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Biomedical subjects

C R Dawson

Publications and source records attributed to C R Dawson.

At least 91 records · Page 5Linked to original sources
PubMed1977

Antibiotic susceptibility of Chlamydia trachomatis.

The antibiotic susceptibility of Chlamydia trachomatis isolates was determined in a tissue culture system. Representatives of all currently recognized serotypes of trachoma-inclusion conjunctivitis agents were tested. Tetracycline and erythromycin yielded similar results, with 1.0 mug/ml preventing chlamydial replication. Rifampin was the most active antibiotic, with 0.25 mug/ml completely suppressing inclusion formation of all strains. Fifty percent end points were usually achieved at one-fourth to one-eighth the 100% suppression level. Penicillin was not as effective, and the assays were often irregular. Antibiotic susceptibility of these chlamydiae was essentially the same, regardless of serotype, anatomic site infected, geographic origin, or antibiotic use in the community.

Chlamydia trachomatis↗
PubMed1977

Resistance to reinfection with a chlamydial agent (guinea pig inclusion conjunctivitis agent).

Although most chlamydial infections are chronic or recurrent, infection of the guinea pig's eye with guinea pig inclusion conjunctivitis (GPIC) agent induces a marked resistance to reinfection. To characterize this resistance to GPIC agent, we compared the disease and infection in previously infected guinea pigs with that in animals infected for the first time. In animals experiencing primary infection, even the lowest dose (10 egg-lethal doses [ELD50]) produced the disease and chlamydial inclusions in conjunctival smears, but the incubation period became progressively shorter with the highest inocula (10(4) and 10(5) ELD50). In animals with previous infection only these two highest inocula produced disease and infection, but the disease was short-lived, and replication of the agent was severely limited. The mechanism of this resistance may be due to secretory antibody in the tears, cellular immunity, or other local factors.

Animals↗
PubMed1976

Acute hemorrhagic conjunctivitis in Tunisia. Report of viral isolations.

Acute hemorrhagic conjunctivitis (AHC), a new disease entity first reported in 1969, has since become pandemic throughout the world. In Tunisia during an epidemic in 1972 to 1973 we studied 25 cases of AHC, which were characterized by explosive onset of lid edema, chemosis, conjunctival hemorrhages, follicular hypertrophy, and epithelial keratitis. Clinical signs peaked in 48 hours and cleared without sequelae in five to seven days. Paired acute- and convalescent-phase sera from six of the patients showed a rising titer of neutralizing antibody to the prototype strain of AHC virus (J6 70/71), which was isolated in Japan. Two viral isolates from Tunisian patients were also antigenically related to the Japanese strain, indicating that a single etiologic agent (a new member of the picornavirus group) is probably responsible for the current pandemic of AHC.

Antibodies, Viral↗
PubMed1976

Herpes simplex keratitis in a developing country. Natural history and treatment of epithelial ulcers in Tunisia.

Herpes simplex keratitis was found to be a common ophthalmic problem in Tunisia. Dendritic and geographic ulcers were complicated by deep stromal keratitis in 31% of patients, two thirds of whom were known to have been treated previously with corticosteroids. Herpes simplex virus was isolated from 41% of patients from whom corneal material was cultured. To develop an effective program for management of epithelial herpes in developing countries, treatment with idoxuridine was compared with debridement and patching. Average healing time for 31 ulcers treated with idoxuridine was 13 days, with three treatment failures; average healing time for 20 ulcers treated with debridement and patching was five days, with one failure. Debridement and patching of herpetic ulcers was an efficient way to treat herpes simplex keratitis within the context of overall medical care in Tunisia.

Adult↗
PubMed1976

The taxonomy of haemophili isolated from conjunctivae.

The paper provides a description of 112 Haemophilus strains isolated from cases of conjunctivitis in Egypt, Tunisia, Denmark, and the U.S.A., and aims at a clarification of the taxonomy of haemophili implicated in conjunctivitis. Although the study confirms the diversity of haemophili which can be isolated from inflamed conjunctivae, the vast majority of strains could be assigned to either biotype II or III of H. influenzae. Thirteen strains possessed all the characteristics of the Koch-Weeks bacillus. However, judged by the findings the recognition of the Koch-Weeks bacillus as a separate species does not seem tenable. It is suggested that this organism is considered a haemagglutinating variety of H. influenzae biotype III. The study indicates that the haemagglutinating ability per se, which can be found in strains of several taxa of Haemophilus, is associated with a special pathogenic potential.

Child, Preschool↗
PubMed1976

Antibodies to two immunotypes of Chlamydia trachomatis in individuals with trachoma.

In Tunisia (North Africa), trachoma remains a common eye disease. Most cases are caused by immunotype A of Chlamydia trachomatis. In a small proportion of cases (less than 10%), type-specific antibodies to both immunotype A and immunotype B exist in the serum of patients. These types do not crossreact, and occasionally sequential acquisition of antibodies has been demonstrated. Thus, individuals in one endemic area of trachoma may be infected with two immunotypes of C. trachomatis. The epidemiological and immunological implications of this new finding are briefly discussed.

