Vol. 60, No. 4

INFECTION AND IMMUNITY, Apr. 1992, p. 1358-1362

0019-9567/92/041358-05$02.00/0 Copyright X) 1992, American Society for Microbiology

Phagocytic Killing of Encapsulated and Microencapsulated Staphylococcus aureus by Human Polymorphonuclear Leukocytes SHILU XU,1 ROBERT D. ARBEIT,2 AND JEAN C. LEE`* Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, and Medical Service, Veterans Affairs Medical Center, Boston, Massachusetts 021302 Received 9 September 1991/Accepted 13 January 1992

Phagocytosis by human polymorphonuclear leukocytes (PMNs) is an important host defense against infections caused by Staphylococcus aureus. Using an in vitro assay, we compared the opsonic requirements for phagocytic killing of prototype strains of encapsulated (type 1) and microencapsulated (type 5 and type 8) S. aureus by human PMNs. More than 85% of broth-grown, logarithmic-phase type 5 and 8 S. aureus organisms were killed by PMNs incubated with fresh normal human, rabbit, or guinea pig serum with complement activity. Under similar conditions, the highly encapsulated type 1 strain was not killed. Both encapsulated and microencapsulated strains were opsonized for phagocytosis by heat-inactivated serum raised in rabbits to killed bacteria. Opsonization by homologous serum was required for phagocytosis of the type 1 strain. In contrast, microencapsulated type 5 and 8 S. aureus organisms were killed by heat-inactivated rabbit serum raised to type 5, type 8, or nonencapsulated isolates; this result suggested that antibodies to the capsule or to cell wall components other than the capsule could opsonize these organisms for phagocytosis. The specificity of the assay was confirmed with capsule type 5-specific monoclonal antibodies, which were opsonic only for the type 5 S. aureus isolate. These studies indicate that, unlike the highly encapsulated type 1 strain, broth-grown microencapsulated S. aureus strains do not resist opsonophagocytic killing in vitro by normal serum.

Capsular polysaccharides are produced by more than 90% of Staphylococcus aureus strains (11, 13, 22, 23). Eleven capsular serotypes have been defined by using capsulespecific monoclonal antibodies (MAbs) and polyclonal antibodies (23). Highly encapsulated mucoid strains (serotypes 1 and 2) are rarely isolated from clinical specimens (3, 17, 23), but they are virulent in animal models of staphylococcal infection (1, 6, 15, 16, 26). Strains belonging to microencapsulated serotypes 5 and 8 constitute -22 and -53%, respectively, of isolates (2, 3, 11, 13, 22, 23), but they have not been shown to be more virulent for animals than are nonencapsulated strains (1, 4). Karakawa et al. (12) reported that S. aureus microcapsules were antiphagocytic. Using an in vitro phagocytic assay with polyclonal rabbit sera and MAbs as opsonic sources, they showed that type 5 and 8 S. aureus strains were opsonized for phagocytosis only in the presence of specific capsular antibodies. Rabbit serum raised to a nonencapsulated strain contained antibodies to teichoic acid, but this serum was not opsonic for a type 8 strain. Furthermore, antisera to type 5 and 8 strains were not opsonic for S. aureus of the heterologous capsule type. These experiments suggest an important role for capsular antibodies in phagocytic clearance of microencapsulated S. aureus. However, Karakawa and colleagues used heat-inactivated sera in their assays, and complement therefore was not available in the assay mixture to opsonize the bacteria. In the current study, we examined and compared the opsonic requirements for phagocytic killing of strains SAl mucoid (capsule type 1), Reynolds (type 5), and Becker (type 8) in the presence and absence of capsular antibodies and complement activity. The highly encapsulated type 1 strain was killed by phagocytic cells after incubation with homologous antiserum. In contrast, the microencapsulated *

type 5 and type 8 strains were opsonized for phagocytosis by homologous antiserum or by normal serum with complement activity. Antisera to organisms of the heterologous capsule type or to a nontypeable strain were also opsonic for strains Reynolds and Becker; this result indicated that microencapsulated strains could be opsonized by antibodies to the capsular polysaccharide or to cell wall components.

