Wallace A. Clyde

Respiratory-syncytial-virus infections, reinfections and immunity. A prospective, longitudinal study in young children.

To better understand acquired immunity to respiratory-syncytial-virus infections, we analyzed data from a 10-year study of respiratory illness in normal children who were followed longitudinally from early infancy. Immunity was measured in terms of failure to become infected or reduction in severity of clinical illness upon reinfection. Outbreaks of infections occurred seven times over the 10-year-period. During epidemics the attack rate for first infection was 98 per cent. The rate for second infections (75 per cent) was modestly reduced (P less than 0.001); that for third infections was 65 per cent. Age and history of infection both influenced illness. Immunity induced by a single infection had no demonstrable effect on illness associated with reinfection one year later; however, a considerable reduction in severity occurred with the third infection. These observations suggest that amelioration of illness--rather than prevention of infection--may be a realistic goal for immunoprophylaxis.

A Longitudinal Study of Respiratory Viruses and Bacteria in the Etiology of Acute Otitis Media with Effusion

We analyzed data from a 14-year longitudinal study of respiratory infections in young children to determine the relative importance of viral respiratory infection and nasopharyngeal colonization with Streptococcus pneumoniae and Haemophilus influenzae as factors influencing the occurrence of acute otitis media with effusion. The incidence of this disorder was increased in children with viral respiratory infections (average relative risk, 3.2; P less than 0.0001). Infection with respiratory syncytial virus, influenza virus (type A or B), and adenovirus conferred a greater risk of otitis media than did infection with parainfluenza virus, enterovirus, or rhinovirus. Colonization of the nasopharynx with Str. pneumoniae or H. influenzae had a lesser effect on the incidence of the disease (average relative risk; 1.5; P less than 0.01). Infections with the viruses more closely associated with acute otitis media (respiratory syncytial virus, adenovirus, and influenza A or B) were correlated with an increased risk of recurrent disease. Prevention of selected otitis-associated viral infections should reduce the incidence of this disease.

The etiologic and epidemiologic spectrum of bronchiolitis in pediatric practice.

To develop a broad understanding of the causes and patterns of occurrence of wheezing associated respiratory infections, we analyzed data from an 11-year study of acute lower respiratory illness in a pediatric practice. Although half of the WARI occurred in children less than 2 years of age, wheezing continued to be observed in 19% of children greater than 9 years of age who had lower respiratory illness. Males experienced LRI 1.25 times more often than did females; the relative risk of males for WARI was 1.35. A nonbacterial pathogen was recovered from 21% of patients with WARI; respiratory syncytial virus, parainfluenza virus types 1 and 3, adenoviruses, and Mycoplasma pneumoniae accounted for 81% of the isolates. Patient age influenced the pattern of recovery of these agents. The most common cause of WARI in children under 5 years of age was RSV whereas Mycoplasma pneumoniae was the most frequent isolate from school age children with wheezing illness. The data expand our understanding of the causes of WARI and are useful to diagnosticians and to researchers interested in the control of lower respiratory disease.

Epidemiologic patterns of acute lower respiratory disease of children in a pediatric group practice

Comprehensive surveillance of acute lower respiratory illnesses of children seen in apediatric group practice was maintained for 67 months in Chapel Hill, North Carolina. The common pathogenic agents associated with these illnesses were respiratory syncytial virus, parainfluenza virus types 1 and 3, and Mycoplasma pneumoniae . Consistent patterns have been observed in the clinical manifestations, seasonal occurrence, and age and sex distribution of infections; these provide guidelines for clinicians, which allow reasonable estimates of the etiologic diagnoses. These studies have important implications for the understanding of disease pathogenesis and for the development of optimal methods of prophylaxis.

Occurrence of Diplococcus pneumoniae in the upper respiratory tract of children

The patterns of colonization of D. pneumoniae were studied over a 46-month period in a group of young children in a day-care center. Forty-four percent of nasal cultures yielded D. pneumoniae. The most frequently isolated serotypes--6, 19, and 23--accounted for 49% of the isolates; the nine most common serotypes included 80% of the isolates. Individual serotypes frequently were carried for several months. Reacquisition of a serotype previously carried occurred frequently. There was limited spread of serotypes among the children despite prolonged contact.

The unusual severity of mycoplasmal pneumonia in children with sickle cell disease

Abstract Five children with sickle-cell disease had severe mycoplasma pneumonia. The severity was greater than that noted with M. pneumoniae infection in otherwise normal persons. Clinical features...

Studies on the role of viruses, bacteria, and M. pneumoniae as causes of lower respiratory tract infections in children.

The etiological roles of bacteria, viruses, and mycoplasmas were assessed simultaneously in 2 different populations of children from the same geographic area. These patients, some from a typical private practice in a small town and others from a rural environment, represent groups that have not been studied extensively. The significance of the agents varied between the groups in terms of frequency, character of associated illness, and age of patients involved. The data indicate the need for long-term observations in differing epidemiological settings to provide a rational basis for prophylaxis, diagnosis, and therapy of acute respiratory diseases.

Biologic effects of Mycoplasma pneumoniae and other mycoplasmas from man on hamster tracheal organ culture.

Summary The applicability of organ culture systems to the study of mycoplasma infections is illustrated by the experiments described. Tracheal organ culture provided a controllable environment for analysis of the interaction between M. pneumoniae and the natural target cell of this pathogen, the ciliated respiratory epithelium. Mycoplasma pneumoniae produced distinct cytopathology in this system that was not seen with other human mycoplasmas tested. In addition, virulent M. pneumoniae produced tissue damage more effectively than did an attenuated strain. The observations suggest that this experimental model may be useful for the analysis of factors contributing to organism pathogenicity.

Hemolysis in Identifying Eaton's Pleuropneumonia-Like Organism

A method for readily demonstrating hemolysis of mammalian erythrocytes by Eatons pleuropneumonia-like organism is described. This reaction may be useful in preliminary identification of this organism, since other strains from human sources are not known to have this property.

The Interrelationship of Virulence, Cytadsorption, and Peroxide Formation in Mycoplasma pneumoniae

Summary A study of the relationship between virulence, peroxide formation, and cytadsorption in M. pneumoniae was undertaken. Two pairs of homologous virulent and attenuated strains were derived by passage of parent strains in animals and artificial media. Comparison of their cytadsorptive activity and peroxide formation by measurement of hemadsorption and hemolysis revealed variations between heterologous strains, but no differences consistently related to virulence. The existence of additional mediators of virulence is suggested.