Crotamine derived from Crotalus durissus terrificus venom combined with drugs increases in vitro antibacterial and antifungal activities.

This study investigated crotamine (CTA), a peptide derived from the venom of the South American rattlesnake Crotalus durissus terrificus, known for its exceptional cell penetration potential. The objective was to explore the antibacterial and antifungal activity of CTA, its ability to inhibit efflux pumps and evaluate the effectiveness of its pharmacological combination with antibiotics and antifungals. In microbiological assays, CTA in combination with antibiotics was tested against strains of S. aureus and the inhibition of NorA, Tet(K) and MepA efflux pumps was also evaluated. CTA alone did not present clinically relevant direct antibacterial action, presenting MIC > 209.7 µM against strains S. aureus 1199B, IS-58, K2068. The standard efflux pump inhibitor CCCP showed significant effects in all negative relationships to assay reproducibility. Against the S. aureus 1199B strain, CTA (20.5 µM) associated with norfloxacin diluted 10 × (320.67 µM) showed a potentiating effect, in relation to the control. Against the S. aureus IS-58 strain, the CTA associated with tetracycline did not show a significant combinatorial effect, either with 2304 or 230.4 µM tetracycline. CTA at a concentration of 2.05 µM associated with ciprofloxacin at a concentration of 309.4 µM showed a significant potentiating effect. In association with EtBr, CTA at concentrations of 2.05 and 20.5 µM potentiated the effect in all strains tested, reducing the prevention of NorA, Tet(K) and MepA efflux pumps. In the C. albicans strain, a potentiating effect of fluconazole (334.3 µM) was observed when combined with CTA (2.05 µM). Against the C. tropicalis strain, a significant effect was also observed in the association of fluconazole 334.3 µM, where CTA 2.05 µM considerably reduced fungal growth and decreased the potentiation of fluconazole. Against the C. krusei strain, no significant potentiating effect of fluconazole was obtained by CTA. Our results indicate that CTA in pharmacological combination potentiates the effects of antibiotics and antifungal. This represents a new and promising antimicrobial strategy for treating a wide variety of infections.

Genomic analysis of Oceanotoga teriensis strain UFV_LIMV02, a multidrug-resistant thermophilic bacterium isolated from an offshore oil reservoir.

Bacteria of the species Oceanotoga teriensis belong to the family Petrotogaceae, are Gram-negative bacilli, are moderately thermophilic and are included in the group of thiosulfate-reducing bacteria, being capable of significantly accelerating corrosion in metallic structures. However, no in-depth study on the genome, antibiotic resistance and mobile elements has been carried out so far. In this work, the isolation, phenotypic and genotypic characterization of the multi-resistant O. teriensis UFV_LIMV02 strain was carried out, from water samples from an offshore oil extraction platform in Rio de Janeiro (Brazil). We determined that the isolate has a genome of 2 812 778 bp in size, with 26 % GC content, organized into 34 contigs. Genomic annotation using Rapid Annotation using Subsystem Technology revealed the presence of genes related to resistance to antibiotics and heavy metals. By evaluating the antimicrobial resistance of the isolate using the disc diffusion technique, resistance was verified for the classes of antibiotics, beta-lactams, fluoroquinolones, aminoglycosides, sulfonamides, lincosamides and rifamycins, a total of 14 antibiotics. The search for genomic islands, prophages and defence systems against phage infection revealed the presence of five genomic islands in its genome, containing genes related to resistance to heavy metals and antibiotics, most of which are efflux pumps and several transposases. No prophage was found in its genome; however, nine different defence systems against phage infection were detected. When analysing the clustered regularly interspaced short palindromic repeat (CRISPR) systems, four CRISPR arrays, classified as types I-B and III-B, with 272 spacers, can provide the strain with immunity to different mobile genetic elements and bacteriophage infection. The results found in this study show that the isolate UFV_LIVM02 is an environmental bacterium, resistant to different classes of antibiotics, and that the proteins encoded by the predicted genomic islands may be associated with the development of greater resistance to antibiotics and heavy metals. They provide evidence that environmental bacteria found in offshore oil exploration residues may pose a risk for the spread of antibiotic resistance genes. More comprehensive studies on the microbial community present in oil waste are needed to assess the risks of horizontal gene transfer.

Development and external validation of a model to predict multidrug-resistant bacterial infections in patients with cirrhosis.

