EUCAST expert rules in antimicrobial susceptibility testing

Salvage strategy for long-term central venous catheter-associated Staphylococcus aureus infections in children: a multicenter retrospective study in France

OBJECTIVES

Catheter removal is recommended in adults with S. aureus central line-associated bloodstream infection (CLABSI) but is controversial in children with long-term central venous catheters (LTCVC). We evaluated the occurrence of catheter salvage strategy (CSS) in children with S. aureus LTCVC-associated CLABSI and assessed determinants of CSS failure.

METHODS

We retrospectively included children (<18 years) with an LTCVC and hospitalized with S. aureus CLABSI in 8 French tertiary care hospitals (2010-2018). CSS was defined as an LTCVC left in place ≥ 72 hours after initiating empiric antibiotic treatment for suspected bacteremia. Characteristics of patients were reviewed, and multivariable logistic regression was performed to identify factors associated with CSS failure (i.e., persistence, recurrence, or complications of bacteremia).

RESULTS

We included 273 episodes of S. aureus LTCVC-associated CLABSI. CSS was chosen in 194 out of 273 (71%) cases and failed in 74 of them (38%). The main type of CSS failure was the persistence of bacteremia (39 out of 74 cases, 53%). Factors independently associated with CSS failure were: history of catheter infection (adjusted odds ratio [aOR] 3.18, 95% confidence interval [95%CI] 1.38-7.36), CLABSI occurring on an implantable venous access device (aOR 7.61, 95%CI 1.98-29.20) when compared with tunneled-cuffed CVC, polymicrobial CLABSI (aOR 3.45, 95%CI 1.25-9.50), and severe sepsis at the initial stage of infection (aOR 4.46, 95%CI 1.18-16.82).

CONCLUSIONS

CSS was frequently chosen in children with S. aureus LTCVC-associated CLABSI, and failure occurred in one-third of cases. The identified risk factors may help clinicians identify children at risk for CSS failure.

Maximally stable extremal regions-based algorithm for automatic interpretation of disc-diffusion antibiotic sensitivity test

Antibiotic resistance causes a major threat to patients suffering from infectious diseases. Accurate and timely assessment of Antibiotic Susceptibility Test (AST) is of great importance to ensure adequate treatment for patients and for epidemiological monitoring. Disc Diffusion Test (DDT) is a standard and widely used method for AST. Manual interpretation of DDT results is a tedious task and susceptible to human errors. Computer vision-based automated interpretation of DDT results will speed up the process and reduces the manpower requirement. This would assist the physician to initiate the antibiotic treatment for the patients on time and results in saving the patient's life. The crucial step in automatic interpretation of DDT result is to measure and present the diameter of zone of inhibition without manual intervention. The existing methods require manual interventions at various stages during inhibition zone diameter measurement for some typical cases. This issue is addressed in the present work through maximally stable extremal regions (MSER) based algorithm. Dataset consisting of 60 agar plate images that includes different agar medium, images having different resolution and visual quality is used to validate the proposed method. Experimental results demonstrated that there is a strong correlation between standard method and the proposed method.

Genomic insights into the expansion of carbapenem-resistant Klebsiella pneumoniae within Portuguese hospitals

Carbapenem-resistant Klebsiella pneumoniae (CR-KP) are a public health concern, causing infections with a high mortality rate, limited therapeutic options and challenging infection control strategies. In Portugal, the CR-KP rate has increased sharply, but the factors associated with this increase are poorly explored. In order to address this question, phylogenetic and resistome analysis were used to compare the draft genomes of 200 CR-KP isolates collected in 2017-2019 from five hospitals in the Lisbon region, Portugal. Most CR-KP belonged to sequence type (ST) 13 (29%), ST17 (15%), ST348 (13%), ST231 (12%) and ST147 (7%). Carbapenem resistance was conferred mostly by the presence of KPC-3 (74%) or OXA-181 (18%), which were associated with IncF/IncN and IncX plasmids, respectively. Almost all isolates were multi-drug resistant, harbouring resistance determinants to aminoglycosides, beta-lactams, trimethoprim, fosfomycin, quinolones and sulphonamides. In addition, 11% of isolates were resistant to colistin. Colonizing and infecting isolates were highly related, and most colonized patients (89%) reported a previous hospitalization. Moreover, among the 171 events of cross-dissemination identified by core genome multi-locus sequence typing data analysis (fewer than five allelic differences), 41 occurred between different hospitals and 130 occurred within the same hospital. The results suggest that CR-KP dissemination in the Lisbon region results from acquisition of carbapenemases in mobile genetic elements, influx of CR-KP into the hospitals by colonized ambulatory patients, and transmission of CR-KP within and between hospitals. Prudent use of carbapenems, patient screening at hospital entry, and improvement of infection control are needed to decrease the burden of CR-KP infection in Portugal.

Microbial diagnostics in periodontal diseases

Microbial analytical methods have been instrumental in elucidating the complex microbial etiology of periodontal diseases, by shaping our understanding of subgingival community dynamics. Certain pathobionts can orchestrate the establishment of dysbiotic communities that can subvert the host immune system, triggering inflammation and tissue destruction. Yet, diagnosis and management of periodontal conditions still rely on clinical and radiographic examinations, overlooking the well-established microbial etiology. This review summarizes the chronological emergence of periodontal etiological models and the co-evolution with technological advances in microbial detection. We additionally review the microbial analytical approaches currently accessible to clinicians, highlighting their value in broadening the periodontal assessment. The epidemiological importance of obtaining culture-based antimicrobial susceptibility profiles of periodontal taxa for antibiotic resistance surveillance is also underscored, together with clinically relevant analytical approaches to guide antibiotherapy choices, when necessary. Furthermore, the importance of 16S-based community and shotgun metagenomic profiling is discussed in outlining dysbiotic microbial signatures. Because dysbiosis precedes periodontal damage, biomarker identification offers early diagnostic possibilities to forestall disease relapses during maintenance. Altogether, this review highlights the underutilized potential of clinical microbiology in periodontology, spotlighting the clinical areas most conductive to its diagnostic implementation for enhancing prevention, treatment predictability, and addressing global antibiotic resistance.

External quality assessment schemes in bacteriology support public health in Germany-results from 2006 to 2023

External Quality Assessment schemes (EQAS) are mandatory to ensure quality standards in diagnostic methods and achieve laboratory accreditation. As host institution for two German culture-based bacteriology EQAS (RV-A and RV-B), we investigated the obtained data of 590 up to 720 surveys per year in RV-A and 2,151 up to 2,929 in RV-B from 2006 to 2023. As educational instruments, they function to review applied methodology and are valuable to check for systemic- or method-dependent failures in microbiology diagnostics or guidelines. Especially, containment of multi-resistant bacteria in times of rising antibiotic resistance is one major point to assure public health. The correct identification and reporting of these strains is therefore of high importance to achieve this goal. Moreover, correct antimicrobial susceptibility testing (AST) per se is important for selecting appropriate therapy, to restrict broad-spectrum antibiotics and minimize resistance development. The reports of participating laboratories displayed a high level of correct identification results in both schemes with mostly consistent failure rates around 2.2% (RV-A) and 3.9% (RV-B) on average. In contrast, results in AST revealed increasing failure rates upon modification of AST requirements concerning adherence to standards and subsequent bacterial species-specific evaluation. Stratification on these periods revealed in RV-A a moderate increase from 1.3% to 4.5%, while in RV-B failure rates reached 14% coming from 4.3% on average. Although not mandatory, subsequent AST evaluation and consistent reporting are areas of improvement to benefit public health.

Assessment of antimicrobial resistance, biofilm formation, and surface modification potential in hospital strains of Pseudomonas aeruginosa and Klebsiella pneumoniae

The occurrence of healthcare-associated infections is a multifactorial phenomenon related to hospital space contamination by bacteria. The ESKAPE group, specifically Pseudomonas aeruginosa and Klebsiella pneumoniae, play a relevant role in the occurrence of these infections. Therefore, comprehensive research is needed to identify characteristics that justify the prevalence of these species in the healthcare environment. In this line, the study aimed to determine the antimicrobial resistance, biofilm formation, and the potential for polymer degradation in a collection of 33 P. aeruginosa strains and 2 K. pneumoniae strains sampled from various equipment and non-critical surfaces in a Portuguese hospital. Antimicrobial susceptibility tests revealed that none of the strains was categorized as multidrug-resistant (non-MDR). An assessment of their biofilm-forming capabilities indicated that 97 % of the strains exhibited biofilm-producing characteristics. Notably, within this group, the majority of P. aeruginosa and half of K. pneumoniae strains were classified as strong biofilm producers. Furthermore, the strains were evaluated for their potential to cause damage or change medical devices, namely infusion sets, nasal cannula, and urinary catheters. Three P. aeruginosa strains, two strong and one moderate biofilm producers, showed the highest ability to modify surfaces of the nasal cannula and infusion sets. Additionally, the Chi-square test revealed a statistically significant relationship between the presence of P. aeruginosa strains and the water accession spots. In conclusion, this work suggests that bacteria from this group hold a significant ability to grow in the healthcare environment through the degradation of non-critical materials. This suggests a potential concern for the persistence and proliferation of these organisms in hospital environments, emphasizing the importance of robust infection control measures to mitigate the risks associated with bacterial growth on such surfaces.

