Alfonso Valdivieso-Garcia

Publications (6)14.86 Total impact

• Article: Prevalence and antimicrobial resistance in Campylobacter spp. isolated from retail chicken in two health units in Ontario.

  Anne Deckert, Alfonso Valdivieso-Garcia, Richard Reid-Smith, Susan Tamblyn, Patrick Seliske, Rebecca Irwin, Cate Dewey, Patrick Boerlin, Scott A McEwen
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  ABSTRACT: Campylobacter is an important enteric pathogen of humans and can cause diarrhea, fever, and abdominal pain. Campylobacter infections have frequently been associated with the handling and consumption of raw and undercooked poultry. Antimicrobial resistance among Campylobacter strains is of concern in the treatment of campylobacteriosis in vulnerable populations. A 2-year multidisciplinary study was conducted in the Perth and Wellington-Dufferin-Guelph public health units in Ontario, Canada, to investigate the prevalence and antimicrobial resistance of Campylobacter spp. in retail chicken. Retail chicken samples were collected from randomly selected stores in these health units. Resulting Campylobacter isolates were tested for susceptibility to amoxicillin-clavulanic acid (AMC), ampicillin (AMP), chloramphenicol (CHL), ciprofloxacin (CIP), clindamycin (CLI), erythromycin (ERY), gentamicin (GEN), nalidixic acid (NAL), tetracycline (TCY), and trimethoprim-sulfamethoxazole (SXT) using the E test. The prevalence of Campylobacter in 1,256 retail chicken samples was 59.6%. Of these positive samples, 9% contained Campylobacter coli, 1% contained Campylobacter lari, and 90% contained Campylobacter jejuni. Of the chicken isolates that were resistant to one or more antimicrobial agents, 301 isolates (40%) were resistant to one agent, 374 (50%) were resistant to two, 39 (5%) were resistant to three, 20 (3%) were resistant to four, and 6 (1%) were resistant to five. Nine isolates (1%) were susceptible to all antimicrobial agents tested. All isolates were susceptible to AMC, CHL, and GEN. Less than 10% of isolates were resistant to NAL, CIP, CLI, ERY, and AMP. Resistance to TCY was common (56%). No isolates had a resistance pattern that included all three antimicrobials important in the treatment of human campylobacteriosis (CIP, ERY, and TCY); however, 24 isolates (3.2%) were resistant to at least two of these antimicrobials.
  Journal of food protection 07/2010; 73(7):1317-24. · 1.94 Impact Factor
• Article: Associations between antimicrobial exposure and resistance in fecal Campylobacter spp. from grow-finish pigs on-farm in Alberta and Saskatchewan, Canada.

  Leigh B Rosengren, Cheryl L Waldner, Richard J Reid-Smith, Alfonso Valdivieso-Garcia
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  ABSTRACT: Campylobacter spp. (n = 405), isolated from the feces of apparently healthy grow-finish pigs in 20 herds, were tested for susceptibility to 10 antimicrobials representing seven classes. Twelve percent of the isolates were susceptible to all drugs, while 64% were resistant to two or more antimicrobial classes. Resistance was most common to clindamycin, azithromycin, and erythromycin (71% each), and 10% of the isolates were resistant to ciprofloxacin. An antimicrobial use risk-factor analysis and a variance analysis explored the connection between antimicrobial resistance and the herd. The antimicrobial exposure of each production phase of each herd, through feed and water, was evaluated as a potential risk factor for resistance to macrolides and quinolones. Every 100,000 pig days of macrolide exposure in nursery pigs increased the odds of resistance to macrolides by a factor of 1.3. In contrast, the odds of resistance to a quinolone were nine times higher in Campylobacter from herds without beta-lactam exposure in grow-finish pigs compared with those with exposure. The variance analysis identified remarkably high clustering between isolates within herds; the intraclass correlations for resistances ranged from 0.52 to 0.82. Such extreme clustering demonstrates the potential for herd-level interventions to influence antimicrobial resistance in Campylobacter. The three key findings of this study, i.e., the prevalent resistance to macrolides, the association between macrolide exposure and Campylobacter resistance to macrolides, and the high clustering of resistance within herds, illustrate the need for continued study of antimicrobial-resistant Campylobacter on pig farms and the importance of judicious antimicrobial use in pork production.
  Journal of food protection 04/2009; 72(3):482-9. · 1.94 Impact Factor
• Article: Antimicrobial resistance in Campylobacter, Salmonella, and Escherichia coli isolated from retail turkey meat from southern Ontario, Canada.

  Angela Cook, Richard Reid-Smith, Rebecca Irwin, Scott A McEwen, Alfonso Valdivieso-Garcia, Carl Ribble
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  ABSTRACT: This study estimated the prevalence of Campylobacter, Salmonella, and Escherichia coli isolated from fresh retail turkey purchased at grocery stores in Ontario, Canada. The antimicrobial susceptibility patterns were determined and assessed for potential public health risk. From February 2003 to May 2004, 465 raw turkey meat samples were collected. Antimicrobial susceptibility testing was performed for Campylobacter isolates with a concentration gradient test and for Salmonella and E. coli isolates with a broth microdilution assay. Campylobacter isolates were recovered from 188 (46%) of 412 samples. The prevalence of resistance to one or more antimicrobials was 168 (81%) of 208. For antimicrobials of very high human health importance (category I of Health Canada's antimicrobial categorization), 12 (6%) of 208 Campylobacter isolates were ciprofloxacin resistant. Salmonella isolates were recovered from 95 (24%) of 397 samples. The prevalence of resistance to one or more antimicrobials was 50 (49%) of 102, and 13 (13%) of 102 samples were resistant to five or more antimicrobials. For category I antimicrobials, 14 (14%) of 102 and 1 (1%) of 102 isolates were resistant to ceftiofur and ceftriaxone, respectively. E. coli isolates were recovered from 392 (95%) of 412 turkey samples. The prevalence of resistance to one or more antimicrobials was 906 (71%) of 1,281, and 225 (18%) of 1,281 samples were resistant to five or more antimicrobials. For category I antimicrobials, 30 (2%) of 1,281 samples were resistant to ceftiofur. This study demonstrated that raw turkey pieces are a potential source of human exposure to enteric pathogens, including antimicrobial-resistant bacteria, if undercooked or improperly handled.
  Journal of food protection 04/2009; 72(3):473-81. · 1.94 Impact Factor
• Article: Serological assessment of synthetic peptides of Campylobacter jejuni NCTC11168 FlaA protein using antibodies against multiple serotypes.

