Protection of mice from experimental infection with type III group B Streptococcus using monoclonal antibodies.

Mouse hybridoma antibodies of several major classes against group B streptococcus type III have been produced. Mice were immunized with either whole heat-killed or acid-treated organisms to obtain antibodies against both the complete (sialated) or incomplete (nonsialated) forms of the type III polysaccharide. Resulting monoclonal antibodies showed exclusive specificity for either the complete or incomplete antigen. The ability of these antibodies to protect mice from a lethal challenge of live type III organisms was tested with a mucin model that permitted use of very small inocula given intraperitoneally with antibody and mucin. Antibodies specific for the nonsialated antigen were not protective, whether of IgM, IgG2a, or IgG3 isotypes. Antibodies specific for the complete antigen were, however, highly protective, including monoclonals of IgM, IgG2a, and IgA isotypes. These mouse monoclonal antibodies against group B streptococci that are directed against either complete or incomplete antigenic determinants, and include isotypes other than IgM, should be particularly useful for studying the mechanism of protection against experimental infection.

Complement in overt and asymptomatic nephritis after skin infection.

In an ongoing study of streptococcal skin infection and acute glomerulonephritis (AGN) begun in 1964, C'3 determinations were done in 784 patients. There were 126 patients with acute poststreptococcal nephritis, 172 of their siblings, and 486 patients with uncomplicated impetigo from families without an index case of nephritis.90% of the patients with nephritis were infected with one of the four prevalent streptococcal serotypes associated with nephritis in this population; only 12% of patients with uncomplicated impetigo were infected with similar serotypes.93% of the patients with overt nephritis had diminished complement levels. Low complement was more often observed (8%) in AGN siblings than was transient hypertension and/or hematuria (5%). Considering the relationship of low C'3 alone and low C'3 preceded hematuria in four others. Two (0.4%) of the patients with uncomplicated impetigo had low complement values, both of whom were infected with nephritogenic strains. Transient hematuria and/or hypertension was less frequently observed (2.7%) among patients with uncomplicated impetigo. Serial determinations in patients with low complement revealed a return to normal in a linear fashion within 2-12 wk. The validity of the hypothesis that the asymptomatic patients with low complement levels, with or without hematuria, likely had subclinical nephritis is strengthened by the accompanying epidemiologic data. The finding of low complement before the onset of, or in the absence of, hematuria or other evidence of nephritis supports the concept that an immunologic mechanism may precipitate the renal injury of acute streptococcal nephritis.

Interaction of group B streptococcal type-specific polysaccharides with wheat germ agglutinin and other lectins.

The group B streptococci (GBS) are known to have type-specific polysaccharides rich in N-acetylneuraminic acid end groups, which are thought to be important immunological determinants. Wheat germ agglutinin (WGA) has affinity for N-acetylneuraminic acid as well as N-acetylglucosamine, and readily precipitates the type but not the group polysaccharide. A WGA-Sepharose affinity column was used to isolate complete type polysaccharides of representative strains of the 4 major GBS types. WGA, other lectins, and rabbit antisera were then used to characterize the products of various extraction procedures and chemical degradations, including mild acid hydrolysis and treatment with neuraminidase. Results of lectin binding studies were consistent with proposed chemical structures of types Ia, Ib and II. Differences were noted, however, between the cross-reactive antigens of pneumococcus type 14 and the desialated GBS type III polysaccharide. Although structurally similar, indirect evidence from lectin binding studies suggest that these antigens may not be identical.

Clinical experience with clindamycin hydrochloride: I. Treatment of streptococcal and mixed streptococcal-staphylococcal skin infections.

