Salivary Antimicrobial Peptide Histatin-5 Does Not Display Zn(II)-Dependent or -Independent Activity against Streptococci.

Histatin-5 (Hst5) is a member of the histatin superfamily of cationic, His-rich, Zn(II)-binding peptides in human saliva. Hst5 displays antimicrobial activity against fungal and bacterial pathogens, often in a Zn(II)-dependent manner. In contrast, here we showed that under in vitro conditions that are characteristic of human saliva, Hst5 does not kill seven streptococcal species that normally colonize the human oral cavity and oropharynx. We further showed that Zn(II) does not influence this outcome. We then hypothesized that Hst5 exerts more subtle effects on streptococci by modulating Zn(II) availability. We initially proposed that Hst5 contributes to nutritional immunity by limiting nutrient Zn(II) availability and promoting bacterial Zn(II) starvation. By examining the interactions between Hst5 and Streptococcus pyogenes as a model Streptococcus species, we showed that Hst5 does not influence the expression of Zn(II) uptake genes. In addition, Hst5 did not suppress growth of a ΔadcAI mutant strain that is impaired in Zn(II) uptake. These observations establish that Hst5 does not promote Zn(II) starvation. Biochemical examination of purified peptides further confirmed that Hst5 binds Zn(II) with high micromolar affinities and does not compete with the AdcAI high-affinity Zn(II) uptake protein for binding nutrient Zn(II). Instead, we showed that Hst5 weakly limits the availability of excess Zn(II) and suppresses Zn(II) toxicity to a ΔczcD mutant strain that is impaired in Zn(II) efflux. Altogether, our findings led us to reconsider the function of Hst5 as a salivary antimicrobial agent and the role of Zn(II) in Hst5 function.

Taquicardia auricular macro-reentrante del tipo flutter auricular en paciente de dos meses infectado con SARS-CoV-2

Introducción: El 11 de marzo de 2020 se confirmaron los primeros casos de la enfermedad en Cuba. Objeto: Examinar una complicación de la infección por SARS-CoV-2 infrecuente en edad pediátrica y su tratamiento. Presentación del caso: Lactante de 2 meses de edad producto de un parto distócico por cesárea a las 41,5 semanas, procedente de la provincia de Guantánamo. Por condiciones maternas permaneció con su madre en el hospital durante 45 días. Egresa y a los 15 días en casa, consultan por fiebre de 38 ℃ durante tres días consecutivos. Se constata frecuencia cardiaca muy elevada y estado eutérmico. El test de antígeno y las pruebas de reacción en cadena de la polimerasa con transcriptasa inversa y PCR para SARS-CoV-2 fueron positivas, por lo que se ingresa en terapia intensiva pediátrica con impresión diagnóstica de taquicardia supraventricular que se define finalmente como flutter auricular. El tratamiento aplicado controló la arritmia cardiaca y contribuyó a su favorable evolución posterior. Conclusiones: Los hallazgos del examen físico y los datos en la anamnesis permiten realizar el diagnóstico del paciente en su etapa temprana. La fisiopatología de las complicaciones en niños está en la regulación local de la expresión de los receptores ACE2, aumento de la producción de catecolaminas y una mayor incidencia de toxicidad por medicamentos que producen lesión cardíaca aguda y arritmia, síntomas que pueden estar asociados con disfunción del sistema respiratorio y cambios hematológicos o no en la edad pediátrica.

Introduction: On March 11, 2020, the first cases of COVID-19 were confirmed in Cuba. Purpose: To examine a complication of SARS-CoV-2 infection uncommon in pediatric ages and its treatment. Case presentation: A 2-month-old infant from Guantánamo province was delivered by cesarean section at 41.5 weeks. Due to maternal conditions, the newborn remained with the mother in the hospital for 45 days. Then the newborn was discharged and after 15 days at home was evaluated due to fever of 38 ° C during three consecutive days. A very high heart rate and euthermic state were observed. The antigen test and reverse transcriptase polymerase chain reaction and PCR tests for SARS-CoV-2 were positive, so the newborn was admitted to the pediatric intensive care unit with diagnostic impression of supraventricular tachycardia that is finally defined as atrial flutter. The treatment applied controlled the cardiac arrhythmia and contributed to its subsequent favorable evolution. Conclusions: The findings of the physical examination and the data in the anamnesis allow the diagnosis of the patient in its early stage. The pathophysiology of complications in children is in the local regulation of ACE2 receptor expression, increased catecholamine production and an increased incidence of toxicity by drugs that produce acute cardiac injury and arrhythmia, symptoms that may be associated with dysfunction of the respiratory system and hematological changes or not in pediatric age.