Impact of MRSA in X-ray departments

MRSA in the Deparment of Radiology

As the mean age of the general population increases, and as we stand on the threshold of the senility of the baby boomers, geriatric health care is becoming a more significant issue. Medical and nursing care for the elderly is at a premium and specialists in the field can name their own jobs as the work is both physically and emotionally demanding. The patients who require care in both hospital settings for are perhaps the most challenging. The multiple medical problems, the poly-pharmacy and increased incidence of methicillin resistant staff aureus infections in this population is a significant cause of nosocomial illness and can contribute to morbidity and mortality. There exists a small but definite risk of nosocomial infection transmission attributable to x-ray procedures.. This issue is most commonly seen in the use of direct patient contact with items such as ultrasound probes and transmission gels.

OBJECTIVE: The objective of this study is to determine if the rate of MRSA in the radiology department is statistically significant, and if so, what procedures are most likely to be linked to transmission.

MATERIALS AND METHOD: The rates of MRSA in a small suburban hospital for the months of January - March 2005 were studied and case files reviewed. Each patient who had had interaction with the radiology department was filtered out and reviewed for patterns. Swabs were taken from those items which seemed to have the most common association with patients who had MRSA, to include ultrasound probe heads and endoscopes used in ERCP. These swipes were cultures on a blood agar to determine the characteristics of the colony forming units (CFU).

RESULT: twelve bacterial isolates were recovered from ultrasound probes after typical cleaning procedures were used. Of these bacterial isolates which were recovered MRSA constituted 12.2%. There was no significant bacterial isolate found on the endoscopes used for endoscopic retrograde cholangiopancreatography (ERCP)

CONCLUSION: The risk of MRSA contamination in patients is higher in radiological procedures which use multiple use probes cleaned only with local measures rather than that of endoscopes which undergo a rigorous timed and chemical disinfection process..

Introduction

Methicillin resistant staff aureus or MRSA, as it is more widely known, has been an identified entity within health care and infectious disease circles since the 1960s. The prevalence of the condition, as well as it's discovery by the general public is not so much noted until some time in the 1980, although until the turn of the century it was previously only associated with significant risk factors, the most common being recent hospitalization or stay in a skilled nursing facility. The infection began to be seen more commonly outside of the hospital setting and on a community basis back around 2000. It also began to occur more commonly in children as well as in those who did not evidence significant risk factors for MRSA. Even so, a study from 2003 showed that'd. aureus was isolated from 21% (www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&term=%22Jernigan+JA%22%5BAuthor%5DJernigan JA, www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&term=%22Pullen+AL%22%5BAuthor%5DPullen AL, www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&term=%22Flowers+L%22%5BAuthor%5DFlowers L, www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&term=%22Bell+M%22%5BAuthor%5DBell M, www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&term=%22Jarvis+WR%22%5BAuthor%5DJarvis WR.) of the patients for whom cultures were performed. Methicillin-sensitive S. aureus was isolated from 18.4% of the patients, and MRSA was isolated from 2.7% of the patients. All 26 MRSA-colonized patients had been admitted to a healthcare facility in the preceding year, had at least one chronic illness, or both. In multivariate analyses comparing MRSA-colonized patients with control-patients, admission to a nursing home or a hospitalization of 5 days or longer during the preceding year were felt to be independent predictors of the likelihood of MRSA colonization. To date, there is no significant evidence that MRSA colonization occurs commonly among low-risk individuals, especially those in the community.

