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Enterobacter cloacae—contaminated cardioplegic solution
Discovery
and eradication
of a pharmacy
reservoir
George H. Talbot, M.D. Douglas E. Miller, Pharm.D. Ulrgaret Doorley, R.N. Mwy Provencher, MT. (ASCP) Maureen Skros, R.N. Raymond J. Coghlan, Pharm.D. WIlllam E. Judd, B.S., Pharm. Philadelphia,
Pennsylvania
Cardioplegic solution (CPS) is a dextroseelectrolyte mixture used during cardiac surgery to induce cardioplegia and to minimize the myocardial metabolic consequences of ischemia.’ CPS is usually prepared on site. Although guidelines for preparation of CPS have been published?, 3 production techniques have undoubtedly varied from institution to institution, with preparation being the responsibility of either the operating room team or the hospital pharmacy. On September 25, 1981, microbiologic quality control checks of CPS prepared in our pharmacy on September 21 revealed Enterobacter cloacae. The infection control practitioner immediately visited the pharmacy to review pertinent records and the methods of CPS preparation. The suspect lot was recalled, impounded, and submitted to the microbiology laboratory for further sterility testing. Since the lot numbers of CPS bags used during surgery were not recorded on the recipients’ charts, it was not possible to determine which patients received potentially contaminated CPS. However, during the 4-day interval be-
From the Infectious Diseases Section, Department of Medicine, University of Pennsylvania School of Medicine, and the Infection Control Section and Pharmacy and Drug Information Service, Hospital of the University of Pennsylvania, Philadelphia. Reprint requests: George H. Talbot, M.D., infectious Diseases Section 536 Johnson Pavilion/G2, 36th St. and Hamilton Walk, Philadelphia, PA 19104.
tween preparation of the implicated lot, its release from the pharmacy, and discovery of its contamination, 4 of 14 patients undergoing cardiac surgery developed otherwise unexplained intraoperative and/or immediate postoperative hypotension. These four had surgery on either September 22 or 23. All were ultimately discharged from the hospital without sequelae attributable to contaminated CPS. We now report the identification and eradication of the pharmacy reservoir of E. cloacae responsible for this episode of bacterial contamination of CPS. MATERIAL
AND METHODS
CPS production and quality control. Prior to recognition of contamination, CPS was prepared as follows: commercially manufactured sterile ingredients (sodium bicarbonate, calcium chloride, sodium chloride, potassium chloride, mannitol, dextrose, and sterile water for injection) were mixed for 1 hour with a magnetic stirrer in a 10 L flask. Mixing was performed inside a laminar airflow hood. The resulting solution was decanted into a 20 L pressure cannister (Fig. 1). (Two pressure cannisters were available, but only one was in constant use during the September episodes of contamination.) The CPS-containing pressure cannister was then connected to a nitrogen pressure tank via an inlet elbow and to a filtration apparatus via an outlet elbow. This latter part of the system consisted of, in sequence, a segment of sterile 239
,Atnerican
240
Talbot et al.
INFECTION
1. Cardioplegic
solution
production
system.
surgical connecting tubing, a Twin-90 0.22 pm filter, another segment of surgical tubing, and then a transfer set that fed into a 1 L Viaflex plastic bag. A Viavac vacuum pump apparatus was employed to assist filling. Manipulation of the filter, the Viaflex bag, and their connections was performed only inside a laminar airflow hood. Nitrogen pressure was monitored by a two-stage pressure regulator. Pressure was maintained at no more than 12 to 15 psi so as not to exceed the 15 psi limit of the Twin-90 filter. The vacuum pump pressure was monitored in inches of mercury; it was usually operated at 20 to 25 in. Hg (10 to 12 psi). The only part of the production system that was neither sterilized on site nor commercially sterilized and prepackaged was the pressure cannister. After each use, the pressure cannister was rinsed with distilled water and stored open to the air in the work area. In preparation for CPS production, the pressure cannister was rinsed with sterile water. It was not dismantled for cleaning on any routine basis. Approximately two 20 L lots of CPS were prepared weekly. Although filtration was performed to produce sterility, 10% of each lot was routinely submitted to microbiology for microbiologic quality control testing, as described later. Pharmacy standard operating procedure required that CPS be held in quarantine for 5 days pending results of bacterial cultures. However, it could be released for use prior to the 30-day period needed for final fungal culture results. If bacterial cultures of initial specimens were positive, the lot was to remain in
ol
quarantine and additional cultures were to be If these failed to con&-m the original findings, the lot was released for use. Once CPS was released from quarantine, it was sent to the operating rooms as needed. Because of heavy demand, virtually no solution ever reached the 6-month expiration date. Operating room procedure did not include recording the lot number of CPS received by an individual patient. In addition to CPS, four other large-volume solutions were prepared with the use of the nitrogen pressure cannister and Twin-90 filtration system: tissue culture medium, infant intravenous hyperalimentation solution (IVH), Renacidin, and kidney preservation solution. Only CPS and tissue culture medium were filtered with vacuum pump assistance. The other three solutions were filtered under positive pressure into glass bottles, which precluded use of the vacuum pump. Microbiologic methods. Routine microbiologic quality control testing was performed on 10% of the bags in each lot of pharmacy-prepared, large-volume fluid, including CPS (e.g., on two 1 L bags from every 20 L lot of CPS). From each bag or bottle, 10 ml was withdrawn aseptically. Five milliliters was injected into 50 ml of thioglycollate broth and 5 ml into 50 ml of Sabouraud’s glucose broth. During the investigation, 6 ml of fluid was withdrawn from each bag of CPS suspected of being contaminated. Five milliliters was inoculated into 50 ml of thioglycollate broth and the remaining 1 ml was plated on blood agar and MacConkey plates. A calibrated loop was not employed for plating. Environmental cultures were collected by using either a syringe and needle or a swab, as appropriate, and were processed in a similar fashion except for the use of 10 ml instead of 50 ml of thioglycollate broth. Brain-heart infusion broth was used for all broth rinses. Organisms were identified by the API-20E Autobac system and susceptibility testing performed on the Autobac multitest system. Engineering analysis. Evaluation of pressures within the production apparatus was performed by members of the hospital’s Clinical Engineering Department. The range of pressures generated by the vacuum pump and the sent.