MATERIALS AND METHODS Bacteria. The bacterial strains used in this study were maintained in skim milk at -70°C and are listed in Table 1. Strain SAl mucoid, a highly encapsulated type 1 S. aureus isolate, was described previously (18). Strains Reynolds and Becker, prototype microencapsulated isolates of type 5 and type 8, respectively, were described by Karakawa and Vann (13). Staphylococci were grown in Columbia broth (Difco Laboratories, Detroit, Mich.) modified by the addition of 0.1% D-glucose, 1% yeast extract, and 0.5% NaCl (13). Antibodies. Polyclonal antisera were raised in rabbits immunized three times per week for 3 weeks with formalinized or heat-killed (70°C for 1 h) suspensions of S. aureus. Immunoglobulin M MAb 17-20-1, specific for the type 5 S. aureus capsular polysaccharide, was described previously (20). Guinea pig serum (GPS; Pel-Freez Biologicals, Rogers, Ark.) was reconstituted and used as recommended by the manufacturer. Pooled normal human serum was obtained by venipuncture from two groups of four or five healthy adult volunteers. Normal rabbit serum was obtained from New Zealand White rabbits prior to immunization or from Cedarlane Laboratories (Hornby, Ontario, Canada). Sera were stored at -70°C or at -20°C after heat inactivation at 56°C for 30 min. Opsonophagocytic assay. Human polymorphonuclear leukocytes (PMNs) from healthy adult volunteers were separated by density gradient centrifugation of heparinized blood in Mono-Poly Resolving Medium (Flow Laboratories,

Corresponding author. 1358

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PHAGOCYTIC KILLING OF STAPHYLOCOCCI

TABLE 2. Opsonization of strains SAl mucoid, Reynolds, and Becker by GPS

TABLE 1. S. aureus strains used for this study

Capsule type

Source

5 Negative

W. Vann (13) 1

GPSa

8 Negative 1 Negative

W. Vann (13) 4 18 1

McLean, Va.). The cells were washed in 10 ml of minimal essential medium (GIBCO Laboratories, Grand Island, N.Y.) containing 1% bovine serum albumin (Sigma Chemical Company, St. Louis, Mo.; MEM-BSA) and were suspended to a concentration of 107 cells per ml. Cell viability, determined by trypan blue exclusion, was greater than 95%. S. aureus strains were cultivated at 37°C in 10 ml of modified Columbia broth with shaking to an A650 of 0.4 and were diluted to 2 x 107 CFU/ml of MEM-BSA before use. The opsonophagocytic killing assay was similar to that described by Karakawa et al. (12). Unless otherwise stated, the assay was performed in polypropylene microcentrifuge tubes (National Scientific Supply Co., Inc., San Rafael, Calif.) containing the following components: 5 x 106 PMNs per 0.5 ml, serum (0.1 ml), and -2 x 106 CFU of S. aureus per 0.1 ml. Control tubes contained S. aureus and each of the other components of the assay alone or in combination. The total volume of each tube was brought to 1 ml with the diluent MEM-BSA. For experiments utilizing MAbs, the volume of each reagent was half that used in the standard assay, although the ratios of the assay components remained the same. The tubes were rotated end over end at 37°C, and the number of CFU per milliliter was determined at 0, 60, and 120 min by the plating of duplicate 100-,ul aliquots of the diluted suspensions onto tryptic soy agar plates. Percent killing was calculated as follows: 100 x [1 (CFU remaining after incubation/CFU at time zero)]. All data presented are the means of at least three independent experiments.

A1:10 A1:25

Strain

Reynolds JL240 Becker JL252 SAl mucoid NT857

Marker

None Reynolds (EMSa) None Becker::Tn551 None None

a EMS, ethyl methanesulfonate.

