Bacterial contamination of enteral feeds as a possible risk of nosocomial infection

Safety of Enteral Nutrition Practices: Overcoming the Contamination Challenges

Enteral nutrition (EN) has host of benefits to offer to critically ill patients and is the preferred route of feeding over parenteral nutrition. But along with the many outcome benefits of enteral feeding come the potential for adverse effects that includes gastrointestinal (GI) disturbances mainly attributed to contaminated feeds. Currently, EN is practiced using blenderized/kitchen prepared feeds or scientifically developed commercial feeds. Commercial feeds based on their formulation may be divided as ready-to-mix powder formulas or ready-to-hang sterile liquid formulas. A holistic view on potential sterility of EN from preparation to patient delivery would be looked upon. These sterility issues may potentially result in clinical complications, and hence process-related errors need to be eliminated in hospital practice, since immunocompromised intensive care unit patients are at high risk of infection. This review intends to discuss the various EN practices, risk of contamination, and ways to overcome the same for better nutrition delivery to the patients. Among the various types of enteral formulas and delivery methods, this article tries to summarize several benefits and risks associated with each delivery system using the currently available literature.

How to cite this article

Sinha S, Lath G, Rao S. Safety of Enteral Nutrition Practices: Overcoming the Contamination Challenges. Indian J Crit Care Med 2020;24(8):709-712.

An Anthology of Advances in Enteral Tube Feeding Formulations

This article summarizes several major advances in tube feeding formulas marketed in the United States. It traces the progress in tube feeding formulas, starting with blenderized formulas to commercially available intact-nutrient formulas and culminating in the introduction of the concept of immunonutrition. The impact of packaging is also described.

A Microbiologic Study of Enteral Feeding Hang Time in a Burn Hospital: Can Feeding Costs be Reduced Without Compromising Patient Safety?

BACKGROUND

Procedural changes for hospitalized patients must always balance safety with fiscal constraints. Microbiologic contamination of enteral feeding solutions has been previously associated with nosocomial infections. Formula manipulation and hang time contribute to microbial load, and there is considerable variation in hang time recommendations in the medical literature. With cost containment in mind, the purpose of this performance improvement study was to determine if an increase in hang time of a modular tube feeding product would increase microbial load or affect the nosocomial infection rate in pediatric burn patients.

METHODS

This biphasic trial initially evaluated the microbial load of the feeding after delivery of two 4-hour aliquots into a container using the same delivery set (total hang time of 8 hours; number of tests = 20). Second, once this feeding procedure was deemed microbiologically safe, tube feedings were administered to patients, and both microbial load and nosocomial infection rate were monitored for 1 year.

RESULTS

Contamination levels at the end of the 8-hour period using the same feeding set with 2 consecutive 4-hour feeding aliquots (number of tests = 38) were lower than standard recommendations. The hospital's nosocomial infection rate was not altered by this procedural change, and feeding-set expenses were reduced.

CONCLUSIONS

The hang time of our enteral feeding administration set can be increased safely from 4 hours to 8 hours, with the tube feeding preparation added as two 4-hour aliquots without a significant change in microbial load or nosocomial infection rate, thus promoting simultaneous fiscal responsibility and patient safety.

Detecting Enteral Nutrition Residues and Microorganism Proliferation in Feeding Tubes via Real-Time Imaging

BACKGROUND

Enteral nutrition (EN) residues that persist in feeding tubes provide substrates for microorganisms to proliferate and occlude the tubes. Visible EN residues in tubes are easily identified, but smaller residues can persist. We developed a new imaging technique to visualize EN residues and proliferation of microorganisms in feeding tubes.

MATERIALS AND METHODS

(1) Feeding tubes containing EN labeled with fluorescent dye and either with or without various types or amounts of thickeners were flushed once with water and then seeded with Pseudomonas aeruginosa Xen05 with recombinant luciferase DNA. (2) Because EN fluoresces intrinsically, EN in the feeding tubes without fluorescent dye was repeatedly flushed until the intrinsic fluorescence levels reached background levels. Fluorescent images of EN residues and bioluminescent images of microorganisms were acquired via an optical imaging system.

RESULTS

(1) Fluorescence images showed that the amount of EN residues increased at various sites in tubes depending on EN viscosity and the thickening agent, and bioluminescence images showed that microorganism proliferation was associated with a commensurate increase in EN residues. (2) The intrinsic fluorescence of EN also enabled the detection of EN residues in tubes even in the absence of fluorescence dye. Higher EN viscosity required more flushes to reach undetectable levels.