With the increasing rate of infections caused by multidrug-resistant organisms (MDRO), selecting appropriate empiric antibiotics has become challenging. We aimed to develop and externally validate a model for predicting the risk of MDRO infections in patients with cirrhosis. METHODS: We included patients with cirrhosis and bacterial infections from two prospective studies: a transcontinental study was used for model development and internal validation (n = 1302), and a study from Argentina and Uruguay was used for external validation (n = 472). All predictors were measured at the time of infection. Both culture-positive and culture-negative infections were included. The model was developed using logistic regression with backward stepwise predictor selection. We externally validated the optimism-adjusted model using calibration and discrimination statistics and evaluated its clinical utility. RESULTS: The prevalence of MDRO infections was 19% and 22% in the development and external validation datasets, respectively. The model's predictors were sex, prior antibiotic use, type and site of infection, MELD-Na, use of vasopressors, acute-on-chronic liver failure, and interaction terms. Upon external validation, the calibration slope was 77 (95% CI .48-1.05), and the area under the ROC curve was .68 (95% CI .61-.73). The application of the model significantly changed the post-test probability of having an MDRO infection, identifying patients with nosocomial infection at very low risk (8%) and patients with community-acquired infections at significant risk (36%). CONCLUSION: This model achieved adequate performance and could be used to improve the selection of empiric antibiotics, aligning with other antibiotic stewardship program strategies.

Genome characterization of a multi-drug resistant Escherichia coli strain, L1PEag1, isolated from commercial cape gooseberry fruits (Physalis peruviana L.).

Introduction: Foodborne infections, which are frequently linked to bacterial contamination, are a serious concern to public health on a global scale. Whether agricultural farming practices help spread genes linked to antibiotic resistance in bacteria associated with humans or animals is a controversial question. Methods: This study applied a long-read Oxford Nanopore MinION-based sequencing to obtain the complete genome sequence of a multi-drug resistant Escherichia coli strain (L1PEag1), isolated from commercial cape gooseberry fruits (Physalis peruviana L.) in Ecuador. Using different genome analysis tools, the serotype, Multi Locus Sequence Typing (MLST), virulence genes, and antimicrobial resistance (AMR) genes of the L1PEag1 isolate were determined. Additionally, in vitro assays were performed to demonstrate functional genes. Results: The complete genome sequence of the L1PEag1 isolate was assembled into a circular chromosome of 4825.722 Kbp and one plasmid of 3.561 Kbp. The L1PEag1 isolate belongs to the B2 phylogroup, sequence type ST1170, and O1:H4 serotype based on in silico genome analysis. The genome contains 4,473 genes, 88 tRNA, 8 5S rRNA, 7 16S rRNA, and 7 23S rRNA. The average GC content is 50.58%. The specific annotation consisted of 4,439 and 3,723 genes annotated with KEEG and COG respectively, 3 intact prophage regions, 23 genomic islands (GIs), and 4 insertion sequences (ISs) of the ISAs1 and IS630 families. The L1PEag1 isolate carries 25 virulence genes, and 4 perfect and 51 strict antibiotic resistant gene (ARG) regions based on VirulenceFinder and RGI annotation. Besides, the in vitro antibiotic profile indicated resistance to kanamycin (K30), azithromycin (AZM15), clindamycin (DA2), novobiocin (NV30), amikacin (AMK30), and other antibiotics. The L1PEag1 isolate was predicted as a human pathogen, matching 464 protein families (0.934 likelihood). Conclusion: Our work emphasizes the necessity of monitoring environmental antibiotic resistance, particularly in commercial settings to contribute to develop early mitigation techniques for dealing with resistance diffusion.

Optimising antibacterial utilisation in Argentine intensive care units: a quality improvement collaborative.

