Activity of propyl-propane-thiosulfinate and propyl-propane-thiosulfonate against carbapenem-resistant Gram-negative bacteria.

Organosulfur compounds derived from plants of the Allium genus, such as propyl-propane-thiosulfinate (PTS) and propyl-propane-thiosulfonate (PTSO), have been proposed as an alternative in antibiotic resistance. The aim of this study was to compare the activity of these substances with other antibiotics against clinical isolates of carbapenem-resistant (CAR-R) and carbapenem-susceptible (CAR-S) Gram-negative bacteria. A total of 126 clinical isolates of CAR-R and 155 CAR-S bacteria were selected, including Enterobacterales, A. baumannii and P. aeruginosa. The antibiotic susceptibility of all isolates was assessed using the microdilution and Kirby-Bauer methods for PTS, PTSO, amoxicillin/clavulanate, piperacillin/tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, ciprofloxacin, and amikacin. Both PTS and PTSO demonstrated in vitro bactericidal activity against CAR-R Enterobacteriaceae and A. baumannii, with no significant difference in activity compared to their response against CAR-S isolates. However, both compounds were less active against P. aeruginosa than against any of the other bacteria, regardless of their resistance to carbapenems. In all cases, the minimum inhibitory concentration values of PTSO were significantly lower than those of PTS. These findings offer valuable information about the potential antibacterial use of these substances, particularly against infections that currently have limited therapeutic options.

Molecular epidemiology of carbapenem-resistant gram-negative bacilli in Ecuador.

INTRODUCTION: Carbapenem-resistant gram-negative bacilli are a worldwide concern because of high morbidity and mortality rates. Additionally, the increasing prevalence of these bacteria is dangerous. To investigate the extent of antimicrobial resistance and prioritize the utility of novel drugs, we evaluated the molecular characteristics and antimicrobial susceptibility profiles of carbapenem-resistant Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii in Ecuador in 2022. METHODS: Ninety-five clinical isolates of carbapenem non-susceptible gram-negative bacilli were collected from six hospitals in Ecuador. Carbapenem resistance was confirmed with meropenem disk diffusion assays following Clinical Laboratory Standard Institute guidelines. Carbapenemase production was tested using a modified carbapenemase inactivation method. Antimicrobial susceptibility was tested with a disk diffusion assay, the Vitek 2 System, and gradient diffusion strips. Broth microdilution assays were used to assess colistin susceptibility. All the isolates were screened for the blaKPC, blaNDM, blaOXA-48, blaVIM and blaIMP genes. In addition, A. baumannii isolates were screened for the blaOXA-23, blaOXA-58 and blaOXA-24/40 genes. RESULTS: Carbapenemase production was observed in 96.84% of the isolates. The blaKPC, blaNDM and blaOXA-48 genes were detected in Enterobacterales, with blaKPC being predominant. The blaVIM gene was detected in P. aeruginosa, and blaOXA-24/40 predominated in A. baumannii. Most of the isolates showed co-resistance to aminoglycosides, fluoroquinolones, and trimethoprim/sulfamethoxazole. Both ceftazidime/avibactam and meropenem/vaborbactam were active against carbapenem-resistant gram-negative bacilli that produce serin-carbapenemases. CONCLUSION: The epidemiology of carbapenem resistance in Ecuador is dominated by carbapenemase-producing K. pneumoniae harbouring blaKPC. Extensively drug resistant (XDR) P. aeruginosa and A. baumannii were identified, and their identification revealed the urgent need to implement strategies to reduce the dissemination of these strains.

Reliability of a Screening Method Using Antibiotic Disks to Detect Carbapenemases in Glucose-Nonfermenting Gram-Negative Microorganisms From Clinical Samples of a Regional Hospital in Southeastern Spain.