CONCLUSION

EN residues and microorganism proliferation in enteral feeding tubes were detected on fluorescence and bioluminescence images, respectively. This simplified approach allowed the real-time visualization of EN residues and microorganisms in feeding tubes.

ASPEN Safe Practices for Enteral Nutrition Therapy [Formula: see text]

Enteral nutrition (EN) is a valuable clinical intervention for patients of all ages in a variety of care settings. Along with its many outcome benefits come the potential for adverse effects. These safety issues are the result of clinical complications and of process-related errors. The latter can occur at any step from patient assessment, prescribing, and order review, to product selection, labeling, and administration. To maximize the benefits of EN while minimizing adverse events requires that a systematic approach of care be in place. This includes open communication, standardization, and incorporation of best practices into the EN process. This document provides recommendations based on the available evidence and expert consensus for safe practices, across each step of the process, for all those involved in caring for patients receiving EN.

Formulation of a nasogastric liquid feed and shelf-life extension using gamma radiation

Nasogastric liquid feed formulation (NGLF) was developed for immunocompromised patients who are vulnerable targets of pathogenic assault. NGLF consisted of cereals, pulses, vegetables, and milk powder to provide balanced nutrients; however, the shelf life was only a few hours because this product was highly prone to microbial contamination and proliferation due to its high water content and rich nutrients. Postpreparation storage and distribution was very difficult, even at chilled temperatures. To overcome this problem, the NGLF was irradiated at various doses (2.5 to 10 kGy). Gamma irradiation at 10 kGy reduced the microbial load to nondetectable levels, and the product could be stored up to 1 month without any detectable increase in microbial load. The sensory evaluation did not indicate differences between the nonirradiated fresh, irradiated fresh, and stored samples. Nutritional quality in terms of total carbohydrates, dietary fiber, proteins, calories, vitamins A and C, and the micronutrients calcium, iron, and zinc was not affected by irradiation. NGLF also possessed antimutagenic potential against ethylmethanesulphonate-induced mutagenesis in Escherichia coli cells as evaluated by the rifampin resistance assay. This property of NGLF remained unchanged even after exposure to a 10-kGy dose of gamma radiation. Thus, irradiated NGLF seemed to be a safe and wholesome food for immunocompromised patients.

Analysis of sites of bacterial contamination in an enteral feeding system

BACKGROUND

Contamination of enteral feedings is an often overlooked source for bacterial infection in the intensive care unit. A new 1-L enteral feeding system with minimal chances of touching critical areas (Nutrison Pack) was compared with routinely used 0.5-L glass bottle systems.

METHODS

Patients admitted to intensive care were randomized to Pack or glass bottle feeding systems. Cultures were taken from the delivery sets 5 times during the day and from feeding containers and different sites of the system after 24 hours.

RESULTS

Bacteria were present in 3 of 112 glass bottles and in 2 of 95 Pack bags. True bacterial contamination (defined as >10(2) colony-forming units/mL, with same bacteria also present in the delivery set) was found in none of the Packs with a 12-h (69 Packs) or a 24-h (26 Packs) hanging time and in only 1 of the glass bottles with a hanging time of 24 hours, which exceeded the advised hanging time of 8 hours. In contrast, the contamination rate of delivery sets was 48%, with increasing bacterial counts over the day and 4 subsequent days. Bacteria mainly belonged to the group of potentially pathogenic bacteria (Enterobacteriaceae and Pseudomonaceae). They likely originated from throat, lungs, and stomach and grew into and along feeding tubes upwards until they reached the delivery set.

CONCLUSIONS

Prolonged hanging times of Pack bags were safe with respect to bacterial contamination. However, the bacterial safety of enteral feedings is more likely to be endangered by the endogenous route of contamination rather than exogenous contamination, as high bacterial counts were found in feeding tubes and delivery sets as a result of retrograde growth.

Enterobacter sakazakii: a coliform of increased concern to infant health

The first cases of neonatal meningitis believed to have been caused by Enterobacter sakazakii were reported in 1961. Prompted by several subsequent outbreaks of E. sakazakii infections in neonates and an increasing number of neonates in intensive care units being fed rehydrated powdered infant formula, considered to be a source of the pathogen, public health authorities and researchers are exploring ways to eliminate the bacterium or control its growth in dry infant formula, processing environments and formula preparation areas in hospitals. Reviewed here are advances in taxonomy and classification of E. sakazakii, methods of detecting, isolating and typing the bacterium, antibiotic resistance, clinical etiology and pathogenicity. Outbreaks of E. sakazakii infections in neonates and adults are summarized. Reports on the presence of E. sakazakii in clinical settings, the environment and foods and food processing facilities are reviewed. Tolerance of the pathogen to environmental stresses, its behavior in powdered and rehydrated infant formulae and hazard analysis and risk management are discussed. Research needs are presented.

