Effect of therapeutic concentrations of nitric oxide on bacterial growth in vitro.
OBJECTIVE
Besides its vasodilative actions, nitric oxide (NO) is also involved in host defense on a cellular level. We studied the antimicrobial properties of NO in concentrations used with inhaled NO therapy for the treatment of pulmonary hypertension in neonates.


METHODS
In vitro study of bacterial growth of five species, with and without NO exposure.


METHODS
Level IV neonatal intensive care unit at a university children's hospital.


METHODS
In vitro bacterial cultures.


METHODS
We tested ten different strains of five bacterial species (Staphylococcus aureus, Staphylococcus epidermidis, group B streptococcus [GBS/Streptococcus agalactiae], Escherichia coli, and Pseudomonas aeruginosa), derived from the tracheal isolates of ventilated premature and term infants. Cultures were exposed to three different concentrations of NO (40, 80, and 120 parts per million [ppm]) and bacterial growth was compared with the same strains incubated in ambient air for 24 hrs. After incubation (with or without NO), colony-forming units were counted.


RESULTS
Bacterial growth of S. aureus, E. coli, and P. aeruginosa was not reduced with the NO concentrations applied. The number of colony-forming units of S. aureus increased at 80 ppm of NO. Growth of S. epidermidis and GBS was significantly affected at 120 ppm, resulting in decreased numbers of colony-forming units as compared with controls exposed to ambient air.


CONCLUSIONS
We conclude that NO has a selective bacteriostatic effect on some of those bacteria most commonly cultured in tracheal specimens of premature infants and neonates. This effect appears to be dose-dependent and occurs in the upper range of dosages used with inhaled NO therapy. However, in the range of dosages applied in ongoing controlled trials of inhaled NO in neonates and premature infants (1 to 80 ppm), a bacteriostatic effect of NO is not to be expected.
Hoehn
T
T
Neonatal Intensive Care Unit, University Children's Hospital, Freiburg, Germany. thomas.hoehn@charite.de
Huebner
J
J
Paboura
E
E
Krause
M
M
Leititis
J U
JU
D000280:Administration, Inhalation; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007231:Infant, Newborn; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000706:statistics & numerical data; D009569:Nitric Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D018709:Statistics, Nonparametric
D000900:Anti-Bacterial Agents; D009569:Nitric Oxide