Biomedical subjects
Publications and source records attributed to R H Michaels.
Strains of pneumococci moderately resistant to penicillin were recovered from three patients at the Children's Hospital of Pittsburgh during 1978. One of these children had meningitis and showed signs of early relapse despite high doses of penicillin G potassium. Routine screening of pneumococci for penicillin resistance is recommended.
A double-blind, randomized clinical trial comparing cefaclor with amoxycillin in the treatment of acute otitis media with effusion (OME) in infants and children is being conducted at Children's Hospital of Pittsburgh. Although the randomization code has not yet been broken, the results of treating the first 55 children are reported, since they appear to be of interest. Of the 62 ears with acute OME on which an initial tympanocentesis was performed, 41 positive cultures were isolated from the middle ear aspirates. Of the 10 ears from which Haemophilus influenzae was isolated, one had a type b strain, and of the remaining unencapsulated strains, one was resistant to both penicillin G and ampicillin. In the one ear from which Staphylococcus aureus was isolated, the organism was found to be resistant to ampicillin. However, all of the organisms were sensitive in vitro to cefaclor. In 88% of all subjects observed for the first 2 weeks, the initial symptomatic response was excellent. Six children had persistent signs and symptoms of acute OME and received a second tympanocentesis; however, none of the effusions from the repeat aspiration revealed an organism. An effusion was still present in 97% of the ears after 3 days, in 69% after 2 weeks, and in 48% 6 weeks after initiation of the study. Tympanocentesis did not appear to affect either the initial clinical response or the persistence of effusion. There were no adverse reactions to either drug in this study. Because an apparent increase in the incidence of ampicillin-resistant strains of H. influenzae is being reported, and because of the presence of ampicillin-resistant S. aureus in some ears with acute OME, a new antimicrobial effective against all the common pathogens causing acute middle ear disease would be desirable. In this respect, the preliminary findings of treatment with cefaclor from this study appear promising.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Two serotypes, uncommon in pediatric infections, accounted for a disproportionately large number of cases of pneumococcal empyema at the Children's Hospital of Pittsburgh. Eight of ten empyemas were caused by types 1 or 3, and two additional cases of mixed infection involved the type 3 pneumococcus. The type 3 pneumococcal empyemas tended to be more severe than those due to other serotypes. Counterimmunoelectrophoresis (CIE) appeared to be more useful than culture in establishing the cause of this condition; in seven of ten cases, the pleural fluid was CIE positive while cultures of blood and pleural fluid were negative. In each of the seven culture-negative cases, antibiotics had been given prior to hospitalization. One case of type 7 pneumococcal empyema illustrated the potential value of the Ouchterlony test for the etiologic diagnosis of this condition.
The growth of parent influenza viruses A/England/939/69 and A/PR/8/34, and clones 6, 7, and 64C, derived by recombination, was studied in newborn rats. Using an inoculum of 10(4.0) EID50, influenza virus A/England/939/69 produced the highest titres of virus in rat turbinates at 48 hours after inoculation; clones 6 and 7 and A/PR/8/34 grew to lower titres; and clone 64C grew to the lowest titre. These differences were less apparent when 10(2.0) EID50 of virus was used as an inoculum, and rats were not infected by smaller inoculum of any of the virus strains. Infection with 10(4.0) EID50 of all viruses produced lung infection; at 48 hours after infection, the highest titres were recovered from rats infected with A/PR/8/34 and A/England/939/69 virus. Prior infection with A/England/939/69 or A/PR/8/34 increased the incidence of bacteraemia and meningitis following intranasal inoculation of Haemophilus influenzae type b; infection with clone 64C did not enhance bacterial meningitis, while infection with clone 6 gave an intermediate result. Volunteer studies with these viruses have shown that influenza virus A/England/939/69 was virulent, clones 6 and 7 were attenuated, clone 64C was over-attenuated, and A/PR/8/34 virus was noninfective for man. The relative titres of virus recovered from turbinates taken 48 hours after infection with 10(4.0) EID50 of virus and the ability of virus infection to enhance bacterial infection correlated with the property of virus attenuation for man for four of the five strains tested; however, no correlation was seen for A/PR/8/34 virus, which is a result also found in other laboratory tests designed to measure virulence for man.
