By Carol A. Kemper, MD, FACP

Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center

Dr. Kemper reports no financial relationships relevant to this field of study.

Food Tray Contamination With MRSA/VRE

SOURCE: Kwon JH, Reske KA, Hink T, et al. An evaluation of the prevalence of vancomycin-resistant Enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) in hospital food. Infect Contr Hosp Epidemiol 2017;38;1373-1375.

Contamination of food with various bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and ESBL-containing gram negatives, has been well documented. These researchers examined contamination of hospital food being fed to patients for the presence of MRSA and vancomycin-resistant Enterococcus (VRE). Samples of food from meal trays were collected by patients as they were eating, and saved in sterile cups. Homogenized specimens were cultured on sheep blood agar. A total of 910 food specimens were collected from 149 patients. Eight (5%) patients were known to be infected or colonized previously with MRSA, and seven (5%) were infected or colonized previously with VRE. A concurrent analysis assessed contamination of food samples with Clostridium difficile.

Food specimens from 17 (11%) patients were positive for MRSA and 17 (11%) were positive for VRE. Positive cultures were obtained from all kinds of foodstuffs, including 5% of eggs, 5% of breads or other grains, 3% of meats, and 1% of chicken. Overall, 3.2% and 2.4% of food samples were positive for MRSA and VRE, respectively. The concurrent analysis also found that only 0.2% of food samples were positive for C. difficile.

Foodstuffs are a recognized source for MRSA and VRE — and cultures of food eaten by 11% patients in hospital were found to be positive for MRSA and/or VRE. Some of these patients were known to be infected or colonized previously with these resistant organisms, so it’s conceivable that patients themselves were the source for the contamination of some food samples. Four patients had positive clinical cultures for MRSA or VRE only after a positive food culture.

Even if some of the hospital food itself was not contaminated before reaching the patient, this study suggests two additional points:

  •  Having patients cleanse their hands before mealtime should be an important hospital activity. Handing patients a moist, soapy towelette for hand cleansing with their meal tray should be routine. This practice can reduce the risk of auto-infection with bacteria, especially with C. difficile.
  •  Food trays being removed from patient rooms may serve as a source for cross-contamination of mobile delivery carts and hospital foodservice personnel as trays are being carted through the hospital and back to the kitchen.

Hospital Ice Machines Contaminated With Bacteria

SOURCE: Kanwar A, et al. Hiding in plain sight: Contaminated ice machines are a potential source for dissemination of gram-negative bacteria and Candida species in healthcare facilities. Infect Control Hosp Epidemiol 2018; Jan. 31: doi: 10.1017/ice.2017.321. [Epub ahead of print].

These researchers conducted a point prevalence survey of all ice machines in five different hospitals and two nursing homes in their area. Protocols for cleaning and disinfecting machines on either a weekly or monthly basis were in place at each facility, although none of the facilities performed surveillance cultures or molecular methods to monitor cleaning.

First, machines were inspected visually for debris, and swab cultures were obtained from both the ice and water chutes. Water samples of 100 mL were collected for culture. Swabs for culture were obtained from 64 machines (3-16 samples per facility).

Visual inspection revealed that 63 of 64 machines (98%) had stagnant water in the pan; 38% had melting ice in the pan, 34% had dripping water, even when the water spout was not in use, and 27% had visible water sprayed on the surrounding countertops or floor. Many of the machines had visible soiling, food, or slime layers.

Gram-negative bacilli and/or Candida organisms were cultured from 100% of the drain pans, 72% of the pan grills, and 52% of the chutes. Swab cultures from 94% of the pans yielded > 100 colonies of gram-negative bacilli, including Enterobacteriaceae (60%), Pseudomonas spp. (26%), Serratia spp. (6%), Stenotrophomonas maltophilia (4%), and Acinetobacter spp. (3%). Of these, 7.7% were carbapenem resistant. All cultures of water and ice were negative. Five of the machines were tested again following cleaning and disinfection with a hydrogen peroxide disinfectant, and all cultures were negative.

Hospital staff were observed using the ice machine on 20 occasions. Staff touched the ice and/or water spouts in nine of 20 episodes (45%), and falling ice touched hands (as it fell into the pan) in 10 of 20 episodes (50%). Cultures of hands frequently yielded gram negatives and yeast.

This study provides a plausible explanation for contamination of ice machines on hospital units. Even if machines are cleaned and disinfected successfully on a regular basis, they may become contaminated quickly by the hands of staff, touching either spouts or falling ice, with contamination of biofilm.

Two quick remedies may be to require staff to cleanse their hands with alcohol hand gel prior to using an ice machine, and to have housekeeping personnel perform more frequent cleaning of machines. Improvement in the design for these machines also may help. For example, deeper pans may help reduce splashes and sprays of water, and different types of spouts or chutes that cannot be touched readily by personnel would reduce cross-contamination.

Significance of Toxocara Serologies?

SOURCE: Liu EW, Chastain HM, Shin SH, et al. Seroprevalence of antibodies to Toxocara species in the United States and associated risk factors, 2011-2014. Clin Infect Dis 2018;66:206-212.

In May 2014, the Centers for Disease Control listed Toxocara canis as one of the “five neglected parasite infections in the United States.” Earlier seroprevalence studies from the National Health and Nutrition Examination Survey (NHANES) from 1988–1994 found a 13.9% seroprevalence of T. canis antibodies in people 6 years of age or older living within the United States.

More recent data from NHANES 2011-2014 found an age-adjusted seroprevalence of T. canis of 5%. This amount is much less than earlier estimates, but nonetheless it suggests that up to 16 million Americans have been infected with T. canis at some point in their lives. This risk was not uniform, but was found to be greater in older people, people born outside the United States, African Americans, males, and those with lower educational levels, living below the poverty line, and living in more crowded households. A similar study, also published in 2017, found an almost identical seroprevalence rate of 5.1% of persons in the United States, with similar risk factors.

This classic “sandbox infection” may be associated rarely with encephalitis, seizure disorder, and blindness, especially in small children. More often it results in asymptomatic or relatively asymptomatic infection, with low-grade fever and malaise. Clinically significant illness with abdominal discomfort and cough could be missed — since those symptoms occur with many other illnesses.

However, concerns have been raised that occult Toxocara infection may be associated with developmental delays and learning disability, especially in lower-income children who are at greater risk for infection. Earlier case-control data from 1987 in the American Journal of Public Health, which examined 4,652 children in New York City, found an association of T. canis antibodies with higher eosinophil counts and serum IgE antibody levels. Cases also performed less well in neuropsychologic assessment, even when adjusted for lead levels, with a higher reported frequency of hyperactivity, although these differences were small and not statistically significant.

Data suggest that most pediatricians and clinicians know little about the epidemiology and treatment of Toxocara infection — and it seldom is considered in otherwise apparently healthy children. However, at the moment, answers to even the most basic questions about Toxocara are lacking. How often does ingestion of eggs lead to clinical infection? What is the clinical significance of T. canis antibodies in asymptomatic persons? Should asymptomatic individuals with positive serologies be treated? Should children or adults with eosinophilia, possibly related to allergies, and positive Toxocara serologies be treated pre-emptively?