RADIOLOGIC. Journal of the American Society of Radiologic Technologists Vol. 73, No. 6 July/August 2002

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1 REPRINT RADIOLOGIC Journal of the American Society of Radiologic Technologists Vol. 73, No. 6 July/August 2002 Radiation Safety in Fluoroscopy Organ Donation and Transplantation Bacterial Survival on Radiographic Cassettes Reprinted with permission of the American Society of Radiologic Technologists, Central Ave. SE, Albuquerque, NM and For more information please communications@asrt.org or visit

2 ... RADIOGRAPHY Bacterial Survival On Radiographic Cassettes SONYA R. LAWSON, M.S., R.T.(R)(T)(QM) RON SAUER, M.A., SM MARY B. LORITSCH, Ed.D., R.T.(R) The purpose of this investigation was to report the life span of Escherichia coli, Enterococcus faecalis and Staphylococcus aureus on 3 types of radio graphic imaging receptors currently used in diagnostic imaging departments in the United States. Kodak 400 speed, Dupont 400 speed and Fuji computed radiography cassettes were inoculated with the 3 bacteria, then placed in an incubation cabinet and cultured for a period of 2 weeks. All 3 cassettes revealed confluent growth with no noticeable reduction in bacterial numbers for the entire test period. This study verifies that common potentially pathogenic bacteria can survive for prolonged periods on radiographic imaging cassettes. Therefore, effective cleaning regimens are of fundamental importance in controlling and preventing potential nosocomial transmission in the diagnostic imaging department. Approximately 2 million nosocomial infections occur annually in the United States, resulting in considerable morbidity, mortality and cost. 1 Jarvis reported that excess length of hospitalization due to nosocomial infections is estimated to be 1 to 30 days, depending on the site of infection. In addition, the estimated mortality rate associated with these nosocomial infections ranges from 24% to 71%, with an estimated cost of approximately $500 to $ per patient. 1 Consequently, hospital infection control measures are critical for patients well-being and to reduce the costs associated with nosocomial infections. Infection control measures in the hospital environment are under new scrutiny due to the emergence of drug-resistant microorganisms. Important examples include methicillin-resistant Staphylococcus aureus (MRSA) and vancomycinresistant Enterococcus (VRE). MRSA has become a widespread nosocomial pathogen in the United States. 2 In hospitals, the most important reservoirs of MRSA are colonized patients, with hospital personnel usually identified as a link for transmission between patients. However, equipment and environmental surfaces may be contaminated with body fluids containing MRSA. Escherichia coli (E coli), Enterococcus faecalis (E faecalis) and Staphylococcus aureus (S aureus) have been recognized as nosocomial pathogens that cause outbreaks of disease in the hospital. Survival of these organisms on patient-contact surfaces and their persistence in the hospital environment are believed to be important factors in the spread of nosocomial infections. Numerous research studies have been published regarding nosocomial infection spread involving hospital intensive care units, patient rooms and health care worker transmission. However, published research investigating potential microbial spread in the diagnostic imaging department is limited. This prompted an investigation to determine whether E coli, E faecalis and S aureus can survive for prolonged periods on currently used radio graphic imaging receptors. Review of Literature E coli is among the most common causes of urinary tract infections and can infect many anatomical sites. 3 Some strains lead to kidney failure. Illnesses may be associated with food or water contaminated with human or animal feces, but in the hospital, person-to-person transmission and inanimate object contamination are common. Most E coli strains are normal members of the intestinal flora; however, pathogenic strains can remain in feces for many weeks after an illness resolves. Because this organism may reside in human fecal material, health care workers can help prevent transmission by following basic handwashing techniques as well as disinfecting patient-contact surfaces. E faecalis primary residence is the intestinal tract, where it is considered to RADIOLOGIC TECHNOLOGY 507

