Role of gamma interferon in a neonatal mouse model of group B streptococcal disease.

The aim of this study was to assess the role of gamma interferon (IFN-gamma) in a neonatal mouse model of group B streptococcal (GBS) sepsis. IFN-gamma was produced by spleen cells at 24, 48, and 72 h after GBS challenge. Treatment with anti-IFN-gamma at 6 h before challenge totally abrogated the IFN-gamma response but did not affect survival. Subcutaneous administration of recombinant IFN-gamma (2,500 IU per pup) at 18 h after challenge resulted in increased survival time and reduced blood colony counts at 48 and 72 h. In vitro preincubation of neonatal whole blood with IFN-gamma before the addition of GBS resulted in significant restriction of bacterial growth. These data indicate that administration of recombinant IFN-gamma can partially restore impaired host defenses against GBS in neonatal mice. This cytokine may be useful for the treatment of neonatal infections.     

Prevention of group B streptococcal neonatal disease revisited. The DEVANI European project

The purpose of this paper was to present the current knowledge on the prevention of group B streptococcus (GBS) neonatal infections and the status of prevention policies in European countries and to present the DEVANI pan-European program, launched in 2008. The aim of this program was to assess the GBS neonatal infection burden in Europe, to design a new vaccine to immunize neonates against GBS infections, to improve the laboratory performance for the diagnosis of GBS colonization and infection, and to improve the methods for the typing of GBS strains. The current guidelines for GBS prevention in different countries were ascertained and a picture of the burden before and after the instauration of prevention policies has been drawn. After the issue of the Centers for Disease Control and Prevention (CDC) guidelines, many European countries have adopted universal screening for the GBS colonization of pregnant women and intrapartum prophylaxis to colonized mothers. Nevertheless, some European countries continue advocating the risk factor approach to GBS prevention. Most European countries have implemented policies to prevent GBS neonatal infections and the burden of the disease has decreased during the last several years. Nevertheless, further steps are necessary in order to develop new strategies of prevention, to improve microbiological techniques to detect GBS colonization and infection, and to coordinate the prevention policies in the EU.     

Prevention of early-onset neonatal group B streptococcal disease with selective intrapartum chemoprophylaxis

Most cases of neonatal group B streptococcal disease with early onset have an intrapartum pathogenesis. Attack rates are increased substantially in infants born to mothers with prenatal group B streptococcal colonization and various perinatal risk factors (premature labor, prolonged membrane rupture, or intrapartum fever). In a randomized controlled trial, we studied the effect of selective intrapartum prophylaxis with ampicillin in 160 such high-risk women. In infants born to mothers who received intravenous ampicillin during labor, as compared with controls who received no treatment, neonatal colonization with group B streptococci was present in 8 of 85 (9 percent) versus 40 of 79 (51 percent; P less than 0.001), colonization at multiple (greater than or equal to 3) sites was observed in 3 of 85 (4 percent) versus 24 of 79 (30 percent; P less than 0.001), and bacteremia occurred in none of 85 versus 5 of 79 (6 percent; P = 0.024). The side effects of ampicillin were limited to a single episode of urticaria in a mother who had no history of penicillin allergy. We conclude that intrapartum ampicillin prophylaxis in women with positive prenatal cultures for group B streptococci who have certain perinatal risk factors can prevent early-onset neonatal group B streptococcal disease.     

Type IV neonatal early-onset group B streptococcal disease in a United States hospital

Group B streptococcus (GBS) serotypes causing neonatal disease vary by geographic region. Surveillance at the Brigham and Women's Hospital in Boston, Massachusetts, revealed a case of neonatal early-onset sepsis caused by type IV GBS. Neonatal type IV disease occurs in the Middle East but has not recently been described in U.S. infants.     

Regulatory role of interleukin-10 in experimental group B streptococcal arthritis

Intravenous inoculation of CD-1 mice with 10(7) CFU of type IV group B Streptococcus (GBS) results in a high incidence of diffuse septic arthritis, associated with high levels of systemic and local production of interleukin-1beta (IL-1beta) and IL-6. In this study, the role of the anti-inflammatory cytokine IL-10 in the evolution of GBS systemic infection and arthritis was evaluated. IL-10 production was evident in sera and joints of GBS-infected mice. Neutralization of endogenous IL-10 by administration of anti-IL-10 antibodies (1 mg/mouse) at the time of infection resulted in worsening of articular lesions and 60% mortality associated with early sustained production of IL-6, IL-1beta, and tumor necrosis factor alpha (TNF-alpha). The effect of IL-10 supplementation was assessed by administering IL-10 (100, 200, or 400 ng/mouse) once a day for 5 days, starting 1 h after infection. Treatment with IL-10 had a beneficial effect on GBS arthritis, and there was a clear-cut dose dependence. The decrease in pathology was associated with a significant reduction in IL-6, IL-1beta, and TNF-alpha production. Histological findings showed limited periarticular inflammation and a few-cell influx in the articular cavity of IL-10-treated mice, confirming clinical observations. In conclusion, this study provides further information concerning the role of IL-10 in regulating the immune response and inflammation and calls attention to the potential therapeutic use of IL-10 in GBS arthritis.     