Fig.
Jomal CONTROL
Volume
12 Number
August,
1984
4
Contaminated
Table 1. Environmental culture results* specimem type
She Distilled water dispenser tubing Distilled water in tubing Sink drain 10 L flask Magnetic stirrer In-use pressure cannister Standing water Inner surface Inner surface Inlet elbow Pressure gauge Pressure-relief valve Outlet elbow Reserve pressure cannister Vacuum pump Oil wick Suction nozzle Exhaust muffler ‘Sampling 1981
was performed
CUlttIre result
241
Pressures
No growth
Aspirate Swab Wash Swab
No No No No
Aspirate Swab Wash Swab Swab Swab Swab Wash
E. cloacae E. cloacae E. cloacae No growth No growth No growth E. cloacae (Bacillus
Swab Swab Swab
(Mold) No growth (Mold)
Site
growth growth growth growth
27, 1981, and September
solution
Table 2. Engineering analysis of pressures generated by CPS production system
Swab
on September
cardioplegic
Vacuum
pump
Indicated* -5 -10
-15 -25 Nitrogen tank
pressure
in. Hg in. Hg
in. Hg in. Hg$ 10 psi 20 psi
Measuredt -4.4 -8.0 - 11.5 - 18.0
in. Hg
(-2.2
in. Hg (-3.9 in. Hg (-5.6 in. Hg# (-9.0 8.0 psi 17.6 psi
psi)
psi) psi) psi)*
‘Indicated by gauge in place in system. tMeasured by Timeter RT-100. $6~ extrapolation-setting not actually tested.
sp)
28,
nitrogen pressure tank was measured with a Timeter RT- 100 calibrated meter. Maximum pressure across the Twin-90 filter was calculated by subtracting the contributions of the vacuum pump and the nitrogen pressure tank. Actual pressures may be somewhat less because of presumed pressure drops within the system. Statistical analysis. The Fisher exact test was applied to dichotomous variables. RESULTS
Microbiologic quality control testing of two bags of CPS from a 20 L lot prepared on September 2 1, 1981, revealed E. cloacae (API Autobac profile No. 3305573). The organism was resistant to ampicillin and cephalothin but sensitive to amikacin, carbenicillin, chloramphenicol, gentamicin, tetracycline, and trimethoprim-sulfamethoxazole. In violation of standard operating procedure, nine bags of this lot had been dispensed to the operating room prior to receipt of microbiologic quality control testing results. Each of the nine bags remaining in the pharmacy was sampled; although invariably clear to visual inspection, each grew E. cZoacae. The API profile number of these or-
ganisms was either 3305573 or 3305553, depending on the bag examined. Susceptibility testing revealed antibiograms identical to that of the first isolate. Quantitative results were not available. In addition, two of four specimens from a lot prepared on September 16, 1981, grew the same organism. Six specimens from the three other lots prepared between September 15 and 22 were culture negative. Results of environmental culturing are summarized in Table 1. Specimens were obtained from a number of sites, including the pharmacy’s distilled water dispensing apparatus, the work area sink, and the reserve pressure cannister. E. cloucae was not recovered from these cultures nor from those of the 10 L mixing flask, the magnetic stirrer, the pressure cannister gauge, the nitrogen gas inlet elbow of the pressure cannister, or the vacuum pump oil wick and suction nozzle. However, E. cZoucue (API Autobac profile No. 3305573), which was resistant only to ampicillin and cephalothin, was recovered from multiple sites within the in-use pressure cannister, including from 20 to 30 ml of distilled water remaining after the last cleaning 4 days previously and from a large amount of particulate material that had accumulated in the outlet elbow. Table 2 summarizes the results of the engineering analysis. Measured pressures generated by the vacuum pump and the nitrogen pressure tank were lower than indicated pressures in all instances. If linear relationships are assumed, then with pressures set at 20 to 25 in. Hg and 10 to 12 psi, respectively, the maximum
American
242
Talbot et al.