-

RESULTS

Opsonophagocytic killing of type 1, 5, and 8 S. aureus organisms in the presence of GPS. To determine whether microencapsulated type 5 and 8 S. aureus organisms could be killed by PMNs in fresh serum containing low levels of antibodies, we used GPS as an opsonic source in the phagocytic assay. As shown in Table 2, the highly encapsulated type 1 strain SAl mucoid was not killed by phagocytosis in the presence of GPS. In contrast, microencapsulated strains of S. aureus (types 5 and 8) were phagocytosed and killed by PMNs in GPS with complement activity, even after the serum was diluted 50-fold. GPS was only poorly opsonic for strains Reynolds and Becker after being heated at 56°C for 30 min. Opsonization of strains SAl mucoid, Reynolds, and Becker by normal serum. Like fresh GPS, fresh normal human or rabbit serum was not opsonic for strain SAl mucoid (Table 3). Heated or unheated human serum promoted phagocytosis of strains Reynolds and Becker, a finding consistent with previous reports that healthy humans have antibodies to microencapsulated strains of S. aureus (2, 5). Fresh normal

1359

% Killing of strain:

SAl mucoid

Reynolds

Becker

60 min

120 min

60 min

120 min

60 min

120 min

N 1:10 1:25 1:50 1:100 1:200

0 0 0 0 0 0

0 0 0 0 0 0

88 97 96 90 51 3

85 97 95 91 54 8

87 92 91 84 43 0

92 92 87 86 65 0

AN

0 0 0 0 0

0 0 0 0 0

44

56 45 18 0

22 44 45 0 0

20 36

28

6 4 0

0 0 0

A1:50 A1:100 a

19

GPS, GPS diluted in MEM-BSA. N, neat; A, heat inactivated at 56°C for

30 min.

(preimmune) rabbit serum was opsonic for the microencapsulated strains Reynolds and Becker, presumably because of opsonization of the staphylococci by C3b. Heat-inactivated normal rabbit serum was poorly opsonic, indicating that rabbits, like guinea pigs, probably have little preexisting antibody to S. aureus. Opsonophagocytic killing of S. aureus by immune rabbit serum. To compare the killing of type 1, 5, and 8 S. aureus organisms by phagocytes in the presence of immune serum, we opsonized the bacteria with heat-inactivated rabbit antiTABLE 3. Opsonophagocytic killing of S. aureus by human PMNs in the presence of normal serum % Killing at:

Strain and serum (%)a

60 min

120 min

0 0 0 0 0

0 0 0 0 0

0 98 98 87 75 96 80 38 29

0 97 98 86 78 95 92 26 11

0 99 98 59 75 97 81

0 99 98 75 83 96 80 0 0

SAl mucoid None NHS (10) NHS (1) NRS (10) NRS (1)

Reynolds None NHS (10) NHS (1) ANHS (10) ANHS (1) NRS (10) NRS (1) ANRS (10) ANRS (1) Becker None NHS (10) NHS (1) ANHS (10) ANHS (1) NRS (10) NRS (1) ANRS (10)

ANRS (1)

14 6

a NHS, pooled normal human serum; NRS, normal rabbit serum; inactivated at 56°C for 30 min.

A, heat

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INFECT. IMMUN.

XU ET AL.

100

A. SAI Mucoid

Antiserum 857 (NT) + C Becker (8) + C d Reynolds (5) + C None JL252 (NT) + C'

A0

TABLE 4. Opsonization of strains Reynolds and Becker by MAb 17-20-1 (50 pug)a % Killing of strain:

MAb

GPSb

17-20-1 17-20-1 None

+

Reynolds

Becker

E

k-

SAI mucoid(1)

.1

SAl mucoid + C

60 Time (min)

a

120 min

60 min

120 min

73 0 0

76 0 0

0 0 0

15 0 0

a Overnight modified Columbia broth cultures of S. aureus were diluted in MEM-BSA and preincubated with MAb 17-20-1 for 1.5 to 2 h. The remaining components of the assay (PMNs, GPS, and MEM-BSA) were added, and the assay was performed as before. b GPS, GPS diluted 1:150.

S.

z

+

60 min

120

_

1oo1 B. Reynolds

No serum

10,

IN.

U-

u

I.E

Antiserum JL252 (NT) Reynolds(S)

-

Becker

(R)

-7n N 1]

60 Time (min)

120

INo serum

L.

