OxyPRAS Plus® PEA Blood Agar Plate
OxyPRAS Plus® PEA Blood Agar is a pre-reduced anaerobically sterilized (PRAS) phenylethyl alcohol blood agar plate for the selective isolation of anaerobic bacteria, especially gram-positive anaerobes, from clinical specimens. Phenylethyl alcohol suppresses most gram-negative facultative organisms such as the Enterobacteriaceae and stops Proteus from swarming, so anaerobes in a mixed specimen are not overgrown. The medium is enriched with 5% sheep blood and vitamin K1 and arrives ready to inoculate with no post-reduction step.
At a glance
Catalog number: P-PEA-BA (single plate), P-PEA-10 (10-pack). Also in multi-packs M-BKP-3, M-BKBP-3.
Medium: Phenylethyl alcohol agar with 5% defibrinated sheep blood and vitamin K1 1 mg/L. Initial pH 7.45.
Type: Selective, enriched. Inhibits gram-negative facultatives; supports gram-positive and obligate anaerobes.
Shelf life: 4 months from manufacture. 28-day minimum guaranteed on arrival.
Storage: 2 to 8°C. Ships at room temperature.
Packaging: Individually sealed oxygen-impermeable pouch.
User QC: Listed as exempt under CLSI M22-A3. Lot QC performed by Oxyrase.
Regulatory: For in vitro diagnostic use. Manufactured in Mansfield, Ohio under ISO 9001:2015.
When to use it
PEA blood agar earns its place in the anaerobic media set on polymicrobial specimens: intra-abdominal and pelvic abscesses, decubitus and diabetic foot wounds, aspirates from sites with a heavy gram-negative facultative load. On a non-selective plate those specimens can come back as a lawn of E. coli or a swarm of Proteus with the anaerobes buried underneath. PEA holds the facultatives back and lets clostridia, peptostreptococci, and other gram-positive anaerobes come up as discrete colonies.
Run it next to OxyPRAS Plus® Brucella for the full picture, and add OxyPRAS Plus® KVL if you also need the gram-negative anaerobes selected out. The OxyPRAS Plus® 3-pack bundles Brucella, PEA, and a BBE/KVL bi-plate for this workflow.
Why PRAS manufacturing matters
Anaerobic media that is poured and packaged in air accumulates oxidation products before it ever reaches your bench. Those products inhibit the most oxygen-sensitive anaerobes, and the effect is invisible: the plate looks fine and simply reports no growth.
OxyPRAS Plus® plates are reduced with the Oxyrase® Enzyme System before sterilization and held in a reduced state through storage and use. In our PRAS vs. non-PRAS comparison, 8 of 30 non-PRAS Brucella plates inoculated with Porphyromonas levii grew nothing at all, while 0 of 30 OxyPRAS Plus® plates failed. OxyPRAS Plus® plates also tolerate up to 2 hours of ambient oxygen exposure during setup without inhibitory oxidation, which gives the bench flexibility to batch work and to use automated streaking platforms.
Read the full data in The Plate That Reports Nothing and the oxygen exposure white paper.
Formulation
Approximate composition per liter of deionized water. Initial pH 7.45 ± 0.15. Production lots may be adjusted to offset raw material variance in order to meet performance criteria.
| Component |
Amount |
| Enzymatic digest of casein |
15.0 g |
| Enzymatic digest of soybean meal |
5.0 g |
| Sodium chloride |
5.0 g |
| Phenylethanol |
2.5 g |
| Agar |
15.0 g |
| Vitamin K1 |
1.0 mg |
| Defibrinated sheep blood |
51.0 mL |
| Oxyrase® Enzyme System |
proprietary |
Phenylethyl alcohol reduces growth of facultative gram-negative bacteria without affecting gram-positive organisms and prevents Proteus swarming while leaving obligate anaerobes unaffected. Vitamin K1 improves growth of some Bacteroides species. Sheep blood adds nutrients and allows hemolytic reactions to be read.
Quality control
Samples of every lot are tested to Oxyrase specifications incorporating CLSI M22-A3. The following results are confirmed before release:
| Organism |
ATCC |
Expected result |
| Bacteroides fragilis |
25285 |
Growth in 2 to 3 days |
| Staphylococcus aureus |
25923 |
Growth in 2 to 3 days |
| Proteus mirabilis |
12453 |
Swarming inhibited for three days |
| Streptococcus pyogenes |
19615 |
Growth in 2 to 3 days |
Uninoculated medium is red with no surface imperfections. PEA blood agar is listed as exempt from user quality control under CLSI M22-A3; each laboratory should still establish its own QC program in line with its accreditation requirements, and the organisms above are recommended if you choose to test.
Directions for use
- Allow plates to reach room temperature before use.
- Remove the plate from the pouch.
- Check for contamination, oxidation (a bright red rather than dark red surface), and the expiration date.
- Inoculate and streak using standard technique.
- Invert and incubate at 35 to 37°C in an anaerobic bag, jar, or chamber.
- Include an anaerobic indicator such as OxyBlue™ to confirm anaerobiosis.
- Read plates after 2 to 3 days.
Anaerobic incubation is still required. PRAS manufacturing protects the medium before and during setup; it does not replace the anaerobic atmosphere during incubation.
Storage, shelf life and guarantee
Plates ship at room temperature and should be stored at 2 to 8°C on receipt. Expiration is 4 months from date of manufacture; the actual date is printed on each plate. Oxyrase guarantees at least 28 days of shelf life from the ship date, and longer dating can be arranged when you order. If OxyPRAS Plus® PEA Blood Agar plates arrive short-dated, contaminated, or oxidized, or fail when used as directed, we refund the purchase price. Contact us with the lot number printed on the plate.
Limitations
- Slower-growing anaerobes may need longer incubation before growth or pigmentation is visible on this medium.
- As a selective medium it supports only select organisms. Colony types require additional identification.
- Hemolysis on PEA can be irregular and should be interpreted with other findings.
- The Oxyrase® Enzyme System contains a penicillin-binding protein that may interfere with penicillin and some related antibiotics. Do not use these plates for susceptibility testing.
- Contains material of animal origin. Source animals are documented free of BSE/TSE.
Frequently asked questions
What does PEA agar inhibit?
Most gram-negative facultative anaerobes, including the Enterobacteriaceae, and it prevents Proteus swarming. Gram-positive organisms and obligate anaerobes grow normally.
Why is a PEA plate PRAS if it is selective anyway?
Selectivity controls what grows. PRAS manufacturing controls whether oxygen-sensitive anaerobes survive long enough to grow at all. A selective plate that has oxidized still reports nothing for the most fastidious anaerobes.
Do I need to reduce the plates before inoculating?
No. OxyPRAS Plus® plates are reduced during manufacturing and stay reduced in the sealed pouch. Open, inoculate, and incubate.
How long can the plate sit on the bench after opening?
Up to 2 hours of ambient oxygen exposure without inhibitory oxidation. Inoculate as soon as practical.
Does my lab have to run QC on each lot?
PEA blood agar is on the CLSI M22-A3 list of media exempt from user QC. Each lot is tested by Oxyrase before release. Your accreditation program may still ask you to document receipt and inspection.
Is it available through my distributor?
Yes, through Fisher Scientific and Cardinal Health, or direct from Oxyrase. Ask us about volume pricing for standing orders.