BACKGROUND: There is limited evidence from antimicrobial stewardship programmes in less-resourced settings. This study aimed to improve the quality of antibacterial prescriptions by mitigating overuse and promoting the use of narrow-spectrum agents in intensive care units (ICUs) in a middle-income country. METHODS: We established a quality improvement collaborative (QIC) model involving nine Argentine ICUs over 11 months with a 16-week baseline period (BP) and a 32-week implementation period (IP). Our intervention package included audits and feedback on antibacterial use, facility-specific treatment guidelines, antibacterial timeouts, pharmacy-based interventions and education. The intervention was delivered in two learning sessions with three action periods along with coaching support and basic quality improvement training. RESULTS: We included 912 patients, 357 in BP and 555 in IP. The latter had higher APACHE II (17 (95% CI: 12 to 21) vs 15 (95% CI: 11 to 20), p=0.036), SOFA scores (6 (95% CI: 4 to 9) vs 5 (95% CI: 3 to 8), p=0.006), renal failure (41.6% vs 33.1%, p=0.009), sepsis (36.1% vs 31.6%, p<0.001) and septic shock (40.0% vs 33.8%, p<0.001). The days of antibacterial therapy (DOT) were similar between the groups (change in the slope from BP to IP 28.1 (95% CI: -17.4 to 73.5), p=0.2405). There were no differences in the antibacterial defined daily dose (DDD) between the groups (change in the slope from BP to IP 43.9, (95% CI: -12.3 to 100.0), p=0.1413).The rate of antibacterial de-escalation based on microbiological culture was higher during the IP (62.0% vs 45.3%, p<0.001).The infection prevention control (IPC) assessment framework was increased in eight ICUs. CONCLUSION: Implementing an antimicrobial stewardship program in ICUs in a middle-income country via a QIC demonstrated success in improving antibacterial de-escalation based on microbiological culture results, but not on DOT or DDD. In addition, eight out of nine ICUs improved their IPC Assessment Framework Score.

Investigating antimicrobial-resistant bacteria from exotic domestic birds - a One Health concern.

Antimicrobial resistance is a natural mechanism in microorganisms, making the treatment of infections more complex in human and veterinary medicine. Global exotic and ornamental bird markets have significantly increased, and the close relationship between pets and humans makes exploring the potential role of these birds as vectors for the spread of antimicrobial-resistant bacteria imperative. This study aimed to use culture-dependent methods to investigate cloacal bacteria and the presence of antibiotic-resistant bacteria in four breeding stocks of ornamental birds. Cloacal swab samples were collected from 53 birds (canaries = 32, cockatiels = 17, and budgies = 4) and used for culturing and isolating facultative anaerobic and/or obligatory aerobic Gram-positive and Gram-negative bacteria. The antimicrobial susceptibility profile of each isolate was determined by the disk diffusion method. Thirty-four isolates were obtained, most of which belonged to the Staphylococcus genus. Bacterial richness was higher in canaries and in one of the breeding stockings, where Gram-negative bacteria were more abundant than in the others. In addition, canaries exhibited a predominance of resistant isolates, particularly multidrug-resistant strains, probably due to prophylactic antimicrobial usage. Most Gram-negative bacteria were resistant to at least one drug tested. A vancomycin-resistant Enterococcus faecalis strain was isolated. Most Staphylococcus strains were resistant to gentamycin, followed by penicillin. Eight strains were cefoxitin-resistant, including oxacillin-resistant S. epidermidis, in which the mecA gene was detected. Understanding the prevalence of resistance in avian species is crucial in the collaborative pursuit of maintaining antibiotic effectiveness and strengthening public health defense against emerging infectious risks.

A resistência antimicrobiana é um mecanismo natural dos microrganismos, complicando o tratamento de infecções na medicina humana e veterinária. O mercado global de aves exóticas e ornamentais cresceu significativamente, e a relação próxima entre esses animais e humanos destaca a necessidade de investigar o papel das aves na disseminação de bactérias resistentes. Este estudo utilizou métodos dependentes de cultura para examinar bactérias cloacais e a presença de resistência a antibióticos em quatro plantéis de aves ornamentais. Amostras de suabe cloacal foram coletadas de 53 aves (canários = 32, calopsitas = 17, periquitos = 4) e usadas para cultivar e isolar bactérias Gram-positivas e Gram-negativas, facultativas anaeróbias e aeróbias obrigatórias. A suscetibilidade antimicrobiana foi determinada pelo método de difusão em disco. Foram obtidos 34 isolados, principalmente do gênero Staphylococcus. A riqueza bacteriana foi maior nos canários e em um dos plantéis, onde houve aumento de Gram-negativos. Canários mostraram predominância de isolados resistentes, especialmente cepas multirresistentes, provavelmente devido ao uso profilático de antimicrobianos. A maioria das bactérias Gram-negativas foi resistente a pelo menos um fármaco testado. Um Enterococcus faecalis resistente à vancomicina foi isolado. A maioria dos Staphylococcus foi resistente à gentamicina e penicilina; oito cepas foram resistentes à cefoxitina, incluindo S. epidermidis resistente à oxacilina com o gene mecA detectado. Compreender a prevalência de resistência em aves é crucial para manter a eficácia dos antibióticos e fortalecer a saúde pública contra riscos infecciosos emergentes.

