Answering your questions

Aug. 1, 2010

Hemacytometer cleaning

Q What are the guidelines for manually cleaning hemacytometers after use?

A When using glass hemacytometers, it is imperative that they are clean and free of debris. Manual cell counting provides many opportunities for procedural errors. Procedural errors can occur when preparing dilutions and plating chambers, or from the presence of debris on the hemacytometer or coverslip.

In researching hemacytometer cleaning, similarities can be found in all cleaning protocols. In general, the following procedural steps are most common:

1. Rinse the surface of the hemaytometer and coverslip with water or a mild cleaning solution (70% ethanol or 10% bleach).

a. Rinse with 70% alcohol or an alcohol pad if a diluted bleach solution or water was used in the first step.

2. Dry the hemacytometer and coverslip with a lint-free soft cloth, being careful not to scratch the surfaces.

3. When not in use, store the hemacytometer and coverslips in a container to help keep them free from dust and scratches.

As a final note, users must use protective clothing, follow chemical and biologic safety precautions, and dispose of any contaminated articles in the appropriate biohazard or chemical-waste receptacles.

—Debbie Bennes, BS, MLT
Education Specialist
Hematopathology Morphology
Instructor in Laboratory Medicine and Pathology
Mayo Clinic
Rochester, MN

Further reading

  1. Turgeon ML. Linn'e & Ringsrud's Clinical Laboratory Science, The Basics and Routine Techniques 5th ed. 2007. St. Louis, MO: Elsevier. 2007:272.
  2. Rodak BF. Hematology, Clinical Principles and Applications, 2nd ed. 2002. Philadelphia, PA: W.B. Saunders Company. 2002:154-158.
  3. Hausser BrightLine Directions for Use (2010). Accessed June 7, 2010

Gloves required for reading culture plates?

Q Recently I was involved in a discussion of the Universal Precautions requirement to wear gloves while handling potentially infectious substances. Does this regulation include reading culture plates, like urine, sputum, blood, or stools? Are gloves required for reading culture plates?

A The use of gloves while reading microbiology plates and subcultures has been a controversial one ever since Occupational Safety and Health Administration's (OSHA) Bloodborne Pathogen Standard was released in 1991. In January 1993, OSHA published an interpretive quip stating, “Gloves are not necessary when handling subcultures as long as hand contact with blood or other potentially infectious material or contaminated surfaces is not anticipated. It is our understanding that this position is consistent with the U.S. Department of Health and Human Services, the U.S. Public Service, Centers for Disease Control and Prevention (CDC), and National Institutes of Health guidelines.”

According to Frank O. Wegerhoff, PhD, director of Global Microbiology at Covance CLS in Indianapolis, IN, College of American Pathologists' regulations and biosafety level 2 (BSL-2) laboratory requirements do not require gloves while handling culture plates or tubes. Standard precautions require gloves when dealing with specimens containing blood or body fluids to avoid bloodborne pathogens; handling plates and tubes do not qualify for this restriction. There is a statement in the NIH document Biosafety in Biomedical and Microbiological Laboratories document, section C4, which states, “Gloves are worn when hands may contact potentially infectious materials, contaminated surfaces, or equipment.” This statement, however, actually refers to the manipulation of raw specimens and not subsequent handling of cultures of organisms in petri dishes or tubes.

Dr. Wegerhoff further states that in the American Society for Microbiology (ASM) Division C (Clinical Microbiology) Newsletter (Spring 1992, Vol. 4, page 2), the ASM Safety Subcommittee states, “gloves may be required for plating of most patient specimens but should not be required for subsequent culture evaluation of most organisms. In most cases, the microbiologic tubes and culture plates that are managed on subsequent days during culture evaluation do not need to be handled with gloves.” This same ASM subcommittee worked with officials from the Clinical and Laboratory Standards Institute (CLSI), OSHA, CDC, and various accrediting and regulatory agencies in an attempt to ensure that effective, evidence-based safety protocols are implemented, avoiding unsubstantiated procedures.

An article in Applied Biosafety, Vol. 14, No.1, 2009, by Karen B. Byers from the Dana-Farber Cancer Institute in Boston, MA, described the importance of handwashing for good infection control. She also points out that the 2005 Journal of Clinical Microbiology calls for the enforcement of CDC BSL-2 practices but has documentation of four U.S. cases of infection with Escherichia coli contracted when performing microbiological procedures while not wearing gloves.

Currently, it is up to the individual lab facility to develop and implement its own rules on when wearing gloves is required. CLSI documents M29 and GP17 are under revision and may provide more specific information and rationale in the future.

—Terry Jo Gile, MT(ASCP), MA Ed
The Safety Lady
North Fort Myers, FL

Brad S. Karon, MD, PhD, is associate professor of laboratory medicine and pathology, and director of the Hospital Clinical Laboratories, point-of-care testing, and phlebotomy services at Mayo Clinic in Rochester, MN.

MLO's “Tips from the Clinical Experts” provides practical, up-to-date solutions to readers' technical and clinical issues from a panel of experts in various fields. Readers may send questions to Brad S. Karon, MD, PhD, by e-mail at [email protected].