Search PubMed⌕ Search

Biomedical subjects

Allison McGeer

Publications and source records attributed to Allison McGeer.

At least 37 records · Page 2Linked to original sources
PubMed2005

Identification of a progenitor of the CTX-M-9 group of extended-spectrum beta-lactamases from Kluyvera georgiana isolated in Guyana.

Chromosomal beta-lactamase genes (bla(KLUY)) from six Kluyvera georgiana strains isolated in Guyana were cloned and expressed in Escherichia coli. KLUY-1 exhibited 100% amino acid identity with the extended-spectrum beta-lactamase CTX-M-14. We also show that a 2.7-kb Kluyvera chromosomal region exhibits 99% nucleotide identity to a portion of In60 that includes bla(CTX-M-9).

Amino Acid Sequence↗
PubMed2005

Mosaic prophages with horizontally acquired genes account for the emergence and diversification of the globally disseminated M1T1 clone of Streptococcus pyogenes.

The recrudescence of severe invasive group A streptococcal (GAS) diseases has been associated with relatively few strains, including the M1T1 subclone that has shown an unprecedented global spread and prevalence and high virulence in susceptible hosts. To understand its unusual epidemiology, we aimed to identify unique genomic features that differentiate it from the fully sequenced M1 SF370 strain. We constructed DNA microarrays from an M1T1 shotgun library and, using differential hybridization, we found that both M1 strains are 95% identical and that the 5% unique M1T1 clone sequences more closely resemble sequences found in the M3 strain, which is also associated with severe disease. Careful analysis of these unique sequences revealed three unique prophages that we named M1T1.X, M1T1.Y, and M1T1.Z. While M1T1.Y is similar to phage 370.3 of the M1-SF370 strain, M1T1.X and M1T1.Z are novel and encode the toxins SpeA2 and Sda1, respectively. The genomes of these prophages are highly mosaic, with different segments being related to distinct streptococcal phages, suggesting that GAS phages continue to exchange genetic material. Bioinformatic and phylogenetic analyses revealed a highly conserved open reading frame (ORF) adjacent to the toxins in 18 of the 21 toxin-carrying GAS prophages. We named this ORF paratox, determined its allelic distribution among different phages, and found linkage disequilibrium between particular paratox alleles and specific toxin genes, suggesting that they may move as a single cassette. Based on the conservation of paratox and other genes flanking the toxins, we propose a recombination-based model for toxin dissemination among prophages. We also provide evidence that a minor population of the M1T1 clonal isolates have exchanged their virulence module on phage M1T1.Y, replacing it with a different module identical to that found on a related M3 phage. Taken together, the data demonstrate that mosaicism of the GAS prophages has contributed to the emergence and diversification of the M1T1 subclone.

Amino Acid Sequence↗
PubMed2005

Use of a selective enrichment broth to recover Clostridium difficile from stool swabs stored under different conditions.

The recovery of Clostridium difficile from the stools of patients with C. difficile-associated diarrhea was evaluated by use of an enrichment broth (cycloserine-cefoxitin fructose broth supplemented with 0.1% sodium taurocholate [TCCFB]) and was compared to that from selective agar (cycloserine-cefoxitin fructose agar [CCFA]) and alcohol shock followed by inoculation onto blood agar (AS-BA). TCCFB was superior to CCFA and AS-BA, and neither the storage time nor the storage temperature affected the recovery rate.

Bacteriological Techniques↗
PubMed2005

Patient contact recall after SARS exposure.

We reinterviewed healthcare workers who had been exposed to a patient with severe acute respiratory syndrome (SARS) in an intensive care unit to evaluate the effect of time on recall reliability and willingness to report contact activities and infection control precautions. Healthcare workers reliably recalled events 6 months after exposure.

Adult↗
PubMed2005

Risk factors for pediatric invasive group A streptococcal disease.

