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Biomedical subjects

H C Dillon

Publications and source records attributed to H C Dillon.

At least 19 recordsLinked to original sources
PubMed1991

Group B streptococcal C protein-associated antigens: association with neonatal sepsis.

The c protein (Ibc) of group B streptococci (GBS) is associated with at least four antigens (alpha, beta, gamma, delta). To assess the virulence potential of these antigens, 255 GBS isolates recovered from septic neonates, healthy neonates, and pregnant women were serotyped and surveyed for reactivity with sera to c protein and the four associated antigens. A radioimmunoassay using intact bacteria was used to detect the GBS antigens. In contrast to earlier reports, most (66%) of the type III strains expressed the c protein. Except for the gamma antigen, none of the other c protein-associated antigens showed an increased association with pathogenic strains independent of the polysaccharide antigens. The gamma antigen was expressed by 15 of 41 c protein-positive early-onset strains and by 4 of 38 c protein-positive late-onset strains (P = .007). This association was independent of the type-specific antigen, suggesting a potential role for the gamma antigen as a virulence factor in GBS strains causing early-onset sepsis.

Antigens, Bacterial↗
PubMed1990

Risk factors for perinatal group B streptococcal disease after amniotic fluid colonization.

A group of 1031 parturient women at high risk for intraamniotic infection were studied. Women in whom group B streptococci grew from cultures of the amniotic fluid did not differ in clinical risk factors when compared with similar parturient women without group B streptococcal colonization of amniotic fluid. Patients who had perinatal group B streptococcal disease (maternal or neonatal bacteremia) did not differ from those without disease, by maternal or neonatal acute antibody levels or antibody response, inoculum size, or serotype of the colonizing strain.

Amniotic Fluid↗
PubMed1988

Seroepidemiology of group B Streptococcus type II antibody specificity.

The specificity of human antibodies for the two major sidechain determinants of the type II group B streptococcal (GBS) polysaccharide was examined in 90 pairs of maternal and cord sera. Using an ELISA system, total antibody was measured against the complete (sialylated) type II antigen and the proportion of antibody against the galactose determinant was estimated by inhibition with free beta-methylgalactopyranoside. Mothers colonized by type II or by other GBS types had higher levels of total specific antibody (means, 3.3 and 4.7 micrograms/ml, respectively) than those not colonized (mean, 2.2 micrograms/ml). Cord sera averaged 1-2 micrograms/ml lower than maternal sera. Colonization with GBS was also associated with higher levels against the galactose determinant (mean, 1.5 micrograms/ml, compared to 0.7 micrograms/ml for those not colonized). The distribution of specificities favoured antibodies against the sialic acid determinant in maternal but not cord sera. Specificity as well as antibody level may play a role in the epidemiology of GBS type II.

Antibodies, Bacterial↗
PubMed1988

Epidemiological studies of Streptococcus pneumoniae in infants: antibody to types 3, 6, 14, and 23 in the first two years of life.

Antibodies to pneumococcal types 3, 6, 14, and 23 were measured in sera from 78 infants prospectively studied from birth. Mean levels of antibodies to capsular antigens were 2-4 micrograms/mL, with no overall differences between carriers and noncarriers of given types. Serial serum samples were studied in selected infants to more precisely define the antibody response in relation to specific pneumococcal colonization and infection. Although some infants had little antibody, and made little in response to exposure, others had demonstrable antibody at the onset of acute otitis media. The highest levels were seen following repeated exposure. After an initial or secondary response, levels declined with or without continued nasopharyngeal carriage.

Acute Disease↗
PubMed1988

Role of adherence of Streptococcus pneumoniae in acute otitis media.

The adherence of Streptococcus pneumoniae to human nasopharyngeal epithelial cells was studied as a possible determinant in the development of acute otitis media (AOM). Pneumococcal isolates were obtained from the nasopharynx (NP) and middle ear fluid of infants followed from birth in a prospective study of pneumococcal carriage and infection. The adherence of 33 middle ear fluid isolates from 19 infants with AOM was compared with 143 strains recovered from NP cultures taken from each child both at the time of their acute infections and on other occasions. We studied 171 NP isolates from 29 "carrier" infants, who had no pneumococcal infections, for comparison. Adherence properties were not associated with any particular pneumococcal capsular types, nor were adherent strains more frequent among infants with AOM. There was no evidence to support the hypothesis that pneumococci associated with AOM have a special propensity for adherence. Adherence was a frequent characteristic of pneumococci recovered from the NP, especially in connection with upper respiratory tract infection, and may be required for the establishment of colonization but was not a property that discriminated between carriage strains and those causing AOM.

