No micro mediocrity
Microbiology is not the place to save money. If micro must be performed in-house, hire the most skilled, most experienced MICRO lab techs you can find/afford …
or send micro testing out. Mediocrity is not acceptable. Second, micro specimens can be extremely difficult to collect (i.e., deep-lung aspirations). If lab techs must perform Gram stains
and inoculate various special media, invest enough time to ensure they are comfortable with these tasks and invest in an on-call micro tech temporarily during training.
Only lab managers/pathologists can determine what level of micro testing is possible, based on budget, facility, and availability of reference-lab support (which is expensive).
Do not get painted into a corner because an administrator hates approving reference-lab payments. If you cannot sign out first-class work, wherever it may be performed by
whomever, the lab will be blamed, regardless of any limitations it suffers.
—Chuck Millstein, MBA, MT(ASCP), CLDir(NCA), Retired
The Gram stain
Ever since J.M.C. Gram devised the method for staining bacteria to distinguish among types, we have found ways to screw it up. The Gram stain is subjective; it resists standardization and is only as good as the tech performing it. The providers have devalued the Gram stain because of so many reporting errors. When a provider sees inconsistencies between initial Gram stain and culture results, that causes confusion, disappointment, loss of confidence in the lab and, ultimately, poor patient management.
This test deserves to gain back its status as the valuable tool it was meant to be. No other test in the microbiology department needs constant, repetitive continuing education and proficiency testing (PT). A true story: We do microbiology culturing for several smaller hospitals, whose labs perform STAT Gram stains. Since the labs are inspected by the College of American Pathologists, unknown samples for Gram stains are sent for evaluation to their sites. One particular lab’s techs kept failing the Gram-stain PT — and after failing several in a row, my lab was asked to find out why. The techs were reading Gram stains by high power 40X magnification, not 100X oil immersion!
Gram stains are cheap, fast, and can offer a wealth of real-time information. They should be considered a rapid, reliable tool for diagnosis and treatment of infections. Providers need confidence in the results to guide treatment decisions; many times, waiting for a culture result is not an option.
These suggestions are not new, nor are they profound:
1. If you read a slide prepared and stained by another person, you have far too much faith in your fellow man. If you read it, you stain it!
2. Speed up your decolorizer. If you buy a kit which contains all the components for the Gram stain, the decolorizer is usually very slow. 50/50 95% ethanol/acetone works best. Make your own — far cheaper than buying it prepared.
3. Do not Gram stain stool smears! Use the Kinyoun’s acid-fast stain. Inflammatory cells (white blood cells, or WBCs) are far more visible. The added bonus? Spotting acid-fast parasites.
4. For sputum smears, place a drop of sputum on a slide, lay another slide on top, gently press together, then pull the slides apart; the technique makes a thin slide that stains more uniformly.
5. Blue WBCs mean the bacteria surrounding them are not stained correctly. This is Micro 101, but I still find techs reading and reporting results from these poorly stained slides.
6. Gram-positive bacteria pop out; do not stop looking. The smaller, lighter-staining Gram-negative organisms are often overlooked in polymicrobial smears.
7. Yeast and cocci can look like stain precipitate, and stain precipitate can look like yeast and cocci. Get a second opinion, or make another smear.
Sometimes, the Gram stain is more helpful than the culture; desquamative inflammatory vaginitis would be missed with culture alone done. Predominance of beta-hemolytic Streptococcus (most often Group B) and absence of lactobacilli would be the only clues. This would seem a normal culture in a non-pregnant adult since some strains of lactobacilli are anaerobic or microaerophilic. Gram stain would reveal an abundance of inflammatory cells, many Gram-positive cocci, and no or rare lactobacilli in a middle-age or post-menopausal vaginal specimen.
In
Lemiere’s disease— the “forgotten disease” since many doctors are unaware of it — patients
(usually young, healthy adults) start out with pharyngitis, which creates a peritonsillar abscess where anaerobic bacteria can flourish and penetrate into the neighboring jugular vein in the neck.
There, they cause an infected clot to form, pieces of which break off and cause serious, often life-threatening systemic disease. Gram stain of the abscess material will show a
polymicrobial infection with a predominance of distinctive Gram-negative Fusobacterium rods. To recognize and report these to the provider in the initial Gram stain
will help him identify Lemiere’s syndrome and jump-start appropriate antimicrobial therapy. Fusobacterium spp can take up to five days to grow in culture.
Aspiration pneumonia is an infection caused by aspiration of the normal upper respiratory flora into the sterile lower respiratory tract.
If culture alone were performed, only normal upper respiratory flora would be identified and reported — which would probably be dismissed by the provider.
The Gram stain, however, would show an abundance of inflammatory cells that have phagocytized a wide assortment of morphotypes.
A report like this would be helpful: “Many intracellular mixed bacteria consistent with aspiration pneumonia.
Treatment should include coverage for anaerobic as well as aerobic bacteria.”
Bacterial Vaginosis (BV)
should be identified by Gram stain not culture. Teach techs to recognize and report this from the microscopic exam.
Culturing for Gardnerella can lead to overdiagnosis because small to moderate numbers can be present in the healthy vagina.
Believing the Gram stain over the culture
: Streptococcus pneumoniae is a fastidious organism that can perish during prolonged transport times.
The Gram stain can look like a classic case of Streptococcus pneumonia pneumonitis, and the culture will only grow out normal upper respiratory flora.
Trust your Gram stain; explain the discrepancy to the provider.
My advice to every microbiology lab is to continuously test the proficiency of the techs doing Gram stains. Pass one gross specimen around.
Have techs make the smear from the gross specimen, then stain and read it. This is the best way to do a thorough proficiency examination and pinpoint a deficiency at any stage.
—Colleen K. Gannon, MT(AMT), HEW,
The “Nancy Grace” for labs
