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Managing an epidemic.

Managing an epidemic

Last spring, the largest outbreak of salmonellosis in United States history struck the Midwest. The epidemic lasted five weeks, and nearly 100 hospitals and countless clinics and reference laboratories reported cases. None identified as many patients with salmonellosis as our microbiology laboratory did.

Workload increased tenfold at the height of the epidemic. To get results out, we had to streamline the standard Salmonella protocol.

During the first week of the epidemic, the source of the contamination was traced to a single Illinois dairy, which served a chain of grocery stores in a four-state area. However, it took several months of investigation by health authorities to determine that a faulty valve had apparently allowed raw milk to be mixed with pasteurized milk. Had the raw milk been fully processed, it would have been safe. Tests confirmed that the isolated organisms --Salmonella group B (ser. typhimurium)1--were not resistant to pasteurization.

This single instance of equipment malfunction had far-reaching consequences. A total of 15,525 culture-confirmed cases of salmonellosis were reported to the Illinois Department of Public Health, and another 1,000 victims were diagnosed in Indiana, Iowa, and Michigan. In addition, a handful of cases were identified in Wisconsin and Minnesota among residents who had traveled to the other four states.

Virtually every hospital and clinic in northern and central Illinois saw salmonellosis. In our 290-bed hospital, we identified 560 cases--about 3.5 per cent of the entire caseload. For several weeks during the outbreak, stool specimens were coming in at 10 times the normal rate. We rapidly modified microbiology procedures in a way that helped us keep pace and contain culture costs without sacrificing the quality of results.

The Salmonella outbreak actually occurred in two waves, probably due to intermittent contamination. The first rush, from March 24 to April 7, brought in more than 100 patients positive for group B Salmonella. The microbiology staff, 6.4 FTEs in all, tested 200 specimens during that period. Just when the extra workload began to subside, a larger influx of specimens hit. During the second wave--April 8 to April 28--the staff examined another 1,000 specimens and identified more than 400 cases of salmonellosis.

The epidemic forced us to address several key issues. With so many additional tests, for example, we were concerned about containing supply and labor costs. The greatly increased volume of specimens also made it necessary to suspend routine requests. There's always a clamor for news during a crisis, so we needed a quick way to provide accurate information to our physicians and the general public. Finally, how could we maintain staff morale in the midst of an unreasonable workload? A number of specific actions, based largely on suggestions from technologists, helped us cope.

Costs. As shown in Figure I, supply costs for processing stool cultures were relatively high at the beginning of the epidemic. We immediately took the following six steps to cut these costs and decrease the associated labor:

1. Eliminated Salmonella/Shigella agar. Although the standard approach of using two selective agars had worked well in the past, we found that it was not increasing isolation rates for this particular Salmonella species. This was the only change that became part of our routine after the epidemic ended.

2. Eliminated colistin nalidixic agar. This is used to identify gram-positive organisms when screening stools for pathogens. Since we had already established that the culprit in this case was gram-negative, there was no need to use this agar.

3. Discontinued complete biochemical identification for screen-positive organisms. The regular protocol involves an initial screen, biochemical confirmation, and then serotyping for absolute confirmation. Since virtually all of the positive screens were confirmed during the epidemic, we decided to skip the intermediate biochemical step. We went straight to serotyping whenever the rapid screen results suggested Salmonella.

4. Tested screen-positive isolates with Salmonella group B antisera only and eliminated polyvalent and other grouping antisera. The normal procedure calls for a screen, biochemical identification, and serologic testing with seven different groups of serotype. Since we had already identified the epidemic strain as group B, we could save the time and expense of running the other six serotypes.

5. Reserved Compylobacter blood agar for grossly bloody or liquid stools. Most of the stools were not characteristic of Campylobacter infection.

6. Only subcultured selenite F broth if cultures were not screen-positive at 24 hours. Sixty per cent of the selenite broths did not require subculture.

These six measures reduced the average supply cost for culture setup from $3.75 to $2.07; the cost of working up Salmonella isolates dropped from $7.66 to $2.56. The related large decrease in labor was even more important at the time.

Eliminating the Campylobacter agar was probably the single biggest cost saver. Cutting the serotyping back to one agent and bypassing the biochemical screen eased our workload the most.

On April 10, the number of stool specimens hit a record high of 120 in a single day. (Before the epidemic, we had seldom processed more than five per day.) As volume peaked, we had to take further steps to reduce supply costs and associated labor. It was becoming more and more expensive to stock up, and we didn't know how soon we would recover the cost from fees.

Outpatients accounted for 85 per cent of the epidemic workload. There was a chance that some might withhold payment pending legal action against the dairy. Indeed, many of the outpatients did not clinically require the test. That is, they had extremely low numbers of organisms and mild symptoms, and a physician would probably not have ordered Salmonella testing. However, they had drunk the milk, felt poorly, and wanted legal documentation of the infection.

We began the second streamlining effort by discontinuing antibiotic susceptibility testing for Salmonella group B isolates. This was feasible because all the previous isolates had exhibited the same pattern of resistance to ampicillin and susceptibility to chloramphenicol and trimethoprim-sulfamethoxazole. In another change, physicians had to specifically request culturing of stool specimens for pathogens other than Salmonella.

Inpatient, emergency department, and employee stool cultures were deemed more critical than outpatient work. They were set up using only MacConkey agar and selenite F broth. This enabled us to report results within 18 hours. Bypassing the more selective Hektoen agar gave us faster Salmonella growth and facilitated earlier screening of suspicious colonies.

The employee screening was available on request, based on an individual's symptoms or reported contact with the contaminated milk. No one in the laboratory contracted salmonellosis, and there were fewer than 20 cases among the entire hospital staff.

