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. 2014 Apr;58(4):2482–2484. doi: 10.1128/AAC.02689-13

Enterobacteriaceae with Extended-Spectrum- and pAmpC-Type β-Lactamase-Encoding Genes Isolated from Freshwater Fish from Two Lakes in Switzerland

Helga Abgottspon 1, Magdalena T Nüesch-Inderbinen 1, Katrin Zurfluh 1, Denise Althaus 1, Herbert Hächler 1, Roger Stephan 1,✉
PMCID: PMC4023715  PMID: 24449774

LETTER

There is growing evidence that Enterobacteriaceae harboring clinically relevant bla genes, especially genes encoding the CTX-M family of extended-spectrum β-lactamases (ESBLs), have spread into the environment (1). The purposes of this study were (i) to investigate the occurrence of expanded-spectrum-cephalosporin-resistant Enterobacteriaceae in intestines of fish captured from Lake Zürich and Lake Thun, Switzerland; (ii) to characterize such isolates by their susceptibility to 13 antimicrobial agents (listed in Table 1) (2); (iii) to identify the involved blaESBL/blapAmpC genes (3–5), (iv) for E. coli multilocus sequence typing (MLST) according to Achtman's scheme (http://mlst.ucc.ie/mlst/dbs/Ecoli); and (v) to determine phylogenetic groups (6).

TABLE 1.

Characterization of extended-spectrum- and pAmpC-type β-lactamase-producing Enterobacteriaceae isolated from various fish species from two lakes in Switzerlanda

Isolate no.b Bacterial species Phylogroup MLSTc ESBL and pAmpC-type β-lactamase Antibiotic resistance profile Lake Fish
Species Common name
88v* E. coli A 10 CTX-M-1 AM, CF, CTX, CIP, NA, GM, S, TE, SMZ, TMP Zürich Rutilus rutilus Roach
105 E. coli A 10 CTX-M-15 AM, CF, CTX,NA, GM, S, TE, SMZ Zürich Perca fluviatilis Perch
140a* E. coli A 10 CTX-M-15 AM, CF, SMZ, TMP Zürich Rutilus rutilus Roach
186 E. coli A 23 CTX-M-1 AM, CF, CTX, TE, SMZ, TMP Thun Coregonus lavaretus Whitefish
139 E. coli A 617 CTX-M-15 AM, CF, CTX, CIP, NA, TE, SMZ, TMP Zürich Rutilus rutilus Roach
86b E. coli A 1788 CTX-M-15 AM, CF, TE Zürich Abramis brama Bream
140b* E. coli A 3478 CTX-M-15 AM, CF, NA Zürich Rutilus rutilus Roach
109b E. coli B1 155 CTX-M-14 AM, CF. CTX, CIP, NA, GM, K, S, TE, C, SMZ, TMP Zürich Coregonus lavaretus Whitefish
63 E. coli B1 155 CTX-M-15 AM, AMC, CF, K, SMZ, TMP Zürich Coregonus lavaretus Whitefish
91b E. coli B1 155 CTX-M-15 AM, AMC, CF, K, SMZ, TMP Zürich Rutilus rutilus Roach
172a* E. coli B1 155 CTX-M-15 AM, CF, CTX, NA Zürich Salmo trutta Brown trout
126 E. coli B1 1586 CTX-M-1 AM, CF, CTX, GM, K, S, TE, C, SMZ, TMP Zürich Coregonus lavaretus Whitefish
175b* E. coli B1 NYDd CTX-M-15 AM, CF, CTX, NA Zürich Centrarchidae Sunfish
88t* E. coli B2 131 CTX-M-14 AM, CF, CTX, CIP, NA Zürich Rutilus rutilus Roach
95t* E. coli B2 131 CTX-M-15 AM, AMC, CF, CIP, NA, K, SMZ, TMP Zürich Rutilus rutilus Roach
136 E. coli B2 131 CTX-M-15 AM, CF, CTX, CIP, NA Zürich Rutilus rutilus Roach
110 E. coli B2 131 CTX-M-27 AM, CF, CTX, CIP, NA Zürich Coregonus lavaretus Whitefish
121 E. coli B2 131 CTX-M-27 AM, CF, CTX, CIP, NA, S, TE, SMZ, TMP Zürich Coregonus lavaretus Whitefish
173 E. coli B2 131 CTX-M-27 AM, CF, CTX, CIP, NA, S, TE, SMZ, TMP Zürich Salmo trutta Brown trout
175a* E. coli B2 131 CTX-M-27 AM, CF, CTX, CIP, NA Zürich Centrarchidae Sunfish
172b* E. coli B2 2245 CTX-M-27 AM, CF, CTX, CIP, NA Zürich Salmo trutta Brown trout
144b* E. coli B2 NYDe CTX-M-27 AM, CF, CTX, CIP, NA, S, TE, SMZ, TMP Zürich Rutilus rutilus Roach
132 E. coli D 38 CTX-M-14 AM, CF, CTX, NA Zürich Rutilus rutilus Roach
144a* E. coli D 38 CTX-M-24 AM, CF, CTX, NA Zürich Rutilus rutilus Roach
89 E. coli D 38 CTX-M-27 AM, AMC, CF, CTX, S, SMZ, TMP Zürich Rutilus rutilus Roach
95b* E. coli D 69 CTX-M-14 AM, CF, CTX, CIP, NA, S, TE, SMZ, TMP Zürich Rutilus rutilus Roach
104 E. coli D 963 CMY-2 AM, AMC, CF, CTX, C, SMZ Zürich Perca fluviatilis Perch
77 E. coli D 1462 CTX-M-1 AM, CF, CTX, GM, S, TE, C, SMZ, TMP Zürich Coregonus lavaretus Whitefish
154 E. coli D NYDf CTX-M-15 AM, CF, CTX, CIP, NA, GM, K, TE, TMP Zürich Perca fluviatilis Perch
188 E. coli D NYDg CTX-M-15 AM, CF, CTX, CIP, NA, GM, K, TE, C, SMZ, TMP Thun Coregonus lavaretus Whitefish
146 E. coli D NYDh CTX-M-24 AM, CF, CTX, NA Zürich Rutilus rutilus Roach
191a* E. coli D NYDi SHV-12 AM, CF Thun Coregonus lavaretus Whitefish
191b* Citrobacter freundii ND ND SHV-12 AM, CF, SMZ Thun Coregonus lavaretus Whitefish
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a

