Immunogenicity and reactogenicity of high- vs. standard-dose trivalent inactivated influenza vaccine in healthcare workers: a pilot randomized controlled trial

OBJECTIVES

To compare immunogenicity, reactogenicity and acceptability of high- and standard-dose trivalent inactivated influenza vaccine (HDTIV, SDTIV) in 18- to 64-year-olds.

METHODS

We randomized 18- to 64-year-olds to HDTIV or SDTIV in two consecutive years. We collected serum on days 0 and 21, measured haemagglutination inhibition geometric mean titres (GMT) and compared seroconversion, day 21 titres, seroprotection, reactogenicity and acceptability.

RESULTS

Immunogenicity was evaluable in 42 of 47 2014 participants, all 33 both-year participants and 87 of 90 2015-only participants. First-dose HDTIV recipients experienced seroconversion more frequently than SDTIV recipients to A(H3N2) in 2014 (13/21, 62% vs. 4/21, 19%, p 0.01) and to all vaccine strains in 2015: (A(H1N1): 24/42, 57% vs. 15/59, 25%; A(H3N2): 42/42, 100% vs. 47/59, 80%; B: 25/42, 60% vs. 13/59, 22%; all p <0.01). Day 21 haemagglutination inhibition GMT were higher in first and two sequential-year HDTIV vs. SDTIV recipients: A(H1N1): GMT 749 and 768 vs. 384 (p <0.0001, p 0.002); A(H3N2): 1238 and 956 vs. 633 (p 0.0003, p 0.1); and B: 1113 and 1086 vs. 556 (p 0.0005, p 0.02). HDTIV was more reactogenic (local pain score 3 vs. 1 of 10 on day 0/1, p 0.0003), but recipients were equally willing to be revaccinated (HDTIV: 76/83 (92%); SDTIV: 76/80 (95%), p 0.54). The ratios of day 21 GMT in SDTIV recipients vaccinated in 0 to 4 prior years to those in SDTIV and HDTIV recipients vaccinated in 15 or more prior years were A(H1N1): 3.73 and 1.38; A(H3N2) 3.07 and 1.16; and B: 2.01 and 1.21.

CONCLUSIONS

HDTIV is more immunogenic and reactogenic and as acceptable as SDTIV in 18- to 64-year-olds.

Is the prevalence of antibiotic-resistant organisms changing in Canadian hospitals? Comparison of point-prevalence survey results in 2010 and 2012

A national point-prevalence survey for infection or colonization with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), and for Clostridium difficile infection (CDI) was done in Canadian hospitals in 2010. A follow-up survey was done in November 2012 to determine whether there were any changes in the prevalence of these organisms; we also determined the prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae, and carbapenem-resistant Enterobacteriaceae (CREs). Associations between prevalence and infection prevention and control policies were evaluated in logistic regression models. A total of 143 (67% of eligible facilities) hospitals with 29 042 adult inpatients participated in the survey, with representation from all 10 provinces; 132 hospitals participated in 2010 and 2012. There were no significant changes in the median prevalence of MRSA in 2010 (4.3%) compared to 2012 (3.9%), or of CDI in 2010 (0.8%) compared to 2012 (0.9%). A higher median prevalence of VRE was identified in 2012 (1.3%) compared to 2010 (0.5%) (p 0.04), despite decreased VRE screening in 2012. The median prevalence of ESBLs was 0.7% and was 0 for CREs; CREs were reported from only 10 hospitals (7.0%). A policy of routinely caring for patients with MRSA or VRE in a private isolation room was associated with lower prevalence of these organisms. Targeted screening of high-risk patients at admission was associated with lower MRSA prevalence; better hand hygiene compliance was associated with lower VRE prevalence. These data provide national prevalence rates for antibiotic-resistant organisms among adults hospitalized in Canadian hospitals. Certain infection prevention and control policies were associated with prevalence.

Factors Associated With Critical-Care Healthcare Workers' Adherence to Recommended Barrier Precautions During the Toronto Severe Acute Respiratory Syndrome Outbreak

Objective.

To assess factors associated with adherence to recommended barrier precautions among healthcare workers (HCWs) providing care to critically ill patients with severe acute respiratory syndrome (SARS).

Setting.

Fifteen acute care hospitals in Ontario, Canada

Design.

Retrospective cohort study.

Patients.

All patients with SARS who required intubation during the Toronto SARS outbreak in 2003.

Participants.

HCWS who provided care to or entered the room of a SARS patient during the period from 24 hours before intubation until 4 hours after intubation.

Methods.

Standardized interviews were conducted with eligible HCWs to assess their interactions with the SARS patient, their use of barrier precautions, their practices for removing personal protective equipment, and the infection control training they received.

Results.

Of 879 eligible HCWs, 795 (90%) participated. In multivariate analysis, the following predictors of consistent adherence to recommended barrier precautions were identified: recognition of the patient as a SARS case (odds ratio [OR], 2.5 [95% confidence interval {CI}, 1.5-4.5); recent infection control training (OR for interactive training, 2.7 [95% CI, 1.7-4.4]; OR for passive training, 1.7 [95% CI, 1.0-3.0]), and working in a SARS unit (OR, 4.0 [95% CI, 1.8-8.9]) or intensive care unit (OR, 4.3 [95% CI, 2.0-9.0]). Two factors were associated with significantly lower rates of consistent adherence: the provision of care for patients with higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores (OR for score APACHE II of 20 or greater, 0.4 [95% CI, 0.28-0.68]) and work on shifts that required more frequent room entry (OR for 6 or more entries per shift, 0.5 [95% CI, 0.32-0.86]).

Conclusions.

There were significant deficits in knowledge about self-protection that were partially corrected by education programs during the SARS outbreak. HCWs' adherence to self-protection guidelines was most closely associated with whether they provided care to patients who had received a definite diagnosis of SARS.

Detection of severe acute respiratory syndrome coronavirus in stool specimens by commercially available real-time reverse transcriptase PCR assays

Three commercially available real-time reverse transcriptase PCR assays (the Artus RealArt HPA coronavirus LightCycler, the Artus RealArt HPA coronavirus Rotor-Gene, and the EraGen severe acute respiratory syndrome coronavirus POL assay) and three RNA extraction methodologies were evaluated for the detection of severe acute respiratory syndrome coronavirus RNA from 91 stool specimens. The assays' sensitivities were highest (58% to 75%) for specimens obtained 8 to 21 days after symptom onset. The assays were less sensitive when specimens were obtained less than 8 days or more than 21 days after the onset of symptoms. All assays were 100% specific.