Urosepsis 30-day mortality, morbidity, and their risk factors: SERPENS study, a prospective, observational multi-center study

PURPOSE

To provide a descriptive report of mortality and morbidity in the first 30 days of diagnosis of urosepsis. Secondary aim is to identify risk factors of unfavourable outcomes.

METHODS

Prospective observational multicentre cohort study conducted from September 2014 to November 2018 in European hospitals. Adult patients (≥ 18 years) diagnosed with acute urosepsis according to Sepsis-2 criteria with confirmed microbiological infection were included. Outcomes were classified in one of four health states: death, multiple organ failure, single organ failure, and recovery at day 30 from onset of urosepsis. Descriptive statistics and ordinal logistic regression analysis was performed.

RESULTS

Three hundred and fifty four patients were recruited, and 30-day mortality rate was 2.8%, rising to 4.6% for severe sepsis. All patients who died had a SOFA score of ≥ 2 at diagnosis. Upon initial diagnosis, 79% (n = 281) of patients presented with OF. Within 30 days, an additional 5% developed OF, resulting in a total of 84% affected. Charlson score (OR 1.14 CI 1.01-1.28), patients with respiratory failure at baseline (OR 2.35, CI 1.32-4.21), ICU admission within the past 12 months (OR 2.05, CI 1.00-4.19), obstruction causative of urosepsis (OR 1.76, CI 1.02-3.05), urosepsis with multi-drug-resistant(MDR) pathogens (OR 2.01, CI 1.15-3.53), and SOFA baseline score ≥ 2 (OR 2.74, CI 1.49-5.07) are significantly associated with day 30 outcomes (OF and death).

CONCLUSIONS

Impact of comorbidities and MDR pathogens on outcomes highlights the existence of a distinct group of patients who are prone to mortality and morbidity. These findings underscore the need for the development of pragmatic classifications to better assess the severity of UTIs and guide management strategies.

STUDY REGISTRATION

Clinicaltrials.gov registration number NCT02380170.

Antibacterial Activity of Various Morphologies of Films Based on Guanidine Derivatives of Pillar[5]arene: Influence of the Nature of One Substitute on Self-assembly

The progress of the pillar[5]arene chemistry allowed us to set out a new concept on application of the supramolecular assemblies to create antimicrobial films with variable surface morphologies and biological activities. Antibacterial films were derived from the substituted pillar[5]arenes containing nine pharmacophoric guanidine fragments and one thioalkyl substituent. Changing the only thioalkyl fragment in the macrocycle structure made it possible to control the biological activity of the resulting antibacterial coating. Pretreatment of the surface with aqueous solution of the amphiphilic pillar[5]arenes reduced the biofilm thickness by 56 ± 10% of Gram-positive Staphylococcus aureus in the case of the pillar[5]arene containing a thiooctyl fragment and by 52 ± 7% for the biofilm of Gram-negative Klebsiella pneumoniae in the case of pillar[5]arene containing a thiooctadecyl fragment. Meanwhile, the cytotoxicity of the synthesized macrocycles was examined at a concentration of 50 μg/mL, which was significantly lower than that of bis-guanidine-based antimicrobial preparations.

Prospective observational pilot study of the T2Resistance panel in the T2Dx system for detection of resistance genes in bacterial bloodstream infections

Early initiation of antimicrobial therapy targeting resistant bacterial pathogens causing sepsis and bloodstream infections (BSIs) is critical for a successful outcome. The T2Resistance Panel (T2R) detects the following resistance genes within organisms that commonly cause BSIs directly from patient blood samples: blaKPC, blaCTXM-14/15, blaNDM/bla/IMP/blaVIM, blaAmpC, blaOXA, vanA, vanB, and mecA/mecC. We conducted a prospective study in two major medical centers for the detection of circulating resistance genes by T2R in patients with BSIs. T2R reports were compared to antimicrobial susceptibility testing (AST), phenotypic identification, and standard molecular detection assays. Among 59 enrolled patients, 25 resistance genes were identified: blaKPC (n = 10), blaNDM/bla/IMP/blaVIM (n = 5), blaCTXM-14/15 (n = 4), blaAmpC (n = 2), and mecA/mecC (n = 4). Median time-to-positive-T2R in both hospitals was 4.4 hours [interquartile range (IQR): 3.65-4.97 hours] in comparison to that for positive blood cultures with final reporting of AST of 58.34 h (IQR: 45.51-111.2 hours; P < 0.0001). The sensitivity of T2R to detect the following genes in comparison to AST was 100% for blaCTXM-14/15, blaNDM/bla/IMP/blaVIM, blaAmpC, mecA/mecC and 87.5% for blaKPC. When monitored for the impact of significant antimicrobial changes, there were 32 events of discontinuation of unnecessary antibiotics and 17 events of escalation of antibiotics, including initiation of ceftazidime/avibactam in six patients in response to positive T2R results for blaKPC. In summary, T2R markers were highly sensitive for the detection of drug resistance genes in patients with bacterial BSIs, when compared with standard molecular resistance detection systems and phenotypic identification assays while significantly reducing by approximately 90% the time to detection of resistance compared to standard methodology and impacting clinical decisions for antimicrobial therapy.

IMPORTANCE

This is the first reported study to our knowledge to identify key bacterial resistance genes directly from the bloodstream within 3 to 5 hours in patients with bloodstream infections and sepsis. The study further demonstrated a direct effect in modifying initial empirical antibacterial therapy in response to T2R signal to treat resistant bacteria causing bloodstream infections and sepsis.

Metal-based nanoparticles: an alternative treatment for biofilm infection in hard-to-heal wounds

Metal-based nanoparticles (MNPs) are promoted as effective compounds in the treatment of bacterial infections and as possible alternatives to antibiotics. These MNPs are known to affect a broad spectrum of microorganisms using a multitude of strategies, including the induction of reactive oxygen species and interaction with the inner structures of the bacterial cells. The aim of this review was to summarise the latest studies about the effect of metal-based nanoparticles on pathogenic bacterial biofilm formed in wounds, using the examples of Gram-positive bacterium Staphylococcus aureus and Gram-negative bacterium Pseudomonas aeruginosa, as well as provide an overview of possible clinical applications.

Intervention with impact: Reduced isolation of methicillin-resistant Staphylococcus pseudintermedius from dogs following the introduction of antimicrobial prescribing legislation in Germany

BACKGROUND

Legislation was introduced in Germany in 2018, requiring bacterial culture and antimicrobial susceptibility testing before the prescription of fluoroquinolones and third-generation cephalosporins to dogs. We hypothesised that, following this intervention, the number of clinical samples testing positive for methicillin-resistant Staphylococcus pseudintermedius (MRSP) would reduce.

METHODS

Reports of S. pseudintermedius isolated from canine clinical samples by three German veterinary diagnostic microbiology laboratories during the 38 months before the introduction of the legislation and the 46 months after were compared. Bacterial identification was performed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, and antimicrobial susceptibility testing followed recognised recommendations but with changes during the study period.

RESULTS

Among a total of 120,571 S. pseudintermedius isolates, MRSP accounted for 7.1% overall. Following the legislative intervention, monthly submissions yielding S. pseudintermedius increased at all three laboratories. The MRSP percentage was lower in the period after the intervention in two of the three laboratories (p < 0.001); in the third laboratory, there was no change between periods, but a year-on-year reduction in MRSP percentages occurred after the intervention (p = 0.0004).

LIMITATIONS

Changing susceptibility testing methods limited the direct comparison of resistance patterns among laboratories.

CONCLUSION

The reduction in MRSP in canine clinical samples following the introduction of this legislation suggests a positive impact of compulsory laboratory testing on reducing antimicrobial resistance.

Antimicrobial Resistance Profile of Group B Streptococci Colonization in a Sample Population of Pregnant Women from Romania

Group B Streptococcus (GBS) represents one of the leading causes of life-threatening invasive disease in pregnant women and neonates. Rates of GBS colonization vary by region, but studies on maternal GBS status are limited in Romania. This study aims to identify the prevalence of colonization with GBS and whether the obstetrical characteristics are statistically associated with the study group's antimicrobial susceptibility patterns of tested GBS strains. This observational study was conducted between 1 May and 31 December 2021 at The Department of Obstetrics and Gynecology at Elias University Emergency Hospital (EUEH) in Bucharest, Romania. A total of 152 samples were positive for GBS and included in the study according to the inclusion criteria. As a result, the prevalence of colonized patients with GBS was 17.3%. GBS isolated in this population had the highest resistance to erythromycin (n = 38; 25%), followed by clindamycin (n = 36; 23.7%). Regarding the susceptibility patterns of tested strains to penicillin, the 152 susceptible strains had MIC breakpoints less than 0.06 μg/μL. The susceptibility patterns of tested strains to linezolid indicated three resistant strains with low levels of resistance (MICs ranging between 2 and 3 μg/μL). Multidrug resistance (at least three antibiotic classes) was not observed. In conclusion, although GBS naturally displays sensitivity to penicillin, the exact bacterial susceptibility testing should be performed in all cases where second-line therapy is taken into consideration for treatment. We acknowledge the need for future actions to limit multidrug-resistant bacteria.

Pediatric intracranial empyema complicating otogenic and sinogenic infection

OBJECTIVE

To describe and compare clinical and microbiological features, surgical and medical management, and outcomes of children with otogenic and sinogenic intracranial empyema (IE) in an institution with an established multidisciplinary protocol. To use the study findings to inform and update the institutional algorithm.

METHODS

Retrospective analysis was carried out on the electronic healthcare records of all children with oto-sinogenic IE admitted in a 5-year period.