Antimicrobial resistance in Gram-negative bacilli isolated from infant formulas

A total of 90 samples of infant formula (IF) were collected from the lactary of a teaching hospital, during a 4-month period from July to August 1999. The sanitary conditions of the formulas were analyzed, and a physiological characterization of Gram-negative bacillus isolates and antimicrobial susceptibility testing were performed. Colony counts were considered to be unacceptable for the majority of the IF samples and the contamination rates were related to inadequate handling. Coliforms (35 degrees C and 45 degrees C growth) were detected in most of the IF tested. Klebsiella pneumoniae, Citrobacter freundii, Cedacea davisae, Klebsiella planticola and Enterobacter cloacae were the isolates most commonly identified. Antimicrobial susceptibility testing showed significant resistance rates, particularly to amoxicillin/clavulanic acid, cefoxitin, cephalotin or ampicillin. One extended-spectrum beta-lactamase-producing K. pneumoniae strain was also recovered.

Is a 24-h cyclic closed enteral feeding system microbiologically safe in geriatric patients?

BACKGROUND AND AIMS

The microbiological quality of a 1-l closed enteral feeding system (CS) was prospectively monitored under clinical conditions simulating cyclic feeding over a 24-h period in geriatric patients.

METHOD

The set was connected after diet sampling (T0). After 5-h feeding, the set was disconnected and a sample taken (T5). Diet was sampled after 12 h before (T12A) and after a 10 ml diet-flush of the set (T12B), after 24-h (T24) and in the pouch (P24). Concentrations of micro-organisms were considered significant when above 10(4) colony-forming units per millilitre.

RESULTS

Twenty-one CS were examined. T0 samples were all sterile; 10 out of 21 T5 were contaminated. The microbiological content of the diet was lower in T12B, compared to T12A (P=0.002). None of the P24 samples was contaminated; 19 were sterile and two contained low levels of micro-organisms that had been previously found in the sets.

CONCLUSION

The CS was sterile before connecting to the patient. Retrograde contamination of the set was observed without contamination of the pouch after 24-h hanging time. Performing a diet-flush decreased the rate of diet contamination at the distal extremity of the set. Thus, cyclic enteral nutrition using the same pouch during a 24-h period seems to be safe in geriatric patients.

Comparison of microbial contamination of enteral feeding solution between repeated use of administration sets after washing with water and after washing followed by disinfection

We compared microbial contamination of in-use enteral feeding solution from repeatedly used administration sets (a delivery bag and an infusion tube) after washing with water or washing followed by disinfection. In eight hospitals where administration sets were re-used after washing with water, residual solution was collected from both the delivery bag and the distal end of the infusion tube immediately after use and the microbial contamination level and microbial species found examined. The residual enteral feeding solution (28 samples) in the delivery bag grew 10(2)-10(8) colony forming units (cfu)/mL and 36 samples from the distal end of the infusion tube grew 10(2)-10(9) cfu/mL. Re-processing was changed to washing with water followed by disinfection with 0.1% (100 ppm) sodium hypochlorite, and similar examinations were performed. The residual solutions in the bag (22 samples) and in the distal end of the infusion tube (24 samples) were contaminated with < 10(1)-10(4) cfu/mL each, a significant decrease (P < 0.01, Wilcoxon U-test) compared with washing with water alone.

The effect of poor handling procedures on enteral feeding systems in Hong Kong

Two enteral feeding systems commonly used in Hong Kong were evaluated for ease of bacterial entry during assembly and delivery of feeds. Wearing new, non-sterile disposable latex gloves during the assembly of the systems did not contaminate the feeds. The risk of contamination increased for systems assembled with bare hands. Systems assembled with hands experimentally contaminated with bacteria resulted in definite contamination of feeds.

