🏽 Medium: Mueller-Hinton agar
🏽 Inoculum: 0.5 McFarland.
🏽 Incubation: Normal atmosphere, 35±2ºC, 20±4H.
◉ Antibiotics are divided into two separate lists :
Standard list
Cefoxitin (screening), Gentamicin, Erythromycin, Clindamycin, Quinupristin-dalfopristin, Norfloxacin (screening), Fluoroquinolone, Linezolid, fusidic acid, Cotrimoxazole, Rifampicin.
Complementary list
Penicillin G, Oxacillin, Ceftaroline, Ceftobiprole, Vancomycin, Teicoplanin, Kanamycin, Tobramycin, Netilmicin, Trimethoprim, Chloramphenicol, Tetracycline, minocycline, Eravacycline, tigecycline, Tedizolid, Nitrofurantoin, Daptomycin, Mupirocin, Fosfomycin.
Antibiotics are divided into 4 distinct groups, A, B, C and U, approved by the United States Food and Drug Administration for clinical use:
Group A
Azithromycin or clarithromycin or erythromycin, Clindamycin, Oxacillin, Cefoxitin (substitute test for oxacillin), Penicillin, Trimethoprim-sulfamethoxazole.
Group B
Ceftaroline, Daptomycin, Linezolid, Tedizolid, Doxycycline, Minocycline, Tetracycline, Vancomycin, Rifampin.
Group C
Chloramphenicol, Ciprofloxacin or Levofloxacin, Moxifloxacin, Gentamicin, Dalbavancin, Oritavancin, Telavancin.
Group U
Nitrofurantoin, Sulfisoxazole, Trimethoprim.
Antibiotics to be tested in the Staphylococcus antibiogram according to CLSI and EUCAST |
|||||||||
|---|---|---|---|---|---|---|---|---|---|
| Penicillins | Bacterial species | Disk |
Ø S |
Ø I |
Ø R |
CMI S |
CMI I |
CMI R |
Comments |
| Penicillin according to CLSI |
All staphylococci | 10 U | ≥29 | / | ≤28 | ≤0.12 | / | ≥0.25 | ● Penicillin-resistant staphylococci are resistant to penicillinase-labile penicillins (penicillin G, aminopenicillins, phenoxymethylpenicillin, carboxypenicillins, and ureidopenicillins). |
| Penicillin G according to EUCAST |
S. aureus. | 1 U | ≥26 | / | <26 | ≤0,125 | / | >0.125 | ● The diffusion method in agar medium is more reliable than the determination of the MIC for the detection of penicillinase-producing strain (visualizes the diameter of inhibition and the aspect of the border).
● Penicillin susceptibility should not be reported for non-aureus stapylococci (no reliable method for detecting penicillinase production for species other than S. aureus). |
| Oxacillin (OX, OXA) according to CLSI |
S. aureus et S. lugdunensis
S. epidermidis, S. pseudintermedius et S. schleiferi |
/ 1µg |
/
≥18 |
/ / |
/ ≤17 |
≤ 2 ≤0.25 |
/ / |
≥ 4 ≥0.5 |
● Oxacillin disc is not reliable for testing S. aureus and S. lugdunensis.
● Methicillin (oxacillin) resistant staphylococci are resistant to all currently available beta-lactam antibiotics except ceftaroline. |
| Oxacillin (OX, OXA) according to EUCAST |
S. aureus, S. lugdunensis et S. saprophyticus Other species |
/ / |
/ / |
/ / |
/ / |
≤2 ≤ 0.25 |
/ / |
> 2 > 0.25 |
● Cefoxitin Disc (FOX) is used for the detection of oxacillin-resistant strains.
● Strains of staphylococci resistant to cefoxitin should be interpreted as resistant to all beta-lactams (penicillins associated or not with a beta-lactamase inhibitor, cephalosporins and carbapenems), except ceftaroline and ceftobiprole. |
| Ampicillin (screening), according to EUCAST |
S. saprophyticus | 2 U | ≥18 | / | <18 | / | / | / | ● If the diameter is <18 mm, the strain is resistant to ampicillin, amoxicillin and piperacillin and a cefoxitin test should be performed to determine methicillin susceptibility. |
| Cephalosporins | Bacterial species | Disk |
Ø S |
Ø I |
Ø R |
CMI S |
CMI I |
CMI R |
Comments |
|---|---|---|---|---|---|---|---|---|---|
| Cefoxitin according to CLSI | S. aureus and S. lugdunensis
Other species (except S. pseudintermedius and S. schleiferi) |
30 μg | ≥22 ≥25 |
/ / |
≤21 ≤24 |
≤4 / |
/ / |
≥8 / |
● Neither MICs nor cefoxitin discs are reliable for detecting resistance by the mecA gene in S. pseudintermedius and S. schleiferi.