Determinantes estructurales de la salud y resistencia a los antibióticos en América Latina: revisión sistemática

Objetivo: Determinar la influencia de los determinantes sociales de la salud en la resistencia antibiótica, en los países de América Latina. Metodología: Estudio documental de tipo revisión sistemática, con análisis interpretativo de la información, se incluyeron a artículos publicados entre 2018 y 2023 de las bases de datos: PubMed, ScienceDirect, Cochrane, Dialnet, Google académico, BVS, LilaCs, Scielo, Epistemonikos, CUIDEN, TripDatabase, BASE Search, Jurn, WorldWideScience, Refseek, Redalyc, EbscoHost y CONRICYT; en los idiomas español, inglés y portugués, que tuvieran como población comunidades y países de América Latina; se excluyeron aquellos con enfoque veterinario o agropecuario. Resultados: Se obtuvieron 4,625 en la búsqueda inicial y posterior a la aplicación de criterios de selección, se analizaron 28 artículos analizó la calidad metodológica, la bibliometría y el análisis temático a través de la interpretación de la información contenida. Conclusión: Los determinantes sociales de la salud estructurales asociados con la resistencia antimicrobiana fueron las políticas públicas, el género, los factores macroeconómicos, el nivel socioeconómico familiar, educativo y la gobernanza.

Objective: Determine the influence of social determinants of health on antibiotic resistance in Latin American countries. Methodology: Systematic review type documentary study with interpretive analysis of the information, articles published between 2018 and 2023 from the following databases were included: PubMed, ScienceDirect, Cochrane, Dialnet, Google scholar, BVS, LilaCs, SciELO, Epistemonikos, CUIDEN, TripDatabase, BASE Search, Jurn, WorldWideScience, Refseek, Redalyc, EbscoHost and CONRICYT; in the Spanish, English and Portuguese languages, which had Latin American communities and countries as their population; Those with a veterinary or agricultural focus were excluded. Results: 4,625 were obtained in the initial search and after the application of selection criteria, 28 articles were analyzed that analyzed the methodological quality, bibliometrics and thematic analysis through the interpretation of the information contained. Conclusion: The social determinants of structural health associated with antimicrobial resistance were public policies, gender, macroeconomic factors, family socioeconomic level, education, and governance.

Comparative genomics of IncQ1 plasmids carrying blaGES variants from clinical and environmental sources in Brazil.

IncQ-type plasmids have become important vectors in the dissemination of blaGES among different bacterial genera and species from different environments around the world, and studies estimating the occurrence of Guiana extended-spectrum (GES)-type ß-lactamases are gaining prominence. We analyzed the genetic aspects of two IncQ1 plasmids harboring different blaGES variants from human and environmental sources. The blaGES variants were identified using polymerase chain reaction (PCR) in Aeromonas veronii isolated from hospital effluent and Klebsiella variicola isolated from a rectal swab of a patient admitted to the cardiovascular intensive care unit in a different hospital. Antimicrobial-susceptibility testing and transformation experiments were performed for phenotypic analysis. Whole-genome sequencing was performed using Illumina and Oxford Nanopore platforms. The comparative analysis of plasmids was performed using BLASTn, and the IncQ1 plasmids showed a high identity and similar size. A. veronii harbored blaGES-7 in a class 1 integron (In2061), recently described by our group, and K. variicola carried blaGES-5 in the known class 1 integron. Both integrons showed a fused gene cassette that encodes resistance to aminoglycosides and fluoroquinolones, with an IS6100 truncating the 3'-conserved segment. The fused genes are transcribed together, although the attC site is disrupted. These gene cassettes can no longer be mobilized. This study revealed a mobilome that may contribute to the dissemination of GES-type ß-lactamases in Brazil. Class 1 integrons are hot spots for bacterial evolution, and their insertion into small IncQ-like plasmids displayed successful recombination, allowing the spread of blaGES variants in various environments. Therefore, they can become prevalent across clinically relevant pathogens.

Serodiversity, antibiotic resistance, and virulence genes of Vibrio parahaemolyticus in oysters collected in coastal areas of northwestern Mexico between 2012 and 2020.