Hospital-acquired invasive group a streptococcal infections in Ontario, Canada, 1992-2000

BACKGROUND

A significant proportion of invasive group A streptococcal infections are hospital acquired. No large, prospective studies have characterized this subgroup of cases and evaluated the risk of transmission in hospitals.

METHODS

We conducted prospective, population-based surveillance of invasive group A streptococcal infections in Ontario, Canada, from 1992 to 2000. Epidemiologic and microbiologic investigations were conducted to identify cross-transmission.

RESULTS

We identified 291 hospital-acquired cases (12.4%) among 2351 cases of invasive group A streptococcal disease. Hospital-acquired invasive group A streptococcal infections are heterogeneous, including surgical site (96 cases), postpartum (86 cases), and nonsurgical, nonobstetrical infections (109 cases). Surgical site infections affected 1 of 100,000 surgical procedures and involved all organ systems. Postpartum infections occurred at a rate of 0.7 cases per 10,000 live births and exhibited an excellent prognosis. Nonsurgical, nonobstetrical infections encompassed a broad range of infectious syndromes (case-fatality rate, 37%). Nine percent of cases were associated with in-hospital transmission. Transmission occurred from 3 of 142 patients with community-acquired cases of necrotizing fasciitis requiring intensive care unit (ICU) admission, compared with 1 of 367 patients with community-acquired cases without necrotizing fasciitis admitted to the ICU and 1 of 1551 patients with other cases (P<.001). Fifteen outbreaks were identified; 9 (60%) involved only 2 cases. Hospital staff were infected in 1 of 15 outbreaks, but colonized staff were identified in 6 (60%) of 10 investigations in which staff were screened.

CONCLUSIONS

Presentation of hospital-associated invasive group A streptococcal infections is diverse. Cross-transmission is common; illness occurs in patients but rarely in staff. Isolation of new cases of necrotizing fasciitis and intervention after a single nosocomial case may also prevent transmission.

Rapid detection of methicillin-resistant staphylococci from blood culture bottles by using a multiplex PCR assay

Rapid detection and accurate identification of methicillin-resistant staphylococci are critical for the effective management of infections caused by these organisms. We describe a multiplex PCR-based assay for the direct detection of methicillin-resistant staphylococci from blood culture bottles (BacT/Alert; Organon-Teknika, Durham, N.C.). A simple lysis method followed by a multiplex PCR assay designed to detect the nuc, mecA, and bacterial 16S rRNA genes was performed. A total of 306 blood culture specimens were collected over a period of 10 months from June 1998 to April 1999, consisting of 236 blood cultures growing staphylococci (including 124 methicillin-resistant Staphylococcus spp.), 50 positive blood cultures which grew organisms other than staphylococci, and 20 blood cultures that were negative for bacterial and fungal pathogens after 5 days of incubation and terminal subculture. DNA extraction, PCR, and detection could be completed in 2.5 h. Of the positive blood cultures with staphylococci, the multiplex PCR assay had a sensitivity and specificity of 99.2% and 100%, respectively. Our results show that rapid, direct detection of methicillin-resistant staphylococci is possible, allowing clinicians to make prompt and effective decisions for the management of patients with staphylococcal bacteremia.

Adherence to antibiotic guidelines for pneumonia in chronic-care facilities in Ontario

OBJECTIVES

To evaluate adherence to antibiotic recommendations for the treatment of pneumonia in patients who receive long-term care and to assess outcomes associated with these recommendations.

DESIGN

A prospective cohort study.

SETTING

Twenty-two facilities that provide long-term care in southern Ontario.

PARTICIPANTS

Older adults treated with antibiotics for a presumptive diagnosis of pneumonia and those with radiologically confirmed pneumonia

METHODS

Over a 12-month period, older patients who were treated with antibiotics for presumptive pneumonia were prospectively identified. A random sample of these antibiotic courses (646 courses in 638 patients) was reviewed using a standardized data collection form, and demographic and clinical data were collected. Antibiotic courses were classified according to Canadian and American Thoracic Society antibiotic recommendations for pneumonia. In patients with radiologically confirmed pneumonia, the effect of adherence to these recommendations on mortality and persistence of symptoms was assessed.

RESULTS

Only 27.6% (178 of 646) of antibiotic prescriptions evaluated met antibiotic recommendations for nursing-home-acquired pneumonia, and the proportion meeting these varied greatly by facility, ranging from 0% to 53% (median 31%). For patients with radiologically confirmed pneumonia, age (adjusted odds ratio [OR] 1.6, 95% confidence interval [CI] 1.0-2.4, per increase in 10 yr, p = 0.02), sex (adjusted OR 3.0, 95% CI 1.1-8.0, p = 0.03), and adherence to recommended antibiotics (OR 3.0, 95% CI 1.3-7.2, p = 0.01) were associated with death. Adherence to the recommended antibiotics was also associated with adverse reactions, which occurred in 10% of prescriptions meeting the recommendations (OR 2.4, 95% CI 1.3-4.6, p = 0.01).

CONCLUSIONS

Adherence to recommended guidelines for antibiotic treatment was low and highly variable among study facilities. Use of recommended antibiotic regimens was associated with increased adverse events and worse outcomes in patients with radiologically confirmed pneumonia.

Evaluation of a latex agglutination test (MRSA-Screen) for detection of oxacillin resistance in coagulase-negative Staphylococci

The MRSA-Screen (Denka-Seiken, Tokyo, Japan) latex agglutination test was evaluated for its ability to detect PBP 2a from 200 clinical isolates of coagulase-negative staphylococci (CoNS; 84 mecA-positive strains and 116 mecA-negative strains) consisting of 108 Staphylococcus epidermidis, 37 S. saprophyticus, 15 S. haemolyticus, 11 S. hominis, 10 S. capitis, 10 S. warneri, and 3 S. lugdunensis species as well as 6 other species of CoNS. The assay was compared with susceptibility testing with an agar screen plate with oxacillin at 6 microg/ml (OXA6), by oxacillin disk diffusion (DD), by broth microdilution (BMDIL), by the E test, and with Vitek GPS-SV and Vitek GPS-107 susceptibility cards. PCR for the detection of the mecA gene was used as the "gold standard." The sensitivities and specificities for the methods evaluated were as follows: MRSA-Screen, 100 and 100%, respectively; OXA6, 100 and 99%, respectively; DD, 98 and 62%, respectively; BMDIL, 100 and 60%, respectively; E test, 100 and 51%, respectively; Vitek GPS-SV susceptibility card, 98 and 87%, respectively; and Vitek GPS-107 susceptibility card, 100 and 61%, respectively. The MRSA-Screen test accurately and rapidly detected oxacillin resistance in CoNS.

