Colonisation of the upper respiratory tract of mice with group B streptococci type III with reference to the R-protein.

Nine strains of group B streptococci type III, five with R-protein (R+) and four without (R-) were tested for capacity to colonise the upper respiratory tract in mice and to adhere to human buccal cells. In the mouse model, 80-microliter inocula of dilutions of overnight cultures of the strains in Todd Hewitt broth were placed in the external nares under light ether anaesthesia. A pilot experiment demonstrated that it was reasonable to study the throat colonisation 2 and 4 days after inoculation. Groups of 18-20 mice were then given inocula containing 8 X 10(6) cfu/ml of five R+ and four R- strains. At day 4, significantly more mice were colonised with type III, R+ strains (73% of the animals) than with type III, R- strains (44%) (p less than 0.01). In adherence experiments with human buccal cells, no difference was found between the R+ and R- strains. The results indicated that the higher colonisation rate among R+ strains was mediated by mechanisms other than adherence.

Chlorhexidine for prevention of neonatal colonization with group B streptococci. I. In vitro effect of chlorhexidine on group B streptococci.

Forty-three strains of group B streptococci (GBS) of types Ia, Ib, II and III were tested for susceptibility to chlorhexidine in concentrations ranging from 256 to 0.25 mg/l using the agar and tube dilution methods. The strains showed minimum inhibitory concentration (MIC) values ranging from 0.5 to 1 mg/l. Serum added to the test medium (50%) increased the MIC values to 4-8 mg/l, while amniotic fluid (50%) had almost no effect, increasing the values to 1-2 mg/l. The minimum bactericidal concentration (MBC) ranged from 1 to 5 mg/l. The killing kinetics were related to the concentration of chlorhexidine and the length of exposure. For example, at a concentration of 63 mg/l, 7 h were required for a bactericidal effect in broth, as compared to 1 h at 500 mg/l chlorhexidine. 200 mg/l chlordexidine had no effect on the adherence of two GBS strains to vaginal epithelial cells, and no effect on the phagocytosis of GBS with mouse peritoneal macrophages.

Retropharyngeal abscess: recent trends.

Retropharyngeal abscess (RPA) is relatively rare today. A study of 17 cases of RPA treated at our hospital in the past 10 years showed a shift in the disease from children below 6 years of age (41%) to older children and adults (58%). Upper respiratory tract infection (URTI) was found to be the commonest (52%) aetiological predisposing factor in all age groups. Other aetiological factors were septicaemia (11%) in children below the age of 6 years and trauma due to foreign body (35%) in the older children and adult age groups. Klebsiella, Staphylococcus and Streptococcus were the commonest species of microorganisms grown from pus. The changing clinical trends, microbiology, choice of antibiotics, usefulness of radiology, and complications of this potentially fatal illness are discussed.

Tuberculoid granulomatous lesion of the pharynx--review of the literature.

Pharyngeal involvement in tuberculosis is rare and is usually secondary to pulmonary tuberculosis. We report a very rare case of chronic granulomatous pharyngitis, which later turned out to be due to primary tuberculosis of the pharynx. The clinical presentation, diagnosis, treatment and complications of this rare clinical entity are presented.

Hemagglutination activities of group B, C, D, and G streptococci: demonstration of novel sugar-specific cell-binding activities in Streptococcus suis.

A total of 378 streptococcal isolates of Lancefield groups B, C, D and G were tested for their ability to hemagglutinate untreated, sialidase-treated, and endo-beta-galactosidase-treated human erythrocytes. Of the 43 strains showing positive hemagglutination, 9 were inhibitable with neutral monosaccharides. Four strains were inhibited with galactose and N-acetylgalactosamine, whereas five were inhibited with galactose only. A third, sialic acid-specific adhesion activity was suggested for two additional strains on the basis of their agglutination of native and endo-beta-galactosidase-treated but not sialidase-treated erythrocytes. All the sugar-specific agglutination activities detected were confined to Streptococcus suis strains of group D streptococci, whereas streptococci of other groups did not exhibit these types of hemagglutination activities. The adhesins were sensitive to proteases and heat treatment, which indicates that they were proteins. The hemagglutinating isolates of S. suis originated from pig brain and lung, human brain, and the tonsils of healthy pigs. No clear correlation with a particular serotype was observed. These results demonstrate the occurrence of unique sugar-specific adherence activities in S. suis, an important pig pathogen with occasional human pathogenicity.

Repeated passage of freshly isolated group A streptococci on blood agar. I. Effect on M protein, opacity factor and IgG Fc-receptor activity.

Seventy-six strains, 20 T-type 1, 20 T-type 2, 18 T-type 4 and 18 T-type 12 group A streptococci were isolated from throat cultures and subjected to 25 serial passages on blood agar. A single "glossy" colony was selected from each passage in order to diminish the M protein content of the strains. In accordance with previous results, the M protein synthesis, as estimated by an electro-immuno assay diminished in the T1 strains, in mean from 23.8 to 15.5% of a reference M protein preparation (p less than 0.01). Opacity factor (OF)-production was used as a measure for M protein in the T-type 2, the T-type 4 and the OF-positive T-type 12 strains. OF-excretion decreased significantly in the T-types 2 and decreased, though not significantly in the T-type 12 strains but increased (unexpectedly) in the T-type 4 isolates during subculture. However, irrespective of the changes in M protein/OF production these types all increased significantly in capacity to bind radiolabelled IgG via the Fc-fragment. It is known that streptococci isolated during convalescence resemble subcultured strains; it is suggested that IgG Fc-receptors are important for protection of the streptococci against phagocytosis in the asymptomatic carrier state.

