TABLE 1.
Distribution of aac(6′)-Ib-cr and qnrB genes among 163 ESBL-producing enterobacterial isolates at the National Oncology Center, Sofia, Bulgaria, from 2000 to 2005 and the respective ESBL prevalence rates
| Species | No. of isolates with indicated aac(6′)-Ib variant and qnrB/total no. of ESBL-positive isolates (%)a
|
|||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2000
|
2001
|
2002
|
2003
|
2004
|
2005
|
|||||||||
| cr | Any | cr | Any | cr | Any | qnrBc | cr | Any | cr | Any | cr | Any | qnrBd | |
| E. coli | 0/3 | 2/3 (67) | 0/8 | 5/8 (63) | 3/10 (30) | 7/10 (70) | 9/16 (56) | 14/16 (88) | 16/24 (67) | 16/24 (67) | 19/33 (58) | 21/33 (64) | ||
| K. pneumoniae | 0/4 | 1/4 (25) | 0/5 | 4/5 (80) | 0/2 | 0/2 | 0/18 | 14/18 (78) | 0/5 | 1/5 (20) | 1/6 (17) | 1/6 (17) | ||
| C. freundii | 0/0 | 0/0 | 0/0 | 0/0 | 0/5 | 5/5 | 5/5 (100) | 0/0 | 0/0 | 0/1 | 0/1 | 2/4 (50) | 2/4 (50) | 2/4 (50) |
| M. morganii | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 1/1 (100) | 1/1 (100) | ||
| E. aerogenes | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 0/0 | 1/1 (100) | 1/1 (100) | ||
| Otherb | 0/1 | 1/1 (100) | 0/1 | 0/1 | 0/2 | 2/2 (100) | 0/0 | 0/0 | 0/3 | 0/3 | 0/10 | 1/10 (10) | ||
| Total | 0/8 | 4/8 (50) | 0/14 | 9/14 (64) | 3/19 (16) | 14/19 (74) | 9/34 (26) | 28/34 (82) | 16/33 (48) | 17/33 (52) | 24/55 (44) | 27/55 (49) | ||
The numbers of ESBL-positive isolates/total numbers of isolates are as follows: for 2000, 8/461 (1.7%); for 2001, 14/553 (2.5%); for 2002, 19/646 (2.9%); for 2003, 34/546 (6.2%); for 2004, 33/674 (4.9%); and for 2005, 55/636 (8.6%).
This category included one isolate each of Providencia rettgeri (recovered in 2000) and Escherichia hermannii (recovered in 2002), two Klebsiella oxytoca isolates (recovered in 2002 and 2005), six Serratia marcescens isolates (recovered in 2001, 2003, and 2005), and seven Enterobacter cloacae isolates (recovered in 2005). The four aac(6′)-Ib-positive isolates included one each of P. rettgeri, E. hermannii, K. oxytoca, and E. cloacae.
Existence of qnrB10 (two isolates) and qnrB18 (three isolates) in C. freundii.
Coexistence of qnrB13 or qnrB18 with aac(6′)-Ib-cr in C. freundii isolates.