Containing methicillin-resistant S aureus. Surveillance, control, and treatment methods

In the past two decades, the prevalence of MRSA has increased in healthcare facilities in many countries around the world. The organism, which has caused nosocomial outbreaks, also has become endemic in many hospitals and long-term care facilities. Recently, reports of community-acquired MRSA in persons without known risk factors for the organism have been increasing. Transmission occurs primarily from colonized or infected patients to others through the hands of healthcare personnel. MRSA infection may be life-threatening and cause considerable morbidity, the need for prolonged hospitalization, and increased costs. Treatment options are limited because organisms are typically resistant to multiple antibiotics, but newer agents are being developed. However, there is also reason for concern about the recent emergence of MRSA resistant to glycopeptides, such as vancomycin. Efforts to limit the spread of MRSA should include surveillance and control measures, such as adequate hand hygiene and appropriate contact isolation or barrier precautions.

The evolution of methicillin-resistant Staphylococcus aureus in Canadian hospitals: 5 years of national surveillance

BACKGROUND

To better understand the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in Canadian hospitals, surveillance has been conducted in sentinel hospitals across the country since 1995. We report the results of the first 5 years of the program.

METHODS

For each newly identified inpatient with MRSA, medical records were reviewed for demographic and clinical data. Isolates were subjected to susceptibility testing and molecular typing by pulsed-field gel electrophoresis.

RESULTS

A total of 4507 patients infected or colonized with MRSA were identified between January 1995 and December 1999. The rate of MRSA increased each year from a mean of 0.95 per 100 S. aureus isolates in 1995 to 5.97 per 100 isolates in 1999 (0.46 per 1000 admissions in 1995 to 4.12 per 1000 admissions in 1999) (p < 0.05). Most of the increase in MRSA occurred in Ontario, Quebec and the western provinces. Of the 3009 cases for which the site of MRSA acquisition could be determined, 86% were acquired in a hospital, 8% were acquired in a long-term care facility and 6% were acquired in the community. A total of 1603 patients (36%) were infected with MRSA. The most common sites of infection were skin or soft tissue (25% of MRSA infections), pulmonary tissues (24%) and surgical sites (23%); 13% of the patients were bacteremic. An epidemiologic link with a previously identified MRSA patient was suspected in 53% of the cases. Molecular typing indicated that most (81%) of the isolates could be classified as related to 1 of the 4 Canadian epidemic strains of MRSA.

INTERPRETATION

There has been a significant increase in the rate of isolating MRSA in many Canadian hospitals, related to the transmission of a relatively small number of MRSA strains.

The role of the laboratory in infection prevention and control programs in long-term-care facilities for the elderly

Hospital infection prevention and control programs rely extensively on diagnostic microbiology laboratory testing. However, specimens for microbiological evaluation are less likely to be obtained from elderly residents of long-term-care facilities (LTCFs). In this article, issues regarding laboratory utilization and the potential role of the microbiology laboratory in infection prevention and control programs in LTCFs are reviewed. The role of the laboratory in infection surveillance, in the management of antimicrobial resistance, and in outbreak investigation are highlighted.

Antibiotic use in Ontario facilities that provide chronic care

OBJECTIVE

To determine the incidence and variability of antibiotic use in facilities which provide chronic care and to determine how often clinical criteria for infection are met when antibiotics are prescribed in these facilities.

DESIGN

A prospective, 12-month, observational cohort study.

SETTING

Twenty-two facilities which provide chronic care in southwestern Ontario.

PARTICIPANTS

Patients who were treated with systemic antibiotics over the study period.

MEASUREMENTS

Characteristics of antibiotic prescriptions (name, dose, duration, and indication) and clinical features of randomly selected patients who were treated with antibiotics.

RESULTS

A total of 9,373 courses of antibiotics were prescribed for 2,408 patients (66% of all patients in study facilities). The incidence of antibiotic prescriptions in the facilities ranged from 2.9 to 13.9 antibiotic courses per 1,000 patient-days. Thirty-six percent of antibiotics were prescribed for respiratory tract infections, 33% for urinary infections, and 13% for skin and soft tissue infections. Standardized surveillance definitions of infection were met in 49% of the 1,602 randomly selected patients who were prescribed antibiotics. Diagnostic criteria for respiratory, urinary, and skin infection were met in 58%, 28%, and 65% of prescriptions, respectively. One third of antibiotic prescriptions for a urinary indication were for asymptomatic bacteriuria. Adverse reactions were noted in 6% of prescriptions for respiratory and urinary infections and 4% of prescriptions for skin infection.

CONCLUSIONS

Antibiotic use is frequent and highly variable amongst patients who receive chronic care. Reducing antibiotic prescriptions for asymptomatic bacteriuria represents an important way to optimize antibiotic use in this population.

The economic impact of methicillin-resistant Staphylococcus aureus in Canadian hospitals

OBJECTIVES

To determine the costs associated with the management of hospitalized patients with methicillin-resistant Staphylococcus aureus (MRSA), and to estimate the economic burden associated with MRSA in Canadian hospitals.

DESIGN

Patient-specific costs were used to determine the attributable cost of MRSA associated with excess hospitalization and concurrent treatment. Excess hospitalization for infected patients was identified using the Appropriateness Evaluation Protocol, a criterion-based chart review process to determine the need for each day of hospitalization. Concurrent treatment costs were identified through chart review for days in isolation, antimicrobial therapy, and MRSA screening tests. The economic burden to Canadian hospitals was estimated based on 3,167,521 hospital discharges for 1996 and 1997 and an incidence of 4.12 MRSA cases per 1,000 admissions.

SETTING

A tertiary-care, university-affiliated teaching hospital in Toronto, Ontario, Canada.

PATIENTS

Inpatients with at least one culture yielding MRSA between April 1996 and March 1998.

RESULTS

A total of 20 patients with MRSA infections and 79 colonized patients (with 94 admissions) were identified. This represented a rate of 2.9 MRSA cases per 1,000 admissions. The mean number of additional hospital days attributable to MRSA infection was 14, with 11 admissions having at least 1 attributable day. The total attributable cost to treat MRSA infections was $287,200, or $14,360 per patient The cost for isolation and management of colonized patients was $128,095, or $1,363 per admission. Costs for MRSA screening in the hospital were $109,813. Assuming an infection rate of 10% to 20%, we determined the costs associated with MRSA in Canadian hospitals to be $42 million to $59 million annually.

CONCLUSIONS

These results indicate that there is a substantial economic burden associated with MRSA in Canadian hospitals. These costs will continue to rise if the incidence of MRSA increases further.

