Table 5.
Comparison of resistant phenotype expression and resistant genotype among Staphylococcus aureus keratitis isolates
| Number of isolates/% of total S. aureus isolates (n=75) | Resistant phenotypic (antibiotic) profilea | Resistant genotypic (genes) profileb | Epidemiologyc | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| ERY | CIP | CLI | GM | MOX | SXT | TET | OX | Resistant determinants | HA | CA | |
| Methicillin-susceptible isolates | |||||||||||
| 12 (16%) | None detected | 3 | 1 | ||||||||
| blaZ | 2 | ||||||||||
| blaZ, fosB | 5 | 1 | |||||||||
| 2 (2.7%) | blaZ, msrA, mphBM, aphA3, sat, mupA, tetK, fosB | 1 | |||||||||
| blaZ, msrA, mphBM, aphA3, sat, fosB | 1 | ||||||||||
| 2 (2.7%) | blaZ, aphA3, sat, tetK, fosB | 2 | |||||||||
| 5 (6.7%) | blaZ | 1 | |||||||||
| blaZ, ermA | 1 | ||||||||||
| blaZ, ermA, fosB | 2 | ||||||||||
| ermC, fosB | 1 | ||||||||||
| 1 (1.3%) | ermA | 1 | |||||||||
| 1 (1.3%) | blaZ, msrA, mphBM, aphA3, sat, fosb | 1 | |||||||||
| 1 (1.3%) | blaZ, ermA, aad, fosB | 1 | |||||||||
| 1 (1.3%) | blaZ, msrA, mphBM, aphA3, sat, mupA, tetK, fosB | 1 | |||||||||
| 1 (1.3%) | ermA, aacA-aphD, aphA3, sat, tetK | 1 | |||||||||
| 1 (1.3%) | ermA, ermC, tetM, fosb | 1 | |||||||||
| 1 (1.3%) | blaZ, msrA, mphBM, aacA-aphD, aph3, sat, dfrA, mupA, tetM, fosB | 1 | |||||||||
| 28 (37.3%) | Total methicillin-susceptible isolates | 26 | 2 | ||||||||
| % Resistant | 46.4% | 17.8% | 32.1% | 7.1% | 17.8% | 3.6% | 21.4% | 0% | % MSSA isolates resistant to three or more antibiotic classes: phenotype, n=5 (17.8%); genotype, n=12 (42.8%) | ||
| MRSA isolates | |||||||||||
| 1 (1.3%) | mecA, blaZ, fosB | 1 | |||||||||
| 2 (6.7%) | mecA, blaZ, msrA, mphBM, aphA3, sat, fosB | 1 | |||||||||
| fosB | 1 | ||||||||||
| 1 (1.3%) | mecA, blaZ, msrA, mphBM, aphA3, sat, fosB | 1 | |||||||||
| 1 (1.3%) | blaZ, fos | 1 | |||||||||
| 5 (6.7%) | fosB | 2 | |||||||||
| mecA, blaZ, msrA, mphBM, aphA3, sat, fosB | 3 | ||||||||||
| 1 (1.3%) | mecA, blaZ, msrA,mphBM, aphA3, fosB | 1 | |||||||||
| 2 (2.7%) | mecA, blaZ, fosB | 2 | |||||||||
| 24 (32%) | ermA, fosB | 2 | |||||||||
| blaZ, ermA, fosB | 2 | ||||||||||
| ermA, aad, fosB | 1 | ||||||||||
| mecA, blaZ, ermA, fosB | 2 | ||||||||||
| mecA, blaZ, ermA, aadD, fosB | 2 | ||||||||||
| mecA, msrA, aac, mupA dfrA, fosB | 1 | ||||||||||
| mecA, blaZ, ermA,, aadD, mupA, fosB | 1 | ||||||||||
| mecA, blaZ, ermA, msrA, aadD, sat, fosB | 1 | ||||||||||
| mecA, blaZ, msrA, mphBM, aphA3, sat, fosB | 2 | ||||||||||
| mecA, blaZ, ermA, msrA, mphBM, aad, mupA, fosB | 1 | ||||||||||
| mecA, blaZ, ermA, msrA, mphBM, aadD, aphA3, sat, fosB | 2 | 2 | |||||||||
| mecA, blaZ, ermA, msrA, mphBM, aadD, mupA, sat, fosB | 1 | ||||||||||
| mecA, blaZ, ermA, msrA, mphBM, aacA-aphD, aph3, sat, fosB | 1 | ||||||||||
| mecA, blaZ, ermA, msrA, mphBM, aadD, aphA3, sat, mupA, fosB | 1 | ||||||||||
| mecA, blaZ, ermA, msrA, mphBM, aadD, aphA3, sat, dfrA, mupA, fosB | 1 | ||||||||||