Explore the source record for details and available documents.
A study was conducted of 274 children who had recurrent acute or chronic otitis media with effusion. Forty-five percent of the ears with effusion were found to contain bacteria, and 11% contained bacteria that were "probable pathogens" (S. pneumoniae, H. influenzae, and S. pyogenes). Bacteria were also found in 40% of the ears without effusions. The type of organism found did not vary with the age of the patient studied or the season of the year. The significance of these bacteria in the etiology of recurrent acute or chronic otitis media with effusion remains to be demonstrated.
When Haemophilus influenzae type b was given intranasally to infant rats, a very large dose was required to produce histologic evidence of meningitis in even half of the animals tested; meningitis developed in 16 of 31 rats that received 10(7) viable bacteria at the age of five days. However, when the animals first received influenza virus, the dose of bacteria required to produce meningitis was reduced 100-fold; meningitis occurred in 10 of 21 rats given virus at two days and 10(5) viable bacteria at five days. These results suggest that prior viral infection of the upper respiratory tract may be a factor in the pathogenesis of haemophilus meningitis.
A longitudinal study of pharyngeal colonization with Haemophilus influenzae type b included 264 members of families that had a child with meningitis or epiglottitis due to this organism. It was found that (1) 52 of 67 such families contained at least one carrier of H. influenzae type b, who was usually a sibling; (2) H. influenzae type b spread slowly in 39 families colonized continuously during a six-month period, with only eight of 19 uncolonized siblings acquiring the organism during that time; (3) 18 of 30 initially colonized families contained one or more carriers after 12 months, including 30% of initially colonized siblings; (4) the highest carrier rate of H. influenzae type b occurred in recovered patients, 80% of whom were colonized after hospital discharge; (5) titers of antibody in serum were higher in colonized than in uncolonized individuals (P less than 0.001); (6) levels of antibody in colonized children were lower in those younger than two years than in older children (P less than 0.001); and (7) prolonged or heavy colonization with H. influenzae type b was not associated with unusually high titers of antibody.
A review of 104 patients with acute orbital cellulitis during the past decade showed that the frequency of hospital admissions for this disease has increased recently. Roentgenograms showed paranasal sinus in 77 of 91 patients. Haemophilus influenzae and Diplococcus pneumoniae were recovered from the blood of 20 and 6 patients, respectively. Four children had concomitant H influenzae meningitis. Bacteremia was demonstrated in 29% and more common in those with extensive orbital involvement, those not receiving antibiotics at the time of culture, and those less than 2 years old. Some of the 26 patients with less extensive involvement were bacteremic (17%), had leukocytosis, or roentgenographic evidence of sinusitis. Most children received large doses of ampicillin sodium and methicillin sodium intravenously until signs and symptoms had almost abated. With this regimen, there were no orbital, ocular, or other complications.
Explore the source record for details and available documents.
The immunologic responses of 100 children hospitalized with meningitis due to Haemophilus influenzae type b were measured by the bactericidal antibody assay (BAA) and radioimmunoassay (RIA) for detection of antibody. Short-term (14-17 days after onset of illness) responses were detected by RIA alone in 20 children, by BAA alone in six, and by both tests in 23. The more sensitive RIA detected 20 children who would have been labeled "immunologically unresponsive" had only BAA been used. The magnitude of the antibody response was clearly related to age. Of 26 children with no immediate antibody response, 11 still had no rise in titer of antibody when restudied two to 20 months later; the remaining 15 had subsequent increases in titer. Nine of 10 children who showed an immediate antibody response remained positive when additional blood smaples were taken two to 18 months later. Over half of the children initially unresponsive to H. influenzae type b meningitis subsequently developed specific antibodies. The remainder, who failed to acquire detectable antibodies at either the acute stage of illness or late in convalescence, deserve further investigation as to the nature of their immunologic hyporesponsiveness to H. influenzae type b meningitis.