Development of minimum criteria for the initiation of antibiotics in residents of long-term-care facilities: results of a consensus conference

Establishing a clinical diagnosis of infection in residents of long-term-care facilities (LTCFs) is difficult. As a result, deciding when to initiate antibiotics can be particularly challenging. This article describes the establishment of minimum criteria for the initiation of antibiotics in residents of LTCFs. Experts in this area were invited to participate in a consensus conference. Using a modified delphi approach, a questionnaire and selected relevant articles were sent to participants who were asked to rank individual signs and symptoms with respect to their relative importance. Using the results of the weighting by participants, a modification of the nominal group process was used to achieve consensus. Criteria for initiating antibiotics for skin and soft-tissue infections, respiratory infections, urinary infections, and fever where the focus of infection is unknown were developed.

Novel cases of blastomycosis acquired in Toronto, Ontario

Blastomycosis a potentially fatal fungal disease, is well known from defined areas of endemicity in Ontario, primarily in the northern part of the province. We present 2 unusual cases that appear to extend the area of endemicity into urban southern Ontario, specifically Toronto. Both patients presented to a dermatology clinic with skin lesions. Chest radiography, history and general physical evaluation indicated no disease at other body sites. Both cases appeared to represent "inoculation blastomycosis" connected with minor gardening injuries and a cat scratch respectively. Atypical dissemination could not be completely excluded in either case. Neither patient had travelled recently to a known area of high endemicity for blastomycosis, nor had the cat that was involved in one of the cases. Physicians must become aware that blastomycosis may mimic other diseases, including dermal infections, and may occur in patients whose travel histories would not normally suggest this infection.

PCR detection of Escherichia coli O157:H7 directly from stools: evaluation of commercial extraction methods for purifying fecal DNA

Rapid identification of Escherichia coli O157:H7 is important for patient management and for prompt epidemiological investigations. We evaluated one in-house method and three commercially available kits for their ability to extract E. coli O157:H7 DNA directly from stool specimens for PCR. Of the 153 stool specimens tested, 107 were culture positive and 46 were culture negative. The sensitivities and specificities of the in-house enrichment method, IsoQuick kit, NucliSens kit, and QIAamp kit were comparable, as follows: 83 and 98%, 85 and 100%, 74 and 98%, and 86 and 100%, respectively. False-negative PCR results may be due to the presence of either inherent inhibitors or small numbers of organisms. The presence of large amounts of bacteria relative to the amount of the E. coli O157:H7 target may result in the lower sensitivities of the assays. All commercial kits were rapid and easy to use, although DNA extracted with the QIAamp kit did not require further dilution of the DNA template prior to PCR.

Why are antibiotics prescribed for asymptomatic bacteriuria in institutionalized elderly people? A qualitative study of physicians' and nurses' perceptions

BACKGROUND

Antibiotic therapy for asymptomatic bacteriuria in institutionalized elderly people has not been shown to be of benefit and may in fact be harmful; however, antibiotics are still frequently used to treat asymptomatic bacteriuria in this population. The aim of this study was to explore the perceptions, attitudes and opinions of physicians and nurses involved in the process of prescribing antibiotics for asymptomatic bacteriuria in institutionalized elderly people.

METHODS

Focus groups were conducted among physicians and nurses who provide care to residents of long-term care facilities in Hamilton, Ont. A total of 22 physicians and 16 nurses participated. The focus group discussions were tape-recorded, and the transcripts of each session were analysed for issues and themes emerging from the text. Content analysis using an open analytic approach was used to explore and understand the experience of the focus group participants. The data from the text were then coded according to the relevant and emergent themes and issues.

RESULTS

We observed that the ordering of urine cultures and the prescribing of antibiotics for residents with asymptomatic bacteriuria were influenced by a wide range of nonspecific symptoms or signs in residents. The physicians felt that the presence of these signs justified a decision to order antibiotics. Nurses played a central role in both the ordering of urine cultures and the decision to prescribe antibiotics through their awareness of changes in residents' status and communication of this to physicians. Education about asymptomatic bacteriuria was viewed as an important priority for both physicians and nurses.

INTERPRETATION

The presence of non-urinary symptoms and signs is an important factor in the prescription of antibiotics for asymptomatic bacteriuria in institutionalized elderly people. However, no evidence exists to support this reason for antibiotic treatment. Health care providers at long-term care facilities need more education about antibiotic use and asymptomatic bacteriuria.

The role of DNA amplification technology in the diagnosis of infectious diseases

Nucleic acid amplification and detection methods developed in the past decade are useful for the diagnosis and management of a variety of infectious diseases. The most widely used of these methods is the polymerase chain reaction (PCR). PCR assays can detect rapidly and accurately the presence of fastidious and slow-growing microorganisms, such as Chlamydia, mycoplasmas, mycobacteria, herpesviruses and enteroviruses, directly from clinical specimens. Commercial PCR assays for the diagnosis of tuberculosis and genital C. trachomatis infection are now routinely used in many diagnostic laboratories. Assays have also been developed that can detect antimicrobial resistance and are used to identify the cause of infection by organisms that cannot be cultivated. The value of viral load measurement by nucleic acid amplification in the management of patients with HIV infection or hepatitis C has also been well established. However, evaluations of this technology for rapid microbial diagnosis have generally been limited by small samples, and the cost of these assays may be as high as Can$125 per test. As nucleic acid amplification methods continue to evolve, their role in the diagnosis and management of patients with infectious diseases and their impact on clinical outcomes will become better defined.

Evaluation of three rapid methods for detection of methicillin resistance in Staphylococcus aureus

The probe-based Velogene Rapid MRSA Identification Assay (ID Biomedical Corp., Vancouver, British Columbia, Canada) and the latex agglutination MRSA-Screen (Denka Seiken Co., Tokyo, Japan) were evaluated for their ability to identify methicillin-resistant Staphylococcus aureus (MRSA) and to distinguish strains of MRSA from borderline oxacillin-resistant S. aureus (BORSA; mecA-negative, oxacillin MICs of 2 to 8 microgram/ml). The Velogene is a 90-min assay using a chimeric probe to detect the mecA gene. MRSA-Screen is a 15-min latex agglutination test with penicillin-binding protein 2a antibody-sensitized latex particles. We compared these assays with the BBL Crystal MRSA ID System (Becton Dickinson, Cockeysville, Md.) and with PCR for mecA gene detection. A total of 397 clinical isolates of S. aureus were tested, consisting of 164 methicillin-susceptible strains, 197 MRSA strains, and 37 BORSA strains. All assays performed well for the identification of MRSA with sensitivities and specificities for Velogene, MRSA-Screen, and BBL Crystal MRSA ID of 98.5 and 100%, 98.5 and 100%, and 98.5 and 98%, respectively. Three MRSA strains were not correctly identified by each of the Velogene and MRSA-Screen assays, but repeat testing with a larger inoculum resolved the discrepancies. The BBL Crystal MRSA ID test misclassified four BORSA strains as MRSA. Both the Velogene and the MRSA-Screen assays are easy to perform, can accurately differentiate BORSA isolates from MRSA isolates, and provide a rapid alternative for the detection of methicillin resistance in S. aureus in clinical laboratories, especially when mecA PCR gene detection is unavailable.