● Cefoxitin-resistant staphylococci are resistant to all currently available beta-lactam antimicrobial agents except ceftaroline. |
| Cefoxitin according to EUCAST (screening) | S. aureus, and S. non-aureus
other than S. epidermidis. S. epidermidis |
30 μg | ≥22 ≥25 |
/ / |
<22 <25 |
* / |
/ / |
* / |
* S. aureus and S. lugdunensis characterized by MICs of the
cefoxitin >4 mg/L, and S. saprophyticus characterized by MICs of
cefoxitin >8 mg/L are resistant to methicillin mainly from
due to the presence of an additional guy gene. ● Strains of staphylococci resistant to cefoxitin must be interpreted as resistant to all beta-lactams (penicillins associated or not with a beta-lactamase inhibitor, cephalosporins and carbapenems), except ceftaroline and ceftobiprole |
| Ceftaroline according to CLSI | S. aureus, including MRSA | 30µg | ≥25 | SDD 20_24 |
≤19 | ≤ 1 | SDD 2_4 |
≥ 8 | ● The sensitivity threshold is based on a dosage regimen of
600 mg administered every 12 hours. ● SDD: Susceptible Dose Dependent |
| Ceftaroline according to EUCAST | S. aureus S. aureus (pneumonia) |
5 µg 5 µg |
≥20 ≥20 |
ZIT 19-20 |
<17 <20 |
≤1 ≤ 1 |
/ / |
>2 >1 |
● Methicillin-susceptible strains of S. aureus are susceptible to ceftaroline. ● ZIT: Zone of Technical Uncertainty |
| Fluoroquinolones | Bacterial species | Disk |
Ø S |
Ø I |
Ø R |
CMI S |
CMI I |
CMI R |
Comments |
|---|---|---|---|---|---|---|---|---|---|
| CLSI: Staphylococcus spp may develop resistance during prolonged treatment with quinolones. Therefore, initially susceptible isolates can become resistant within 3-4 days after the start of treatment. Repeat isolate testing may be warranted. | |||||||||
| Norfloxacin according to CLSI | All staphylococci | 10 μg | ≥17 | 13-16 | ≤12 | ≤4 | 8 | ≥ 16 | ● For testing and reporting of urinary tract isolates only. |
| Norfloxacin according to EUCAST (screening) | All Staphylococci | 10 μg | ≥17 | ● Strains classified as susceptible to norfloxacin may be rendered sensitive at high doses to ciprofloxacin and to levofloxacin and sensitive to moxifloxacin. For strains no susceptible to norfloxacin, each fluoroquinolone should be tested individually and rendered as categorized | |||||
| Ciprofloxacin according to CLSI | All staphylococci | 5 μg | ≥21 | 16-20 | ≤15 | ≤1 | 2 | ≥4 | |
| Ciprofloxacin according to EUCAST | S. aureus S. non-aureus |
5 μg 5 μg |
≥50 ≥50 |
/ / |
<21 <24 |
≤0.001 ≤0.001 |
/ / |
>1 >1 |
|
| Levofloxacin according to CLSI | All staphylococci | 5 μg | ≥19 | 16_18 | ≤15 | ≤1 | 2 | ≥4 | |
| Levofloxacin according to EUCAST | S. aureus S. non-aureus |
5 μg 5 μg |
≥50 ≥50 |
/ / |
<22 <24 |
≤0.001 ≤0.001 |
/ / |
>1 >1 |
● A
strain resistant to levofloxacin must be resistant to all fluoroquinolones. |
| Moxifloxacin according to CLSI | All staphylococci | 5 μg | ≥24 | 21-23 | ≤20 | ≤0.5 | 1 | ≥2 | |
| Moxifloxacin according to EUCAST | S. aureus S. non-aureus |
5 μg 5 μg |
≥25 ≥28 |
/ / |
<25 <28 |
≤0.25 ≤0.25 |
/ / |
>0.25 >0.25 |
● A
strain resistant to moxifloxacin must be resistant to all fluoroquinolones. |
| Ofloxacin according to CLSI | All staphylococci | 5 μg | ≥18 | 15-17 | ≤14 | ≤1 | 2 | ≥4 | |
| Delafloxacin according to EUCAST | S. aureus | / | / | / | / | ≤0.25 | / | >0.25 | |
| Enoxacin according to CLSI | All staphylococci | 10 μg | ≥18 | 15-17 | ≤14 | ≤2 | 4 | ≥8 | ● For testing and reporting of urinary tract isolates only. |
Reference