Invasive group A Streptococcus (GAS) infections can be fatal and can occur in healthy children. A case-control study identified factors associated with pediatric disease. Case-patients were identified when Streptococcus pyogenes was isolated from a normally sterile site, and matched controls (>or=2) were identified by using sequential-digit dialing. All participants were noninstitutionalized surveillance-area residents <18 years of age. Conditional regression identified factors associated with invasive disease: other children living in the home (odds ratio [OR]=16.85, p=0.0002) and new use of nonsteroidal antiinflammatory drugs (OR=10.64, p=0.005) were associated with increased risk. More rooms in the home (OR=0.67, p=0.03) and household member(s) with runny nose (OR=0.09, p=0.002) were associated with decreased risk. Among children, household-level characteristics that influence exposure to GAS most affect development of invasive disease.

Adolescent↗
PubMed2004

Health care workers and the initiation of treatment for latent tuberculosis infection.

BACKGROUND: Despite strong evidence and recommendations supporting the treatment of latent tuberculosis infection, many affected health care workers at risk of acquiring tuberculosis from and potentially transmitting tuberculosis to their patients do not receive treatment. The objective of this study was to determine whether health care workers were less likely than non-health care workers to initiate treatment for latent tuberculosis infection. METHODS: In this retrospective cohort study that used the disease management database from a specialized downtown Toronto tuberculosis clinic, patients with latent tuberculosis infection were included if they had risk factors for progression of disease and were excluded if they had contraindications to treatment. RESULTS: Our final cohort consisted of 308 patients with latent tuberculosis infection. The overall treatment initiation rate was 58%. We found that, when a number of confounding variables, including age, foreign birth, contact with persons with active tuberculosis, tuberculosis skin test conversion, bacille Calmette-Guérin vaccination, abnormal chest radiograph findings, comorbidities, and income, were considered and/or controlled for, the odds of a health care worker initiating treatment were approximately one-half of those of a non-health care worker (adjusted odds ratio, 0.55; 95% confidence interval, 0.32-0.93). CONCLUSION: We conclude that, in our clinic, health care workers are less likely than non-health care workers to initiate treatment for latent tuberculosis infection.

Adult↗
PubMed2004

Genome-wide molecular dissection of serotype M3 group A Streptococcus strains causing two epidemics of invasive infections.

Molecular factors that contribute to the emergence of new virulent bacterial subclones and epidemics are poorly understood. We hypothesized that analysis of a population-based strain sample of serotype M3 group A Streptococcus (GAS) recovered from patients with invasive infection by using genome-wide investigative methods would provide new insight into this fundamental infectious disease problem. Serotype M3 GAS strains (n = 255) cultured from patients in Ontario, Canada, over 11 years and representing two distinct infection peaks were studied. Genetic diversity was indexed by pulsed-field gel electrophoresis, DNA-DNA microarray, whole-genome PCR scanning, prophage genotyping, targeted gene sequencing, and single-nucleotide polymorphism genotyping. All variation in gene content was attributable to acquisition or loss of prophages, a molecular process that generated unique combinations of proven or putative virulence genes. Distinct serotype M3 genotypes experienced rapid population expansion and caused infections that differed significantly in character and severity. Molecular genetic analysis, combined with immunologic studies, implicated a 4-aa duplication in the extreme N terminus of M protein as a factor contributing to an epidemic wave of serotype M3 invasive infections. This finding has implications for GAS vaccine research. Genome-wide analysis of population-based strain samples cultured from clinically well defined patients is crucial for understanding the molecular events underlying bacterial epidemics.

Antigens, Bacterial↗
PubMed2004

Interpretation of diagnostic laboratory tests for severe acute respiratory syndrome: the Toronto experience.

