Pathogenic bacteria worsen RSV severity, lengthen ICU stays in infants

WASHINGTON – Potentially pathogenic nasopharyngeal bacterial colonization was associated with more severe respiratory syncytial virus–related bronchiolitis in infants, according to a study.

"We found that [colonization] was significantly more common and almost double in the RSV patients, compared with controls," said Dr. Eleanora Bunsow, a researcher at Nationwide Children’s Hospital in Columbus, Ohio, who presented the data at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. "And RSV patients were frequently colonized with more than one pathogenic bacteria."

Additionally, the use of polymerase chain reaction (PCR) assays to assess bacterial colonization types and levels was found to outperform the accuracy of cultures.

"The PCR showed an increased capacity for bacteria detection and had the ability to quantitate the bacterial load in infant RSV bronchiolitis," Dr. Bunsow said.

While the majority of infants hospitalized with RSV bronchiolitis are previously healthy with no known risk factors, about 15% will require intensive care. The role of pathogenic bacteria has, until recently, been explored only in animal studies, Dr. Bunsow said.

From December 2010 to May 2012, 294 children (median age, 2.5 years) were enrolled at a single site. Of these, 47 were age-matched healthy controls, 182 were inpatient, and 65 were admitted to the ICU. Both inpatient and ICU admissions tended to include twice as many boys as girls (1.6:1 and 1.7:1, respectively). A total of 47% of the control group were African Americans.

Cultures and PCR assays were performed on all study participants for the detection of gram-positive Staphylococcus aureus and Streptococcus pneumoniae, and gram-negative Moraxella catarrhalis and Haemophilus influenzae.

PCR had a 1.4-fold higher level of sensitivity (95% confidence interval, 91%-98%) and equal specificity when compared with cultures for identifying all four bacteria tested.

Polymicrobial bacterial colonization of both gram-positive and gram-negative species was found in 13% of RSV patients, compared with no potentially pathogenic bacterial colonizations in the control group (P = .004).

Rates of colonization were also higher in those with severe RSV infections of the lower respiratory tract who were admitted to the pediatric ICU (PICU), compared with inpatients with less severe disease (53.8% vs. 39%; P = .038). The median clinical disease severity score for those with potentially pathogenic bacterial colonization was 5, compared with a median score of 4 in those without colonization (P = .187).

Colonization with gram-negative bacteria was associated with a "significantly higher" need for up to 3 days of ICU oxygen support, compared with needing only up to 2 days of oxygen for colonization with gram-positive bacteria (P = .039), Dr. Bunsow noted.

Also, H. influenzae was identified in 54% of PICU patients, compared with 39% of inpatient ones. Higher H. influenzae loads correlated with PICU lengths of stay (P = .03).

"Our future study will include outpatients ... and will analyze the impact of the microbiome in these patients," Dr. Bunsow said.

Dr. Bunsow said she had no relevant disclosures.

[email protected]

On Twitter @whitneymcknight

WASHINGTON – Potentially pathogenic nasopharyngeal bacterial colonization was associated with more severe respiratory syncytial virus–related bronchiolitis in infants, according to a study.

"We found that [colonization] was significantly more common and almost double in the RSV patients, compared with controls," said Dr. Eleanora Bunsow, a researcher at Nationwide Children’s Hospital in Columbus, Ohio, who presented the data at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. "And RSV patients were frequently colonized with more than one pathogenic bacteria."

Additionally, the use of polymerase chain reaction (PCR) assays to assess bacterial colonization types and levels was found to outperform the accuracy of cultures.

"The PCR showed an increased capacity for bacteria detection and had the ability to quantitate the bacterial load in infant RSV bronchiolitis," Dr. Bunsow said.

While the majority of infants hospitalized with RSV bronchiolitis are previously healthy with no known risk factors, about 15% will require intensive care. The role of pathogenic bacteria has, until recently, been explored only in animal studies, Dr. Bunsow said.

From December 2010 to May 2012, 294 children (median age, 2.5 years) were enrolled at a single site. Of these, 47 were age-matched healthy controls, 182 were inpatient, and 65 were admitted to the ICU. Both inpatient and ICU admissions tended to include twice as many boys as girls (1.6:1 and 1.7:1, respectively). A total of 47% of the control group were African Americans.