| 1 (1.3) | mecA ,blaZ, ermC, msrA, mphBM, aphA3, sat, fosB | 1 | |||||||||
| 1 (1.3) | ermA, fosB | 2 | |||||||||
| 1 (1.3 | mecA, blaZ, msrA, mphBM, aphA3, sat, fosB | 1 | |||||||||
| 1 (1.3) | mecA, blaZ, fosB | 1 | |||||||||
| 1 (1.3) | mecA, blaZ, msrA, mphBM, aacA-aphD, aphA3, sat, mupA, tetM, fosB | 1 | |||||||||
| 1 (1.3) | mecA, blaZ, msrA, mphBM, aadD, sat, mupA, fosB | 1 | |||||||||
| 1 (1.3) | mecA, blaZ, msrA, mphBM, aacA-aphD, aphA3, sat, dfrA, mupA, tetM, fosB | 1 | |||||||||
| 1 (1.3) | mecA, fosB | 1 | |||||||||
| 1 (1.3) | mecA, blaZ, msrA, mphBM, aacA-aphD, aphA3, sat, dfrA, mupA, tetM, fosB | 1 | |||||||||
| 1 (1.3%) | blaZ, ermC, fosB | 1 | |||||||||
| 47 (62.7%) | TOTAL | 35 | 12 | ||||||||
| % MRSA resistant | 89.4% | 93.6% | 63.8% | 8.5% | 91.3% | 14.9% | 12.8% | 100% | % MRSA isolates resistant to three or more antibiotic classes Phenotype, n=43 (91.5%); genotype, 39 (83.0%) | ||
| % Resistant All isolates (n=75) | 73.3% | 65.3% | 63.8% | 8.0% | 63.5% | 10.7% | 16.0% | 62.7% | % of all S. aureus isolates resistant to three or more antibiotic classes: Phenotype, n=48 (64%); genotype, n=51 (68%) | ||
Notes: Comparative profiles were available for eight antibiotics/pairs. These included ciprofloxacin, clindamycin, erythromycin, gentamicin, moxifloxacin, trimethoprim-sulfamethoxazole, tetracycline and oxacillin. Among the resistant group, agreement ranged from 76% for methicillin to 97.6% for gentamicin. No isolates were resistant to linezolid and/or vancomycin by phenotype and/or by the presence of resistant genes.
Resistant phenotypic profile:
Resistant genotypic profile:
HA, healthcare associated. Phenotypic resistant pattern key:
Abbreviations: CIP, ciprofloxacin, CLI, clindamycin; ERY, erythromycin; GM, gentamicin; MOX, moxifloxacin; OX, oxacillin; SXT, trimethoprim sulfamethoxazole; TET, tetracycline; aacA-aphD, aminoglycoside modifying bifunctional-adenylphosphotransferase enzyme includes both intermediate and resistant isolates (gentamicin, tobramycin); aadD, aminoglycoside adenyltransferase enzymes (neomycin, kanamycin, and/or tobramycin); aphA3, bifunctional aminoglycoside phosphotransferase, modifying enzyme (neomycin kanamycin); blaZ, beta-lactamase gene (penicillins); dfrA, dihydrofolate reductase mediating trimethoprim resistance; ermA, rRNA methyltransferase associated with macrolide/lincosamide resistance; ermC, rRNA methyltransferase associated with macrolide/lincosamides resistance; fosB, metallothiol transferase (fosfomycin B); mecA, penicillin binding protein 2a (an SCC element resistance to most beta-lactams); MRSA, methicillin-resistant S. aureus; mpbBM, macrolide phosphotransferase II; mrsA, macrolide efflux pump; mupR, isoleucyl-tRNA synthetase associated with mupirocin resistance; sat, streptothricin acetyltransferase; tetK, tetracycline efflux protein, and tetM, ribosomal protection protein associated with tetracycline resistance; CA, community associated.