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HACEK group endocarditis at the Riyadh Armed Forces Hospital.

INTRODUCTION: Fastidious Gram-negative organisms classified as the HACEK group (Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens and Kingella spp.) are rare causes of infective endocarditis. CASE REPORT: In this series, we report six cases of endocarditis in Saudi patients occurring between 1990 and 1994 in our hospital, caused by two of the organisms in the HACEK group, i.e. Cardiobacterium hominis and Actinobacillus actinomycetemcomitans. The clinical features, predisposing factors and treatment of the patients are briefly described. The microscopic and cultural characteristics of the organisms are described together with the laboratory methods of diagnosis. MAJOR FINDINGS: HACEK endocarditis was frequently associated with prosthetic heart valves or structural heart abnormalities. Dental caries or periodontal disease seems to be a predisposing factor. The prognosis of HACEK endocarditis is very good as clinical and bacteriological cure were achieved with antibiotic therapy in all our cases except one who required mitral valve replacement. Contrary to previous reports we did not find all the organisms sensitive to penicillin and aminoglycosides. However, all our isolates were sensitive to amoxycillin, cefuroxime, ceftriaxone and ciprofloxacin. CONCLUSIONS: Laboratory diagnosis of HACEK group of organisms requires a high index of suspicion and should be suspected in cases of endocarditis in which fastidious Gram-negative coccobacilli are isolated which fail to grow on MacConkey agar. Empiric therapy should be started in suspected cases with second generation cephalosporins or with ciprofloxacin, until antibiotic sensitivity results become available. Antibiotic therapy should be continued for 4-6 weeks. Progress and outcome was very good in the series.

Actinobacillus Infections↗

The role of 16S rRNA gene sequencing in identification of microorganisms misidentified by conventional methods.

Traditional methods for microbial identification require the recognition of differences in morphology, growth, enzymatic activity, and metabolism to define genera and species. Full and partial 16S rRNA gene sequencing methods have emerged as useful tools for identifying phenotypically aberrant microorganisms. We report on three bacterial blood isolates from three different College of American Pathologists-certified laboratories that were referred to ARUP Laboratories for definitive identification. Because phenotypic identification suggested unusual organisms not typically associated with the submitted clinical diagnosis, consultation with the Medical Director was sought and further testing was performed including partial 16S rRNA gene sequencing. All three patients had endocarditis, and conventional methods identified isolates from patients A, B, and C as a Facklamia sp., Eubacterium tenue, and a Bifidobacterium sp. 16S rRNA gene sequencing identified the isolates as Enterococcus faecalis, Cardiobacterium valvarum, and Streptococcus mutans, respectively. We conclude that the initial identifications of these three isolates were erroneous, may have misled clinicians, and potentially impacted patient care. 16S rRNA gene sequencing is a more objective identification tool, unaffected by phenotypic variation or technologist bias, and has the potential to reduce laboratory errors.

Bacterial Typing Techniques↗

[Detection of bacterial molecular markers in the tissue of cardiac valves in normal and pathological states by gas chromatography and mass spectrometry].

Samples from cardiac valves of 31 patients were analyzed by gas chromatography and mass spectrometry. The algorithm of mass spectrometric parameters was developed, which permitted the determination of about 200 known microbial fatty acids, aldehydes and sterols, sufficient for the detection and quantitative determination of more that 170 taxons of clinically significant microorganisms on the genus or species levels. The quantitative and qualitative differences in the composition of microbial markers of endocardial valves in normal and pathological states, particularly in cases of infectious endocarditis, were detected. The participation of 37 microbial taxons in the process was confirmed. The level of endocardium colonization in infectious endocarditis reached from 2 to 7 x 10(9) microbial cells/g of valvular tissue (which exceeded twofold the equivalent concentrations of the marker in the normal state). In terms of quantity, the leading role was played by Cardiobacterium hominis.

Adolescent↗

Rapid identification of Capnocytophaga isolated from septicemic patients.

Four Capnocytophaga strains from blood cultures of immunocompromised patients with malignant disease and the type strains of three Capnocytophaga species were examined and compared to strains representing five other genera that are hard to differentiate from Capnocytophaga. With three rapid identification methods, negative catalase and oxidase reactions and positive ONPG assay, Capnocytophaga was easily separated from Eikenella corrodens, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, and CDC group DF-2. Haemophilus aphrophilus was excluded by leucine, valine and cystine arylamidase and alpha-glucosidase reactions (API ZYM). Further confirmatory reactions constituted gelatin hydrolysis, haemin requirement, and carbohydrate and esculin breakdown. Although rapid identification of Capnocytophaga to the genus level was feasible, differentiation on a species level proved impossible.

Capnocytophaga↗

Increased frequency of isolation of Pasteurella and Actinobacillus species and related organisms.

Ninety-six clinical isolates of Pasteurella, Actinobacillus and related organisms were submitted to our reference laboratory for identification. The procedures for detecting the 11 identified species, Pasteurella multocida, Pasteurella haemolytica, Pasteurella ureae, Pasteurella pneumotropica, Actinobacillus lignieresii, Actinobacillus equuli, Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Cardiobacterium hominis, and two unnamed species of CDC groups, HB-5 and EF-4, are described and their clinical importance is discussed. These organisms have been increasingly isolated in Japan and are most often associated with respiratory infections and endocarditis.

