Induction of experimental endocarditis by continuous low-grade bacteremia mimicking spontaneous bacteremia in humans.

Transient high-grade bacteremia following invasive procedures carries a risk of infective endocarditis (IE). This is supported by experimental endocarditis. On the other hand, case-control studies showed that IE could be caused by cumulative exposure to low-grade bacteremia occurring during daily activities. However, no experimental demonstration of this latter possibility exists. This study investigated the infectivity in animals of continuous low-grade bacteremia compared to that of brief high-grade bacteremia. Rats with aortic vegetations were inoculated with Streptococcus intermedius, Streptococcus gordonii or Staphylococcus aureus (strains Newman and P8). Animals were challenged with 10(3) to 10(6) CFU. Identical bacterial numbers were given by bolus (1 ml in 1 min) or continuous infusion (0.0017 ml/min over 10 h). Bacteremia was 50 to 1,000 times greater after bolus than during continuous inoculation. Streptococcal bolus inoculation of 10(5) CFU infected 63 to 100% vegetations compared to 30 to 71% infection after continuous infusion (P > 0.05). When increasing the inoculum to 10(6) CFU, bolus inoculation infected 100% vegetations and continuous infusion 70 to 100% (P > 0.05). S. aureus bolus injection of 10(3) CFU infected 46 to 57% valves. This was similar to the 53 to 57% infection rates produced by continuous infusion (P > 0.05). Inoculation of 10(4) CFU of S. aureus infected 80 to 100% vegetations after bolus and 60 to 75% after continuous infusion (P > 0.05). These results show that high-level bacteremia is not required to induce experimental endocarditis and support the hypothesis that cumulative exposure to low-grade bacteremia represents a genuine risk of IE in humans.

Predictors of endocarditis in isolates from cultures of blood following dental extractions in rats with periodontal disease.

Rats with periodontitis and catheter-induced aortic valve vegetations underwent dental extractions. Cultures of blood obtained 1 min later showed polymicrobial bacteremia in 19 of 19 rats, mostly due to viridans streptococci (18 of 19), Morganella (15 of 19), group G streptococci (13 of 19), and Staphylococcus aureus (10 of 19). Viridans streptococci circulated in higher numbers than did group G streptococci and S. aureus (P less than .01). Three days after dental extractions, 18 of 20 rats had endocarditis. Fifteen (83%) of 18 infections were due to group G streptococci, 9 (50%) of 18 were due to S. aureus, and 2 (11%) of 18 were due to viridans streptococci (P less than .05). In vitro, adherence to platelet-fibrin matrices of endocarditis strain 8 of group G streptococcus was two times greater than that of endocarditis strain S. aureus 23 and three to four times greater than that of Streptococcus sanguis 44 and Morganella morganii 93 (P less than 10(-5)). The inoculum size that produced endocarditis in 90% of rats after iv challenge was 10(5) cfu for group G streptococcus strain 8 and 10(7) for S. sanguis 44.

Mechanisms of successful amoxicillin prophylaxis of experimental endocarditis due to Streptococcus intermedius.

Prophylaxis with amoxicillin (40 mg/kg) was studied in rats with aortic valve vegetations. Bacteria on the valves were quantitated early (10 min to 6 hr) and late (three days) after intravenous challenge with tolerant Streptococcus intermedius. Amoxicillin reduced by 40% the number of bacteria per valve 10 min after intravenous challenge with 10(5) S. intermedius (P less than .05) and by 74% the incidence of endocarditis three days thereafter (P less than .0001). Bacterial multiplication started 2 hr after challenge in control rats, whereas bacteria disappeared in 6 hr in amoxicillin-treated rats. Intravenous penicillinase 30 min after challenge abolished successful amoxicillin prophylaxis, a result demonstrating the necessity of prolonged growth inhibition for protection. Growth inhibition for 18 hr (two subsequent amoxicillin doses) was necessary for protection after intravenous challenge with 10(5) S. intermedius. Thus, in the absence of bacterial killing, inhibition of valvular colonization by amoxicillin was not as important a mechanism of endocarditis prophylaxis as was prolonged inhibition of bacterial growth, which allowed adherent bacteria to be cleared from the valves.

