The Microbial Disease Laboratory (MDL) Branch is part of the Center for Laboratory Sciences (CLS)​, California Department of Public Health ​(CDPH). MDL supports State and local public health programs for the prevention and control of communicable diseases. The laboratory plays a key role in the epidemiologic investigations of disease out​breaks, and in providing reference diagnostic services to the local public health laboratories at county or city level. Additionally, the laboratory is a designated facility for the testing of the Select Agents, and training of future public health microbiologists.

MDL has in-house personnel skilled in both traditional methods such as microbial cultures, biochemical profiles and serological typing as well as in nucleotide sequencing, real-time quantitative polymerase chain reaction, chromosomal typing, multiplex-beads assay system, and MALDI-TOF. Specimens are usually accepted from other public health laboratories and by prior authorization from other sources. The test turnaround times vary with different assays and the result is reported directly to the submitter. The business hours are from 8:00 A.M. to 5:00 P.M. Monday through Friday. The laboratory observes all State holidays.​​