BACKGROUND: Infections by glucose-nonfermenting gram-negative bacilli (NFGNB) pose a major public health problem due to multiresistance to beta-lactam antibiotics, especially plasmid-borne carbapenemases. Their detection by microbiology laboratories is challenging, and there is a need for easy-to-use and reliable diagnostic techniques. Our objective was to evaluate an in-house screening method to presumptively detect carbapenemases in NFGNB in a simple and clinically useful manner. METHODS: The study included 175 NFGNB isolates from urinary, respiratory, and rectal samples. In a triple assay, isolates were incubated at 37°C for 24 h on three solid-culture media: MacConkey II Agar, 5% Sheep Blood Columbia Agar and Mueller Hinton II Agar; meropenem (MEM) and cefepime (FEP) disks were employed for screening. Studies were then performed on the inhibition halo diameter, scanning effects, and the appearance of mutant colonies, which were compared with those observed using the colorimetric Neo-Rapid CARB Kit and immunochromatography (NG5-Test Carba and K-Set for OXA-23). Receiver operating characteristic curves were constructed for these data. RESULTS: Carbapenemases were expressed by 79/175 (45.1%): 19 Pseudomonas aeruginosa and 60 Acinetobacter baumannii. Optimal inhibition halo diameter cutoffs to detect this resistance on 5% sheep blood agar were as follows: 6 mm (MEM) and 6.5 mm (FEP) for P. aeruginosa (in the absence of scanning effects and mutations) and 10.5 mm (MEM) and 16 mm (FEP) for A. baumannii (even in the presence of scanning effects). CONCLUSION: The combined utilization of MEM and FEP antibiotic disks in 5% sheep blood agar, measuring their inhibition haloes, offers an effective method to predict the presence of carbapenemases as resistance mechanism in P. aeruginosa and A. baumannii.

Antibiotics against Pseudomonas aeruginosa on Human Skin Cell Lines: Determination of the Highest Non-Cytotoxic Concentrations with Antibiofilm Capacity for Wound Healing Strategies.

Pseudomonas aeruginosa is one of the most common microorganisms causing infections of severe skin wounds. Antibiotic or antiseptic treatments are crucial to prevent and curb these infections. Antiseptics have been reported to be cytotoxic to skin cells and few studies evaluate the impact of commonly used antibiotics. This study evaluates how clinical antibiotics affect skin cells' viability, proliferation, migration, and cytokine secretion and defines the highest non-cytotoxic concentrations that maintain antibacterial activity. Cell proliferation, viability, and migration were evaluated on cell monolayers. Cytokines related to the wound healing process were determined. The minimum inhibitory concentrations and the impact on bacterial biofilm were assessed. Results showed that 0.02 mg/mL ciprofloxacin and 1 mg/mL meropenem are the highest non-cytotoxic concentrations for fibroblasts and keratinocytes while 1.25 mg/mL amikacin and 0.034 mg/mL colistin do not affect fibroblasts' viability and cytokine secretion but have an impact on keratinocytes. These concentrations are above the minimum inhibitory concentration but only amikacin could eradicate the biofilm. For the other antibiotics, cytotoxic concentrations are needed to eradicate the biofilm. Combinations with colistin at non-cytotoxic concentrations effectively eliminate the biofilm. These results provide information about the concentrations required when administering topical antibiotic treatments on skin lesions, and how these antibiotics affect wound management therapies. This study set the basis for the development of novel antibacterial wound healing strategies such as antibiotic artificial skin substitutes.

Preliminary reading of antibiogram by microdilution for clinical isolates in urine culture.

