Introduction
Materials and methods
Bacterial isolates and susceptibility testing
Compound/phenotype | 1997–2010 N = 216 | 1997–2005 N = 128 | 2006–2010 N = 88 | MIC breakpoints/ECOFF (μg/ml) | |||||
---|---|---|---|---|---|---|---|---|---|
Number (%) non-susceptible | Number (%) non-susceptible | MIC 50 (mg/l) | MIC90 (mg/l) | Number (%) non-susceptible | MIC 50 (mg/l) | MIC90 (mg/l) | S ≤ | R > | |
Vancomycina
| 216 (100) | 128 (100) | 512 | >512 | 88 (100) | >256 | >256 | 4 | 4 |
Teicoplanina
| 216 (100) | 128 (100) | 64 | 128 | 88 (100) | 48 | >256 | 2 | 2 |
Ampicillina
| 215 (99.5) | 128 (100) | >128 | >256 | 87 (98.8) | 128 | >256 | 4 | 8 |
HLGRa
| 172 (79.6) | 118 (92.2) | >1024 | >1024 | 54 (64.4) | >1024 | >1024 | 128 | 128 |
HLSRa
| 167 (77.3) | 112 (87.5) | >1024 | >2048 | 55 (62.5) | >1024 | >2048 | 512 | 512 |
HLAR 28
| 147 (68.1) | 110 (86) | >1024 | >1024 | 37 (42) | >1024 | >2048 | - | - |
Quinupristin/dalfopristina
| 2 (0.9) | 1 (0.8) | 1 | 2 | 1 (1.1) | 1 | 1.5 | 1 | 4 |
Linezolida
| 1 (0.5) | 0 (0) | 1 | 4 | 1 (1.1) | 1 | 2 | 4 | 4 |
Tigecyklinea
| 0 (0) | 0 (0) | 0.06 | 0.19 | 0 (0) | 0.06 | 0.25 | 0.25 | 0.5 |
Tetracyclineb
| 135 (62.2) | 89 (68.9) | 64 | 128 | 46 (52.3) | 8 | 128 | 4 | 4 |
Ciprofloxacinb
| 215 (99.5) | 127 (99.2) | 128 | >256 | 88 (100) | 128 | 256 | 4 | 4 |
Daptomycinb
| 0 (0) | 0 (0) | 2 | 3 | 0 (0) | 2 | 3 | 4 | 4 |
Chloramphenicolc
| 53 (24.4) | 30 (23.2) | 8 | 16 | 23(26.1) | 8 | 16 | 8 | ≥32c
|
MDR28
| 216 (100) | 128 (100) | nc | nc | 88 (100) | nc | nc | – | – |
DNA isolation and genotyping of isolates
Plasmid profiling, hybridization analyses, Tn1546 typing and statistical analysis
Results
Susceptibility to antimicrobial agents
MLVA, MLST, IS16 and virulence markers detection
Structural diversity of Tn1546 transposons
Plasmid gene content among VREfm and diversity of vanA-plasmids
Strain ID/year of isolation | Code of medical centrea
| Tn1546 type | MLST type (lineage) | Number of VanA plasmid bands | Hypothetical genetic event b
| VanA plasmid replicon types and stabilization systems (approximate size in kb)c
| ||
---|---|---|---|---|---|---|---|---|
1639/1997 |
Gd-a
| BBBI1 | 407(17/18) | 1 | rep17 TA1 (45) | |||
1641/1997 |
Gd-a
| BBBI2 | 408(17/18) | 1 | Chromosomal integration of 50-kb plasmid | rep17 rep18 TA1 (50) | rep2 rep17 rep18 TA1 (chr) | |
3132/1998 |
Gd-p
| A1 | 18(17/18) | 2 | Transfer of 40-kb plasmid between ST18 and ST411 strains, followed by plasmid recombination or transposition of A1 | rep2 rep17 TA1 (35) | rep2 TA2 (40) | |
3136/1998 |
Gd-p
| A1 | 411 (singleton) | 2 | rep2 TA2 (40) | rep2 TA2 (270) | ||