Bacterial Adhesion↗
PubMed1987

Type-specific streptococcal antibodies in amniotic fluid.

Type-specific antibodies against group B streptococcal and pneumococcal capsular antigens were measured in 68 amniotic fluid samples from healthy women between 16 and 20 weeks of pregnancy. Mean antibody levels ranged from 0.13 to 0.61 microgram/ml, with few samples having greater than 1 microgram/ml against any antigen. The role of antibodies in protection against intrauterine infection is discussed.

Adult↗
PubMed1987

Group B streptococcal carriage and disease: a 6-year prospective study.

A prospective study of group B streptococcal (GBS) carriage and disease was conducted over 6 years. Carriage rates at delivery for mothers and infants were 20% and 12%, respectively. Forty-five cases of GBS disease occurred in infants, 24 "early-onset" disease and 21 "late-onset" disease. The combined attack rate for early and late disease was 3.3 per 1000 live births over the 6 years. The rate of early-onset disease was highest in infants found to be heavily colonized at birth: 50 per 1000 live births. Twenty-three of 24 had evidence of intrauterine-acquired infection. All GBS serotypes were represented. Preterm delivery, prolonged labor, premature rupture of membranes, and maternal infection enhanced the risk of early disease. Septicemia was the predominant form of late-onset disease (15 of 21 cases); GBS type III accounted for 19 of 21 cases. Ten of 21 infants with late infections were colonized at birth with the GBS type that subsequently caused disease. Thus a maternal source of infection was identified in 34 of the 45 infants. These data reveal consistent year-to-year carriage and disease rates in the study population.

Anti-Bacterial Agents↗
PubMed1987

Lack of correlation of in vitro adherence of Haemophilus influenzae to epithelial cells with frequent occurrence of otitis media.

The adherence to human epithelial cells, biotype and capsular type of 175 Haemophilus influenzae cultured from the upper respiratory tract were studied in a prospective study of children with recurrent otitis media. Forty-three children who had greater than 2 episodes of acute otitis media (AOM) during the first year of life were followed for at least 1 year. Cultures of the oropharynx were done periodically, and the middle ear fluid (MEF) was cultured at the time of AOM. H. influenzae was recovered from MEF in 44% of the 136 AOM episodes recorded. Thirty-one children had at least one episode of AOM caused by H. influenzae; the remaining 12 children, designated as "controls," had no otitis or had AOM caused by other organisms. The possible differences between carriage and infection strains were evaluated by comparison of MEF and oropharyngeal isolates, by pairwise comparison of MEF and oropharyngeal isolates and by pairwise comparison of multiple isolates from each host recovered at the time of AOM and during infection-free intervals. No significant differences in patterns of adherence, capsular type or biotype were found. The lack of correlation between these characteristics and infection suggests either that H. influenzae organisms have determinants of virulence yet to be defined or that variations in host susceptibility permit infection by the strain colonizing the upper respiratory tract. Adherence per se may be less important in the development of infection than in establishing and maintaining colonization within the host.

Acute Disease↗
PubMed1987

Streptococcal pharyngitis in the 1980s.

