Emergence of highly antibiotic-resistant Pseudomonas aeruginosa in relation to duration of empirical antipseudomonal antibiotic treatment.

OBJECTIVE: This study examines antibiotic resistance in Pseudomonas aeruginosa in hospitalized patients in relation to prior empirical antibiotic therapy. DESIGN: Two retrospective case analyses comparing patients who manifested P aeruginosa with differing patterns of antibiotic resistance. SETTING AND PARTICIPANTS: Patients acquiring P aeruginosa in a community hospital. MEASURES: Patients were compared on duration of hospitalization and days and doses of antibiotics prior to recovery of P aeruginosa. Patients were grouped, based on susceptibility patterns of their P aeruginosa isolates classified as follows: (1) fully susceptible (susceptible to all classes of antipseudomonal antibiotics [SPA]), (2) multidrug-resistant (resistant to two classes of antipseudomonal antibiotics [MDRPA]), or (3) highly drug-resistant (resistant to > or = 6 classes of antipseudomonal antibiotics [HRPA]). To control for duration of hospitalization, antibiotic treatments of HRPA and SPA patients were compared during the first 21 days of care. RESULTS: Prior to recovery of HRPA, six HRPA patients received greater amounts of antibiotics, both antipseudomonal and non-antipseudomonal, than did six SPA patients prior to recovery of SPA. For 14 patients with hospital-acquired SPA who later manifested MDRPA, duration and dosage of antipseudomonal antibiotics, but not all antibiotics, were significantly higher for the SPA-to-MDRPA interval than for the preceding admission-to-SPA interval. The median duration of antipseudomonal antibiotic treatment prior to the recovery of P aeruginosa was 0 days for SPA, 11 days for MDRPA, and 24 days for HRPA. CONCLUSION: Duration of empirical antipseudomonal antibiotic treatment influences selection of resistant strains of P aeruginosa; the longer the duration, the broader the pattern of resistance.

Recorded criteria as a "gold standard" for sensitivity and specificity estimates of surveillance of nosocomial infection: a novel method to measure job performance.

OBJECTIVES: To compare the accuracy of infection control practitioners' (ICPs') classifications of operative site infection in Florida Consortium for Infection Control (FCIC) hospitals, in two time periods, 1990 to 1991 and 1991 to 1992, and to estimate the effect of duration of surveillance experience on that accuracy. METHODS: Medical record reviewers examined records of all patients classified by an ICP as infected, to distinguish false-positives from true infections based on evidence of standard infection criteria and the ICP's contemporaneous clinical observations. Reviewers also examined a random sample of 100 records from patients classified as noninfected for evidence of undetected infections (false-negatives). These observations permitted estimates of the sensitivity and specificity of each ICP's classification of infection status. SETTING: Fourteen FCIC community hospitals at which performance of 16 ICPs was monitored. RESULTS: There was a strong linear trend relating increasing sensitivity to numbers of years of ICP surveillance experience (P < .001). For ICPs with < 4 years of experience, satisfactory sensitivity (> or = 80%) was reached in only one of 10 ICP-years of observation. For ICPs with > or = 4 years' experience, satisfactory sensitivity was achieved for 14 of 18 person-years (P = .001). Estimated specificity was 97% to 100% for all ICP-years observed. CONCLUSIONS: ICPs with < 4 years of surveillance experience in FCIC community hospitals rarely achieved a satisfactory sensitivity estimate, whereas ICPs with > or = 4 years' experience generally did. Monitoring ICP surveillance accuracy through retrospective medical record audits offers an objective approach to evaluating ICP performance and to interpreting infection rates at different hospitals.

An apparent excess of operative site infections: analyses to evaluate false-positive diagnoses.