7952/1999 |
Gd-p
| nt | 381(17/18) | 3 | rep2 rep17 TA1 (35) | rep17 TA1 (170) | rep17 TA1 (320) | |
2509/2000 |
Po-1
| A3 | 386(17/18) | 2 | Chromosomal integration of 40-kb plasmid | rep2 (30) | rep2 TA1 TA2 (40) | rep1 rep2 TA1 TA2 (chr) |
2524/2000 |
Po-1
| A3 | 382(17/18) | 2 | rep17 TA2 (40) | rep1 TA2 relpEF1(140) | ||
2712/2000 |
Po-1
| A3 | 385(17/18) | 3 | Transposition of A3 or plasmid recombination in ST385 strain | TA2 (40) | rep1 TA2 (140) | rep1 reppLG1 TA2 relpEF1 (265) |
1409/2002 |
Po-4
| A3 | 385(17/18) | 1 | rep2 reppMG1 TA1 TA2 (250) | |||
2506/2000 |
Po-1
| A4 | 385(17/18) | 2 | Derivative of A3 in ST385 strain, with concomitant change of plasmid backbone | rep2 rep18 TA2 (<30) | rep1 rep18 TA2 (265) | |
291/2002 |
Po-2
| A3 | 117(17/18) | 1 | rep1 rep17 TA1 TA2 (145) | |||
1714/2003 |
Po-2
| A3 | 117(17/18) | 1 | Clonal spread of ST117 with 265-kb plasmid, followed by transposition of A3 among plasmids or plasmid recombination | rep1 (265) | ||
710/2004 |
Po-2
| A3 | 117(17/18) | 4 | rep1 (265) | rep1 rep2 rep18 TA1 TA2 (255,310,360) | ||
914/2002 |
Po-2
| A3 | 17(17/18) | 1 | rep1 rep17 TA1 (155) | |||
2039/2003 |
Po-2
| A3 | 410(17/18) | 1 | rep1 (145) | |||
3010/2003 |
Po-2
| A3 | 192(78) | 1 | rep1 rep2 rep18 (145) | |||
655/2007 |
Po-4
| A6 | 549(78) | 1 | rep2 TA1 TA2 (40) | |||
3003/2003 |
Po-2
| E | 117(17/18) | 1 | Transposition of E or plasmid recombination in ST117 strain | rep1 rep2 rep18 reppLG1 TA1 (165) | ||
2127/2004 |
Po-2
| E | 117(17/18) | 1 | rep1 reppLG1 (165) | |||
2512/2000 |
Po-1
| D | 17(17/18) | 1 | rep1 TA2 (30) | |||
1156/2002 |
Po-2
| D | 382(17/18) | 1 | rep1 rep2 TA2 (50) | |||
714/2003 |
Kr-1
| C1 | 117(17/18) | 1 | rep2 rep18 rep17 reppLG1 TA1 TA2 (450) | |||
756/2003 |
Kr-1
| C1 | 17(17/18) | 1 | rep17 rep18 TA1 TA2 relpEF1 (70) | |||
1679/2003 |
Kr-1
| C1 | 18(17/18) | 1 | Clonal spread of ST18 strain and concomitant change of plasmid size by a presumable deletion (loss of relpEF1) | rep2 rep18 TA1 TA2 relpEF1 (70) | ||
3779/2004 |
Kr-4
| C1 | 18(17/18) | 1 | rep2 rep18 TA1 TA2 (65) | |||
4002/2005 |
Kr-3
| C1 | 387(17/18) | 1 | Plasmid transfer and ∼15-kb deletion | rep2 rep18 TA1 TA2 relpEF1 (55) | ||
1332/2003 |
Kr-1
| C1 | 132(17/18) | 1 | Clonal spread of ST132 strain with 45-kb plasmid harbouring C1 transposon | rep17 TA1 (45) | ||
1336/2003 |
Kr-1
| C1 | 132(17/18) | 1 | rep17 TA1 (45) | |||
2981/2003 |
Mi
| ntd
| 132(17/18) | 1 | Evolution of C1 transposon within the same ST132 strain and 45-kb plasmid backbone | rep17 TA1 (45) | ||
2216/2005 |
Kr-1