Hormonal response to enteral feeding and the possiblerole of peptide YY in pathogenesis of enteral feeding-related diarrhoea

Diarrhoea is a common complication of enteral feeding. Previous studies have demonstrated a secretion of water and electrolytes in the ascending colon during intragastric but not intraduodenal enteral feeding. The cause of this secretion is likely to be neurohumoral in origin. This study was designed to examine the hormonal responses to enteral feeding. In vivo segmental colonic perfusion studies were undertaken. Before and at hourly intervals during these studies serum was taken for estimations of neurotensin (NT), pancreatic glucagon (PG), peptide YY (PYY) and vasoactive intestinal polypeptide (VIP). During fasting there was a median ascending colonic absorption of water in all groups. During feeding there was a net secretion in the ascending colon in both gastric groups and in the high load duodenal group, but not in the low load duodenal group. During these studies the PYY levels remained unchanged from fasting in the low and high load gastric groups. In the low and high load duodenal groups the PYY levels increased. The NT levels increased only in the high load duodenal group. There were no other changes in NT or in PG or VIP levels either between fasting and feeding, or between the gastric and duodenal groups. PYY is known to stimulate intestinal absorption. The absence of a rise during intragastric feeding may be important in the underlying mechanisms of enteral feeding-induced colonic secretion and hence enteral feeding-related diarrhoea.

Killing activity of microwaves in milk

The killing activity of microwaves of 2450 MHz frequency and 600 W power on Pseudomonas aeruginosa, Escherichia coli, Enterobacter sakazakii, Klebsiella pneumoniae, Staphylococcus aureus, Candida albicans, Mycobacterium terrae and poliomyelitis vaccine-virus suspended in five infant formula preparations was investigated. The samples were brought to the boil (85-100 s depending on milk type). They had reached average temperatures of 82-93 degrees C at this point. Most of the vegetative organisms were killed. In those samples where growth was still detectable after microwave treatment, a significant reduction in viable micro-organisms (at least 5000-fold) was noted. We conclude that microwave beating to the boil is a convenient and fast method to reduce microbial contamination of infant feeds. However, care should be taken to ensure that milk is adequately cooled to the required temperature before it is fed to an infant.

Reducing bacterial contamination in enteral tube feeds

It is well known that enteral tube feeds may become contaminated with bacteria and other microorganisms during preparation and administration and that this may lead to the development of infectious complications in patients. This article describes potential sources and routes of microbial contamination of these feeds and suggests procedures that can be implemented to reduce the risk of contamination.

Outbreak of gentamicin, ciprofloxacin-resistant Pseudomonas aeruginosa in an intensive care unit, traced to contaminated quivers

An outbreak of gentamicin, ciprofloxacin-resistant Pseudomonas aeruginosa in an intensive care unit, was investigated. The majority of isolates were from sputum and the organism was not isolated from any other patient in the hospital, except those admitted to the unit. A prospective study was set up, and the organism was found to be associated with contaminated quivers, used to store suction tubing between use on ventilated patients. Once the quivers were disinfected and changed between patients daily, the outbreak stopped. Suction of ventilated patients may be an important source of contamination of the respiratory tract with nosocomial pathogens. It is important that infection control teams regularly review procedures to ensure the correct practices are being followed, so that nosocomial outbreaks of infection may be prevented.

Evaluation of "closed" vs "open" systems for the delivery of peptide-based enteral diets

BACKGROUND

The study was designed to quantitate factors such as preparation time, waste, and contamination associated with three different feeding systems for peptide-based diets and to determine appropriate hang times.

METHODS

Intensive care unit patients were randomized to receive a peptide-based diet in 1500-mL prefilled, sterile closed-system containers (CS) infused more than 24 hours, as open systems decanted from cans (OS-Can), or as open systems mixed from powder (OS-Powder). Open-system groups were provided a 12-hour supply twice daily in commercially clean 1-L bags with preattached sets. Samples were taken for culture during preparation and after infusion. Preparation time, initial and final microbial concentrations, and total waste were quantified.

RESULTS

Preparation time was significantly shorter for CS than for OS-Can or for OS-Powder (2 minutes vs 7.5 minutes vs 13.0 minutes). Initially, 100% of the OS-Powder and 30% of the OS-Can bags were contaminated, with significant contamination exceeding 10(4) colony-forming units/mL in 40% and in 5% of the bags, respectively. On final culture, significant contamination occurred in only 2% of the CS bags compared with 83% of the OS-Powder and 60% of the OS-Can bags. Average time from potential initial contamination to final culture in CS was 49.9 hours vs 38.8 hours for OS-Can and 32 hours for OS-Powder. Total waste was greater in CS than in OS-Can or OS-Powder but could be eliminated by extending allowable hang times.

CONCLUSIONS

Nonvented closed-delivery containers may be safely infused for up to 48 hours. They are associated with reduced labor and contamination.