Severe neonatal echovirus 20 infection characterized by hepatic failure.
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Diagnosis, Differential↗
Biomedical subjects
A Fleer
Publications and source records attributed to A Fleer.
Intracellular pathways involved in tumor necrosis factor-alpha release by human monocytes on stimulation with lipopolysaccharide or staphylococcal peptidoglycan are partly similar.
This study compared the effects of intracellular pathway inhibitors on tumor necrosis factor-alpha (TNF-alpha) release from human monocytes. Cells were stimulated with peptidoglycan (PG) from Staphylococcus epidermidis or with Escherichia coli lipopolysaccharide (LPS), both in the presence of 10% human serum. Of 10 substances tested, only the protein tyrosine kinase inhibitor tyrphostin AG 126 discriminated significantly between PG and LPS: TNF-alpha release induced by PG, but not by LPS, was dose-dependently suppressed. The results obtained with other modulatory substances, including different protein kinase and G protein inhibitors, suggest that calmodulin-dependent protein kinase, protein tyrosine kinase, and a cholera-toxin-sensitive G protein are involved in both PG- and LPS-induced TNF-alpha release. Further, drugs such as pentoxifylline, chloroquine, and the antioxidant apocynin similarly inhibited TNF-alpha release by PG- as well as LPS-stimulated cells.
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
Moraxella catarrhalis in acute laryngitis: infection or colonization?
The complement phenotypes of Moraxella catarrhalis isolates obtained from adult patients with acute laryngitis were investigated using a microliter serum bactericidal assay and compared with those of other donor groups. Laryngitis isolates had a higher proportion (57%) of complement-resistant strains than did carrier strains from healthy 8- to 13-year-old schoolchildren (16%). The difference between these groups was statistically significant (chi2 [3 x 2 table] = 21.55; P < .001). The relatively frequent occurrence of the complement-resistant (virulence-associated) phenotype in adults with acute laryngitis supports the theory of an active role of M. catarrhalis in the pathogenesis of acute laryngitis.
Adolescent↗
Coagulase-negative staphylococci isolated from two cases of toxic shock syndrome lack superantigenic activity, but induce cytokine production.
Two strains of Staphylococcus epidermidis isolated from patients with toxic shock symptoms have been reported to carry genes related to S. aureus enterotoxins B and C by dot-blot hybridisation, although the corresponding superantigenic toxins were not detected immunologically. We here show that these strains produce no superantigens capable of stimulating proliferation of human mononuclear leukocytes or rabbit splenocytes, and that no DNA homologous to the seb or sec genes can be detected by PCR. However, stimulation of human monocytes by whole killed bacteria induced dose-dependent production of the cytokines TNF alpha, IL-1 beta and IL-6, which may be responsible for the clinical symptoms in these patients.
Antigens, Bacterial↗
Molecular characterization of the BRO beta-lactamase of Moraxella (Branhamella) catarrhalis.
A rapid increase in the prevalence of beta-lactamase-producing Moraxella (Branhamella) catarrhalis strains has been noticed during the last decades. Today, more than 80% of strains isolated worldwide produce beta-lactamase. To investigate beta-lactamase(s) of M. catarrhalis at the molecular level, the BRO-1 beta-lactamase gene (bla) was isolated as part of a 4,223-bp HindIII fragment. Sequence analysis indicated that bla encodes a polypeptide of 314 amino acid residues. Insertional inactivation of bla in M. catarrhalis resulted in complete abrogation of beta-lactamase production and ampicillin resistance, demonstrating that bla is solely responsible for beta-lactam resistance. Comparison with other beta-lactamases suggested that M. catarrhalis beta-lactamase is a unique enzyme with conserved residues at the active sites. The presence of a signal sequence for lipoproteins suggested that it is lipid modified at its N terminus. In keeping with this assumption was the observation that 10% of beta-lactamase activity was found in the membrane compartment of M. catarrhalis. M. catarrhalis strains produce two types of beta-lactamase, BRO-1 and BRO-2, which differ in their isoelectric points. The BRO-1 and BRO-2 genes from two ATCC strains of M. catarrhalis were sequenced, and only one amino acid difference was found between the predicted products. However, there was a 21-bp deletion in the promoter region of the BRO-2 gene, possibly explaining the lower level of production of BRO-2. The G + C content of bla (31%) was significantly lower than those of the flanking genes (47 and 50%), and the overall G + C content of the M. catarrhalis genome (41%). These results indicate that bla was acquired by horizontal gene transfer from another, still unknown species.
