Baldwin Toye

Host and Pathogen Factors for Clostridium difficile Infection and Colonization

BACKGROUND Clostridium difficile infection is the leading cause of health care-associated diarrhea, and the bacterium can also be carried asymptomatically. The objective of this study was to identify host and bacterial factors associated with health care-associated acquisition of C. difficile infection and colonization. METHODS We conducted a 15-month prospective study in six Canadian hospitals in Quebec and Ontario. Demographic information, known risk factors, potential confounding factors, and weekly stool samples or rectal swabs were collected. Pulsed-field gel electrophoresis (PFGE) was performed on C. difficile isolates to determine the genotype. Levels of serum antibodies against C. difficile toxins A and B were measured. RESULTS A total of 4143 patients were included in the study; 117 (2.8%) and 123 (3.0%) had health care-associated C. difficile infection and colonization, respectively. Older age and use of antibiotics and proton-pump inhibitors were significantly associated with health care-associated C. difficile infection. Hospitalization in the previous 2 months; use of chemotherapy, proton-pump inhibitors, and H(2) blockers; and antibodies against toxin B were associated with health care-associated C. difficile colonization. Among patients with health care-associated C. difficile infection and those with colonization, 62.7% and 36.1%, respectively, had the North American PFGE type 1 (NAP1) strain. CONCLUSIONS In this study, health care-associated C. difficile infection and colonization were differentially associated with defined host and pathogen variables. The NAP1 strain was predominant among patients with C. difficile infection, whereas asymptomatic patients were more likely to be colonized with other strains. (Funded by the Consortium de Recherche sur le Clostridium difficile.).

Evaluation of the IDI-MRSA Assay for Detection of Methicillin-Resistant Staphylococcus aureus from Nasal and Rectal Specimens Pooled in a Selective Broth

ABSTRACT Rapid detection of methicillin-resistant Staphylococcus aureus (MRSA) by PCR can be performed directly from nasal specimens with the IDI-MRSA assay. To improve the efficiency of screening, we evaluated the performance of the IDI-MRSA assay for the detection of MRSA from pooled and unpooled specimens cultured in a selective broth. Of the 287 specimens evaluated, 71 were culture and PCR positive, 203 were culture and PCR negative, 3 were culture positive and PCR negative, 8 were culture negative and PCR positive, and 2 remained inhibited. A methicillin-susceptible Staphylococcus aureus isolate was recovered from five of the eight specimens with false-positive PCR results. Compared to the results of culture, the sensitivity, specificity, and negative and positive predictive values of the IDI-MRSA assay for detection of MRSA from broth were 96%, 96%, 90%, and 98%, respectively. Following implementation of the IDI-MRSA assay, PCR-positive broths were subcultured for evaluation of assay performance. Of the 298 IDI-MRSA assay-positive broths, the results for 103 could not be confirmed by culture. A methicillin-susceptible S. aureus (MSSA) isolate was recovered from 77 of these 103 broths. Repeat testing by the IDI-MRSA assay directly with the MSSA isolates confirmed the original positive PCR result. The positive predictive value of the IDI-MRSA assay fell from 90% during the evaluation phase to 65% postimplementation. The IDI-MRSA assay performed well for the detection of MRSA from a selective broth compared to the performance of the detection of MRSA from culture. However, because of the burden associated with implementation of infection control precautions, cultures remain essential in confirming positive IDI-MRSA results.

Prevalence and Mechanisms of Erythromycin Resistance in Group A and Group B Streptococcus: Implications for Reporting Susceptibility Results