2t 20

Antiserum JL240 (NT) Becker (8) JL252

(NT)

Rcynolds (5)

60

Time (min)

120

FIG. 1. Opsonophagocytic killing of type 1 strain SAl mucoid (A), type 5 strain Reynolds (B), and type 8 strain Becker (C) by human PMNs in the presence of 1% heat-inactivated rabbit serum raised to the strains indicated. Strain SAl mucoid was not killed after opsonization with heterologous sera in the presence or absence of undiluted GPS (C'). NT, nontypeable.

sera to killed bacteria. The data in Fig. 1 indicate that both encapsulated and microencapsulated strains were opsonized for phagocytosis by rabbit serum raised to the homologous strain. Although killing of strain SAl mucoid was evident after opsonization by homologous antiserum, the percentage of bacteria killed was higher when complement (provided by GPS) was included in the assay. Rabbit sera raised to heterologous strains were not opsonic for the type 1 isolate, even in the presence of complement. The microencapsulated strains Reynolds and Becker were killed by phagocytosis in the presence of heat-inactivated serum to type 5, type 8, or nonencapsulated isolates. This result suggested that these strains could be opsonized by antibodies directed either toward the capsule or toward noncapsular cell wall-associated antigens.

Opsonization of strains Reynolds and Becker by MAb 17-20-1. Normal sera contain antibodies to peptidoglycan and teichoic acid (8, 24); we therefore used a MAb (17-20-1) reactive with the type 5 capsular polysaccharide (20) to show type-specific killing of S. aureus by human PMNs. Because PMNs do not have Fc receptors for immunoglobulin M, MAb 17-20-1 alone was not opsonic for S. aureus (Table 4). Therefore, we added a complement source (GPS) to the assay at a dilution (1:150) that was not opsonic in the absence of added antibody. Even in the presence of complement, however, logarithmic-phase cells of strain Reynolds were killed poorly by PMNs and MAb 17-20-1. We observed -50% killing of logarithmic-phase Reynolds cells (opsonized with MAb and GPS) after 60 min, but the number of CFU per milliliter rose to the starting inoculum level by 120 min (no killing). The total numbers of logarithmic-phase S. aureus increased -10-fold during the 2-h assay incubation period (Fig. 1), and opsonophagocytosis in the presence of MAbs was apparently not sufficient to kill these rapidly multiplying cells. When polyclonal antiserum was used to opsonize microencapsulated S. aureus, we observed no differences in the phagocytic killing of logarithmic- and stationary-phase cells (30). Therefore, we preincubated a stationary-phase culture of strain Reynolds for 1.5 to 2 h with MAb 17-20-1 before adding PMNs and GPS to the opsonophagocytic assay. Under these conditions, -75% of Reynolds cells were phagocytosed and killed (Table 4). Under similar conditions of incubation with MAb 17-20-1, Becker cells were not killed by phagocytosis. Neither isolate was killed by PMNs and GPS (diluted 1:150) in the absence of added antibody. Thus, phagocytic killing of microencapsulated S. aureus by PMNs was type specific if MAb 17-20-1 was used to opsonize the organisms. DISCUSSION The biological properties of highly encapsulated S. aureus strains have been well characterized (14, 16, 19, 21, 26, 27). Heavily encapsulated strains (serotypes 1 and 2) are rarely encountered (3, 23) but are virulent in animal models of staphylococcal infection (6, 15, 16, 27) and are highly resistant to phagocytosis by PMNs (14, 16, 19, 21, 27, 28). The mechanism by which the S. aureus type 1 capsule is antiphagocytic was elucidated by Wilkinson et al. (27, 29) and Verbrugh and colleagues (25), who showed that the capsule shields C3b molecules deposited on the cell wall layer, making them inaccessible to receptors on the membrane of the PMN.

