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Query: UMLS:C0014118 (endocarditis)
 15,629 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Streptococci requiring either pyridoxal or L-cysteine for growth were first observed 30 years ago as organisms forming satellite colonies adjacent to colonies of "helper" bacteria. Although they were previously considered nutritional mutants of viridans streptococcal species, the nutritionally variant streptococci (NVS) are currently thought to belong to distinct species of the genus Streptococcus. NVS strains may display pleomorphic cellular morphologies, depending on their growth conditions, and are distinguished from most other streptococci by enzymatic and serological characteristics and the presence of a cell wall chromophore. NVS are found as normal inhabitants of the oral cavity, and in addition to their participation in endocarditis, they have been isolated from a wide range of clinical specimens. Endocarditis caused by NVS is often difficult to eradicate; combinations of penicillin and an aminoglycoside are recommended for treatment. The unique physiological features of the NVS contribute to the difficulties encountered in their recovery from clinical specimens and may play a role in the problems associated with successful treatment of NVS endocarditis.
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PMID:Nutritionally variant streptococci. 207 Mar 44

Brain heart infusion cysteine broth, with and without Panmede (a papain digest of ox liver) and Fastidious Anaerobe Broth, with and without Liquoid, were compared by inoculating the broths with blood collected from each of 51 patients, 2 min after dental extraction. Bacteraemia caused by viridans streptococci or oral non-sporing anaerobes or both was detected in 39 patients (76%). Detection of bacteraemia caused by viridans streptococci and anaerobes was more rapidly achieved by the addition of Panmede to brain heart infusion broth. Significantly more cases of bacteraemia caused by viridans streptococci were detected by use of the Panmede-containing medium than by use of Fastidious Anaerobe Broth after incubation of the broths for only 1 day. Use of brain heart infusion cysteine broth with and without Panmede, and Fastidious Anaerobe Broth permitted detection of bacteraemia caused by viridans streptococci in 26, 11 and 22 patients respectively during incubation for 2 weeks. Bacteraemia caused by anaerobes was detected by use of these three media in 24, 13 and 23 patients respectively. The addition of Liquoid to Fastidious Anaerobe Broth had no significant effect on the detection of bacteraemia caused by viridans streptococci or anaerobes. The Panmede-containing blood-culture medium should be a useful anaerobic broth in the investigation of patients with suspected endocarditis, because viridans streptococci are also rapidly detected.
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PMID:Clinical comparison of anaerobic blood-culture media for detecting bacteraemia due to viridans streptococci and oral anaerobes. 298 26

Nutritionally variant streptococci have been characterized in the past by their growth as satellite colonies and by their nutrient requirements of cysteine or vitamin B6 for growth in complex media. To further understand the growth characteristics of these strains, we studied fresh isolates from patients with endocarditis by using chemically defined medium enriched with 2% Todd-Hewitt dialysate. Under anaerobic conditions, growth yields of the strains in this medium were comparable to those obtained from a complex medium supplemented with vitamin B6, whereas under aerobic conditions, most of the strains had higher growth yields in the semisynthetic medium. Furthermore, the requirement for cysteine and vitamin B6 in the semisynthetic medium was no greater than that of other Streptococcus species. Electron microscopic studies demonstrated normal cell wall structures in organisms grown in the semisynthetic medium as compared with abnormal and irregular cell wall thickening in organisms grown in supplemented complex medium. Finally, these strains appeared to contain a common component when grown in the semisynthetic medium as demonstrated by the appearance of a chromophore after boiling the bacteria at pH 2. Therefore, the demonstration of a medium which permits adequate growth with a normal ultrastructure of nutritionally variant streptococci will permit the further study of this group of important streptococci.
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PMID:Nutritionally variant streptococci from patients with endocarditis: growth parameters in a semisynthetic medium and demonstration of a chromophore. 724 84

