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Shigella sonneiShigella sonnei Antimicrobial Resistance, Phage Typing And Antimicrobial Resistance, Phage Typing And
11Interim National Salmonella Reference Laboratory, UCHG.Interim National Salmonella Reference Laboratory, UCHG.22National University of Ireland, GalwayNational University of Ireland, Galway
33Cork Institute of Technology.Cork Institute of Technology.44LEP, PHLS, ColindaleLEP, PHLS, Colindale
Shigella sonnei is a leading cause of gastroenteritis in both developing and industrialised
countries. Various phenotypic and genotypic methods have been used to type S. sonnei
isolates, including phage typing, antimicrobial resistance typing (ART), pulsed field gel
electrophoresis (PFGE), random amplification of polymorphic DNA (RAPD) and
plasmid profiling. Sixty-seven S. sonnei isolates from various counties in Ireland were
analysed using PFGE and ART , while phage typing (n=8), plasmid profiling (n=28), and
integron analysis (n=14) was carried out on subsets of strains. PFGE divided the isolates
into two major clusters, A (n= 53) and B (n=14). There were seven different resistance
profiles detected, with resistance to ampicillin, streptomycin(S) and sulphonamide (Su)
(associated exclusively with PFGE A), being the most common (76%). Resistance to S,
Su, tetracycline and trimethoprim was common within PFGE B (78%). Two PFGE A
strains phage typed were PT9, while the PFGE B strains typed as PT6 (n=4), and PT50
(n=1) and RDNC (n=1). There were several different plasmid profiles among the strains
analysed. Two different plasmid profiles were observed among PFGE A, ASSu strains.
Integron analysis of a subset of isolates (n=14) revealed that at least 1 isolate contained a
complete class 1 integron structure while 10 isolates contained a gene encoding integrase
2. Six isolates which were resistant to trimethoprim by phenotypic methods contained an
amplicon for a DHFR gene which confers resistance to trimethoprim. Our data
demonstrate very limited diversity among S. sonnei in Ireland by PFGE, but greater
discrimination can be achieved by a use of a variety of typing methods.
Restriction patterns interpreted by criteria of Tenover et al
48.5
97.0
145.5
194.0
242.5
291.0
339.5
Kb
PFGE analysed by Bionumerics
RDNC
PT9
PT6PT50
PT6
PT9
PT6
Phage Typing of S. sonnei isolates (performed by LEP, Colindale, London)
PT 9 PFGE A (n=2) PT6 PFGE B (n=1) PFGE B1 (n=1)
PFGE B4 (n=1)
PFGE B5 (n=1)
PT50 PFGE B3 (n=1)
RDNC PFGE B (n=1)
Phage type 6 accounts for approximately 80% of U.K. infections.PT9 is quite rare.
Conjugation of S.sonnei isolates
1 Isolated on Trptone Soya Agar , Oxoid2 Isolated on Mueller Hinton Agar, BBLA = Ampicillin 100g/ml agarNa = Nalidixic acid 30g/ml agarT = Tetracycline 20g/ml agarTm = Trimethoprim 5g/ml agar
Isolate no Resistance profile
Transconjugant Res. profile
Selected on:
3331 ASSu ASSu A + Na 1 3331 ASSu A A + Na 1 3599 A A A + Na 1 Dublin 3 SSuTTm SSuT T + Na 1 Cork 2 ASSuTTm ASuT A + Na 1 3219 ASuTm A A + Na 1 3219 ASuTm ASuTm Tm + Na 2
Plasmid Profiles
B4 A A A A A A A1 A1 B A A B1 B4 pDu
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
108
6
4
2
3
5
Kb
Most isolates had multiple plasmids ranging in size from 2kb to >50kb