Septic arthritis of the pubic symphysis caused by Streptococcus mitis.

Septic arthritis of the pubic symphisis is distinguished from osteitis pubis by positive cultures. The symptoms, physical examination and laboratory findings of these two conditions are comparable. We present a case of 57-year-old woman with septic arthritis of pubic symphisis caused by Streptococcus mitis, a commensal oral flora that belongs to viridans group streptococci, which normally reside in the oral cavity, the gastrointestinal and the urogenital tract.

Loss of penicillin tolerance by inactivating the carbon catabolite repression determinant CcpA in Streptococcus gordonii.

OBJECTIVES: Antibiotic tolerance is a phenomenon allowing bacteria to withstand drug-induced killing. Here, we studied a penicillin-tolerant mutant of Streptococcus gordonii (Tol1), which was shown to be deregulated in the expression of the arginine deiminase operon (arc). arc was not directly responsible for tolerance, but is controlled by the global regulator CcpA. Therefore, we sought whether CcpA might be implicated in tolerance. METHODS: The ccpA gene was characterized and subsequently inactivated by PCR ligation mutagenesis in both the susceptible wild-type (WT) and Tol1. The minimal inhibitory concentration and time-kill curves for the strains were determined and the outcome of penicillin treatment in experimental endocarditis assessed. RESULTS: ccpA sequence and expression were similar between the WT and Tol1 strains. In killing assays, the WT lost 3.5 +/- 0.6 and 5.3 +/- 0.6 log(10) cfu/mL and Tol1 lost 0.4 +/- 0.2 and 1.4 +/- 0.9 log(10) cfu/mL after 24 and 48 h of penicillin exposure, respectively. Deletion of ccpA almost totally restored Tol1 kill susceptibility (loss of 2.5 +/- 0.7 and 4.9 +/- 0.7 log(10) cfu/mL at the same endpoints). In experimental endocarditis, penicillin treatment induced a significant reduction in vegetation bacterial densities between Tol1 (4.1 log(10) cfu/g) and Tol1DeltaccpA (2.4 log(10) cfu/g). Restitution of ccpA re-established the tolerant phenotype both in vitro and in vivo. CONCLUSIONS: CcpA, a global regulator of the carbon catabolite repression system, is implicated in penicillin tolerance both in vitro and in vivo. This links antibiotic survival to bacterial sugar metabolism. However, since ccpA sequence and expression were similar between the WT and Tol1 strains, other factors are probably involved in tolerance.

Estudo da resistência do streptococcus pneumoniae à penicilina em pneumopatias infecciosas nas cidades de Porto Alegre e Caxias do Sul (RS - Brasil)

A resistência aos antibióticos dos patógenos mais comuns do trato respiratório está aumentando mundialmente. Recentemente, Streptococcus pneumoniae resistente à penicilina tem sido isolado em diversos países, e a freqüência dessas cepas tem elevado de modo alarmante. O aumento da resistência, com conseqüentes implicações terapêuticas, tem levado a uma reavaliação do uso dos antibióticos ß-lactâmicos para o tratamento de infecções pneumocócicas. No presente trabalho, um total de 107 amostras de Streptococcus pneumoniae, obtidas de materiais provenientes de pacientes adultos ambulatoriais e hospitalizados, em dois centros médicos de duas cidades do Rio Grande do Sul (Porto Alegre e Caxias do Sul), os quais apresentavam quadro clínico-radiológico de infecção pulmonar, foram analisadas com o objetivo de estudar-se a resistência do germe à penicilina. As amostras constituídas de escarro (80,4%), lavado brônquico (13,5%) e aspirado traqueal (6,6%) foram coletadas no período compreendido entre Julho de 1998 e Julho de 1999. O material foi semeado em meio de Agar sangue e as colônias suspeitas de Streptococcus pneumoniae foram transferidas para meio de Mueller-Hinton para teste de optoquina e de sensibilidade à penicilina com discos de oxacilina. Um halo de inibição da oxacilina menor do que 20 mm indicava a realização de teste para determinação da concentração inibitória mínima (MIC) com E-test. Um total de nove cepas foi identificado como tendo resistência intermediária à penicilina (MIC 0,1-1,0μg/ml) e nenhuma cepa resistente (resistência elevada: MIC > 2,0 μg/ml) foi identificada. Uma monitorização local das cepas quanto à resistência antimicrobiana é de grande importância para os clínicos no manejo de infecções pneumocócicas.