Nutritional variant streptococci identified as pyridoxal-dependent Streptococcus mitior (mitis) account for 5 to 6% of streptococcal endocarditis and may be a cause of "culture-negative" endocarditis. Hence, growth of three variant strains in 11 commercial blood culture broths was compared to that in fresh heart infusion broth. For simulation of clinical specimens, culture bottles were injected with 5 ml of human blood, inoculated with approximately 500 colony-forming units (CFU) per bottle, and monitored for 7 days with Gram stains and viable counts. Only Thiol broth (Difco Laboratories, Detroit, Mich.) supported growth without blood at this low inoculum. In media containing blood, maximal growth of 10(9) CFU/ml was reached within 2 days of incubation, and heavy turbidity was consistently observed in only heart infusion broth, Thiol broth, and media supplemented with pyridoxal hydrochloride. Columbia broth (BBL Microbiology Systems, Cockeysville, Md.) with increased cysteine, thioglycollate broth, and one brain heart infusion broth produced moderate growth (1 x 10(8) to 5 x 10(8) CFU/ml), whereas Columbia broth, another brain heart infusion broth, and two brands of tryptic soy broth showed fair growth (1 x 10(7) to 4 x 10(7) CFU/ml). The poor growth (1 x 10(6) to 3 x 10(6) CFU/ml) observed in three other brands of tryptic soy broth was often not apparent macroscopically or by Gram stain. Furthermore, on growth occurred in 40% of tryptic soy broth cultures inoculated with 50 CFU. Therefore, to ensure isolation of these variant streptococci from clinical blood cultures, a medium containing thiol compounds or supplemented with pyridoxal should be used. Subcultures should be made within 2 days of incubation to blood agar enriched with pyridoxal or containing a Staphylococcus sp. streak for satellitism.
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PMID:Evaluation of blood culture media for isolation of pyridoxal-dependent Streptococcus mitior (mitis). 728 85

Streptococcus adjacens and S. defectivus are two recently individualized species of viridans streptococci. Both species were previously designated as nutritionally variant streptococci and characterized by their growth as small satellite colonies supported by 'helper' bacteria, or requiring complex media enriched with cysteine or with pyridoxal. Structural abnormalities were observed under these conditions and balanced growth can be obtained only with a semi-chemically defined medium, in which the cells are morphologically normal and exhibit a parietal chromophore. The two species are primarily isolated from the oral cavity, or from intestinal and genito-urinary tracts. They are likely to be responsible for most blood-culture-negative endocarditis and account for more than 4% of streptococcal strains isolated from blood cultures during this disease. Cases of endocarditis caused by these bacteria exhibit much higher rates of failure, relapse and mortality than those due to other viridans streptococci. The slow growth rate of the bacteria and the production of large amounts of exopolysaccharide in vivo may account for the difficulties encountered in treatment and suggest that a longer course of antimicrobial therapy may be required for successful cures. Results obtained from experimental models of endocarditis confirmed the efficacy of vancomycin as an alternative therapy in patients when a combination of penicillin and aminoglycoside is ineffective or contraindicated.
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PMID:Human endocarditis due to nutritionally variant streptococci: streptococcus adjacens and Streptococcus defectivus. 767 20

We isolated a hitherto undescribed microorganism from a patient with endocarditis. The microscopic appearance, a negative catalase reaction, and growth as satellite colonies next to Staphylococcus epidermidis suggested that this microorganism is a member of the genus Abiotrophia, formerly known as nutritionally variant streptococci. However, the clinical isolate described herein differed markedly from the known Abiotrophia spp., A. adiacens and A. defectiva, in terms of its (i) biochemical properties, (ii) restricted growth temperature range, (iii) whole-cell lysate polypeptide profile, and (iv) unique nutritional requirements. In contrast to the type strains of A. adiacens and A. defectiva, which used L-cysteine and pyridoxal hydrochloride as growth factors, the growth of the clinical isolate was only supported by L-cysteine hydrochloride and not by pyridoxal hydrochloride when the organism was tested in Todd-Hewitt or casein-soy peptone broth. Comparative 16S rRNA gene sequence analysis revealed that the microorganism was a member of the genus Abiotrophia and was most closely related to A. adiacens (96.9% homology). Phenotypic and phylogenetic data are consistent with the assumption of a new species within the genus Abiotrophia, for which we propose the name Abiotrophia elegans sp. nov. The unique nutritional requirements of this strain are of importance for diagnostic laboratories. The media of blood culture systems supplemented only with pyridoxal hydrochloride as a growth factor may fail to promote the growth of A. elegans sp. nov., and thus, these systems might not detect this microorganism as a possible cause of endocarditis.
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PMID:Abiotrophia elegans sp. nov., a possible pathogen in patients with culture-negative endocarditis. 943 29

Streptococci that were dependent for their growth upon staphylococci were isolated from a patient with sub-acute bacterial endocarditis and subsequently identified as nutritionally-variant streptococci (NVS). Failure of the isolate to grow on agar media supplemented with pyridoxal hydrochloride or L-cysteine, the known supporting growth factors for NVS, made conventional antimicrobial disc diffusion assay impossible. We modified the assay by co-inoculating Staphylococcus aureus resistant to the drugs being tested as a helper to support the growth of the NVS. Streaking S. aureus closely to the antibiotic discs that were placed above NVS resulted in the growth of satellite colonies of NVS that orbited the S. aureus and that produced a pattern of interrupted zones of growth inhibition. Using an alternative method--adding staphylococcal secreting factor(s) to a 10% staphylococcal cell-free culture supernatant and adding this to an antibiotic susceptibility testing medium,--we found that the NVS formed colonies that formed clear zones of growth inhibition around the disc. When the sizes of the growth inhibition zones produced by both these methods were compared with those recommened by the NCCLS, the NVS were found to be susceptible to penicillin, vancomycin, erythromycin, chloramphenicol, cefoperazone, cefamandole and ofloxacin and resistant to co-trimoxazole, gentamicin and tetracycline. Based on these findings, vancomycin was selected for treatment and the patient was cured of endocarditis. The correlation between the in vitro drug susceptibility testing and the in vivo clinical response indicated that the modified antibiotic susceptibility test is an appropriate method for establishing antibiotic regimens.
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PMID:Modified antimicrobial disc susceptibility testing for nutritionally-variant streptococci. 1211 43