Statement of the Problem

Methicillin resistant Staphylococcus aureus is the full name for MRSA. It belongs to family staphylococcus aureus, a common cause of bacterial infections especially boils, carbuncles, wound infections, deep and superficial abscesses. Staph aureus is also the most common etiology for bacteremia. It was first identified as a common cause of post-surgical wound infection. When penicillin became available in the 1940s, it was found that most strains of S.aureus were sensitive to it, and this discovery significantly decreased post operative morbidity and mortality. Eminently adaptable, some strains of S. aureus were penicillinase producers, which meant they developed an enzyme which was able to break the beta lactam ring in the molecular structure of the penicillin. This deactivated the antibiotic, and protected the bacteria, in a sense making the bacteria stronger. This adaptation was so significant that by the 1960s, almost all strains of S.aureus were resistant to penicillin. The drug Methicillin was developed from penicillin to treat these resistant S.aureus infections. Methicillin avoided the beta lactam ring activity by counteracting the enzyme penicillinase responsible for the molecular change. This meant that previously resistant strains would now be treated with Methicillin. Within the first year of the introduction of methicillin, the first MRSA was reported. In essence, this meant that the S.aureus had adapted itself again so that the germ was now resistant to the very medication which had been developed to overcome resistance.

In the mid-1990s 'epidemic' strains of MRSA began to appear in hospitalized patients. This was more frequent initially in Europe and then passed to the United States. The epidemic strains were found to be very easily transmitted from patient to patient and easily colonized on patients and staff members. Far from a benign happenstance, the prevalence of S.aureus is now the most common cause of bacteremia in the developed world.

S.aureus is and S. epidermis are the most common staphylococci found on human skin. While S.epidermidis. is generally considered to be a harmless commensal bacteria, there are now strains which have also become Methicillin resistant, via the same mechanisms and S.aureus. S.epidermidis can cause significant morbidity as the cause of wounds infections, and especially if cultured off of medical devices like artificial hip joints or heart valves, or intravenous catheters. The most susceptible patients to Methicillin Resistant S. epidermis (MRSE) infections are those who are undergoing chemotherapy or other treatments which suppress the immune system, or those who are severely ill and hospitalized in intensive care units.

Staphylococcus aureus (including those that are MRSA) can cause anything from an asymptomatic carrier state, in which a patient has no illness but is simply colonized with the bacteria, to the previously mentioned bacteremia and septicemia. Patients who are colonized with S.aureus are still capable of passing these bacteria on to susceptible individuals while remaining healthy themselves.

A septicemia. It has been estimated that approximately 30% of the world's population are asymptomatically colonized with S.aureus. The incidents in hospital workers are higher, most likely because health care workers are more likely to come in contact with those who are infected. As previously noted, MRSA is most likely seen in hospital populations, but is now being found within the community. A recent study of wounds and abscesses of patients treated in an outpatient emergency department setting showed that, 12% were community-associated MRSA, and 75% of community associated MRSA isolates were from skin and soft tissue infections (Frazee, et.al. 2004). Even so, it is more likely to find S.aureus in hospital workers or in the hospital bound population. This is most likely because patients who are hospitalized are often on antibiotics, and resistant bacteria will be likely selected out due to the many infections treated within a hospital. The most likely sites of colonization for chronic S.aureus carriers are in the nose and the skin, especially folds such as axilla (armpit) or groin. A carrier can infect themselves, or they can pass it on to another. It is sometimes useful, in high risk situations, such as when a patient is immunocompromised or potentially immunompromised as in receiving chemotherapy, that pre-screening with skin or nasal culture is done. Should the patient be found to be a colonized patient, then it is likely they will have strict skin decontamination and intranasal topical antibiotic treatment before they undergo any procedure.

MRSA does not cause a solitary illness, like the bacteria which cause tuberculosis or syphilis. Instead, the bacterium S.aureus has a propensity for many different sites and types of tissue. S.aureus / MRSA is the most common cause of wound infection - either in wounds obtained accidentally or post operatively. It is commonly manifested as a red, inflamed wound with yellow exudates. Ulcers which are due to either superficial skin damage (such as decubitus ulcers) or poor blood supply (like stasis or diabetic ulcers) are Commonly found to be sites of infection with MRSA. Intravenous catheter lines, central or peripheral, are susceptible to infection with MRSA. This can be the nidus from which MRSA can enter the blood stream, causing bacteremia, septicemia and even death. Even after it is in the blood, MRSA can also lodge in organs like the lungs or kidneys and cause deep abscesses. These abscesses require a high index of suspicion since the patient may only present with a high fever and high white blood cell count on CBC, rigors and low blood pressure, heralding the onset of septicemic shock. This may eventually lead to end organ failure and death. MRSA / S.aureus are not often found to be the etiology of lung infection except in hospitalized patients who reside in the Intensive Care Units. Often the victim requires ventilation, meaning the bacteria can bypass the humoral and physical defenses of the nose and throat. Endotracheal intubation can also be a method of MRSA pneumonia, often fatal in the debilitated patient.