| C1 | 388(17/18) | 1 | rep2 rep17 rep18 TA1 TA2 relpEF1 (75) | |||
84/2010 |
Gdy
| C2 | 17(17/18) | 1 | rep2 rep17 TA1 TA2 (50) | |||
3552/2009e
|
Wa-10
| A1 | 18(17/18) | 2 | Ancestor for B2 transposon, associated with plasmids of unknown rep-type(s) | (<30) | (170) | |
3240/2006 |
Po-5
| B2 | 17(17/18) | 3 | Concomitant transfer of three ∼30-, 160- and 380-kb plasmids with unknown rep-type(s), carrying B2 transposon, into diverse clonal backgrounds | (30) | (160) | (380) |
1930/2007 |
Wa-1
| B2 | 64(17/18) | 3 | (30) | (160) | (380) | |
4285/2008 |
Wa-1
| B2 | 192(78) | 3 | (30) | (160) | (380) | |
5151/2008 |
Osw
| B2 | 18(17/18) | 3 | (30) | (160) | (380) | |
1767/2010 |
Wa-3
| B2 | 780(17/18) | 3 | (<30) | (160) | (380) | |
5009/2009 |
Wa-2
| B2 | 230(78) | 3 | Transfer of 160-kb plasmid of unknown rep-type, followed by transposition of B2 among plasmids or plasmid recombination | rep17 TA1 (<30), rep17 (45) | (160) | |
3238/2006 |
Sk
| B2 | 279(17/18) | 2 | Transfer of 30-kb plasmid of unknown rep-type, followed by transposition of B2 among plasmids or plasmid recombination | (30) | rep18 reppLG1 (180) | |
2546/2008 |
Gr
| BH | 202(17/18) | 3 | BH derivative of B2 transposon on ∼370-kb plasmid of unknown rep-type, followed by transposition of BH among plasmids or plasmid recombination | rep17 rep18 TA1 (30) | rep17 rep18 TA1 (155) | (370) |
8744/2010 |
Wa-2
| B2 | 561(17/18) | 1 | rep2 rep17 TA2 relpEF1(35) | |||
484/2010 |
Ke
| B2 | 17(17/18) | 3 | Transfer of <30-kb plasmid among strains of ST877 and ST17 | rep2 rep17 rep18 TA1 (<30) | rep2 (160) | rep2 rep17 rep18 TA1 (320) |
9363/2010 |
Sw
| B2 | 877(17/18) | 1 | rep2 rep17 rep18 TA1 (<30) | |||
3856/2005 |
Wa-1
| B4 | 78(78) | 1 | rep2 TA2 (50) | |||
991/2009e
|
Wa-4
| G | 18(17/18) | 1 | Recombination events or transposition of G among rep17 plasmids. | rep17 (100) | ||
3554/2009e
|
Wa-10
| G | 192(78) | 1 | rep17 (50) | |||
2944/2009 |
Ko
| G | 18(17/18) | 1 | rep2 rep17 TA2 (35) | |||
3392/2009 |
Ost
| G | 78(78) | 1 | rep17 relpEF1 (45) | |||
726/2010 |
In
| G | 17(17/18) | 1 | rep17 relpEF1 (100) | |||
3322/2007 |
Wa-2
| BC1 | 412(78) | 1 | Evolution of BC transposons within the same ST412 strain in the ∼35-kb plasmid backbone | rep2 rep17 TA2 (35) | ||
107/2010 |
Wa-2
| BC5 | 412(78) | 1 | rep2 rep17 TA2 (35) | |||
3948/2010 |
Wa-2
| BC4 | 412(78) | 1 | rep2 rep17 TA2 (35) | |||
1901/2005 |
Lo
| F | 279(17/18) | 1 | rep17 rep18 TA2 (50) | |||
8034/2010 |
Kr-5
| B3 | 341(78) | 2 | rep2 rep17 TA1 TA2 relpEF1(50) | rep2 rep17 TA2 relpEF1(65) | ||
8628/2010 |
Ka
| BBI | 202(17/18) | 1 | (115) |