PURPOSE: We evaluated a modification of automated antibiograms in urine cultures designed to facilitate the early interpretation of minimum inhibitory concentrations (MICs) and accelerate the targeted treatment of urinary tract infections (UTIs), METHODS: A prospective study was conducted of 309 isolates (219 Enterobacteriaceae, 75 Enterococcus spp., and 15 non-fermenting Gram-negative bacilli (NFGNB), and a retrospective study of 9 carbapenemase-producing clinical isolates from urine cultures. Colonies grown on conventional isolation plates were inoculated in MicroScan Walkaway system panels and incubated for 7 h, using a MicroScan AutoScan-4 plate reader for preliminary MIC determination by turbidimetry. Resulting antibiograms were compared with definitive antibiograms obtained after incubation for 17 h. RESULTS: Preliminary and definitive readings were concordant for 86.7% of Gram-positive cocci isolates (65/75), 61.6% of Enterobacteriaceae (135/219), and 53.3% of NFGNB. The agreement rate was greater than 90% for most antimicrobials against Gram-positive cocci (94.7% or more) and Enterobacteriaceae, (97.2% or more for 10 of 17 antibiotics) except with nitrofurantoin (89%). The agreement rate was 86.7% or more for most antibiotics against NFGNB apart from piperacillin/tazobactam, aztreonam, amikacin, and ciprofloxacin. Gram-negative bacilli showed the highest differences in MIC values between preliminary and definitive readings. CONCLUSIONS: A preliminary antibiogram reading may be useful in urine cultures to reduce the delay before targeted antibiotherapy, especially against Enterobacteriaceae and Gram-positive cocci, but not in cases of carbapenemase-producing NFGNB. Further local studies are warranted to evaluate the usefulness of this approach in relation to resistance rates.

Antibiotic resistances of Pseudomonas aeruginosa and Acinetobacter baumannii in urine cultures: experience in a hospital of Southeast Spain.

The objectives of this study were to perform a systematic review of publications between 2010 and 2021 on the antibiotic resistance of Pseudomonas aeruginosa and Acinetobacter baumannii from urinary tract infections and to analyze changes over time in hospital urine cultures from 2016 through 2021. The literature was searched, and a retrospective cross-sectional descriptive study was performed in the hospital. Out of 21 838 positive urine cultures, 3.86% were due to P. aeruginosa and 0.44% were due to A. baumannii. For P. aeruginosa, lower resistance rates were observed to virtually all tested antibiotics than were obtained in the systematic review, and the present series of hospital samples showed an in vitro resistance rate <10% to ceftazidime, cefepime, meropenem, piperacillin-tazobactam, amikacin, tobramycin, and colistin. For A. baumannii, the resistance rates to almost all antibiotics were higher in the present series than in the systematic review, being lowest to colistin (10%). Both microorganisms show reduced in vitro susceptibility to some antibiotics during the years of the COVID-19 pandemic in comparison to previous years. In our setting, both piperacillin-tazobactam and meropenem can be recommended for the empirical treatment of UTIs by P. aeruginosa, whereas only colistin can be recommended for UTIs by A. baumannii.

Genetic Characterization of Extensively Drug-Resistant Shigella sonnei Infections, Spain, 2021-2022.

In 2022, the United Kingdom reported an increase in drug resistance in Shigella sonnei isolates. We report 33 cases in Spain genetically related to the UK cases and 4 cases with similar antimicrobial resistance profiles infected with genetically distant strains. Our results suggest circulation of multiple genetic clusters of multidrug-resistant S. sonnei in Spain.

Antibiotic Resistance Changes in Gram-Positive Bacteria from Urine Cultures: Development Analysis in a Health Area of South-East Spain.

This study analyzed the epidemiology and antibiotic susceptibility profile of significant bacteriuria and assessed the impact of adopting EUCAST criteria on antibiotic resistances. A systematic review was performed on publications in English or Spanish between 1 January 2010 and 30 June 2021 on the susceptibility of Gram-positive bacteria isolated in urinary samples in Europe. A retrospective descriptive study was also conducted on the results of 21,838 urine cultures with presumptive urinary tract infection (UTI) obtained during the past five years by the Department of Microbiology of the Virgen de las Nieves University Hospital (Granada, Spain). The activity of various antibiotics was determined, differentiated among various populations, and interpretations compared according to the application of EUCAST or CLSI criteria. Among 21,838 cases of significant bacteriuria, 27.69% were by Gram-positive bacteria, which were Enterococcus faecalis in 19.04% and Enterococcus faecium in 3.92%. The susceptibility profile remained stable for most antibiotics except for levofloxacin for E. faecalis and Staphylococcus aureus and nitrofurantoin for E. faecium. The resistance of Enterococcus spp. and Staphylococcus spp. to glycopeptides was exceptionally low in our setting. No significant difference in the prevalence of methicillin-resistant Staphylococcus aureus was observed between hospital (26.67%) and community (28.85%) samples. Resistances in our local setting remain stable and appear to be lower than reported in other studies. The adoption of EUCAST vs. CLSI criteria did not produce a general change in resistance rates. Findings suggest the need to revise certain empirical criteria, such as aminoglycoside synergy for Enterococcus and for community-origin S. aureus.