VOL. 60, 1992

Microencapsulated S. aureus strains have not been so well studied. Karakawa et al. (12) reported that microencapsulated type 5 and 8 isolates, like highly encapsulated S. aureus, were more resistant to phagocytosis than strains lacking capsules. In contrast, we showed that a microencapsulated mutant derived from a type 1 strain was not more resistant to phagocytosis than an isogenic, nonencapsulated mutant (16). Furthermore, in animal models of staphylococcal infection, we found no evidence that S. aureus microcapsules enhanced staphylococcal virulence (1, 4, 16). Similarly, epidemiologic studies have not found an association between capsule type and virulence, since type 5 and type 8 microcapsules are widely prevalent among S. aureus isolates from both pathologic and commensal sources. To clarify the role that these polysaccharides play in the host-parasite interaction, we compared the opsonic requirements of a highly encapsulated type 1 strain with those of microencapsulated type 5 and type 8 strains for phagocytosis by human PMNs in an vitro killing assay. When unheated GPS was used as an opsonic source in the phagocytic assay, the highly encapsulated type 1 strain SAl mucoid was resistant to phagocytosis. This observation agrees with previous reports (21, 27-29) suggesting that C3b molecules deposited on type 1 S. aureus are masked by the capsule and are inaccessible for recognition by phagocytes. In contrast, the microencapsulated strains Reynolds and Becker were opsonized for phagocytosis by PMNs in GPS with complement activity, even after the serum was diluted 50-fold. The microcapsule is apparently unable to impede sterically the interaction between cell wall-associated C3b and leukocyte membrane receptors for C3b. Strain SAl mucoid was killed by phagocytosis only after incubation with homologous rabbit antiserum. In previous work, we reported that both mouse anticapsular antibodies and complement were needed to opsonize SAl mucoid cells for phagocytosis (16). Differences in type 1 capsular-antibody levels between immune mouse serum (titer, -103) and immune rabbit serum (titer, -105) may explain this discrepancy. Strains Reynolds and Becker, but not strain SAl mucoid, were phagocytosed after opsonization by normal human serum, even if the serum was heat inactivated. This result is consistent with previous reports showing that healthy humans have antibodies to S. aureus surface antigens (2, 5, 8, 24). Likewise, type 5 and 8 microencapsulated S. aureus organisms were opsonized for phagocytosis by heat-inactivated serum raised in rabbits to homologous, heterologous, or nonencapsulated staphylococci. These results, which indicate that strains Reynolds and Becker can be opsonized by antibodies directed to either capsular or noncapsular cell wall determinants, conflict with those of Karakawa et al. (12). Discrepancies between data obtained from the two laboratories are difficult to explain. Our experiments were performed with the prototype isolates Reynolds and Becker, whereas Karakawa et al. used strain Becker as well as other microencapsulated strains of S. aureus. Although our MAb data showing type specificity are in agreement with the findings of Karakawa et al., the latter authors were able to opsonize the bacteria with immunoglobulin M MAbs in the absence of complement (12). Only additional studies with these and other strains are likely to resolve the differences. Although most strains of S. aureus express microcapsules of only two antigenic specificities (types 5 and 8), the role that the microcapsule plays in the host-pathogen interaction remains uncertain. Our experiments suggest that S. aureus microcapsules are not antiphagocytic, and this idea is con-

PHAGOCYTIC KILLING OF STAPHYLOCOCCI

1361

sistent with the fact that microencapsulated strains of S. aureus do not share other biological properties associated with highly encapsulated staphylococci. Highly encapsulated strains of S. aureus not only resist opsonophagocytic killing in normal serum but also are clumping factor negative, phage nontypeable, diffuse in serum soft agar, and mucoid on agar plates. More important, encapsulated S. aureus is virulent in animal models of staphylococcal infection (6, 15, 16, 26). Microencapsulated strains lack these characteristics. Nonetheless, S. aureus microcapsules may have other unrecognized functions, such as adherence to mammalian extracellular matrix proteins. They may also be important targets for immunization, since capsular antibodies are opsonic. Recently, Fattom et al. (7) synthesized a vaccine composed of type 5 or type 8 capsular polysaccharides conjugated to Pseudomonas aeruginosa exotoxin A. Both type 5 and type 8 conjugate vaccines elicited a rise in antibodies to the staphylococcal capsule in mice, and antibodies to the type 5 conjugate were opsonic for type 5 S. aureus. The authors proposed to use the vaccines in clinical studies designed to actively or passively immunize patients at risk for S. aureus bacteremia. Although our experiments indicate that antibodies to noncapsular cell wall determinants are also opsonic for microencapsulated S. aureus in vitro, these antibodies have not been shown to be protective (8-10, 24). Whether antibodies to type 5 and type 8 polysaccharides are important in immunity to S. aureus infections is a question that deserves attention in the future. ACKNOWLEDGMENTS This work was supported by Public Health Service grants AI23244 and AI-29040 from the National Institute of Allergy and Infectious Diseases to J.C.L. and by a Merit Review grant from the Research Service of the Department of Veterans Affairs to R.D.A.