Hypothesis

Given the prevalence of MRSA within the hospital population, both patient and staff, and given the rate of MRSA infection within the general population, it is my hypothesis that it is more likely for patients to be contaminated with MRSA in radiological procedures which require the use of multi-patient equipment that goes through rudimentary cleaning, rather than radiographic procedures using multi-use equipment which goes through rigorous cleaning between each patient.

Literature Review

In essence, while a multitude of data and peer reviewed journal articles exist on MRSA, from colonization to hospital eradication programs, it was very difficult to find and studies in which the details were specific to the radiology department. Chief topics seem to currently surround the likelihood that MRSA is developing into a community rather than hospital based (or nosocomial) problem. Several articles cover the current debate. There are some studies which seem to indicate that MRSA is alive and well within the community while others seem to indicate that the transmission is solely seen within the health care setting. In 2003, Jernegan et. al. conducted a prevalence study of MRSA colonization among patients presenting to a university hospital by performing surveillance cultures at the time of hospital admission. Of the 974 patients cultured, 21% had S. aureus isolated, and 26 (2.7%) had MRSA, representing 12.7% of all patients colonized. The independent predictors of MRSA colonization in the study's population were admission to a nursing home in the previous year or a hospitalization of 5 days or longer during the preceding year.

Because of the confounding data in competing studies, it is difficult to know who is right. It is important to remember in the review of these articles that the studies are based upon cultures taken and reported positive in less than 48 hours from the time of admission. As is noted, patients can be in an asymptomatic chronic carrier state with MRSA for months of even years, which makes it doubly hard to presume the reliability of this data.

An interesting study by Manian, et. al looked at the feasibility of screening all patients on routine basis for MRSA. The clients in this study where patients with a history of intravenous drug use who were being admitted to acute rehabilitation beds. Interestingly, Manian reported a 12% isolation rate for MRSA on newly admitted patients, and only 7% on those patients for in house transfers. It is not reported within these studies whether the patients who required transfer from the rehabilitation setting to a medical bed were transferred due to illness possibly associated with MRSA infections. It is known that a history of MRSA infection or colonization were independently associated with the positive screening cultures. But this only represented about 40% of patients who were admitted with MRSA positive cultures, and may speak for the value of routine cultures on all admissions, especially if the cost/procedure benefit is high.

One of the greatest problems identified in the literature, especially that as noted by wound care specialists, is that of the gap between literature and actual practice. An article by Bodenheimer in the New England Journal of Medicine recently noted that even physicians and other medical practitioners who are educated on the hard evidence and willing to change, there is very little follow through in the matter of the identification of and prevention of MRSA. Steps to improving care surrounding MRSA were identified in this article and included:

involve relevant people develop a proposal study the main difficulties in achieving change select a set of strategies/measures develop a budget.

One interesting study reviewed the use of maggots in the treatment of MRSA. While not specifically germane to the subject at hand, it will show what a significant problem this health care issue has become. In this study, it was felt that it was important to discover alternatives to antibiotic resistant wounds in which no other form of treatment appeared to suffice. The goal of the study was to find a way to combat wounds and promote a healing. Ultimately it was felt that maggot therapy has been seen to act on MRSA in wounds and constitutes another area in need of study, with greater emphasis on evidence-based practice (Courtney, Church and Ryan, 2000).