Interleukin-10 protects neonatal mice from lethal group B streptococcal infection.

We investigated the role of interleukin-10 (IL-10) in a neonatal mouse model of lethal group B streptococci (GBS) sepsis. Plasma IL-10 levels significantly increased at 24 and 48 h after GBS inoculation. Neutralization of IL-10 with specific antibodies had no effect on lethality. Administration of recombinant IL-10 at 20 or 4 h before challenge, but not at later times, resulted in decreased tumor necrosis factor alpha levels and improved survival. IL-10 could be potentially useful for the treatment of GBS sepsis.     

Detection of group B streptococcal antigen in early-onset and late-onset group B streptococcal disease with the Wellcogen Strep B latex agglutination test.

The Wellcogen Strep B latex agglutination test (Wellcome Diagnostics, Dartford, England) was evaluated as a method of detecting group B streptococcal antigen in urine, cerebrospinal fluid, and serum from neonates with early-onset (less than or equal to 7 days of age) and late-onset group B streptococcal disease. Urine was the best source of antigen, which was detected in 100% of six neonates with early-onset group B streptococcal disease who had urine available in the first 12 h of illness and in 88% of 17 group B streptococcus-infected neonates with urine available in the first 48 h of illness. Antigen was not detected in any samples from patients without group B streptococcal disease except in the urine of one patient with Proteus mirabilis meningitis. The Wellcogen Strep B latex test of the lot tested compares favorably with a noncommercially available latex agglutination test.     

Efficacy of a universal screening program for the prevention of neonatal group B streptococcal disease

Universal antepartum vaginal cultures for group B streptococcus (GBS) were initiated in a Spanish hospital in 1994 using Granada medium. Infants born to carriers were monitored closely, and blood, urine and mucocutaneous areas were cultured for GBS. Group B streptococcus was detected in 543 of 4,525 women (12 %). Of these, 454 gave birth vaginally, of whom 201 (44 %) received intrapartum ampicillin. Prophylaxis was not administered to 253 women (56 %). In this group, infants of 120 women were colonized and 1 case of neonatal GBS disease occurred. Using this protocol, most GBS carriers with risk factors received intrapartum prophylaxis. This protocol also led to early identification of colonized newborns.     

Application of the French guidelines for preventing neonatal group B streptococcal disease in a university hospital

This study evaluated the application of the French guidelines for prevention of neonatal group B streptococcus (GBS) infections. The prevalence of GBS vaginal carriage by pregnant women during the study period was 6%. Less than 50% of pregnant women testing positive for GBS were treated with at least two doses of antibiotics during labour, and most received only one dose or no antibiotics. In addition, several neonates were colonised or infected by GBS although their mothers were GBS-negative. These results are consistent with vaginal screening having a poor sensitivity, as suggested by the low prevalence of GBS carriage.     

The hemolytic and cytolytic activity of group B streptococcal hemolysin and its possible role in early onset group B streptococcal disease.

The in vitro and cytolytic properties of the hemolysin of group B streptococcus (GBS) were investigated using sheep erythrocytes and McCoy cells adapted for growth in a serum-deficient medium. The relationship between the hemolysin, various carrier molecules and phospholipids was examined. Starch-based carriers interfered with the inhibitory activity of phospholipids and solvents for the phospholipids reduced the activity of the hemolysin. These technical problems were resolved by use of an albumin-based carrier, a strain producing large amounts of hemolysin and sonication of the phospholipid. The hemolysin was cytolytic for McCoy cells and this activity and its hemolytic action on sheep erythrocytes were inhibited by a number of phospholipid components of surfactant. It is possible that GBS hemolysin has a direct or indirect role in the pathogenesis of the pneumonitis of early onset GBS infection.     

Reduction of morbidity and mortality rates for neonatal group B streptococcal disease through early diagnosis and chemoprophylaxis.