RESULTS

A total of 76 patients were identified and treated according to an institutional protocol. Two distinct groups were identified: intracranial empyema related to otogenic infection (OI-IE, n = 36) or sinogenic infection (SI-IE, n = 40). SI-IE was seen in older children and had a significantly higher morbidity. Sub-dural IE was seen in a minority (n = 16) and only in SI-IE and required urgent collaborative ENT-neurosurgery. Extra-dural IE occurred more frequently and was seen in both SI-IE and OI-IE. No death and overall low morbidity were observed. Particularities found in SI-IE and OI-IE groups (as thrombosis, microbiology, antibiotic treatment, duration and outcome) permitted the delineation of these groups in our updated algorithm.

CONCLUSION

The presence of a collaborative multidisciplinary protocol permits the step-wise co-ordination of care for these complex patients in our institution. All patients received prompt imaging, urgent surgical intervention, and antibiotic treatment. Microbiological identification was possible for each patient and antibiotic rationalization was permitted through use of Polymerase chain reaction (PCR) testing in cases of sterile cultures. Of note, intracranial empyema related to sinogenic infection is shown to have significantly more severe clinical presentation, a higher morbidity, and a longer duration of antibiotic therapy than that related to otogenic infection. Study findings allowed for the update and clarification of the institutional protocol, which now clearly demarcates the clinical presentation, biological evidence, radiology, surgical and medical treatments in children with oto-sinogenic IE.

Carvacrol and Thymol Content Affects the Antioxidant and Antibacterial Activity of Origanum compactum and Thymus zygis Essential Oils

Essential oils are of great interest due to their potent pharmaceutical and biological activities. In this study, essential oils extracted from Origanum compactum and Thymus zygis originating from the Middle Atlas of Morocco were investigated. Their chemical compositions were analyzed using gas chromatography and mass spectrometry, while the assessment of the trapping power of the radical (DPPH: 1,1-diphenyl-2-picrylhydrazyl) and the reducing antioxidant potential of ferric ions (FRAP: Ferric Reducing Antioxidant Power) were performed in order to evaluate the antioxidant activity. Their antibacterial potency was tested against six bacterial strains through the disk diffusion method. The chromatography analyses of the extracted essential oils highlighted the presence of two main components, namely carvacrol at 75.70% in O. compactum and thymol at 40.67% in T. zygis. The antioxidant activity tests showed that both essential oils demonstrated a significant antioxidant activity comparable to the positive control (e.g., ascorbic acid). The antibacterial activity results showed a strong antimicrobial effect for both essential oils, compared to synthetic antibiotics. This study affirms the presence of bioactive components with interesting antioxidant and antibacterial activities in the essential oils extracted from Origanum compactum and Thymus zygis, which could find several applications in the food and pharmaceutical industries through the substitution of synthetic antioxidants and antibiotics.

The Antimicrobial Potential of the Hop (Humulus lupulus L.) Extract against Staphylococcus aureus and Oral Streptococci

Plant extracts are in the focus of the pharmaceutical industry as potential antimicrobials for oral care due to their high antimicrobial activity coupled with low production costs and safety for eukaryotic cells. Here, we show that the extract from Hop (Humulus lupulus L.) exhibits antimicrobial activity against Staphylococcus aureus and Streptococci in both planktonic and biofilm-embedded forms. An extract was prepared by acetone extraction from hop infructescences, followed by purification and solubilization of the remaining fraction in ethanol. The effect of the extract on S. aureus (MSSA and MRSA) was comparable with the reference antibiotics (amikacin, ciprofloxacin, and ceftriaxone) and did not depend on the bacterial resistance to methicillin. The extract also demonstrated synergy with amikacin on six S. aureus clinical isolates, on four of six isolates with ciprofloxacin, and on three of six isolates with ceftriaxone. On various Streptococci, while demonstrating lower antimicrobial activity, an extract exhibited a considerable synergistic effect in combination with two of three of these antibiotics, decreasing their MIC up to 512-fold. Moreover, the extract was able to penetrate S. aureus and S. mutans biofilms, leading to almost complete bacterial death within them. The thin-layer chromatography and LC-MS of the extract revealed the presence of prenylated flavonoids (2',4',6',4-tetrahydroxy-3'-geranylchalcone) and acylphloroglucides (cohumulone, colupulone, humulone, and lupulone), apparently responsible for the observed antimicrobial activity and ability to increase the efficiency of antibiotics. Taken together, these data suggest an extract from H. lupulus as a promising antimicrobial agent for use both as a solely antiseptic and to potentiate conventional antimicrobials.

Second-Line Antibiotic Agents in Patient-Reported Penicillin or Cephalosporin Allergy Have No Negative Impact on Antibiotic Resistance After Hip and Knee Arthroplasty

BACKGROUND

The aim of the present study was to compare causative bacteria and their antibiotic resistance profiles in patients developing a periprosthetic joint infection (PJI) based on preoperative prophylactic antibiotic regimens in primary total hip (THA) and primary total and unicompartmental knee arthroplasty (TKA/UKA).

METHODS

We reviewed all cases of PJI occurring after primary THA and primary TKA/UKA, between 2011 and 2020 in a tertiary referral hospital. The standard preoperative prophylactic antibiotic for primary joint arthroplasty was cefuroxime and recommended second-line agent was clindamycin. Patients were divided by the replaced joint and analyzed independently.

RESULTS

In the THA group, culture-positive PJI was detected in 61 of 3,123 (2.0%) cefuroxime-administered cases and 6 of 206 (2.9%) noncefuroxime-administered cases. In the TKA/UKA group, culture positive PJI was identified in 21 of 2,455 (0.9%) cefuroxime-administered cases and in 3 of 211 (1.4%) noncefuroxime administered cases. The most commonly isolated bacteria in both groups were coagulase negative staphylococci (CNS). There were no statistically significant differences of pathogen spectrum depending on the preoperative antibiotic regimen detected. Antibiotic resistance of isolated bacteria was significantly different in 4 of 27 (14.8%) analyzed antibiotics in THA and in 3 of 22 (13.6%) analyzed antibiotics in TKA/UKA. In all cohorts, a high occurrence of oxacillin-resistant CNS (50.0 to 100.0%) and clindamycin-resistant CNS (56.3 to 100.0%) has been observed.

CONCLUSION

The use of the second-line antibiotic did not influence the pathogen spectrum or antibiotic resistance. However, an alarmingly high proportion of CNS strains was resistant to clindamycin.

Profiling Antibiotic Susceptibility among Distinct Enterococcus faecalis Isolates from Dental Root Canals

Enterococcus faecalis, a leading multi-resistant nosocomial pathogen, is also the most frequently retrieved species from persistently infected dental root canals, suggesting that the oral cavity is a possible reservoir for resistant strains. However, antimicrobial susceptibility testing (AST) for oral enterococci remains scarce. Here, we examined the AST profiles of 37 E. faecalis strains, including thirty-four endodontic isolates, two vanA-type vancomycin-resistant isolates, and the reference strain ATCC-29212. Using Etest gradient strips and established EUCAST standards, we determined minimum inhibitory concentrations (MICs) for amoxicillin, vancomycin, clindamycin, tigecycline, linezolid, and daptomycin. Results revealed that most endodontic isolates were susceptible to amoxicillin and vancomycin, with varying levels of intrinsic resistance to clindamycin. Isolates exceeding the clindamycin MIC of the ATCC-29212 strain were further tested against last-resort antibiotics, with 7/27 exhibiting MICs matching the susceptibility breakpoint for tigecycline, and 1/27 reaching that of linezolid. Both vanA isolates confirmed vancomycin resistance and demonstrated resistance to tigecycline. In conclusion, while most endodontic isolates remained susceptible to first-line antibiotics, several displayed marked intrinsic clindamycin resistance, and MICs matched tigecycline's breakpoint. The discovery of tigecycline resistance in vanA isolates highlights the propensity of clinical clone clusters to acquire multidrug resistance. Our results emphasize the importance of implementing AST strategies in dental practices for continued resistance surveillance.

Terpene-Functionalized Fluoroquinolones as Potential Antimicrobials: Synthesis and Properties

This study was the first to synthesize terpene-containing conjugates of fluoroquinolones, ciprofloxacin and norfloxacin, and to evaluate their antibacterial activity against gram-positive methicillin sensitive (MSSA) and methicillin resistant (MRSA) S. aureus, gram-negative P. aeruginosa as well as antifungal activity against C. albicans. The ability of obtained fluoroquinolones to inhibit S. aureus growth was found to depend upon the presence of a linker separating the bulky terpene and fluoroquinolone fragments, and this activity diminished with increasing its length. The highest activity against MSSA was demonstrated by ciprofloxacin derivatives with campholenic (MIC 1 μg/mL) and 2-(isobornan-2-yl-sulfanyl)acetyl (MIC 0.5 μg/mL) substituents. The compound with the last fragment showed high activity against MRSA (MIC 8 μg/mL). The terpene-functionalized norfloxacin derivatives generally proved to be less active than those containing ciprofloxacin fragment. Camphor-10-sulfonylamide derivative with the ciprofloxacin fragment was the only one of all compounds that showed high antifungal activity against C. albicans (8 μg/mL). The study presents data on docking fluoroquinolones to S. aureus DNA gyrase to explain the reasons for manifestation or disappearance of antibacterial activity. The cytotoxicity of fluoroquinolones that showed any antimicrobial activity was investigated against bovine primary lung cells, and they were found to be not toxic in most cases.