Streptococcal pharyngitis remains a common problem in children and adolescents. However, the incidence of acute rheumatic fever is now quite low except in developing countries. Proper management of streptococcal pharyngitis has contributed significantly to the decline in ARF. Penicillin treatment has clearly altered the natural history of streptococcal infection; the acute illness is shortened, risk of spread of infection is reduced, suppurative complications are prevented and ARF is prevented. Some cases of acute glomerulonephritis may be prevented. The decline in rheumatic fever has probably contributed to a greater interest in clinical benefits of therapy. Antigen detection tests appear promising for providing a more rapid bacteriologic diagnosis of streptococcal infection, which in turn permits prompt treatment. While penicillin has been the treatment of choice for four decades, a disturbing trend of increasing numbers of clinical relapses or recurrent infections has been noted in recent years. Alternative antibiotics, such as the oral cephalosporins, may now be superior to oral penicillin in terms of lessening the risk of relapse. This advantage must be weighed against other factors including cost effectiveness. The most pressing dilemma for the clinician is management of the patient with repeated episodes of acute streptococcal pharyngitis. Certain of these problem patients may benefit from a period of penicillin prophylaxis during the seasons when streptococcal infections are most prevalent. There is now agreement that posttreatment throat cultures need not be done in the child who remains asymptomatic following therapy. However, it is incumbent on the clinician to make certain that appropriate therapy is prescribed and that compliance with oral regimens of therapy is satisfactory in the management of the patient with acute streptococcal pharyngitis.

Acute Disease↗
PubMed1985

Penicillin-intermediate pneumococci in a children's hospital.

During the three-year period from 1981 to 1984, all clinical isolates of Streptococcus pneumoniae were screened for resistance to penicillin in the clinical bacteriology laboratory at The Children's Hospital of Alabama, Birmingham. Twenty-eight of 828 isolates were presumed resistant by disk diffusion testing with 1-microgram oxacillin disks (zone diameter, less than 20 mm). Seventeen of the 28 (61%) were found to be intermediately sensitive to penicillin by a conventional agar dilution method. Penicillin-intermediate strains had a minimal inhibitory concentration of 0.125 to 0.5 mg/L; no penicillin-resistant (minimal inhibitory concentration, greater than 1 mg/L) strains were encountered. The prevalence of penicillin-intermediate strains was thus 17 of 828 isolates, or 2.1%. These strains were also examined for susceptibility to ampicillin, vancomycin, cefotaxime, and chloramphenicol. We present the clinical features of 17 patients with disease due to penicillin-intermediate pneumococci.

Alabama↗
PubMed1985

The natural history of streptococcal skin infection: prevention with topical antibiotics.

An investigation on the natural history of streptococcal skin infection was done in fifty-nine children in a rural day care setting. A double-blind study for prevention of streptococcal pyoderma was done during the peak season for skin infection. Triple antibiotic ointment, containing bacitracin, polysporin, and neomycin, was compared to placebo ointment. Ointments were applied thrice daily for minor skin trauma; mosquito bites and abrasions were predominant. Cultures of normal skin surfaces were taken for group A streptococci each week of the 15-week study period. Skin lesions were cultured whenever present. Eighty-one percent of the fifty-nine patients had positive normal skin cultures on one or more occasions. Nineteen children (32%) developed streptococcal pyoderma. Infection occurred significantly more often in children using placebo ointment than in those using topical antibiotic (47% vs 15%; p = 0.01). The infecting strain was first recovered from normal skin surfaces in 67% of placebo patients and in two of the four patients using antibiotic ointment. This study further confirms the importance of skin carriage of group A streptococci as a precursor to pyoderma and demonstrates the importance of minor skin trauma as a predisposing factor. Topical antibiotics may be useful in preventing streptococcal pyoderma, especially in children known to be at increased risk for such infection.

Administration, Topical↗
PubMed1985

Seroepidemiological studies of group B Streptococcus type II.

In the course of prospective epidemiological studies of group B streptococcal (GBS) colonization and infection, we surveyed 401 paired maternal and cord sera (obtained at delivery) and 23 sera from patients with systemic type II infection for IgG antibody to GBS type II. Type II carriers were more likely to have antibody (greater than 2 micrograms/ml) than were those carrying other GBS types, whereas noncolonized patients were the least likely to have antibody. The overall prevalence of levels of antibody greater than 2 micrograms/ml was estimated to be approximately 6%, on the basis of assay results of the 401 maternal-cord pairs and adjusted for known-colonization status for the entire population of 8,928 deliveries that occurred during the study period. The majority of patients with infection had antibody levels less than 2 micrograms/ml. Five patients, however, had antibody present at levels ranging from 2.7 to 5.8 micrograms/ml. These findings suggest that "antibody deficiency" was widespread and was not by itself a useful determinant of risk for disease caused by GBS type II.

Antibodies, Bacterial↗