Naso-orbicular tissue necrosis by Streptococcus parasanguis in a patient with Fanconi anemia: Clinical and laboratory aspects

Fanconi anemia (FA) is a rare autosomal recessive disorder, characterized by pancytopenia and progressive hypoplasia of the bone marrow. A 23-year-old woman with FA showed severe pancytopenia and developed an abscess on the infraorbicular region on the right side of the face that progressed to phlegmon and caused tissue necrosis of the nostrils, nasal septum, nasal fossa, and posterior orbital region. Laboratory examination showed Streptococcus parasanguis as the etiologic agent of the phlegmon. Supportive treatment was recommended due to donor incompatibility for bone marrow transplant. The intraoral examination showed spontaneous gingival bleeding, edema of the interdental papillae, hematomas on the superior and inferior lips, bacterial and fungal infections, and adequate oral hygiene. The patient was treated with the administration of an antibiotic (imipenem), an antifungal (amphotericin B), and mouth washing with antiseptic solutions. Periodontal prophylaxis and orientation to and control of oral hygiene and diet were also used during the remission period. For functional and esthetic rehabilitation of the alar regions and nasal dorsum, an acrylic resin nasal prosthesis was made, supported by a spectacle frame.

Cost-effectiveness of universal prophylaxis in pregnancy with prior group B streptococci colonization.

OBJECTIVE: To estimate the costs and outcomes of rescreening for group B streptococci (GBS) compared to universal treatment of term women with history of GBS colonization in a previous pregnancy. STUDY DESIGN: A decision analysis model was used to compare costs and outcomes. Total cost included the costs of screening, intrapartum antibiotic prophylaxis (IAP), treatment for maternal anaphylaxis and death, evaluation of well infants whose mothers received IAP, and total costs for treatment of term neonatal early onset GBS sepsis. RESULTS: When compared to screening and treating, universal treatment results in more women treated per GBS case prevented (155 versus 67) and prevents more cases of early onset GBS (1732 versus 1700) and neonatal deaths (52 versus 51) at a lower cost per case prevented ($8,805 versus $12,710). CONCLUSION: Universal treatment of term pregnancies with a history of previous GBS colonization is more cost-effective than the strategy of screening and treating based on positive culture results.

Obesity during pregnancy on vagal tone, hemoglobin A1c, oxygenation, and perinatal outcomes

Purpose: To examine the effect of obesity and gestational weight gain on heart rate variability (HRV), oxygenation (HbO 2 and SpO2), hemoglobin A1c (HbA1c) and the frequency of pregnancy complications in obese (O) and non-obese (NO) women.^ Design: The study was an observational comparison study with a repeated measures design. ^ Setting: The setting was a low risk prenatal, university clinic located in a large southeastern metropolitan city. ^ Sample: The sample consisted of a volunteer group of 41 pregnant women who were observed at the three time points of 20, 28, and 36 weeks gestation. ^ Analysis: Analysis included general linear modeling with repeated measures to test for group differences with changes over time on vagal response, HbA1c, and oxygenation. Odds ratios were computed to compare the frequency of birth outcomes. ^ Findings: The interaction effect of time between O and NO women on HbO2 was significant. The mean HP, RSA, and HbO2 changed significantly over time within the NO women. The mean HbA 1c increased significantly over time within the O women. Women with excess gestational weight gain had significantly lower heart period than women with weight gain within the IOM recommendations. Obese women were more likely to have Group B streptococcal infections, gestational hypertension, give birth by cesarean or instrument assistance, and have at least one postnatal event. ^ Conclusions: Monitoring HRV, oxygenation, and HbA1c using minimally invasive measures may permit early identification of alterations in autonomic response. Implementation of interventions to promote vagal tone may help to reduce risks for adverse perinatal outcomes related to obesity. Future studies should examine the effect of obesity on the vagal response and perinatal outcomes. ^

Scabies mite inactivated serine protease paralogues are present both internally in the mite gut and externally in feces

