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Biomedical subjects

H C Dillon

Publications and source records attributed to H C Dillon.

At least 55 records · Page 3Linked to original sources
PubMed1979

Laboratory and field evaluation of selective media for isolation of group B streptococci.

Problems encountered with currently recommended selective media for group B streptococci (GBS) (selective broth medium and CNA agar) prompted a searach for alternative culture methods in ongoing epidemiological studies. Previously recommended inhibitory agents were tested in vitro. Gentamicin, alone or in combination with nalidixic acid, proved inhibitory for many GBS strains. Among other agents tested, polymyxin was most complementary to the gram-negative spectrum of nalidixic acid, without compromising GBS growth. Crystal violet provided the simplest, most economical staphylococcal inhibitor. Broth and agar media, constituted with these three agents and designated NPC, were evaluated in vitro and in field studies. This investigation represents the first direct comparison of broth media containing inhibitory agents for the preferential isolation of GBS. In maternal colonization studies, NPC broth proved superior to Todd-Hewitt broth containing nalidixic acid and gentamicin at concentrations employed in the previously described selective broth medium (95% versus 59% recovery). Our comparisons were done without added sheep blood since GBS grow well in Todd-Hewitt broth. NPC broth proved more sensitive than NPC agar for detecting GBS colonization in newborns. The NPC agar medium was useful for further purification of broth cultures and quantitative culture techniques.

Bacteria↗
PubMed1979

Clinical and laboratory studies with cefaclor: efficacy in skin and soft tissue infections.

Clinically relevant, recent isolates of common Gram-positive pathogens were examined for their in vitro susceptibility to cefaclor. Group A streptococci and pneumococci were uniformly sensitive (MICs 0.06--0.12 micrograms/ml) to both cefaclor and cephalothin. Cefaclor was 5--10-fold less active than cephalothin against group B streptococci. S. aureus strains were uniformly more susceptible to cephalothin than to cefaclor, but among isolates from children, almost all were sensitive to the latter drug. In clinical studies of patients with skin and soft tissue infections, cefaclor proved effective. Over 90% of patients with staphylococcal bullous impetigo, streptococcal and mixed streptococcal-staphylococcal forms of pyoderma were cleared after 7--10 day courses of treatment. In addition, twice-daily therapy, examined more recently, proved as effective in these forms of infection as did the conventional dose schedule. No significant adverse reactions were noted. Cefaclor appears to be an effective orally absorbed cephalosporin for common skin and soft tissue infections.

Adolescent↗
PubMed1978

Susceptibility of Staphylococcus aureus to cefaclor and cephalothin: laboratory and clinical studies.

In vitro susceptibility tests of 201 strains of Staphylococcus aureus by agar dilution revealed 90% to be susceptible to 8 mug or less of cefaclor per ml. Strains from hospitalized children and adults were more often resistant than those from patients with bullous impetigo. Cephalothin was more active than cefaclor against all strains tested. Results with disk tests, including those strains examined from the clinical investigation, revealed some discrepancies in identifying strains more resistant to cefaclor. In clinical studies, cefaclor proved quite effective for the treatment of bullous impetigo. Of 73 patients, 90% were cured and 7% improved after completing 5 or more days of treatment. Prompt improvement was noted among most patients seen 3 to 5 days after treatment was begun. One patient experienced mild diarrhea. There were no other adverse or toxic manifestations attributable to therapy.

Adolescent↗
PubMed1977

Manner and meaning of susceptibility testing of ampicillin-resistant Haemophilus influenzae.

We examined ampicillin-resistant strains of Haemophilus influenzae to compare the percentage of resistant organisms in each strain with the susceptibility to ampicillin by an agar dilution method. Using an inoculum of 10(4) colony-forming units, the minimal inhibitory concentration (MIC) increased with the percentage of resistant organisms in the strain. Laboratory-manipulated strains composed of different proportions of a susceptible and a resistant strain behaved similarly. The survival of isolated colony-forming units (colony MIC) was then determined by spreading inocula over the surface of a set of MIC plates, resulting in separation of individual colonies. This modification of the susceptibility test to the colony level gave end points that were clear and reproducible and that did not vary with changes in incubation time or temperature. True differences in susceptibility among strains were demonstrated by this method, whereas results of the conventional MIC test may reflect only the number of resistant organisms present in the inoculum.

Ampicillin↗
PubMed1977

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.

Agar↗
PubMed1976

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.

Erythromycin↗
PubMed1976

A prolonged nursery epidemic associated with a newly recognized type of group A streptococcus.

During a six-month period 69 infants in a newborn nursery were colonized with group A streptococci. Fifty-one had omphalitis, two infected circumcision wounds, and one each had meningitis, primary peritonitis, and conjunctivitis. Thirteen infants were asymptomatically colonized. Control of the epidemic was difficult. Benzathine penicillin prophylaxis to all infants suppressed active infection but did not eradicate asymptomatic colonization of the umbilical cord. Triple dye treatment of the umbilical cord plus benzathine penicillin prophylaxis eradicated the infection from the nursery. The epidemic streptococcus was a newly recognized ""skin strain,'' provisional type strain 5656-S, not previously known to cause epidemic disease or serious systemic infections.

Disease Outbreaks↗
PubMed1975

A new M-type of group A streptococcus of clinical importance in pyoderma and pharyngitis.

A new M-type of group A streptococcus, provisionally designated type 65, is described. The vaccine and other initially isolated strains of this type attracted attention because of the T-agglutination reactions 2/25, not previously encountered among pyoderma streptococci. The investigations characterizing the strains as members of a new type were done with streptococci isolated from patients with pyoderma. However, type 65 was subsequently found to cause both pyoderma and acute pharyngitis. The T-2 agglutination reactions encountered with original members of this type, plus the cross-reactions later seen with type 65 antiserum and M-type 2 streptococci, prompted a comparison of this new type with M-type 2 streptococci, including those with the T-2 agglutination and others with the 8-25-Imp. 19 complex. The two M-antigens were clearly distinguished from one another in reciprocal bactericidal and precipitin tests with absorbed antisera. They were further distinguished in that all type 65 strains were opacity-factor (OF) negative, whereas type 2 streptococci were uniformly OF-positive. Most M-type 65 strains subsequently found in surveillance studies were shown to be members of the 8-25-Imp,19 T-complex. Type 65 is thus a newly described type which shares with M-types 55 and 57 a commom T-agglutination pattern and, like members of these types, fails to produce opacity factor. In our colleciton of strains, from both pyoderma and pharyngitis, shown to be members of the 8-25-Imp. 19 complex, and OF-negative, only type 65 has been identified to date. In contrast to types 55 and 57, the new type 65 does not appear to be of major importance in causing acute glomerulonephritis.

Agglutination Tests↗
PubMed1975

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.

Cells, Cultured↗
PubMed1974

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.

Antibodies, Bacterial↗