Pregnant women, part of the term service population at Orlando Regional Medical Center, were screened for group B streptococci (GBS), using Lim Group B Strep Broth (GIBCO Laboratories, Madison, Wis.) and the Phadebact Strep B Test (Pharmacia Diagnostics, Piscataway, N.J.). Of the 803 women screened, 173 were confirmed as colonized with GBS at the time of admission in labor. Eighty of these women were treated with ampicillin at least 6 h prior to delivery. The remaining 93 women received no ampicillin. None of the infants born to the treated women was colonized with GBS at surface culture sites. Forty-three of the infants born to untreated women were colonized. Rapid identification of GBS colonization in women, combined with ampicillin chemoprophylaxis, significantly reduced vertical transmission of GBS.     

Synergistic effects of streptolysin S and streptococcal pyrogenic exotoxin B on the mouse model of group A streptococcal infection

Streptococcus pyogenes is a group A streptococcus (GAS) and an important human pathogen that causes a variety of diseases. Streptococcal pyrogenic exotoxin B (SPE B) and streptolysin S (SLS) are important virulence factors involved in GAS infection, but it is not clear which one is more virulent. Using an air pouch infection model, the wild-type strain NZ131, its isogenic mutants, and complementary mutants were used to examine the effects of SPE B and SLS on GAS infection. The results of the skin lesion and mouse mortality assays showed that although SPE B and SLS had a synergistic effect on GAS infection, SPE B played a more important role in local tissue damage while SLS had a more prominent effect on mouse mortality. Surveys of the exudates from the air pouch revealed that the expression of inflammatory cytokines was significantly inhibited in the sagB/speB-double-mutant JM4-infected mice. Furthermore, in vivo and in vitro studies showed that the isogenic mutant strains were more susceptible to the immune cell killing than the wild-type strain and that the sagB/speB-double-mutant JM4 was the most sensitive among these strains. Moreover, infection with the sagB/speB-double-mutant JM4 strain caused the least amount of macrophage apoptosis compared to infection with the wild-type NZ131 and the other complementary strains, which express only SPE B or SLS or both. Taken together, these results indicate that both SPE B and SLS contributed to GAS evasion from immune cell killing, local tissue damage, and mouse mortality.     

Cytokine appearance and effects of anti-tumor necrosis factor alpha antibodies in a neonatal rat model of group B streptococcal infection.

Cytokines are suspected of playing an important role in the pathophysiology of septic shock. This study was undertaken to determine whether tumor necrosis factor alpha (TNF-alpha) induces the production of other cytokines and mediates mortality in a neonatal rat model of sepsis caused by group B streptococci (GBS). We have measured TNF-alpha, interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6), and gamma interferon (IFN-gamma) levels in neonatal rats infected with different strains (H738, 259, and 90) and doses (1 50% lethal dose [LD50] and 5 90% lethal doses [LD90]) of type III GBS. TNF-alpha and IL-6 were detected by the L929 cytotoxicity and the B9 proliferation assays, respectively, in serial plasma samples. IL-1 alpha and IFN-gamma were measured in spleen homogenates by enzyme-linked immunosorbent assay kits by using antibodies raised against the corresponding mouse cytokines. Plasma TNF-alpha levels significantly rose above baseline values within 12 h after intraperitoneal challenge with 5 LD90 of GBS strain H738, corresponding to 3 x 10(3) CFU. A mean peak TNF-alpha concentration of 232 +/- 124 U/ml was reached at 20 h. Peak IL-1 alpha and IL-6 levels of 766 +/- 404 U/g and 1,033 +/- 520 U/ml, respectively, were reached at 24 h after bacterial challenge. Maximal spleen concentrations of IFN-gamma (449 +/- 283 U/g) were measured at 36 h. Concentrations of TNF-alpha, but not other cytokines, remained significantly elevated at 72 h, a time when mortality approached 100%. Significant correlations were found between concentrations of each of the cytokines tested and the logs of CFU concentrations in the blood. In order to ascertain whether TNF-alpha influenced the production of other cytokines, rat pups received two injections of anti-murine TNF-alpha or normal rabbit serum at 2 h before and at 26 h after challenge with live GBS. Plasma TNF-alpha bioactivity was undetectable in anti-TNF-alpha-treated animals, while IL-6 and IFN-gamma, but not IL-1 alpha, levels were significantly reduced, compared with normal serum controls. Rat pups pretreated with anti-TNF-alpha serum and infected with 1 and 5 LD90 of strains H738 and 259 showed enhanced early (48 to 72 h) survival. However, by 96 h this protection was no longer apparent.