Synthesis and biological evaluation of fluoroquinolones containing a pyridoxine derivatives moiety

We report herein the design, synthesis and biological evaluation of series of 7-substituted fluoroquinolones with pyridoxine derivatives. In vitro screening of antibacterial activity and toxicity of 39 synthesized fluoroquinolones defined compounds 7 and 28 as lead compounds for further investigations. On various clinical isolates lead compounds 7 and 28 exhibited antibacterial activity comparable with reference fluoroqinolones. Mutagenic effects haven't been observed for these compounds in SOS-chromotest. Compound 7 are non-toxic in vivo on mice (LD50 > 2000 mg/kg, oral) and rats (LD50 > 2000 mg/kg, oral). Compound 28 was more toxic (LD50 = 474 mg/kg, oral, mice). Moreover compound 7 showed greater in vivo efficacy compared to ciprofloxacin in a murine model of staphylococcal sepsis. Taken together the described active compound are promising candidate for preclinical trials.

Extended-Spectrum β-Lactamases (ESBL): Challenges and Opportunities

The rise of antimicrobial resistance, particularly from extended-spectrum β-lactamase producing Enterobacteriaceae (ESBL-E), poses a significant global health challenge as it frequently causes the failure of empirical antibiotic therapy, leading to morbidity and mortality. The E. coli- and K. pneumoniae-derived CTX-M genotype is one of the major types of ESBL. Mobile genetic elements (MGEs) are involved in spreading ESBL genes among the bacterial population. Due to the rapidly evolving nature of ESBL-E, there is a lack of specific standard examination methods. Carbapenem has been considered the drug of first choice against ESBL-E. However, carbapenem-sparing strategies and alternative treatment options are needed due to the emergence of carbapenem resistance. In South Asian countries, the irrational use of antibiotics might have played a significant role in aggravating the problem of ESBL-induced AMR. Superbugs showing resistance to last-resort antibiotics carbapenem and colistin have been reported in South Asian regions, indicating a future bleak picture if no urgent action is taken. To counteract the crisis, we need rapid diagnostic tools along with efficient treatment options. Detailed studies on ESBL and the implementation of the One Health approach including systematic surveillance across the public and animal health sectors are strongly recommended. This review provides an overview of the background, associated risk factors, transmission, and therapy of ESBL with a focus on the current situation and future threat in the developing countries of the South Asian region and beyond.

Speaking of sepsis: semantics, syntax, and slang

Medical language is in a constant state of evolution. Its grammar and vocabulary are not fixed by rigid rules. The interdisciplinary field of sepsis has become a meeting point for new insights arising from advances in systems biology, epidemiology, mechanistic understandings of disease process and antimicrobial interventions. This convergence has gained from our recent experience of SARS-CoV-2 infection and COVID-19 and possibilities inferred from emerging information technology. Biomedical descriptors have diverged along disciplinary lines creating an unfortunate disconnect between clinical and laboratory-based terminology. The resulting confusion between clinically determined sepsis and laboratory verified bloodstream infection raises practical questions that affect daily operational processes in the ward, clinic and laboratory. There is an urgent need to understand how the clinical sepsis pathway and corresponding clinical laboratory workflow can be better aligned as a single coherent entity. There is also an implicit need to understand how this process should produce actionable information in a timely and orderly manner, and identify residual obselete terminology that has crept into common usage. A widely accepted sepsis epistemology, ontology and heuristic will help us improve our clinical management of sepsis.

Need assessment for HIV drug resistance testing and landscape of current and future technologies in low- and middle-income countries

Resistance to antiretroviral drugs used to treat HIV is an important and evolving concern, particularly in low- and middle-income countries (LMICs) which have been impacted to the greatest extent by the HIV pandemic. Efforts to monitor the emergence and transmission of resistance over the past decade have shown that drug resistance-especially to the nucleoside analogue and non-nucleoside reverse transcriptase inhibitors-can (and have) increased to levels that can jeopardize the efficacy of available treatment options at the population level. The global shift to integrase-based regimens as the preferred first-line therapy as well as technological advancements in the methods for detecting resistance have had an impact in broadening and diversifying the landscape of and use case for HIV drug resistance testing. This review estimates the potential demand for HIV drug resistance tests, and surveys current testing methodologies, with a focus on their application in LMICs.

Antimicrobial susceptibility pattern of extended-spectrum beta-lactamase-producing uropathogens in aminu Kano teaching hospital, Northwestern Nigeria

Background

UTI is the most common nosocomial infection among hospitalized patients. Emerging increasing resistance has been observed among uropathogens of the family enterobacterales. Extended spectrum beta lactamase genes encode for multidrug resistance and unrestricted use of antibiotics in hospitals provides an environment for spread of infections with limited treatment options. This necessitates therapies based on culture and antimicrobial sensitivity to improve patients' outcomes We aimed to determine susceptibility pattern of ESBL uropathogens among hospitalized patients in Aminu Kano Teaching Hospital, Kano.

Methodology

Three hundred and eighty-nine urine samples were obtained from in-patients with UTI between April 2020 and April 2021. Five samples were rejected and remaining analyzed. Susceptibility testing was done by modified Kirby Bauer technique. Clinical Laboratory Standards Institute guidelines 2019 (CLSI 2019) and the European Committee on Antimicrobial Susceptibility testing guidelines version 2 (EUCAST version 2) were used for screening and confirmation of ESBL production respectively.

Results

Of the 384-urine processed, 105 (27.3%) were gram negatives and 81 were Enterobacterales, Isolation rates were E. coli-55.6%, K. pneumoniae-29.6%, Citrobacter spp.-12.3%, P. mirabilis-1.2% and Morganella spp.-1.2%. Among Enterobacterales, 32 (39.5%) were ESBL producers. Prevalence of ESBL were 62.5% for Escherichia coli, 28.1% for Klebsiella pneumoniae and 9.4% for Citrobacter species. Susceptibility showed that ESBL-producing Isolates were highly susceptible to amikacin (96.9%). Resistance to other antibiotics varied from 3.1% to 100%.

Conclusion

We recommend strengthening laboratory capacity, antibiotics stewardship and Infection control to prevent spread of resistant pathogens including ESBLs.

Fluorescent optotracers for bacterial and biofilm detection and diagnostics

Effective treatment of bacterial infections requires methods that accurately and quickly identify which antibiotic should be prescribed. This review describes recent research on the development of optotracing methodologies for bacterial and biofilm detection and diagnostics. Optotracers are small, chemically well-defined, anionic fluorescent tracer molecules that detect peptide- and carbohydrate-based biopolymers. This class of organic molecules (luminescent conjugated oligothiophenes) show unique electronic, electrochemical and optical properties originating from the conjugated structure of the compounds. The photophysical properties are further improved as donor-acceptor-donor (D-A-D)-type motifs are incorporated in the conjugated backbone. Optotracers bind their biopolymeric target molecules via electrostatic interactions. Binding alters the optical properties of these tracer molecules, shown as altered absorption and emission spectra, as well as ON-like switch of fluorescence. As the optotracer provides a defined spectral signature for each binding partner, a fingerprint is generated that can be used for identification of the target biopolymer. Alongside their use for in situ experimentation, optotracers have demonstrated excellent use in studies of a number of clinically relevant microbial pathogens. These methods will find widespread use across a variety of communities engaged in reducing the effect of antibiotic resistance. This includes basic researchers studying molecular resistance mechanisms, academia and pharma developing new antimicrobials targeting biofilm infections and tests to diagnose biofilm infections, as well as those developing antibiotic susceptibility tests for biofilm infections (biofilm-AST). By iterating between the microbial world and that of plants, development of the optotracing technology has become a prime example of successful cross-feeding across the boundaries of disciplines. As optotracers offers a capacity to redefine the way we work with polysaccharides in the microbial world as well as with plant biomass, the technology is providing novel outputs desperately needed for global impact of the threat of antimicrobial resistance as well as our strive for a circular bioeconomy.

Accuracy of T2 magnetic resonance assays as point-of-care methods in the intensive care unit

BACKGROUND

Novel molecular diagnostic methods are being evaluated in order to expedite pathogen identification in patients with bacteraemia.

AIMS

To evaluate the feasibility and diagnostic accuracy of the T2 magnetic resonance (T2MR) assays - T2 Bacteria (T2B) and T2 Resistance (T2R) - as point-of-care tests in the intensive care unit compared with blood-culture-based tests.

METHODS

Prospective cross-sectional study of consecutive patients with suspected bacteraemia. Diagnostic accuracy was evaluated using blood culture as the reference method.

FINDINGS

In total, 208 cases were included in the study. The mean time from sampling to report was lower for the T2MR assays compared with blood-culture-based methods (P<0.001). The rate of invalid reports was 6.73% for the T2B assay and 9.9% for the T2R assay. For the T2B assay, overall positive percentage agreement (PPA) was 84.6% [95% confidence interval (CI) 71.9-93.1%], negative percentage agreement (NPA) was 64.3% (95% CI 55.4-72.6%), positive predictive value (PPV) was 48.9% (95% CI 42.5-55.3%) and negative predictive value (NPV) was 91.2% (95% CI 84.4-95.2%). Cohen's kappa coefficient was 0.402. For the T2R assay, overall PPA was 80% (95% CI 51.9-95.7%), NPA was 69.2% (95% CI 54.9-81.3%), PPV was 42.9% (95% CI 31.7-54.8%) and NPV was 92.3% (95% CI 81.1-97.1%). Cohen's kappa coefficient was 0.376.