ABSTRACT Increased rates of erythromycin resistance among group B Streptococcus (GBS) and group A Streptococcus (GAS) have been reported. Cross-resistance to clindamycin may be present, depending on the mechanism of resistance. We determined the prevalence of macrolide-resistant determinants in GBS and GAS isolates to guide the laboratory reporting of erythromycin and clindamycin susceptibility. Susceptibilities were determined by the disk diffusion and broth microdilution methods. Inducible and constitutive resistance to clindamycin was determined by the double-disk diffusion method. The presence of the ermTR, ermB, and mefA genes was confirmed by PCR. Of the 338 GBS isolates, 55 (17%) were resistant to erythromycin, whereas 26 (8%) were resistant to clindamycin. The erm methylase gene was identified in 48 isolates, 22 of which had inducible resistance to clindamycin and 26 of which had constitutive resistance to clindamycin. The remaining seven resistant isolates had mefA. Of the 593 GAS isolates, 49 (8%) and 6 (1%) isolates were resistant to erythromycin and clindamycin, respectively. Erythromycin resistance was due to mefA in 33 isolates, whereas 14 isolates had erm-mediated resistance (9 isolates had inducible resistance and 5 isolates had constitutive resistance). In our population, erythromycin resistance in GAS was predominantly mediated by mefA and erythromycin resistance in GBS was predominantly mediated by erm. Regional differences in mechanisms of resistance need to be taken into consideration when deciding whether to report clindamycin susceptibility results on the basis of in vitro test results. Testing by the double-disk diffusion method would be an approach that could be used to address this issue, especially for GAS.

High Prevalence of ST131 Isolates Producing CTX-M-15 and CTX-M-14 among Extended-Spectrum-β-Lactamase-Producing Escherichia coli Isolates from Canada

ABSTRACT Phenotypic and genotypic methods were used to characterize extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli isolated in 2007 from 11 different Canadian medical centers. Of the 209 ESBL-producing E. coli isolates tested, 148 (71%) produced CTX-M-15, 17 (8%) produced CTX-M-14, 5 (2%) produced CTX-M-3, and 1 produced CTX-M-27. Overall, 96 (46%) of the ESBL producers belonged to clonal complex ST131, with the highest prevalence in Brampton, Calgary, and Winnipeg. ST131 is an important cause of community onset urinary tract infections due to ESBL-producing E. coli across Canada.

Collagen and glycopolymer based hydrogel for potential corneal application.

6-Methacryloyl-alpha-D-galactopyranose (MG) was synthesized, and characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectrometry, and single-crystal X-ray diffraction. A series of interpenetrating polymer network (IPN) hydrogels was fabricated by simultaneously photocuring MG crosslinked by poly(ethylene glycol) diacrylate and chemically crosslinking type I collagen with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. The successful incorporation of the glycopolymer, polymer MG, into collagen hydrogel was confirmed by FTIR and solid-state (13)C NMR. The optical characteristics of the IPN hydrogels are comparable to those of human corneas. The tensile strength and modulus of the hydrogels are enhanced by incorporation of polymer MG in comparison to that of the control collagen hydrogel. Biodegradation results indicated that polymer MG enhanced the stability of the composite hydrogels against collagenase. In vitro results demonstrated that the IPN hydrogel supported the adhesion and proliferation of human corneal epithelial cells and outperformed human cornea in blocking bacteria adhesion. Taken together, the IPN hydrogel might be a promising material for use in corneal lamellar keratoplasty.

The presence of serum antibody to the chlamydial heat shock protein (CHSP60) as a diagnostic test for tubal factor infertility

OBJECTIVE To study the utility of testing for heat shock protein 60 (CHSP60) antibodies in the diagnosis of tubal factor infertility. DESIGN Prospective case control. SETTING Canadian university hospital infertility clinic. PATIENT(S) Women presenting for infertility investigation. INTERVENTION(S) Sera were collected from 77 patients. MAIN OUTCOME MEASURE(S) The relationship between tubal factor infertility and the presence of antibodies to Chlamydia trachomatis and CHSP60 was assessed. RESULT(S) There were no significant differences between antibodies to C. trachomatis in women with tubal factor infertility (63%) and other causes of infertility (46%). However, more women with tubal factor infertility (44%) had anti-CHSP60 antibodies compared with other causes of infertility (8%). Antibody testing for C. trachomatis has only a 63% sensitivity and a 54% specificity for detecting tubal factor infertility. In contrast, the CHSP60 antibody test has a 44% sensitivity and a 92% specificity for detecting tubal factor infertility. There is a good positive likelihood ratio of 5.5 for CHSP60 antibody testing detecting the presence of tubal factor infertility. Combining CHSP60 antibody with antibody testing for C. trachomatis has an excellent positive likelihood ratio of 10 for the detection of C. trachomatis-associated tubal factor infertility. CONCLUSION(S) CHSP60 antibody testing is a more accurate test than antibody testing for C. trachomatis for predicting chlamydia-associated tubal factor infertility. These tests, when used in combination at initial infertility evaluation, would provide a rapid noninterventive means of diagnosing tubal factor infertility.