Actinobacillus↗

Application of quadFERM+ for the identification of fastidious gram-positive and gram-negative bacilli.

The 2-hr quadFERM+ kit (qF) (Analytab Products, Plainview, NY) was compared with conventional tube tests for the identification of the HACEK bacteria (Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae), other Haemophilus and Kingella spp., Capnocytophaga, Corynbacterium, and Moraxella spp. Test results were identical for 296 comparisons with 74 isolates (74%). In the remaining 104 comparisons for 26 isolates, 50 reactions were identical, and qF produced a positive result in 46 of 54 discrepancies.

Actinobacillus↗

Bilateral endogenous endophthalmitis caused by HACEK microorganism.

PURPOSE: To report a case of bilateral endogenous endophthalmitis caused by a HACEK group organism (Actinobacillus actinomycetemcomitans). METHODS: An 85-year-old Caucasian female presented with bilateral light perception visual acuity, anterior chamber cells, hypopyon, posterior synechiae, and no red reflex. RESULTS: The patient underwent bilateral vitrectomy, with topical, intravitreal, and systemic antibiotics. Vitreous cultures revealed gram-negative cocco bacilli consistent with Actinobacillus actinomycetemcomitans. At final follow-up, visual acuity was 20/25 RE and 20/40 LE. CONCLUSIONS: Prompt diagnosis and treatment of HACEK [Hemophilus sp. (parainfluenzae, aphrophilus, paraphrophilus), Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corodens, and Kingella kingae] group bacterial endophthalmitis can yield good results.

Actinobacillus Infections↗

Determination of the antimicrobial activity of 29 clinically important compounds tested against fastidious HACEK group organisms.

HACEK group organisms are very fastidious organisms (Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominus, Eikenella corrodens, Kingella spp.) that can produce serious invasive infections such as endocarditis. Problems with susceptibility testing methods and their rarity of isolation limit available information of therapeutic choices, particularly among newer antimicrobial agents. Forty-two HACEK strains were tested by the Etest (AB BIODISK, Solna, Sweden) method against 29 antimicrobial agents. Nearly all compounds exhibited activity with best potency observed among the tested beta-lactamase inhibitor combinations, "third- or fourth-generation" cephems, meropenem, fluoroquinolones, and rifampin. Numerous therapeutic options appear possible for initial parenteral treatment followed by oral "step-down" or switch therapy. Each case of HACEK infection therapy should be guided by accurate susceptibility tests, for which the Etest seems preferred for these fastidious species.

Anti-Bacterial Agents↗

Prolonged incubation and extensive subculturing do not increase recovery of clinically significant microorganisms from standard automated blood cultures.

An extensive blood culture protocol, including prolonged incubation of cultures, for 215 patients believed to have had endocarditis yielded only 3 clinically relevant results. Twenty-four Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella (i.e., HACEK) organisms were recovered from standard 5-day blood cultures during the same time period. Specialized methods and not extended incubation times are recommended for recovery of fastidious agents of septicemia.

Bacteremia↗

New consensus guidelines from the Clinical and Laboratory Standards Institute for antimicrobial susceptibility testing of infrequently isolated or fastidious bacteria.

The Clinical and Laboratory Standards Institute (CLSI) recently published a new laboratory guideline for antimicrobial susceptibility testing of infrequently encountered or fastidious bacteria not covered in previous CLSI publications. The organisms include Aeromonas species, Bacillus species, and Vibrio species that may cause infections following environmental exposure. Fastidious organisms that may cause endocarditis or medical device infections include Abiotrophia and Granulicatella species; coryneform bacteria; Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella group gram-negative rods; and the instrinsically vancomycin-resistant gram-positive organisms Erysipelothrix, Lactobacillus, Leuconostoc, and Pediococcus species. Organisms not previously covered in depth in CLSI guidelines include Branhamella catarrhalis, Campylobacter jejuni, Campylobacter coli, Listeria species, and Pasteurella species. Clinically important drug resistance has been reported for each of these organisms. The guidelines provide recommendations for when it may be important to test these organisms, how standard methods may be easily adapted for testing, and appropriate interpretive criteria for results. Communication with infectious diseases clinicians prior to performing such testing is emphasized.

Anti-Bacterial Agents↗

Use of corticosteroids in glomerulonephritis related to infective endocarditis: three cases and review.

We report the cases of three patients treated for infective endocarditis (IE) for whom corticosteroids were added to the antibiotic treatment. They all had clinical and biological evidence of immune-mediated glomerulonephritis. The microorganisms responsible for IE were Coxiella burnetii, Streptococcus bovis, and Cardiobacterium hominis. Median duration of IE before antimicrobial therapy was 7 months. In all patients, renal function deteriorated despite appropriate antimicrobial treatment for a mean duration of 16 days, but it improved after addition of corticosteroid therapy. All patients were cured of IE. A literature review revealed four additional cases of IE-related glomerulonephritis in which adjunctive immunosuppressive therapy was considered to be effective. Although corticosteroid therapy is generally not recommended for IE, it should be considered for patients whose renal dysfunction secondary to glomerulonephritis does not improve with appropriate antimicrobial treatment, especially if the duration of the illness is long.

Aged↗