Antibodies, Bacterial↗
PubMed1976

Severe endemic trachoma in Tunisia.

In two villages in southern Tunisia where trachoma was endemic 7 per cent and 14 per cent of adults respectively had visual acuity of 20/400 or less. In both villages active trachoma affected most children under the age of two, reached a peak in two- to five-year-olds, then declined to age 15. The chronic inflammatory disease in childhood appeared to produce irreversible scarring of the eyelids, and loss of vision occurred in adult life due to corneal scarring caused by inturned eye lashes and loss of tears (dry-eyed syndrome). Economic development in one village was associated with a decline in active, infectious disease. In the second village, whose traditional economy was unchanged, there was the same prevalence of active disease over a three-year period. Unless economic development or public health control programmes reduce the prevalence of severe and moderate trachoma children now affected will develop the same blinding lesions as their parents. With the increasing numbers of children who survive there will probably be a dramatic increase in the numbers of the blind from trachoma in 10 to 20 years. Since active inflammatory trachoma in childhood responds to tetracyclines, erythromycin, and sulphonamides the disease should be attacked in those undeveloped rural areas where it continues to lead to blindness.

Adolescent↗
PubMed1975

Topical tetracycline and rifampicin therapy of endemic trachoma in Tunisia.

A controlled chemotherapy trial of trachoma was carried out in a Tunisian oasis among schoolchildren with active disease. We compared 1% tetracycline ointment (79 patients) or 1% rifampicin ointment (76 patients) with 5% boric acid ointment (79 patients). Medications were administered twice daily, six days a week, for ten weeks. Slit-lamp examinations by three ophthalmologists were made independently before treatment as well as five, 19, and 39 weeks after treatment. Bacteriologic cultures were taken during treatment as were smears to detect trachoma agent at each clinical examination. Five weeks after treatment, the intensity of conjunctival disease in the tetracycline and rifampicin groups was reduced significantly when compared with boric acid, but at 19 weeks this suppression was found only in the tetracycline group. Ocular bacterial pathogens were eliminated almost entirely in the two antibiotic groups during treatment. The initial prevalence of trachoma (29to 31%) was significantly reduced in the two antibiotic-treated groups at five weeks and 19 weeks after treatment. The prevalence of trachoma was equally low (7%) in all three groups following retreatment with tetracycline. Although both antibiotics were effective, rifampicin offered no advantage over tetracycline in this trial. Recurrent disease in this school-based treatment study probably was due to reinfection from younger siblings at home. While systematic, community-wide, antibiotic treatment programs are not always possible in countries where trachoma is endemic, limited antibiotic therapy programs should be continued in these areas to reduce the intensity and prevalence of trachoma, even though the disease cannot be eradicated.

Administration, Topical↗
PubMed1975

Phosphonoacetic acid in the treatment of experimental herpes simplex keratitis.

In a rabbit model of herpes simplex corneal ulceration, 5% phosphonoacetic acid solution or ophthalmic ointment suppressed clinical disease and virus replication. The effect of 5% phosphonoacetic acid ointment was equivalent to that of 0.5% idoxuridine ointment in the treatment of this established herpetic eye infection.

Acetates↗
PubMed1975

Cytology as a guide to the presence of chlamydial inclusions in Giemsa-stained conjunctival smears in severe endemic trachoma.

Microscopical examination of 927 Giemsa-stained conjunctival smears from children with chronic trachoma in southern Tunisia showed 93 (10 per cent.) with typical trachoma (chlamydial) inclusions in epithelial cells. The accompanying cytological features were a useful indicator for inclusions. Inclusions were found only in slides with numerous polymorphonuclear neutrophils (PMNs) and separation of the epithelial cells. When these two features alone were present, 3 per cent. of the smears were inclusion-positive; when many lymphocytes were present also, 25 per cent. were inclusion positive; when other cytological features (plasma cells, macrophages, blastoid, and stem cells) were present as well, 70 per cent. of the smears were inclusion-positive. The occurrence of these sets of cytological features can be a useful guide for selecting smears for intensive examination for chlamydial inclusions. Immunofluorescent (FA) staining and Giemsa staining of 527 pairs of matched smears detected trachoma agent in 67 (13 per cent.); in thirty by both methods, in thirteen by Giemsa staining alone, and in 24 by FA alone. The examination of Giemsa-stained smears for chlamydial inclusions is a useful technique for the diagnosis of trachoma or inclusion conjunctivitis by laboratories that do not have the specialized facilities for the identification of these chlamydial infections by the technically more complex procedures of immunofluorescent staining or isolation in embryonated eggs or tissue cultures.

Bacteria↗
PubMed1975

Blinding and non-blinding trachoma: assessment of intensity of upper tarsal inflammatory disease and disabling lesions.

A simplified method of evaluating both the intensity of active inflammatory disease and the visually disabling lesions of trachoma is presented. Evaluation of the active disease is based on the scoring of clinical signs, lymphoid follicles, and papillary hypertrophy. The irreversible lesions of trachoma are classified as conjunctival scarring, trichiasis and/or entropion, and corneal scarring.

Blindness↗