Two hundred and forty-four children were evaluated in a study comparing clindamycin hydrochloride, erythromycin, and phenoxymethyl penicillin for the treatment of streptococcal pyoderma. Similar numbers of patients were followed during (day 7) and after (day 14) therapy in each of the three treatment groups. All patients had skin lesions positive for group A streptococci with or without staphylococci; the percentage rate of pure and mixed cultures was similar for the three groups of patients. Both clindamycin and erythromycin proved somewhat superior to penicillin on the basis of effecting earlier clinical cures and sterilization of skin lesions. Streptococcal eradication rates by day 7 were as follows: clindamycin, 97%; erythromycin, 99%; and penicillin, 91%. By day 14, clinical and bacteriologic cure rates were essentially the same in each group: clindamycin, 99%; erythromycin, 99%; and penicillin, 97%. Persistence or reacquisition of a pyoderma strain in the upper respiratory tract was highest in that group treated with penicillin. There were no adverse reactions associated with clindamycin or the other antibiotic agents evaluated. However, clindamycin holds no advantage over erythromycin for treatment of streptococcal pyoderma, and additional clinical information will be required to determine whether the potential for toxicity in children will compromise the use of this newer antibiotic.

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.

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.

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.

Treatment of staphylococcal skin infections: a comparison of cephalexin and dicloxacillin.

Cephalexin, given twice daily, and dicloxacillin, given four times daily, were compared in a randomly controlled study for the treatment of staphylococcal skin and skin structure infections. Among 70 evaluable patients, 57 had staphylococcal bullous impetigo. The remaining 13 patients had bullous impetigo with streptococcal or mixed streptococcal-staphylococcal cultures (6 patients), abscess (4 patients), or cellulitis with pyoderma (3 patients). Staphylococci were recovered from lesions of 64 of the 70 evaluable patients; all strains were sensitive to both cephalexin and dicloxacillin, but only 2 of the 64 strains were susceptible to penicillin G. Cephalexin and dicloxacillin proved equally effective. Treatment failures were uncommon (1 patient in each group), and recurrences (3 patients in each group) were limited to patients with bullous impetigo. In general, patients with staphylococcal bullous impetigo responded promptly, with clearing of lesions evident within the first week, but delayed healing with persistence of staphylococci in lesions was more common in the group receiving dicloxacillin. Twice-daily dosing with oral antibiotics is obviously convenient and may enhance compliance. Twice-daily therapy with cephalexin for staphylococcal skin and skin structure infections can be recommended with confidence.

Post-streptococcal glomerulonephritis following pyoderma.

Studies of the epidemiology of acute glomerulonephritis (AGN) following pyoderma reported over the past 15 years have been reviewed. Investigations in Alabama, at Red Lake in Minnesota, and in Trinidad proved of special interest because they contribute new information concerning the natural history of streptococcal skin infections and the role of such infections in AGN. Interesting contrasts between streptococcal infections of the skin and those of the throat are now apparent. Compared with pharyngeal infections, skin infections are more common in young preschool children, are caused by different serotypes, and differ in the nature of the streptococcal antibody response. A number of new M-serotypes of group A streptococci, including several of importance in AGN, were found in studies of pyoderma. In contrast to M-types 1 and 12 (those of major importance in AGN followng pharyngitis), M-types 2, 49, 55, 57, and 60 are now recognized to be of major importance in AGN following pyoderma. Although streptococcal skin infections are quire important in AGN, they do not result in acute rheumatic fever.

Erythromycin therapy for streptococcal pharyngitis.

Streptococcal eradication rates of 86% were demonstrated in 97 patients seen on day 14 and in 73 patients seen on both days 14 and 28 after a ten-day course of erythromycin estolate therapy given at a dosage of 20 mg/kg/day, administered in two equal doses. The efficacy of this regimen compares favorably with other results in which this and other erythromycin preparations have been employed at higher doses, usually in the range of 30 to 50 mg/kg/day. Our reported effectiveness at a lower than usual dose of erythromycin is probably explained by the following factors: the known susceptibility of group A streptococci to low concentrations of erythromycin, the uniform absorption of the estolate formulation of erythromycin, and adequate compliance in adhering to the treatment regimen by the majority of our patients. This dosage schedule of erythromycin is simple to administer; and a reduction by half of the total dose usually recommended provides an economical advantage for patients.

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.

New streptococcal serotypes causing pyoderma and acute glomerulonephritis types 59,60, and 61.