Evaluation of the BacT/Alert microbial detection system with FAN aerobic and FAN anaerobic bottles for culturing normally sterile body fluids other than blood

We evaluated the BacT/Alert Microbial Detection System (Organon Teknika Corporation, Durham, NC, USA) by using FAN bottles compared to conventional culture methods for the recovery of microorganisms from normally sterile body fluids other than blood and dialysates. Clinically significant pathogens were isolated from 116 (11%) of 1, 099 consecutive specimens (80 from both conventional media and FAN bottles; 23 from FAN bottles only; 13 from conventional media only). Gram-positive cocci were more likely to be recovered from FAN bottles than from conventional media (p = 0.04). Contaminants were also more likely to have grown in FAN bottles (3%) than on conventional media (1%) (p = 0.04). The mean time to detection of significant pathogens was 20.9 h using FAN bottles as compared to 30. 9 h using conventional media (p = 0.0001). These results indicate that the BacT/Alert Microbial Detection System using FAN blood culture bottles improves the yield of clinically significant Gram-positive isolates from normally sterile body fluids with a reduced time to detection.

Surveillance for outbreaks of respiratory tract infections in nursing homes

BACKGROUND

Outbreaks of respiratory tract infections are common in long-term care facilities for older people. The objective of our study was to determine both the frequency of such outbreaks and their clinical and epidemiological features.

METHODS

Prospective surveillance for outbreaks of respiratory tract infections and a retrospective audit of surveillance records were conducted in 5 nursing homes in metropolitan Toronto over 3 years. The clinical manifestations of infected residents were identified and microbiological investigations for causal agents were conducted.

RESULTS

Sixteen outbreaks, involving 480 of 1313 residents, were identified prospectively during 1 144 208 resident-days of surveillance, for an overall rate of 0.42 infections per 1000 resident-days. Another 30 outbreaks, involving 388 residents, were identified retrospectively. Outbreaks occurred year-round, with no seasonal pattern. Pathogens included influenza virus, parainfluenza virus, respiratory syncytial virus, Legionella sainthelensi and Chlamydia pneumoniae. Multiple pathogens were detected in 38% (6/16) of the prospectively identified outbreaks. Of the 480 residents in the prospectively identified outbreaks 398 (83%) had a cough, 194 (40%) had fever and 215 (45%) had coryza. Clinical findings were nonspecific and could not be used to distinguish between causal agents. Pneumonia developed in 72 (15%) of the 480 residents, and 58 (12%) required transfer to hospital. The case-fatality rate was 8% (37/480).

INTERPRETATION

Our findings emphasize the importance of adequate surveillance for outbreaks of respiratory tract infections in nursing homes and of early diagnosis so that appropriate interventions can be promptly instituted.

Cost-effectiveness analysis of six strategies for cardiovascular surgery prophylaxis in patients labeled penicillin allergic

The cost-effectiveness of different approaches to antimicrobial prophylaxis for cardiovascular surgery patients labeled penicillin allergic was studied. A decision-analytic model was used to examine the cost-effectiveness of six strategies for antimicrobial prophylaxis in cardiovascular surgery patients at a tertiary care hospital. The strategies consisted of (1) giving vancomycin to all patients labeled penicillin allergic, (2) giving cefazolin to all patients labeled penicillin allergic, (3) giving vancomycin to all patients with a history suggesting an immunoglobulin E (IgE)-mediated reaction to penicillin and cefazolin to patients without such a history, (4) administering a penicillin skin test to patients with a history suggesting an IgE-mediated reaction to penicillin and giving vancomycin to patients with positive results and cefazolin to all others, (5) skin testing all patients labeled penicillin allergic and giving vancomycin to those with positive results and cefazolin to those with negative results, regardless of history, and (6) skin testing all patients and giving vancomycin to those with positive results or a history suggesting an IgE-mediated reaction to penicillin and cefazolin to all others. Giving cefazolin to all patients labeled penicillin allergic was the least expensive strategy but was associated with the highest rate of both anaphylactic and non-life-threatening serious reactions. Selective use of vancomycin in patients with a history suggesting an IgE-mediated reaction to penicillin was associated with an added cost and a slightly lower rate of anaphylaxis. Although skin-testing strategies may decrease both non-life-threatening and anaphylactic reactions, the incremental cost was high. When vancomycin was given to all patients labeled penicillin allergic, the incremental cost was very high. A decision-analytic model indicated that selective use of vancomycin is more cost-effective than indiscriminate use of vancomycin for surgical prophylaxis in cardiovascular surgery patients labeled penicillin allergic.

A comparison of model-building strategies for lower respiratory tract infection in long-term care

Five strategies for creating predictive models of lower respiratory tract infection in residents of long-term care facilities were compared. A linear judgment model was derived by administering clinical vignettes to physicians who indicated the risk of infection based on the presence or absence of five predictor variables. A model based on physician consensus was created using the same variables. Three models based on empirical data (logistic regression, proportional hazards, and recursive partitioning) were created from a "derivation" sample of data from a cohort study of lower respiratory tract infections in nursing homes using the five predictor variables. All models were applied to a validation set and compared using receiver operating characteristic (ROC) curves. The data-derived and consensus models showed the highest discriminative ability while the linear judgment model showed inferior performance.

Infection in hospitalized trauma patients: incidence, risk factors, and complications

BACKGROUND

Several factors place victims of multiple trauma at increased risk for infection. The purpose of this study was to delineate the frequency of, types of, and risk factors for infection in hospitalized trauma patients.

METHODS

Prospective surveillance for nosocomial infection was conducted for all trauma patients who were admitted for more than 24 hours to a tertiary-care regional trauma center between January 1 and December 31, 1996.