OBJECTIVE: To investigate an apparent excess of operative site infections (OSI) reported according to doctor's diagnosis (presumptive OSI) by applying objective criteria for classification (documented OSI). To examine potential consequences of habitual overdiagnosis of OSI. DESIGN: A case-control design was used to examine the clinical course of 18 case patients (12 presumptive OSI, six documented OSI) and 18 matched controls. Comparisons also were made between presumptive and documented OSI patients. SETTING: A nonteaching community hospital. PATIENTS: Thirty-six patients having laminectomies done by the same surgeon. INTERVENTION: Implementation of objective criteria for diagnosis of confirmed OSI and reclassification of presumptive OSI patients. RESULTS: Postoperatively, the frequency of specific adverse events within the operative site (including postoperative hematoma or bleeding; wound necrosis, dehiscence, or sinus tract; and dural tear) was 83% for documented OSI patients, contrasted with 16.7% for presumptive OSI patients (P < .01) and controls (P = .007). Median days of inpatient stay were 27 for documented OSI, contrasted with 9.5 for presumptive OSI (P = .01) and 7 for controls (P < .001). CONCLUSION: Documented OSI patients were found to have significantly more adverse findings and longer lengths of stay than presumptive OSI patients or controls. The similarity of findings for presumptive OSI patients and controls suggests that the apparent excess frequency of OSI was caused by incorrect diagnosis. Whereas doctor's diagnosis may be useful as an initial screen for OSI, use of objective criteria for confirming OSI may avert the consequences of overdiagnosis including excessive length of stay and unnecessary therapy, which lead to elevated healthcare costs and threaten a physician's practice.

Intervention to discontinue parenteral antimicrobial therapy in hospitalized patients with urinary tract infection, skin and soft tissue infection, or no evident infection.

OBJECTIVES: In a previous study, we found that unsolicited recommendations to physicians of medically stable patients with pneumonia to suspend parenteral antimicrobials shortened hospital length of stay (LOS) significantly. In this study, we made similar recommendations to physicians treating patients with different indications for parenteral antimicrobials, to examine the effect on LOS. METHODS: A nurse-interventionist presented randomly assigned physicians with nonconfrontational suggestions to discontinue parenteral antimicrobials by substituting comparable oral antimicrobials or stopping treatment. Patients were being treated for urinary tract infection, skin infection, or no evident infection. Blinded observers evaluated in-hospital and 30-day postdischarge patient courses. Methodologies were identical to the previous study. RESULTS: There were 70 physician-patient episodes (49 intervened episodes, 21 control episodes). In 44 episodes (90%), compliant physicians discontinued parenteral antimicrobials. Compared to a median postrandomization LOS of 2.5 days (range, 0 to 40.5) for 21 patients of control physicians, the corresponding LOS for 44 patients of compliant physicians was two days (range, 0 to 8; P = 1.0), and for five patients of noncompliant physicians, five days (range, 3 to 11; P = 0.04). The combined occurrence of all adverse events detected in this and the previous study was 11% for patients of control physicians, compared to 14% for patients of compliant physicians (P = 0.2), and 19% for patients of noncompliant physicians (P < 0.05). CONCLUSIONS: For patients of compliant physicians hospitalized with urinary tract infection, skin and soft tissue infection, or no evident infection, cessation of parenteral antimicrobials did not significantly shorten LOS, due to brief LOS of patients of control physicians. Patients of noncompliant physicians experienced more adverse events and prolonged LOS. The appropriateness of routine continuous use of parenteral antimicrobials in medically stable inpatients is questioned.

Lack of evidence of efficacy of cohorting nursing personnel in a neonatal intensive care unit to prevent contact spread of bacteria: an experimental study.

Nurse cohorting was investigated in a modern neonatal intensive care unit (NICU). During 99 days bacterial infection and colonization rates were determined in 100 infants experimentally assigned cohort or noncohorted care. Colonizing isolate identity was determined by plasmid profile analyses and biotyping in weekly surveillance cultures. Between Days 2 and 7, 3 infections occurred in cohorted infants but none in noncohorted ones. No secondary spread of infection or definitive colonization cluster occurred. The first colonization rate, at any site, was 0.53/patient-week in the noncohorted and 0.3 to 0.4 in the cohorted units (P greater than 0.05). Colonization ratios with species other than usual skin bacteria in the respiratory tract and with species other than Escherichia coli in the rectum were lower for noncohorted infants. Effective infection control practices in a modern NICU, including alcohol hand antisepsis, should obviate a need for cohorting.