Cloxacillin versus vancomycin for presumed late-onset sepsis in the Neonatal Intensive Care Unit and the impact upon outcome of coagulase negative staphylococcal bacteremia: a retrospective cohort study

BackgroundCoagulase negative staphylococcus (CONS) is the main cause of late-onset sepsis in Neonatal Intensive Care Units (NICU). Although CONS rarely causes fulminant sepsis, vancomycin is frequently used as empiric therapy. Indiscriminate use of vancomycin has been linked to the emergence of vancomycin resistant organisms. The objective of this study was to compare duration of CONS sepsis and mortality before and after implementation of a policy of selective vancomycin use and compare use of vancomycin between the 2 time periods.MethodsA retrospective study was conducted of infants ≥4 days old, experiencing signs of sepsis with a first positive blood culture for CONS, during two 12-month periods. Late-onset sepsis was treated empirically with vancomycin and gentamicin during period 1, and cloxacillin and gentamicin during period 2. The confidence interval method was used to assess non-inferiority of the outcomes between the two study groups.ResultsThere were 45 episodes of CONS sepsis during period 1 and 37 during period 2. Duration of sepsis was similar between periods (hazard ratio of 1.00, 95%CI: 0.64, 1.57). One death during period 2 was possibly related to CONS sepsis versus none in period 1. Vancomycin was used in 97.8% of episodes in period 1 versus 81.1% of episodes in period 2.ConclusionAlthough we failed to show non-inferiority of duration of sepsis in the cloxacillin and gentamicin group compared to the vancomycin and gentamicin group, duration of sepsis was clinically similar. Restricting vancomycin for confirmed cases of CONS sepsis resistant to oxacillin appears effective and safe, and significantly reduces vancomycin use in the NICU.

Detection of Plasmid-Mediated KPC-Producing Klebsiella pneumoniae in Ottawa, Canada: Evidence of Intrahospital Transmission

ABSTRACT Klebsiella pneumoniae isolates from three patients admitted to the Ottawa Hospital, a 1,040-bed teaching hospital, were found to contain the plasmid-borne K. pneumoniae carbapenemase (KPC)-producing bla gene (blaKPC). There was evidence of person-to-person transmission for two patients. Screening of 186 clinical isolates revealed no additional blaKPC-containing isolates.

Surveillance for hospital outbreaks of invasive group a streptococcal infections in Ontario, Canada, 1992 to 2000.