Repeated passage of freshly isolated group A streptococci on blood agar. II. Effect on adherence capacity.

Group A streptococcal strains (three T-type 1, two T-type 2 and three T-type 4), freshly isolated from throat cultures, were subjected to 25 serial passages on blood agar. All strains changed their M protein production and/or opacity factor (OF)-activity during the passages. The capacity of each strain to adhere to a pool of buccal cells from six healthy individuals was studied both before and after passage. Five of six strains with decreased OF-activity/M protein production diminished significantly in adherence capacity, whereas one of two strains with increasing OF-activity adhered better to the epithelial cells. The results are discussed in relation to the clinical view of asymptomatic carriers of group A streptococci.

Binding of aggregated human serum albumin to M12 and some other types of group A streptococci.

In radiobinding tests many group A, C and G streptococci react with IgG and IgA, irrespective of the antigen-combining sites, as well as with various other serum proteins, e.g. human serum albumin (HSA). The present study demonstrated that glutaraldehyde-aggregated, radiolabelled HSA (a*HSA), in comparison to monomeric HSA, binds more avidly to streptococci. Of group A streptococci, strains representing types M6, M12, M18, M46, M55 and M57 displayed pronounced binding of a*HSA whereas a number of other serotypes were non-reactive. The streptococcal sites involved proved to be relatively heat-resistant and highly sensitive to trypsin treatment. Human fibrinogen counteracted the binding of a*HSA. The uptake by M12 was inhibited strongly by rabbit antiserum raised against M12, whereas other antisera were less active. The results suggest that the bacterial structure binding a*HSA is a protein and that, in at least one serotype, M12, the binding occurs to the M-protein.

Protective effect of heterologous gram-positive vaccine against lethal upper respiratory tract infection with type M50 group A streptococci in mice.

Type M50 group A streptococci are exceptional for their virulence in mice. However, intranasal (i.n.) vaccination with heat-killed group A streptococci, either of type M50 or M55, or an M12 strain deficient in M-protein, protected mice against i.n. challenge with M50 streptococci (82, 88 and 83% survival, respectively). Significant resistance against M50 streptococci was also noted by i.n. application of heat-killed Lactobacillus fermenti (81% survival) as well as two strains of pneumococci (50 and 79% survival). In contrast, no protective effect was obtained using heat-killed trypsin-treated M55 streptococci. Nor did vaccination with Escherichia coli and Pseudomonas aeruginosa induce protection against type M50. Thus, M protein was not required for immunity against type M50. The results call for a revision of the hitherto accepted view that M proteins are the only candidates for mucosal vaccines against group A streptococci.

Induction of local immunity to group A streptococci type M50 in mice by non-type-specific mechanisms.

The possibility of inducing immunity in the upper respiratory tract against type M50 group A streptococci was studied in mice. The M50 type exhibited an LD100 a of 10(5) colony-forming units (CFU) when administered intranasally (i.n.), and of 10(7) CFU when introduced intraperitoneally (i.p.). I.n. administered vaccines prepared from M types 12, 18, 30, 49, 50 and 55 were equally efficient in preventing lethal infection after i.n. challenge with type M50. Subcutaneous (s.c.) immunization with type 18 had no effect, whereas s.c. immunization with type 50 was effective against i.n. challenge with type 50. Neither with i.n. nor s.c., did vaccination with type 18 - in contrast to with type 50 - protect against i.p. challenge with type 50. The results strongly suggest that local immunity against M50 group A streptococci can be achieved using a non-type-specific mechanism. Once the local barrier had been overcome, protection against systemic infection was type-specific in accordance with classic concepts.

Effects of pneumococcal vaccination on tonsillo-pharyngitis and upper respiratory tract flora.

The effect of a 14-valent pneumococcal vaccine on upper respiratory tract infections and carriage of beta-haemolytic streptococci was studied in a double-blind prospective study of 405 children 0.5-5 years of age. In the children under 2 years of age at vaccination, the cases of acute tonsillitis were more frequent among the vaccinees than among the controls (p less than 0.01). In contrast, among the children over 2 years of age at vaccination, fewer episodes of acute tonsillitis were reported among the vaccinees than among the controls (p less than 0.01). In the older age group, the total rate of upper respiratory tract infections was also significantly reduced. Similarly, an increase in asymptomatic carriage of group A streptococci was registered in children vaccinated at 2-5 years of age (p less than 0.01). Inversely, the carriership of group C streptococci diminished among the vaccinated children (p less than 0.05). Some possible mechanisms underlying these unexpected findings, including non-specific mitogenic features and cross-protection due to antigenic similarities, were explored.