Hospitals Can Be A Hotbed Of Cross Contamination Opportunities

Hospitals Can Be A Hotbed Of Cross Contamination Opportunities

By Kelly M. Pyrek

The opportunities for bacterial cross-contamination are numerous in the healthcare environment. This article will highlight both the expected and unexpected opportunities for cross contamination in a hospital's kitchen, operating room and central sterile department.


Many cases of foodborne illness are caused by the consumption of ready-to-eat foods contaminated by poor handling techniques and the cross contamination between raw and finished food products. Seventy-five million cases of foodborne illness occur each year in the United States; of these cases, 325,000 hospitalizations and 5,000 deaths resulted according to a 1999 study by the Centers for Disease Control and Prevention (CDC). These statistics are particularly frightening, considering that food service in hospitals impacts a large group of immunosuppressed individuals who are open to opportunistic pathogens.

A team of researchers at the North Carolina State University and Research Triangle Institute decided to estimate the degree of risk to human health posed by cross contamination during food preparation and conducted an exposure assessment to address the likelihood and routes of transmitting Salmonella and Campylobacter jejuni during food handling.

Various food-handling scenarios were designed to model cross contamination from raw to cooked foods via contaminated hands, countertops, cutting boards and dishcloths, and laboratory investigations provided data concerning the transfer rate of pathogens. Simulations estimated that in most cases, less than 1 percent of pathogens were transmitted during food handling. Taking into account pathogen survival rates on surfaces and marginal cleaning efforts during food preparation, an initial Salmonella level of 100 CFU/ml in meat exudates would result in a mean level of 0.056 CFU/g for food contaminated through contact with contaminated hands, countertops and dishcloths. The researchers say that while this level of contamination may seem small, the levels of contamination may be significantly higher when considering cases of "gross mishandling" during food preparation. The study shows that exposure levels are greatly influenced by survival and transfer rates during pathogen transmission.

When inservicing kitchen workers about cross contamination, infection control practitioners (ICPs) may want to consider addressing the potential hazard of "wet-nesting" of foodservice dishware, explored by researcher Danielle Hautenne-Dekay, a clinical dietitian at Swedish Medical Center in Ballard, Wash., and her team in the August 2001 issue of the Journal of the American Dietetic Association.

According to The American Dietetic Association (ADA), changes in demographics and lifestyles have contributed to the increase in foodborne illness observed during the last 20 years. Americans now consume more meals from commercial foodservice establishments -- including healthcare facilities -- where high employee turnover, an unskilled foodservice labor force and increased demand present more opportunity for cross contamination of food items than ever before.

One aspect of food safety, according to the ADA, is the proper sanitation of dishware on which food is served. The 1999 Food and Drug Administration (FDA) Food Code specifies air-drying of all dishware as an important step in preventing bacterial growth on food-contact surfaces. The code states, "Items must be allowed to drain and to air-dry before being stacked or stored. Stacking wet items such as pans prevents them from drying and may allow an environment where microorganisms can begin to grow." This stacking of dishes before being completely air-dried is called wet-nesting.

Kitchen managers evaluate their operations based on the FDA Food Code; however, no scientific evidence implicating wet-nesting as a food safety concern has been gathered. A study at the Veterans Affairs Medical Center in Portland, Ore., was conducted to determine if wet-nesting of serving plates increased the incidence of foodborne illness.

In the study, samples were taken from 100 randomly selected breakfast serving plates returned to the patient foodservice kitchen. Cultures were taken from soiled plates after excess waste had been scraped away. A template of the 9 1/8-in serving plates was made with a 3x3-inch square cut out of the center to ensure consistency in the areas swabbed.

Sterile cotton-tipped swabs were moistened with 0.85 percent saline solution immediately before touching the soiled serving plates. A total of 40 zigzag stokes were made, starting in the upper left-hand corner and moving to the bottom right. The swab was immediately placed in a test tube containing 2 mL tryptic soy broth obtained from the hospital's microbiology laboratory, sealed and taken immediately to the microbiology laboratory. After vortex mixing for 10 seconds, 0.1 mL broth from each sample was spread evenly over individual blood agar plates. The plates were incubated for 24 hours; following incubation, bacterial growth was determined by visual inspection for colony-forming units. A count was then made of the number of blood agar plates having colony-forming units. The lower level of detection with this method is 10 colony-forming units per milliliter of broth.

The sanitizing equipment used in the study was a dishwashing machine with all temperature requirements met during all cycles (prerinse 160 degrees to 180 degrees F, wash 150 degrees to 170 degrees F and final rinse 180 degrees to 195 degrees F). Fifty of the 100 sample plates were run through the dishwashing machine and retrieved after completing the full cycle. The plates were immediately placed in stacks of 10 plates each. In between each plate, 5 mL sterile water was added to ensure a moist environment. These wet-nested serving plates were allowed to sit for 24 hours and were swabbed again using the previously stated method. The remaining 50 soiled plates were run through the dishwashing cycle but were allowed to air-dry separately for 24 hours placed vertically in a dish rack in a dry, low traffic area of the kitchen. These clean, air-dried plates were swabbed and plated using the previously stated methods.

The original tryptic soy broth samples from the wet-nested and air-dried plates were incubated for a second 24-hour period to allow additional time for bacterial growth.