RESULTS

A total of 563 patients (414 males) with a mean age of 40 years (range, 15-97 years) were followed. Most (86%) sustained blunt traumatic injuries. A total of 367 infections occurred in 209 (37%) patients for an incidence of 32.1/1,000 patient-days. The hospital stay of 37% of patients was complicated by at least one infection, involving the following sites: lower respiratory tract (28%), urinary tract (24%), surgical wound (18%), skin/soft tissue (13%), intra-abdominal (5%), primary bloodstream (5%), and other sites (8%). Infection was complicated by septic shock in 36 (10%) cases, acute respiratory distress syndrome in 32 (9%) cases, and multiorgan failure in 13 (4%) cases. Death was attributed to infection in four patients. In a multivariate analysis, infected patients were more likely to have been ventilated (odds ratio [OR] = 2.6; p<0.001), to have had multiple surgical procedures (OR = 2.8; p = 0.02), to have received multiple blood transfusions (OR = 2.3; p = 0.04), and to have had a spinal cord injury (OR = 5.0; p = 0.002). First surgical procedure within 24 hours of admission was protective (OR = 0.4, p = 0.001).

CONCLUSION

Trauma patients are at high risk for developing infection. Identifying patients who are at increased risk for infection may allow for early intervention and subsequent decrease in infectious morbidity.

Synergy testing of vancomycin-resistant Enterococcus faecium against quinupristin-dalfopristin in combination with other antimicrobial agents

Using checkerboard and time-kill assays, we evaluated the in vitro activity of quinupristin-dalfopristin (RP 59500) alone and in combination with five other antimicrobial agents against 12 clinical strains of vancomycin-resistant Enterococcus faecium (VREF). In time-kill studies, six VREF strains exhibited synergism with the combination of quinupristin-dalfopristin and doxycycline and three exhibited synergism with quinupristin-dalfopristin plus ampicillin-sulbactam. Combinations of quinupristin-dalfopristin with these and other agents warrant further clinical evaluation for the treatment of serious VREF infections.

Risk factors for pneumonia and other lower respiratory tract infections in elderly residents of long-term care facilities

BACKGROUND

Little is known about the risk factors, outcome, and impact of pneumonia and other lower respiratory tract infections (LRTIs) in residents of long-term care facilities.

OBJECTIVE

To determine the risk factors and the effect of these infections on functional status and clinical course.

METHODS

Active surveillance for these infections was conducted for 475 residents in 5 nursing homes from July 1, 1993, through June 30, 1996. Information regarding potential risk factors for these infections, functional status, transfers to hospital, and death was also obtained.

RESULTS

Two hundred seventy-two episodes of pneumonia and other LRTIs occurred in 170 residents during 228 757 days of surveillance for an incidence of 1.2 episodes per 1000 resident-days. Multivariable analysis revealed that older age (odds ratio [OR], 1.7; 95% confidence interval [CI], 1.1-2.6 per 10-year interval; P = .01), male sex (OR, 1.9; 95% CI, 1.1-3.5; P = .03), swallowing difficulty (OR, 2.0; 95% CI, 1.2-3.3; P = .01), and the inability to take oral medications (OR, 8.3; 95% CI, 1.4-50.3; P = .02) were significant risk factors for pneumonia; receipt of influenza vaccine (OR, 0.4; 95% CI, 0.3-0.5; P = .01) was protective. Age (OR, 1.6 [95% CI, 1.0-2.5] per 10-year interval; P = .05) and immobility (OR, 2.6; 95% CI, 1.8-3.8; P = .01) were significant risk factors for other LRTIs, and influenza vaccination was protective (OR, 0.3; 95% CI, 0.2-0.4; P = .01). Residents with pneumonia (OR, 0.7; 95% CI, 0.3-1.4; P = .31) or with other LRTIs (OR, 0.5; 95% CI, 0.2-1.1; P = .43) were no more likely to have a deterioration in functional status than individuals in whom infection did not develop.

CONCLUSIONS

Swallowing difficulty and lack of influenza vaccination are important, modifiable risks for pneumonia and other LRTIs in elderly residents of long-term care facilities. Our findings challenge the commonly held belief that pneumonia leads to long-term decline in functional status in this population.

Influenza vaccination in long-term-care facilities: structuring programs for success

OBJECTIVES

To determine which influenza vaccination program characteristics were associated with high resident vaccination rates in Canadian long-term-care facilities (LTCFs).

DESIGN

A cross-sectional survey consisting of a mailed questionnaire conducted in spring 1991.

PARTICIPANTS

All 1,520 Canadian LTCFs for the elderly with at least 25 beds.

RESULTS

The mean overall influenza vaccination rate in the 1,270 (84%) responding facilities was 79%. In multivariate analysis, the variables significantly associated with increased vaccination rates were: a single nonphysician staff person organizing the program, having more program aspects covered by written policies, the offering of vaccine to all residents, a policy of obtaining consent on admission that was durable for future years rather than repeating consent annually, and automatically administering vaccine to residents whose guardians could not be contacted for consent. Any encouragement to staff to be vaccinated had a significant impact on staff vaccination rates.

CONCLUSION

Well-organized influenza vaccination programs increase the influenza vaccination rates of residents in Canadian LTCFs. Facilities need to develop resident vaccination programs further and to focus on vaccinating staff.

Screening high-risk patients for methicillin-resistant Staphylococcus aureus on admission to the hospital: is it cost effective?

OBJECTIVES

To determine the cost-effectiveness of a policy of screening high-risk patients for methicillin-resistant Staphylococcus aureus (MRSA) colonization on admission to hospital.

SETTING

980-bed university-affiliated tertiary-care hospital.

PATIENTS

Between June 1996 and May 1997, patients directly transferred from another hospital or nursing home, or who had been hospitalized in the previous 3 months, were screened for MRSA within 72 hours of hospital admission.

DESIGN

Nasal, perineal, and wound swabs were obtained for MRSA screening using standard laboratory methods. Laboratory and nursing costs associated with screening patients for MRSA on admission to hospital were calculated. The costs associated with the implementation of recommended infection control measures for patients with MRSA also were determined.

RESULTS

3,673 specimens were obtained from 1,743 patients. MRSA was found on admission in 23 patients (1.3%), representing 36% of the 64 patients with MRSA identified in the hospital during the year. MRSA-colonized patients were more likely to have been transferred from a nursing home (odds ratio [OR], 6.4; P =.04) or to have had a previous history of MRSA colonization (OR, 13.1; P =.05). Laboratory and nursing costs were found to be $8.34 per specimen, for a total cost of $30,632 during the year. The average cost of implementing recommended infection control measures for patients colonized with MRSA was approximately $5,235 per patient.

CONCLUSION

If early identification of MRSA in colonized patients prevents nosocomial transmission of the organism to as few as six new patients, the screening program would save money.