This study aimed to determine the prevalence of V. parahaemolyticus in oysters from the northwestern coast of Mexico and to identify the serotypes, virulence factors, and antibiotic resistance of the strains. Oyster samples were collected from 2012 to 2020 from the northwest coast of Mexico; biochemical and molecular methods were used to identify V. parahaemolyticus from oysters; antiserum reaction to determine V. parahaemolyticus serotypes, and PCR assays were performed to identify pathogenic (tdh and/or trh) or pandemic (toxRS/new, and/or orf8) strains and antibiotic resistance testing. A total of 441 oyster samples were collected and tested for V. parahaemolyticus. Forty-seven percent of oyster samples were positive for V. parahaemolyticus. Ten different O serogroups and 72 serovars were identified, predominantly serotype O1:KUT with 22.2% and OUT:KUT with 17.3%. Twenty new serotypes that had not been previously reported in our region were identified. We detected 4.3% of pathogenic clones but no pandemic strains. About 73.5% of strains were resistant to at least one antibiotic, mainly ampicillin and ciprofloxacin; 25% were multi-drug resistant. In conclusion, the pathogenic strains in oysters and antibiotic resistance are of public health concern, as the potential for outbreaks throughout northwestern Mexico is well established.

Molecular and Phylogenomic Analysis of a Vancomycin Intermediate Resistance USA300LV Strain in Chile.

Antimicrobial resistance is a major global health problem, and, among Gram-positive bacteria, methicillin-resistant Staphylococcus aureus (MRSA) represents a serious threat. MRSA causes a wide range of infections, including bacteremia, which, due to the limited use of ß-lactams, is difficult to treat. This study aimed to analyze 51 MRSA isolates collected in 2018 from samples of patients with bacteremia from two hospitals of the Metropolitan Health Service of Santiago, Chile, both in their resistance profile and in the identification of virulence factors. In addition, genomic characterization was carried out by the WGS of an isolate that was shown to be the one of greatest concern (N°. 42) due to its intermediate resistance to vancomycin, multiple virulence factors and being classified as ST8 PVL-positive. In our study, most of the isolates turned out to be multidrug-resistant, but there are still therapeutic options, such as tetracycline, rifampicin, chloramphenicol and vancomycin, which are currently used for MRSA infections; however, 18% were PVL positive, which suggests greater virulence of these isolates. It was determined that isolate N°42 is grouped within the USA300-LV strains (ST8, PVL+, COMER+); however, it has been suggested that, in Chile, a complete displacement of the PVL-negative ST5 clone has not occurred.

Characterization of Clostridioides difficile Persister Cells and Their Role in Antibiotic Tolerance.

Clostridioides difficile is a Gram-positive pathogen known for its toxin production and spore formation. It is primarily responsible for most cases of antibiotic-associated diarrhea. Bacterial persisters are a small subset of the population that exhibits transient tolerance to bactericidal substances, and they are of significant medical concern due to their association with the emergence of antibiotic resistance and difficult-to-treat chronic or recurrent infections. Vancomycin, the predominant antibiotic utilized in the management of C. difficile infection, is extensively applied in the realm of clinical practice. Previous studies have demonstrated a persister-like phenotype with treatments involving this antibiotic. However, the mechanism in C. difficile remains largely unknown, primarily due to the challenge of isolating this small population at any given time. To better characterize C. difficile persister cells, we present a study that enables the enrichment and characterization of persister cells from bacterial cultures in both the exponential and stationary phases. Moreover, we could differentiate between triggered (induced using antibiotics such as vancomycin) and spontaneous (stochastic) persister cells. Additionally, we observed the involvement of toxin-antitoxin systems and Clp proteases in persister cell formation.

Point Mutations in Furazolidone and Rifampicin Resistance Genes in Helicobacter pylori Strains from Colombia.

The eradication of Helicobacter pylori is a valid strategy for preventing gastric cancer; however, the therapeutic failure of first-line treatments in Colombia is associated with high resistance to metronidazole and amoxicillin. This study explored alternative antibiotics and analyzed point mutations in resistance genes to furazolidone and rifampicin in order to include them in rescue therapy regimens. A total of 239 complete genomes of Helicobacter pylori Colombian strains were compared to that of the ATCC 26695 strain to identify mutations in the rpoB and porD genes for rifampicin and furazolidinone resistance, respectively. While rifampicin resistance mutations were not found, only 0.84% of the isolates showed the porD gene, suggesting that Helicobacter pylori is sensitive to these antibiotics. A phylogenomic analysis of Helicobacter pylori revealed an independent lineage in Colombia (hspColombia). The absence of point mutations in the rpoB gene, together with the scarce mutations identified in the porD gene of Helicobacter pylori, suggest that the hspColombia isolates are sensitive to rifampicin and furazolidone, which could be key to including these antibiotics in the rescue therapies against Helicobacter pylori.