Long term epidemiological analysis of Citrobacter diversus in a neonatal intensive care unit.

A prolonged outbreak of Citrobacter diversus central nervous system infection among hospitalized term infants, peaking in 1979, ceased with establishment of nurse-patient cohorting. The outbreak was attributed to dissemination of an epidemic strain among infants in an antiquated neonatal intensive care unit. When C. diversus colonization recurred within the new neonatal intensive care unit in 1984, cohorting and bacteriologic surveillance were reinstituted. By utilizing biotypes, plasmid profiles and antibiograms, four different C. diversus strains were identified circulating during 1979. Strains recovered between 1984 and 1988 from neonatal intensive care unit infants were similar to those from community-acquired sources. A strain considered avirulent in 1979 was found causing bacteremia in two infants (one with central nervous system disease) in 1984 to 1988. During cohorting C. diversus acquisition was 0.019/patient-month; after cohorting ceased it was 0.017/patient-month. Multiple source introductions appeared to occur with different C. diversus strains, some causing infant disease. No efficacy of cohorting was evident.

Intervention to discontinue parenteral antimicrobial therapy in patients hospitalized with pulmonary infections: effect on shortening patient stay.

OBJECTIVES: Current efforts to contain anti-microbial costs in hospitals are based on restricting drugs. We explored the effects of unsolicited case-specific recommendations to physicians to discontinue parenteral antimicrobial therapy in medically stable patients with pneumonia, in order to shorten hospital length of stay. METHODS: A nurse-interventionist, working as an emissary of an appropriate committee in 3 nonteaching community hospitals, presented randomly assigned physicians with nonconfrontational suggestions to substitute comparable oral antimicrobials for parenteral antimicrobials. Blinded observers evaluated in-hospital and 30-day postdischarge courses of patients of physicians who had been contacted by the nurse (cases) and those who had not (controls). RESULTS: Eighty-two patient episodes (47 physicians) met study criteria. There were 53 cases and 29 controls. In 42 of 53 (79%) case episodes, physicians discontinued parenteral antimicrobials; patients' mean length of stay was 2.4 days less than for 29 control episodes (estimated cost savings was $884/patient). In 11 (21%) episodes, case physicians continued parenteral therapy; patients' mean length of stay was 1.9 days longer than for controls (estimated cost excess was $704/patient). Education, training and practice characteristics were comparable in physician groups. Severity of illness indicators and postdischarge outcomes were comparable in patient groups. CONCLUSIONS: The major cost-saving potential for shifting from parenteral to oral antimicrobial therapy is shortened length of stay. Timely information about alternative drug therapies, offered on a patient-specific basis, appears to modify the treating behavior of physicians. The program as currently conducted is cost-effective, with an estimated net savings of $50,000 per 100 interventions.

Failure of bland soap handwash to prevent hand transfer of patient bacteria to urethral catheters.

OBJECTIVE: The study was designed to compare the efficacies of bland soap handwash and isopropyl alcohol hand rinse in preventing transfer of aerobic gram-negative bacilli to urinary catheters via transient hand colonization acquired from direct patient contact. Glove juice recovery of gram-negative bacteria was considered transient colonization; catheter recovery was considered transfer colonization. DESIGN: The contact source for gram-negative bacteria was a single "high burden" groin skin carrier (greater than or equal to 10(4)/ml cup scrub fluid). Using a two-period cross-over design, 6 healthcare workers had 2 15-second contacts for each hand followed by either soap handwash or alcohol hand rinse (12 experiments with each treatment). Between 4 to 5 minutes after contact, each hand manipulated a catheter; the catheter was then cultured and the hand was glove juice tested. RESULTS: Soap handwash failed to prevent gram-negative bacteria transfer to the catheter in 11 of 12 (92%) experiments; alcohol hand rinse in 2 of 12 (17%) (p less than .001). Soap handwash failed to prevent transient colonization in 12 of 12 (100%) experiments; alcohol in 5 of 12 (42%) (risk ratio 2.4, 95% confidence interval 1.2-4.7). Single gram-negative bacteria species carried at source levels greater than or equal to 5.5 x 10(3)/ml (heavy contamination) established transient colonization in 23 of 30 (77%) exposures following soap handwash; single gram-negative bacteria species carried at levels less than or equal to 3.5 x 10(3)/ml established colonization in 1 of 22 (5%) similar exposures (p less than .001). CONCLUSIONS: Bland soap handwash was generally ineffective in preventing hand transfer of gram-negative bacteria to catheters following brief contact with a heavy-contamination patient source; alcohol hand rinse was generally effective.