Cultures and PCR assays were performed on all study participants for the detection of gram-positive Staphylococcus aureus and Streptococcus pneumoniae, and gram-negative Moraxella catarrhalis and Haemophilus influenzae.

PCR had a 1.4-fold higher level of sensitivity (95% confidence interval, 91%-98%) and equal specificity when compared with cultures for identifying all four bacteria tested.

Polymicrobial bacterial colonization of both gram-positive and gram-negative species was found in 13% of RSV patients, compared with no potentially pathogenic bacterial colonizations in the control group (P = .004).

Rates of colonization were also higher in those with severe RSV infections of the lower respiratory tract who were admitted to the pediatric ICU (PICU), compared with inpatients with less severe disease (53.8% vs. 39%; P = .038). The median clinical disease severity score for those with potentially pathogenic bacterial colonization was 5, compared with a median score of 4 in those without colonization (P = .187).

Colonization with gram-negative bacteria was associated with a "significantly higher" need for up to 3 days of ICU oxygen support, compared with needing only up to 2 days of oxygen for colonization with gram-positive bacteria (P = .039), Dr. Bunsow noted.

Also, H. influenzae was identified in 54% of PICU patients, compared with 39% of inpatient ones. Higher H. influenzae loads correlated with PICU lengths of stay (P = .03).

"Our future study will include outpatients ... and will analyze the impact of the microbiome in these patients," Dr. Bunsow said.

Dr. Bunsow said she had no relevant disclosures.

[email protected]

On Twitter @whitneymcknight

WASHINGTON – Potentially pathogenic nasopharyngeal bacterial colonization was associated with more severe respiratory syncytial virus–related bronchiolitis in infants, according to a study.

"We found that [colonization] was significantly more common and almost double in the RSV patients, compared with controls," said Dr. Eleanora Bunsow, a researcher at Nationwide Children’s Hospital in Columbus, Ohio, who presented the data at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. "And RSV patients were frequently colonized with more than one pathogenic bacteria."

Additionally, the use of polymerase chain reaction (PCR) assays to assess bacterial colonization types and levels was found to outperform the accuracy of cultures.

"The PCR showed an increased capacity for bacteria detection and had the ability to quantitate the bacterial load in infant RSV bronchiolitis," Dr. Bunsow said.

While the majority of infants hospitalized with RSV bronchiolitis are previously healthy with no known risk factors, about 15% will require intensive care. The role of pathogenic bacteria has, until recently, been explored only in animal studies, Dr. Bunsow said.

From December 2010 to May 2012, 294 children (median age, 2.5 years) were enrolled at a single site. Of these, 47 were age-matched healthy controls, 182 were inpatient, and 65 were admitted to the ICU. Both inpatient and ICU admissions tended to include twice as many boys as girls (1.6:1 and 1.7:1, respectively). A total of 47% of the control group were African Americans.

Cultures and PCR assays were performed on all study participants for the detection of gram-positive Staphylococcus aureus and Streptococcus pneumoniae, and gram-negative Moraxella catarrhalis and Haemophilus influenzae.

PCR had a 1.4-fold higher level of sensitivity (95% confidence interval, 91%-98%) and equal specificity when compared with cultures for identifying all four bacteria tested.

Polymicrobial bacterial colonization of both gram-positive and gram-negative species was found in 13% of RSV patients, compared with no potentially pathogenic bacterial colonizations in the control group (P = .004).

Rates of colonization were also higher in those with severe RSV infections of the lower respiratory tract who were admitted to the pediatric ICU (PICU), compared with inpatients with less severe disease (53.8% vs. 39%; P = .038). The median clinical disease severity score for those with potentially pathogenic bacterial colonization was 5, compared with a median score of 4 in those without colonization (P = .187).

Colonization with gram-negative bacteria was associated with a "significantly higher" need for up to 3 days of ICU oxygen support, compared with needing only up to 2 days of oxygen for colonization with gram-positive bacteria (P = .039), Dr. Bunsow noted.

Also, H. influenzae was identified in 54% of PICU patients, compared with 39% of inpatient ones. Higher H. influenzae loads correlated with PICU lengths of stay (P = .03).

"Our future study will include outpatients ... and will analyze the impact of the microbiome in these patients," Dr. Bunsow said.

Dr. Bunsow said she had no relevant disclosures.

[email protected]

On Twitter @whitneymcknight