Tabh~ quality
3. Correlation of equipment used in production of large-volume control results. (May 11, 1981, to September 24, 1981)
INFECTION
Production Preeeure cennleter
solution
Cardioplegic solution Tissue culture medium Infant IV hyperalimentation solution Renacidin Kidney preservation solution Xardioplegic
solution
and tissue
culture
medium
Miorobiolagk controt Vacuum pump’
+ + + + + were
prepared
with vacuum
pressure across the Twin-90 filter can be estimated to be approximately 15 to 19 psi, a range in excess of the filter’s 15 psi tolerance. A review of microbiologic quality control testing records from June 1980 through September 1981 revealed 26 instances in which pharmacy-prepared solutions were culture positive. Organisms recovered included StuphyZococcus epidermidis, diphtheroids, and species of Penicillium, Bacillus, Propionibacterium, Cladosporium, and Aspergillus. E. cloacae was isolated first on May 11, 198 1, from kidney preservation solution. Preparation of kidney preservation solution involved filtration under nitrogen pressure, but vacuum pump-assisted filling was not possible because this solution was packaged in glass bottles. Table 3 correlates production techniques of the five products prepared in the pressure cannister from May 11, 198 1, to September 24, 198 1, with results of microbiologic quality control tests. Of 91 specimens submitted from solutions prepared with the use of vacuum pump-assisted filling, five (5.5%) revealed E. cloucae. Of 60 specimens submitted from products for which the vacuum pump was not employed, one (1.7%) revealed E. cloucae (p = 0.403, two-tailed Fisher’s exact test). Thus there was no difference between the frequency of E. cloacae contamination of solutions prepared with vacuum pump assistance and the frequency of E. cloacae contamination of solutions prepared without vacuum pump-assisted filling. During the investigation, a member of the pharmacy CPS production team (W.E.J.) noted
+ + pump-assisted
of
with microbiologic
equipment Twin-90 filter
+ + + + +
solutions
Journal CONTROL
Samples submftted
qwlhy tests Samplee poeitive for E. chxtcee
79 12
5 0
44
0
10
0
6
1
ftlling, the remaining
three
solutions
ware
not
that some of the Twin-90 filters were cracked. The manufacturer was notified. Subsequently, a nationwide and international recall of Twin90 filters was initiated by the manufacturer.4
Although extrinsic contamination of CPS has recently been implicated in E. cloacae bacteremia and mediastinitis,j intrinsic CPS contamination has not previously been reported as far as we are aware. In other instances, intrinsic microbial contamination of pharmaceutical products has caused significant patient morbidity and mortality on both a nationwide6 and a loca17mg level. These problems often have been uncovered only after recognition and investigation of an epidemic. At our hospital, a microbiologically proven epidemic was not documented. Initial review of CPS production techniques immediately centered attention on the pressure cannister as a possible reservoir for E. cloucae. Environmental culturing confirmed this suspicion: E. cloacue of the same API profile number and antibiogram as that in the CPS was recovered from the pressure cannister. Cultures negative for this organism from other sites in the work area and in the CPS production system substantiated the hypothesized role of the pressure cannister. How the pressure cannister itself originally became contaminated is uncertain . Pharmacy personnel have been implicated in one other reported episode of product contamination.‘O Hand or nasal cultures were not performed to test this hypothesis. Since the pressure cannister indeed repre-
Volume
12 Number
August,
1984
4
sented the likely reservoir for E. cloacae, it was necessary to explain how organisms contaminated the final CPS, since all solution passed through a 0.22 pm filter capable of removing bacteria. Engineering analysis initially suggested that the simultaneous use of the nitrogen pressure tank and the vacuum pump could generate pressures in excess of the 15 psi filter specification, which in turn could allow transfilter passage of bacteria with consequent CPS contamination. However, this hypothesis was not tenable since kidney preservation solution, which was prepared without use of the vacuum pump apparatus, was also contaminated with E. cbacae in one instance. The observation of occasional defective Twin-90 filters provided the likely explanation. Malfunction of the filters was in all likelihood the single event needed for contamination to occur, since the rates of E. cloacae contamination did not differ as a function of the presence (5.5% contamination rate) or absence (1.7% contamination rate) of vacuum pump assistance. It remains possible that excessive transfilter pressure could contribute to filter malfunction, but our findings do not support this hypothesis. Other data suggest that intact Twin-90 filters are capable of withstanding transmembrane pressures significantly in excess of 15 psi.” As a result of these findings, control measures were instituted. The pressure cannister is now sterilized before each use. In addition, it is disassembled every 2 weeks and thoroughly cleaned of any accumulated debris. To ensure that excessive transfilter pressure is not generated, the vacuum pump is no longer used to assist filling. Before use, filters are examined for gross defects. An integrity test is now performed on each unit after use. Quarantine of CPS awaiting microbiological clearance is strictly enforced. l2 When CPS is released, a precise record is maintained of the patients receiving it. Finally, a more extensive communication network linking the pharmacy, the microbiology laboratory, and the Infection Control Section has been established.12s l3 Following these changes, there has been no instance of E. cbacae contamination of any pharmacyprepared fluid.