CONCLUSION

T2MR assays have high NPV for rapid exclusion of bacteraemia, and could potentially assist with antimicrobial stewardship when applied as point-of-care diagnostic tests in the intensive care unit.

Antibiotic resistance in bloodstream isolates from high-complexity paediatric units in Madrid, Spain: 2013-2021

BACKGROUND

Antimicrobial resistance (AMR) has become a significant challenge in high-complexity healthcare settings.

AIM

To evaluate the prevalence of AMR in bloodstream isolates from high-complexity paediatric units in Spain over a nine-year period.

METHODS

A retrospective observational multicentre study was conducted in three tertiary hospitals, analysing bloodstream isolates from patients aged <18 years admitted to the paediatric intensive care, neonatology, and oncology-haematology units between 2013 and 2021. Demographics, antimicrobial susceptibility, and resistance mechanisms were analysed in two periods (2013-2017 and 2017-2021).

FINDINGS

In all, 1255 isolates were included. AMR was more prevalent in older patients and those admitted to the oncology-haematology unit. Multidrug resistance was observed in 9.9% of Gram-negative bacteria (GNB); 20.0% of P. aeruginosa vs 8.6% of Entero-bacterales (P < 0.001), with an increase in Enterobacterales from 6.2% to 11.0% between the first and the second period (P = 0.021). Difficult-to-treat resistance was observed in 2.7% of GNB; 7.4% of P. aeruginosa vs 1.6% of Enterobacterales (P < 0.001), with an increasing trend in Enterobacterales from 0.8% to 2.5% (P = 0.076). Carbapenem resistance among Enterobacterales increased from 3.5% to 7.2% (P = 0.029), with 3.3% producing carbapenemases (67.9% VIM). Meticillin resistance was observed in 11.0% of S. aureus and vancomycin resistance in 1.4% of Enterococcus spp., with both rates remaining stable throughout the study period.

CONCLUSION

This study reveals a high prevalence of AMR in high-complexity paediatric units. Enterobacterales showed a concerning increasing trend in resistant strains, with higher rates among older patients and those admitted to oncology-haematology units.

The bacterial profile and antibiotic susceptibility pattern in respiratory tract samples from art-experienced HIV-positive adults in Uganda

INTRODUCTION

Microbial infections are a major cause of morbidity and mortality among people living with HIV (PLWH). Respiratory tract infections (RTIs) are responsible for approximately 70% of illnesses among PLWH. Drug resistant bacteria are highly prevalent among PLWH and this is a public health concern.

METHODS

This is a retrospective analysis of data collected during the COSTOP trial between 2011 and 2013. Sputum collected on spot from participants presenting with a productive cough was examined using Gram, Ziehl-Neelsen stains and cultured on suitable bacteriological media. Antimicrobial sensitivity testing was done on isolated pathogens, by disc diffusion technique.

RESULTS

We included 687 participants with mean age 41.3 (SD 8.2) years of whom 76.4% were female. Two hundred one sputum samples grew bacteria; Moraxella species (27.4%), Streptococcus pneumoniae(25.4%), Haemophilus influenza(22.4%), Mycobacterium species(4.5%), Pseudomonas species(4.0%), Staphylococcus aureus(4.0%), Escherichia coli (1.0%), Klebsiella species (1.0%), other bacteria (10.4%). A higher monthly income greater than or equal to 30$ (aOR = 0.63, 95%CI: 0.40-0.99) and longer duration since HIV diagnosis (aOR = 1.06, 95%CI: 1.0-1.11) were found to be independently associated with a positive bacterial culture. Moraxella sp, H. influenza and Pseudomonas had zero sensitivity towards cotrimoxazole. Sensitivity to erythromycin was low among Moraxella sp (28.6%), H. influenza (31.6%) and S. aureus(42.9%) and other bacteria (42.9%). Most isolates were sensitive to Amoxicillin + Clavulanic acid and ceftriaxone.

CONCLUSION

There is a very low sensitivity of isolated bacteria to commonly prescribed antibiotics that are more available through the national supply chain, which is of public health concern. Urgent steps to tackle the high antimicrobial resistance among PLWH is required.

Extensive screening reveals previously undiscovered aminoglycoside resistance genes in human pathogens

Antibiotic resistance is a growing threat to human health, caused in part by pathogens accumulating antibiotic resistance genes (ARGs) through horizontal gene transfer. New ARGs are typically not recognized until they have become widely disseminated, which limits our ability to reduce their spread. In this study, we use large-scale computational screening of bacterial genomes to identify previously undiscovered mobile ARGs in pathogens. From ~1 million genomes, we predict 1,071,815 genes encoding 34,053 unique aminoglycoside-modifying enzymes (AMEs). These cluster into 7,612 families (<70% amino acid identity) of which 88 are previously described. Fifty new AME families are associated with mobile genetic elements and pathogenic hosts. From these, 24 of 28 experimentally tested AMEs confer resistance to aminoglycoside(s) in Escherichia coli, with 17 providing resistance above clinical breakpoints. This study greatly expands the range of clinically relevant aminoglycoside resistance determinants and demonstrates that computational methods enable early discovery of potentially emerging ARGs.

Synergistic Antibacterial Effects of Amoxicillin and Gold Nanoparticles: A Therapeutic Option to Combat Antibiotic Resistance

Compacted Au@16-mph-16/DNA-AMOX (NSi) nanosystems were prepared from amoxicillin (AMOX) and precursor Au@16-mph-16 gold nanoparticles (Ni) using a Deoxyribonucleic acid (DNA) biopolymer as a glue. The synthesized nanocarrier was tested on different bacterial strains of Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae to evaluate its effectiveness as an antibiotic as well as its internalization. Synthesis of the nanosystems required previous structural and thermodynamic studies using circular dichroism (CD) and UV-visible techniques to guarantee optimal complex formation and maximal DNA compaction, characteristics which facilitate the correct uptake of the nanocarrier. Two nanocomplexes with different compositions and structures, denoted NS1 and NS2, were prepared, the first involving external Au@16-mph-16 binding and the second partial intercalation. The Ni and NSi nanosystems obtained were characterized via transmission electron microscopy (TEM), zeta potential, and dynamic light scattering (DLS) techniques to measure their charge, aggregation state and hydrodynamic size, and to verify their presence inside the bacteria. From these studies, it was concluded that the zeta potential values for gold nanoparticles, NS1, and NS2 nanosystems were 67.8, -36.7, and -45.1 mV. Moreover, the particle size distribution of the Au@16-mph-16 gold nanoparticles and NS2 nanoformulation was found to be 2.6 nm and 69.0 nm, respectively. However, for NS1 nanoformulation, a bimodal size distribution of 44 nm (95.5%) and 205 nm (4.5%) was found. Minimal inhibitory concentration (MIC) values were determined for the bacteria studied using a microdilution plates assay. The effect on Escherichia coli bacteria was notable, with MIC values of 17 µM for both the NS1 and NS2 nanosystems. The Staphylococcus aureus chart shows a greater inhibition effect of NS2 and NP2 in non-diluted wells, and clearly reveals a great effect on Streptococcus pneumoniae, reaching MIC values of 0.53 µM in more diluted wells. These results are in good agreement with TEM internalization studies of bacteria that reveal significant internalization and damage in Streptococcus pneumoniae. In all the treatments carried out, the antibiotic capacity of gold nanosystems as enhancers of amoxicillin was demonstrated, causing both the precursors and the nanosystems to act very quickly, and thus favoring microbial death with a small amount of antibiotic. Therefore, these gold nanosystems may constitute an effective therapy to combat resistance to antibiotics, in addition to avoiding the secondary effects derived from the administration of high doses of antibiotics.

What's the Matter with MICs: Bacterial Nutrition, Limiting Resources, and Antibiotic Pharmacodynamics

The MIC of an antibiotic required to prevent replication is used both as a measure of the susceptibility/resistance of bacteria to that drug and as the single pharmacodynamic parameter for the rational design of antibiotic treatment regimes. MICs are experimentally estimated in vitro under conditions optimal for the action of the antibiotic. However, bacteria rarely grow in these optimal conditions. Using a mathematical model of the pharmacodynamics of antibiotics, we make predictions about the nutrient dependency of bacterial growth in the presence of antibiotics. We test these predictions with experiments in broth and a glucose-limited minimal media with Escherichia coli and eight different antibiotics. Our experiments question the sufficiency of using MICs and simple pharmacodynamic functions as measures of the pharmacodynamics of antibiotics under the nutritional conditions of infected tissues. To an extent that varies among drugs: (i) the estimated MICs obtained in rich media are greater than those estimated in minimal media; (ii) exposure to these drugs increases the time before logarithmic growth starts, their lag; and (iii) the stationary-phase density of E. coli populations declines with greater sub-MIC antibiotic concentrations. We postulate a mechanism to account for the relationship between sub-MICs of antibiotics and these growth parameters. This study is limited to a single bacterial strain and two types of culture media with different nutritive content. These limitations aside, the results of our study clearly question the use of MIC as the unique pharmacodynamic parameter to develop therapeutically oriented protocols. IMPORTANCE For studies of antibiotics and how they work, the most-often used measurement of drug efficacy is the MIC. The MIC is the concentration of an antibiotic needed to inhibit bacterial growth. This parameter is critical to the design and implementation of antibiotic therapy. We provide evidence that the use of MIC as the sole measurement for antibiotic efficacy ignores important aspects of bacterial growth dynamics. Before now, there has not been a nexus between bacteria, the conditions in which they grow, and the MIC. Most importantly, few studies have considered sub-MICs of antibiotics, despite their clinical importance. Here, we explore these concentrations in-depth, and we demonstrate MIC to be an incomplete measure of how an infection will interact with a specific antibiotic. Understanding the critiques of MIC is the first of many steps needed to improve infectious disease treatment.

