Laboratory Bulletin...
Updates and Information from Rex Healthcare and Rex Outreach
April 1996
Diagnosing
pneumonia,
proposed
changes for
sputum cultures
Issue Number 7
Several key parameters have been identified in an effort to maximize the diagnostic yield from
sputum cultures. Procurement of adequate sputum samples is an essential first step. To maximize
the diagnostic yield of the sputum examination, only samples free of oropharyngeal contamination
should be processed. Based on the current literature, samples with more epithelial cells and fewer
neutrophils are non-diagnostic and should be rejected. The presence of alveolar macrophages does
not alter the bacteriologic findings when substantial numbers of epithelial cells are present,
indicating that otherwise adequate samples of sputum can be contaminated with oropharyngeal
contents and thereby rendered non-diagnostic. 1
Although generally not considered diagnostic, the initial Gram stain can be clinically useful. A
predominance of gram positive, lancet-shaped diplococci should suggest pneumococcal infection.
Small, gram-negative coccobacillary organisms are characteristic of H. influenzae.
In a retrospective six month study of sputum cultures at Rex Hospital, based on the criteria that, for
a sputum to be acceptable, the ratio of WBCs to epithelial cells must be greater than one, 214 of 970
specimens would have been considered unacceptable (22%).
It is proposed that within the next few months, Rex Laboratory would begin rejecting unacceptable
sputum culture specimens for inpatients and ask that they be re-collected. The initial specimen
would be held refrigerated for up to 24 hours until a satisfactory specimen is resubmitted. Rejected
specimens would only be processed by specific physician request when clinically justified. If a
specimen is rejected and not cultured, the sputum culture billing would be replaced with a Gram
stain only charge.
New criteria would also be applied to “working up” sputum cultures. Cultures with a clear
predominance of a single potential pathogen (see below) relative to the oropharyngeal flora present
would get complete ID and susceptibilities as appropriate.
If a second pathogen is present in lesser amounts, only a presumptive ID would be given for the
second pathogen. For cultures with three or more potential pathogens, none predominating, Mixed
flora would be reported. In both cases the comment, For further workup, contact the laboratory
within 24 hrs - tel 783-3051, would be included. If further identification and/or susceptibilities are
required for patient management, the laboratory would need to be notified.
Potential pathogens include:
Streptococcus pneumonia
Haemophilus influenzae
Beta hemolytic streptococci
Enterobacteriacae
Pseudomonas, Acinetobacter, Xanthamonas
Moraxella catarrhalis
Staphylococcus aureus
Enterococcus
Yeast.
Cultures having only organisms that are considered normal flora would be reported as Normal
respiratory flora.
1
Principles and Practice of Infectious Diseases Mandell, Douglas and Bennett, 4th edition, 1995.
If there are any questions or comments concerning these proposed procedures, please contact
Dr. Kleeman at 783-3063 or Dr. John Sorge at 783-3062.
Karl T. Kleeman, Ph.D.
John P. Sorge, M.D.
Piperacillin no
longer routinely
reported for
Pseudomonas
aeruginosa
Currently the FDA requires that commercial susceptibility tests detect 98.5% of resistant isolates for
all drug/microorganism combinations. Our vendor for susceptibility testing has placed the following
caution on the testing of P. aeruginosa against Piperacillin, “an alternate method must be used to
confirm the results for this combination when the antimicrobic is being considered for treatment.”
Full
implementation
of new anaerobic
culture
procedures
In the January issue of the Laboratory Bulletin, we indicated that we were planning to change our
anaerobe culture procedures. We have not received any communications of concern related to these
changes and are implementing the new procedures. For anaerobes other than Clostridium
perfringens and Bacteroides fragilis group, we will simply give a presumptive identification based
on an aerotolerance test to prove the isolate is an anaerobe and the Gram stain. We will also include
the comment, If further work-up is required, contact the Laboratory at ext 3051 within 24 hrs. If
there are any questions or concerns, please contact the laboratory.
Based on this recommendation, we will discontinue routinely reporting Piperacillin when testing
P. aeruginosa using our automated method. If Piperacillin is being considered for treatment, the
physician must notify the laboratory and the susceptibility will be performed by a standard overnight
disk susceptibility test.
Karl T. Kleeman, Ph.D.
Karl T. Kleeman, Ph.D.
Rapid turnaround
on Gram stains of
normally sterile
body fluids
For some time the laboratory has been providing a one hour or less turnaround time for Gram stains
of CSF. The laboratory has now extended this service to include all Gram stains of normally sterile
body fluids including joint, synovial, pleural, peritoneal, pericardial and other fluids. Because, if
properly collected, these fluids should be sterile, the presence of microorganisms on the Gram stain
should be considered clinically significant.
Karl T. Kleeman, Ph.D.
Robin Ivosic, Core Laboratory Manager
National Medical
Laboratory Week
Rex Healthcare Laboratories, along with the American Society of Clinical Pathologists (ASCP) and
more than 12,000 other laboratories across the country, will be celebrating National Medical
Laboratory Week, April 14-20, 1996. The theme is “Helping You Have A Healthy Tomorrow”.
There are about 2,000 different types of tests available in medical laboratories. A host of these,
including the urinalysis, thyroid functions, throat cultures, and a variety of blood tests are among the
most useful and least expensive diagnostic procedures performed. By supervising, carefully
performing quality tests and providing timely consultation, our highly trained professionals help
physicians make diagnoses early, when cures are most likely!
Karen T. Sanderson, Specialty Laboratories Manager
For further information, call the Laboratory (783-3040). Telephone extensions are: Dr. Benson (3059), Dr. Brainard (3056), Dr.
Carter (3058), Dr. Chiavetta (3040), Dr. Kanich (3057), Dr. Kleeman (3063), Dr. Nance (3286), Dr. Sorge (3062), Robin Ivosic (Core
Lab Manager 3053), Linda Lompa (Blood Services Manager 781-0220), Lynn Nichols (Rex Outreach 783-4488), Rex Outreach
Couriers (783-4400), Karen Sanderson (Specialty Labs Manager 3396), Greg Wilson (Customer Services Manager 3318).