Over 1,300 children were studied in an analysis of factors that might affect pharyngeal colonization with Haemophilus influenzae type b. Our semiquantitative methods for the culture of H. influenzae type b, consisting of inoculation of 0.001 ml of throat swab fluid on antiserum agar plates and division of the results into three grades of intensity, showed agreement as to intensity of colonization in over 80% of repeat throat cultures. Our data also suggest that throat swabs are more efficient than nasopharyngeal swabs for detecting colonization, particularly for older children. All 17 H. influenzae type b carriers found with either method were detected with throat swabs, but six had negative nasopharyngeal cultures; four of these six were lightly colonized older children. Furthermore, colony counts were apt to be higher on plates inoculated with throat swab fluids. The frequency of pharyngeal H. influenzae type b colonization in children visiting health department clinics and pediatricians' offices was low during the first 6 months of life (0.7%) but averaged 3 to 5% throughout the rest of childhood. Approximately two-thirds of the carriers were colonized at an intensity too low to be detected by standard laboratory techniques. No influence on colonization rates was found for sex, race, season, economic status, or common childhood infectious diseases such as coryza or otitis media.
Twenty-seven cases of Reye's syndrome (RS) were admitted over a 19-month period to one urban hospital. All lived in a suburban or rural location and 23 cases occurred during two influenza outbreaks. Two to three months following the last cases of RS, 24 families of RS cases and 21 control families representing neighbors or friends were interviewed for factors which could predispose to RS. Children with RS had an illness immediately preceding the onset of RS more frequently than did controls (p less than .001). No other clinical, familial, or environmental factors distinguished RS children and families from controls. Water samples, collected during the interviews, from 34 homes showed no potential toxins. The geographic pattern of RS cases with localization exclusively to rural areas suggests that an as yet unidentified environmental factor may be related to the development of RS.
In early 1974, seventeen children were treated for Reye syndrome. Thirteen of these were studied for laboratory evidence of concomitant viral infection. Influenza B/Hong Kong was isolated from the pharynx in four of nine 1974 cases tested. One child had just recovered from varicella. Adenovirus type 2 and respiratory syncytial virus were isolated from two additional patients. Serologic tests for influenza suggested concomitant or recent influenza B infection in ten of 13 of 1971 cases. During February 1975, six children were treated for this syndrome. Influenza A/Port Chalmers was recovered from three in six 1975 cases, and all six showed significant antibody rises to influenza A. These studies suggest that influenza viruses provide a trigger mechanism for the development of Reye syndrome in susceptible children.
Children who had recovered from meningitis, orbital cellulitis, or epiglottitis caused by Haemophilus influenzae type b were immunized with capsular polysaccharide vaccine derived from that bacterium; some healthy siblings and adults who had not had H. influenzae infections were also vaccinated. Of 10 children who had had H. influenzae meningitis previously, only one had an antibody response to the vaccine. One child with prior H. influenzae orbital cellulitis also failed to respond. None of the children had detectable H. influenzae polysaccharide antigen in their bloodstream at the time of immunization. Two children who had had H. influenzae epiglottitis and six of seven controls without histories of H. influenzae infections responded immunologically to the vaccine. One of eight vaccinees under two years of age showed a response, and eight of 12 over two years responded well (P = 0.02). All four nonresponders over the age of two years had had H; influenzae meningitis or cellulitis. Children who had had H. influenzae meningitis responded less well to the polysaccharide vaccine than did other recipients of the vaccine; this difference could not be explained solely on the basis of age;
An antiserum agar medium was found to provide a rapid, sensitive, and highly specific method for pharyngeal culture and quantitation of HIB.