Welcome to the State of California 

The MDL Today

Currently, MDL is part of the California Department of Public Health (CDPH), Center for Infectious Diseases (CID), Division of Communicable Disease Control (DCDC). Located since 2003 on the Richmond Campus of the CDPH, the laboratory has four sections: Biologics; Mycobacteriology and Mycology; Enteric Diseases & Special Pathogens; and, Environmental Microbial Diseases. In addition to reference testing, MDL conducts applied research and provides instruction to Public Health Microbiologists and Postdoctoral Fellows. The laboratory has 60 staff members which include Laboratory Directors, Public Health Microbiologists, Research Scientists, Technicians and Fellows.

Biologics Section

The Biologicals Section provides services developing high-quality immunological diagnostic reagents not otherwise obtainable through commercial sources for use in MDL diagnostic and reference testing. The Biologics Section assists the CDC and other state health departments and agencies in obtaining such reagents; and works with numerous agencies, universities and research establishments to contribute to the availability of reagents and assay methods useful to public health laboratories, CDC, and other state and federal agencies.


      Using plate agglutination method and MDL-prepared
      monoclonal antibodies (left) to detect Salmonella
      typhi seropositive human sample (right, arrowed)

     Diagnostic antibodies produced by Biologics include:

  • Polyclonal antibodies against the whole cells of E.coli O157, Vibrio cholerae, and multiple serogroups of Salmonella, Shigella, and Legionella;
  • Monoclonal antibodies against the O and H antigens of multiple Salmonella serogroups;
  • Polyclonal conjugates against Legionella, Actinomyces, Rothia dentocariosa, Borrelia burgdorferi, Clostridium botulinum, Corynebacterium matruchotii, Haemophilus ducreyi, Neisseria meningitidis, Streptobacillus, Vi antigen;
  • Modified commercial detection antibody preparations to improve detection specificity;
  • Various whole-cell bacterial antigens used for serology assays.




Specificity of an MDL-prepared Salmonella O: 8 monoclonal antibody (MAB) was demonstrated by a competitive inhibition assay in which the MAB at a standard concentration was mixed with serial dilutions of Salmonella O antigens as inhibitors.  The inhibition of the MAB subsequently binding to an O: 6, 8 antigen was measured. Only the O: 8 and O: 6, 8 antigens give a dose-dependent inhibition as shown.  



Mycobacteriology and Mycology Section

The Mycobacteriology and Mycology Section (MMS) provides services for detection and genotyping of mycobacteria in various samples; and for identification of genetic mutations of multidrug-resistant Mycobacterium tuberculosis through DNA pyrosequencing, providing preliminary results to guide therapy during the period of several weeks when tuberculosis cultures are growing and culture-based drug susceptibility testing is being performed. MMS also provides identification testing on dimorphic fungus (Coccidioides spp.).





          Mutations found in the genes of drug-resistant M.
tuberculosis isolates by pyrosequencing at MDL


Enteric Diseases & Special Pathogens Section

   Special Pathogens Unit:

   Enteric Diseases Unit:

      (Microscopic) Y. pestis after
      being stained with fluorescent
      dye-labeled detection antibody

The Special Pathogens unit provides public health laboratory testing for the identification and serotyping of most bacterial pathogens from human sources except Mycobacterium and enteric bacteria. The unit provides serogrouping and serotyping of vaccine-preventable bacterial pathogens including H. influenzae, N. meningitidis, and S. pneumoniae. Rapid nucleic acid amplification testing of primary specimens is available for culture negative cases of suspected invasive meningococcal and pneumococcal disease. The unit provides laboratory testing to support plague surveillance activities in California and provides reference level diagnostic testing for the detection of bacterial select agents (such as Y. pestis) and toxins through participation in the Laboratory Response Network (LRN).


       Shiga toxin negative (left) and positive
       (right) bacteria on Vero cells

The Enteric Diseases unit provides public health laboratory testing for the identification, serotyping, and strain typing of bacterial isolates belonging to the families Enterobacteriaceae, Vibrionaceae, and Aeromonadaceae. Specialized testing includes screening and confirmation for Shiga Toxin-producing E. coli, toxigenic V. cholerae detection, and nucleic acid amplification testing for the detection of carbapenem resistance genes. The unit provides molecular strain typing for the detection of foodborne disease outbreaks and is a member of PulseNet. Diagnostic testing for blood and intestinal parasites is also available through the Enteric Diseases unit.

Environmental Microbial Diseases Section


EMDS services include:

Paralytic toxin surveillance that enables regulators to determine when shellfish can be safely harvested from recreational and commercial growing areas. This joint collaboration between regulator and lab has existed since the 1980’s. When toxin levels exceed specific parameters in a particular location, the regulators protect the public from consuming the toxic shellfish. 

Food, water, and environmental outbreak and surveillance support to stakeholders (e.g., public health labs, epidemiologists and local, state, and federal regulators plus LRN partners). Support consists of guidance, testing, and reporting functions. Typical bacterial exams include those associated with contaminated products or environments. Examples include exams for toxigenic E. coli, Salmonella species, Clostridium perfringens, Staphylococcus aureus, Listeria species, Clostridium botulinum or indicator organisms.

Classical and molecular methods to detect, isolate and identify botulinum neurotoxin producing species of Clostridium in human and environmental samples submitted through local public health laboratories. This service is not diagnostic; it assists public health in the identification of human cases for the purpose of reporting disease incidence to the Centers for Disease Control and in the tracking of contaminated products that may have been distributed to the public.





Paralytic Shellfish Poisoning (PSP)
toxin surveillance on a California
estuary during Jan. - Feb., 2013






Clostridium botulinum (left) detected
in home canned food sample (right)

Last modified on: 10/25/2013 1:56 PM