REFERENCES 1. Albus, A., R. D. Arbeit, and J. C. Lee. 1991. Virulence of Staphylococcus aureus mutants altered in type 5 capsule production. Infect. Immun. 59:1008-1014. 2. Albus, A., J. M. Fournier, C. Wolz, A. Boutonnier, M. Ranke, N. Hoiby, H. Hochkeppel, and G. Doring. 1988. Staphylococcus aureus capsular types and antibody response to lung infection in patients with cystic fibrosis. J. Clin. Microbiol. 26:2505-2509. 3. Arbeit, R. D., W. W. Karakawa, W. F. Vann, and J. B. Robbins. 1984. Predominance of two newly described capsular polysaccharide types among clinical isolates of Staphylococcus aureus. Diagn. Microbiol. Infect. Dis. 2:85-91. 4. Baddour, L. M., C. Lowrance, A. Albus, J. H. Lowrance, S. K. Anderson, and J. C. Lee. Staphylococcus aureus microcapsule expression attenuates bacterial virulence in a rat model of experimental endocarditis. J. Infect. Dis., in press. 5. Christensson, B., A. Boutonnier, U. Ryding, and J. M. Fournier. 1990. Diagnosing Staphylococcus aureus endocarditis by detecting antibodies against S. aureus capsular polysaccharide type 5 and 8. J. Infect. Dis. 163:530-533. 6. Cohn, Z. 1962. Determinants of infection in the peritoneal cavity. 1. Response to and fate of Staphylococcus aureus and Staphylococcus albus in the mouse. Yale J. Biol. Med. 35:1228. 7. Fattom, A., R. Schneerson, S. C. Szu, W. F. Vann, J. Shiloach, W. W. Karakawa, and J. B. Robbins. 1990. Synthesis and immunologic properties in mice of vaccines composed of Staphylococcus aureus type 5 and type 8 capsular polysaccharides conjugated to Pseudomonas aeruginosa exotoxin A. Infect. Immun. 58:2367-2374. 8. Ganstrom, M., I. Julandar, S.-A. Hedstrom, and R. Mollby. 1983. Enzyme-linked immunosorbent assay for antibodies

1362

9.

10. 11.

12.

13. 14.

15. 16.

17.

18.

19.

INFECT. IMMUN.

XU ET AL.

against teichoic acid in patients with staphylococcal infections. J. Clin. Microbiol. 17:640-646. Greenberg, D. P., A. S. Bayer, D. Turner, and J. I. Ward. 1990. Antibody responses to protein A in patients with Staphylococcus aureus bacteremia and endocarditis. J. Clin. Microbiol. 28:458-462. Greenberg, D. P., J. I. Ward, and A. S. Bayer. 1987. Influence of Staphylococcus aureus antibody on experimental endocarditis in rabbits. Infect. Immun. 55:3030-3034. Hochkeppel, H. K., D. G. Braun, W. Vischer, A. Imm, S. Sutter, U. Staeubli, R. Guggenheim, E. L. Kaplan, A. Boutonnier, and J. M. Fournier. 1987. Serotyping and electron microscopy studies of Staphylococcus aureus clinical isolates with monoclonal antibodies to capsular polysaccharide types 5 and 8. J. Clin. Microbiol. 25:526-530. Karakawa, W. W., A. Sutton, R. Schneerson, A. Karpas, and W. F. Vann. 1988. Capsular antibodies induce type-specific phagocytosis of capsulated Staphylococcus aureus by human polymorphonuclear leukocytes. Infect. Immun. 56:1090-1095. Karakawa, W. W., and W. Vann. 1982. Capsular polysaccharides of Staphylococcus aureus. Semin. Infect. Dis. 4:285-293. Karakawa, W. W., D. A. Young, and J. A. Kane. 1978. Structural analysis of the cellular constituents of a fresh clinical isolate of Staphylococcus aureus, and their role in the interaction between the organisms and polymorphonuclear leukocytes in the presence of serum factors. Infect. Immun. 21:496-505. Koenig, M. 1962. Factors relating to the virulence of staphylococci. I. Comparative studies on two colonial variants. Yale J. Biol. Med. 34:537-559. Lee, J. C., M. J. Betley, C. A. Hopkins, N. E. Perez, and G. B. Pier. 1987. Virulence studies, in mice, of transposon-induced mutants of Staphylococcus aureus differing in capsule size. J. Infect. Dis. 156:741-750. Lee, J. C., M. J. Liu, J. Parsonnet, and R. D. Arbeit. 1990. Expression of type-8 capsular polysaccharide and production of toxic shock syndrome toxin-1 are associated among vaginal isolates of Staphylococcus aureus. J. Clin. Microbiol. 28:26122615. Lee, J. C., F. Michon, N. E. Perez, C. A. Hopkins, and G. B. Pier. 1987. Chemical characterization and immunogenicity of capsular polysaccharide isolated from mucoid Staphylococcus aureus. Infect. Immun. 55:2191-2197. Melly, M., L. Duke, D.-F. Liau, and J. Hash. 1974. Biological

