A collection of 2,209 isolates of six polysaccharide capsule types of Haemophi/us influenzoe, including 1,975 serotype b isolates recovered in 30 countries was characterized for electrophoretically demonstrable allele profiles at 17 metabolic enzyme loci. Two hundred eighty distinct multilocus genotypes were distinguished, and cluster analysis revealed two primary phylogenetic divisions. The population structure of encapsulated H. influenzae is clonal. Currently, most of the invasive disease worldwide is caused by serotype b strains of nine clones, Strains producing serotype c, e, and f capsules belong to single divisions and have no close genetic relationships to strains of other serotypes, Serotype a and b strains occur in both primary phylogenetic divisions, probably as a result of transfer and recombination of serotype-specific sequences of the cap region between clonal lineages. A close genetic relatedness between serotype d isolates and some strains of serotypes a and b was identified, There are strong patterns of geographic variation, on an intercontinental scale, in both the extent of genetic diversity and the clonal composition of populations of encapsulated strains, The analysis suggests that the present distribution of clones is, in part, related to patterns of racial or ethnic differentiation and historical demographic movements of the human host populations.

We describe the cases of 2 infants with congenital babesiosis born to mothers with prepartum Lyme disease and subclinical Babesia microti infection. The infants both developed anemia, neutropenia, and thrombocytopenia, and 1 infant required red blood cell transfusion. Both infants recovered with treatment. Additional studies are warranted to define the optimal management strategy for pregnant women with early Lyme disease in geographic areas in which B microti infection is endemic.

The need for routine sepsis evaluation in patients who have experienced an apparent life-threatening event but lack signs of infection remains controversial. To assess their risk of a serious occult bacterial infection, records were reviewed of 95 infants in whom infections were discovered during their inpatient evaluation after an apparent life-threatening event. Noted for each patient was the presence of any suggestive findings that would have prompted a physician to consider the given type of infection in the differential diagnosis. Thirty patients had bacterial infections; all but 5 had suggestive findings. The exceptions included 1 patient with pneumonia and 4 with urinary tract infections. None of the remaining 25 patients had occult bacterial infections. In patients with an apparent life-threatening event who appear well and lack signs suggestive of a serious bacterial infection, it may be possible to forego routine sepsis evaluation beyond a chest radiograph and urine culture without risking a serious missed diagnosis.

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