High Rates of Extensively Drug-Resistant Pseudomonas aeruginosa in Children with Cystic Fibrosis.

Pseudomonas aeruginosa has a high adaptive capacity, favoring the selection of antibiotic-resistant strains, which are currently considered a global health problem. The purpose of this work was to investigate the rate and distribution of extensively drug-resistant (XDR) P. aeruginosa in pediatric patients with cystic fibrosis (CF) with recurrent infections and to distinguish the current efficacy of antibiotics commonly used in eradication therapy at a Mexican institute focused on children. A total of 118 P. aeruginosa isolates from 25 children with CF (2015-2019) underwent molecular identification, antimicrobial sensitivity tests, and Random Amplified Polymorphic DNA genotyping (RAPD-PCR). The bacterial isolates were grouped in 84 RAPD profiles, revealing a cross-infection between two sisters, whose resistance profile remained unchanged for more than 2 years. Furthermore, 77.1% (91/118) and 51.7% (61/118) of isolates showed in vitro susceptibility to ceftazidime and amikacin, respectively, antibiotics often used in eradication therapy at our institution. As well, 42.4% (50/118) were categorized as multi-drug resistant (MDR) and 12.7% (15/118) were XDR. Of these resistant isolates, 84.6% (55/65) were identified from patients with recurrent infections. The high frequency of XDR strains in children with CF should be considered a caution mark, as such resistance patterns are more commonly found in adult patients. Additionally, amikacin may soon prove ineffective. Careful use of available antibiotics is crucial before therapeutic possibilities are reduced and "antibiotic resistance crisis" worsens.

The Skin Microbiome of Patients With Atopic Dermatitis Normalizes Gradually During Treatment.

Background: Atopic dermatitis (AD) is characterized by an altered skin microbiome dominantly colonized by S. aureus. Standard treatment includes emollients, anti-inflammatory medications and antiseptics. Objectives: To characterize changes in the skin microbiome during treatment for AD. Methods: The skin microbiomes of children with moderate-to-severe AD and healthy children were investigated in a longitudinal prospective study. Patients with AD were randomized to receive either standard treatment with emollients and topical corticosteroids or standard treatment with the addition of dilute bleach baths (DBB) and sampled at four visits over a three-month period. At each visit, severity of AD was measured, swabs were taken from four body sites and the composition of the microbiome at those sites was assessed using 16S rRNA amplification. Results: We included 14 healthy controls and 28 patients. We found high relative abundances of S. aureus in patients, which correlated with AD severity and reduced apparent alpha diversity. As disease severity improved with treatment, the abundance of S. aureus decreased, gradually becoming more similar to the microbiomes of healthy controls. After treatment, patients who received DBB had a significantly lower abundance of S. aureus than those who received only standard treatment. Conclusions: There are clear differences in the skin microbiome of healthy controls and AD patients that diminish with treatment. After three months, the addition of DBB to standard treatment had significantly decreased the S. aureus burden, supporting its use as a therapeutic option. Further study in double-blinded trials is needed.

Study of simultaneous experimental colonization of Meriones unguiculatus (Mongolian gerbils) by cagPAI+ and cagPAI- strains of Helicobacter pylori.

Helicobacter pylori has a chromosomal pathogenicity island (cagPAI), and the presence or absence of this Island places the microorganism into two types of strains: cagPAI+ which is associated to serious infectious processes, and cagPAI- related to mild to moderate infectious events. Simultaneous colonization by cagPAI+ and cagPAI- strains is frequent and these bacteria can interact among themselves. The aim of this project was to analyze the interaction between cagPAI+ and cagPAI- strains of H. pylori in experimental infection, using the Mongolian gerbil as an experimental animal model. We employed J99 (cagPAI+) and 251F (cagPAI-) strains, and obtained 3 derivate strains in successive isolation from experimentally infected gerbils. By RAPD-PCR we found that cagPAI+ and cagPAI- underwent genetic rearrangement during the gerbil-adaptation process. We identified individual isolates from gerbils, and by in situ hybridization we established that both type of strains were able to colonize the same regions of the host's stomach, and induce a mild to moderate inflammatory process. We studied the competence between cagPAI+ and cagPAI- strains by simultaneous and sequential infections. The study shows that in both colonization experiments, the cagPAI- strains were more efficient than cagPAI+ strains in colonizing the infected host by displacing cagPAI+.

