The Peanuts Sign : A Novel Clue to the Rapid Discrimination of Penicillin-susceptible Enterococci Based on Gram Staining Findings

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  • 腸球菌のペニシリン感受性をグラム染色所見の「落花生サイン」で推定
  • チョウ キュウキン ノ ペニシリン カンジュセイ オ グラム センショク ショケン ノ 「 ラッカセイ サイン 」 デ スイテイ

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<p>When an enterococcal infection is strongly suspected, intravenous vancomycin is generally selected for the initial treatment. Vancomycin is administered for a few days, at which time susceptibility testing often indicates penicillin-susceptible enterococci, leading to unnecessary adverse reactions and the development of antibiotic-resistant bacteria. In cases of penicillin-susceptible Enterococcus faecalis bacteremia, where treatment has been performed with vancomycin, a higher mortality rate has resulted than in cases treated with penicillin.<BR> To solve these problems, a method capable of rapidly identifying a penicillin susceptible strain is desired ; however, mass spectrometry or genetic testing is expensive and requires proficiency, and many hospitals comprise different subjects. Therefore, we devised a method to rapidly identify the penicillin susceptibility of enterococci by observing what we refer to as the “peanut sign”, based on Gram staining.<BR> Microscopic testing was performed on blood culture-positive gram-stained specimens. Gram-positive diplococci without a capsule with pointed elliptical ends were presumed to be enterococci. The enterococci with a peanut shell-like symmetrical notch present in the center of the bacterial cell on both sides were defined as having the “peanut sign”. We evaluated the results for microscopic testing and penicillin-susceptibility testing of enterococci between a medical technologist, who performs microscopic testing on a daily basis and a physician, who does not.<BR> In the microscopic examination by the physician, the “peanut sign”returned a sensitivity of 78% and specificity of 96% to penicillin-resistant enterococci. In the microscopic examination by the medical technologist, the sensitivity was 94% and specificity was 78%. The kappa coefficient was 0.62, indicating “substantial agreement” between the findings of the physician and medical technologist.<BR> Penicillin-susceptible enterococci can be rapidly identified by Gram staining results, with a substantial agreement noted for inter-rater reliability.<BR> If a patientʼs condition is not urgent, then optimal antibiotics can be selected in real-time, either penicillin or vancomycin depending on positive or negative presence of the “peanut sign”. This may assist with appropriate administration of antimicrobials, maximizing therapeutic efficacy, minimizing the risk of unnecessary adverse reactions and preventing the development of antibiotic-resistant bacteria.</p>

Journal

  • Kansenshogaku Zasshi

    Kansenshogaku Zasshi 93 (3), 306-311, 2019-05-20

    The Japanese Association for Infectious Diseases

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