Glabridin inhibited the spread of polymyxin-resistant Enterobacterium carrying ICEMmoMP63

Introduction

The role of integrative and conjugative elements (ICEs) in antibiotic resistance in Morganella morganii is unknown. This study aimed to determine whether an ICE identified in the M. morganii genome contributed to the polymyxin resistance.

Methods

Whole-genome sequencing was performed followed by bioinformatics analyses to identify ICEs and antibiotic resistance genes. Conjugation assays were performed to analyze the transferability of a discovered ICE. A drug transporter encoded on the ICE was heterogeneously expressed in Escherichia coli, minimum inhibitory concentrations of antibiotics were determined, and a traditional Chinese medicine library was screened for potential efflux pump inhibitors.

Results

An antibiotic resistance-conferring ICE, named ICEMmoMP63, was identified. ICEMmoMP63 was verified to be horizontally transferred among Enterobacteriaceae bacteria. G3577_03020 in ICEMmoMP63 was found to mediate multiple antibiotic resistances, especially polymyxin resistance. However, natural compound glabridin was demonstrated to inhibit polymyxin resistance.

Discussion

Our findings support the need for monitoring dissemination of ICEMmoMP63 in Enterobacteriaceae bacteria. Combined glabridin and polymyxin may have therapeutic potential for treating infections from multi-drug resistant bacteria carrying ICEMmoMP63.

Alterations in Antibiotic Susceptibility of Staphylococcus aureus and Klebsiella pneumoniae in Dual Species Biofilms

In the last decades, it has been shown that biofilm-associated infections in most cases are caused by rather two or even more pathogens than by single microorganisms. Due to intermicrobial interactions in mixed communities, bacteria change their gene expression profile, in turn leading to alterations in the biofilm structure and properties, as well as susceptibility to antimicrobials. Here, we report the alterations of antimicrobials efficiency in mixed biofilms of Staphylococcus aureus-Klebsiella pneumoniae in comparison with mono-species biofilms of each counterpart and discuss possible mechanisms of these alterations. In cell clumps detached from dual-species biofilms, S. aureus became insensitive to vancomycin, ampicillin, and ceftazidime compared to solely S. aureus cell clumps. In turn, the increased efficiency of amikacin and ciprofloxacin against both bacteria could be observed, compared to mono-species biofilms of each counterpart. Scanning electron microscopy and confocal microscopy indicate the porous structure of the dual-species biofilm, and differential fluorescent staining revealed an increased number of polysaccharides in the matrix, in turn leading to more loose structure and thus apparently providing increased permeability of the dual-species biofilm to antimicrobials. The qRT-PCR showed that ica operon in S. aureus became repressed in mixed communities, and polysaccharides are produced mainly by K. pneumoniae. While the molecular trigger of these changes remains undiscovered, detailed knowledge of the alterations in antibiotic susceptibility to given drugs opens doors for treatment correction options for S. aureus-K. pneumoniae biofilm-associated infections.

Antimicrobial Susceptibility of Bacteria Isolated from Freshwater Mussels in the Wildcat Creek Watershed, Indiana, United States

Antimicrobial resistance (AMR) is a global health crisis that threatens the health of humans and animals. The spread of resistance among species may occur through our shared environment. Prevention of AMR requires integrated monitoring systems, and these systems must account for the presence of AMR in the environment in order to be effective. The purpose of this study was to establish and pilot a set of procedures for utilizing freshwater mussels as a means of surveillance for microbes with AMR in Indiana waterways. One hundred and eighty freshwater mussels were sampled from three sites along the Wildcat Creek watershed in north-central Indiana. Specimens were evaluated for the presence of ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species), Escherichia coli, Campylobacter, and Salmonella species, and the isolates were tested for antimicrobial resistance. A total of 24 bacterial isolates were obtained from tissue homogenates of freshwater mussels collected at a site directly downstream from Kokomo, Indiana. Of these, 17 were Enterobacter spp., five were Escherichia coli, one was Pseudomonas aeruginosa, and one was Klebsiella pneumoniae. All isolates were resistant to three or more antimicrobial drug classes. Further work is necessary to determine the source of the bacterial species found in the mussels.

Population pharmacokinetics and pharmacokinetic/pharmacodynamic evaluation of marbofloxacin against Coagulase-negative staphylococci, Staphylococcus aureus and Mycoplasma agalactiae pathogens in goats

Marbofloxacin is a broad-spectrum fluoroquinolone, and an extra-label use has been reported in horse, sheep and goat. However, extrapolation of dosage regimens from cattle to horse and small ruminants could lead to incorrect dosing due to pharmacokinetic differences among species, increasing the risk of antimicrobial resistance or toxicity. Pharmacokinetic properties of marbofloxacin, including PK/PD analysis, have been studied by intravenous, intramuscular and subcutaneous administration in lactating and non-lactating goats. A population pharmacokinetic model of marbofloxacin in goats was built using 10 pharmacokinetic studies after intravenous, intramuscular, and subcutaneous administration at a dose of 2, 5 and 10 mg/kg. Serum or plasma and milk concentration-time profiles were simultaneously fitted with a non-linear mixed effect model with Monolix software. Level of milk production (lactating and non-lactating) and health status (healthy and un-healthy) were retained as covariates on volume of distribution and clearance. Marbofloxacin concentrations were well described in plasma/serum and milk by the population model. Simulated dose regimens of marbofloxacin administered at 2, 5 and 10 mg/kg by intramuscular route for five days were evaluated (n = 5000 per group). Steady-state fAUCs for each dose regimen were obtained. Probability of target attainment of fAUC/MIC ratios were determined and PK/PDco values (highest MIC for which 90% of individuals can achieve a prior numerical value of the fAUC/MIC index) were established using Monte Carlo simulations (n = 50,000). MIC values for wild type isolates of Staphylococcus aureus, coagulase negative staphylococci, and Mycoplasma agalactiae were determined and tentative epidemiological cutoff (TECOFF) were obtained at 1.0, 0.5 and 0.5 mg/L, respectively. The PK/PDco for the dose regimen of 2 mg/kg/24 h and 5 mg/kg/24 h (0.125 and 0.25 mg/L) were lower than TECOFF (0.5 and 1 mg/L). The dosage regimen of 10 mg/kg/24 h was adequate for intermediate MIC values of 0.125-0.50 mg/L and could be effective for a population with a target fAUC/MIC ratio ˂ 48 for Coagulase negative staphylococci and Mycoplasma agalactiae, but not for Staphylococcus aureus. Results obtained in this study could be taken as a starting point by committees that set the clinical breakpoints and justifies expert rules to optimize marbofloxacin dose regimens.

Genomic Characterization of Staphylococcus aureus in Wildlife

Staphylococcus aureus is an opportunistic multi-host pathogen that threatens both human and animal health. Animals can act as a reservoir of S. aureus for humans, but very little is known about wild animals’ epidemiological role. Therefore, in this study, we performed a genomic characterization of S. aureus isolates from wildlife, hunters, and their auxiliary hunting animals of Eastern Spain. Of 20 different species, 242 wild animals were examined, of which 28.1% were S. aureus carriers. The common genet, the Iberian ibex, and the European hedgehog were the species with the highest S. aureus carriage. We identified 30 different sequence types (STs), including lineages associated with wild animals such as ST49 and ST581, multispecies lineages such as ST130, ST398, and ST425, and lineages commonly isolated from humans, including ST1 and ST5. The hunters and the single positive ferret shared ST5, ST398, or ST425 with wild animals. In wildlife isolates, the highest resistance levels were found for penicillin (32.8%). For virulence factors, 26.2% of them carried superantigens, while 14.8% harbored the immune evasion cluster (IEC), which indicates probable human origin. Our findings suggest that wild animals are a reservoir of clinically relevant genes and lineages that could have the potential to be transmitted to humans. These data support the notion that wildlife surveillance is necessary to better understand the epidemiology of S. aureus as a pathogen that circulates among humans, animals, and the environment.

Antibacterial Enhancement of High-Efficiency Particulate Air Filters Modified with Graphene-Silver Hybrid Material

Bacterial infections are a major concern as antibiotic resistance poses a great threat, therefore leading to a race against time into finding new drugs or improving the existing resources. Nanomaterials with high surface area and bactericidal properties are the most promising ones that help combating microbial infections. In our case, graphene decorated with silver nanoparticles Gr-Ag (5 wt% Ag) exhibited inhibitory capacity against S. aureus and E. coli. The newly formed hybrid material was next incubated with high-efficiency particulate air (HEPA) filter, to obtain one with bactericidal properties. The modified filter had greater inhibitory action against the tested strains, compared to the control, and the effect was better against the Gram-negative model. Even if the bacteria remained attached to the filters, their colony forming unit capacity was affected by the Gr-Ag (5 wt% Ag) hybrid material, when they were subsequently re-cultured on fresh agar media. Therefore, the HEPA filter modified with Gr-Ag (5 wt% Ag) has high antibacterial properties that may substantially improve the existing technology.

