LAR Standard Operating Procedures

Working With Staphylococcus aureus in an Animal Model

Last updated: March 21, 2012

Background Information

All work will be conducted at BSL2 in a Type II Biosafety Cabinet (BSC).  Outbred female mice aged 4-12 weeks old will be used for these studies.  On the day of inoculation, cultures of S. aureus will be prepared in a BSC in the laboratory of the PI and placed into individual doses in syringes, packaged per Institutional Biosafety Committee (IBC) requirements for transport to the animal facility where the inoculae is placed into the BSC. 

Mice will be inoculated by IP injection (23-27 gauge needle) of 0.3 mL of bacterial inoculae.  All syringes will be repackaged for transport back to the PI's laboratory and disposed of appropriately there.

Thoroughly wash hands with soap and water before leaving the laboratory and after handling infectious materials.

Signage

Appropriate biohazard signage will be posted in the laboratory and in the animal facility to prevent unauthorized entry to the restricted area during bacteria preparation, inoculation and harvesting.  Cages with inoculated mice will be appropriately labeled as containing S. aureus.

PPE

All personnel working with S. aureus or infected animals must wear:

1. Disposable surgical mask
2. Disposable gloves
3. Lab coat with elasticized fitting at the wrists 

All work with S. aureus and S. aureus infected animals and their caging, bedding, etc. will be conducted in a BSC. 

Non disposable materials coming into contact with infected animal (weigh trays, etc.) will be kept in the BSC under UV irradiation between manipulations.

Disease Condition in the Animals

The infected mice are expected to develop a systemic bloodborne infection (sepsis).  Mice are expected to experience lethargy, ruffled hair coat, inappetance, dehydration, weight loss, and muscle soreness as exhibited by discomfort and sensitivity to touch. Some mice may die suddenly without first showing signs of illness.  S. aureus is an opportunistic secondary parasite of wound sites (these are rare in young female mice), so any mice with wounds will be monitored extremely closely.

Transmission of infection can occur through contact with infected animals or their secretions.  All bedding and cage material and equipment should be considered to carry infectious organisms.  Potentially, viable bacteria may be excreted in urine if sufficient kidney damage occurs.  The rate of excretion is unknown and varies depending on degree of illness of individual animals

S. aureus is susceptible to common disinfectants used in animal facilities and to mechanical or chemical sterilization.  All bedding, unused food and water, disposable gloves, paper towels used for wiping surfaces will be steam sterilized in red biohazard bags. All racks for housing animals will be disinfected using MB-10 (chlorinated disinfectant) and then washed in the cage washer.

Waste Disposal

All dirty bedding and carcasses will be handled as biohazards and autoclaved before routine cleaning or disposal, respectively.   All bedding, unused food and water, disposable gloves, paper towels used for wiping surfaces will be steam sterilized in red biohazard bags. All racks for housing animals will be disinfected using MB-10 (chlorinated disinfectant) and then washed in the cage washer.

Clean Up

All spills of live cultures should be treated with 10% bleach or MB-10 (chlorinated disinfectant) prior to cleaning up with paper towels. Paper towels should then be collected into biohazard bags and sealed for further steam sterilization.