[Isolation of Haemophilus no ducreyi in samples from the genital tract of men: Its clinical relationship]. / Aislamiento de Haemophilus no ducreyi en muestras del aparato genital de varones: relación con la clínica.

INTRODUCTION: With the advancement of microbiological methods, the isolation of less typical pathogens in cases of urethral and rectal infection is more frequent, apart from the classic etiological agents. One of them is formed by species of Haemophilus no ducreyi (HND). The objective of this work is to describe frequency, susceptibility to antibiotics, and clinical features of HDN urethritis and proctitis in adult males. PATIENTS AND METHODS: This is an observational retrospective descriptive study of the results obtained by the Microbiology laboratory of the Virgen de las Nieves University Hospital on the isolates of HND in genital and rectal samples from males between 2016 and 2019. RESULTS: HND was isolated in 135 (7%) of the genital infection episodes diagnosed in men. H. parainfluenzae was the most commonly isolated (34/45; 75.6%). The most frequent symptoms in men with proctitis were rectal tenesmus (31.6%) and lymphadenopathy (10.5%); in those with urethritis, dysuria (71.6%), urethral suppuration (46.7%) and gland lesions (27%), so differentiating it from infections caused by other genitopathogens is difficult. 43% of patients were HIV positive. Antibiotic resistance rates for H. parainfluenzae were high to quinolons, ampicillin, tetracycline and macrolides. CONCLUSION: HND species should be considered as possible etiologic agents in episodes of urethral and rectal infection in men, especially in cases with negative screening tests for agents that cause sexually transmitted infections (STIs). Its microbiological identification is essential for the establishment of an effective targeted treatment.

Evolution of Antibiotic Resistance in Escherichia coli and Klebsiella pneumoniae from Urine Cultures.

OBJECTIVE: Determine the evolution of antibiotic resistance of symptomatic bacteriuria caused by Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) in Granada. MATERIAL AND METHOD: A descriptive retrospective study was carried out, including antibiograms of urine cultures in which microorganisms identified as E. coli and K. pneumoniae, were isolated in the Microbiology laboratory of the Hospital Universitario Virgen de las Nieves (Granada, Spain) between January 2016 and June 2021. RESULTS: E. coli was the most frequent isolate (10,048) and its resistance to ampicillin (59.45%) and ticarcillin (59.59%), and the increase to cefepime (15.07%) and amoxicillin-clavulanic acid (17.67%) is noteworthy. K. pneumoniae (2222) is notable for resistance to Fosfomycin (27.91%) and an increase to ciprofloxacin (37.79%) and amoxicillin-clavulanic acid (36.63%). Resistance is generally higher in hospitalized patients, males, and adults. CONCLUSIONS: Antibiotic resistance to the studied Enterobacteriaceae is on the rise, requiring empirical treatment targeted to the population area.

Outbreaks by Klebsiella oxytoca in neonatal intensive care units: Analysis of an outbreak in a tertiary hospital and systematic review.