Contaminated
cardioplegic
solution
243
SUMMARY
Our conclusions and recommendations are as follows: 1. Pressurized cannisters used in the production of large-volume parenteral fluids may serve as a reservoir of bacterial contamination unless they are routinely disassembled, cleaned, and sterilized. 2. Filtration cannot be assumed to ensure sterility, since filters may be defective. Microbiologic quality control measures are essential. 3. Quality control procedures must be part of an established surveillance system for reporting of problems with large-volume solutions. Ideally, representatives of the pharmacy, the microbiology laboratory, and infection control should be involved. 4. Quarantine of products awaiting microbiological clearance should be strictly enforced. 5. Microbiologic quality control tests that reveal gram-negative rods must be viewed with concern and investigated appropriately. 6. Record keeping should allow precise, rapid identification of the specific patients receiving a pharmacy-prepared product. 7. The use of both positive and negative pressure to increase filtration rate conceiveably may produce a total pressure exceeding that recommended for the filter used. Therefore users of such filtration systems should periodically recalibrate pressure-monitoring gauges to ensure that excess pressure is not generated. We express our appreciation to the Microbiology Laboratory for their enthusiastic assistance in this investigation. Michael Soltys, Joseph Evans, and Frank Sharer kindly performed the engineering analysis. Dr. Ed Lusk provided statistical advice. We also thank Dr. Henry Edmunds and all other members of the Cardiothoracic Surgery Section for their cooperation and support. Ms. Mickey Campanile and Mrs. Hazel Price provided excellent secretarial assistance, and Ms. Cindy Friedman prepared the figure.
References 1. Kirklin JW, Conti VR, Blackstone EH: Prevention of myocardial damage during cardiac operations. N Engl J Med 301: 135 141, 1979. 2. Swerling R: The use and preparation of cardioplegic solutions in cardiac surgery. Hosp Pharm 15:497-503, 1980. 3. Armistead S, Collins GE, Bowman JD, et al: Prepara-
Arwcan
244
4. 5.
6.
7.
8.
Talbot
et al.
tion of cardioplegic solutions. Am J Hosp Pharm 36:1361-1365, 1979. Food and Drug Administration: FDA enforcement report. Rockville, Md, March 9, 1983. Kalaidjian R, Tager IB: Bacteremia among aorticvalve surgery patients-Boston. Morbid Mortal Weekly Rep 31:88-89, 1982. Maki DG, Rhame FS, Mackel DC, Bennet JV: Nationwide epidemic of septicemia caused by contaminated intravenous products, I. Epidemiologic and clinical features. Am J Med 60~47 l-485, 1976. Sarubbi FA, Wilson B, Lee M, Brokopp C: Nosocomial meningitis and bacteremia due to contaminated amphotericin B. JAMA 239~416-418, 1978. Plouffe JF, Brown DG, Silva J, et al: Nosocomial outbreak of Candida parapsilosis fungemia related to intravenous infusions. Arch Intern Med 137: 1686- 1689, 1977.
INFECTION
Journal
of
CONTROL
9. Phillips I, Eykyn S, Laker M: Outbreak of hospital infection caused by contaminated autoclaved fluids. Lancet 1: 1258- 1260, 1972. 10. Davis AT, Nadler HL, Brown MC, et al: Primary bacteremia. Morbid Mortal Weekly Rep 29: 110-l 11, 1976. 11. Leahy TJ, Sullivan MJ: Validation of bacterialretention capabilities of membrane filters. Pharm Tech 2:65-75, 1978. 12. National Coordinating Committee on Large Volume Parenterals: Recommended guidelines for quality assurance in hospital centralized intravenous admixture services. Am J Hosp Pharm 37:645-655, 1980. 13. National Coordinating Committee on Large Volume Parenterals: Recommended system for surveillance and reporting of problems with large-volume parenterals in hospitals. Am J Hosp Pharm 32: 125 l- 1253, 1975.
