Synthetic antimicrobial peptides: Characteristics, design, and potential as alternative molecules to overcome microbial resistance

Recently, the dramatic emergence of antimicrobial resistance has received attention from World Health Organization. Synthetic antimicrobial peptides (SAMPs) are considered new weapons to fight against infections caused by multi-drug resistant pathogens. Here, the authors provide an overview of the current research on SAMPs. The focus is SAMPs, how to design them, which features must be considered during design, and comparison with natural peptides. This review also includes a discussion about the natural AMPs, mechanisms of action and applications as new drugs or even as adjuvants molecules to enhance commercial drugs activity. The advances in chemical synthesis have reduced the cost to produce synthetic peptides open ways to achieve new antimicrobial agents. Therefore, synthetic peptides are new promising molecules to safeguard human and animal health.

Intensive care unit-acquired pneumonia due to Pseudomonas aeruginosa with and without multidrug resistance

OBJECTIVE

Pseudomonas aeruginosa often presents multi-drug resistance (MDR) in intensive care unit (ICU)-acquired pneumonia (ICUAP), possibly resulting in inappropriate empiric treatment and worse outcomes. We aimed to identify patients with ICUAP at risk for these pathogens in order to improve treatment selection and outcomes.

METHODS

We prospectively assessed 222 consecutive immunocompetent ICUAP patients confirmed microbiologically. We determined the characteristics, risk factors, systemic inflammatory response and outcomes of P. aeruginosa pneumonia (Pa-ICUAP), compared to other aetiologies. We also compared patients with MDR vs. non-MDR Pa-ICUAP.

RESULTS

Pseudomonas aeruginosa was the most frequent aetiology (64, 29%); 22 (34%) cases had MDR. Independent predictors for Pa-ICUAP were prior airway colonization by P. aeruginosa, previous antibiotic treatment, solid cancer and shock; alcohol abuse and pleural effusion were independently associated to lower risk for Pa-ICUAP. Chronic liver disease independently predicted MDR among Pa-ICUAP. The inflammatory biomarkers were similar between all groups. Patients with Pa-ICUAP had lower unadjusted 90-day survival (p = 0.049). However, the 90-day survival adjusted for confounding factors using a propensity score did not differ between all groups.

CONCLUSION

Pseudomonas aeruginosa remains the most frequent aetiology of ICUAP, with high prevalence of MDR. These risk factors should be taken into account to avoid inappropriate empiric antibiotics for Pa-ICUAP. Pseudomonas aeruginosa, regardless multidrug resistance, was not associated with different propensity-adjusted survival.

SERS-based antibiotic susceptibility testing: Towards point-of-care clinical diagnosis

Emerging antibiotic resistant bacteria constitute one of the biggest threats to public health. Surface-enhanced Raman scattering (SERS) is highly promising for detecting such bacteria and for antibiotic susceptibility testing (AST). SERS is fast, non-destructive (can probe living cells) and it is technologically flexible (readily integrated with robotics and machine learning algorithms). However, in order to integrate into efficient point-of-care (PoC) devices and to effectively replace the current culture-based methods, it needs to overcome the challenges of reliability, cost and complexity. Recently, significant progress has been made with the emergence of both new questions and new promising directions of research and technological development. This article brings together insights from several representative SERS-based AST studies and approaches oriented towards clinical PoC biosensing. It aims to serve as a reference source that can guide progress towards PoC routines for identifying antibiotic resistant pathogens. In turn, such identification would help to trace the origin of sporadic infections, in order to prevent outbreaks and to design effective medical treatment and preventive procedures.

Ultrabroad-spectrum, multidrug resistant bacteria-killing, and biocompatible quaternized chitin derivative for infected wound healing

Wound infections have consistently been recognized as serious threats to human. The design of antimicrobial and biocompatible wound dressings for infected wounds is an area of constant research. Herein, we homogeneously synthesized an ultrabroad-spectrum antimicrobial and biocompatible quaternized chitin derivative (QC-4) in a high-efficiency and sustainable route using aqueous KOH/urea solution. Particularly, QC-4 displayed powerful multidrug resistant bacteria-killing activities even at a very low antimicrobial concentration range from 500 ng/mL to 5 μg/mL, including clinically prevalent multidrug-resistant Escherichia coli (MDR-E. coli), methicillin resistant Staphylococcus aureus (MRSA), multidrug-resistant Pseudomonas aeruginosa (MRPA), and multidrug-resistant Acinetobacter baumannii (MDR-A. baumannii). With the aim to facilitate clinical translation, we validated the biocompatibility and safety of QC-4 both in vitro and in vivo, and further assessed the effects of QC-4 on infected wound healing in a porcine infectious full-thickness skin wound model. QC-4 demonstrated significant reduction of microbial aggregates and enhanced wound-healing effects by promoted re-epithelialization and collagen deposition, which were quite comparable to that of commercial Alginate-Ag dressing and absolutely superior to commercial Chitoclot Bandage dressing. Additionally, we provided clear evidences that QC-4 had a unique mechanism of action by attracting electrostatically to the negatively charged microbial surface, thus damaging the microbial cell wall and membrane. Findings of this work provided robust preclinical rationale for the future translational applications of QC-4 as a novel ultrabroad-spectrum and multidrug resistant bacteria-killing antimicrobial wound dressing for clinical wound management.