Context Hospital outbreaks of invasive group A streptococcal infection are a potentially preventable source of morbidity and mortality. Contribution In Ontario, Canada, 291 cases of hospital-acquired invasive group A infection occurred between 1992 and 2000; 10% of these infections occurred during 20 outbreaks in the hospital. Although nosocomial infections were most common in surgical and obstetric patients, most outbreaks of streptococcus A infection occurred outside of those settings. One quarter of the outbreaks was related to community-acquired infections (mostly necrotizing fasciitis) requiring intensive care; the bacteria were primarily transmitted from patient to patient. Implication Isolation of patients with necrotizing fasciitis may be an important strategy to reduce hospital outbreaks of invasive group A streptococcal infection. The Editors Streptococcus pyogenes has the capacity to produce myriad invasive diseases, the most dramatic being necrotizing fasciitis and streptococcal toxic shock syndrome (1). The rate of invasive disease has increased in recent decades to more than 3 per 100000 persons per year, and the case-fatality rate remains approximately 15% (2, 3). Equally as dramatic as the illness that group A streptococcus produces in individual patients are the outbreaks it has caused in hospitals (463). Such outbreaks have involved as many as 56 patients and health care workers and have continued for as long as 3 years (32, 39). Preventing hospital transmission of group A streptococcal infection would allow for the prevention of many secondary cases of disease (64). The current Centers for Disease Control and Prevention (CDC) recommendations for preventing nosocomial outbreaks exist only for postpartum and postsurgical settings and are based on expert opinion and a review of a limited number of outbreaks (6, 28, 32, 41, 55, 58, 65). This study sought to describe the epidemiology of hospital outbreaks of invasive group A streptococcal disease in Ontario, Canada, in order to assess the utility of proposed strategies for the prevention, investigation, and management of clusters of this disease (66). Methods Surveillance Prospective, population-based surveillance of all invasive group A streptococcal infections was conducted in the province of Ontario, Canada, from 1 January 1992 to 31 December 2000, as described elsewhere (2, 3). All Ontario microbiology laboratories processing sterile-site specimens telephoned the central study office whenever group A streptococcus was identified from a specimen from any sterile site. Annual audits were performed in all laboratories to ensure complete case ascertainment. Case definitions are described elsewhere (3). Invasive group A streptococcal infection was defined as illness associated with isolation of group A streptococcus from a normally sterile body site. Infections were deemed hospital acquired if disease was neither present nor incubating at the time of admission (67). The Ontario Group A Streptococcal surveillance system was approved by the institutional review boards of the University of Toronto and participating hospitals. Investigation of Disease Transmission When a nosocomial case of group A streptococcus was identified, study staff contacted the hospitals infection control practitioner to offer recommendations regarding investigation. Recommendations included 1) case finding in hospital patients, staff, and family members; 2) screening close contacts of the patient for symptoms of group A streptococcal infection; 3) taking additional precautions or restricting work for acutely ill contacts; 4) obtaining throat swabs and considering vaginal and rectal swabs from contacts for group A streptococcal culture; and 5) typing any isolates obtained. An outbreak was defined as the occurrence of at least 2 cases of culture-confirmed, symptomatic infection that were epidemiologically linked and were caused by isolates of the same M and T type and were indistinguishable by pulsed-field gel electrophoresis (3). Study staff were available for consultation during these investigations, and typing of isolates was provided by the study. Laboratory Methods Clinical isolates were identified as S. pyogenes using standard methods. Both M serotyping and T agglutination typing were performed at the Canadian National Centre for Streptococcus, Edmonton, Alberta, Canada (6870). Pulsed-field gel electrophoresis was performed as described elsewhere (71). Statistical Analysis Surveillance data were entered in duplicate and were analyzed in SAS for Windows, version 8 (SAS Institute, Cary, North Carolina). Differences in proportions were assessed by using Fisher exact tests, and differences in continuous variables were evaluated by using Wilcoxon rank-sum tests. Role of the Funding Sources Surveillance was funded by the CDC and by the Department of Microbiology at the Mount Sinai Hospital. These funding sources contributed to the design of surveillance but had no influence on the conduct or reporting of this study or the decision to submit the manuscript for publication. Results In prospective surveillance from 1 January 1992 to 31 December 2000, 2351 cases of invasive group A streptococcal