Increased prevalence of penicillin-resistant viridans group streptococci in Japanese children with upper respiratory infection treated by beta-lactam agents and in those with oncohematologic diseases.

BACKGROUND: Viridans group streptococci, especially penicillin-resistant strains, have been emerging as pathogens of bacteremia in neutropenic patients with hematologic malignancies. OBJECTIVES: To survey the penicillin susceptibilities of viridans group streptococci in Japanese children with and without oncohematologic diseases and to evaluate the effect of the short term administration of beta-lactam agents on the antibiotic susceptibility. METHODS: We tested 113 isolates of viridans group streptococci by the microdilution method for the minimal inhibitory concentrations (MICs) to 10 antibiotics. We isolated 40 isolates from the throats of children with an upper respiratory infection (URI) before beta-lactam antibiotic treatment, 32 isolates after the treatment, 33 isolates in hospitalized children with oncohematologic diseases and 8 isolates from blood. RESULTS: Twenty-five isolates (62.5%) from the children with URI before treatment were penicillin-intermediate or -high level resistant (MIC > or = 0.25 microg/ml). The prevalence of those isolates after antibiotic treatment (87.5%) was significantly increased compared with that before treatment (P = 0.03). The prevalences of the penicillin-high level resistant isolates (MIC > or = 4 microg/ml) in the children with oncohematologic diseases (39.4%) and in the isolates from blood (62.5%) were significantly higher than that in the children with URI before treatment (12.5%) (P < 0.01). Decreased susceptibilities to other beta-lactam agents were observed in the penicillin-high level resistant strains. CONCLUSIONS: The high prevalence of penicillin-intermediate or -high level resistant viridans group streptococci in healthy Japanese children was documented. The administration of beta-lactam agents decreased the prevalence of penicillin-susceptible isolates in the children with URI. High prevalences of penicillin-high level resistant isolates were observed in the oncohematologic patients and in the isolates from blood.

Difference in incidence and transmission mode of methicillin-resistant Staphylococcus aureus among surgery, orthopedics, and pediatrics wards: a prospective study at a university hospital.

The incidence and circumstances of colonization by methicillin-resistant Staphylococcus aureus were prospectively investigated. Among 404 patients, 15 (3.7%) were carriers on admission, and 43 (10.6%) became colonized, mainly after surgical operation. A different mode of transmission was suggested in each ward.

B cell epitope mapping of the bacterial superantigen staphylococcal enterotoxin B: the dominant epitope region recognized by intravenous IgG.

We showed that i.v. IgG contains Abs against a major group of bacterial superantigens, and that they can inhibit superantigen-elicited T cell activation. The B cell epitope region of the superantigen and the inhibitory mechanism have remained unknown. To analyze the dominant B cell epitopes on the bacterial superantigen SEB (staphylococcal enterotoxin B), we constructed fusion proteins of SEB deletion mutants, and the reactivities of these recombinant proteins to i.v. IgG and healthy human sera were evaluated by means of immunoblotting. Intravenous IgG and healthy human sera mostly recognized the C-terminal fragment (amino acid (aa) 133-239). The C-terminally truncated protein (aa 1-228) and the truncated mutant delta 225-234 lost reactivity, while the truncated protein (aa 1-234) did not, suggesting that the region (aa 225-234) is the dominant B cell epitope. The mutant, in which residues 226-229 of SEB were exchanged for residues 209-212 of streptococcal pyrogenic exotoxin A, reduced the reactivity with the C-terminal region-specific IgG purified by affinity chromatography. The C-terminal region-specific IgG inhibited SEB-elicited T cell activation, suggesting that this Ab that recognizes the epitope functions as the humoral defensive factor against SEB in humans. Furthermore, the assumed epitope region was homology to the residues (aa 32-41) of human thymopoietin, containing the biologic active site.

Risk factors for persistence of pulmonary arterial branch stenosis in neonates and young infants.

BACKGROUND: Pulmonary arterial branch stenosis (PBS) in neonates is considered to be transient. However, PBS has been found not only in neonates, but also in young infants. Among these patients, we encountered several patients whose PBS was still present after the age of 1 year. METHODS: To clarify the natural history of PBS in neonates and young infants, we retrospectively reviewed the records of 103 patients diagnosed with PBS in the neonatal period and early infancy. RESULTS: The PBS findings were improved in all patients. Pulmonary arterial branch stenosis disappeared in 94 patients by the age of 1 year (group A), but persisted after I year of age in nine patients (group B). Group B patients had a significantly lower mean birth weight and greater deltavelocity (the difference in the peak flow velocity between the main pulmonary artery and stenotic branch) at diagnosis than group A patients. Incidences of low birth weight (< 2,500 g) and deltavelocity above 1.2 m/s were significantly higher in group B than group A patients. There was no significant difference in the frequency of premature infants (gestational age < 36 weeks) between the groups, suggesting that intrauterine growth retardation may be related to developmental abnormalities of the pulmonary arterial branch. CONCLUSIONS: All cases of PBS in neonates and young infants were improved. However, PBS persisted in some patients after the age of 1 year. Low birth weight and deltavelocity above 1.2 m/s are risk factors for persistent PBS. Pulmonary arterial branch stenosis was not present after the age of 1 year in 62 of 63 patients without either of these risk factors.