I Bound volumes avahble to sulmxibers Bound volumes of AMERICAN JOURNAL OF INFECTION CONTROL are available to subscribers (only) for the 1984 issues from the Publisher, at a cost of $23.00 ($28.50 international) for Vol. 12 (January-December). Shipping charges are included. Each bound volume contains a subject and author index and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact The C. V. Mosby Company, Circulation Department, 11830 Westline Industrial Drive, St. Louis, Missouri 63146 USA; phone (800)325-4177, ext. 351. Subscriptions must be in force to qualify. Bound volumes are not ava%labte in plam of a regular journal subscription.
and eradication
of a pharmacy
reservoir
George H. Talbot, M.D. Douglas E. Miller, Pharm.D. Ulrgaret Doorley, R.N. Mwy Provencher, MT. (ASCP) Maureen Skros, R.N. Raymond J. Coghlan, Pharm.D. WIlllam E. Judd, B.S., Pharm. Philadelphia,
Pennsylvania
Cardioplegic solution (CPS) is a dextroseelectrolyte mixture used during cardiac surgery to induce cardioplegia and to minimize the myocardial metabolic consequences of ischemia.’ CPS is usually prepared on site. Although guidelines for preparation of CPS have been published?, 3 production techniques have undoubtedly varied from institution to institution, with preparation being the responsibility of either the operating room team or the hospital pharmacy. On September 25, 1981, microbiologic quality control checks of CPS prepared in our pharmacy on September 21 revealed Enterobacter cloacae. The infection control practitioner immediately visited the pharmacy to review pertinent records and the methods of CPS preparation. The suspect lot was recalled, impounded, and submitted to the microbiology laboratory for further sterility testing. Since the lot numbers of CPS bags used during surgery were not recorded on the recipients’ charts, it was not possible to determine which patients received potentially contaminated CPS. However, during the 4-day interval be-
From the Infectious Diseases Section, Department of Medicine, University of Pennsylvania School of Medicine, and the Infection Control Section and Pharmacy and Drug Information Service, Hospital of the University of Pennsylvania, Philadelphia. Reprint requests: George H. Talbot, M.D., infectious Diseases Section 536 Johnson Pavilion/G2, 36th St. and Hamilton Walk, Philadelphia, PA 19104.
tween preparation of the implicated lot, its release from the pharmacy, and discovery of its contamination, 4 of 14 patients undergoing cardiac surgery developed otherwise unexplained intraoperative and/or immediate postoperative hypotension. These four had surgery on either September 22 or 23. All were ultimately discharged from the hospital without sequelae attributable to contaminated CPS. We now report the identification and eradication of the pharmacy reservoir of E. cloacae responsible for this episode of bacterial contamination of CPS. MATERIAL
AND METHODS
CPS production and quality control. Prior to recognition of contamination, CPS was prepared as follows: commercially manufactured sterile ingredients (sodium bicarbonate, calcium chloride, sodium chloride, potassium chloride, mannitol, dextrose, and sterile water for injection) were mixed for 1 hour with a magnetic stirrer in a 10 L flask. Mixing was performed inside a laminar airflow hood. The resulting solution was decanted into a 20 L pressure cannister (Fig. 1). (Two pressure cannisters were available, but only one was in constant use during the September episodes of contamination.) The CPS-containing pressure cannister was then connected to a nitrogen pressure tank via an inlet elbow and to a filtration apparatus via an outlet elbow. This latter part of the system consisted of, in sequence, a segment of sterile 239
,Atnerican
240
Talbot et al.
INFECTION
1. Cardioplegic
solution
production
system.
surgical connecting tubing, a Twin-90 0.22 pm filter, another segment of surgical tubing, and then a transfer set that fed into a 1 L Viaflex plastic bag. A Viavac vacuum pump apparatus was employed to assist filling. Manipulation of the filter, the Viaflex bag, and their connections was performed only inside a laminar airflow hood. Nitrogen pressure was monitored by a two-stage pressure regulator. Pressure was maintained at no more than 12 to 15 psi so as not to exceed the 15 psi limit of the Twin-90 filter. The vacuum pump pressure was monitored in inches of mercury; it was usually operated at 20 to 25 in. Hg (10 to 12 psi). The only part of the production system that was neither sterilized on site nor commercially sterilized and prepackaged was the pressure cannister. After each use, the pressure cannister was rinsed with distilled water and stored open to the air in the work area. In preparation for CPS production, the pressure cannister was rinsed with sterile water. It was not dismantled for cleaning on any routine basis. Approximately two 20 L lots of CPS were prepared weekly. Although filtration was performed to produce sterility, 10% of each lot was routinely submitted to microbiology for microbiologic quality control testing, as described later. Pharmacy standard operating procedure required that CPS be held in quarantine for 5 days pending results of bacterial cultures. However, it could be released for use prior to the 30-day period needed for final fungal culture results. If bacterial cultures of initial specimens were positive, the lot was to remain in
ol