Update on Therapeutic Drug Monitoring of Beta-Lactam Antibiotics in Critically Ill Patients—A Narrative Review

Beta-lactam antibiotics remain one of the most preferred groups of antibiotics in critical care due to their excellent safety profiles and their activity against a wide spectrum of pathogens. The cornerstone of appropriate therapy with beta-lactams is to achieve an adequate plasmatic concentration of a given antibiotic, which is derived primarily from the minimum inhibitory concentration (MIC) of the specific pathogen. In a critically ill patient, the plasmatic levels of drugs could be affected by many significant changes in the patient’s physiology, such as hypoalbuminemia, endothelial dysfunction with the leakage of intravascular fluid into interstitial space and acute kidney injury. Predicting antibiotic concentration from models based on non-critically ill populations may be misleading. Therapeutic drug monitoring (TDM) has been shown to be effective in achieving adequate concentrations of many drugs, including beta-lactam antibiotics. Reliable methods, such as high-performance liquid chromatography, provide the accurate testing of a wide range of beta-lactam antibiotics. Long turnaround times remain the main drawback limiting their widespread use, although progress has been made recently in the implementation of different novel methods of antibiotic testing. However, whether the TDM approach can effectively improve clinically relevant patient outcomes must be proved in future clinical trials.

Susceptibility pattern of bacterial isolates in equine ulcerative keratitis: Implications for empirical treatment at a university teaching hospital in Sydney

Corneal ulceration is a common ophthalmic condition in horses. It is frequently caused by trauma to the corneal surface, followed by secondary infection by commensal or pathogenic organisms including Streptococcus equi subspecies zooepidemicus, Pseudomonas aeruginosa and Staphylococcus spp. Emerging antimicrobial resistance amongst these organisms has raised the need for appropriate antimicrobial therapy selection, to optimise treatment efficacy while minimising further antimicrobial resistance. Medical records of 38 horses presented at the University Veterinary Teaching Hospital Camden for ulcerative keratitis between 2010 and 2020 were reviewed to identify those with positive bacterial cultures and antimicrobial susceptibility profiles (13/38). Common susceptibility patterns were identified and used to guide the empirical treatment of equine bacterial corneal ulcers. Pseudomonas spp. (64.3%), Streptococcus equi subspecies zooepidemicus (14.3%) and Actinobacillus spp. (14.3%) were most commonly identified. Susceptibility to amikacin, gentamicin and ciprofloxacin was observed in 100%, 66.7% and 85.7% Pseudomonas spp. isolates respectively. Resistance to polymyxin B and neomycin occurred in 85.7% and 71.4% of Pseudomonas spp., respectively. All Streptococcus equi subspecies zooepidemicus organisms in this study were susceptible to ceftiofur, cephalexin, penicillin and ampicillin, while they were all resistant to gentamicin, neomycin, enrofloxacin and marbofloxacin. Predominating in this study, Pseudomonas spp. maintained overall aminoglycoside susceptibility despite some emerging resistance, and good fluoroquinolone susceptibility. High resistance to Polymyxin B could have arisen from its common use as first-line therapy for bacterial corneal ulcers. Although further research is required, these new findings about predominant bacteria in equine corneal ulceration in the Camden region and their antimicrobial susceptibility patterns can be used to guide the empirical treatment of bacterial corneal ulcers in horses.

Severe community-acquired Streptococcus pneumoniae bacterial meningitis: clinical and prognostic picture from the intensive care unit

BACKGROUND

Severe community-acquired pneumococcal meningitis is a medical emergency. The aim of the present investigation was to evaluate the epidemiology, management and outcomes of this condition.

METHODS

This was a retrospective, observational and multicenter cohort study. Sixteen Spanish intensive care units (ICUs) were included. Demographic, clinical and microbiological variables from patients with Streptococcus pneumoniae meningitis admitted to ICU were evaluated. Clinical response was evaluated at 72 h after antibiotic treatment initiation, and meningitis complications, length of stay and 30-day mortality were also recorded.

RESULTS

In total, 255 patients were included. Cerebrospinal fluid (CSF) culture was positive in 89.7%; 25.7% were non-susceptible to penicillin, and 5.2% were non-susceptible to ceftriaxone or cefotaxime. The most frequent empiric antibiotic regimen was third-generation cephalosporin (47.5%) plus vancomycin (27.8%) or linezolid (12.9%). A steroid treatment regimen was administered to 88.6% of the patients. Clinical response was achieved in 65.8% of patients after 72 h of antibiotic treatment. Multivariate analysis identified two factors associated with early treatment failure: invasive mechanical ventilation (OR 10.74; 95% CI 3.04-37.95, p < 0.001) and septic shock (OR 1.18; 95% CI 1.03-1.36, p = 0.017). The 30-day mortality rate was 13.7%. Only three factors were independently associated with 30-day mortality: delay in start of antibiotic treatment (OR 18.69; 95% CI 2.13-163.97, p = 0.008), Sepsis-related Organ Failure Assessment (SOFA) score (OR 1.36; 95% CI 1.12-1.66, p = 0.002) and early treatment failure (OR 21.75 (3.40-139.18), p = 0.001). Neurological complications appeared in 124 patients (48.63%).

CONCLUSIONS

Mortality rate in critically ill patients with pneumococcal meningitis is lower than previously reported. Delay in antibiotic treatment following admission is the only amendable factor associated with mortality.

Chemical Composition and Antimicrobial Potential of a Plant-Based Substance for the Treatment of Seborrheic Dermatitis

Seborrheic dermatitis (SD) is the most prevalent dermatological disease, occurring in up to 50% of newborns, children, and adults around the world. The antibacterial and antifungal resistance contributed to the search for new natural substances and the development of a novel substance based on Melaleuca alternifolia (M. alternifolia) leaf oil (TTO), 1,8-cineole (eucalyptol), and α-(-)-bisabolol. Thus, this work aimed to determine the chemical composition of the novel plant-based substance and to evaluate its antimicrobial activity against standard microorganisms involved in the pathogenesis of SD. Moreover, the chemical composition of the substance was analyzed by gas chromatography coupled with mass spectrometry (GC/MS). Staphylococcus epidermidis (S. epidermidis), Staphylococcus aureus (S. aureus), Micrococcus luteus (M. luteus), and Candida albicans (C. albicans) were used for antimicrobial and antifungal assays by means of the broth microdilution method to determine the minimal inhibitory concentration (MIC). Finally, the substance’s ability to inhibit Malassezia furfur (M. furfur) was evaluated. Eighteen compounds from different chemical groups were identified by GC/MS. The major biologically active compounds of the substance were terpinen-4-ol (20.88%), 1,8-cineole (22.28%), (-)-α-bisabolol (25.73%), and o-cymene (8.16%). The results showed that the substance has a synergistic antimicrobial and antifungal activity, while S. epidermidis and C. albicans strains were the most susceptible. Furthermore, the substance inhibited M. furfur, which is a main pathogen involved in the pathogenesis of SD and clinical manifestations. It can be concluded that the novel plant-based substance has a promising potential against M. furfur and scalp commensal bacteria and may be helpful for the development of new drugs for treatment of dandruff and SD.

N-(((1S,5R)-6,6-Dimethylbicyclo[3.1.1]hept-2-en-2-yl)methyl)-3-((1R,5S)-6,6-dimethylbicyclo[3.1.1]hept-2-ene/ane-2-carboxamido)-N,N-dimethylpropan-1-aminium Bromide

The synthesis of the title compounds was performed from (-)-cis-myrtanic and (-)-myrtenic acids. The compounds obtained were characterized using 1H- and 13C-NMR, IR, and high-resolution mass spectrometry. Despite the presence of quaternary ammonium moiety, both compounds had moderate antimicrobial activity with a MIC of 128 µg/mL on S. aureus and 512 µg/mL on E. coli. The antifungal activity was low on Candida isolates, while also comparable with conventional antimycotic (Fluconazole) on filamentous fungi. These data suggest that two bulky bicyclic terpene fragments apparently both increase lipophilicity and close the quaternary ammonium moiety located in the center of molecules and thus drastically decrease the antimicrobial potential of bipharmacophore.

Safety Evaluation and Probiotic Potency Screening of Akkermansia muciniphila Strains Isolated from Human Feces and Breast Milk

Akkermansia muciniphila is considered a next-generation probiotic because of its immense potential to regulate disorders. We isolated 31 strains of A. muciniphila from feces or breast milk of healthy people. After genome sequencing, assembly, and analysis, we selected six strains (AM01 to AM06) for further exploration. We first analyzed their general characteristics, including morphological description, growth characteristics, and physiological and biochemical characteristics, and then confirmed their genetic characteristics, including GC content, putative virulence factors, and antibiotic resistance genes. We next investigated the tolerance of these strains to artificial gastric and intestinal fluids and bile salts to evaluate their survival potential in the digestive tract. Drug sensitivity tests were also conducted based on the analysis of the antibiotic resistance genes of these strains. Furthermore, we examined the genetic stability and acute toxicity of two strains (AM02 and AM06) in mice. Finally, the safety of AM06 was evaluated in normal mice and nude mice. AM06 exhibited adaptability to pH changes. Since AM02 and AM03 showed more resistance to antibiotics than AM01 and AM04 to AM06, their potential clinical application may be limited. Both AM02 and AM06 were genetically and phenotypically stable and safe in normal mice, and AM06 was safe in nude mice. Considering all this together, AM06 is a safe A. muciniphila strain and exhibits a great potential for use as a probiotic strain among the isolated strains. IMPORTANCE In this study, we isolated 30 strains of Akkermansia muciniphila from different samples of human feces, and for the first time we isolated an A. muciniphila strain from human breast milk. This isolation verified the existence of microbes in human breast milk, which suggests that A. muciniphila can be vertically propagated from mother to infant and participates in the formation of the early gut microbiome. We then systematically evaluated the potential for use as a probiotic of this A. muciniphila strains according to the FAO/WHO recommendation. We confirmed that the AM06 strain isolated from breast milk has no virulence factors and is genetically stable and nonpathogenic for both normal mice and nude mice. Moreover, its tolerance to pH changes and bile salts indicates its desirable probiotic properties. Thus, we propose that the AM06 strain of A. muciniphila is safe for use as a probiotic candidate.