Even though 95 of 100 plates showed bacterial contamination before dishwashing, no significant difference in bacterial growth was found between air-dried and wet-nested plates in the first 24 hours, but a significant difference was found after 48 hours.

Testing for specific microorganisms was not completed because of financial constraints; however, researchers presumed the microbial load consisted of normal mouth flora such as Streptococci and Staphylococci.

According to the author, "The data show that wet-nesting of dishware, if held for long periods before reuse, may be of concern in specific foodservice operations, particularly in hospital and other foodservice operations that provide meals for immunocompromised persons. This suggests the need for further study on the range of identifiable microorganisms that can survive current dishwashing temperature/chemical decontamination standards. Additional bacteria may survive when dishware is washed either by hand or by a less-effective dishwashing machine or when dishes are held for extended periods of time. Wet-nesting of dishes does not appear to pose a serious risk for bacterial contamination of food when dishware is sanitized with proper equipment and chemicals at appropriate temperatures. However, wet-nesting may pose a threat if dishes are allowed to sit for longer than 24 hours before being used."


The key to minimizing the spread of infection is to decrease opportunities for cross contamination, especially in patient rooms where direct care is given. Infection control experts agree that handwashing is the most critical procedure for preventing the spread of infection. According to the Association for Professionals in Infection Control and Epidemiology (APIC), hands should be washed after contact with body fluids, soiled linen, waste or contaminated equipment; after removing gloves; before and after performing clean or sterile procedures; between tasks on different body parts of the same resident; between resident contacts; and before and after eating, drinking, smoking, applying cosmetics or preparing food.


The CDC states that linens should be handled as little as possible and with minimum agitation. Sheets should be rolled when removed from the bed to reduce transmitting airborne bacteria. Soiled linens should be bagged to contain bacteria and then transported, preferably in covered containers, which should be cleaned on a regular basis. Sorting soiled linen prior to washing minimizes exposure of facility and laundry personnel to potentially infectious material. A hot-cycle wash should be used, and clean linens should be stored in covered containers or shelves.

It is recommended that environmental services personnel monitor environmental cleanliness by doing rounds with a checklist for each area of the facility. APIC suggests the following points to keep in mind when cleaning resident and public areas of hospitals:

  • Work from the top to bottom of a room and from the least to most contaminated areas
  • Remove debris before mopping
  • Change cleaning solutions and mop heads frequently
  • Use a closed-cleaning system that provides a new product every time and store all equipment clean at the end of the day.

Infectious waste, categorized as items contaminated with blood and other potentially infectious body fluids, should be contained in leak-proof bags or containers that will resist ripping, tearing or bursting during handling. Containers of infectious waste should be color-coded or labeled, large enough to contain various forms of waste and closed prior to removal to prevent spilling. Disposable sharp items should be packaged or maintained in puncture-resistant, leak-proof containers that are labeled with a red color or "biohazard" label.

A number of factors can contribute to cross contamination in the hospital building itself, according to Alvin Chapital, healthcare market segment manager for Kimberly-Clark. Walls, floors, furniture and countertops should be selected for ease of maintenance, cleaning and disinfection. In bathroom areas, no-touch products can reduce the transmission of bacteria, and faucets, towel, tissue and soap dispensers, light switches and toilet flushing devices can be purchased with an electronic sensor that detects motion and activates automatically.


There has been no shortage of news headlines announcing a large number of infections that have been traced to improperly cleaned, disinfected and sterilized surgical instruments and endoscopes. Bioburden allowed to dry and remain on these instruments will endanger the health and safety of the patient who is operated on next. To help operating room personnel avoid surgical site infections, central sterile/sterile processing personnel must understand the mechanisms of cross contamination as they apply to this department. Debris left in the lumens and channels of an endoscope used on one patient will introduce pathogens to the next patient unless the chain of infection is broken and the surgical instrument is prepped correctly, following the hospital's guidelines for cleaning, disinfection, sterilization, assembly and wrapping.

When the case cart is delivered to the operating room, its access by healthcare workers (HCWs) should be limited in order to protect package integrity and prevent cross contamination. Every time a package is handled, contaminants from a HCWs' hands that were picked up from other animate or inanimate objects can be transmitted to the package surface, allowing pathogens to enter through microscopic holes or tears in the wrapping material.


Getting the OR ready is a prime opportunity for cross contamination if personnel are not careful in opening sterile supplies, setting up the sterile field with instruments for the surgical procedure and preparing the patient for surgery. Following aseptic principles and techniques can create and maintain a clean surgical environment, according to Cathy Osman, RN, BS, CNOR. She explains that key infection control measures in the OR must focus on preventing cross contamination and ensure a smooth traffic flow of entrance to exit or clean to dirty areas in a series of clearly delineated unrestricted and restricted areas.

"Good traffic control practices protect personnel, patients, supplies and equipment from potential sources of cross contamination," she says.

The unrestricted area usually includes entrances and exits to the surgical suite, as well as patient-holding areas, post-anesthesia recovery units, supply-receiving areas, offices and locker rooms. The restricted area includes the OR and adjacent substerile areas, and surgical attire must be worn by personnel. Masks are required when sterile supplies are open or when scrubbed personnel are present, according to practices recommended by the Association of periOperative Registered Nurses (AORN). Supplies and equipment, not just surgical personnel, must also follow designated traffic patterns so as not to undermine surgical environmental controls.

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