[RAPD-PCR characterization of Pseudomonas aeruginosa strains obtained from cystic fibrosis patients]. / Caracterización, por RAPD-PCR, de aislados de Pseudomonas aeruginosa obtenidos de pacientes con fibrosis quística.

OBJECTIVE: To characterize P. aeruginosa strains isolated from bronchoalveolar lavage fluid of cystic fibrosis (CF) patients over a 3 year period. MATERIAL AND METHODS: A prospective follow-up study was carried out in a population of cystic fibrosis patients. The random amplified polymorphic DNA (RAP.D) technique was used to amplify DNA of P. aeruginosa strains isolated from bronchoalveolar lavage fluid samples of five CF patients from the Servicio de Neumología y Cirugía del Tórax del Instituto Nacional de Pediatría (Mexico City Chest Clinic of the National Pediatrics Institute) in Mexico City, between June 1996 and June 2002. Amplification patterns were established for each isolate to accurately identify all strains and to carry out an epidemiological analysis of P. aeruginosa among the selected CF patients. RESULTS: Eighteen different DNA amplification patterns were defined and used to identify each P. aeruginosa strain isolated from the different bronchoalveolar lavage samples. No correlation was observed between the different P. aeruginosa strain genotypes and mucoid or non-mucoid phenotypes, as strains with different phenotypes showed similar amplification patterns. Several strains with different amplification patterns were identified in samples obtained from the same patient, suggesting coinfection with ore than one P. aeruginosa strain. Two siblings with CF shared similargenotypes, suggesting the occurrence of cross- contamination. Similar genotypes of P. aeruginosa strains were isolated throughout the study period. CONCLUSION: Genotypic characterization of P. aeruginosa strains in CF patients allows more accurate epidemiological analyses of this important host-agent relationship.

Caracterización, por RAPD-PCR, de aislados de Pseudomonas aeruginosa obtenidos de pacientes con fibrosis quística / RAPD-PCR characterization of Pseudomonas aeruginosa strains obtained from cystic fibrosis patients

OBJETIVO: Caracterizar a las cepas de P aeruginosa aisladas de lavados broncoalveolares de pacientes con fibrosis quística a lo largo de un periodo de tres años. MATERIAL Y MÉTODOS: Estudio prospectivo, de seguimiento de una población de pacientes con fibrosis quística. Se utilizó la técnica de la amplificación del ADN empleando PCR con bajas condiciones de especificidad (Random amplified polymorphic DNA, RAPD-PCR) para la amplificación del ADN de cepas de P aeruginosa aisladas de lavados broncoalveolares de cinco pacientes con fibrosis quística, provenientes del Servicio de Neumología y Cirugía del Tórax del Instituto Nacional de Pediatría de la Ciudad de México, en el periodo de junio de 1996 a junio de 2002; se establecieron los patrones de amplificación de cada aislamiento, lo que permitió la identificación precisa de todas las cepas aisladas y el estudio de la epidemiología de P aeruginosa en los pacientes seleccionados con dicha enfermedad. RESULTADOS: Se definieron 18 patrones de amplificación del ADN que permitieron identificar a cada cepa de P aeruginosa aislada en las diferentes muestras de lavado broncoalveolar; no se encontró relación entre el fenotipo de P aeruginosa (mucoide o no mucoide) y el genotipo de cada aislamiento, ya que cepas con fenotipos distintos mostraron patrones de amplificación semejantes; en nuestros pacientes se identificaron cepas con patrones de amplificación distintos a partir de una misma muestra, lo que sugiere la presencia de infecciones simultáneas por más de una cepa de P aeruginosa; se demostró que dos hermanos con la enfermedad compartían cepas con genotipos semejantes, lo que sugiere una contaminación cruzada entre ambos, y se demostró el aislamiento de cepas de P aeruginosa con genotipos semejantes a lo largo de los periodos estudiados. CONCLUSIONES: La identificación mediante la caracterización genotípica de las cepas de P aeruginosa aisladas de los pacientes con fibrosis quística permite llevar a cabo estudios más precisos de la epidemiología de esta importante relación huésped-parásito.