NVS grow in culture media with 0.001% pyridoxal hydrochloride (PHC) and 0.1% cysteine hydrochloride (CysHC). These bacteria need the help of other organisms to grow on common solid media showing the effect known as "satellitism". Both, satellitism and the pyrrolidonilarilamidase test are the key tests for suspecting the presence of NVS. They can grow as a faint haze on blood agar or chocolate agar prepared with the Columbia agar base without adding any other substance. The most frequently documented infections are endocarditis. Among extravascular infections, ocular infections predominate. For antimicrobial susceptibility testing, the Etest and dilution methods with the addition of 0.001% PHC can be used. Whichever the method there does not seem to be much correlation in vitro/ in vivo. The rate of penicillin resistance and the MICs were similar to those observed in viridans group streptococci. Four to six weeks of penicillin plus gentamicin is recommended for the treatment of VNS endocarditis. In cases of treatment failure or beta-lactam allergic susceptibility, vancomycin alone or with the addition of gentamicin and/or rifampin is used.
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PMID:[Abiotrophia and Granulicatella]. 1715 18

Aggregatibacter (Actinobacillus) actinomycetemcomitans is the causative organism of localized aggressive periodontitis, a rapidly progressing degenerative disease of the gingival and periodontal ligaments, and is also implicated in causing subacute infective endocarditis in humans. The bacterium produces a variety of virulence factors, including an exotoxic leukotoxin (LtxA) that is a member of the repeats-in-toxin (RTX) family of bacterial cytolysins. LtxA exhibits a unique specificity to macrophages and polymorphonuclear cells of humans and other primates. Human lymphocyte function-associated antigen 1 (LFA-1) has been implicated as the putative receptor for LtxA. Human LFA-1 comprises the CD11a and CD18 subunits. It is not clear, however, which of its subunits serves as the functional receptor that confers species-specific susceptibility to LtxA. Here we demonstrate that the human CD18 is the receptor for LtxA based on experiments performed with chimeric beta2-integrins recombinantly expressed in a cell line that is resistant to LtxA effects. In addition, we show that the cysteine-rich tandem repeats encompassing integrin-epidermal growth factor-like domains 2, 3, and 4 of the extracellular region of human CD18 are critical for conferring susceptibility to LtxA-induced biological effects.
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PMID:Human CD18 is the functional receptor for Aggregatibacter actinomycetemcomitans leukotoxin. 1763 65

Corynebacterium jeikeium is an emerging nosocomial pathogen responsible for vascular catheters infections, prosthetic endocarditis and septicemia. The treatment of C. jeikeium infections is complicated by the multiresistance of clinical isolates to antibiotics, in particular to beta-lactams, the most broadly used class of antibiotics. To gain insight into the mechanism of beta-lactam resistance, we have determined the structure of the peptidoglycan and shown that C. jeikeium has the dual capacity to catalyse formation of cross-links generated by transpeptidases of the d,d and l,d specificities. Two ampicillin-insensitive cross-linking enzymes were identified, Ldt(Cjk1), a member of the active site cysteine l,d-transpeptidase family, and Pbp2c, a low-affinity class B penicillin-binding protein (PBP). In the absence of beta-lactam, the PBPs and the l,d-transpeptidase contributed to the formation of 62% and 38% of the cross-links respectively. Although Ldt(Cjk1) and Pbp2C were not inhibited by ampicillin, the participation of the l,d-transpeptidase to peptidoglycan cross-linking decreased in the presence of the drug. The specificity of Ldt(Cjk1) for acyl donors containing a tetrapeptide stem accounts for this effect of ampicillin since the essential substrate of Ldt(Cjk1) was produced by an ampicillin-sensitive d,d-carboxypeptidase (Pbp4(Cjk)). Acquisition and mutational alterations of pbp2C accounted for high-level beta-lactam resistance in C. jeikeium.
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PMID:The beta-lactam-sensitive D,D-carboxypeptidase activity of Pbp4 controls the L,D and D,D transpeptidation pathways in Corynebacterium jeikeium. 1980 68


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