Two nursing home outbreaks of respiratory infection with Legionella sainthelensi

OBJECTIVE

To describe outbreaks of infection caused by Legionella sainthelensi occurring in older residents of two nursing homes and to determine risk factors for the development of infection.

DESIGN

Descriptive epidemiology and a case-control study.

SETTING

Two nursing homes (140 beds and 254 beds in nursing homes A and B, respectively) located in southern Ontario, Canada, experiencing outbreaks of respiratory tract infection in July and August 1994.

SUBJECTS

Case-residents of the two nursing homes who met clinical and laboratory criteria for Legionella infection. Control-residents were defined as those who were in the homes during the outbreaks and were asymptomatic.

MEASUREMENTS

Active surveillance was conducted in both nursing homes to identify symptomatic residents. Residents with fever or respiratory tract symptoms had nasopharyngeal swabs taken for viral antigen detection and culture, urine for Legionella antigen detection, and acute and convalescent serology for viruses, Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella. Chest X-rays were performed, and an attempt was made to obtain blood and sputum cultures. Water samples from shower heads, faucets, and air conditioning units were collected for Legionella culture and polymerase chain reaction (PCR) assay. A case-control study was done to assess possible risk factors for legionellosis.

RESULTS

Twenty-nine cases -- 17 in nursing home A; 12 in nursing home B - were identified. Four (14%) case-residents had documented pneumonia and four case-residents died. Univariate analysis revealed that a history of stroke (odds ratio (OR) 2.3 (95% CI, 1.0-5.3)), eating pureed food (OR 4.6 (95% CI, 1.6-12.7)), and having fluids administered with medication (OR 2.5 (95% CI, 1.0-5.9)) were significant risk factors. Cases were less likely to wear dentures (OR .4 (95% CI, .2-.9)) or to eat solid food (OR .3, (95% CI, .1-.6)). Only eating pureed food remained significant in a multivariable analysis (OR 4.6 (95% CI, 1.6-13.0, P = .01)).

CONCLUSION

This report describes outbreaks of legionellosis in two nursing homes, representing the first reported outbreaks of infection caused by Legionella sainthelensi. The association with illness of dietary characteristics indicative of swallowing disorders suggests that aspiration was the most likely mode of infection. The diagnosis of legionellosis should be considered during outbreaks of respiratory infection in nursing homes.

Molecular analysis of the genetic variation among penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae serotypes in Canada

Few studies have examined the genetic relatedness within and between serotypes of Streptococcus pneumoniae. Penicillin-susceptible S. pneumoniae (PSSP) isolates (n=170) and penicillin-resistant S. pneumoniae (PRSP) isolates (n=48) belonging to 13 different serotypes from across Canada were studied to further understand the molecular epidemiology of S. pneumoniae. PRSP of serotypes 6B, 14, and 19F appeared to be novel clones, differentiated by pulsed-field gel electrophoresis from the recognized international penicillin-resistant clones belonging to these serotypes. In addition, not all PRSP strains shared similar genetic backgrounds with PSSP strains of the same serotype, suggesting that in Canada, certain PRSP strains have emerged from new unique lineages of PRSP. Although there was significant heterogeneity among S. pneumoniae of different serotypes, certain serotypes (3, 7F, and 22F) appeared to be more clonally related despite having originated from different geographic regions.

Application of multiplex PCR for detection of non-O157 verocytotoxin-producing Escherichia coli in bloody stools: identification of serogroups O26 and O111

Primers were designed to amplify sequences of verocytotoxin genes and eaeA genes of Escherichia coli O26:H11, O111:H8, and O157:H7 in a multiplex PCR assay. This assay successfully detected E. coli O26:H11 in bloody stool specimens in which other enteric pathogens were not detected by culture-based methods. Rapid assays to detect non-O157:H7 verocytotoxin-producing E. coli is important to improve methods for the etiologic diagnosis of hemorrhagic colitis.

Diagnosis of group A streptococcal necrotizing fasciitis by using PCR to amplify the streptococcal pyrogenic exotoxin B gene

This study evaluated a PCR assay for detection of the streptococcal pyrogenic exotoxin B (speB) gene from tissue biopsy specimens of patients with necrotizing fasciitis. speB was detected in specimens from all 10 patients with necrotizing fasciitis due to group A streptococcus. The assay was negative for all 11 patients without culture or serologic evidence of streptococcal infection. These results suggest that the detection of speB by PCR may be useful for confirming group A streptococcal infection when cultures are negative or not available.

Comparison of six rapid agglutination tests for the identification of Staphylococcus aureus, including methicillin-resistant strains

Six rapid agglutination tests for the identification of Staphylococcus aureus were evaluated by testing 416 strains of staphylococci. The sensitivities and specificities of the tests were as follows: Staphyloslide, 97.7% and 99.3% respectively; Prolex Staph Latex, 96.9% and 93.6%; Staphaurex, 95.4% and 94.2%; Staphaurex Plus, 100% and 93.4%; Slidex Staph Plus, 98.9% and 99.3%; and Staphytect Plus, 99.6% and 88.2%. The three tests utilizing latex particles coated with staphylococcal capsular antibodies were better able to identify methicillin-resistant S. aureus, but only Staphyloslide and Slidex Staph Plus had adequate specificity.

Amphotericin B in lipid emulsion: stability, compatibility, and in vitro antifungal activity

Newer formulations of amphotericin B (AmB) complexed with liposomes or lipid suspensions have been developed. Preliminary studies have suggested that AmB in Intralipid (IL) may be as effective as, but less toxic than, conventional formulations of AmB, but few data are available regarding its stability, compatibility, or in vitro antifungal activity. A compatibility study was done to evaluate the effects of AmB concentrations in IL containing either 10 or 20% soybean oil. The effects of temperature, shaking, and AmB and IL concentrations on the stability of AmB-IL suspensions were analyzed by visual inspection and liquid chromatography. The in vitro antifungal activity of AmB-IL, compared to that of AmB alone against reference strains of Candida species was determined by using a broth macrodilution method in accordance with National Committee for Clinical Laboratory Standards guidelines (M27-T). Samples of AmB-IL which were lightly shaken retained more than 90% of the AmB concentration over 21 days when stored at either 4 or 23 degrees C. Varying the AmB concentration did not appear to affect the stability of AmB-IL. However, a precipitate was formed when mixtures with more than 30% lipid as a proportion of the total volume were centrifuged. AmB-IL and AmB alone had similar in vitro antifungal activities against reference strains of yeasts. Further pharmacologic and clinical studies with AmB-IL are warranted, although AmB should not be combined with IL in concentrations capable of producing a precipitate.