Essential Oil of Fractionated Oregano as Motility Inhibitor of Bacteria Associated with Urinary Tract Infections.

In this research, several analyses were carried out on concentrated fractions of Mexican oregano essential oil (Poliomintha longiflora Gray) in order to determine its ability to inhibit the growth and the motility of Escherichia coli (swimming), Pseudomonas aeruginosa (swimming), and Proteus vulgaris (swarming); these Gram-negative bacteria associated with urinary tract infections are motile due to the presence of flagella, which is considered an important virulence factor that favors their motility when trying to reach the target organ and cause an infection. Also, the resistance pattern to antibiotics of each strain was determined. The results showed resistance pattern (8 out of 12 antibiotics tested) for P. aureginosa, while E. coli and P. vulgaris were resistant to 4 antibiotics out of the 12 tested. On the other hand, fractionated oregano caused an inhibition of growth and a reduction in motility, varying between fractions and among bacteria. Fraction 4 showed major growth reduction, with MBC values ranging from 0.002 to 23.7 mg/mL. Treatment with fractionated oregano (F1, F2, F3, F4) reduced the motility by 92-81% for P. vulgaris, 90-83% for E. coli, and 100-8.9% for P. aeruginosa. These results demonstrated a higher performance with a lower application dose due to its high content of Carvacrol and Thymol; unlike other concentrated fractions, this synergy of oxygenated monoterpenes may cause greater antimicrobial activity.

Characterization of carbapenemase-producing Enterobacterales from rectal swabs of patients in the intensive care units of a tertiary hospital in Cali-Colombia.

Background: Carbapenemase-producing Enterobacterales (CPE) represents a significant threat to global health. This study aimed to characterize clinically and molecularly the CPE isolated from rectal swabs of patients in the intensive care units (ICUs) of a tertiary hospital in Cali, Colombia. Methods: This was a cross-sectional observational study. Rectal swabs from patients admitted to the ICUs were collected. Bacterial identification and carbapenemase production were determined using phenotypic and molecular methods. Demographic and clinical data were extracted from electronic medical records. Results: The study included 223 patients. Thirty-six patients (36/223, 16.14 %) were found to be colonized or infected by CPE. Factors such as prolonged stay in the ICU, previous exposure to carbapenem antibiotics, use of invasive procedures, and admission due to trauma were associated with CPE. Klebsiella pneumoniae (52.5 %) was the most prevalent microorganism, and the dominant carbapenemases identified were KPC (57.8 %) and NDM (37.8 %). Conclusion: Distinguishing carbapenemase subtypes can provide crucial insights for controlling dissemination in ICUs in Cali, Colombia.

Group A streptococcus isolated in Guyana with reduced susceptibility to ß-lactam antibiotics.

Introduction. Streptococcus pyogenes [group A streptococci (GAS)] is the causative agent of pharyngitis and various other syndromes involving cellulitis, streptococcal toxic shock syndrome (STSS), and necrotising fasciitis. Although the prevalence of GAS infections globally remains high, necessitating the widespread use of ß-lactam antibiotics, GAS have remained largely susceptible to these agents. However, there have been several reports of GAS with reduced susceptibility harbouring mutations in genes for penicillin-binding proteins (PBPs). The objectives of this study were to examine the in vitro ß-lactam susceptibility patterns of group A streptococci, determine the prevalence of drug resistance, and ascertain whether such resistance could be attributed to mutations in specific PBP genes. Methods. In this study, we sought to use Sanger sequencing to identify mutations in PBP genes of Streptococcus pyogenes isolated from patients that required inpatient and outpatient care that could confer reduced PBP affinity for penicillin and/or cephalosporin antibiotics. All isolates were screened for susceptibility to penicillin, amoxicillin, and cefazolin using E-test strips. Results. While there were no documented cases of reduced susceptibility to penicillin or amoxicillin, 13 isolates had reduced susceptibility to cefazolin. Examination of pbp1a by Sanger sequencing revealed several isolates with single amino acid substitutions, which could potentially reduce the affinity of PBP 1A for cefazolin and possibly other first-generation cephalosporins. Conclusion. Penicillin and penicillin-derived antibiotics remain effective treatment options for GAS infections, but active surveillance is needed to monitor for changes to susceptibility patterns against these and other antibiotics and understand the genetic mechanisms contributing to them.

Inside-out, antimicrobial resistance mediated by efflux pumps in clinical strains of Acinetobacter baumannii isolated from burn wound infections.