OBJECTIVE: Klebsiella oxytoca can cause nosocomial infections, affecting vulnerable newborns. There are few studies describing nosocomial outbreaks in the neonatal intensive care units (NICU). In this study, a systematic review of the literature was carried out to know the main characteristics of these outbreaks and the evolution of one is described. METHODS: We conducted a systematic review in the Medline database up to July 2022, and present a descriptive study of an outbreak with 21 episodes in the NICU of a tertiary hospital, between September 2021 and January 2022. RESULTS: 9 articles met the inclusion criteria. The duration of outbreaks was found to be variable, of which 4 (44.4%) lasted for a year or more. Colonization (69%) was more frequent than infections (31%) and the mortality rate was 22.4%. In studies describing sources, the most frequent was the environmental origin (57.1%). In our outbreak there were 15 colonizations and 6 infections. The infections were mild conjunctivitis without sequelae. Molecular typing analysis made it possible to detect 4 different clusters. CONCLUSIONS: There is an important variability in the evolution and results of the published outbreaks, highlighting a greater number of colonized, use of PFGE (pulsed-field gel electrophoresis) techniques for molecular typing and implementation of control measures. Finally, we describe an outbreak in which 21 neonates were affected with mild infections, resolved without sequelae and whose control measures were effective.

Nosocomial outbreak caused by Serratia marcescens in a neonatology intensive care unit in a regional hospital. Analysis and improvement proposals.

OBJECTIVES: Serratia marcescens (SM) may cause nosocomial outbreaks in Neonatal Intensive Care Units (NICU). We describe an outbreak of SM in a NICU and propose additional prevention and control recommendations. METHODS: Between March 2019 and January 2020, samples were taken from patients in the NICU (rectal, pharyngeal, axillary and other locations) and from 15 taps and their sinks. Control measures were implemented including thorough cleaning of incubators, health education to staff and neonates'relatives, and use of single-dose containers. PFGE was performed in 19 isolates from patients and in 5 environmental samples. RESULTS: From the first case in March 2019 to the detection of the outbreak, a month elapsed. Finally, 20 patients were infected and 5 colonized. 80% of infected neonates had conjunctivitis, 25% bacteremia, 15% pneumonia, 5% wound infection, and 5% urinary tract infection. Six neonates had two foci of infection. Among the 19 isolates studied, 18 presented the same pulsotype and only one of the isolates from the sinkhole showed a clonal relationship with those of the outbreak. Initial measures established were ineffective to control de outbreak and were implemented with exhaustive cleaning, use of individual eye drops, environmental sampling and changing sinks. CONCLUSION: This outbreak presented a high number of neonates affected due to its late detection and torpid evolution. The microorganisms isolated from the neonates were related to an environmental isolate. Additional prevention and control measures are proposed, including routine weekly microbiological sampling.

Presence and Relevance of Emerging Microorganisms in Clinical Genitourinary Samples.

Microorganisms responsible for genitourinary infections increasingly include species other than conventional etiological agents that are of clinical and pathogenic relevance and therapeutic interest. This cross-sectional descriptive study selected samples from clinical genitourinary episodes between January 2016 and December 2019 in which emerging microbiological agents were detected. The patients' epidemiological characteristics, clinical presentation, antibiotic treatment, and outcome were studied to identify their pathogenic role. The emerging microorganisms most frequently detected in urinary tract infections were Streptococcus bovis (58.5%) and Gardnerella spp. (23.6%) in females and S. bovis (32.3%), Aerococcus urinae (18.6%), and Corynebacterium spp. (16.9%) in males, while the most frequently detected in genital infections were S. viridans (36.4%) in females and C. glucuronolyticum (32.2%) and Gardnerella spp. (35.6%) in males. All cases in female children were produced by S. bovis. Symptomatic episodes were more frequent with Aerococcus spp. and S. bovis and the presence of leukocytosis more frequent with Aerococcus spp. Quinolones and doxycycline were most often prescribed antibiotics for genital infections and quinolones and amoxicillin-clavulanic acid for urinary infections. Urinary infection by Aerococcus spp. was more frequent in males of advanced age, Corynebacterium spp. was more frequent in permanent vesical catheter carriers, and episodes of asymptomatic bacteriuria by Gardnerella spp. were more frequent in patients with kidney transplant and chronic consumers of corticosteroid therapy. Lactobacillus spp. should be considered in urinary infections of patients of advanced age and with a previous antibiotic load. Genital infection by Gardnerella spp. was significantly associated with a history of risky sexual relations.