Amino Acid Sequence↗
Ultrastructural organization and regulation of a biomaterial adhesin of Staphylococcus epidermidis.
Coagulase-negative staphylococci have emerged as important pathogens in infections associated with intravascular devices. Microbial adherence to biomaterial surfaces is a crucial step in the pathogenesis of these infections. Staphylococcal surface proteins (herein referred to as SSP-1 and SSP-2) are involved in the attachment of Staphylococcus epidermidis 354 to polystyrene. In the present study we show that the adhesin protrudes from the cell surface as a fimbria-like polymer. Furthermore, in vitro proteolytic cleavage of SSP-1 produces an SSP-2-like protein which coincides with a loss of adhesive function. SSP-1 expression is down-regulated in a phenotypical variant of S. epidermidis 354 whereas SSP-2 expression is not. These results could suggest that proteolytic cleavage is a key to the regulation of the adhesive state of S. epidermidis in vivo.
Adhesins, Bacterial↗
Complement resistance is a virulence factor of Branhamella (Moraxella) catarrhalis.
The purpose of this study was to investigate complement resistance in Branhamella (Moraxella) catarrhalis isolated from healthy schoolchildren or sputum-producing adult patients. Two techniques were used: a serum bactericidal assay as the gold standard and an easier 'culture and spot' test. Children (age 4-13; n = 303) and patients (n = 1047) showed high colonization/infection rates with B. catarrhalis (31% and 19%, respectively). Complement resistance or intermediate sensitivity occurred frequently in patient isolates (62% and 27%, respectively) and less often in children (33% and 8.5%, respectively; P << 0.0001). In young children (age 4-5 years), the proportion of complement-resistant strains was around 50%. Complement resistance in B. catarrhalis is associated with illness and may hence be considered a virulence factor.
Adolescent↗
Serum-induced potentiation of tumor necrosis factor alpha production by human monocytes in response to staphylococcal peptidoglycan: involvement of different serum factors.
Peptidoglycan from a Staphylococcus epidermidis strain, isolated from a patient with septicemia, was preincubated with human serum. This mixture was then investigated for its potency to induce tumor necrosis factor (TNF) secretion by human blood monocytes. TNF was measured in the supernatants by using a bioassay and/or an enzyme-linked immunosorbent assay specific for TNF alpha (TNF-alpha). Although earlier studies indicated that staphylococcal peptidoglycan alone is a relatively poor stimulator of TNF-alpha production, the present study shows that human serum highly potentiates peptidoglycan-induced TNF-alpha release by human monocytes. In the presence of serum and in the low-dose range, peptidoglycan was almost as potent as endotoxin. At high peptidoglycan concentrations, monocytes showed an extremely high TNF-alpha response, but again only in the presence of serum. At low peptidoglycan doses, the stimulatory effect of serum was abrogated by heat treatment or depleting serum of complement components C1 and C3/C4, which suggests a role for the classical complement pathway. At high doses of peptidoglycan, the serum stimulatory effect depended mainly on immunoglobulin G.
Blood Physiological Phenomena↗
Clinical significance of Clostridium difficile and its toxins in faeces of immunocompromised children.
In this study, clinical and laboratory findings were tested for correlation with the presence of Clostridium difficile. The toxigenicity of the isolated strains and the toxins were determined in faecal samples of immunocompromised children admitted to a single room for protective isolation. Using the toxin assay as the gold standard, the culture sensitivity of toxigenic C difficile was 94.1%, the specificity 93.8%, the positive predictive value 62.8%, and the negative predictive value 99.3%. Correction for stools with a positive culture of toxigenic C difficile preceding detection of toxin, resulted in a positive prediction value of 78.4%. A statistically significant association was found between a positive faecal toxin assay and fever, and between a positive culture of toxigenic C difficile and abdominal pain: 42% of the patients with positive toxin assays had fever versus 21% with negative toxin assays, and 66% of the patients with a positive culture for toxigenic C difficile had abdominal pain, versus 22% with negative cultures. Further analysis of the cultures and toxin assays showed no statistically significant association with diarrhoea, fever, white blood cell count, C reactive protein concentrations, or abdominal pain. Based on these findings, it is suggested that immunocompromised children should be treated when toxigenic C difficile is cultured or when toxin is detected in stool samples.