quarantine and additional cultures were to be If these failed to con&-m the original findings, the lot was released for use. Once CPS was released from quarantine, it was sent to the operating rooms as needed. Because of heavy demand, virtually no solution ever reached the 6-month expiration date. Operating room procedure did not include recording the lot number of CPS received by an individual patient. In addition to CPS, four other large-volume solutions were prepared with the use of the nitrogen pressure cannister and Twin-90 filtration system: tissue culture medium, infant intravenous hyperalimentation solution (IVH), Renacidin, and kidney preservation solution. Only CPS and tissue culture medium were filtered with vacuum pump assistance. The other three solutions were filtered under positive pressure into glass bottles, which precluded use of the vacuum pump. Microbiologic methods. Routine microbiologic quality control testing was performed on 10% of the bags in each lot of pharmacy-prepared, large-volume fluid, including CPS (e.g., on two 1 L bags from every 20 L lot of CPS). From each bag or bottle, 10 ml was withdrawn aseptically. Five milliliters was injected into 50 ml of thioglycollate broth and 5 ml into 50 ml of Sabouraud’s glucose broth. During the investigation, 6 ml of fluid was withdrawn from each bag of CPS suspected of being contaminated. Five milliliters was inoculated into 50 ml of thioglycollate broth and the remaining 1 ml was plated on blood agar and MacConkey plates. A calibrated loop was not employed for plating. Environmental cultures were collected by using either a syringe and needle or a swab, as appropriate, and were processed in a similar fashion except for the use of 10 ml instead of 50 ml of thioglycollate broth. Brain-heart infusion broth was used for all broth rinses. Organisms were identified by the API-20E Autobac system and susceptibility testing performed on the Autobac multitest system. Engineering analysis. Evaluation of pressures within the production apparatus was performed by members of the hospital’s Clinical Engineering Department. The range of pressures generated by the vacuum pump and the sent.
Fig.
Jomal CONTROL
Volume
12 Number
August,
1984
4
Contaminated
Table 1. Environmental culture results* specimem type
She Distilled water dispenser tubing Distilled water in tubing Sink drain 10 L flask Magnetic stirrer In-use pressure cannister Standing water Inner surface Inner surface Inlet elbow Pressure gauge Pressure-relief valve Outlet elbow Reserve pressure cannister Vacuum pump Oil wick Suction nozzle Exhaust muffler ‘Sampling 1981
was performed
CUlttIre result
241
Pressures
No growth
Aspirate Swab Wash Swab
No No No No
Aspirate Swab Wash Swab Swab Swab Swab Wash
E. cloacae E. cloacae E. cloacae No growth No growth No growth E. cloacae (Bacillus
Swab Swab Swab
(Mold) No growth (Mold)
Site
growth growth growth growth
27, 1981, and September
solution
Table 2. Engineering analysis of pressures generated by CPS production system
Swab
on September
cardioplegic
Vacuum
pump
Indicated* -5 -10
-15 -25 Nitrogen tank
pressure
in. Hg in. Hg
in. Hg in. Hg$ 10 psi 20 psi
Measuredt -4.4 -8.0 - 11.5 - 18.0
in. Hg
(-2.2
in. Hg (-3.9 in. Hg (-5.6 in. Hg# (-9.0 8.0 psi 17.6 psi
psi)
psi) psi) psi)*
‘Indicated by gauge in place in system. tMeasured by Timeter RT-100. $6~ extrapolation-setting not actually tested.
sp)
28,
nitrogen pressure tank was measured with a Timeter RT- 100 calibrated meter. Maximum pressure across the Twin-90 filter was calculated by subtracting the contributions of the vacuum pump and the nitrogen pressure tank. Actual pressures may be somewhat less because of presumed pressure drops within the system. Statistical analysis. The Fisher exact test was applied to dichotomous variables. RESULTS
Microbiologic quality control testing of two bags of CPS from a 20 L lot prepared on September 2 1, 1981, revealed E. cloacae (API Autobac profile No. 3305573). The organism was resistant to ampicillin and cephalothin but sensitive to amikacin, carbenicillin, chloramphenicol, gentamicin, tetracycline, and trimethoprim-sulfamethoxazole. In violation of standard operating procedure, nine bags of this lot had been dispensed to the operating room prior to receipt of microbiologic quality control testing results. Each of the nine bags remaining in the pharmacy was sampled; although invariably clear to visual inspection, each grew E. cZoacae. The API profile number of these or-
ganisms was either 3305573 or 3305553, depending on the bag examined. Susceptibility testing revealed antibiograms identical to that of the first isolate. Quantitative results were not available. In addition, two of four specimens from a lot prepared on September 16, 1981, grew the same organism. Six specimens from the three other lots prepared between September 15 and 22 were culture negative. Results of environmental culturing are summarized in Table 1. Specimens were obtained from a number of sites, including the pharmacy’s distilled water dispensing apparatus, the work area sink, and the reserve pressure cannister. E. cloucae was not recovered from these cultures nor from those of the 10 L mixing flask, the magnetic stirrer, the pressure cannister gauge, the nitrogen gas inlet elbow of the pressure cannister, or the vacuum pump oil wick and suction nozzle. However, E. cZoucue (API Autobac profile No. 3305573), which was resistant only to ampicillin and cephalothin, was recovered from multiple sites within the in-use pressure cannister, including from 20 to 30 ml of distilled water remaining after the last cleaning 4 days previously and from a large amount of particulate material that had accumulated in the outlet elbow. Table 2 summarizes the results of the engineering analysis. Measured pressures generated by the vacuum pump and the nitrogen pressure tank were lower than indicated pressures in all instances. If linear relationships are assumed, then with pressures set at 20 to 25 in. Hg and 10 to 12 psi, respectively, the maximum
American
242
Talbot et al.
