Increased salivary elastase precedes gram-negative bacillary colonization in postoperative patients

Severe SARS-CoV-2 Infection in a Pediatric Patient Requiring Extracorporeal Membrane Oxygenation

The overwhelming majority of pediatric cases of SARS-CoV-2 infection are mild or asymptomatic with only a handful of pediatric deaths reported. We present a case of severe COVID-19 infection in a pediatric patient with signs of hyperinflammation and consumptive coagulopathy requiring intubation and extracorporeal membrane oxygenation (ECMO) and eventual death due to ECMO complications.

Oropharyngeal colonization: epidemiology, treatment and ventilator-associated pneumonia prevention

Oropharyngeal (OP) colonization and ventilator-associated pneumonia (VAP) mechanisms are tightly linked. A significant within-population variation in OP colonization has been described, with its composition being dependent from patients' severity. For instance, healthy subjects have a very low rate in Gram-negative bacteria (GNB) colonization, while its rate rises in comorbid patients, reaching high proportions in ICU patients. Various factors can be put forward to explain the modifications of hospital acquired OP. ICU patients might suffer from underlying diseases; the gastric reflux induced by the presence of nasogastric tubes and the patients' position influences OP colonization; salivary composition might influence OP content, as it modulates bacterial adhesion and induces reversible bacterial changes enhancing bacterial binding. The transition from OP colonization to VAP has been shown in numerous studies, with the digestive tract acting as a filter, or as a reservoir. Some therapies have been investigated to modulate OP colonization, in order to reduce the risk for VAP. Among those, mammalian antimicrobial peptides have been shown effective in reducing GNB colonization in healthy subjects, but failed in preventing VAP in ICU patients. The widely used chlorhexidine was tested in numerous trials. Data on its efficacy are conflicting, and meta-analyses yield discordant results. Above all, several drawbacks have aroused: a poor tolerance of concentrated solutions; an increased risk of death in the less severe patients; and a reduced susceptibility towards chlorhexidine of number of VAP pathogens. Proanthocyanidins, used to prevent Escherichia coli adhesion to the urothelium, have been tested in mice model of pneumonia with interesting results. Some complementary data are needed before moving to clinical research. Future research paths should include a reappraisal of OP colonization; finding better formulations for chlorhexidine; define the best populations to target oral decontamination and developing other strategies to prevent and treat OP colonization.

Microbiology of Tracheal Secretions: What to Expect with Children and Adolescents with Tracheostomies

Introduction  People with tracheostomies exhibit a higher risk of colonization of the lower respiratory tract, acute tracheitis and pneumonia. Despite this, the culture of tracheal secretions is not a routine in most hospitals, and sometimes empiric therapy is based on personal experience, which is not an ideal situation.

Objective  To recognize the pathogens present in the tracheal secretions collected from people up to 18 years old with tracheostomies.

Methods  Prospective evaluation of patients under the age of 18 of a tertiary care hospital. A standardized questionnaire was completed, and tracheal secretion aspirates were sent for microbiological cultures and antibiograms.

Results  Twenty patients under 18 years of age were evaluated, 65% of whom were male. The microbiological culture was positive in 90% of the patients, and the most common microorganisms found were Pseudomonas aeruginosa (55.5%) and Staphylococcus aureus (27.7%).

Discussion  Tracheostomized children and adolescents have respiratory tracts colonized by pathogens, the most common of which is Pseudomonas aeruginosa . These patients must undergo tracheal secretion cultures, whether they present symptoms or not, to determine if there is a correlation between the colonization and the infections. This finding could guide the adequate treatment, avoiding the inappropriate use of antibiotics and indicating the better therapy in cases of laryngeal reconstruction.

Conclusion  In this sample, the culture of tracheal secretions was mainly positive, and the most common agent was P. aeruginosa . We suggest the routine access to Brazilian children and adolescents tracheal secretion cultures, which could help to make a profile of these children and guide the use of antibiotics.

Oropharyngeal carriage and lower airway colonisation/infection in 45 tracheotomised children

BACKGROUND

A study was undertaken to determine the oropharyngeal carrier state of potentially pathogenic microorganisms (PPM) and the magnitude of colonisation and infection rates of the lower airways with these PPM in children requiring long term ventilation first transtracheally and afterwards via a tracheotomy.

METHODS

A 5 year, prospective, observational cohort study was undertaken in 45 children (33 boys) of median age 6.4 months (range 0-180) over a 5 year period at the Royal Liverpool Children's NHS Trust of Alder Hey, a university affiliated tertiary referral centre. The children were first admitted to the 20-bed paediatric intensive care unit (PICU) and, following placement of a tracheotomy, they were transferred to a four bedded respiratory ward. The two main indications were neurological disorders and airway obstruction. All children were ventilated transtracheally for a median period of 12 days (range 0-103) and, after placement of the tracheotomy, for a similar period of 12 days (range 1-281). Surveillance cultures of the oropharynx were taken on admission to the PICU and on the day of placement of the tracheotomy. Throat swabs were taken twice weekly during ventilation, both transtracheal and via the tracheotomy. Tracheal aspirates were taken once weekly and when clinically indicated (in cases where the lower airway secretions were turbid).

RESULTS

Twenty five patients (55%) had abnormal flora, mainly aerobic Gram negative bacilli (AGNB), particularly Pseudomonas aeruginosa, while the community PPM Staphylococcus aureus was present in the oropharynx of 37% (17/45) of the study population. The lower airways were sterile in six children; the other 39 patients (87%) had a total of 82 episodes of colonisation. "Community" PPM significantly increased once the patients received a tracheotomy, independent of the number of patients enrolled, episodes of colonisation/infection, and the number of colonised/infected patients. "Hospital" PPM significantly decreased after tracheotomy only when episodes were compared.

