Nancy A. Melville

May 29, 2012

May 29, 2012 (Thessaloniki, Greece) — Infants with respiratory syncytial virus (RSV) bronchiolitis who have nasopharyngeal colonization of pathogenic bacteria show increased rates of disease severity, according to research presented here at the European Society for Paediatric Infectious Diseases (ESPID) 30th Annual Meeting.

Researchers seeking to determine the impact of bacterial colonization on clinical and biological parameters of pulmonary function for infants evaluated 136 previously healthy children who were hospitalized with RSV bronchiolitis from December 2010 to September 2011, of whom 62% were male. Twenty-three matched control participants were also enrolled.

Nasopharyngeal swabs were cultured for the following: Staphylococcus aureus, Stroptococcus pneumoniae, Mycoplasma catarrhalis, Hemophilus influenzae, and β-hemolytic Streptococcus. Demographic and disease severity parameters were compared among patients testing positive for pathogenic bacteria.

The results showed that the nasopharyngeal cultures were negative for 43% of the children (59/136) with RSV bronchiolitis and for 76% of those who had received antibiotics.

Of the patients not treated with antibiotics, 51% (69/136) were colonized more frequently with gram-negative bacteria (GNB, 43%; 15/35) compared with healthy control participants, who were mostly colonized with gram-positive bacteria (GPB, 93%; 13/14, P = .01).

RSV patients who were colonized with pathogenic bacteria showed significantly higher white blood cell counts in nasopharyngeal samples (P = .03), higher percentages of blood neutrophil (P = .02), and lower basal oxygen saturation levels (P < .05) than those not colonized with the pathogenic bacteria.

Colonization with GNB, but not GPB, was associated with a longer need for supplemental oxygen (P = .04).

"We found that 85% of patients were colonized with one or more than one bacteria," said lead author María del Carmen Suárez-Arrabal, MD, of the Center for Vaccines and Immunity, which is part of the Research Institute at Nationwide Children's Hospital in Columbus, Ohio.

"As many as 80% of RSV patients were colonized with one or more than one pathogenic bacteria, compared with 65% of healthy infants, and the patients colonized with pathogenic bacteria had higher percentage of low neutrophils compared to those with gram-positive flora," she explained.

Other factors indicative of worse disease, including hospitalization, were observed in association with the increased bacterial levels.

"Patients colonized with gram-negative bacteria needed hospitalization for longer periods of time compared with other groups, specifically, compared with those colonized with gram-positive bacteria," Dr. Arrabal added.

"In nasal washes, we saw that white blood cell counts were higher in those colonized with one or more pathogenic bacteria, compared with those colonized with RSV."

In ongoing research, Dr. Arrabal and her colleagues are currently working to measure and compare viral loads between patients with GNB and healthy control participants.

None of the speakers have disclosed any relevant financial relationships.

European Society of Paediatric Infectious Diseases (ESPID) 30th Annual Meeting. Abstract 524. Presented May 11, 2012.

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