It is interesting to note that the method found to be probably the most effective in decreasing the hand-to-hand transmission of MRSA is a cross between an item containing a 10% povidone-iodine solution and one that is primarily 70% ethyl alcohol. These results came from a small Brazilian study in which volunteers were tested using different cleaning agents after hands were minimally and then heavily contaminated with MRSA. It is interesting to note that the volunteers also used plain soap and a chlorhexadine solution. It should be noted however, that6 the study was relatively small, using only five volunteers and this significantly limits the data (Guilhermetti, 2001).

In Australia, a rigid screening and decolonization program has been helpful in decreasing the incidence of MRSA, although it continues to be a notable cause of hospitalization there. After an outbreak in a hospital in 1982 caused an epidemic, statutory notifications were enacted and several outbreaks were halted. It is interesting to note that there was a concurring incident of Ciprofloxacin resistance at the same time, but on the whole Australia has one of the lowest worldwide rates of multi-drug resistant MRSA thought to be in the most part due to their rigorous screening and surveillance programs. These programs have been so successful that there does not appear to be a significant presence of multi-drug resistant MRSA in any western Australian hospitals (McGuire, et al.).

Methodology

METHODS AND PROCEDURES: It is the hypothesis of this study that patients are more likely to become exposed to MRSA in the radiology department via multiuse items such as ultrasound probes using transdermal gel than with even more invasive radiological tools which undergo a more rigid and methodical cleaning program, such as the endoscopes used in the performance of endoscopic retrograde panreatoduodenoscopy.

The sample size estimates were based on the routine daily traffic throughout the radiology department in a small suburban hospital outside of a major metropolitan area. From a review of daily activity summaries, it was estimated that approximately 20 ultrasounds take place each day, while the rate or ERCP is one or less per week. To achieve a reasonable study population size, 100 study participants were needed. Patients will be identified via retrospective record review from data obtained from the local infection control committee, to whom all episodes of MRSA are reported for hospitalized and outpatient clients. A review of the patient history was done regarding medical history, current medication, lifestyle factors and family history. It was desirable for the patient population to be uniform in age (i.e. greater than 18 years and no greater than 70 years of age). We did not discern between inpatient and outpatients attending the radiology department, since the purpose of our study was not to determine whether the infection was nosocomial or community acquired, although it should be noted t hat the infection control committee of this institution did collect this data and would be willing to make it available to use for further study. For the purposes of HIPPA compliance, all personally identifying information was removed from the records before they were provided for the study staff, to include names, dates of birth, medical records number, social security number and other sensitive demographic information. The patients were simply identified by first and last initial and a two or three digit numeral, plus the modified "U" for those patients who had ultrasound and "E" for those who had had ERCP.

The study was retrospective in design. The study itself and took place over a 4-month period. Medical history checklists were developed by the study designer. Checklists were completed via chart review by a medical assistant hired specifically for the purpose. Medical history checklists were pre-tested on a group of individuals not enrolled in the study and evaluated for elements of clarity, reliability, sensitivity and interpretability. Study participants were not paid. Patients were screened for previous diagnosis of MRSA, either acute infection or as a carrier.

EVALUATION: Data collection was done by a review of all clinical material obtained. The presumed outcome (That multi-use radiological equipment which is cleaned using manual methods is more likely to be associated with transmission of MRSA than multi-use invasive equipment which is cleaned using rigid procedure and chemical disinfection) was compared to actual data collected. Possible confounding issues are previous unreported history of MRSA infection or colonization, patients who are not identified with infection during hospital stay or outpatient period of care.

Since the reporting of MRSA+ cultures is mandated by the state, it was unlikely that any patient identified with MRSA, either symptomatic or asymptomatic, would be missed.

ETHICAL CONSIDERATIONS: This research project was peer reviewed by the existing ethics element at the Health Maintenance organization. There appear to be no inherent harms to the participants involved, and the benefit of participation in the research study includes possibility of decreased morbidity and mortality from MRSA infection.

DISSEMINATION: Data from this research study will be provided to the clinicians at the health maintenance organization, to the radiology department, to the Ethics committee, the infection control committee and will be published if possible.