Microbiology of Facial Skin Infections-Strains, Susceptibility, and Therapeutic Consequences

BACKGROUND

Skin and soft tissue infections (SSTIs) are common conditions with severe and potentially life-threatening outcomes. However, the use of antibiotics to treat these infections is controversial.

PURPOSE

This study was to identify the microorganisms responsible for facial SSTIs, their antibiotic sensitivities, and the therapeutic outcomes of treatment.

STUDY DESIGN, SETTING, AND SAMPLE

This was a retrospective, observational cohort study conducted at a single oral and maxillofacial plastic surgery department. The study sample included 103 patients with facial SSTIs (61 men, 42 women) with a mean age of 41.8 years (standard deviation ± 20.4).

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLES

The predictor variables included patient characteristics, antibiotic use before the clinic visit, and the infection's site and origin.

MAIN OUTCOME VARIABLE(S)

The primary outcome variable was the presence of antibiotic resistance in the bacterial strains isolated from the infections.

METHODS

The data were collected by reviewing the results of microbiological swabs and patient records obtained from patients with facial SSTIs. Categorical variables were described using absolute and relative frequencies, and continuous variables were described using mean and standard deviation. The association between antibiotic resistance and the predictor variables was analyzed using Pearson's χ² test and student's t test.

RESULTS

The most common cause of SSTI was an infected epidermal cyst (60.1%). Of all the microorganisms identified, 80.6% were Gram-positive, and 55.8% showed antibiotic resistance against one or more of the evaluated antibiotics, including several backup antibiotics. There were no identified risk factors that significantly influenced the probability of resistance, and there were no adverse events observed.

CONCLUSION

The results of this study suggest that surgery should be the primary approach for treating SSTIs, as antibiotic administration may not be effective due to the unknown susceptibility of the causative strains. Antibiotics should be reserved for severe cases and high-risk patients, and if deemed necessary for SSTI management, a broad-spectrum antibiotic should be administered to cover resistant organisms.

A Synthetic Polymicrobial Community Biofilm Model Demonstrates Spatial Partitioning, Tolerance to Antimicrobial Treatment, Reduced Metabolism, and Small Colony Variants Typical of Chronic Wound Biofilms

Understanding chronic wound infection is key for successful treatment and requires accurate laboratory models. We describe a modified biofilm flow device that effectively mimics the chronic wound environment, including simulated wound fluid, a collagen-based 3D biofilm matrix, and a five-species mixture of clinically relevant bacteria (Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Citrobacter freundii). Mixed biofilms were cultured for between 3 and 14 days with consistent numbers of bacteria that exhibited reduced metabolic activity, which increased with a high dose of glucose. S. aureus was recovered from biofilms as a small colony variant, but as a normal colony variant if P. aeruginosa was excluded from the system. Bacteria within the biofilm did not co-aggregate but formed discrete, species-specific clusters. Biofilms demonstrated differential tolerance to the topical antimicrobials Neosporin and HOCl, consistent with protection due to the biofilm lifestyle. The characteristics exhibited within this model match those of real-world wound biofilms, reflecting the clinical scenario and yielding a powerful in vitro tool that is versatile, inexpensive, and pivotal for understanding chronic wound infection.

Invited review: Antimicrobial resistance in bovine mastitis pathogens: A review of genetic determinants and prevalence of resistance in European countries

Antimicrobial resistance is an urgent and growing problem worldwide, both for human and animal health. In the animal health sector actions have been taken as concerns grow regarding the development and spread of antimicrobial resistance. Mastitis is the most common infection in dairy cattle. We aimed to summarize the genetic determinants found in staphylococci, streptococci, and Enterobacteriaceae isolated from mastitic milk samples and provide a comparison of percentage resistance to a variety of antimicrobials in European countries.

Genomic analysis of Chryseobacterium indologenes and conformational dynamics of the selected DD-peptidase

Chrysobacterium indologenes is an emerging MDR pathogen that belongs to the family Flavobacteriaceae. The genome of the C. indologenes, isolated from the nephrotic patient, was sequenced through Illumina MiSeq. The pangenomics of available 56 C. indologenes strains using BPGA revealed an open pangenome (n=5553 CDS), core genome (2141), and accessory genome (2013). The CEG/DEG database identified 662 essential genes that drastically reduced to 68 genes after non-homology analyses towards human and gut microbiome. Further filtering the data for other drug target prioritizing parameters resulted in 32 putative targets. Keeping in view the crucial role played in cell wall biosynthesis, dacB was selected as the final target that encodes D-alanyl-d-alanine carboxypeptidase/endopeptidase (DD-peptidase). The 3D structure of dacB was modelled and rendered to docking analyses against two compound libraries of African plants (n=6842) and Tibetan medicines (n=52). The ADMET profiling exhibited the physicochemical properties of final compounds. The MD simulations showed the stability of inhibitor-DD-peptidase complex and interactions in terms of RMSD, RMSF, binding free energy calculation and H-bonding. We propose that the novel compounds Leptopene and ZINC95486338 from our findings might be potent DD-peptidase inhibitors that could aid in the development of new antibiotic-resistant therapy for the emerging MDR C. indologenes.

Antimicrobial and Biofilm-Preventing Activity of l-Borneol Possessing 2(5H)-Furanone Derivative F131 against S. aureus—C. albicans Mixed Cultures

Candida albicans and Staphylococcus aureus are human pathogens that are able to form mixed biofilms on the surface of mucous membranes, implants and catheters. In biofilms, these pathogens have increased resistance to antimicrobials, leading to extreme difficulties in the treatment of mixed infections. The growing frequency of mixed infections caused by S. aureus and C. albicans requires either the development of new antimicrobials or the proposal of alternative approaches to increase the efficiency of conventional ones. Here, we show the antimicrobial, biofilm-preventing and biofilm-eradicating activity of 2(5H)-furanone derivative F131, containing an l-borneol fragment against S. aureus-C. albicans mixed biofilms. Furanone F131 is also capable of inhibiting the formation of monospecies and mixed biofilms by S. aureus and C. albicans. The minimal biofilm-prevention concentration (MBPC) of this compound was 8-16 μg/mL for S. aureus and C. albicans mono- and two-species biofilms. While the compound demonstrates slightly lower activity compared to conventional antimicrobials (gentamicin, amikacin, fluconazole, terbinafine and benzalkonium chloride), F131 also increases the antimicrobial activity of fluconazole-gentamicin and benzalkonium chloride against mixed biofilms of S. aureus-C. albicans, thus reducing MBPC of fluconazole-gentamicin by 4-16 times and benzalkonium chloride twofold. F131 does not affect the transcription of the MDR1, CDR1 and CDR2 genes, thus suggesting a low risk of micromycete resistance to this compound. Altogether, combined use of antibiotics with a F131 could be a promising option to reduce the concentration of fluconazole used in antiseptic compositions and reduce the toxic effect of benzalkonium chloride and gentamicin. This makes them an attractive starting point for the development of alternative antimicrobials for the treatment of skin infections caused by S. aureus-C. albicans mixed biofilms.

New putative therapeutic targets against Serratia marcescens using reverse vaccinology and subtractive genomics

The Gram-negative bacillus Serratia marcescens, a member of Enterobacteriaceae family, is an opportunistic nosocomial pathogen commonly found in hospital outbreaks that can cause infections in the urinary tract, bloodstream, central nervous system and pneumonia. Because S. marcescens strains are resistant to several antibiotics, it is critical the need for effective treatments, including new drugs and vaccines. Here, we applied reverse vaccinology and subtractive genomic approaches for the in silico prediction of potential vaccine and drug targets against 59 strains of S. marcescens. We found 759 core non-host homologous proteins, of which 87 are putative surface-exposed proteins, 183 secreted proteins, and 80 membrane proteins. From these proteins, we predicted seven candidates vaccine targets: a sn-glycerol-3-phosphate-binding periplasmic protein UgpB, a vitamin B12 TonB-dependent receptor, a ferrichrome porin FhuA, a divisome-associated lipoprotein YraP, a membrane-bound lytic murein transglycosylase A, a peptidoglycan lytic exotransglycosylase, and a DUF481 domain-containing protein. We also predicted two drug targets: a N(4)-acetylcytidine amidohydrolase, and a DUF1428 family protein. Using the molecular docking approach for each drug target, we identified and selected ZINC04259491 and ZINC04235390 molecules as the most favorable interactions with the target active site residues. Our findings may contribute to the development of vaccines and new drug targets against S. marcescens. Communicated by Ramaswamy H. Sarma.