3 ... BACTERIA ON IMAGE RECEPTORS be a member of the normal intestinal flora. Thus, the direct or indirect reservoir for E faecalis infection is the digestive tract and transmission is similar to transmission of E coli. Direct or indirect contact with feces can lead to infections of any normally sterile site. Despite its inclusion in the normal human flora, E faecalis is among the most common causes of subacute bacterial endocarditis. Bloodstream infections always indicate severe, life-threatening disease processes. 4 S aureus resides on the skin of many healthy humans but retains the ability to take advantage of any disturbance in the host s environment. It can cause skin, wound and bloodstream infections if the epithelium is broken by injury or intravenous catheters. S aureus can infect nearly any anatomic site and is among the most common causes of hospital-acquired infections, particularly in patients more than 60 years old. 5 S aureus infections usually are associated with a high mortality. Published research investigating nosocomial infections in the diagnostic imaging department is limited. However, the results of studies involving patient-contact surfaces have demonstrated microbial contamination. In 1969 Myers 6 cultured chin rests and chest board surfaces, as well as the head and middle area of x-ray tables and found all of the surfaces to be contaminated with Staphylococcus and coloform colonies. An antiseptic germicidal towel containing alcohol and benzalkonium chloride was found to eradicate these organisms. In 1970 Haskin and colleagues 7 cultured the Franklin head unit, image intensifiers, chest boards, x-ray tables and portable x-ray cassettes. Staphylococcus, Streptococcus, fungi, Micrococcus, Klebsiella pneumoniae and diphtheroids were found on these surfaces. Of the 7 x-ray cassettes randomly chosen for testing, only one contained no microbial growth. Eight years later, LeFrock 8 published a study investigating the microbial cross-contamination potential during portable x-ray procedures. The chest boards and chin rests, x-ray tables, portable x-ray cassettes, Franklin head units, barium preparation area, wheelchairs and stretchers were colonized with K pneumoniae, E coli, micrococcus species, bacillus species, E faecalis, S epidermidis, Staphylococcus species and Streptococcus species. LeFrock tested the organisms sensitivity to various antibiotics. S epidermidis and bacillus species were resistant to most antibiotics. Interestingly enough, he found S aureus to be sensitive to vancomycin and methicillin. Today, S aureus may be resistant to both of these antibiotics. Twenty years after LeFrock s work, Ohara 9 evaluated whether ultrasound instruments were important in the spread of nosocomial staphylococcal infections. This study demonstrated that ultrasound procedures transfer S aureus from a patient s skin to the ultrasound transducer. In addition, they verified that S aureus survived in the transmission medium (gel). 9 In 2000 Neely and Maley 10 conducted a study to determine the survival of 22 gram-positive bacteria on 5 common hospital materials (clothing, towels, scrub suits, laboratory coats, privacy drapes and splash aprons). All isolates survived for a least 1 day, and some survived for more than 90 days on various materials. Wendt and colleagues 11 demonstrated that survival of Acinetobacter species in the environment is significantly associated with the strain and its source; strains recovered from dry sources or during outbreaks survived for longer periods. Published research has demonstrated the presence of potentially harmful microorganisms on patientcontact surfaces in the diagnostic imaging department, thus verifying the need for strict adherence to infection control policies and procedures. However, these studies are limited in number and most were conducted approximately 20 years ago. To determine the risk of disease transmission in the diagnostic imaging department, it is important to know what materials are potentially infectious. 12 Although diagnostic imaging and radiation oncology departments have not been of major concern in nosocomial infection spread, the potential for contagion exists, particularly with the emergence of antibiotic-resistant organisms. This research study provides further insight into the survival of 3 common pathogenic microorganisms on diagnostic imaging receptors. Methods E coli, E faecalis and S aureus were grown overnight in tryptic soy broth (TSB) at 37 C. Bacterial suspensions were prepared in fresh broth to approximate the density of a 0.5 McFarland turbidity standard (1.5 x 10 8 bacteria/ml). Three 14 x 17-inch diagnostic imaging cassettes were used in this study: Fuji computer radiography (Fujifilm Medical Systems USA Inc, Stamford, Conn), Kodak 400 speed (Eastman Kodak Co, Rochester, NY) and Dupont 400 speed (Dupont, Wilmington, Del). Each cassette was disinfected with 3% bleach and placed on a separate shelf in a clean incubation cabinet for 30 minutes. The bleach disinfectant was 508 VOLUME 73/NUMBER 6

4 ... LAWSON, SAUER, LORITSCH removed aseptically from each cassette, and each cassette was cultured to confirm the absence of bacteria by swabbing the cleaned surface with a sterile, broth-moistened cotton swab that was inoculated to both sheep blood agar and MacConkey agar plates. These culture plates were incubated at 37 C for 48 hours. All 3 cassettes were confirmed to be free of E coli, E faecalis and S aureus prior to testing. A cassette was divided into 3 sections; one each for the E coli, E faecalis, and S aureus. (See Fig. 1.) A 1-mL inocula of each of the 3 bacterial suspensions was spread evenly over the designated area and allowed to dry. This procedure was repeated for the remaining 2 cassettes. The cassettes were held in a dark incubation cabinet that had no airflow and minimal temperature or humidity changes during the test period. A 2-inch band across the bottom of each cassette was left uninoculated as a negative inoculum control. This area was sampled each time the cassette was tested for viability of the 3 different microbes. A sterile cotton swab moistened with sterile broth was swabbed back and forth across a 1-square-inch area of the cassette inoculated with E coli immediately after bacterial inoculation. The swab 2 weeks Hours Immediate Test/Control Area then was rolled across the surface of a fresh Mueller Hinton agar plate. This process was repeated for the areas inoculated with E faecalis and S aureus. Swab samples were taken from separate 1-inch test areas immediately after inoculation and at 1, 2, 6, 12, 24, 48 and 96 hours and at 2 weeks. This procedure was repeated for the remaining 2 cassettes. Results Each test area for each bacterium on each cassette revealed visible evidence of confluent growth when swabbed across the surface of a Meuller Hinton agar E coli E faecalis S aureus Microorganism Type Fig. 1. Schematic of organism placement on the radiographic cassettes. Each 14 x 17-inch cassette was oriented crosswise and blocked by the hour tested and type of microorganism. Table 1 Amount of Organisms Present at Each Time Interval Sampling Time E coli E faecalis S aureus Immediate Confluent Confluent Confluent 1 hour Confluent Confluent Confluent 2 hours Confluent Confluent Confluent 6 hours Confluent Confluent Confluent 12 hours Confluent Confluent Confluent 24 hours Confluent Confluent Confluent 48 hours Confluent Confluent Confluent 96 hours Confluent Confluent Confluent 2 weeks Confluent Confluent Confluent plate on the initial sampling and on each of the subsequent test samples at 1, 2, 6, 12, 24, 48 and 96 hours and even after 2 weeks in the incubation cabinet. Confluent growth means that there was so much of the bacterial growth on the agar plates that specific colony numbers could not be counted. There was no noticeable reduction in bacterial growth throughout the test period. (See Table 1.) All bacteria isolated at the end of the 2-week test period were confirmed by standard microbiological techniques to be the same bacteria that were inoculated initially. 13 The control area for each bacterium on each cassette revealed no evidence of bacterial growth when swabbed across the surface of a RADIOLOGIC TECHNOLOGY 509