Microbial profile of early and late onset ventilator associated pneumonia in the intensive care unit of a tertiary care hospital in bangalore, India

INTRODUCTION

Ventilator-associated pneumonia (VAP), an important form of hospital-acquired pneumonia (HAP), specifically refers to pneumonia developing in a patient on mechanical ventilator for more than 48 h after intubation or tracheostomy. Despite the advancements in antimicrobial regimes, VAP continues to be an important cause of morbidity and mortality. VAP requires a rapid diagnosis and initiation of appropriate antibiotic treatment, as there is adverse effect of inadequate antibiotic treatment on patients' prognosis and the emergence of multidrug-resistant (MDR) pathogens.

AIMS

The present study was undertaken to assess the etiological agents of early-onset and late-onset VAP and to know their sensitivity pattern.

MATERIAL AND METHODS

VAP data over a period of 12 months (February 2012 -February 2013) in a tertiary care ICU was retrospectively analysed. The patients were stratified by age, sex, duration of VAP (Early/Late onset) and the identified pathogens with their sensitivity pattern.

RESULTS

Incidence of VAP was found to be 35.14%, out of which 44.23% had early-onset (<4 days MV) VAP and 55.77% had late-onset (>4 days MV) VAP. The most common organisms isolated in early onset and late onset VAP was Pseudomonas aeruginosa, E.coli and Acinetobacter baumanii. All enterobacteriaceal isolates were extended spectrum beta lactamase (ESBL) producing organisms and all Staphylococcus aureus isolates except one were methicillin resistant. The incidence of Multidrug resistant (MDR) Pseudomonas aeruginosa and Acinetobacter were 40% and 37.5% respectively.

CONCLUSION

Due to the increasing incidence of multidrug-resistant organisms in our ICU, early and correct diagnosis of VAP is an urgent challenge for an optimal antibiotic treatment and cure. Hence, knowing the local microbial flora causing VAP and effective infection control practices are essential to improve clinical outcomes.

Antibiotic resistance in nosocomial respiratory infections

Nosocomial respiratory infections are the most common acquired infections in patients with severe underlying conditions and are responsible for high morbidity and mortality in this patient population. Multidrug-resistant (MDR) pathogens are associated with hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). This article describes the etiology, epidemiology, pathogenesis, diagnosis, and treatment of HAP and VAP associated with antibiotic-resistant bacterial pathogens.

Clinical characteristics and outcomes of neonates with polymicrobial ventilator-associated pneumonia in the intensive care unit

BACKGROUND

Ventilator associated pneumonia (VAP) caused by more than one microorganisms is not uncommon and may be potentially challenging, but the relevant data is scarce in ventilated neonates. We aimed to investigate the clinical characteristics and outcomes of polymicrobial VAP in the neonatal intensive care unit (NICU).

METHODS

All neonates with definite diagnosis of VAP from a tertiary level neonatal intensive care unit (NICU) in Taiwan between October 2017 and September 2020 were prospectively observed and enrolled for analyses. All clinical features, therapeutic interventions and outcomes were compared between the polymicrobial VAP and monomicrobial VAP episodes. Multivariate regression analyses were used to find the independent risk factors for treatment failure.

RESULTS

Among 236 episodes of neonatal VAP, 60 (25.4%) were caused by more than one microorganisms. Polymicrobial VAP episodes were more likely to be associated with multidrug-resistant pathogens (53.3% versus 34.7%, P = 0.014), more often occurred in later days of life and in neonates with prolonged intubation and underlying bronchopulmonary dysplasia. Otherwise most clinical characteristics of polymicrobial VAP were similar to those of monomicrobial VAP. The therapeutic responses and treatment outcomes were also comparable between these two groups, although modification of therapeutic antibiotics were significantly more common in polymicrobial VAP episodes than monomicrobial VAP episodes (63.3% versus 46.2%; P < 0.001). None of any specific pathogens was significantly associated with worse outcomes. Instead, it is the severity of illness, including presence of concurrent bacteremia, septic shock, and requirement of high-frequency oscillatory ventilator and underlying neurological sequelae that are independently associated with treatment failure.

