Director: Michael Mitchell, MD

(508) 856-6417

Lab Manager: Brenda Brogden-Torres, BS, MT SM(ASCP)

(508) 856-3429

The Microbiology Laboratories offer a broad range of services for the diagnosis of infectious diseases. Laboratory sections include bacteriology (aerobic and anaerobic), mycobacteriology, mycology, parasitology, virology, and serology.

Please refer to the Laboratory Manual for a listing of available tests. The Manual includes specimen requirements, transport conditions, turn-around-time, reference range, and other information. The Laboratory Manual also lists Critical Values that are called to the requesting provider as soon as available. Gram stains may be requested STAT in emergency situations, and these results are handled like Critical Values. All final test results can be viewed in the computer system and a copy of these results are sent to the requesting clinician.

Standard protocols are applied by the Laboratoies for the detection of microorganisms. If an uncommon or fastidious pathogen is suspected, please alert the Laboratory. Some of these pathogens (like Legionella or Brucella) require special procedures for detection.

The technologists in the Laboratory are available to assist clinicians who wish to review test results or slides. In addition, the Laboratory Director is available by beeper to provide consultation concerning diagnostic or interpretative problems.

In many significant infections, the responsible pathogen may detected directly by microscopic examination of stained smears. Bacterial and fungal pathogens are most frequently detected by a Gram stain, which is routinely performed on sputum, biopsy, wound, and sterile fluids. Gram stains may be ordered on other specimen types, when appropriate. Since the sensitivity of stained smears is less than the sensitivity of culture, a culture should always be requested with requests for stained smears. (Exceptions include accurate diagnosis of oral or vaginal thrush by Gram stain only.)

Specimens for mycobacterial detection are stained using a fluorochrome stain specific for acid fast bacteria. Positive results are phoned STAT to the requesting clinician.

Wet mounts (KOH) for fungi, nocardia stains, cryptococcal antigen detection, and monoclonal antibody stains for Pneumocystis carinii, RSV, HSV and VZV are also available, as described in the Laboratory Manual.

Culture protocols for each specimen type are designed to detect the pathogens commonly isolated from that site. If an unusual pathogen is suspected, alert the laboratory so that appropriate methods can be used. Significant aerobic isolates will be tested for susceptibility to a variety of antibiotics, appropriate for the organism and specimen type. The organism is reported as Sensitive, Intermediate, or Resistant, based of achievable concentrations of the antibiotic in serum. Quantitative MIC results or special susceptibility testing may be requested.

Most significant infections show moderate or heavy growth of a single pathogen. Full work-up of cultures yielding more than two potential pathogens is rarely clinically useful and will be performed only by specific request. Therefore, isolates from mixed cultures will be repoted only descriptively.

Specimens for anaerobic culture must be transported quickly under anaerobic conditions. Specimens transported under these conditions are also acceptible for aerobic, fungal, and mycobacterial culture, if sufficient quantity is submitted.

The Mycology Laboratory performs tests to detect and identify fungal (yeast and mold) pathogens. Direct detection, using calcofluor white stained KOH wet mounts or cryptococcal antigen testing, may be requested. Fungal cultures are incubated for four weeks. Most yeasts, however, are isolated and identified within 3 to 5 days. Molds, especially dermatophytes and dimorphic pathogens, require longer times for isolation and identification.

Notify the Laboratory if a dimorphic pathogen (like Coccidioides or Histoplasma) is suspected because these isolates are common causes of laboratory acquired infection.