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Salmonella Reference Laboratory Epidemiology of Salmonella enterica from 1998-2002

Salmonella Reference Laboratory Epidemiology of Salmonella enterica from 1998-2002. C. O’ Hare 1 , N. Delappe 1 , G. Doran 1 , D. Morris 2 , D. Kilmartin 2 , G. Corbett-Feeney 1 and M. Cormican 1 .

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Salmonella Reference Laboratory Epidemiology of Salmonella enterica from 1998-2002

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  1. Salmonella Reference Laboratory Epidemiology of Salmonella enterica from 1998-2002 C. O’ Hare1, N. Delappe1, G. Doran1, D. Morris2, D. Kilmartin2, G. Corbett-Feeney1 and M. Cormican1. 1National Salmonella Reference Laboratory, Medical Microbiology, UCHG, Galway. 2Department of Bacteriology, NUI, Galway.

  2. Introduction Salmonella infection is a significant global public health problem. There are over 2000 serotypes of Salmonella enterica, the bacterial species associated with Salmonellosis. The Salmonella enterica serotypes associated with gastroenteritidis in humans are often present in the gastrointestinal tract of animals including animals intended for human comsumption. The primary source of human infection is by transfer from animals to humans through the food chain, although person-to-person transfer can occur. Most cases of human infection with Salmonella are associated with an acute self-limiting gastrointestinal illness, characterised by diarrhoea, abdominal cramps, fever and vomiting. However, in a proportion of cases, especially among the very young, aged or immunosuppressed the bacteria may invade the blood steam and cause very serious life-threatening infection. The NSRL provides an overview of the epidemiology and burden of disease caused by Salmonella infection in Ireland today. Another important role of the Laboratory is the extended sensitivity testing and phage typing of Salmonella isolates. Global levels of antimicrobial resistance is of increasing concern. Laboratory susceptibilty testing of isolates, is important both as a guide to the therapy of individual patients and as an indicator of the nature and extent of the problem of resistance

  3. Abstract The National Salmonella Reference Laboratory (NSRL) was established in January 2000 with funding through the Western Health Board from the Department of Health and Children. The laboratory assists in the epidemiology and surveillance of Salmonella enterica isolates by the routine testing of extended antimicrobial susceptibilities, phage typing, serotyping and molecular analysis of submitted isolates. By assembly of all Salmonella enterica isolates in a single laboratory, the NSRL facilitates recognition and confirmationof links between individual cases of infection, even whereoutbreaks are widely dispersed Between 1998 and 2002, a total of 4038 isolates (2693 human and 1345 non human) of Salmonella enterica were received Bythe NRSL (banks of Salmonella were kept prior to 2000) Serotyping, antimicrobial susceptibility testing and phage typing were performed by standard methods.

  4. Abstract From 1998 to2002 the relative frequency of isolation of the serotype S.Typhimurium from both clinical and non-clinical Sourcesdeclined from 80% to 27% while the frequency of isolation ofS. Enteritidis increased from 8% to 20.5%.   S. Typhimurium phage type DT104 and the closely related type DT104b accounted for between 90% to 50% of S Typhimurium isolates between 1998-2002. Phage type 4 (PT4) declined from 85% of all S. Enteritidis isolates in 1998 to 21% in 2002, while PT1 increased from non-detected in 1998 to 36% of isolates in 2002. Resistance to multiple antimicrobial agents was very commonly observed in S Typhimurium but rare in S. Enteritidis. Non-human isolates included 1084 isolates from food and animals, and 262 isolates from environmental samples. Of isolates received from cattle and pigs, S. Typhimurium was the most prominent serotype at 57%. By contrast, from isolates submitted from poultry S Kentucky was the most prevalent serotype (21%), and S Typhimurium accounted for only 10%. As in humans, DT104 in S. Typhimurium predominated

  5. Materials and Methods • Clincal Salmonella isolates 1998-2002 N= 714, 438, 638, 509, 394 • Non-clinical Salmonella isolates 1998-2002 N= 7, 16, 212, 573, 537 • Serotyping (Kauffmann and White) • Susceptibility Testing (1)(NCCLS) WHONET • Phage typing (2)(PHLS, Colindale) • Molecular analysis PFGE (3)(PULSENET) Plasmid analysis (refs) Bionumerics

  6. Results: Serotyping Top Serotypes of Salmonella enterica 1998-2002 Clinical Non-clinical Typhimurium 1306 (48%) 325 (24%) Enteritidis 831 (31%) 68 (5%) Bredeney 107 (4%) 123 (9%) Kentucky 46 (2%) 174 (13%) Dublin 42 (2%) 21 (2%) Agona 21 (1%) 75 (6%) Virchow 42 (2%) 7 (1%) Typhi1 9 (<1%) 0 Livingstone2 2 83 (6%) Other3 289 (11%) 552 (41%) 1S. Typhi is a human pathogen only 2 Primarily found in poultry 3 Other serotypes which singly represent >2%

  7. Results: Salmonella Typhimurium phage types 1998-2002 Clinical Non-clinical

  8. Results: Salmonella Enteritidis phage types 1998-2002 Clinical Non-clinical

  9. Results: Pulse Field Gel Electrophoresis PGFE has been standardised for Salmonella and E. coli by PULSENET (CDC, Atlanta, USA). Restriction enzymes used are XbaI and BlnI

  10. Discussion Over the period 1998-2002 among samples from both Clinical and non-clinical sources • In general, isolate numbers have be declining in recent years in line with published data from other EU countries. • Numbers of S. Typhimurium received are decreasing (80% to 27%) while S. Enteritidis are increasing (8% to 21%) Non-clinical isolates encompass a much broader range of serotypes • 78% of clinical S. Typhimurium DT104/DT104b • 51% of non-clinical

  11. Discussion 65% of all S. Typhimurium harboured the ACSSuT multi-resistance phenotype Of these 84% were either phage type DT104 or DT104b 2% of S. Typhimurium were susceptible to the 15 antibiotics tested, by comparison to 33% of S. Enteritidis PT4 and PT1 are the most common phage types in S. Enteritidis. 67% of PT1 is associated with naladixic acid resistance. All naladixic acid resistant strains had reduced susceptibilities to ciprofloxacin (MIC’s 0.094mg/ml to 0.19mg/ml). No ciprofloxacin resistant isolates observed.

  12. Bibliography (1) National Committee for Clinical Laboratory Standards (NCCLS) (1997). Performance standards for antimicrobial susceptibility tests, sixth edition: approved standard. M2-A6. Villanova, PA: NCCLS. (2) Anderson ES, Ward LR, de Saxe MJ. Bacteriophage-typing designations of Salmonella Typhimurium. J Hyg 78: 297-300, 1977 (3) Swaminathan B., Barrett T.J., Hunter S., Tauxe R.V., and the CDC PulseNet Task Force. (2001). PulseNet: The Molecular Subtyping Network for Foodborne Bacterial Disease Surveillance, United States. Emerg. Infect. Diseases. 7, pp. 382-389.

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