Aerococcus urinae and Aerococcus sanguinicola: Susceptibility Testing of 120 Isolates to Six Antimicrobial Agents Using Disk Diffusion (EUCAST), Etest, and Broth Microdilution Techniques

Abstract

Background: Aerococcus urinae and Aerococcus sanguinicola are relatively newcomers and emerging organisms in clinical and microbiological practice. Both species have worldwide been associated with urinary tract infections. More rarely cases of bacteremia/septicemia and infective endocarditis have been reported. Treatment options are therefore important. Just recently, European recommendations on susceptibility testing and interpretive criteria have been released.Objective:In this investigation 120 A. urinae and A. sanguinicola isolates were tested for susceptibility to six antimicrobial agents: Penicillin, cefotaxime, meropenem, vancomycin, linezolid, and rifampicin.Methods:Three susceptibility testing methods were used; disk diffusion according to The European Committee on Antimicrobial Susceptibility Testing (EUCAST) standardized disk diffusion methodology and MIC determination with Etest and broth microdilution (BMD). All testing was performed with EUCAST media for fastidious organisms.Results:Data obtained in this study were part of the background data for establishing EUCAST breakpoints. MIC values obtained by Etest and BMD were well correlated with disk diffusion results.Conclusion:All isolates were found susceptible to all six antimicrobial agents: penicillin, cefotaxime, meropenem, vancomycin, linezolid, and rifampicin.

The clinical relevance of pathogen Aerococcus urinae identification by MALDI-TOF mass spectrometry: a case of sepsis in 86-year-old Caucasian male

“…In addition to the obvious clinical impact for patients, the correct identification of A. urinae might also permit to perform accurate studies on antibiotic sensitivities of this species (1,6). Reviewing in vitro studies, variable resistance to clindamycin, erythromycin, and levofloxacin, and sensitivity to amoxicillin, cefotaxime, ceftriaxone, doxycycline, linezolid, meropenem, penicillin, rifampin, and vancomycin were observed (1,4,6). In our case, A. urinae isolates are completely sensitive to all antibiotic tested.…”

“…Although genetic approaches like 16S rRNA sequencing are the gold standard for aerococci identification, they are expensive and require trained personnel (1,11). The introduction of MALDI-TOF MS in routine laboratories as the primary technique for species determination overcame most of the limits of aerococci identification (1,4,(6)(7)(8)(9)12). The aim of this case report is to highlight the clinical importance of MALDI-TOF MS in aerococcus identification, thus revealing the true incidence of this microorganism.…”

“…Risk factors include elderly male subjects and comorbidities associated to genitourinary tract (1,3). The incidence of human infections caused by this pathogen is however underestimated since the identification of aerococci often fails due to the colony morphology and microscopic appearance in Gram-stain similar to staphylococci, and to the antibiotic resistance patterns similar to those of enterococci (1,3,4). Moreover, a variety of common diagnostic systems based on biochemical reactions do not recognize aerococci, thus increasing the misidentification in many laboratories world-wide (1,5).…”

“…Moreover, a variety of common diagnostic systems based on biochemical reactions do not recognize aerococci, thus increasing the misidentification in many laboratories world-wide (1,5). However, the introduction of MALDI-TOF MS and genetic techniques as 16S ribosomal subunit sequencing for bacteria identification in diagnostic microbiological laboratories has increased the frequency of detection of infections caused by A. urinae in human (1,3,4,(6)(7)(8)(9).…”

Emerging Presence of Culturable Microorganisms in Clinical Samples of the Genitourinary System: Systematic Review and Experience in Specialized Care of a Regional Hospital

“…were published by EUCAST in 2017 [ 30 ] and by CLSI in 2015 [ 31 ]. This genus is usually susceptible to beta-lactams, the antibiotic of choice, and to vancomycin, which is reserved for allergic patients in combination with gentamycin [ 32 ]. However, A. viridans has elevated minimum inhibitory concentration (MIC) values for penicillin and aminoglycosides, and resistance to vancomycin has been reported [ 33 , 34 ].…”