Hello everybody! This is Jeremy Chu (TG01) attached to bacteriology posting on...
The Miscellaneous Bench
The miscellaneous bench deals with every other specimens besides blood, stool, urine and respiratory specimens. Fluid, tissues and swabs are mainly the samples received. Some examples are heart/liver tissues, peritoneal fluid or peritoneum fluid, wound swabs and high/low vaginal swabs. Detecting bacteria at these sites are important, especially for sterile sites. There should not be any bacteria found at sterile sites such as the heart and liver or patient’s situation could be fatal.
Wound cultures are performed to isolate and identify bacteria infections causing an infection of the wound. This way, doctors can then administer the appropriate antibiotics to kill the causative agent.
Fluid culture is done, similarly to isolate and identify bacteria causing an infection. Peritoneal/Pericardial fluids are sterile fluids and any presence of bacteria is regarded as significant. Gram stain is also performed.
High vaginal swabs are cultured for the purpose of detecting group B streptococci (commonly Streptococcus agalactiae) found in the female reproductive tract. S. agalactiae can cause pneumonia and meningitis commonly in neonates and the elderly.
The different types or media used and its purposes are listed in the table below.
Media | Purpose | Types of specimens |
Blood Agar | Enriched media to enhance bacteria growth | Tissues Fluids Fluid swabs Wound swabs Catheter tips/devices Vaginal swabs |
MacConkey Agar | Selective media to inhibit most gram positive bacteria and differentiates lactose fermenters | |
Blood Agar (anaerobic) | Enriched media to enhance anaerobic bacteria growth | Tissues Fluids Fluid swabs |
Cooked Meat broth | Enriched broth for cultivating bacteria | Tissues Fluids Fluid swabs Wound swabs Catheter tips/devices |
LIM broth | Enriched broth used to grow group B streptococci from vaginal swabs | Vaginal swabs |
Fluid culture agar plates are incubated under CO2 conditions, while its broths in aerobic conditions. Blood, MAC, blood (anaerobic) agars and cooked meat broth are the choice of media.