Tabh~ quality
3. Correlation of equipment used in production of large-volume control results. (May 11, 1981, to September 24, 1981)
INFECTION
Production Preeeure cennleter
solution
Cardioplegic solution Tissue culture medium Infant IV hyperalimentation solution Renacidin Kidney preservation solution Xardioplegic
solution
and tissue
culture
medium
Miorobiolagk controt Vacuum pump’
+ + + + + were
prepared
with vacuum
pressure across the Twin-90 filter can be estimated to be approximately 15 to 19 psi, a range in excess of the filter’s 15 psi tolerance. A review of microbiologic quality control testing records from June 1980 through September 1981 revealed 26 instances in which pharmacy-prepared solutions were culture positive. Organisms recovered included StuphyZococcus epidermidis, diphtheroids, and species of Penicillium, Bacillus, Propionibacterium, Cladosporium, and Aspergillus. E. cloacae was isolated first on May 11, 198 1, from kidney preservation solution. Preparation of kidney preservation solution involved filtration under nitrogen pressure, but vacuum pump-assisted filling was not possible because this solution was packaged in glass bottles. Table 3 correlates production techniques of the five products prepared in the pressure cannister from May 11, 198 1, to September 24, 198 1, with results of microbiologic quality control tests. Of 91 specimens submitted from solutions prepared with the use of vacuum pump-assisted filling, five (5.5%) revealed E. cloucae. Of 60 specimens submitted from products for which the vacuum pump was not employed, one (1.7%) revealed E. cloucae (p = 0.403, two-tailed Fisher’s exact test). Thus there was no difference between the frequency of E. cloacae contamination of solutions prepared with vacuum pump assistance and the frequency of E. cloacae contamination of solutions prepared without vacuum pump-assisted filling. During the investigation, a member of the pharmacy CPS production team (W.E.J.) noted
+ + pump-assisted
of
with microbiologic
equipment Twin-90 filter
+ + + + +
solutions
Journal CONTROL
Samples submftted
qwlhy tests Samplee poeitive for E. chxtcee
79 12
5 0
44
0
10
0
6
1
ftlling, the remaining
three
solutions
ware
not
that some of the Twin-90 filters were cracked. The manufacturer was notified. Subsequently, a nationwide and international recall of Twin90 filters was initiated by the manufacturer.4
Although extrinsic contamination of CPS has recently been implicated in E. cloacae bacteremia and mediastinitis,j intrinsic CPS contamination has not previously been reported as far as we are aware. In other instances, intrinsic microbial contamination of pharmaceutical products has caused significant patient morbidity and mortality on both a nationwide6 and a loca17mg level. These problems often have been uncovered only after recognition and investigation of an epidemic. At our hospital, a microbiologically proven epidemic was not documented. Initial review of CPS production techniques immediately centered attention on the pressure cannister as a possible reservoir for E. cloucae. Environmental culturing confirmed this suspicion: E. cloacue of the same API profile number and antibiogram as that in the CPS was recovered from the pressure cannister. Cultures negative for this organism from other sites in the work area and in the CPS production system substantiated the hypothesized role of the pressure cannister. How the pressure cannister itself originally became contaminated is uncertain . Pharmacy personnel have been implicated in one other reported episode of product contamination.‘O Hand or nasal cultures were not performed to test this hypothesis. Since the pressure cannister indeed repre-
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12 Number
August,
1984
4
sented the likely reservoir for E. cloacae, it was necessary to explain how organisms contaminated the final CPS, since all solution passed through a 0.22 pm filter capable of removing bacteria. Engineering analysis initially suggested that the simultaneous use of the nitrogen pressure tank and the vacuum pump could generate pressures in excess of the 15 psi filter specification, which in turn could allow transfilter passage of bacteria with consequent CPS contamination. However, this hypothesis was not tenable since kidney preservation solution, which was prepared without use of the vacuum pump apparatus, was also contaminated with E. cbacae in one instance. The observation of occasional defective Twin-90 filters provided the likely explanation. Malfunction of the filters was in all likelihood the single event needed for contamination to occur, since the rates of E. cloacae contamination did not differ as a function of the presence (5.5% contamination rate) or absence (1.7% contamination rate) of vacuum pump assistance. It remains possible that excessive transfilter pressure could contribute to filter malfunction, but our findings do not support this hypothesis. Other data suggest that intact Twin-90 filters are capable of withstanding transmembrane pressures significantly in excess of 15 psi.” As a result of these findings, control measures were instituted. The pressure cannister is now sterilized before each use. In addition, it is disassembled every 2 weeks and thoroughly cleaned of any accumulated debris. To ensure that excessive transfilter pressure is not generated, the vacuum pump is no longer used to assist filling. Before use, filters are examined for gross defects. An integrity test is now performed on each unit after use. Quarantine of CPS awaiting microbiological clearance is strictly enforced. l2 When CPS is released, a precise record is maintained of the patients receiving it. Finally, a more extensive communication network linking the pharmacy, the microbiology laboratory, and the Infection Control Section has been established.12s l3 Following these changes, there has been no instance of E. cbacae contamination of any pharmacyprepared fluid.
