Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical Mastitis
The objective of this study was to compare the minimum inhibitory concentrations of antimicrobials included in a commercial broth microdilution panel among Gram-positive pathogens that caused non-severe clinical mastitis on three Michigan dairy farms. Duplicate quarter milk samples were collected fr...
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MDPI AG
2024-01-01
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| Series: | Antibiotics |
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| Online Access: | https://www.mdpi.com/2079-6382/13/1/91 |
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| author | Quinn K. Kolar Juliano L. Goncalves Ronald J. Erskine Pamela L. Ruegg |
| author_facet | Quinn K. Kolar Juliano L. Goncalves Ronald J. Erskine Pamela L. Ruegg |
| author_sort | Quinn K. Kolar |
| collection | DOAJ |
| description | The objective of this study was to compare the minimum inhibitory concentrations of antimicrobials included in a commercial broth microdilution panel among Gram-positive pathogens that caused non-severe clinical mastitis on three Michigan dairy farms. Duplicate quarter milk samples were collected from eligible quarters of cows enrolled in a randomized clinical trial, cultured in a university laboratory, and identified using MALDI-TOF. Etiologies were grouped by genus as <i>Enterococcus</i> species (n = 11), <i>Lactococcus</i> species (n = 44), non-aureus <i>Staphylococcus</i> species (n = 39), or <i>Streptococcus</i> species (n = 25). Minimum inhibitory concentrations (MICs) were determined using the mastitis panel of a commercially available broth microdilution test. In vitro susceptibility was determined using approved guidelines and included breakpoints for mastitis pathogens, or when not available, breakpoints from other species. Most isolates were inhibited at or below breakpoints that demonstrated in vitro susceptibility. The proportions of susceptible isolates varied among pathogens for pirlimycin, penicillin, and tetracycline. The greatest proportion of resistance was observed for pirlimycin, tetracycline, and sulfadimethoxine. Survival analysis was performed to evaluate differences in MICs among pathogen groups. MIC values varied among pathogens for ceftiofur, cephalothin, erythromycin, penicillin, pirlimycin, and tetracycline. However, nearly all isolates were susceptible to ceftiofur and cephalothin, indicating that pathogen differences in MIC are not likely clinically relevant, as these are the two most commonly administered mastitis treatments in the United States. While differences in vitro susceptibility were observed for some antimicrobials, susceptibility was high to cephalosporin-based IMM treatments that are most commonly used and did not vary among pathogens. |
| first_indexed | 2024-03-08T11:07:25Z |
| format | Article |
| id | doaj.art-940ed70976e64faab9fbec026e6117aa |
| institution | Directory Open Access Journal |
| issn | 2079-6382 |
| language | English |
| last_indexed | 2024-03-08T11:07:25Z |
| publishDate | 2024-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Antibiotics |
| spelling | doaj.art-940ed70976e64faab9fbec026e6117aa2024-01-26T14:38:42ZengMDPI AGAntibiotics2079-63822024-01-011319110.3390/antibiotics13010091Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical MastitisQuinn K. Kolar0Juliano L. Goncalves1Ronald J. Erskine2Pamela L. Ruegg3Department of Animal Science, Michigan State University, East Lansing, MI 48824, USADepartment of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USADepartment of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USADepartment of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USAThe objective of this study was to compare the minimum inhibitory concentrations of antimicrobials included in a commercial broth microdilution panel among Gram-positive pathogens that caused non-severe clinical mastitis on three Michigan dairy farms. Duplicate quarter milk samples were collected from eligible quarters of cows enrolled in a randomized clinical trial, cultured in a university laboratory, and identified using MALDI-TOF. Etiologies were grouped by genus as <i>Enterococcus</i> species (n = 11), <i>Lactococcus</i> species (n = 44), non-aureus <i>Staphylococcus</i> species (n = 39), or <i>Streptococcus</i> species (n = 25). Minimum inhibitory concentrations (MICs) were determined using the mastitis panel of a commercially available broth microdilution test. In vitro susceptibility was determined using approved guidelines and included breakpoints for mastitis pathogens, or when not available, breakpoints from other species. Most isolates were inhibited at or below breakpoints that demonstrated in vitro susceptibility. The proportions of susceptible isolates varied among pathogens for pirlimycin, penicillin, and tetracycline. The greatest proportion of resistance was observed for pirlimycin, tetracycline, and sulfadimethoxine. Survival analysis was performed to evaluate differences in MICs among pathogen groups. MIC values varied among pathogens for ceftiofur, cephalothin, erythromycin, penicillin, pirlimycin, and tetracycline. However, nearly all isolates were susceptible to ceftiofur and cephalothin, indicating that pathogen differences in MIC are not likely clinically relevant, as these are the two most commonly administered mastitis treatments in the United States. While differences in vitro susceptibility were observed for some antimicrobials, susceptibility was high to cephalosporin-based IMM treatments that are most commonly used and did not vary among pathogens.https://www.mdpi.com/2079-6382/13/1/91antibioticsmastitisGram-positivedairy |
| spellingShingle | Quinn K. Kolar Juliano L. Goncalves Ronald J. Erskine Pamela L. Ruegg Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical Mastitis Antibiotics antibiotics mastitis Gram-positive dairy |
| title | Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical Mastitis |
| title_full | Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical Mastitis |
| title_fullStr | Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical Mastitis |
| title_full_unstemmed | Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical Mastitis |
| title_short | Comparison of Minimum Inhibitory Concentrations of Selected Antimicrobials for Non-Aureus <i>Staphylococci</i>, <i>Enterococci</i>, <i>Lactococci</i>, and <i>Streptococci</i> Isolated from Milk Samples of Cows with Clinical Mastitis |
| title_sort | comparison of minimum inhibitory concentrations of selected antimicrobials for non aureus i staphylococci i i enterococci i i lactococci i and i streptococci i isolated from milk samples of cows with clinical mastitis |
| topic | antibiotics mastitis Gram-positive dairy |
| url | https://www.mdpi.com/2079-6382/13/1/91 |
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