Acinetobacter baumannii belongs to the ESKAPE group. It is classified as a critical priority group by the World Health Organization and a global concern on account of its capacity to acquire and develop resistance mechanisms to multiple antibiotics. Data from the United States indicates 500 deaths annually. Resistance mechanisms of this bacterium include enzymatic pathways such as ß-lactamases, carbapenemases, and aminoglycoside-modifying enzymes, decreased permeability, and overexpression of efflux pumps. A. baumannii has been demonstrated to possess efflux pumps, which are classified as members of the MATE family, RND and MFS superfamilies, and SMR transporters. The aim of our work was to assess the distribution of efflux pumps and their regulatory gene expression in clinical strains of A. baumannii isolated from burned patients. METHODS: From the Clinical Microbiology Laboratory at the Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra collection in Mexico, 199 strains were selected. Antibiotics susceptibilities were performed by broth microdilutions to determine minimal inhibitory concentrations. Phenotypic assays with efflux pump inhibitors were conducted using carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and phenylalanine-arginine ß-naphthylamide (PAßN) in conjunction with amikacin, ceftazidime, imipenem, meropenem and levofloxacin. A search was conducted for structural genes that are linked to efflux pumps, and the relative expression of the adeR, adeS, and adeL genes was analyzed. RESULTS: Among a total of 199 strains, 186 exhibited multidrug resistance (MDR). Fluoroquinolones demonstrated the highest resistance rates, while minocycline and amikacin displayed comparatively reduced resistance rates (1.5 and 28.1, respectively). The efflux activity of fluorquinolones exhibited the highest phenotypic detection (from 85 to 100%), while IMP demonstrated the lowest activity of 27% with PAßN and 43.3% with CCCP. Overexpression was observed in adeS and adeL, with adeR exhibiting overexpression. Concluding that clinical strains of A. baumannii from our institution exhibited efflux pumps as one of the resistance mechanisms.

Effects of antibiotics on the anti-tumor efficacy of immune checkpoint inhibitor therapy.

PURPOSE: Immunotherapy using immune checkpoint inhibitors (ICIs) has shown several benefits over traditional therapies. However, the eligible population remains small. Antibiotic (ATB) use might reduce immunotherapy efficacy by disrupting the gut microbiota. However, in China, ATB effect on ICI therapy efficacy remains unelucidated. We aimed to assess the effects of ATBs on the anti-tumor efficacy of ICIs to provide a reference for clinical use. METHODS: We included 134 patients with advanced tumors undergoing ICI therapy at Shanghai Jiading District Central Hospital from January 1, 2021, to October 1, 2023. They were divided into Non-ATB and ATB groups based on ATB use within 30 days before and after ICI administration. Moreover, we compared progression-free (PFS) and overall (OS) survival between the groups. RESULTS: Median PFS and OS were lower in the ATB than in the Non-ATB group (PFS: 4.0 vs. 5.5 months; OS: 5.4 vs. 6.5 months). Univariate analysis revealed that ATB use significantly affected PFS (hazard ratio [HR] = 2.318, 95% confidence interval [CI] = 1.281-4.194, P = 0.005) and OS (HR = 2.115, 95% CI = 1.161-3.850, P = 0.014). Moreover, multivariate analysis revealed poor PFS (HR = 2.573, 95% CI = 1.373-4.826, P = 0.003) and OS (HR = 2.452, 95% CI = 1.298-4.632, P = 0.006) in patients who received ATBs during ICI therapy. CONCLUSIONS: ATB use is negatively correlated with ICI therapy efficacy, leading to reduced PFS and OS in patients undergoing such treatment. Owing to the significant impact of ATBs on the human gut microbiome, regulation of the gut microbiome may emerge as a novel therapeutic target that can enhance the clinical activity of ICIs.

Seven-day antibiotic therapy for Enterobacterales bacteremia in high-risk neutropenic patients: toward a new paradigm.