Contaminated
cardioplegic
solution
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SUMMARY
Our conclusions and recommendations are as follows: 1. Pressurized cannisters used in the production of large-volume parenteral fluids may serve as a reservoir of bacterial contamination unless they are routinely disassembled, cleaned, and sterilized. 2. Filtration cannot be assumed to ensure sterility, since filters may be defective. Microbiologic quality control measures are essential. 3. Quality control procedures must be part of an established surveillance system for reporting of problems with large-volume solutions. Ideally, representatives of the pharmacy, the microbiology laboratory, and infection control should be involved. 4. Quarantine of products awaiting microbiological clearance should be strictly enforced. 5. Microbiologic quality control tests that reveal gram-negative rods must be viewed with concern and investigated appropriately. 6. Record keeping should allow precise, rapid identification of the specific patients receiving a pharmacy-prepared product. 7. The use of both positive and negative pressure to increase filtration rate conceiveably may produce a total pressure exceeding that recommended for the filter used. Therefore users of such filtration systems should periodically recalibrate pressure-monitoring gauges to ensure that excess pressure is not generated. We express our appreciation to the Microbiology Laboratory for their enthusiastic assistance in this investigation. Michael Soltys, Joseph Evans, and Frank Sharer kindly performed the engineering analysis. Dr. Ed Lusk provided statistical advice. We also thank Dr. Henry Edmunds and all other members of the Cardiothoracic Surgery Section for their cooperation and support. Ms. Mickey Campanile and Mrs. Hazel Price provided excellent secretarial assistance, and Ms. Cindy Friedman prepared the figure.
References 1. Kirklin JW, Conti VR, Blackstone EH: Prevention of myocardial damage during cardiac operations. N Engl J Med 301: 135 141, 1979. 2. Swerling R: The use and preparation of cardioplegic solutions in cardiac surgery. Hosp Pharm 15:497-503, 1980. 3. Armistead S, Collins GE, Bowman JD, et al: Prepara-
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4. 5.
6.
7.
8.
Talbot
et al.
tion of cardioplegic solutions. Am J Hosp Pharm 36:1361-1365, 1979. Food and Drug Administration: FDA enforcement report. Rockville, Md, March 9, 1983. Kalaidjian R, Tager IB: Bacteremia among aorticvalve surgery patients-Boston. Morbid Mortal Weekly Rep 31:88-89, 1982. Maki DG, Rhame FS, Mackel DC, Bennet JV: Nationwide epidemic of septicemia caused by contaminated intravenous products, I. Epidemiologic and clinical features. Am J Med 60~47 l-485, 1976. Sarubbi FA, Wilson B, Lee M, Brokopp C: Nosocomial meningitis and bacteremia due to contaminated amphotericin B. JAMA 239~416-418, 1978. Plouffe JF, Brown DG, Silva J, et al: Nosocomial outbreak of Candida parapsilosis fungemia related to intravenous infusions. Arch Intern Med 137: 1686- 1689, 1977.
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9. Phillips I, Eykyn S, Laker M: Outbreak of hospital infection caused by contaminated autoclaved fluids. Lancet 1: 1258- 1260, 1972. 10. Davis AT, Nadler HL, Brown MC, et al: Primary bacteremia. Morbid Mortal Weekly Rep 29: 110-l 11, 1976. 11. Leahy TJ, Sullivan MJ: Validation of bacterialretention capabilities of membrane filters. Pharm Tech 2:65-75, 1978. 12. National Coordinating Committee on Large Volume Parenterals: Recommended guidelines for quality assurance in hospital centralized intravenous admixture services. Am J Hosp Pharm 37:645-655, 1980. 13. National Coordinating Committee on Large Volume Parenterals: Recommended system for surveillance and reporting of problems with large-volume parenterals in hospitals. Am J Hosp Pharm 32: 125 l- 1253, 1975.
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