BUDGET:

Personnel:

Research Administrator (part time for 3 months) $1,000

No benefits for this position

MA for questionnaire review (80 hours @$12/hour) $720

Consultants: None

Supplies:

Computer (Laptop) $1,000

Office Supplies $250

Printing and Copying Services $150

Patient centered costs: None

Travel: None

Other expenses (discretionary for research administrator) $250

Total $3,370

HUMAN SUBJECTS: All subjects involved in this study will be over 18 years old and under 65 years old.

Patients will not receive a stipend or free medication for their participation. Patients must be English speaking and reside no greater than 50 miles from the hospital they attended.

Exclusion criteria:

Previous colonization or chronic carrier state - known.

Surgical procedures within the last twelve months

Selection: identification via infection control review

Must have undergone a radiological procedure during the hospital visit, either ultrasound or ERCP or both.

Results:

Twelve bacterial isolates were recovered from ultrasound probes after typical cleaning procedures were used (Probes are wiped twice with a bactericidal solution using a dry cloth with technologist wearing gloves). Of these bacterial isolates which were recovered MRSA constituted 12.2%. There was no significant bacterial isolate found on the endoscopes used for endoscopic retrograde cholangiopancreatography (ERCP) (The cleaning procedure for the endoscope consists of manual cleaning in which all channels, removable parts and all immerse able parts of the endoscope are cleaned. The outer surface is wiped with enzymatic soaked gauze and the scope in immersed in an enzymatic cleaner to prevent secretions from drying.) It is of interest to note that the three patients who underwent ERCP had also undergone ultrasound prior to the more invasive procedure and as yet, none have developed MRSA infection.

Conclusion:

It appears that the current method being used to clean the multi-use ultrasound probe heads in inadequate for the eradication of the risk of transmission of MRSA to patients within the radiology department. In addition, it would not appear that the invasive nature of the procedure is more likely to cause fomite colonization with MRSA, since the endoscopes used for the ERCP are far more invasive for the ultrasound probes, and go through a meticulous screening and cleaning procedure between each use. It would certainly be a source of infection should these probes not be cleaned correctly. The hypothesis proves to be true and the conclusion can be made that it is not the nature of the procedure that inherently increase the risk of MRSA but rather the care which is given to the radiological equipment between patients. It would also appear that there is not a significant degree of association with the patient's diagnosis and the ultimate colonization of the radiological equipment, since each patient who underwent an ERCP also underwent ultrasound, in each case within twenty four hours. In incidental review of the charts, there appeared to be no other significant radiological procedure which appeared to be associated with greater incidence of MRSA infection, either hospitalized patients or outpatients.

Discussion:

Because the prevalence of MRSA appears to vary widely, studies in a variety of healthcare settings would likely be helpful. One of the limitations of this study was that the hospital selected did a relatively small number of procedures which would fall under the heading of interventional radiology, and as such, would be of even more significant study as to the frequency of colonization in the radiology department related to rate of infection within the health care setting. The apparent emergence of community acquired MRSA as well as the relative reticence of most health insurers to hospitalize all but the sickest patients also makes it difficult for us to know who are truly nosocomially acquired and those who simply were undetected during their short hospital stay. Outcome studies to determine the association of in vitro resistance to clinical failure, as associated with potential source from hospital acquisition would also be useful. It is not entirely clear at the time of this writing that MRSA skin and soft tissue infections treated with drugs like cephalosporins are necessarily associated with poor outcome. Further study is going to be a worthwhile undertaking now that there appears to be a difference both genotypically and phenotypically between hospital and community associated MRSA - although it is early days yet. When these two isolates can be distinguished from each other, it is helpful since in most cases, community associated MRSA has a tendency to susceptibility to a broader range of antibiotics. More study needs to be done on the issue in which community associated MRSA strains often carry genes for what is known as Panton-Valentine leukocidin, a virulence factor that is associated with skin and soft tissue infections and necrotizing pneumonia.