CONCLUSIONS

Polymicrobial VAP accounted for 25.4% of all neonatal VAP in the NICU, and frequently occurred in neonates with prolonged intubation and underlying bronchopulmonary dysplasia. In our cohort, most clinical features, therapeutic responses and final outcomes of neonates with monomicrobial and polymicrobial VAP did not differ significantly.

Antimicrobial susceptibility of multidrug-resistant Pseudomonas aeruginosa isolated from drinking water and hospitalized patients in Jordan

Pseudomonas aeruginosa (P. aeruginosa) is an important environmental, opportunistic and nosocomial pathogen with a significant threat to public health. The objectives of this study were to determine the in vitro antimicrobial susceptibility patterns of, and antibiotic drug combinations with synergistic effects against P. aeruginosa isolated from drinking water and hospitalized patients in Jordan. A total of 16 P. aeruginosa isolates were obtained from hospitalized patients and 15 were isolated from bottled drinking water were used in the study. Bacterial isolation and identification was performed using routine microbiological methods and confirmed using PCR technique targeting the 16S rDNA gene. The antimicrobial susceptibility patterns were determined by measuring the minimum inhibitory concentration (MIC) using the 2-fold microdilution method. Synergy interaction between various antimicrobials was determined using the checkerboard method and fractional inhibitory concentration index (FICI). The majority of water isolates were sensitive to gentamicin (93.3%), ticarcillin (86.7%) and ciprofloxacin, levofloxacin, amikacin, colistin, piperacillin, azlocillin, aztreonam, ceftazidime and imipenem (100% each). All water isolates (100%) were resistant to amoxicillin, oxytetracycline and doxycycline (93.3% and 86.7, respectively). For the clinical isolates, all (100%) were sensitive to ceftazidime, 81.3% were sensitive to aztreonam, while 62.5% were sensitive to ciprofloxacin, levofloxacin, gentamicin, amikacin, colistin, piperacillin, ticracillin, azlocillin, and imipenem. All clinical isolates (100%) were resistant to oxytetracycline, doxycycline and amoxicillin. Analysis of the checkerboard synergy assay of multi-drug resistant isolates (n=26) showed significant synergism (P ≤ 0.05) when ciprofloxacin or gentamicin were included in the combination. There were no significant differences in synergistic activity between ciprofloxacin and levofloxacin when combined with other antimicrobial agents of the beta-lactams or aminoglycosides classes. There were no significant differences in the synergistic activities between beta lactams - aminoglycoside and beta lactams - fluoroquinolone combinations. Results of this study indicate an alarming widespread presence of multidrug-resistant P. aeruginosa associated with chronic suppurative infections in hospitalized patients and apparently clean drinking water in Jordan. Treatment of clinical suppurative lesions must be based on culture and in vitro susceptibility testing using potent antimicrobial combinations to avoid emergence of resistant strains and to improve the clinical outcome of treated patients.

Prior antimicrobial therapy duration influences causative pathogens identification in ventilator-associated pneumonia

OBJECTIVE

To determine whether prior antimicrobial therapy, divided in recent or current antibiotic treatment, influences the identification rate and/or the type of causative pathogens in patients with suspected episodes of ventilator-acquired pneumonia.

DESIGN

Monocentric retrospective study.

SETTING

Intensive car unit in a universitary hospital.

PATIENTS

230 episodes of ventilator-associated pneumonia with a Clinical Pulmonary Infection Score≥6 were retrospectively evaluated. Based on the antimicrobial treatment regimen, we defined 3 groups: the no antimicrobial treatment group (VAP is suspected in patients that has never received antibiotics during the last 90days), group 2: the current antimicrobial therapy (VAP is suspected under antimicrobial therapy) and group 3: the recent antimicrobial therapy (VAP is suspected whereas an antimicrobial treatment has been used during the last 90days but discontinued for >24h).

INTERVENTION

Bacteriologic analysis using a protected distal sampling with microscopic examination, culture and microbial identification using MALDI-TOF.

MEASUREMENTS AND MAIN RESULTS

Suspected episodes of VAP were sorted as follow: 70 suspected episodes in the no antimicrobial therapy group, 106 suspected episodes in the current antimicrobial therapy group and 54 suspected episodes in the recent antimicrobial therapy group. The rate of positive culture was significantly lower in the current antimicrobial treatment group (group 2) when compared to the recent (group 3) and to the no antimicrobial treatment groups (group 1) (42%, 68% and 86%, respectively). When compared to the recent antibiotherapy group, we observed that current antibiotherapy was significantly associated with a higher rate of MDR positive culture, mainly due to higher rate of MDR Pseudomonas aeruginosa.

