Serratia infection laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Diagnosis of Serratia infection is made by growth of Serratia in culture media. Other laboratory findings are non-specific.

Laboratory findings may be non-specific and depend on the site of infection.

According to the Centers for Disease Control and Prevention (CDC), the following procedure should be followed to properly culture Serratia:^[1]

• Biosafety Level: 2
• Medium: Trypticase Soy Agar with 5% Sheep Blood (BAP)
• Growth Conditions:

• Temperature: 35 °C (95 °F)
• Atmosphere: Aerobic

• Procedure

• Remove the sample vial to a container with dry ice or a freezer block. Keep vial on ice or block. (Do not let vial content thaw)
• Open vial aseptically to avoid contamination
• Using a sterile loop, remove a small amount of frozen isolate from the top of the vial
• Aseptically transfer the loop to BAP
• Use streak plate method to isolate single colonies
• Incubate inverted phase at 35 °C (95 °F) for 18-24 hours

The following table demonstrates the minimum inhibitory concentration (MIC) results following Serratia culture/antibiogram and interpretation:

^{* Reflects MIC of first component
** Screen for metallo-beta-lactamase production[2]
*** Based on FDA break points
Abbreviations: MIC=Minimum inhibitory concentration; I=Intermediate; R=Resistant; S=Susceptible
Table adapted from Antimicrobial Resistance Bank – Serratia marcescens. Centers for Disease Control and Prevention.[3]}