Bacterial meningitis in children and adults. Changes in community-acquired disease may affect patient care

Despite improved understanding of how bacterial meningitis develops, the infection remains a potentially life-threatening emergency capable of causing significant morbidity and mortality. Since the introduction and widespread use of H influenzae type b vaccine in infancy and childhood in North America, the epidemiology of community-acquired bacterial meningitis has changed. S pneumoniae is now the most common cause in children and adults overall, although N meningitidis causes most disease in patients between ages 2 and 18 years. Broad-spectrum cephalosporins (eg, ceftriaxone, cefotaxime) are considered the agents of choice for empirical treatment of bacterial meningitis. However, use of these agents will have to be reconsidered if the incidence of invasive infection from drug-resistant S pneumoniae continues to increase. The role of adjunctive corticosteroid therapy needs to be better defined. Improved conjugate pneumococcal and meningococcal vaccines may soon make bacterial meningitis a preventable disease.

Risk factors, clinical features and outcome of Acinetobacter bacteremia in adults

The medical records of 39 patients with Acinetobacter bacteremia identified in the period between 1985 and 1995 were reviewed. In 24 cases (62%) the bacteremia was considered to have been clinically significant. Most of the infections (79%) were nosocomial, and the majority of these were acquired in an intensive care unit. Ten (42%) patients developed septic shock complicating the bacteremia and 13 (54%) died. In most of these cases (85%), Acinetobacter bacteremia was thought to have caused or contributed to death. The following variables were associated with a greater risk of mortality: age > 65 years (OR = 16; p = 0.01); development of septic shock (OR = 22; p = 0.004); and the presence of coagulopathy (OR = 20; p = 0.03).

Antifungal susceptibility testing of yeast isolates from blood cultures by microbroth dilution and the E test

The results of microbroth dilution were compared with those of the E test for 169 yeast isolates tested for their susceptibility to antifungal agents. All isolates were tested by both methods against amphotericin B, ketoconazole, fluconazole, and itraconazole. The E test results generally correlated well with those obtained by the reference method. There was at least 80% agreement of minimum inhibitory concentration results within two dilutions for all yeast species and agents tested, except for Cryptococcus neoformans tested with fluconazole (8% agreement). The E test appears to be a suitable alternative antifungal susceptibility test method for yeasts, although improvements are required for testing Cryptococcus neoformans against fluconazole.

Mycobacterium xenopi infection in patients with human immunodeficiency virus infection

Mycobacterium xenopi is one of the most frequently isolated nontuberculous mycobacteria in Ontario, Canada. We reviewed the records of 28 human immunodeficiency virus (HIV)-infected patients from whom M. xenopi was isolated between 1982 and 1995. M. xenopi was recovered from respiratory specimens from 24 patients, most of whom had clinical and radiographic evidence of pulmonary disease. However, coexistent pulmonary infection due to other pathogens was found in 17 patients: Pneumocystis carinii (9 patients), cytomegalovirus (5), Haemophilus influenzae (2), Mycobacterium avium complex (2), Streptococcus pneumoniae (1), Staphylococcus aureus (1), Aspergillus species (1), and Histoplasma capsulatum (1). Three patients had bacteremia with M. xenopi, including two patients with pulmonary infection. Two of the bacteremic patients had chronic fever and a wasting syndrome. Twenty-one (75%) of the 28 patients were thought to be colonized, and seven patients (25%; of whom four had CD4 cell counts of < or = 50/mm3) were thought to have significant infection due to M. xenopi. Sixteen patients died, but in no case was death attributable to M. xenopi infection. In a region where M. xenopi is a relatively common mycobacterial isolate, the organism frequently colonizes HIV-infected patients. Significant disease occurs in those patients with more advanced HIV infection.

Investigation of a pseudo-outbreak of Nocardia asteroides infection by pulsed-field gel electrophoresis and randomly amplified polymorphic DNA PCR

Molecular strain typing by pulsed-field gel electrophoresis and by randomly amplified polymorphic DNA analysis was used to investigate a cluster of four Nocardia asteroides isolates associated with the BACTEC 460 TB system. An instrument motor drive misalignment resulted in inadequate needle sterilization and cross-contamination of BACTEC vials. This pseudo-outbreak illustrates the importance of proper BACTEC 460 needle sterilization and maintenance and confirms the usefulness of molecular typing methods for epidemiologic investigations.

Nosocomial Neisseria meningitidis: molecular analysis of a clinical problem

Over a 1-week period, Neisseria meningitidis serogroup B was recovered from two patients in the intensive-care unit (ICU). A cross-infection was presumed when one patient developed invasive meningococcal disease and another patient was found to be colonized. Investigation by molecular typing showed that these cases were not related, demonstrating the value of molecular typing when investigating potential cross-infections in a closed environment such as the ICU.

Antimicrobial susceptibilities of blood culture isolates obtained before and after the introduction of ciprofloxacin

The in-vitro susceptibilities of 1658 blood culture isolates to ciprofloxacin and 13 other antimicrobial agents were determined, and compared with the results for isolates obtained before and after the availability of ciprofloxacin in 1989. Only six (0.6%) of 995 Enterobacteriaceae were resistant to the fluoroquinolones tested; all of the ciprofloxacin-resistant strains were isolated after 1989 (P = 0.04). No significant increase in ciprofloxacin resistance was found in Pseudomonas aeruginosa or Acinetobacter spp. No resistance to ciprofloxacin was found in 124 Staphylococcus aureus isolates prior to 1989, but five (2.4%) of 208 S. aureus strains recovered after 1989 were ciprofloxacin-resistant (P = 0.16). Rates of resistance to ciprofloxacin and other antimicrobial agents commonly used to treat bacteraemic infections have remained relatively low in this Canadian teaching hospital over the past 16 years.

Canadian national survey of prevalence of antimicrobial resistance among clinical isolates of Streptococcus pneumoniae. Canadian Bacterial Surveillance Network

The antimicrobial susceptibilities of 1,089 clinical isolates of Streptococcus pneumoniae obtained from 39 laboratories across Canada between October 1994 and August 1995 were determined. A total of 91 isolates (8.4%) demonstrated intermediate resistance (MIC, 0.1 to 1.0 microgram/ml) and 36 (3.3%) had high-level resistance (MIC, > or = 2.0 micrograms/ml) to penicillin. Penicillin-resistant strains were more likely to have been recovered from normally sterile sites (P = 0.005) and to be cross-resistant to several beta-lactam and non-beta-lactam antimicrobial agents (P < 0.05). These results indicate that there has been a recent significant increase in the prevalence of antibiotic-resistant S. pneumoniae in Canada.