Antibiotic Resistances of Enterobacteriaceae with Chromosomal Ampc in Urine Cultures: Review and Experience of a Spanish Hospital.

The Enterobacteriaceae Citrobacter freundii, Enterobacter cloacae, Klebsiella aerogenes, Morganella morganii, Providencia stuartii, and Serratia marcescens (CESPM group) produce numerous urinary tract infections (UTIs) which are difficult to treat due to their high multiresistance rate. The objectives of this study were to carry out a systematic review of antibiotic resistances by UTIs and to determine changes over time in urine cultures from a reference hospital in southern Spain. The literature was searched for European data on the resistance rates of each microorganism, and a retrospective cross-sectional descriptive study was performed in samples with suspicion of UTI from patients in Virgen de las Nieves University Hospital (Granada, Spain) between 2016 and the first half of 2021. Among 21,838 positive urine cultures, 1.85% were caused by E. cloacae, 0.77% by M. Morganii, 0.65% by K. aerogenes, 0.46% by C. freundii, 0.29% by P stuartii, and 0.25% by S. marcescens. The lowest resistance rates by microorganism were: E. cloacae to amikacin (3.47%) and imipenem (5.28%); M. morganii to piperacillin-tazobactam (1.79%), cefepime (4.76%), and tobramycin (7.74%); K. aerogenes to tobramycin (3.55%), gentamicin (4.25%), trimethoprim-sulfamethoxazole (4.96%), imipenem (5.75%), and cefepime (6.43%); C. freundii to imipenem (no resistance), nitrofurantoin (1.96%), fosfomycin (2.80%), and ertapenem (6.12%); P. stuartii to cefepime (3.28%) and ceftazidime (3.28%); and S. marcescens to gentamicin (1.8%), ciprofloxacin (3.64%), cefepime (3.70%), piperacillin-tazobactam (3.70%), and trimethoprim-sulfamethoxazole (5.45%). In our setting, CESMP Enterobacteriaceae showed the lowest resistance to piperacillin-tazobactam, cefepime, imipenem, gentamicin, and colistin, which can therefore be recommended for the empirical treatment of UTIs. The COVID-19 pandemic may have had a clinical impact in relation to the increased resistance of E. cloacae and M. morgani to some antibiotics.

Clinical significance of isolation of Haemophilus no ducreyi in genital samples. Systematic review.

INTRODUCTION AND OBJECTIVES: Currently, the microbiological diagnosis of genital infections is carried out with molecular methods, which allow the detection of less frequent etiological agents but with potential pathogenic importance, such as Haemophilus spp. The objective of this review is to analyse and highlight the clinical importance of the isolation of Haemophilus spp. in genital and rectal infections, excluding Haemophilus ducreyi. MATERIAL AND METHODS: A systematic review was carried out based on an exhaustive search of the publications included in the MEDLINE database up to August 5, 2021, on the presence of Haemophilus spp. in genital and rectal infections, excluding H. ducreyi. RESULTS: After reviewing what was described in the literature, Haemophilus spp. (excluding H. ducreyi: HSNOD) was detected in 2397 episodes of genital infection, the most frequently isolated species being H. influenzae and H. parainfluenzae. Most of the episodes (87,6%) are constituted by single isolation. There is a slight predominance in women (48,3%) where it can cause vaginitis, salpingitis, endometritis or complications during pregnancy. In men, the clinical picture usually corresponds to urethritis. Most of the samples correspond to vaginal and urethral exudates, with a minority representation at the rectal level (2.3%). CONCLUSION: HSNOD plays a relevant pathogenic role in episodes of genital infection, so microbiological diagnostic protocols must include methods that allow their detection, as well as include them in the etiological spectrum of this type of clinical picture.

Abnormal Alpha-1 Antitrypsin Levels and Other Risk Factors Associated with Lung Function Impairment at 6 and 12 Months after Hospitalization Due to COVID-19: A Cohort Study.