BACKGROUND: An outbreak of severe acute respiratory syndrome (SARS) began in Canada in February 2003. The initial diagnosis of SARS was based on clinical and epidemiological criteria. During the outbreak, molecular and serologic tests for the SARS-associated coronavirus (SARS-CoV) became available. However, without a "gold standard," it was impossible to determine the usefulness of these tests. We describe how these tests were used during the first phase of the SARS outbreak in Toronto and offer some recommendations that may be useful if SARS returns. METHODS: We examined the results of all diagnostic laboratory tests used in 117 patients admitted to hospitals in Toronto who met the Health Canada criteria for suspect or probable SARS. Focusing on tests for SARS-CoV, we attempted to determine the optimal specimen types and timing of specimen collection. RESULTS: Diagnostic test results for SARS-CoV were available for 110 of the 117 patients. SARS-CoV was detected by means of reverse-transcriptase polymerase chain reaction (RT-PCR) in at least one specimen in 59 (54.1%) of 109 patients. Serologic test results of convalescent samples were positive in 50 (96.2%) of 52 patients for whom paired serum samples were collected during the acute and convalescent phases of the illness. Of the 110 patients, 78 (70.9%) had specimens that tested positive by means of RT-PCR, serologic testing or both methods. The proportion of RT-PCR test results that were positive was similar between patients who met the criteria for suspect SARS (50.8%, 95% confidence interval [CI] 38.4%-63.2%) and those who met the criteria for probable SARS (58.0%, 95% CI 44.2%-70.7%). SARS-CoV was detected in nasopharyngeal swabs in 33 (32.4%) of 102 patients, in stool specimens in 19 (63.3%) of 30 patients, and in specimens from the lower respiratory tract in 10 (58.8%) of 17 patients. INTERPRETATION: These findings suggest that the rapid diagnostic tests in use at the time of the initial outbreak lack sufficient sensitivity to be used clinically to rule out SARS. As tests for SARS-CoV continue to be optimized, evaluation of the clinical presentation and elucidation of a contact history must remain the cornerstone of SARS diagnosis. In patients with SARS, specimens taken from the lower respiratory tract and stool samples test positive by means of RT-PCR more often than do samples taken from other areas.

Adolescent↗
PubMed2004

Facility-level correlates of antimicrobial use in nursing homes.

We assessed the contribution of facility-level variables to antimicrobial use in a cohort of 50 nursing homes and found that antimicrobial use was significantly correlated with the percentage of nursing home residents with feeding tubes, the number of healthcare aides, and the country of origin of the facility.

Anti-Infective Agents↗
PubMed2004

Patterns of handwashing behavior and visits to patients on a general medical ward of healthcare workers.

OBJECTIVE: To obtain accurate data regarding the handwashing behavior and patterns of visits to patients by healthcare workers (HCWs). METHODS: All visits by HCWs to selected patient rooms were recorded for 3 days and 2 nights. Additionally, 5 nurses were observed for 1 day each and 2 nurses were observed for 1 night each. Nurses were observed for their entire shifts and all of their activities were recorded. SETTING: A general medical ward in a tertiary-care hospital. PARTICIPANTS: Convenience samples of HCWs and patients. RESULTS: Patients were visited every 25 minutes on average. Monitoring rooms and observing nurses resulted in similar rates of patient visits. The highest level of risk was contact with body fluids in 11% of visits and skin in 40% of visits. The overall rate of handwashing was 46%; however, the rate was higher for visits involving contact with body fluids (81%) and skin (61%). Nurses returned immediately to the same patient 45% of the time. The rate of handwashing was higher for the last of a series of visits to a patient's room (53% vs 30%, P < .0001). CONCLUSIONS: Nurses adjusted their handwashing rates in accordance with the risk level of each visit. Monitoring patient rooms and observing nurses yielded similar estimates of patient visits and proportions of visits involving contact with skin or body fluids. Education programs about hand hygiene may be more effective if patterns of care and levels of risk are incorporated into recommendations.

Body Fluids↗
PubMed2004

Nutrition risk factors for survival in the elderly living in Canadian long-term care facilities.

OBJECTIVES: To determine the role of nutritional parameters in influencing the risk of mortality in institutionalized elderly. DESIGN: A prospective cohort study in which subjects had several nutritional parameters measured at baseline and were followed for 19 months. Time to death and mortality were recorded starting immediately after enrollment. SETTING: Fourteen long-term care facilities (LTCFs). PARTICIPANTS: Four hundred eight elderly long-term care residents aged 60 and older who resided in the facility for more than 6 weeks. MEASUREMENTS: At baseline, knee height, weight, mid-arm circumference (MAC), skin-fold thickness, and fat-free mass using bioelectric impedance analysis were measured. Covariates included demographic factors, length of stay in the facility, functional status, and medical diagnoses. Cox proportional hazards regression analysis was used to identify independent predictors of mortality. Results are reported as mean+/-standard error of the mean (SEM). RESULTS: Overall, mortality rate was 28.4%. Univariate predictors included male sex, body mass index, MAC, and triceps skin fold. In multivariate analysis, male sex (hazard ratio (HR)=1.7, 95% confidence interval (CI)=1.2-2.7, P=.0096) and MAC less than 26 cm were significantly associated with increased risk of mortality (HR=4.8, 95% CI: 2.8-8.3, P<.0001). CONCLUSION: Among this elderly population living in LTCFs, MAC is the best nutritional predictor of mortality.