Mediastinitis complicating cardiac operations: evidence of postoperative causation.

An excess rate of mediastinitis complicating cardiac operations occurred in one of two hospitals served by the same surgeons. The rates were 4% at hospital A and 0.48% at hospital B for the same period (P = .002). At hospital A five patients who underwent a thoracic reoperation experienced postoperative pneumonia or bacteremia prior to onset of mediastinitis; these infections were caused by the same bacterial species. This circumstance provided a unique opportunity for comparing infection control practices, in which one hospital served as a control for interventional changes. At hospital A regular and temporary critical care nursing personnel, who took care of both infected and uninfected patients, did not antisepticize their hands before manipulation of percutaneous catheters. After cohorts of nurses were formed and antisepsis of the hands with alcohol was strictly enforced (no diminution in the number of temporary personnel was instituted), the frequency of mediastinitis decreased significantly among patients who underwent reoperations at hospital A (P = .002), but no concurrent change was noted at hospital B. Preventable postoperative remote-site infection may lead to mediastinitis.

Irrigation-aspiration for culturing draining decubitus ulcers: correlation of bacteriological findings with a clinical inflammatory scoring index.

Biopsy of infected decubitus ulcers for culture disrupts tissues and may disseminate infection. Antimicrobial prophylaxis to prevent dissemination of infection may adversely affect biopsy culture results. Irrigation-aspiration to obtain submarginal specimens from draining decubitus ulcers was studied as an atraumatic, noninvasive culturing technique to serve as an alternative to biopsy in research activities. Two aspirates were obtained serially from 32 subjects; in 12 subjects, biopsies were also performed immediately. A median of 4.5 bacterial species was recovered per ulcer by irrigation-aspiration. Recent antimicrobial treatment had no evident effect on the recovery of bacterial species in general or, specifically, on the recovery of Bacteroides species. Concordance of results for both aspirates was 97.6% for aerobes and 91.8% for anaerobes, indicating no interactive methodological effect of the first irrigation-aspiration on the second. Compared with biopsy isolates for one aspirate, the sensitivity was 93% and the specificity was 99.0%; for another aspirate, the sensitivity was 94.7% and the specificity was 99.5%. The positive predictive value for either aspirate was greater than or equal to 93.9%. A weighted clinical index to score inflammatory ulcer characteristics was devised (score range, 0 to 15). In the absence of anaerobes in 15 subjects, the mean score was 6.1 +/- 3.5; in the presence of anaerobes in 17 subjects, the mean score was 9.4 +/- 3.2 (P = 0.008). The presence of aerobic gram-positive or gram-negative species did not significantly affect scores. Irrigation-aspiration for culture and clinical scoring of inflammation should permit independent serial measures of bacteriological and clinical courses of draining decubitus ulcers without patient risk or discomfort.

Infections complicating low-risk cesarean sections in community hospitals: efficacy of antimicrobial prophylaxis.

A prospective study of women with low-risk cesarean sections was conducted in four community hospitals to determine the frequency of postoperative infections and identify factors predisposing to endometritis and wound infection. Low-risk cesarean section was defined as a scheduled procedure without an urgent indication, with any duration of ruptured membranes being less than or equal to 12 hours. In a cohort of 1863 patients, 26 (1.4%) developed endometritis and 21 (1.1%) had wound infections. Primary cesarean section was associated with endometritis in the cohort (p less than 0.01) and in a retrospective study with the same cases as in the cohort (p = 0.01). Absence of antibiotic prophylaxis was associated with endometritis (p less than or equal to 0.013) or endometritis with wound infection (p less than 0.01) in both studies. Without prophylaxis 37 such infections occurred in 957 (3.7%) women; with prophylaxis eight infections occurred in 906 (0.9%) women. Routine timely antibiotic prophylaxis in low-risk cesarean sections could lead to an annual national savings of approximately $9 million.

