Experimental bacterial keratitis in neutropenic guinea pigs: polymorphonuclear leukocytes in corneal host defense

Abstract

Quantitative techniques were used to determine the relative concentrations of viable bacteria and polymorphonuclear leukocytes (PMNs) in the corneas of neutropenic and non-neutropenic guinea pigs with experimental bacterial keratitis induced with three strains of Pseudomonas aeruginosa. Neutropenia was produced by whole-body X-irradiation 1 week before infection. Significantly greater numbers of bacteria were present in the corneas of neutropenic animals 48 h after infection than were present in the corneas of non-neutropenic animals. The same was true 24 and 48 h after infecting animals with Staphylococcus aureus. Examination of histological sections showed that fewer PMNs were present in the corneas of infected neutropenic animals than in the corneas of infected nonneutropenic animals. Radiolabeling of PMNs confirmed a significant reduction in PMN concentration in the corneas of infected neutropenic animals. Tears and the corneal epithelium appear to be the most important elements protecting the cornea against local invasion by bacteria. However, once bacterial keratitis is established, PMNs play a role in limiting bacterial multiplication.Little is known regarding the role of the polymorphonuclear leukocyte (PMN) in the defense of the cornea against bacterial infection. Intracorneal administration of bacterial or chemical agents causes the accumulation of many PMNs at the site of injection (8). Mice made neutropenic with cyclophosphamide and then infected intracorneally with Pseudomonas aeruginosa develop rapidly progressive ocular infections and are more likely to die of sepsis than are non-neutropenic animals similarly challenged (6). Corticosteroids inhibit the entry of PMNs into inflammatory corneal foci (8). Patients receiving such agents may be more susceptible to bacterial or fungal corneal infection (4).The effect of neutropenia on the progress of bacterial keratitis or on the inflammatory response in the cornea has not been quantitatively assessed. By using analytic methods which allowed measurement of the ingress of PMNs into experimentally infected corneas and assay of the number of viable bacteria present, we demonstrated that PMNs play a major role in the response of the cornea to bacterial infection and that neutropenia alters that inflammatory response.(This paper was presented in part at the 18th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, Ga., [1][2][3][4] October 1978.) MATERIALS AND METHODS Induction of neutropenia. Male Hartley strain guinea pigs weighing about 300 g received 450 rads over a 2-min period from a 280 kV X-ray unit (Picker X-ray Corp., Pittsburgh, Pa.). The half-value layer was 1.0 mm copper. The target distance was 43 cm and the field size was 35 cm in diameter. The animals were lightly anesthetized and placed in a plexiglass holder; their eyes were shielded during irradiation with lead strips. Their position were reversed after one-half dose. White blood cell and differential counts on peripheral blood were performed prior to and daily for 9 da...

Gene expression of pro‐inflammatory cytokines and chemokines in mouse eye infected with Pseudomonas aeruginosa

“…4 Various studies indicate that the stimulated host responses may be more responsible for the further tissue damage than the invading pathogens. [2][3][4][5] Pseudomonas aeruginosa ocular clinical isolates exhibit three phenotypes: 6 (i) an invasive P. aeruginosa, which can invade epithelial cells; 7 (ii) a cytotoxic P. aeruginosa, which can cause epithelial cell cytotoxicity; 8 and (iii) a type of P. aeruginosa associated with contact lens induced acute red eye (CLARE) reaction. 9 The third type is neither cytotoxic nor invasive toward human corneal epithelial cells, 10 but can adhere to contact lenses.…”

Kinetics of serum, tear, and corneal antibody responses in resistant and susceptible mice intracorneally infected with Pseudomonas aeruginosa

“…These results suggest that ocular IgA was made locally, whereas most ocular IgG may have originated from the serum, with some possible local synthesis. These immunological results indicate that DBA/2 and C57BL/6 mice respond differently to corneal challenge with P. aeruginosa.Pseudomonas aeruginosa is an opportunistic pathogen which causes severe corneal infections in humans and experimental animals (3,6,11,32,33). Previous experimental studies from our laboratory have indicated that DBA/2 mice can spontaneously restore corneal clarity within a few weeks after infection; they are therefore classified as naturally resistant (2, 12).…”

“…Pseudomonas aeruginosa is an opportunistic pathogen which causes severe corneal infections in humans and experimental animals (3,6,11,32,33). Previous experimental studies from our laboratory have indicated that DBA/2 mice can spontaneously restore corneal clarity within a few weeks after infection; they are therefore classified as naturally resistant (2,12).…”

Serum antibody response to Pseudomonas aeruginosa antigens during corneal infection

“…The kinetics of the humoral response in susceptible C57BL/6J mice-were similar to those in resistant DBA/2J mice, although the magnitude of the response varied according to the antigen tested. These results indicate that LPS, exotoxin A, PLC, and flagella are present or produced in amounts that are immunogenic during corneal infection by P. aeruginosa 19660 in the mouse strains tested.Pseudomonas aeruginosa is an opportunistic pathogen which causes severe corneal infections in humans and experimental animals (6,8,14,37,38). The infection is usually preceded by corneal trauma.…”

“…Pseudomonas aeruginosa is an opportunistic pathogen which causes severe corneal infections in humans and experimental animals (6,8,14,37,38). The infection is usually preceded by corneal trauma.…”