We used selenite F broth alone for outpatient specimens. No primary plates were inoculated. The selenite F broths were then subcultured to Hektoen after 24 hours of incubation.

Thanks to those stool culture modifications, we handled the surge in outpatient work without affecting the turnaround time required for inpatient work. Since the great majority of all stool cultures came from outpatients, dropping primary plates for this work yielded sizable supply cost savings. The stool culture cost now dropped to $1.45 for outpatients and $1.62 for inpatients (Figure I), while the Salmonella workup reagent cost fell to $2.02 (Figure II).

Overall, labor costs did not come down. Although the measures we took trimmed technical labor, that was outweighed by a tremendous increase in clerical work--such steps as calling positive results to physicians, obtaining patient addresses for submission with Salmonella isolates to the public health department, and reporting positive patients to the hospital's infection control team.

Outpatient cultures often came in from entire families, so we did save some time by batching the results to physicians in one call instead of phoning as each test was completed. But total weekly overtime for the microbiology lab rose to 20 hours during the worst of the epidemic, compared with a usual level of five hours per week.

Routine testing. When a patient has diarrhea, the standard practice is for physicians to order stool cultures and ova and parasite exams in a series of three daily specimens. If the symptomatic patient is a young child, they often request rotavirus antigen detection as well. These tests are very labor-intensive, and we don't see many positive O & Ps in our population. To perform the tests routinely during the epidemic, we would have had to double the microbiology staff, and patients would have been charged for essentially unnecessary lab work given the circumstances.

So even before physicians modified their ordering practices, we began holding O & P and rotavirus requests until Salmonella had been ruled out by culture. We told the physicians of this temporary measure, and as the epidemic progressed, some of them issued a standing order to cancel O & P and rotavirus testing when a stool culture was positive for Salmonella.

Every time a physician did ask for the extra tests, we questioned the need for them during our phone calls to report positive Salmonella results. Such test requests came primarily in the initial phase of the epidemic, and virtually all the physicians we contacted canceled the additional procedures. Since we could presumptively report positive Salmonella screens within 18 to 24 hours of specimen collection, we were able to eliminate a large amount of unneeded or duplicate lab work right at the start.

Communication. We kept the medical staff informed about procedural changes in a series of memoranda. To strengthen clinicians' cooperation, we also provided updates on our enormous daily workload.

We asked physicians not to call the laboratory except in an emergency. In exchange, the microbiology supervisor personally called their offices with positive results as soon as each day's screening tests were computed. When the workload began to drop, physicians were notified that the emergency procedures were no longer in force.

The public also needed accurate information during the epidemic. We routinely released statistics, granted interviews to the media, and distributed instructional handouts to all patients seen in the emergency department and outpatient laboratory. The flyers listed the symptoms of salmonellosis, emphasized the importance of washing one's hands, offered tips on food preparation, and explained how fecal-oral infections occur and spread from person-to-person contact.

Our National Medical Laboratory Week open house took place during the epidemic. It gave us an ideal opportunity to further educate the public. On April 17, the laboratory was decorated with posters showing our daily workload and the number of Salmonella organisms isolated. We also presented actual agar plate displays of the Salmonellae isolated from our patients, and on our door we hung a daily update of the total number of positive patients.

The hospital's communications department set up a 24-hour Salmonella hot line to answer questions from the public. Nonmedical staff members fielded more than 500 calls. They provided the information covered in our handouts and referred especially concerned callers to participating physicians for consultation.

Morale. With workload running at 10 times the normal level for up to three weeks, maintaining staff morale became as important as cost containment. We took several steps to keep our attitude positive. Many of the clerical tasks were delegated to the nontechnical staff. Computer-generated work lists and specimen labels also helped ease the clerical burden. And we called in part-timers and students to avoid having full-time technologists work an excessive amount of overtime.

A television crew came to the hospital, and three local newspapers profiled the laboratory's efforts. The media attention buoyed our staff's spirits. Another morale booster was the active involvement of technologists in all of our procedural streamlining. Employees had the satisfaction of seeing their ideas rapidly implemented.

The supervisor kept the staff up to date on the microbiology lab's standing in the race to identify the most Salmonella cases. Although the epidemic had very little impact on the other sections, the laboratory director had buttons made for all 85 staff members that read: "We 85 Survived' and "Stools Took Over Our Lab.'

When the workload finally began to diminish, the hospital administration hosted a luncheon buffet for employees. The laboratory director distributed a personal letter of appreciation to those staff members directly invoved in Salmonella testing.

Eight months have passed since the Salmonella epidemic struck, and the microbiology lab is back to business as usual. We learned a lot about managing a tremendous but relatively short-term increase in the workload. What's more, we had to learn fast, or risk refusing outpatient specimens at a time of great public anxiety. We're likely to learn even more if laboratorians are called in as expert witnesses when lawsuits reach trial.

We gained confidence that the laboratory could handle an even larger epidemic if such a disaster should ever occur. With luck, we'll never have to find out. As someone remarked while setting up one of the 1,300 stools, "Why couldn't it have been a strep throat epidemic?'

1. Centers for Disease Control. Morbidity and Mortality Weekly Report 15: 215, April 19, 1985.

Table: Figure I Stool culture media costs

Table: Figure II Reagent costs for Salmonella workup
COPYRIGHT 1985 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1985 Gale, Cengage Learning. All rights reserved.

Article Details
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Title Annotation:handling a salmonella outbreak
Author:DeBoer, Kathie P.; Gibbons, Austin J.
Publication:Medical Laboratory Observer
Date:Dec 1, 1985
Words:2168
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