DIRECTOR: Mary Jane Ferraro, Ph.D., M.P.H. x6-3612
ASSOCIATE DIRECTOR: Eric Rosenberg, M.D. x4-7519
ASSISTANT DIRECTOR: John Branda, M.D. x6-3611

The Microbiology Laboratories are divided into Bacteriology, Susceptibility Testing, Mycology, Mycobacteriology, Parasitology, Virology, Serology, and Molecular Diagnostics. Specimens are accepted for accessioning and processing for all divisions 24 hours/day.

Hours of Full Service Operation

General Microbiology
24 hours for accessioning and processing of specimens.

Anaerobes, Molecular Diagnostics, Mycology, Mycobacteriology,
Parasitology, Serology, and Virology
Mon-Fri 8:30am-5:00pm

For information or special test requests call x6-3613 during the above hours. For after-hour emergency assistance call the Clinical Pathology Resident for Microbiology (beeper #2-1826).

Specimen Collection

Specimens submitted to the Microbiology Laboratories must be labeled with patient’s name and unit number and bagged according to Infection Control Standard Precaution protocols. The requisition should be firmly attached to the outside of the specimen transport bag and be filled in with the following information:

1. Patient Name
2. Patient Unit Number
3. Patient Location (i.e., in-house, clinic or physician to whom report is to be sent if private patient).
4. Telephone extension of ordering care unit or physician.
5. Type or source (anatomic site) of specimen.
6. Type of culture requested (i.e. routine, fungal, TB, viral, etc.)
7. Ordering Physician
8. Diagnosis and/or specific organism sought.
9. Date and time of collection.
10. Specific organism sought.

Specimen Delivery

Because they may contain viable micro-organisms, specimens should be delivered to the laboratory as soon as possible after collection. Specimens are accepted for all divisions 24 hours.

Special Requirements

Ambulatory patients requiring specimens for parasite examination should be directed to the Ambulatory Lab #2 in the Wang Ambulatory Care Center (WACC), 2nd Level for specimen collection instructions and assistance. Fresh stool specimens for O&P arriving in laboratory after 4 p.m. will be preserved for processing the next working day.

Respiratory specimens from cystic fibrosis patients (including post-transplant patients) must be labeled "CF" to receive appropriate specimen processing and workup.

Criteria for Refusal of Specimens

For the purpose of providing useful diagnostic testing, the Microbiology laboratories consider it an obligation to refuse specimens under the following circumstances:

1. Patient's name and unit number are not provided.
2. Name on specimen differs from that on the requisition.
3. Specimen type is not that indicated on the requisition.
4. Specimen is one or more days old.
5. Specimen type is not indicated.
6. Test requested is not available in the Microbiology Lab.
7. Quantity is not sufficient.
8. Quality of specimen is questionable.
9. Improperly sealed or leaking container.
10. Specimen is received in fixative or in improper fixative
11. Time or date of collection is not indicated.
12. Excessive delay in receiving specimen for anaerobic culture.
13. Method of collection is not acceptable for anaerobic culture and viral culture.
14. Stool specimens from patients hospitalized >3 days.
15. Whole blood specimens for molecular diagnostics testing received >6 hours after collection.

Specimens that have been refused are held in the laboratory for 48 hours and will be processed only after consultation with the laboratory supervisory personnel by the requesting physician. Specimens which are unacceptable for any of the above reasons, which have been collected by invasive procedures, or which might necessitate recalling an outpatient for recollection will usually be processed with a notation on the report indicating why the specimen is unacceptable. Interpret results of such cultures carefully.

Results
Preliminary and final times listed for individual cultures indicate the earliest times for availability of results. Positive cultures may require additional time for identification or susceptibility testing of isolates. The lab will call results to the requesting area in accordance with the MGH Critical Values Policy

NOTES ON MICROBIOLOGY LABORATORY RESULTS (September 2004)

1. PRELIMINARY RESULTS – All culture results are preliminary unless marked “FINAL.” Preliminary results may be changed, modified, deleted, or augmented after further observation, incubation, or testing of cultures.

2. ROUTINE CULTURES AND “NORMAL FLORA”:

3. ANTIMICROBIAL SUSCEPTIBILITY TESTING

Susceptibility testing of aerobic pathogens is performed by either the Kirby-Bauer disk diffusion method or an automated, rapid system (Vitek AMS), depending upon identification of the organism and reliability of the applicable methods. Anaerobic susceptibility testing is available after consultation with the laboratory. Results of susceptibility testing are interpreted into 3 categories (Susceptible, Intermediate, Resistant), using standardized criteria. The intermediate category for a drug indicates an equivocal result and this drug should generally not be relied on for single agent therapy except perhaps of urinary tract infections. Certain organisms are screened for beta-lactamase production before susceptibility results are reported.

Susceptibility testing is done using the class drug concept for certain antimicrobials. Oxacillin susceptibility applies also to methicillin, nafcillin, cloxacillin, dicloxacillin, cephalothin, cefaxolin and other cephalosporins. Cefaxolin or cephalothin susceptibility applies also to cephapirin, cephradine, cephalexin, cefadroxil, and cefaclor.

Serious infections with enterococci respond best to a combination of penicillin, ampicillin, or vancomycin plus gentamicin; less serious infections and urinary infections generally respond to ampicillin alone. Certain strains of enterococci possess high level resistance to gentamicin and resist killing by the above combinations with gentamicin; advice on treating serious infections with these organisms can be obtained from the Infectious Disease Unit. Blood and cerebrospinal fluid isolates of enterococci are routinely screened for high level resistance to gentamicin and for penicillinase production (which mediates one type of resistance to penicillin and ampicillin); these resistances, if present, are indicated on the report.