eliminating the need to be reviewed.

CONCLUSION

The paper highlights real-time validation and presentation of the cumulative antibiogram, additionally suggesting the format for reporting using a novel in-house software ABSOFT. This technology provided us an accurate, simple, cost-effective solution to present validated data real-time in a transparent and consistent manner. To our knowledge to date, no uniform format has been recommended for the presentation of cumulative antibiograms.

Pitfalls Associated With Antibiograms

An accurate, appropriately collated antibiogram represents an integral resource for health care providers when assessing bacterial resistance and guiding antimicrobial selection and formulary decisions. Interpretation of bacterial susceptibility statistics is problematic yet frequent and unrecognized pitfalls may be avoided by following the M39-A2 guidelines to ensure correct analysis and presentation of cumulative antimicrobial susceptibility test data. This review addresses guideline recommendations related to antibiogram development, CLSI breakpoint interpretation, antimicrobial inclusion decisions, and the avoidance of duplicate and surveillance isolates. Unit-specific antibiograms in critical care units is encouraged for differentiation between hospital-wide ecology and these specific areas harboring more resistant pathogens. Antibiograms cannot track the emergence of microbial resistance during therapy and discrepancies exist between automated microbiology surveillance systems and their agreement with manual surveillance methods. When striving to improve overall patient outcomes, the use of a well-produced and disseminated antibiogram helps guide clinical decision making for patients requiring antimicrobial therapy.

The utility of hospital antibiograms as tools for guiding empiric therapy and tracking resistance. Insights from the Society of Infectious Diseases Pharmacists

Hospital antibiograms are commonly used to help guide empiric antimicrobial treatment and are an important component of detecting and monitoring trends in antimicrobial resistance. To serve these purposes, antibiograms must be constructed using standardized methods that allow inter- and intrahospital comparisons. Antibiograms that include surveillance cultures and duplicate bacterial isolates can overestimate rates of resistance. In 2002, the National Committee for Clinical Laboratory Standards (now known as the Clinical and Laboratory Standards Institute [CLSI]) published standards for constructing antibiograms. According to national surveys, many of the recommended elements of the CLSI document have not been fully adopted. In lieu of full compliance with CLSI standards, it is necessary that the methods used to construct antibiograms are clearly delineated. Antibiograms have several limitations, such as their inability to track emergence of resistance during therapy. The antibiogram can serve as a valuable tool in guiding antimicrobial therapy, but other patient factors, such as previous infection history and antibiotic use, also need to be considered. Additional data are needed for specialized applications of resistance analyses.

Nationwide antibiogram analysis using NCCLS M39-A guidelines

Lack of standardization in antibiogram (ABGM) preparation (the overall profile of antimicrobial susceptibility results of a microbial species to a battery of antimicrobial agents) has not been addressed until recently. The objective of this study was to analyze current antibiograms using the recently published NCCLS M39-A guidelines for preparation of antibiograms to identify areas for improvement in the reporting of antibiogram susceptibility data. Antibiograms from across the United States were obtained by various methods, including direct mailings, Internet searches, and professional contacts. Each ABGM collected was analyzed using prospectively defined elements from the M39-A guidelines. Additionally, seven quality indicators were also evaluated to look for the reporting of any atypical or inappropriate susceptibility data. The 209 antibiograms collected from 149 institutions showed at least 85% compliance to 5 of the 10 M39-A elements analyzed. Clinically relevant elements not met included annual analysis, duplicate isolate notation, and the exclusion of organisms with fewer than 10 isolates. As for the quality indicators evaluated, unexpected results included the 7% of antibiograms that reported <100% vancomycin susceptibility for Staphylococcus aureus, 24% that had inconsistent beta-lactam susceptibility for Staphylococcus aureus, 20% that reported <100% imipenem susceptibility for Escherichia coli, and 37% that reported >0% ampicillin susceptibility for Klebsiella pneumoniae. These findings suggest that antibiograms should be reviewed thoroughly by infectious disease specialists (physicians and pharmacists), clinical microbiologists, and infection control personnel for identification of abnormal findings prior to distribution.