Aged↗
PubMed2004

Complete nucleotide sequence of a 92-kilobase plasmid harboring the CTX-M-15 extended-spectrum beta-lactamase involved in an outbreak in long-term-care facilities in Toronto, Canada.

A major outbreak involving an Escherichia coli strain that was resistant to expanded-spectrum cephalosporins occurred in Toronto and surrounding regions in 2000 to 2002. We report the complete sequence of a plasmid, pC15-1a, that was found associated with the outbreak strain. Plasmid pC15-1a is a circular molecule of 92,353 bp consisting of two distinct regions. The first is a 64-kb region that is essentially homologous to the non-R-determinant region of plasmid R100 except for several point mutations, a few small insertions and deletions, and the absence of Tn10. The second is a 28.4-kb multidrug resistance region (MDR) that has replaced the R-determinant region of the R100 progenitor and consists mostly of transposons or partial transposons and five copies of the insertion element IS26. All drug resistance genes found in pC15-1a, including the beta-lactamase genes bla(CTX-M-15), bla(OXA-1), and bla(TEM-1), the tetracycline resistance gene tetA, and aminoglycoside resistance genes aac(6')-Ib and aac(3)-II, are located in the MDR. The bla(CTX-M-15) gene was found downstream of ISEcp1as part of a transposition unit, as determined from the surrounding sequence. Examination of the plasmids from CTX-M-15-harboring strains isolated from hospitals across Canada showed that pC15-1a was found in several strains isolated from a site in western Canada. Comparison of pC15-1a and pCTX15, found in an E. coli strain isolated in India in 1999, revealed that the plasmids had several features in common, including an R100 backbone and several of the resistance genes, including bla(CTX-M-15), bla(TEM-1), bla(OXA-1), tetA, and aac(6')-Ib.

Base Sequence↗
PubMed2004

In vitro antimicrobial susceptibilities of Streptococcus pneumoniae clinical isolates obtained in Canada in 2002.

Empirical treatment is best guided by current surveillance of local resistance patterns. The goal of this study is to characterize the prevalence of antimicrobial nonsusceptibility within pneumococcal isolates from Canada. The Canadian Bacterial Surveillance Network is comprised of laboratories from across Canada. Laboratories collected a defined number of consecutive clinical and all sterile site isolates of S. pneumoniae in 2002. In vitro susceptibility testing was performed by broth microdilution with NCCLS guidelines. Rates of nonsusceptibility were compared to previously published reports from the same network. A total of 2,539 isolates were tested. Penicillin nonsusceptibility increased to 15% (8.5% intermediate, 6.5% resistant) compared to 12.4% in 2000 (P < or = 0.025, chi(2)). Only 32 (1.3%) isolates had an amoxicillin MIC of > or = 4 microg/ml and only 2 of 32 cerebrospinal fluid isolates had an intermediate susceptibility to ceftriaxone by meningeal interpretive criteria (MIC = 1 microg/ml). A total of 354 (13.9%) isolates were macrolide nonsusceptible (46.3% MLS(B), 56.7% M phenotype), increasing from 11.4% in 2000 (P < or = 0.0075, chi(2)). Only 13 (<1%) isolates had a telithromycin MIC of >1 microg/ml. Ciprofloxacin nonsusceptibility (defined as an MIC of > or = 4 microg/ml) increased to 2.7% compared to 1.4% in 2000 (P < or = 0.0025, chi(2)) and was primarily found in persons > or =18 years old (98.5%). Nonsusceptibility to penicillin, macrolides, and fluoroquinolones is increasing in Canada. Nonsusceptibility to amoxicillin and ceftriaxone remains uncommon. Newer antimicrobials such as telithromycin and respiratory fluoroquinolones have excellent in vitro activity.

Adolescent↗