Respiratory function deficits are common sequelae for COVID-19. In this study, we aimed to identify the medical conditions that may influence lung function impairment at 12 months after SARS-CoV2 infection and to analyze the role of alpha-1 antytripsin (AAT) deficiciency (AATD). A cohort study was conducted on hospitalized COVID-19 pneumonia patients in Granada (Spain) during the first infection wave who were referred to a post-COVID-19 hospital clinic. The patients were monitored with three follow-up visits from May 2020 to May 2021. Previous medical history, hospital admission data, baseline parameters and physical examination data were collected at the first visit. Pulmonary function tests were performed at 6 and 12 months together with the determination of AAT level and AATD genotype. After 12 months, 49 out of 157 patients (31.2%) continued to have lung function impairment. A multivariate analysis showed a statistically significant association of lung function impairment with: higher Charlson index; pneumonia with a central and/or mixed distribution; anemia on admission; time in intensive care; need for corticosteroid boluses; abnormal respiratory sounds at 6 months; elevated lactate dehydrogenase at 12 months; abnormal AAT; and MZ genotype. Our results suggest that these medical conditions predispose COVID-19 patients to develop long-term lung function sequelae.

Colistin resistance screening by 3 µg/ml colistin agar in Carbapenemase-producing Enterobacterales.

BACKGROUND: In low- and middle-income countries, the use of colistin in therapeutic regimens is common, to treat infections produced for Carbapenemase-producing Enterobacterales (CPE) due to limited access to the recently discovered-approved antibiotics. Furthermore, the technical limitations to perform colistin susceptibility tests make it difficult to assess the suitability of this treatment for each patient, as well as to monitor the rates of resistance. In the present study, we describe the use of agar dilution using a unique colistin concentration of 3 µg/ml to discriminate isolates with colistin resistance in CPE obtained from clinical samples. METHODS: Clinical Laboratory Standards Institute (CLSI) colistin broth microdilution method and dilution agar with a colistin concentration of 3 µg/ml were performed in 168 isolates of CPE obtained from clinical samples in Guayaquil, Ecuador. Broth microdilution was considered our gold standard using CLSI breakpoints as reference (≤2 µg/ml intermediate and ≥4 µg/ml resistant). Categorical agreement was defined as obtaining a reading within the same category with both methodologies. RESULTS: Isolates obtained from respiratory samples were the most prevalent (26.19%; n = 44). Klebsiella pneumoniae was the predominant specie (94.04%; n = 158). KPC-like carbapenemase was present in all the isolates, and interestingly, colistin resistance was not mediated by MCR-1 production. Categorical agreement between both methods resulted in 97.02%. CONCLUSION: We propose the use of dilution agar with a colistin concentration of 3 µg/ml, as a valid method for screening colistin resistance in low- and middle-income countries to monitor resistance and to perform epidemiological studies.

Gallic Acid: A Natural Phenolic Compound Exerting Antitumoral Activities in Colorectal Cancer via Interaction with G-Quadruplexes.

Natural phenolic compounds have gained momentum for the prevention and treatment of cancer, but their antitumoral mechanism of action is not yet well understood. In the present study, we screened the antitumoral potential of several phenolic compounds in a cellular model of colorectal cancer (CRC). We selected gallic acid (GA) as a candidate in terms of potency and selectivity and extensively evaluated its biological activity. We report on the role of GA as a ligand of DNA G-quadruplexes (G4s), explaining several of its antitumoral effects, including the transcriptional inhibition of ribosomal and CMYC genes. In addition, GA shared with other established G4 ligands some effects such as cell cycle arrest, nucleolar stress, and induction of DNA damage. We further confirmed the antitumoral and G4-stabilizing properties of GA using a xenograft model of CRC. Finally, we succinctly demonstrate that GA could be explored as a therapeutic agent in a patient cohort with CRC. Our work reveals that GA, a natural bioactive compound present in the diet, affects gene expression by interaction with G4s both in vitro and in vivo and paves the way towards G4s targeting with phenolic compounds.