HACEK Infections – Etiology, pathophysiology, symptoms, signs, diagnosis & prognosis from the MSD Manuals – Medical Professional Version. The “HACEK” organisms are a group of fastidious Gram-negative bacteria that cause a variety of infections, including infective endocarditis. Antimicrobial. Hacek. 1. Dr Vishal Kulkarni MBBS MD (Microbiology); 2. The acronym HACEK refers to a group of fastidious slow growing bacteria.

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Antimicrobial susceptibility testing is not universally available, and therapy for these infections is often empirical.

All isolates were susceptible to ceftriaxone and levofloxacin, indicating that these agents remain appropriate empirical choices for the treatment of infections with this group of organisms.

These organisms are normal flora of the human oral cavity, but are capable of causing disease, most notably infective endocarditis IEbut also periodontal infections, abscesses, and nonendocarditis bacteremia secondary to focal gruupo. Therefore, therapy is often chosen bactefias based on published reports and guidelines. The recommended treatment of IE due to these organisms is therefore a broad-spectrum cephalosporin or a fluoroquinolone.

This is based on limited data due to the clinical rarity of infections by these organisms. Of those, 49 isolates were submitted for identification only and 18 isolates were recovered from autopsy specimens, which do not routinely undergo susceptibility testing.

Baccterias remaining isolates were submitted for identification and susceptibility testing. Isolates were identified using either traditional biochemical tests or the 16S rRNA molecular assay 5.


After 48 h of incubation, results were interpreted using batcerias published by CLSI 6. Of isolates, Among the isolates with successful susceptibility testing, the most common isolates were H. Two isolates each of C. Blood isolates accounted for The MICs of 18 antimicrobial agents for 70 isolates are summarized in Table 1.


No isolates were resistant to amoxicillin-clavulanic acid, ceftriaxone, meropenem, levofloxacin, or chloramphenicol based on CLSI breakpoints Table 1. Clarithromycin and penicillin were the least active agents, with Resistance to imipenem, sulfamethoxazole-trimethoprim, ampicillin, and tetracycline was also observed. Notably, two isolates—one pleural fluid isolate of H. The penicillin with the greatest in vitro activity was amoxicillin-clavulanic acid.

Ceftriaxone was active against all isolates and was also the most potent cephalosporin MIC 900.

Group A Beta-hemolytic Streptococcus

Meropenem was more active and more potent than imipenem. Levofloxacin and chloramphenicol were universally active. Resistance was most frequently observed bacteias Aggregatibacter and Haemophilus species. Six of 13 Aggregatibacter species were resistant bacteriqs at least one agent, and 3 of 13 were resistant to at least two agents. Twenty-five of 37 Haemophilus isolates were intermediate or resistant to at least one agent, and 16 were intermediate or resistant to more than one agent.

HACEK organisms

Of the remaining 20 isolates, one Eikenella isolate was resistant to ampicillin and penicillin. The two Cardiobacterium isolates and a single Kingella isolate were susceptible to all tested antimicrobials. From this data set, the following observations can be made.

Our data are most robust for isolates of AggregatibacterHaemophilusand Eikenellasince only a limited number of Cardiobacterium and Kingella isolates were tested. Since the fastidiousness of HACEK organisms makes resistance testing impractical for many laboratories, and isolates commonly fail susceptibility testing, published reports and guidelines frequently provide the only guidance for antimicrobial selection 1 — 3.


The high failure rate for susceptibility results among these organisms also indicates that current recommended susceptibility methods may not be optimal. Our findings confirm that the use of broad-spectrum cephalosporins and fluoroquinolones remains vacterias for this group of organisms. Published ahead of print 12 February National Center for Biotechnology InformationU.

HACEK organisms – Wikipedia

Journal List Antimicrob Agents Chemother v. Jamiesona, d David J. Farrella, d and Samir N. Author information Article notes Copyright and License information Disclaimer. Address correspondence to Samir N. This article has been cited by other articles in PMC. Open bacteriias a separate window.

Results for drugs to which all bacteria were susceptible S have been highlighted in boldface. Footnotes Published ahead of print 12 February Guidelines for the diagnosis and antibiotic treatment of endocarditis in adults: Guidelines on the prevention, diagnosis, and treatment of infective endocarditis new version Determination of the antimicrobial activity of 29 clinically important compounds tested against fastidious HACEK group organisms.

Clinical and Laboratory Standards Institute Methods for antimicrobial dilution and disk susceptibility testing of infrequently isolated or fastidious bacteria.

Clinical features of patients with invasive Eikenella corrodens infections and microbiological characteristics of the causative isolates. Antibiotic susceptibility of Kingella kingae isolates from respiratory carriers and patients with invasive infections.

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