CONCLUSIONS

While P aeruginosa present in the admission flora caused primary endogenous colonisation/infection during mechanical ventilation on the PICU, S aureus not carried in the throat was responsible for the exogenous colonisation/infection once the patients had a tracheotomy. This is in sharp contrast to adult studies where exogenous infections are invariably caused by AGNB. This discrepancy may be explained by chronic underlying conditions such as diabetes, alcoholism, and chronic obstructive pulmonary disease which promote AGNB, whereas the children were recovering following tracheotomy.

Clinical impact of abnormal gut flora in infants receiving parenteral nutrition

OBJECTIVE

Illness is associated with the carriage of abnormal flora (aerobic Gram-bacilli except E. coli) in the oropharynx and rectum. The aim of this study was to investigate whether carriage of abnormal flora is associated with increased risk of sepsis and septicemia in surgical newborn infants.

METHODS

A 2-year prospective study was carried out on 94 consecutive newborn infants requiring parenteral nutrition (PN) for gastrointestinal abnormalities. Throat and rectal swabs were taken on day 1 of PN and twice weekly. Patients were divided into two groups: abnormal flora (AF; n = 41) and normal flora (NF; n = 53). Sepsis was defined as clinical features of generalized inflammation requiring blood culture. Septicemia was the combination of sepsis and positive blood culture.

RESULTS

Among the infants carrying abnormal flora Pseudomonas and Enterobacter spp. predominated. Duration of PN (AF median 30 days; NF median 9 days), incidence of sepsis (AF 29%; NF 6%), and septicemia (AF 22%; NF 2%) were significantly greater in the group of infants with abnormal flora. Surveillance cultures allow the detection of a subset of infants on PN at high risk of sepsis and septicemia. The degree of gut dysfunction related to the severity of underlying disease determines the duration of PN and the development of abnormal flora. The association between abnormal carriage and increased risk of sepsis and septicemia may be because of the intestinal endotoxin pool known to cause liver impairment and consequent suppression of systemic immunity.

The pathogenesis of ventilator-associated pneumonia: I. Mechanisms of bacterial transcolonization and airway inoculation

Ventilator-associated pneumonia (VAP) is an infection of the lung parenchyma developing in patients on mechanical ventilation for more than 48 h. VAP is associated with a remarkably constant spectrum of pathogenic bacteria, most of which are aerobic Gram-negative bacilli (AGNB) and, to a lesser extent Staphyloccus aureus. Most authorities agree that VAP develops as a result of aspiration of secretions contaminated with pathogenic organisms, which appear to be endogenously acquired. These pathogens gain access to the distal airways by mechanical reflux and aspiration of contaminated gastric contents and also by repetitive inoculation of contaminated upper airway secretions into the distal tracheobronchial tree. Persistence of these organisms in the upper airways involves their successful colonization of available surfaces. Although exogenous acquisition can occur from the environment, the rapidity at which critically ill patients acquire AGNB in the upper airways in conjunction with the low rate of AGNB colonization of health-care workers exposed to the same environment favors the presence of endogenous proximate sources of AGNB and altered upper airway surfaces that are rendered receptive. Proximate sources of AGNB remain unclear, but potential sites harboring AGNB prior to illness include the upper gastrointestinal tract, subgingival dental plaque, and the periodontal spaces. Following illness or antibiotic therapy, competitive pressures within the oropharynx favor AGNB adherence to epithelial cells, which lead to oropharyngeal colonization. Similar dynamic changes in contiguous structures (oropharynx, trachea, sinuses, and the upper gastrointestinal tract) lead to the transcolonization of these structures with pathogenic bacteria. Following local colonization or infection, these structures serve as reservoirs of AGNB capable of inoculating the lower airways. As the oropharynx becomes colonized with AGNB, contaminated oropharyngeal secretions reach the trachea, endotracheal tube, and ventilator circuit. Contaminated secretions pooled above the endotracheal tube cuff gain access to the trachea and inner lumen of the endotracheal tube by traversing endotracheal tube cuff folds. Amorphic particulate deposits containing AGNB form along the endotracheal tube and are capable of being propelled into the distal airways by ventilator-generated airflow or by tubing manipulation. Bacteria embedded within this type of amorphous matrix are particularly difficult for the host to clear. If host defenses fail to clear the inoculum, then bacterial proliferation occurs, and the host inflammatory response progresses to bronchopneumonia.(ABSTRACT TRUNCATED AT 400 WORDS)

Relationship between cytomegalovirus and colonization of the oropharynx by gram-negative bacilli following renal transplantation

Numerous investigators have reported an increased incidence of pneumonia caused by Gram-negative bacilli and other secondary pathogens in transplant recipients infected by cytomegalovirus (CMV). To determine if CMV infections are related to colonization of the upper respiratory tract by Gram-negative bacilli, we examined prospectively 22 renal transplant recipients with sequential bacteriological, virological and biochemical examinations performed just prior to and at various times after transplantation. Only 11% of subjects had Gram-negative bacilli isolated from gargle specimens prior to transplantation, as compared to 54% after transplantation. More importantly, after transplantation, subjects with active CMV infections were more likely to have prolonged oropharyngeal carriage of Gram-negative bacilli than subjects without CMV infections (36% v. 25%). During active CMV infections, the rate at which Gram-negative bacilli were isolated from gargle specimens rose from 28 to 47%. During culture-positive CMV infections, the isolation rate reached 57% and was significantly different from that of CMV-negative samples (P less than 0.01). The increased rate of Gram-negative bacillary isolation from gargle specimens during CMV infections was not a function of type of immunosuppressive agents used, rejection episodes, antibiotic administration, concomitant hepatitis B, Epstein-Barr (EBV) virus, or herpes simplex virus infections, or alterations in salivary fibronectin concentrations.