Hospital Central Dr. Ignacio Morones Prieto

In 2019, pneumonia caused 740,180 deaths in children under five years of age, representing 22% of global mortality in this age group. During the COVID-19 pandemic, public health interventions markedly reduced the circulation of most respiratory viruses other than SARS-CoV-2, leading to significant post-pandemic shifts in respiratory pathogen epidemiology. This study aimed to characterize the epidemiology, clinical features, and risk factors associated with respiratory viruses and bacteria causing pneumonia in Mexican children during the late pandemic and post pandemic periods. Children younger than 14 years with pneumonia were recruited from seven hospitals in Mexico. Demographic and clinical data were collected, and nasopharyngeal swabs were analyzed using a multiplex PCR panel detecting 19 viruses and 7 bacteria. Univariate, bivariate, and logistic regression analyses were performed (SPSS v25). A total of 1715 children were included: 704 during the pandemic (2021-2023) and 1011 post-pandemic (2023-2025). Co-infections (72% vs. 65%, p < 0.001), virus-virus co-infections (25% vs. 11%, p < 0.001), and single viral infections (20% vs. 15%, p = 0.007) were more frequent during the pandemic. Pathogen detection was high in both periods, though negative samples increased post-pandemic (5.4% vs. 15%, p < 0.001). During the pandemic, the 5 most frequently detected pathogens were rhinovirus (66%), RSV A and B (38%), Streptococcus pneumoniae (30%), Haemophilus influenzae (28%), human metapneumovirus (13%). In the post-pandemic period, the 5 most frequently detected pathogens were rhinovirus (52%), Haemophilus influenzae (36%), Streptococcus pneumoniae (35%), RSV A and B (28%), metapneumovirus (11%). Rhinovirus and RSV predominated during the pandemic, whereas Haemophilus influenzae, Streptococcus pneumoniae, parainfluenza viruses, Bordetella pertussis, and Mycoplasma pneumoniae significantly increased post-pandemic. Pediatric pneumonia epidemiology shifted from a predominantly viral profile during the pandemic to increased bacterial detections and virus-bacteria co-infections post-pandemic, alongside re-emergence of typical RSV and influenza seasonality. Higher mean age and rhinovirus as the most frequent pathogen persist after the pandemic. Sustained molecular surveillance and reinforced vaccination programs remain essential in the post-pandemic era.

Piperacillin-tazobactam is widely used off-label in neonates for the empirical treatment of severe infections, resulting in diverse dosing regimens across clinical settings. This variability, combined with high interindividual differences in renal maturation that impact drug disposition, complicates standardized dosing and emphasizes the need for individualized, evidence-based strategies. This study aimed to develop and evaluate a population pharmacokinetic model of piperacillin in neonates to support optimized initial dosing recommendations. Neonatal patients (postnatal age ≤28 days) admitted to an intensive care unit who received piperacillin-tazobactam (8:1 ratio) at Neofax-recommended doses were included. Plasma concentrations were measured using an ultra-high-performance liquid chromatography with tandem mass spectrometry method. Population pharmacokinetic analysis for piperacillin was performed using nonlinear mixed-effects modeling. A total of 65 blood samples were collected from 25 neonates, both preterm (56%) and full-term. Piperacillin pharmacokinetics was best described by a one-compartment model incorporating body weight-based allometric scaling, postmenstrual age, and serum creatinine as covariates influencing clearance. For a typical neonate in the study (1.76 kg), the estimated clearance was 0.748 L/h (coefficient of variation, 38.3%), and the volume of distribution was 0.866 L (37.7%). Simulations indicated adequate probability of target attainment with current recommendations, but a high proportion of preterm neonates (>75%) were at risk of overexposure (trough piperacillin plasma concentration >50 mg/L). Additional simulations supported individualized initial regimens based on renal maturation and suggested that extended infusions (1-4 h) may improve target attainment for stricter targets and less-susceptible pathogens. This study provides a validated pharmacokinetic model for piperacillin in neonates with severe infections, offering a framework to optimize empiric dosing based on renal function and developmental stage.