Abdominal Pain↗
[Diagnosis and chemoprophylaxis of perinatal infections caused by beta-hemolytic streptococci from Group B].
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Carrier State↗
Disseminating infection with Scytalidium dimidiatum in a granulocytopenic child.
A 13-year-old Moroccan boy in The Netherlands developed fever and a lesion resembling ecthyma gangrenosum on the abdomen during cytostatic drug treatment for a lymphoblastic B-cell lymphoma. Scytalidium dimidiatum was cultured from blood and the abdominal skin lesion. The patient was successfully treated with amphotericin B. The fungus Scytalidium dimidiatum is a fairly common plant pathogen in tropical and subtropical countries and is known to cause dermatomycoses in humans in these areas. This case demonstrates that it is necessary to be aware that immigrants from these areas can import their own fungal flora, some members of which may cause life-threatening disease in the case of patients with immune suppression.
Adolescent↗
Development of resistance to aminoglycosides among coagulase-negative staphylococci and enterobacteriaceae in a neonatal intensive care unit.
A prospective study of the development of resistance to aminoglycosides among coagulase-negative staphylococci (CNS) and Enterobacteriaceae (ENT) was conducted for all patients admitted to a neonatal intensive care unit (NICU) from October 1985 to January 1990. A change in antibiotic regimen from gentamicin to amikacin occurred in January 1986, due to widespread gentamicin resistance among CNS, the most important cause of nosocomial infections in this NICU. From 657 patients, 884 faecal cultures, 1505 cultures from the respiratory tract and 152 blood cultures were included in the study. After its introduction, susceptibility to amikacin decreased rapidly in faecal and respiratory CNS isolates (from 62% to 28% and from 58% to 23% respectively). During the first half year, resistance to amikacin in faecal CNS isolates developed more rapidly among antibiotic-treated patients than among patients not treated with antibiotics. Susceptibility to amikacin in CNS blood isolates decreased more slowly, from 94% to 58% in 1987, while subsequently an increase in susceptibility was observed to about 80% in 1989. The same difference in development of resistance in faecal and respiratory CNS isolates compared to CNS blood isolates was noticed for gentamicin and tobramycin. In contrast, ENT remained highly (85-100%) susceptible to amikacin, gentamicin and tobramycin throughout the study period. It was concluded that four years after its introduction amikacin still appeared to be a valuable antibiotic in combination treatment of the vast majority of clinically important infections occurring in our NICU, since both Enterobacteriaceae and the majority of CNS blood isolates proved to be susceptible to this agent.(ABSTRACT TRUNCATED AT 250 WORDS)
Amikacin↗
Chemiluminescence of human polymorphonuclear leucocytes after stimulation with whole cells and cell-wall components of Staphylococcus epidermidis.
The purpose of this study was to define cell-wall components of Staphylococcus epidermidis responsible for activation of human polymorphonuclear leucocytes (PMNL). Metabolic activation of PMNL was determined by chemiluminescence (CL). Purified peptidoglycan (PG) induced a concentration-dependent metabolic burst in PMNL. The minimal concentration needed for CL induction was 1 microgram/ml. Comparison between different S. epidermidis strains showed variation in the capacity to induce CL in PMNL. Purified PG induced a higher CL response in PMNL than its intact parent strain; this effect was found in all S. epidermidis strains. Lipoteichoic acid (LTA), PG stem peptide and muramyldipeptide (MDP) did not induce CL; teichoic acid induced a CL response only at very high concentrations. No differences in CL inducing capacity were found between PG, crude cell walls, and purified cell walls of S. epidermidis. Sonication of PG strongly diminished CL-inducing capacity. PG treatment with mutanolysin immediately resulted in decreased CL-inducing capacity. Treatment of PG with S. aureus lytic enzyme (SALE) 10 micrograms/ml for up to 15 min enhanced the CL response to PMNL; a similar increase in CL was induced by PG treated with SALE at 1 microgram/ml for up to 120 min. Beyond these times, a continuous decrease in PG-induced CL was observed. In conclusion, PG was found to be the major cell-wall component of S. epidermidis involved in CL induction. Moreover, a minimal fragment size or a specific tertiary structure of PG, or both, is required for metabolic activation of PMNL.
Adult↗
Peptidoglycan and teichoic acid from Staphylococcus epidermidis stimulate human monocytes to release tumour necrosis factor-alpha, interleukin-1 beta and interleukin-6.
