Thesis & Dissertations

Contamination of intensive care unit environment with nosocomial bacteria: a meta-analysis


Background Nosocomial infections, especially those acquired in the ICU setting, are often severe, difficult to treat, and at substantial risk for recurrence. ICUs are important areas for the emergence and spread of nosocomial infections because of the frequent use of broad-spectrum antibiotics; the crowding of patients with high levels of disease acuity within relatively small, specialized areas; reductions in nursing staff and other support staff because of economic pressures, which increase the likelihood of person-to-person transmission of microorganisms; and the presence of more chronically and acutely ill patients with multiple catheters and instruments who require prolonged hospitalizations and often harbor antibiotic-resistant bacteria. Some of the most aggressive, resistant pathogens have become endemic in hospital environments, and many of these pathogens have established residence in ICUs. Examples of such pathogens are methicillin resistant Staphylococci – both Staphylococcus aureus and coagulase-negative Staphylococci – and the vancomycin-resistant Enterococcus. Additionally, resistant Gram negative pathogens, such as Acinetobacter baumannii, resistant strains of Pseudomonas aeruginosa, Klebsiella species, and Escherichia coli can establish endemic residence in the ICU and can result in clustered infections and unnecessary morbidity and mortality. The nosocomial reservoirs for these resistant organisms vary by the pathogen and the clinical setting. Certain organisms have a proclivity for establishing reservoirs in the inanimate environment in healthcare settings. Many such organisms find moist places in the environment and establish residence. These organisms often have extremely limited nutritional requirements and can survive even reasonably harsh conditions in the environment. Such organisms, once established in a reservoir, may cause recurring clustered infections in an environment. The potentially contaminated ICU environment, including contaminated equipment routinely used in the care of the critically ill patients, is ideal for the multiplication, persistence and spread of resistant nosocomial bacteria. In some situations, identifying the reservoir may be extremely difficult. The inanimate environment of the ICU contains several loci that can, in the absence of attention to the details of cleaning and infection control, present a serious problem for detection. 64 Infection control principles that have special relevance to the ICU setting which limit the spread of resistant nosocomial bacteria are the following: (1) implementation of administrative controls; (2) ensuring antimicrobial stewardship in the ICU; and (3) use of special infection control interventions (e.g., cohorting, special microbial surveillance programs, decontamination strategies, molecular typing of organisms, etc.) Aim This study is a meta-analysis of studies dealing with nosocomial bacteria contamination of inanimate surfaces surrounding ICU patients in outbreak and non-outbreak settings. The aim was identifying the most common contaminating bacteria in the ICU environment in addition to its inanimate reservoirs which act as fomites serving for cross-transmission among patients. Methods A review of published literature from several electronic databases was done. Extracted studies targeted nosocomial bacteria contamination of intensive care unit with a particular focus on the inanimate surfaces serving as reservoirs for pathogen cross transmission. Results In the General studies, (59%) environmental contamination was found in comparison to an average of (15%) contamination in the Outbreak studies. Gram positive contaminants were most seen in the General studies (37%) compared to the outbreaks (10%).However, Gram negative contamination was higher in the outbreaks (29%) than in the General studies (16%). In the General studies, the most common bacteria recovered from MICU environment were coagulase negative staphylococci showing the highest percentage of environmental contamination (37%), yet, Pseudomonas aeruginosa showed the least contamination (3%). With respect to bacterial resistance in the General group, vancomycin resistant Enterococcus showed the highest percentage of contamination 65 (29%), while methicillin resistant coagulase negative staphylococci showed the least contamination (6%). In the MICU outbreak studies, Pseudomonas aeruginosa was shown to be the most contaminating bacteria (17%) and the one most implicated in outbreaks (9 outbreaks).This was followed by the occurrence of Klebsiella pneumoniae, Sphingomonas paucimobilis (16%) and Staphylococcus aureus (15%). Acinetobacter baumannii showed to have close contamination (12%) and occurrence as Pseudomonas aeruginosa. This was unlike Escherichia coli which showed the least contamination and occurrence in outbreaks. With respect to bacterial resistance in the Outbreaks group, methicillin resistant staphylococcus aureus showed the highest level of contamination (43%). In the PICU outbreak studies, Enterobacter species showed the highest contamination (63%) and was recovered from 2 outbreaks followed by Serratia species (47%) and Escherichia coli (29%), yet Enterococci showed the least contamination (10%). Outbreaks caused by highly resistant bacteria were much less in the PICU where resistant strains of Klebsiella pneumoniae showed the highest contamination (11%). Several inanimate surfaces and equipment were found to be vectors for nosocomial bacteria transmission within the ICU environment. In the General studies, bedside curtains (65%), bath basins (62%) and radiograph equipment (63%) showed a similar percentage of contamination. However, staff mobile phones (95%), patients‟ charts (90%) and staff pens (80%) showed higher contamination percentage than the above listed fomites. In MICU outbreaks, bedside curtains along with taps showed (7%) contamination while water from devices showed higher contamination (19%).A variety of patient equipment was contaminated by bacteria where surgical scrub gallons were found to be the most contaminated objects (13%).Similarly, we found out that patients charts were contaminated as well (14%) along with HEPA air filters showing an (11%).Some reservoirs were repeatedly mentioned in outbreaks as sources of contamination and they 66 were the following: beds, bedside tables, sinks, taps, tap water, monitors, syringes, ventilators, work trolleys, door knobs and floors. In PICU outbreaks, enteral feeding tubes were found to be the most commonly contaminated object reaching (75%) contamination. This finding was followed by a (37%) tap water contamination and (13%) tap contamination. Conclusion Patient environment harboring antibiotic resistant bacteria often becomes colonized with the same bacteria due to lapses in infection control. These organisms persist in an appropriate environmental niche for weeks unless removed through appropriate disinfection process. These surfaces in addition to contaminated patient equipment have been linked to resistant bacteria transmission to critically ill patients in intensive care unit, leading to multiple outbreaks of healthcare acquired infections.




Prof. Mohamad Anwar, Prof. Ahmed El Mallah, Dr. Souraya Domiati