CONCLUSION

In patients with a high probability of VAP, current but not recent antibiotic use is associated with a lower rate of positive culture with a higher proportion of MDR pathogens, mostly MDR Pseudomonas aeruginosa.

[Nosocomial pneumonia from a radiological perspective]

Due to the high morbidity and mortality, nosocomial pneumonia represents a serious risk in hospitalized patients. The increased risk of infections with multidrug-resistant (MDR) pathogens makes a timely diagnosis and prompt therapy indispensable. A newly occurring or progressive infiltrate in any patient who has been hospitalized for more than 48 h should be viewed with suspicion. In contrast to community acquired pneumonia (CAP), radiography plays a limited role in the diagnosis of hospital-acquired pneumonia (HAP). This is partly due to the technical challenges in imaging of patients who are in a lying position as well as the numerous other possible differential diagnoses. Careful analysis of the various radiological features, such as temporal progression, distribution and appearance can help to narrow down the differential diagnoses. In the absence of a single gold standard, clinical features and appropriate radiological features in addition to cultures obtained from respiratory secretions can help to maximize the diagnostic efficacy and expedite the treatment with appropriate antibiotic therapy.

The role of rapid multiplex molecular syndromic panels in the clinical management of infections in critically ill patients: an experts-opinion document

Rapid multiplex molecular syndromic panels (RMMSP) (3 or more pathogens and time-to-results < 6 h) allow simultaneous detection of multiple pathogens and genotypic resistance markers. Their implementation has revolutionized the clinical landscape by significantly enhancing diagnostic accuracy and reducing time-to-results in different critical conditions. The current revision is a comprehensive but not systematic review of the literature. We conducted electronic searches of the PubMed, Medline, Embase, and Google Scholar databases to identify studies assessing the clinical performance of RMMSP in critically ill patients until July 30, 2024. A multidisciplinary group of 11 Spanish specialists developed clinical questions pertaining to the indications and limitations of these diagnostic tools in daily practice in different clinical scenarios. The topics covered included pneumonia, sepsis/septic shock, candidemia, meningitis/encephalitis, and off-label uses of these RMMSP. These tools reduced the time-to-diagnosis (and therefore the time-to-appropriate treatment), reduced inappropriate empiric treatment and the length of antibiotic therapy (which has a positive impact on antimicrobial stewardship and might be associated with lower in-hospital mortality), may reduce the length of hospital stay, which could potentially lead to cost savings. Despite their advantages, these RMMSP have limitations that should be known, including limited availability, missed diagnoses if the causative agent or resistance determinants are not included in the panel, false positives, and codetections. Overall, the implementation of RMMSP represents a significant advancement in infectious disease diagnostics, enabling more precise and timely interventions. This document addresses relevant issues related to the use of RMMSP on different critically ill patient profiles, to standardize procedures, assist in making management decisions and help specialists to obtain optimal outcomes.

[Multidrug resistant gram-negative bacteria : Clinical management pathway for patients undergoing elective interventions in visceral surgery]

BACKGROUND

Only a few antibiotics are available for treatment of infections with multidrug resistant gram-negative bacteria (MRGN). The management of patients with MRGN colonization or infection is therefore of great importance with respect to postoperative morbidity and mortality.

OBJECTIVE

This article presents a description of the management pathway for patients with MRGN colonization.

RESULTS

The prevalence of MRGN colonization is increasing, particularly for persons with contact to the healthcare system in endemic regions. The Robert Koch Institute demands an obligatory MRGN screening and isolation of patients with geographic or contact-related exposure risk for colonization with 4MRGN (carbapenemase producers). For patients with elective visceral interventions a prompt sensitive screening before inpatient admission is wise. Strict basic hygiene measures are essential to prevent transmission. Isolation is indicated for patients with 4MRGN and also for patients with 3MRGN in risk areas. Risk patients with unknown status are preemptively isolated. Perioperative antibiotic prophylaxis should be administered as a single dose and in cases of MRGN colonization substances effective against MRGN should be given if necessary. For treatment of secondary/tertiary peritonitis with a risk of MRGN involvement and in hemodynamically instable patients, effective extended spectrum beta-lactamase (ESBL) substances should primarily be used (e.g. tigecycline, carbapenems, ceftolozane/tazobactam and ceftazidim/avibactam). Ceftazidim/avibactam is also a novel therapy option for infections with carbapenamase-producing enterobacteria.

CONCLUSION

The structured implementation of MRGN screening in patients at risk, stringent basic hygiene, targeted isolation and adequate calculated antibiotic therapy are essential measures in the management of the problem of MRGN in visceral surgery.