Abbreviations: AM, ampicillin; AMC, amoxicillin-clavulanic acid; CF, cephalothin; CTX, cefotaxime; CIP, ciprofloxacin; NA, nalidixic acid; GM, gentamicin; K, kanamycin; S, streptomycin; TE, tetracycline; C, chloramphenicol; SMZ, sulfamethoxazole; TMP, trimethoprim; ND, not determined; NYD, not yet defined (new allelic combination).

b

*, individual strain isolated from one fish.

c

Multilocus sequence type.

d

New allelic combination: adk-6, fumC40, gyrB14, icd-16, mdh-24, purA8, recA14.

e

New allelic combination: adk-53, fumC26, gyrB47, icd-13, mdh-36, purA28, recA29.

f

New allelic combination: adk-92, fumC26, gyrB87, icd-96, mdh-70, purA58, recA2.

g

New allelic combination: adk-18, fumC4, gyrB20, icd-6, mdh-5, purA5, recA4.

h

New allelic combination: adk-4, fumC40, gyrB2, icd-25, mdh-5, purA5, recA19.

i

New allelic combination: adk-46, fumC22, gyrB37, icd-25, mdh-5, purA16, recA33.

A total of 139 freshwater fish consisting of 64 samples of Coregonus lavaretus (whitefish), 33 samples of Perca fluviatilis (perch), 29 samples of Rutilus rutilus (roach), six samples of Salmo trutta (brown trout), 4 samples of Esox lucius (pike), and one sample each of Abramis brama (bream), Tinca tinca (tench), and Centrarchidae species (sunfish) were captured by net. The fish were gutted immediately upon arrival at the port, and the intestines were placed in sterile bags. Samples were homogenized and incubated at a ratio of 1:10 in Enterobacteriaceae enrichment (EE) broth (BD, Franklin Lakes, NJ, USA) at 37°C over night. One loopful of each of the enrichment cultures was inoculated onto chromogenic Brilliance ESBL agar (Oxoid, Hampshire, United Kingdom). Colonies with typical Enterobacteriaceae morphology were selected and identified using API ID 32 Etest strips (bioMérieux, Marcy l'Etoile, France).

Twenty-six (18.7%) of the fish gut samples rendered 33 ESBL- or pAmpC-producing isolates (Table 1). Most of the isolates were E. coli. blaCTX-M genes were detected in 30 isolates. Two isolates contained blaSHV-12, and one isolate carried blaCMY-2. Of the E. coli isolates, 13 belonged to commensal phylogroup A or B1, and 19 belonged to pathogenic phylogroup B2 or D. A total of seven E. coli isolates belonged to the multidrug-resistant pandemic extraintestinal pathogenic group B2:ST131, with a majority (four) containing blaCTX-M-27.

These characterization data strongly resemble results from recent studies in the human population and river waters in Switzerland (1, 7, 8).

In contrast to what is seen in homeothermic animals, E. coli is not a permanent inhabitant of intestinal tracts of fish (9) but reflects the character of the aquatic habitat and the bacterial load in the water (10–12).

On account of their motility, fish must be considered potent disseminators of resistant bacteria. Due to their exposure to a plethora of environmental bacteria on their epidermal mucus layer (13), they also provide excellent conditions for the horizontal transfer of antibiotic resistance genes among the aquatic bacterial community. Recent studies have shown that there is a tendency for Aeromonas spp. from the aquatic environment to acquire ESBLs and other resistance mechanisms (14, 15), thus contributing to the dissemination of resistance determinants. The incidental detection of an Aeromonas sobria isolate containing blaCTX-M-15 from one of the fish intestines in our study corroborates these reports. To our knowledge, this is the first report of CTX-M-15 in Aeromonas sobria, a species representing an important causative agent of fish disease (16).

ACKNOWLEDGMENTS

We thank Peter Grieser and Hans Sieber (professional fishermen) for their cooperation and for their help in collecting the samples.

This work was partly supported by the Swiss Federal Office of Public Health, Division of Communicable Diseases.

Footnotes

Published ahead of print 21 January 2014

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