DW-16 Automatic Bacterial Spread Plating Instrument by DAWEI

Overview

The DW-16 Automatic Bacterial Spread Plating Instrument is an engineered solution for standardized, reproducible microbial inoculation in classical culture-based microbiology workflows. Designed specifically to replace manual spread plating—a technique widely used in colony-forming unit (CFU) enumeration, antibiotic susceptibility testing (AST), and strain isolation—the DW-16 implements a controlled rotational spreading principle grounded in centrifugal fluid dynamics. When a defined volume of bacterial suspension is deposited at the center of a standard 90 mm Petri dish placed on the motor-driven platform, rotation induces radial dispersion under controlled angular velocity. This process ensures uniform distribution of cells across the agar surface without mechanical shear-induced cell lysis or localized over-concentration—critical prerequisites for accurate CFU quantification per ISO 4833-1:2013 and FDA BAM Chapter 3. The instrument operates independently of robotic integration but conforms to GLP-aligned laboratory practices through consistent mechanical actuation, eliminating inter-operator variability inherent in hand-held spreader techniques.

Key Features

• Motor-driven rotary platform with four discrete speed settings (200, 250, 300, and 350 rpm), enabling optimization for viscosity-dependent media (e.g., 1.5% agar vs. soft agar overlays)
• Spill-resistant mechanical architecture featuring sealed bearing housings and sloped internal chassis geometry to prevent ingress of liquid media or condensate into drive components
• Corrosion-resistant metal alloy construction (anodized aluminum and stainless steel fasteners), fully compatible with routine decontamination using 70% ethanol, isopropanol, or sodium hypochlorite solutions
• Dish alignment ring included to ensure precise centration of standard 90 mm plastic or glass Petri dishes (per ISO 648:2022 dimensional tolerances: base outer diameter 87 ± 0.5 mm; lid outer diameter 89–90 mm)
• Low-power DC motor with thermal cut-off protection, supporting extended unattended operation during high-throughput plating sessions
• Manual start/stop interface via tactile push-button—no software dependency, minimizing validation burden in regulated environments

Sample Compatibility & Compliance

The DW-16 is validated for use with standard 90 mm Petri dishes containing solidified agar-based media (e.g., Tryptic Soy Agar, Plate Count Agar, MacConkey Agar, Mueller-Hinton Agar). It supports both single-layer and double-layer plating protocols and accommodates common spreader types—including calibrated stainless steel “L-shaped” spreaders and sterile disposable plastic spreaders—without requiring proprietary consumables. While not classified as a medical device, its design adheres to fundamental principles outlined in ISO 13485:2016 (for manufacturer quality systems) and supports compliance with USP <61>, EP 2.6.12, and ISO 11133:2014 requirements for culture media performance verification. No firmware or network connectivity is present, eliminating cybersecurity concerns and simplifying 21 CFR Part 11 compliance for audit trails when paired with paper-based or LIMS-linked procedural documentation.

Software & Data Management

The DW-16 operates as a standalone electromechanical device with no embedded microprocessor, firmware, or digital interface. All operational parameters—including speed selection and activation—are managed manually via physical controls. Consequently, no software validation, update management, or electronic record retention is required. This architecture aligns with laboratories implementing paper-based Standard Operating Procedures (SOPs) or those seeking minimal-complexity instrumentation for ISO/IEC 17025-accredited microbiology testing. For labs utilizing Laboratory Information Management Systems (LIMS), instrument usage can be logged manually or integrated via external barcode scanning of plate identifiers prior to plating—ensuring full traceability without reliance on instrument-generated metadata.

Applications

• Quantitative microbial enumeration (CFU/mL or CFU/g) in food, water, pharmaceutical, and environmental samples per ISO 4833-1, APHA 9221, or ASTM D5542
• Preparation of uniformly seeded plates for disk diffusion antimicrobial susceptibility testing (AST) in accordance with CLSI M02-A13 and EUCAST guidelines
• Isolation of pure colonies from mixed cultures or enrichment broths during strain purification workflows
• High-reproducibility plating for phage titration (plaque assays) and mutant screening protocols
• Training platforms for undergraduate and technical staff to standardize spread plating technique prior to manual execution

FAQ

Does the DW-16 support Petri dishes other than 90 mm?
No. The mechanical alignment system and rotational torque profile are calibrated exclusively for standard 90 mm dishes (base OD 87 mm). Use of non-standard diameters may result in off-center rotation, uneven spreading, or mechanical interference.
Can the instrument be used inside a biosafety cabinet?
Yes. Its compact footprint (200 × 180 × 120 mm), low electromagnetic emission profile, and absence of heat-generating components make it suitable for Class II A2 and B2 biosafety cabinets.
Is calibration required before use?
No periodic calibration is mandated. However, users should verify rotational speed accuracy annually using a handheld tachometer against the labeled settings (200/250/300/350 rpm) as part of preventive maintenance.
What sterilization methods are validated for the unit?
Surface disinfection with 70% ethanol or isopropanol is fully supported. UV-C irradiation (254 nm, ≥15 min exposure at 1 m distance) is also effective. Autoclaving, steam, or immersion cleaning is strictly prohibited.
Are replacement parts available?
Yes. DAWEI supplies certified replacement alignment rings, motor brushes, and power supply units under part numbers DW-16-RING, DW-16-BRUSH-KIT, and DW-16-PSU-12V, respectively.