Objective: The aim of this case report is to show the surgical treatment of cranial fasciitis in a 2-year-old patient. Cranial fasciitis is an uncommon, nonmalignant, and swiftly proliferating lesion that primarily involves the cranium, predominantly in the temporoparietal area. It mostly comprises smooth muscle tissue, connective tissue, and diverse immune cells. The lesion often manifests as an indurated, asymptomatic mass, averaging approximately 2.5 cm in size, although it may exceed 15 cm. Cranial fasciitis predominantly manifests in children below the age of 6. The diagnosis is validated via histological investigation, which identifies a benign tumor defined by the proliferation of spindle-shaped cells organized in a myxoid matrix, frequently displaying a storiform pattern. Methods: We present a case of cranial fasciitis in a 2-year-old pediatric patient, characterized by an atypical manifestation in the maxillary region. The lesion underwent surgical intervention resulting in total excision. Results: Three years after the surgery, the patient is asymptomatic and shows no signs of recurrence. Regular clinical follow-up and imaging are scheduled biannually, and the patient is anticipated to have a favorable long-term prognosis. Conclusions: Cranial fasciitis is a very rare benign lesion that occurs more commonly in childhood. In this case, surgical resection was effective, and three years later, the patient remains asymptomatic and free of recurrence, with a favorable long-term prognosis.

Retinoblastoma (Rb1) is a gene that codes for a tumour suppressor protein involved in various types of cancer. It was first described in retinoblastoma and is segregated as an autosomal dominant trait with high penetrance. In 1971, Knudson proposed his hypothesis of the two hits, where two mutational events are required to initiate tumour progression. We analysed three different point mutations present in patients' retinoblastoma. We produced three cell lines with retinoblastoma protein (RB) mutated in various regions: the missense pN328H, pD718N, and the nonsense early stop codon pR552*. We studied the effect of these point mutations on levels of mRNA and protein expression, proliferation, viability, localisation, and migration using an RBKO cell line. All three affected their localisation patterns and proliferation. However, the pR552* mutation also increases viability and migration. Moreover, when this mutation is simultaneously expressed with a wild-type RB, the phenotype and proliferation parameters are as with the mutant alone, suggesting that maybe only one mutated allele is needed to trigger the characteristic cancer phenotype. In other words, the pR552* mutant behaves more like a gain-of-function or oncogenic mutant. Indeed, a family carrying this mutation showed complete penetrance and high expressivity.

Clinical features of SARS-CoV-2 infection vary, ranging from asymptomatic cases to pneumonia, and other serious complications. Some populations have been observed to be at higher risk for severe disease and death compared to other ethnical groups. To evaluate two parameters of the innate immune system, that play a significant role in viral immunity. In samples of peripheral blood from sixteen patients with severe COVID-19, ten with asymptomatic to mild illness, and fifteen healthy subjects, the percentage of NK and NKT cells, the expression of different NK cell receptors and the blood levels of pro-inflammatory cytokines were tested. We observed that patients with severe COVID-19 showed significantly lower frequencies of both CD56dim and CD56bright NK cells compared to patients with mild illness or healthy controls. Furthermore, patients with severe manifestation of COVID-19 exhibited an aberrant expression of the natural cytotoxicity receptors NKp30, NKp44 and NKp46. Similarly, NK cells from these patients showed statistically significant differences in the expression of various killer immunoglobulin-like receptors (KIRs) in the two main cell subsets (CD56bright, CD56dim) compared to controls or patients with mild disease. Moreover, patients with severe illness displayed decreased frequency of NKT cells (defined as CD3+CD56+) and elevated blood levels of the cytokines IL-6 and IL-8. This study suggests that the abnormal features of NK and NKT cells observed in patients with severe SARS-CoV-2 infection may play an important role in the outcome of this infectious disease in various population groups.