Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in Enterobacterales
<b>Background</b>: The increasing incidence of infection with Gram-negative bacilli (GNB) producing broad-spectrum β-lactamases, such as extended-spectrum β-lactamases (ESBLs), cephalosporinases (AmpCs), and carbapenemases, has become a great clinical concern. AmpCs are found in many cli...
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MDPI AG
2025-06-01
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| Series: | Antibiotics |
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| author | Edgar-Costin Chelaru Andrei-Alexandru Muntean Mădălina-Maria Muntean Mihai-Octav Hogea Costin-Ștefan Caracoti Bogdan-Florin Ciomaga Thierry Naas Mircea Ioan Popa |
| author_facet | Edgar-Costin Chelaru Andrei-Alexandru Muntean Mădălina-Maria Muntean Mihai-Octav Hogea Costin-Ștefan Caracoti Bogdan-Florin Ciomaga Thierry Naas Mircea Ioan Popa |
| author_sort | Edgar-Costin Chelaru |
| collection | DOAJ |
| description | <b>Background</b>: The increasing incidence of infection with Gram-negative bacilli (GNB) producing broad-spectrum β-lactamases, such as extended-spectrum β-lactamases (ESBLs), cephalosporinases (AmpCs), and carbapenemases, has become a great clinical concern. AmpCs are found in many clinically relevant Enterobacterales, where they may compromise the effectiveness of most β-lactams, including carbapenems when associated with an impaired outer membrane. Detection and distinction between these resistance mechanisms are crucial for antimicrobial therapy and for implementation of proper infection control procedures to prevent further spread. <b>Methods</b>: The disk diffusion antibiogram using Mueller-Hinton agar (MHA) supplemented with cloxacillin (MHC), which inhibits AmpCs, was validated to identify AmpC-producing Enterobacterales (AmpC-PE). As cloxacillin is not available in several countries, we investigated the use of oxacillin as an alternative compound to inhibit AmpCs. The ability of MHA supplemented with oxacillin (MHO) to distinguish between carbapenem-resistant Enterobacterales (CREs) due to AmpC hyperproduction and the presence of a carbapenemase has particularly been investigated. <b>Results</b>: MHOs containing several concentrations of oxacillin were compared to MHA and MHC containing 250 mg/L cloxacillin (MHC250). A set of well-characterized Enterobacterales with different β-lactam resistance mechanisms were evaluated. MHO containing 300 mg/L of oxacillin (MHO300) gave similar results to MHC250. <b>Conclusions</b>: The use of MHO300 proved to be efficient in inhibiting AmpCs, allowing differentiation between AmpC hyperproducers and carbapenemase producers. In addition, the use of MHO300 allowed detection of resistance mechanisms hidden by AmpCs, such as ESBLs. |
| format | Article |
| id | doaj-art-4d2f4d1df3744be19f68695bda637c07 |
| institution | Kabale University |
| issn | 2079-6382 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
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| series | Antibiotics |
| spelling | doaj-art-4d2f4d1df3744be19f68695bda637c072025-08-20T03:26:15ZengMDPI AGAntibiotics2079-63822025-06-0114661610.3390/antibiotics14060616Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in EnterobacteralesEdgar-Costin Chelaru0Andrei-Alexandru Muntean1Mădălina-Maria Muntean2Mihai-Octav Hogea3Costin-Ștefan Caracoti4Bogdan-Florin Ciomaga5Thierry Naas6Mircea Ioan Popa7Discipline of Microbiology II, Department 2, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, 020021 Bucharest, RomaniaDiscipline of Microbiology II, Department 2, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, 020021 Bucharest, RomaniaDiscipline of Microbiology II, Department 2, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, 020021 Bucharest, RomaniaDiscipline of Microbiology II, Department 2, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, 020021 Bucharest, RomaniaDiscipline of Microbiology II, Department 2, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, 020021 Bucharest, RomaniaDiscipline of Microbiology II, Department 2, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, 020021 Bucharest, RomaniaTeam Resist UMR1184 Immunology of Viral, Auto-Immune, Hematological and Bacterial Diseases (IMVA-HB), INSERM, Faculty of Medicine, CEA, LabEx LERMIT, Université Paris-Saclay, 94270 Le Kremlin-Bicêtre, FranceDiscipline of Microbiology II, Department 2, Faculty of Medicine, Carol Davila University of Medicine and Pharmacy, 020021 Bucharest, Romania<b>Background</b>: The increasing incidence of infection with Gram-negative bacilli (GNB) producing broad-spectrum β-lactamases, such as extended-spectrum β-lactamases (ESBLs), cephalosporinases (AmpCs), and carbapenemases, has become a great clinical concern. AmpCs are found in many clinically relevant Enterobacterales, where they may compromise the effectiveness of most β-lactams, including carbapenems when associated with an impaired outer membrane. Detection and distinction between these resistance mechanisms are crucial for antimicrobial therapy and for implementation of proper infection control procedures to prevent further spread. <b>Methods</b>: The disk diffusion antibiogram using Mueller-Hinton agar (MHA) supplemented with cloxacillin (MHC), which inhibits AmpCs, was validated to identify AmpC-producing Enterobacterales (AmpC-PE). As cloxacillin is not available in several countries, we investigated the use of oxacillin as an alternative compound to inhibit AmpCs. The ability of MHA supplemented with oxacillin (MHO) to distinguish between carbapenem-resistant Enterobacterales (CREs) due to AmpC hyperproduction and the presence of a carbapenemase has particularly been investigated. <b>Results</b>: MHOs containing several concentrations of oxacillin were compared to MHA and MHC containing 250 mg/L cloxacillin (MHC250). A set of well-characterized Enterobacterales with different β-lactam resistance mechanisms were evaluated. MHO containing 300 mg/L of oxacillin (MHO300) gave similar results to MHC250. <b>Conclusions</b>: The use of MHO300 proved to be efficient in inhibiting AmpCs, allowing differentiation between AmpC hyperproducers and carbapenemase producers. In addition, the use of MHO300 allowed detection of resistance mechanisms hidden by AmpCs, such as ESBLs.https://www.mdpi.com/2079-6382/14/6/616oxacillincloxacillinAmpCEnterobacteralesMueller-Hinton agardisk diffusion antibiogram |
| spellingShingle | Edgar-Costin Chelaru Andrei-Alexandru Muntean Mădălina-Maria Muntean Mihai-Octav Hogea Costin-Ștefan Caracoti Bogdan-Florin Ciomaga Thierry Naas Mircea Ioan Popa Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in Enterobacterales Antibiotics oxacillin cloxacillin AmpC Enterobacterales Mueller-Hinton agar disk diffusion antibiogram |
| title | Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in Enterobacterales |
| title_full | Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in Enterobacterales |
| title_fullStr | Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in Enterobacterales |
| title_full_unstemmed | Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in Enterobacterales |
| title_short | Oxacillin-Supplemented Mueller-Hinton Agar for In Vitro Inhibition of Ambler Class C β-Lactamases in Enterobacterales |
| title_sort | oxacillin supplemented mueller hinton agar for in vitro inhibition of ambler class c β lactamases in enterobacterales |
| topic | oxacillin cloxacillin AmpC Enterobacterales Mueller-Hinton agar disk diffusion antibiogram |
| url | https://www.mdpi.com/2079-6382/14/6/616 |
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