5 ... BACTERIA ON IMAGE RECEPTORS Meuller Hinton agar plate on the initial sampling or on any of the subsequent test samples. (See Table 1.) Limitations This investigation was carried out in a microbiology laboratory and not an actual patient care area. The cassettes were stored in the horizontal position in a location with minimal airflow. Therefore, caution is recommended in generalizing this data to the clinical setting. Further research conducted in the clinical practice setting is recommended. Conclusion Radiographic imaging receptors occasionally become contaminated with harmful microorganisms during patient use and are potentially a source of nosocomial disease transmission. This investigation verifies that common potentially pathogenic bacteria can survive for prolonged periods on radiographic imaging receptors. These bacteria may be transmitted to patients, radiologic technologists or other health care personnel. Research has shown that effective cleaning regimens are fundamental in controlling and preventing potential nosocomial transmission in the health care environment. Future investigations that examine the effect of cleaning on microbial growth on radiographic imaging cassettes in the diagnostic imaging department are required. Furthermore, future studies are needed to determine whether other nosocomial isolates behave in a manner similar to these microorganisms, and to investigate the life span of microorganisms on other patient-contact surfaces specific to the diagnostic imaging department. In addition, further research should be conducted to determine risk factors for cross-transmission of nosocomial infections to evaluate what puts radiologic technologists at risk and methods to safeguard against it. References 1. Jarvis WR. Selected aspects of the socioeconomic impact of nosocomial infections: morbidity, mortality, cost, and prevention. Infect Control Hosp Epidemiol. 1996;17: Preventing emerging infectious diseases, a strategy for the 21st century. Available at: /ncidod/emergplan. Accessed January 10, Escherichia coli. Available at: /ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm. Accessed January 10, Stroud L, Edwards J, Danzig L, Culver D, Gaynes R. Risk factors associated with enterococcal bloodstream infections. Infect Control Hospital Epidemiol. 1996;17: Espersen F. Identifying the patient risk for Staphylococcus aureus bloodstream infections. J Chemother. 1995;7(Suppl 3): Myers PH. Contamination of patient-contact surfaces in radiology departments. JAMA. 1969;209: Haskin ME, Bondi A, Holmes RH, et al. The possible role of hospital radiology departments in cross infection and antibiotic-resistant bacterial mutagenesis. Surg Clin North Am. 1970;50: LeFrock JL, Babu JP, Klainer AS. Nosocomial infection: radiology department as source. NY State J Med. November 1978: Ohara T, Itoh Y, Itoh K. Ultrasound instruments as possible vectors of staphylococcal infection. J Hosp Infect. 1998;40: Neely AN, Maley MP. Survival of enterococci and staphylococci on hospital fabrics and plastics. J Clin Microbiol. 2000;38: Wendt C, Ditetze B, Dietz E, Ruden H. Survival of Acinetobacter baumannii on dry surfaces. J Clin Microbiol. 1997;35: Hansen ME. Bloodborne pathogens and procedure safety in interventional radiology. Seminars in Ultrasound, CT, and MRI. 1998;19: Mahon C, Manuselis G. Textbook of Diagnostic Microbiology. 2nd ed. Philadelphia, Pa: WB Saunders Co; Sonya R. Lawson, M.S., R.T.(R)(T)(QM), is an adjunct faculty member in the department of educational research in the Virginia Commonwealth University School of Medicine in Richmond, Va. Ms. Lawson is also a doctoral student in educational research and evaluation at Virginia Commonwealth University. Ronald Sauer, M.A., SM (AAM), is associate professor in the department of clinical laboratory sciences at Virginia Commonwealth University. Mary B. Loritsch, Ed.D., R.T.(R), is a professor in the radiography program at Virginia Western Community College in Roanoke, Va. The authors gratefully acknowledge Alisha Hodges, R.T.(R), for her assistance with data collection. Reprint requests may be sent to the American Society of Radiologic Technologists, Communications Department, Central Ave. SE, Albuquerque, NM by the American Society of Radiologic Technologists. 510 VOLUME 73/NUMBER 6

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