PURPOSE: Data on short courses of antibiotic therapy for Enterobacterales bacteremia in high-risk neutropenic patients are limited. The aim of the study was to describe and compare the frequency of bacteremia relapse, 30-day overall and infection-related mortality, Clostridiodes difficile infection and length of hospital stay since bacteremia among those who received antibiotic therapy for 7 or 14 days. METHODS: This is a multicenter, prospective, observational cohort study in adult high-risk neutropenic patients with hematologic malignancies or hematopoietic stem cell transplant and monomicrobial Enterobacterales bacteremia. They received appropriate empirical antibiotic therapy, had a clinical response within 7 days, and infection source control. Clinical, epidemiological and outcomes variables were compared based on 7 or 14 days of AT. RESULTS: Two hundred patients were included (100, 7-day antibiotic therapy; 100, 14-day antibiotic therapy). Escherichia coli was the pathogen most frequently isolated (47.5%), followed by Klebsiella sp. (40.5%). Among those patients that received 7-day vs. 14-day antibiotic course, a clinical source of bacteremia was found in 54% vs. 57% (p = 0.66), multidrug-resistant Enterobacterales isolates in 28% vs. 30% (p = 0.75), and 40% vs. 47% (p = 0.31) received combined empirical antibiotic therapy. Overall mortality was 3% vs. 1% (p = 0.62), in no case related to infection; bacteremia relapse was 7% vs. 2% (p = 0.17), and length of hospital stay since bacteremia had a median of 9 days (IQR: 7-15) vs. 14 days (IQR: 13-22) (p = < 0.001). CONCLUSIONS: These data suggest that seven-day antibiotic therapy might be adequate for patients with high-risk neutropenia and Enterobacterales bacteremia, who receive appropriate empirical therapy, with clinical response and infection source control.

Antibiofilm effect of biogenic silver nanoparticle alone and combined with polymyxin B against carbapenem-resistant Acinetobacter baumannii.

Acinetobacter baumannii is a bacteria associated with nosocomial infections and outbreaks, difficult to control due to its antibiotic resistance, ability to survive in adverse conditions, and biofilm formation adhering to biotic and abiotic surfaces. Therefore, this study aimed to evaluate the antibiofilm activity of biogenic silver nanoparticle (Bio-AgNP) and polymyxin B alone and combined in biofilms formed by isolates of carbapenem-resistant A. baumannii (CR-Ab). In the biofilm formation inhibition assay, CR-Ab strains were exposed to different concentrations of the treatments before inducing biofilm formation, to determine the ability to inhibit/prevent bacterial biofilm formation. While in the biofilm rupture assay, the bacterial biofilm formation step was previously carried out and the adhered cells were exposed to different concentrations of the treatments to evaluate their ability to destroy the bacterial biofilm formed. All CR-Ab isolates and ATCC® 19606™ used in this study are strong biofilm formers. The antibiofilm activity of Bio-AgNP and polymyxin B against CR-Ab and ATCC® 19606™ demonstrated inhibitory and biofilm-disrupting activity. When used in combination, Bio-AgNP and polymyxin B inhibited 4.9-100% of biofilm formation in the CR-Ab isolates and ATCC® 19606™. Meanwhile, when Bio-AgNP and polymyxin B were combined, disruption of 6.8-77.8% of biofilm formed was observed. Thus, antibiofilm activity against CR-Ab was demonstrated when Bio-AgNP was used alone or in combination with polymyxin B, emerging as an alternative in the control of CR-Ab strains.

Effects of a mixed additive based on Saccharomyces cerevisiae and Lactobacillus rhamnosus on broilers exposed to aflatoxin B1 by contaminated feed.

The objective of the present study was to explore the influence of dietary supplementation with a mixed additive (MA) containing a probiotic and anti-mycotoxin (Saccharomyces cerevisiae RC016 and Lactobacillus rhamnosus RC007) and its interaction on the performance and health (biochemistry and liver/intestine histopathology) of broilers fed diets contaminated with aflatoxin B1 (AFB1) at 506000±22.1ng/kg. The MA contained S. cerevisiae RC016 (1×107cells/g) and L. rhamnosus RC007 (1×108cells/g) in relation 1:1. A total of sixty-one-day-old Cobb broilers were randomly allocated into four treatment groups with three replicates of 5 birds each for a five-week-old feeding experiment. The experimental diet for each treatment (T) was formulated as follows: T1, a commercial diet (CD); T2, CD+AFB1; T3, CD+0.1% MA; T4, CD+AFB1+0.1% MA. The MA improved (p<0.01) production parameters (weight gain, conversion rate, and carcass yield) and reduced (p<0.01) the toxic effect of AFB1 on the relative weight of the livers. In addition, the macro and microscopic alterations of livers and the possible intestinal injury related to histological damage in the presence of mycotoxin were reduced. The use of probiotic MA based on S. cerevisiae RC016 and L. rhamnosus RC007 in animal feed provides greater protection against mycotoxin contamination and is safe for use as a supplement in animal feed, providing beneficial effects that improve animal health and productivity. This is of great importance at the economic level for the avian production system.