TABLE 1.
Genetic and phenotypic traits of CTX-M-producing Escherichia coli from organic layers
| Farm | Strain designationa | Chicken age (wk) | PFGE typeb | β-Lactamase genesc | ClaI plasmid RFLPd | BglII plasmid RFLPd | Plasmid replicon typed | Resistance cotransferred by the plasmide |
|---|---|---|---|---|---|---|---|---|
| B | S1 | 48 | B | CTX-M-9 group (14/17) | 2 | b | N | None |
| B | S21* | 48 | M | CTX-M-9 group (14/17) | 2 | b | N | None |
| B | S31 | 48 | M | CTX-M-9 group (14/17) | − | − | − | − |
| B | S42* | 51 | M | CTX-M-9 group (14/17) | 2 | b | N | None |
| B | S52 | 51 | I | CTX-M-1 group (1/61), TEM-1 | 3 | c | I1 | STR, SUL, TET, TMP |
| B | S63 | 51 | I | CTX-M-1 group (1/61), TEM-1 | − | − | − | − |
| B | S73 | 51 | I | CTX-M-1 group (1/61), TEM-1 | − | − | − | − |
| B | S84 | 51 | I | CTX-M-1 group (1/61), TEM-1 | − | − | − | − |
| B | S94 | 51 | I | CTX-M-1 group (1/61), TEM-1 | − | − | − | − |
| B | S105 | 51 | I | CTX-M-1 group (1/61), TEM-1 | 3 | c | I1 | STR, SUL, TET, TMP |
| B | S115 | 51 | I | CTX-M-1 group (1/61), TEM-1 | − | − | − | − |
| B | S126 | 51 | J | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| B | S136 | 51 | K | CTX-M-2 group (2/20/44) | − | − | − | SUL, TET, TMP |
| B | S146 | 51 | L | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| B | F1 | 61 | A | CTX-M-2 group (2/20/44), TEM-1 | NI | NI | Untypeable | SUL, TET, TMP |
| B | F2 | 61 | D | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| B | F3 | 61 | C | CTX-M-1 group (1/61) | NI | NI | Untypeable | SUL, TET, TMP |
| B | F4 | 61 | E | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| B | F5 | 61 | N | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| B | F6 | 61 | O | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| B | F7 | 61 | NT | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| B | CS1 | 61 | H | CTX-M-2 group (2/20/44) | − | − | − | SUL, TET, TMP |
| B | CS2 | 61 | G | CTX-M-2 group (2/20/44) | NI | NI | Untypeable | SUL, TET, TMP |
| C | S17 | 66 | P | CTX-M-1 group (1/61) | 1 | a | I1 | SUL, TET |
| C | S27 | 66 | P | CTX-M-1 group (1/61) | − | − | − | − |
| C | F1 | 77 | D | CTX-M-1 group (1/61) | 1 | a | I1 | SUL, TET |
| C | F2 | 77 | F | CTX-M-1 group (1/61), TEM-1 | 1 | a | I1 | SUL, TET, TMP |
| C | F3 | 77 | F | CTX-M-1 group (1/61), TEM-1 | − | − | − | − |
| C | CS1 | 77 | NT | CTX-M-1 group (1/61) | 1 | a | I1 | SUL, TET |
| C | CS2 | 77 | F | CTX-M-1 group (1/61), TEM-1 | 1 | a | I1 | SUL, TET, TMP |
Letters indicate the sample type. S, sock sample; F, fecal dropping; CS, cloacal swab. Isolates sharing the same superscript number were obtained from the same sample. *, indole-negative isolates confirmed as E. coli by rpoB sequencing. Designations in bold represent isolates used for conjugative plasmid transfer experiments.
PFGE types were assigned by visual inspection of the macrorestriction profiles interpreted according to Tenover et al. (8). NT, nontypeable isolates.
Beta-lactamase genes in the donors were characterized by PCR and sequencing. The specific genes compatible with the obtained sequences are reported in parentheses. Designations representing genes transferred by conjugation, as determined by PCR but not by sequencing, are underlined.
Characterization was done on plasmids obtained from the transconjugants. −, not characterized; NI, not interpretable.
Susceptibility to additional antimicrobials was determined for donors and transconjugants by the disk diffusion method. The antimicrobials tested included sulfonamides (SUL), streptomycin (STR), tetracycline (TET), and trimethoprim (TMP). Designations representing patterns transferred by conjugation are underlined. −, not characterized.