20.

21.

22.

23.

24.

25.

26. 27.

28.

29.

30.

properties of the encapsulated Staphylococcus aureus M. Infect. Immun. 10:389-397. Nelles, M. J., C. A. Niswander, W. W. Karakawa, W. F. Vann, and R. D. Arbeit. 1985. Reactivity of type-specific monoclonal antibodies with Staphylococcus aureus clinical isolates and purified capsular polysaccharide. Infect. Immun. 49:14-18. Peterson, P., B. Wilkinson, Y. Kim, D. Schmeling, and P. Quie. 1978. Influence of encapsulation on staphylococcal opsonization and phagocytosis by human polymorphonuclear leukocytes. Infect. Immun. 19:943-949. Poutrel, B., A. Boutonnier, L. Sutra, and J. M. Fournier. 1988. Prevalence of capsular polysaccharide types 5 and 8 among Staphylococcus aureus isolates from cow, goat, and ewe milk. J. Clin. Microbiol. 26:38-40. Sompolinsky, D., Z. Samra, W. W. Karakawa, W. F. Vann, R. Schneerson, and Z. Malik. 1985. Encapsulation and capsular types in isolates of Staphylococcus aureus from different sources and relationship to phage types. J. Clin. Microbiol. 22:828-834. Verbrugh, H., R. Peters, M. Rozenberg-Arska, P. Peterson, and J. Verhoef. 1981. Antibodies to cell wall peptidoglycan of Staphylococcus aureus in patients with serious staphylococcal infections. J. Infect. Dis. 144:1-9. Verbrugh, H. A., P. K. Peterson, B. Y. Nguyen, S. P. Sisson, and Y. Kim. 1982. Opsonization of encapsulated Staphylococcus aureus: the role of specific antibody and complement. J. Immunol. 129:1681-1687. Wiley, B., and N. Maverakis. 1974. Capsule production and virulence among strains of Staphylococcus aureus. Ann. N.Y. Acad. Sci. 236:221-232. Wilkinson, B. 1983. Staphylococcal capsules and slime, p. 481-523. In C. Easmon and C. Adlam (ed.), Staphylococci and staphylococcal infections. Academic Press, London. Wilkinson, B. J., P. K. Peterson, and P. G. Quie. 1979. Cryptic peptidoglycan and the antiphagocytic effect of the Staphylococcus aureus capsule: model for the antiphagocytic effect of bacterial cell surface polymers. Infect. Immun. 23:502-508. Wilkinson, B. J., S. P. Sisson, Y. Kim, and P. K. Peterson. 1979. Localization of the third component of complement on the cell wall of encapsulated Staphylococcus aureus M: implications for the mechanism of resistance to phagocytosis. Infect. Immun. 26:1159-1163. Xu, S., R. D. Arbeit, and J. C. Lee. Unpublished data.

Phagocytic killing of encapsulated and microencapsulated Staphylococcus aureus by human polymorphonuclear leukocytes.

Phagocytosis by human polymorphonuclear leukocytes (PMNs) is an important host defense against infections caused by Staphylococcus aureus. Using an in...
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