Time filter

Source Type

Bells Corners, Canada

Pightling A.W.,U.S. Food and Drug Administration | Petronella N.,Bureau of Food Surveillance and Science Integration | Pagotto F.,Microbiology Research Division
BMC Research Notes | Year: 2015

Background: The influences that different programs and conditions have on error rates of single-nucleotide polymorphism (SNP) analyses are poorly understood. Using Illumina short-read sequence data generated from Listeria monocytogenes strain HPB5622, we assessed the performance of four SNP callers (BCFtools, FreeBayes, UnifiedGenotyper, VarScan) under a variety of conditions, including: (1) a range of sequencing coverages; (2) use of four popular reference-guided assemblers (Burrows-Wheeler Aligner, Novoalign, MOSAIK, SMALT); (3) with and without read quality trimming and filtering; and (4) use of different reference sequences. Results: At 8-fold coverage the proportions of true positive calls ranged from 0.22 to 25.00 % when reads were aligned to a nearly identical reference (0.000096 % distant). Calls made when reads were aligned to a non-identical reference (0.85 % distant) were from 92.54 to 98.88 % accurate. At 79-fold coverage accuracies ranged from 3.95 to 20.00 % with the nearly identical reference and 93.80-98.75 % with the non-identical reference. Read preprocessing significantly changed the numbers of false positive calls made, from a 65.24 % decrease to a 54.55 % increase. Conclusions: The combinations of reference-guided sequence assemblers and SNP callers greatly influenced not only the numbers of true and false positive sites but also the proportions of true positive calls relative to the total numbers of calls made. Furthermore, the efficacy of different assembler and caller combinations changed dramatically with the different conditions tested. Researchers should consider whether identifying the greatest numbers of true positive sites, reducing the numbers of false positive calls, or achieving the highest accuracies are desired. © 2015 Pightling et al. Source

Budu-Amoako E.,University of Prince Edward Island | Greenwood S.J.,University of Prince Edward Island | Dixon B.R.,Microbiology Research Division | Sweet L.,University of Prince Edward Island | And 3 more authors.
Zoonoses and Public Health | Year: 2012

To determine the zoonotic potential of Cryptosporidium and Giardia in Prince Edward Island (PEI), Canada, 658 human faecal specimens were screened that were submitted to the Queen Elizabeth Hospital diagnostic laboratory. Overall, 143 (22%) samples were Cryptosporidium positive, while three (0.5%) were positive for Giardia. Successful genotyping of 25 Cryptosporidium isolates by sequence analysis of the HSP70 gene revealed that 28 and 72% were C. hominis and C. parvum, respectively. Cryptosporidium isolates from humans and previously genotyped C. parvum from beef cattle were subtyped by sequence analysis of the GP60 gene. Subtyping identified three subtypes belonging to the family IIa. All three subtypes IIaA16G2RI (55%), IIaA16G3RI (22%) and IIaA15G2RI (22%) were found in the animal isolates, while two of the subtypes found in the animals, IIaA16G2RI (80%) and IIaA15G2RI (20%), were also identified in the human isolates. Cryptosporidium infection in humans peaked in April-June. Molecular epidemiological analysis of the human data showed a C. parvum peak in the spring and a relatively smaller peak for C. hominis in July-September. The majority (57%) of human Cryptosporidium isolates were found in children between 5 and 10years of age. All three Giardia isolates were identified as G. duodenalis assemblage A. The overall Cryptosporidium prevalence in our human samples was high relative to other studies, but because the samples were submitted to a hospital diagnostic laboratory, the results may not be representative of the general population. Further, the presence of the same zoonotic C. parvum subtypes in cattle and human isolates implies that transmission is largely zoonotic and cattle may be a source of sporadic human infections on PEI. The presence of Giardia in people on PEI is rare, and the assemblage A found in humans might originate from humans, livestock or other domestic or wild animals. © 2012 Blackwell Verlag GmbH. Source

Waturangi D.E.,Atma Jaya Catholic University of Indonesia | Pradita N.,Atma Jaya Catholic University of Indonesia | Linarta J.,Atma Jaya Catholic University of Indonesia | Banerjee S.,Microbiology Research Division
Journal of Food Protection | Year: 2012