Three new streptococcal M serotypes, types 59, 60, and 61; have been described. They were first isolated from patients with pyoderma and acute glomerulonephritis (AGN), seen during epidemiological studies in Alabama. A possible antigenic relationship between types 59 and 61 was suggested by their T-agglutination reactions; a more specific T antiserum prepared for type 59 was useful in separating these two types, as well as other strains known to share T antigens 11, 12, and 5/27/44. On the basis of precipitin tests, a common antigenic determinant among types 59, 61, and 49 was suggested. This is of interest in view of the relation between these types and AGN. Type 59 has been relatively more widespread in distribution than type 61, but neither have been related to epidemic AGN. Type 60, first identified as "T-4," thus being related to previously described M types which share this antigen, is of great interest in terms of the epidemiology of AGN. Most strains in our collection were recovered from patients with pyoderma and AGN or from their infected siblings. Recently, the type was found to be prevalent among patients with pyoderma and AGN seen in Trinidad. Data reported in relation to these new types further illustrate the dichotomy in M serotypes common to pyoderma and AGN on the one hand and those types found in collections of patients with pharyngitis on the other hand. The high rate of non-M-typable streptococci among pyoderma collections, encountered earlier, is best explained by lack of suitable reference antisera available for prevalent pyoderma serotypes.

Clinical and epidemiologic studies of pneumococcal infection in children.

Streptococcus pneumoniae was isolated from 1310 children in a 5-year period from 1979 through 1984. There were 44 cases of meningitis, 172 bacteremic infections, 787 cases of otitis media and 307 respiratory and miscellaneous isolates. The majority of infections could be accounted for by a small number of serotypes, with types 3, 6, 14, 19 and 23 predominating. Most infections (70%) occurred in infants younger than 2 years of age. However, nearly one-fourth of those suffering systemic illness had some underlying condition which may have contributed to their risk for infection, even beyond 2 years of age. Ten of the 12 deaths occurred in patients with altered host defenses. Characteristics of pneumococcal disease and the distribution of serotypes are discussed in relation to the work of other investigators over the past 50 years.

Epidemiological studies of Streptococcus pneumoniae in infants: methods of isolating pneumococci.

A prospective study of the natural history of pneumococcal infection, which involves serial culture studies in healthy infants from 6 weeks of age onward, is in progress in our laboratory. This report describes results of a comparison of several methods for the isolation and identification of Streptococcus pneumoniae from the nasopharynges and throats of these infants. Sheep blood agar, sheep blood agar with gentamicin sulfate (gentamicin agar), and mouse inoculation with 4-h broth cultures were used. Gentamicin agar proved superior to plain sheep blood agar as a solid culture medium, especially in enhancing the recovery of pneumococci from throat cultures. With gentamicin agar, similar carrier rates were found for both culture sites (nasopharynx and throat). In addition, gentamicin agar proved superior to mouse inoculation for the recovery of carrier strains from 131 nasopharyngeal culture samples processed by both methods. Sixty of 131 samples were positive for pneumococci, 25% of which would have been missed had mouse inoculation alone been used. In only three instances did we recover a strain by mouse inoculation that failed to grow on gentamicin agar; conversely, 15 strains were isolated on gentamicin agar but could not be recovered from mice. The latter observation might be explained by the fact that certain carrier strains may be relatively mouse avirulent. The use of blood agar containing gentamicin appears to offer a simple and inexpensive method for the recovery of S. pneumoniae and, in our opinion, provides an ideal method for the identification of pneumococcal carriers as well as for the recovery of these strains from clinical material such as sputum or ear exudates, where other and less fastidious organisms may also be present.

Streptococcal pharyngitis therapy. A comparison of two erythromycin formulations.

The recommended dosage of erythromycin, without regard to the formulation prescribed, for children with streptococcal pharyngitis is 30 to 40 mg/kg/day. We previously reported an acceptable streptococcal eradication rate among patients with pharyngitis treated with erythromycin estolate, 20 mg/kg/day. In this study, an extension of the earlier one, the efficacy of this same dosage of erythromycin estolate was compared with a 40 mg/kg/day dosage of erythromycin ethylsuccinate. Streptococcal eradication rates were nearly identical in the two groups of patients. The efficacy of erythromycin estolate at a dosage lower than that recommended for children is most likely explained on pharmacologic grounds: better absorption and higher levels in serum and tissue than those achieved with other erythromycin formulations. It seems rational to calculate required dosages of erythromycin on the basis of the formulation being administered.