The scabies mite, Sarcoptes scabiei, is the causative agent of scabies, a disease that is common among disadvantaged populations and facilitates streptococcal infections with serious sequelae. Previously, we encountered large families of genes encoding paralogues of house dust mite protease allergens with their catalytic sites inactivated by mutation (scabies mite inactivated protease paralogues [SMIPPs]). We postulated that SMIPPs have evolved as an adaptation to the parasitic lifestyle of the scabies mite, functioning as competitive inhibitors of proteases involved in the host–parasite interaction. To propose testable hypotheses for their functions, it is essential to know their locations in the mite. Here we show by immunohistochemistry that SMIPPs exist in two compartments: 1) internal to the mite in the gut and 2) external to the mite after excretion from the gut in scybala (fecal pellets). SMIPPs may well function in both of these compartments to evade host proteases.

Group B streptococcal neonatal infections in Rio Grande do Sul, Brazil

Group B Streptococcus is the most common pathogen found in neonatal sepsis in North America. OBJECTIVES: We describe 15 cases of neonatal infections by Group B Streptococcus (Streptococcus agalactiae) at a Neonatal Intensive Care Unit of a public and teaching hospital. METHODS: We conducted a study at Hospital de Clínicas de Porto Alegre, from January 1st, 1996 to June 30, 1999. Diagnosis of neonatal infection was established according to the findings of Group B Streptococcus in blood culture associated with alterations resembling sepsis on the basis of clinical picture and laboratory findings. RESULTS: Fifteen cases of neonatal infections by Group B Streptococcus were detected. Eleven cases consisted of early-onset sepsis, 2 cases of occult bacteremia and 2 cases of late-onset sepsis. Eight cases had septic shock (53%), 8 cases had pneumonia (53%), and 4 cases had meningitis (27%). Fourteen cases were diagnosed from a positive blood culture, and 1 case from evidence of these bacteria in pulmonary anatomopathological examination. Thirteen cases (87%) were diagnosed before 72 hours of life. We had 3 deaths (20%), and 3 cases of meningitis developing neurological deficits. CONCLUSIONS: Streptococcus Group B is one of the most important pathogens in the etiology of early-onset neonatal sepsis at our hospital, with high mortality and morbidity. However, we do not know the incidence of GBS neonatal infections at other hospitals. More data are needed to establish a basis for trials of different strategies to reduce these infections.

Anti-Group A Streptococcal Vaccine Epitope STRUCTURE, STABILITY, AND ITS ABILITY TO INTERACT WITH HLA CLASS II MOLECULES

Streptococcus pyogenes infections remain a health problem in several countries due to poststreptococcal sequelae. We developed a vaccine epitope (StreptInCor) composed of 55 amino acids residues of the C-terminal portion of the M protein that encompasses both T and B cell protective epitopes. The nuclear magnetic resonance (NMR) structure of the StreptInCor peptide showed that the structure was composed of two microdomains linked by an 18-residue alpha-helix. A chemical stability study of the StreptInCor folding/unfolding process using far-UV circular dichroism showed that the structure was chemically stable with respect to pH and the concentration of urea. The T cell epitope is located in the first microdomain and encompasses 11 out of the 18 alpha-helix residues, whereas the B cell epitope is in the second microdomain and showed no alpha-helical structure. The prediction of StreptInCor epitope binding to different HLA class II molecules was evaluated based on an analysis of the 55 residues and the theoretical possibilities for the processed peptides to fit into the P1, P4, P6, and P9 pockets in the groove of several HLA class II molecules. We observed 7 potential sites along the amino acid sequence of StreptInCor that were capable of recognizing HLA class II molecules (DRB1*, DRB3*, DRB4*, and DRB5*). StreptInCoroverlapping peptides induced cellular and humoral immune responses of individuals bearing different HLA class II molecules and could be considered as a universal vaccine epitope.

Efficacy of trovafloxacin in treatment of experimental staphylococcal or streptococcal endocarditis.