Vibrio cholerae is well recognized as the causative agent of cholera, an acute intestinal infection characterized by watery diarrhea that may lead to dehydration and death in some cases. V. cholerae is a natural inhabitant of the aquatic environment in the tropical regions. Jakarta has the highest percentage of individuals affected by sporadic diarrheal illness compared with other areas in Indonesia. Inadequate safety measures for drinking water supplies, improper sanitation, and poor hygiene can increase the risk of cholera outbreaks. Few studies have been conducted on the prevalence of these bacteria in ice and beverages that are popularly sold and consumed in Jakarta. In this study, we detected and quantified V. cholerae from ice and beverages collected from several areas in five regions of Jakarta. Levels of V. cholerae in both ice and beverages were determined with the three-tube mostprobable- number (MPN) method and ranged from <0.3 to >110 MPN/ml. The presence of regulatory and virulence gene sequences was determined by using uniplex and multiplex PCR assays. Of 110 samples tested, 33 (30%) were positive for V. cholerae; 21 (64%) were ice samples and the remaining 12 (36%) were beverages. A total of 88 V. cholerae strains were isolated, based on the presence of the toxR gene sequence identified by PCR. Other genetic markers, such as hlyA (59%), ompU (16%), and ctxA (19%), also were found during the search for potential pathogenic strains. The detection and isolation of potentially harmful V. cholerae from ice and beverages in Jakarta indicate that these products pose a health risk from choleragenic vibrios, particularly because of the emergence of classical biotypes of V. cholerae O1 and potentially harmful non-O1 serovars of this species. © International Association for Food Protection. Source

Budu-Amoako E.,University of Prince Edward Island | Greenwood S.J.,University of Prince Edward Island | Dixon B.R.,Microbiology Research Division | Barkema H.W.,University of Calgary | McClure J.T.,University of Prince Edward Island
Journal of Food Protection | Year: 2011

Waterborne outbreaks caused by Cryptosporidium and Giardia are well documented, while the public health implications for foodborne illness from these parasites have not been adequately considered. Cryptosporidium and Giardia are common in domestic livestock, where young animals can have a high prevalence of infection, shedding large numbers of oocysts and cysts. Molecular epidemiological studies have advanced our knowledge on the distribution of Cryptosporidium and Giardia species and genotypes in specific livestock. This has enabled better source tracking of contaminated foods. Livestock generate large volumes of fecal waste, which can contaminate the environment with (oo)cysts. Evidence suggests that livestock, particularly cattle, play a significant role in food contamination, leading to outbreaks of cryptosporidiosis. However, foodborne giardiasis seems to originate primarily from anthroponotic sources. Foodborne cryptosporidiosis and giardiasis are underreported because of the limited knowledge of the zoonotic potential and public health implications. Methods more sensitive and cheaper are needed to detect the often-low numbers of (oo)cysts in contaminated food and water. As the environmental burden of Cryptosporidium oocysts and Giardia cysts from livestock waste increases with the projected increase in animal agriculture, public health is further compromised. Contamination of food by livestock feces containing Cryptosporidium oocysts and Giardia cysts could occur via routes that span the entire food production continuum. Intervention strategies aimed at preventing food contamination with Cryptosporidium and Giardia will require an integrated approach based on knowledge of the potential points of entry for these parasites into the food chain. This review examines the potential for foodborne illness from Cryptosporidium and Giardia from livestock sources and discusses possible mechanisms for prevention and control. Copyright © International Association for Food Protection. Source

Bin Kingombe C.I.,Microbiology Research Division | D'Aoust J.-Y.,Microbiology Research Division | Huys G.,Ghent University | Hofmann L.,Microbiology Research Division | And 2 more authors.
Applied and Environmental Microbiology | Year: 2010

A novel multiplex PCR method using three sets of specific primers was developed for the detection of the cytotoxic (act), heat-labile (alt), and heat-stable (ast) enterotoxin genes in Aeromonas spp. This assay was used to characterize 35 reference strains as well as 537 food-borne isolates. A total of seven gene pattern combinations were encountered, including act, alt, act/alt, act/alt/ast, act/alt/148-bp amplicon, alt/ast,and alt/alt/148-bp amplicon. The alt gene was detected with 34 reference strains (97%) and occurred singly in 14% of these strains. The frequency of occurrence of the act/alt, act/alt/ast, and alt/ast gene patterns in reference strains was 14 (40%), 2 (6%), and 2 (6%), respectively. An unpredicted amplicon was detected in 11 reference strains (31%). Characterization of this amplicon showed that its size was 148 bp, as generated by the AHLF and AHLR primers, and that it uniquely aligned with the Aeromonas salmonicida A449 genome sequence (GenBank accession number CP000644). This amplicon was named Aeromonas salmonicida subsp. salmonicida hypothetical protein amplicon (AssHPA). In the 537 food-borne isolates, the act and alt genes were most dominant and were detected in 349 (65%) and 452 (84%) isolates, respectively, either alone or in combinations. The act and alt genes occurred singly in 30 (6%) and 128 (24%) of these strains, respectively. The act/alt gene pattern occurred in 315 isolates (59%), whereas the ast gene was always linked to strains exhibiting the act/alt/ast and alt/ast gene combinations in 4 (0.7%) and 5 (0.9%) isolates, respectively. The uniplex amplification of three enterotoxin genes separately confirms the specificity of the unique selected primers. This multiplex PCR is rapid and simple and can detect the presence of three Aeromonas enterotoxin genes in a single assay. Copyright © 2010, American Society for Microbiology. All Rights Reserved. Source

Discover hidden collaborations