Containing costs of antimicrobials in the hospital: a critical evaluation.

Because reimbursement of hospitals from patient sources for the cost of antimicrobial agents varies considerably according to the nature of the patient population, the actual savings potential of cost-containment efforts is proportional to the extent that costs are not reimbursed. Meaningful cost estimations include calculations for drug preparation, administration, necessary laboratory tests, toxicity, and acquisition. Savings in surgical antimicrobial prophylaxis may be estimated according to the type and volume of operations, history of usage excesses, and anticipated degree of cooperation of surgeons. In therapy, savings generally derive from restricting use of costly drugs. Studies that demonstrate similar outcomes of patient care in restricted and unrestricted settings are presently lacking. Such studies are essential for programs that promote change from parenteral to oral antimicrobials, because they may shorten the length of hospitalization. The outcome of antimicrobial cost-containment efforts in patient care should be monitored as a surveillance activity to be conducted by infection control practitioners involved with quality assessment.

Proteeae species bacteriuria accompanying Proteeae species groin skin carriage in geriatric outpatients.

There have been numerous reports of Proteeae species urinary tract infections among elderly individuals. To explore a possible urinary carrier source of Proteeae species in this population, the frequency of aerobic gram-negative bacillus (AGNB) bacteriuria at the greater than or equal to 10(2)/ml level was determined in 67 ambulatory elderly outpatients classified as to Proteeae group (Morganella, Proteus, Providencia) groin carriage by a set of two skin cultures obtained at least 1 week apart. None had urethral catheters, symptomatic infections, skin ulcers, or recent antibiotic therapy. We found AGNB bacteriuria in 12 of 15 carriers (80%) and in 21 of 52 noncarriers (40%) (P = 0.009). Proteeae species bacteriuria occurred in eight carriers (53.3%) and six noncarriers (11.5%) (P = 0.001). At the 10(2) to 10(4)/ml level, Proteeae species were isolated in urine specimens from seven carriers (46.7%) and four noncarriers (7.7%) (P = 0.001). There was concordance of species of skin and urine Proteeae isolates in six carriers. By contrast, non-Proteeae AGNB bacteriuria at any level was present in four Proteeae species carriers (26%) and 15 noncarriers (28.8%) (P greater than 0.05). There was a 36.7% frequency of Proteeae species bacteriuria in nursing home residents, in contrast to 8.1% among those living in private homes; this parallels the greater frequency of Proteeae species groin carriage among nursing home residents in the study population. Low-level urinary colonization with Proteeae species accompanying Proteeae species groin skin colonization in elderly individuals is a hitherto unrecognized finding. This may account for the greater frequency of Proteeae species urinary infections in this population.

Indications for alcohol or bland soap in removal of aerobic gram-negative skin bacteria: assessment by a novel method.

A patient contact model was devised for health care workers (HCWs) to define heavy hand contamination with aerobic gram-negative bacilli (AGNB) that requires alcohol for complete removal. In patients, AGNB quantitation was per ml cup scrub fluid; in HCWs per ml glove juice. Following 15-second contact, two Proteeae groin carriers yielding greater than or equal to 4 log10 AGNB (high burden) transmitted greater than or equal to 3 log10 in 67% of 24 tests of six HCWs, and less than or equal to 2 log10 in 29%. Two carriers yielding less than or equal to 3 log10 in 38%. At less than or equal to 2 log10 HCW acquisitions, soap eliminated all AGNB in three of 10; alcohol in eight of eight (p = 0.009). Contact with densely colonized patient skin may cause heavy AGNB contamination of HCWs' hands that generally necessitates alcohol for complete removal.