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Effect of Bacterial Secondary Infection in an Animal Model of Trachoma

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Effect of Bacterial Secondary Infection in an Animal Model of Trachoma INFECTION AND IMMUNITY, June 1984, p. 614-616 Vol. 44, No. 3 0019-9567/84/060614-03$02.00/0 Copyright C) 1984, American Society for Microbiology Effect of Bacterial Secondary Infection in an Animal Model of Trachoma HUGH R. TAYLOR,'* ROBERT A. KOLARCZYK,1 SHIRLEY L. JOHNSON,1 JULIUS SCHACHTER 2 AND ROBERT A. PRENDERGAST' The Wilmer Institute, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205,1 and Department of Laboratory Medicine, University of California, San Francisco, California 941102 Received 19 December 1983/Accepted 20 February 1984 In trachoma the interaction between chronic chlamydial and acute bacterial conjuntivitis has been suggested as important in determining the severity of disease and, therefore, blindness. We investigated the effect of acute conjunctival infection with each of three common human pathogens, Haemophilus influenzae, Haemophilus aegyptius, and Streptococcus pneumoniae, in a model of trachoma established in cynomolgus monkeys. Although acute conjunctivitis developed, animals with trachoma were not more susceptible to infection than other monkeys, nor did they develop more severe disease as a result of the bacterial conjunctivitis. The failure of bacterial conjunctivitis to exacerbate the experimental trachoma indicates that, in this model at least, chronically maintained chlamydial infection alone is sufficient to produce the changes characteristic of trachoma. In endemic human trachoma, episodes of bacterial con- and serum were collected for serological tests, smears were junctival infection are generally believed to produce more obtained from the superior tarsal plate for cytological study, intense inflammation and trachoma of increased severity, and conjunctival and nasopharyngeal swabs were taken for with an increased risk of blindness (2, 4). Although eyes chlamydial reisolation cultures in a cycloheximide-McCoy persistently inflammed by chronic chlamydial infection may cell tissue culture system and for bacterial reisolation cul- be more susceptible to chronic bacterial infection, the most tures on either blood agar or brain heart infusion agar plates florid bacterial conjunctivitis occurs in acute seasonal epi- (5). Although both eyes were examined, specimens were demics which sweep through trachomatous areas (2). Jones taken from the left eye only to eliminate the possibility of et al., in particular, have drawn attention to the interaction artifactitious changes in the right eye. of chronic chlamydial conjunctivitis and acute mucopurulent C. trachomatis Bour, an E serotype, was grown in yolk bacterial conjunctivitis (4). It has even been suggested that sacs of embryonated chicken eggs and diluted in phosphate- blinding trachoma does not develop in the absence of buffered saline. Each eye was inoculated with 20 ,ul of a 103-2 bacterial infection (9). 50% egg lethal dose suspension of chlamydia. An animal model of trachoma has been developed in Three bacterial species were studied. Haemophilus aegyp- cynomolgus monkeys (8) with most of the important clinical tius (ATCC 1116) was obtained from the American Type and histological features of the human disease. A mixed Culture Collection, Rockville, Md. Two strains of strepto- papillary and follicular reaction develops in the tarsal con- mycin-resistant Haemophilus influenzae type B were exam- junctiva. This progresses to the production of typical tracho- ined: strain B Eag, an encapsulated invasive strain, and matous scarring. Corneal pannus, however, is not marked. strain S2, a nonencapsulated strain (5). These strains were The conjunctival response provides a particularly useful provided by R. Moxon, The Johns Hopkins Hospital, Balti- model for the study of human trachoma where blindness more, Md. The Haemophilus organisms were grown in brain usually results from the in-turning of eye lashes (trichiasis) heart infusion broth supplemented with Leviathal base and caused by conjunctival scarring. Trichiasis produces corneal prepared for inoculation as described by Moxon and Vaughn opacification and blindness. (5). Each eye was inoculated with 20 ,ul containing 2 x 107 Chronic trachoma is produced in this model by the repeat- organisms. Finally, a pure suspension of Streptococcus ed inoculation of the conjunctiva with Chlamydia trachoma- pneumoniae type 3 that had been isolated from a patient with tis (7) in the absence of appreciable bacterial infection. In conjunctivitis was used. This was provided by P. Charache, this report we present studies undertaken to examine the The Johns Hopkins Hospital, Baltimore, Md. Again, 20 ,ul effect of acute bacterial infection superimposed on chronic containing 2 x 107 organisms was inoculated into each eye. chlamydial conjunctivitis in an animal model of trachoma. MATERIALS AND METHODS RESULTS Our standard examination protocol was followed (7, 8). H. aegyptius was inoculated once into both eyes of three Young, adult, colony-raised cynomolgus monkeys were groups of