Cytokines play a major role in the pathophysiology of septic shock. In this study, human peripheral blood monocytes were stimulated with peptidoglycan and teichoic acid, purified from a strain of Staphylococcus epidermidis. Polymyxin B (PM-B) was added to avoid the effects of possible contamination with endotoxin. Tumour necrosis factor-alpha (TNF), interleukin-1 beta (IL-1), and interleukin-6 (IL-6) in the supernates were measured by enzyme-linked immunosorbent assays. Peptidoglycan and teichoic acid induced TNF, IL-1, and IL-6 in a concentration-dependent manner. Teichoic acid was a weaker inducer than peptidoglycan, especially for IL-1. Lipopolysaccharide from an E. coli strain was used as a control, being 100-1000 times more potent than peptidoglycan and teichoic acid.
Enzyme-Linked Immunosorbent Assay↗
Induction of release of tumor necrosis factor from human monocytes by staphylococci and staphylococcal peptidoglycans.
The role of cytokines in gram-positive infections is still relatively poorly defined. The purpose of this study was to establish whether or not intact staphylococci and purified peptidoglycans and peptidoglycan components derived from staphylococci are capable of stimulating the release of tumor necrosis factor (TNF) by human monocytes. We show here that intact staphylococci and purified peptidoglycans, isolated from three Staphylococcus epidermidis and three S. aureus strains, were indeed able to induce secretion of TNF by human monocytes in a concentration-dependent fashion. TNF release was detected by both enzyme immunoassay and the L929 fibroblast bioassay. In the enzyme immunoassay, a minimal concentration of peptidoglycan of 1 micrograms/ml was required to detect TNF release by monocytes, whereas in the bioassay a peptidoglycan concentration of 10 micrograms/ml was needed to detect a similar amount of TNF release. Peptidoglycan components such as the stem peptide, tetra- and pentaglycine, and muramyl dipeptide were unable to induce TNF release from human monocytes.
Cell Wall↗
The predictive value of CRP and I/T-ratio in neonatal infection.
C-reactive protein (CRP) and immature: total neutrophil ratio (I/T-ratio) were evaluated as tests to detect neonatal sepsis in a prospective study in 185 neonates. The positive predictive values (P.P.A.) of CRP and I/T-ratio when used for screening for infection were 20-30% in early onset and 50-60% in late onset infection. In patients with clinical signs of infection the P.P.A. of CRP and I/T-ratio was 35-45% in early onset and 65-70% in late onset infection. For the whole group of patients the negative predictive accuracy (N.P.A.) of both CRP and I/T-ratio was high, in early as well as in late onset infection (90-98%). Based on incidence rates of 7.5% and 23% for early and late onset infection respectively the chance that the infant was not infected was already 92.5% and 77% for the two types of infection. In conclusion, CRP and I/T-ratio determination are of limited value as diagnostic tests in neonatal infection.
Bacterial Infections↗
Host defense to infection in the neonate.
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Antibodies, Bacterial↗
Characterisation and functional aspects of monoclonal antibodies specific for surface proteins of coagulase-negative staphylococci.
Mouse monoclonal antibodies (MAbs) raised against whole cells of Staphylococcus epidermidis strain 354 were characterised morphologically and functionally. Nine MAbs showed strong reactivity with coagulase-negative staphylococci (CNS). Only two MAbs were specific for CNS; both belonged to the IgG1 subclass, and one, MAb 36.4, reacted only with the strain used for immunisation. In immunoblotting, both CNS-specific MAbs 36.3 and 36.4 reacted strongly with cell-wall protein bands of 220 Kda of S.epidermidis strain 354 and weak reactivity was observed with a 110-Kda band. MAb 36.3 reacted also with 220-230 Kda bands of two other S.epidermidis strains (291 and ATCC 35984) and a 160-180 Kda band of S.epidermidis strain 354. Only MAb 36.4 promoted phagocytosis of strain 354 by polymorphonuclear leucocytes (PMNL) and monocytes, whereas MAb 36.3 and the other MAbs lacked this activity. Opsonisation of S. epidermidis with MAb 36.4 in the presence of complement enhanced uptake by PMNL, but not by monocytes. Furthermore, S.epidermidis strain 354 opsonised with MAb 36.4 induced chemiluminescence of PMNL. Immuno-gold electronmicroscopy with both MAbs 36.3 and 36.4 demonstrated a homogeneous distribution of gold particles on the surface as well as close to the surface of S.epidermidis.
Animals↗