disease were detected in Ontario (3) (Table 1). Of the 291 nosocomial invasive group A streptococcal infections, 29 (10%) were associated with 20 outbreaks. These 20 nosocomial outbreaks also involved 26 laboratory-confirmed noninvasive group A streptococcal illnesses, for a total of 53 outbreak-associated patient cases (there were 6 cases in health care workers, all pharyngitis). The average rate of outbreaks over the 9-year period was 1.0 per 100 hospitals per year, with an average rate of outbreak-associated disease of 0.5 per 100000 hospital admissions per year. Table 1. Characteristics of Invasive Group A Streptococcal Disease Cases in Ontario, 19922000 The clinical presentations of the 29 invasive cases associated with outbreaks did not differ from those of all invasive disease cases (data not shown). The case-fatality rate of outbreak-associated invasive cases (24% [7 of 29]) did not statistically significantly differ from that of all cases of invasive infection (16% [347 of 2242]; P= 0.20) or that of sporadic nosocomial infections (17% [42 of 255]; P> 0.2). Table 2 details the characteristics of the 20 nosocomial outbreaks. The outbreaks were distributed evenly over time and occurred in 15 institutions. Five (25%) outbreaks included at least 1 surgical site infection; 6 (30%) included at least 1 postpartum infection; and 14 (70%) included at least 1 nonsurgical, nonobstetric infection. Five (25%) outbreaks involved a mix of 2 or more case types. Nonsurgical, nonobstetric infections encompassed a broad range of syndromes, including primary bacteremia (5 cases), soft-tissue infection (5 cases), pneumonia (4 cases), pharyngitis (2 cases), and peritonitis (1 case). Table 2. Nosocomial Outbreaks of Group A Streptococcal Infection Identified via Prospective Surveillance in Ontario, 19922000 In 5 (25%) outbreaks, transmission was initiated by admission of a patient with community-acquired invasive group A streptococcal infection. All community-acquired index cases involved necrotizing fasciitis or a draining soft-tissue infection, and 4 of the 5 patients were admitted directly to an intensive care unit. Outbreak initiation and propagation were rapid, with a median interval between first and second cases of 4.5 days (range, 0 to 30 days) and a median interval between any 2 subsequent cases of 2 days (range, 0 to 11 days). Fourteen outbreaks (70%) involved only 2 cases. The largest outbreak involved 10 cases: 6 health care workers and 4 patients. Only 2 (10%) outbreaks lasted more than 2 weeks, and none lasted more than 1 month. The most common mode of outbreak propagation was patient-to-patient transmission (via a person or the environment), judged as primarily responsible for 12 (60%) outbreaks. Transmission from a staff carrier was the sole source of transmission in 1 (5%) outbreak, mixed patient-to-patient transmission and staff transmission contributed to 1 (5%) outbreak, and in 1 (5%) outbreak it could not be determined whether transmission occurred from a staff carrier or by patient-to-patient spread. The mode of propagation could not be ascertained in the remaining 5 (25%) outbreaks. Transmission via the inanimate environment was suspected in 2 situations. One patient developed group A streptococcal pneumonia 2 days after being admitted to the intensive care unit room and bed of a patient who had died of necrotizing fasciitis. No staff had contact with both patients. Another patient developed a postoperative surgical site infection 24 hours after having a biopsy in an operating room in which the previous procedure (completed 6 hours before) was debridement of necrotizing fasciitis. Again, no staff had contact with both patients. In 3 of the 11 (26%) remaining outbreaks thought to be propagated from patient to patient, roommates of index patients developed acute infection. The staff carrier implicated as a sole source was a colonized surgeon linked to 3 surgical site infections over a 10-day period. One colonized obstetrician was probably responsible for propagation of 2 of 3 secondary cases of postpartum disease in another outbreak, and 1 colonized nurse may have been responsible for propagation to 2 patients on a medical ward in a third outbreak. In 5 of 10 (46%) other investigated outbreaks, at least 1 colonized or infected staff person was identified; in all cases, a health care worker may have transmitted S. pyogenes to 1, but not more than 1, of the outbreak-associated cases. Although a staff carrier was the primary mode of transmission in only 2 (10%) outbreaks, 1 or more health care workers were colonized with the outbreak strain in 6 of 18 (33%) other outbreaks. In 5 outbreaks (25%), health care workers who were screened were colonized with nonoutbreak strains. In outbreaks

The use of a bacteria detection system to evaluate bacterial contamination in PLT concentrates

BACKGROUND: Random‐donor PLTs (RDPs) are functional at 7 days. Nevertheless, since the mid‐1980s, concern for bacterial contamination has caused the storage period to be reduced to 5 days. The ability of a bacteria detection system (BDS, Pall) to determine bacterial contamination and permit extension of the PLT shelf life to 7 days was assessed.