monkeys. The first group of five monkeys had used. The clinical response of each eye was graded for a experimental "active trachoma" and was receiving weekly number of individual signs using a slit-lamp. The individual ocular inoculations of chlamydia. The second group of four signs were then combined to give indices that quantify the monkeys had "old trachoma"; i.e., they had conjunctival clinical response: the follicular index, which characterizes scarring from previous follicular disease, although the week- the follicular response, and the inflammatory index, which ly inoculation of chlamydia had been stopped and the summarizes the nonspecific signs of inflammation (8). Tears follicular disease allowed to resolve. The third group was composed of four normal animals. Acute conjunctivitis de- * Corresponding author. veloped in the normal animals and resolved in 14 days. A 614 VOL. 44, 1984 BACTERIAL SECONDARY INFECTION IN TRACHOMA 615 x 4- NORMAL OLD TRACHOMA (H. aegyptius) (H. aegyptius) z 3. -J 2- z _i I-)I- w cr A, B: 0 o 0A x 4 Z 3. -J 4 < 2- ACTIVE TRACHOMA ACTIVE TRACHOMA* -J I. (H. aegyptius) (H. influenzae) I: I 1 n C- I r-r-T 1 O - C:' ouOJ I .- .- I -2 0 2 4 6 8 10 12 14 -2 0 2 4 6 8 10 12 14 16 DAYS DAYS FIG. 1. Clinical response to a single inoculation of Haemophilus organisms. (A) Four normal cynomolgus monkeys. (B) Four monkeys with old trachoma. (C) Four monkeys with active trachoma who continued to receive weekly ocular inoculations with C. trachomatis. Groups A, B, and C received a single inoculation with H. aegyptius ATCC 1116 in each eye on day zero. (D) Two monkeys with active trachoma who were inoculated with H. influenzae strains. The clinical response is shown as the mean follicular (0) and inflammatory (0) indices for each group. The frequency of positive (POS.) bacterial reisolation cultures is also shown. similar transient increase in nonspecific inflammation was that trachoma in the absence of bacterial conjunctivitis seen in both active and old trachoma groups (Fig. 1). Despite rarely leads to major visual loss (9) and that one of the main this clinical evidence of bacterial infection, the bacteria mechanisms of action of topical chemotherapy for severe could not be reisolated from the eye or nasopharynx of any endemic trachoma is the suppression of seasonal epidemics animal. Few Haemophilus organisms could be seen on Gram of acute bacterial conjunctivitis (6). stain, but the number of polymorphonuclear cells increased markedly in most monkeys 2 to 3 days after inoculation and 5 did not resolve until 8 to 14 days after inoculation. x A NORMAL 4- 0-O INFLAMMATORY INDEX H. influenza was inoculated once into both eyes of two w (S. pneumoniae) 0 z *-* FOLLICULAR INDEX monkeys. These organisms could be reisolated from the eyes 3, and the nasopharynx of these animals from the day after -i 4 inoculation until 4 weeks later. There was a transient in- 2- z crease in the inflammatory index (Fig. 1) but no real change J- in the follicular response. w Lastly, S. pneumoniae was inoculated into five monkeys with active trachoma and two normal monkeys. All monkeys 0 5 e 50- developed acute conjunctivitis, and organisms were reisolat- C.)M n n n n n ed from the nasopharynx of one of the normal monkeys and three of the with trachoma from 1 to 22 and monkeys day day 5. B from the eye of a normal monkey on day 2 and a monkey x w with trachoma on day 8 (Fig. 2). There was a small transient 4' increase in follicular index in monkeys with trachoma. z There was no change in tear or serum antichlamydial ACTIVE TRACHOMA antibody titers in any group. Chlamydial reisolation cultures -i (S. pneumonioe) remained negative in animals with active trachoma despite 1 continuing weekly chlamydial inoculation. No monkey de- w veloped new conjunctival scarring during the course of this 0'.- _, 50- study. Q- 0- DISCUSSION -2 0 2 4 6 8 10 12 14 16 18 20 22 24 Attention has been drawn to the importance of the interac- DAYS tion between chronic and acute bacterial infec- chlamydial FIG. 2. Clinical response in animals a single ocular have receiving tion in areas of endemic trachoma. Jones et al. (4) inoculation of S. pneumoniae at day zero. (A) Two normal mon- called this complex of chlamydial and bacterial infection keys. (B) Five monkeys with active trachoma. The clinical response "communicable ophthalmia," and the commonest organ- is shown as the mean follicular and inflammatory indices. The isms are the Haemophilus species, S. pneumoniae, and frequency of positive (POS.) streptococcal reisolation cultures is Moraxella sp. (2, 9). Indeed, some authors have suggested also shown. 616 TAYLOR ET AL. INFECT. IMMUN. Little attention has been given to examining this question mydia from the conjunctiva. However, our findings suggest in animal models of trachoma. The feline keratoconjunctivi- that even if bacterial infection could exacerbate the ocular tis agent is a member of Chlamydia psittaci and causes a inflammation in endemic trachoma, bacterial infection is not chronic follicular conjunctivitis in cats infected naturally or essential for the production of blinding or potentially blind- experimentally.
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