The efficacy of trovafloxacin against Staphylococcus aureus and viridans group streptococci was investigated in vitro and in an experimental model of endocarditis. The MICs at which trovafloxacin and ciprofloxacin inhibited 90% of clinical isolates of such bacteria (MIC90s) were (i) 0.03 and 2 mg/liter, respectively, for 30 ciprofloxacin-susceptible S. aureus isolates, (ii) 32 and 128 mg/liter, respectively, for 20 ciprofloxacin-resistant S. aureus isolates, and (iii) 0.25 and 8 mg/liter, respectively, for 28 viridans group streptococci. Rats with aortic vegetations were infected with either of two ciprofloxacin-susceptible but methicillin-resistant S. aureus strains (strains COL and P8), one penicillin-susceptible Streptococcus sanguis strain, or one penicillin-resistant Streptococcus mitis strain. Rats were treated for 3 or 5 days with doses that resulted in kinetics that simulated those achieved in humans with trovafloxacin (200 mg orally once a day), ciprofloxacin (750 mg orally twice a day), vancomycin (1 g intravenously twice a day), or ceftriaxone (2 g intravenously once a day). Against the staphylococci, the activities of both trovafloxacin and ciprofloxacin were equivalent to that of vancomycin, and treatment of endocarditis with these drugs was successful (P < 0.05). However, ciprofloxacin selected for resistant derivatives in vitro and in vivo, whereas trovafloxacin was 10 to 100 times less prone than ciprofloxacin to select for resistance in vitro and did not select for resistance in vivo. Against the two streptococcal isolates, trovafloxacin significantly (P < 0.05) decreased bacterial counts in the vegetations but was less effective than the control drug, ceftriaxone. Thus, a simulated oral dose of trovafloxacin (200 mg per day) was effective against ciprofloxacin-susceptible staphylococci and was less likely than ciprofloxacin to select for resistance. The simulated oral dose of trovafloxacin also had some activity against streptococcal endocarditis, but optimal treatment of infections caused by such organisms might require higher doses of the drug.

Virulent infections due to alpha-haemolytic streptococci in cancer patients and their management

Streptococci of the viridans group have long been considered to be minor pathogens, except in bacterial endocarditis. For some years, however, these microorganisms have been the cause of serious bacteraemia in neutropenic patients receiving intensive chemotherapy. These infections can lead to severe complications such as endocarditis, respiratory distress syndromes or shock, and are associated with a mortality rate ranging from 6-30%. The principal risk factors for these infections are profound neutropenia, antibiotic prophylaxis with quinolones or cotrimoxazole, large doses of cytosine arabinoside, a recent history of chemotherapy, oropharyngeal mucositis and viridans streptococcal colonization. Protective factors are the early administration of parenteral antibiotics during periods of neutropenia, or the prophylactic administration of penicillin. Although the introduction of penicillin to prophylactic antibiotic regimens has led to a decrease in the incidence of these infections, the emergence of strains resistant to beta-lactams is a worrying problem which could compromise this type of treatment.

Studies of group B streptococcal infection in mice deficient in complement component C3 or C4 demonstrate an essential role for complement in both innate and acquired immunity.

Group B streptococci (GBS) cause sepsis and meningitis in neonates and serious infections in adults with underlying chronic illnesses. Specific antibodies have been shown to be an important factor in protective immunity for neonates, but the role of serum complement is less well defined. To elucidate the function of the complement system in immunity to this pathogen, we have used the approach of gene targeting in embryonic stem cells to generate mice totally deficient in complement component C3. Comparison of C3-deficient mice with mice deficient in complement component C4 demonstrated that the 50% lethal dose for GBS infection was reduced by approximately 50-fold and 25-fold, respectively, compared to control mice. GBS were effectively killed in vitro by human blood leukocytes in the presence of specific antibody and C4-deficient serum but not C3-deficient serum. The defective opsonization by C3-deficient serum in vitro was corroborated by in vivo studies in which passive immunization of pregnant dams with specific antibodies conferred protection from GBS challenge to normal and C4-deficient pups but not C3-deficient pups. These results indicate that the alternative pathway is sufficient to mediate effective opsonophagocytosis and protective immunity to GBS in the presence of specific antibody. In contrast, the increased susceptibility to infection of non-immune mice deficient in either C3 or C4 implies that the classical pathway plays an essential role in host defense against GBS infection in the absence of specific immunity.