  Ursla Fernando, Debabrata Biswas, Brenda Allan, Sam Attah-Poku, Philip Willson, Alfonso Valdivieso-Garcia, Andrew A Potter
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  ABSTRACT: The flagellum of Campylobacter jejuni is not only responsible for initiating colonization of the gastrointestinal tract of host animals but is also a major antigen that induces protective immune responses. However, protection is limited to the homologous strain and the ability to protect against multiple serotypes has yet to be determined. In this study, we have shown that FlaA is an immunodominant protein on NCTC11168 CJ1 flagella and we mapped the immunoreactive epitopes on the protein by probing a series of overlapping synthetic peptides spanning the entire sequence with sera against multiple C. jejuni serotypes. Amino acid residues 176-205 (P8), 376-405 (P16) and 501-530 (P21) were immunodominant and cross-reactive. The mucosal IgA in the intestinal secretions of CJ1-infected birds reacted significantly with peptides P16 and P21 indicating that the specificity of the mucosal response is different from the systemic response. Antisera raised against formalin-killed CJ1 cells and purified flagellin showed positive reactivity with a subset of peptides identified by antisera against live C. jejuni. This study provides insight into the specificity of the host immune responses to the FlaA protein of C. jejuni and suggests that these sequences merit further testing for their immunogenicity and potential as subunit vaccine candidates for multiple serotypes.
  Medical Microbiology and Immunology 04/2008; 197(1):45-53. · 3.83 Impact Factor
• Article: Novel Campylobacter isolation method using hydrophobic grid membrane filter and semisolid medium.

  Alfonso Valdivieso-Garcia, Kathleen Harris, Edward Riche, Stephanie Campbell, Anne Jarvie, Maria Popa, Anne Deckert, Richard Reid-Smith, Kris Rahn
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  ABSTRACT: Culture procedures for isolation of thermophilic campylobacters from food matrices are complex, labor intensive, and time-consuming. Most available methods include the use of antibiotics as selective agents to prevent the growth of competing microflora. A simple procedure for isolation of thermophilic campylobacters after enrichment in Rosef's enrichment broth was developed using a hydrophobic grid membrane filter (HGMF) on semisolid medium (SSM). SSM contains no antibiotics, and the HGMF physically separates Campylobacter from the enrichment broth, allowing isolation based on differential motility. The HGMF-SSM method was compared to the Agriculture and Agri-Food Canada Food Safety Procedures Manual (FSPM-10) method (Isolation of Thermophilic Campylobacters from Fresh Pork, Beef Veal, Poultry and Ready-to-Eat Meat Products), which includes the use of selective antibiotics. During the initial study, after enrichment the HGMF-SSM method yielded pure cultures of campylobacters after 16 to 18 h (overnight) compared with 48 h for the FSPM-10 method. Ninety-four turkey samples collected at local retail stores and 38 frozen pig fecal samples were processed by both methods. Thirty-five samples (26.5%) were positive by the HGMF-SSM method; 24 (18.2%) of these positive samples contained Campylobacter jejuni and 11 (8.3%) contained Campylobacter coli. With the FSPM-10 method, 25 samples (18.9%) were positive: 21 (15.9%) with C. jejuni and 4 (3%) with C. coli. For a subsequent field study, only the HGMF-SSM method was used to isolate Campylobacter from 1,200 chicken samples and 454 turkey samples sold at retail. Analysis of five subisolates from various samples indicated that only one type of Campylobacter was recovered by the HGMF-SSM method, as ascertained by MICs for 10 antimicrobials, sequencing of the short variable region of the flaA gene, and fingerprinting based on amplified fragment length polymorphism. The absence of antibiotics in the SSM may explain the higher recovery of thermophilic campylobacters. The HGMF-SSM method resulted in improved isolation of campylobacters and is simpler, faster, cheaper, and less labor intensive than the FSPM-10 method. The recovery of one type of Campylobacter from the chicken samples may have important implications, particularly in epidemiological studies.
  Journal of food protection 03/2007; 70(2):355-62. · 1.94 Impact Factor
• Article: Pathogenesis of Guillain-Barre syndrome.

  Raymond Sw Tsang, Alfonso Valdivieso-Garcia
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  ABSTRACT: Guillain-Barre syndrome is a postinfectious disorder caused by an aberrant immune response to an infectious pathogen, resulting in an autoimmune disease. As with other autoimmune diseases of infectious nature, the intricate balance of the numerous factors involved in the immune response may determine the outcome of the interaction between the microbe and host. Recent studies focusing on the role of cytokines and its network of related mediators and receptors suggest that any imbalance may make a significant contribution to the outcome of the infectious disease process. Better understanding of the pathogenesis of Guillain-Barre syndrome may lead to the discovery of newer therapeutics and may also serve as a model for studying other autoimmune diseases.
  Expert Review of Anticancer Therapy 01/2004; 1(4):597-608. · 3.28 Impact Factor