TABLE 8.

Population studies of plasmid-mediated AmpC β-lactamases

SampleCollection period (yr)LocationFrequency of plasmid-mediated AmpCAmpC type(s)aReference
63 cefoxitin-resistant E. coli strains from 2,133 strains screened199610 hospitals in Greece55 strains (87% of cefoxitin resistant strains) or 2.6% of totalLAT-3 (CMY-6), LAT-4 (LAT-1)104
4,093 Salmonella isolates1996-199817 U.S. state and community health departments13 strains (0.32%)CMY-280
408 nosocomial isolates of K. pneumoniae resistant to cephalosporins or carbapenem1996-200024 U.S. hospitals in 18 states54 strains (13.2%)ACT-1, DHA-1, FOX-5, CMY-2216
190 bloodstream isolates of K. pneumoniae1995-199930 U.S. hospitals in 23 states5 strains (2.6%)ACT-1, FOX-565
752 cephalosporin-resistant K. pneumoniae, K. oxytoca, and E. coli strains1992-200070 sites in 25 U.S. states and the District of ColumbiaK. pneumoniae, 8.5%; K. oxytoca, 6.9%; E. coli, 4%ACT-1, FOX-5, CMY-2, DHA-16
232 cefoxitin-resistant E. coli strains from a total of 29,323 screened1999-200012 Canadian hospitals25 of cefoxitin resistant strains (10.8%) or 0.09% of totalCMY-2220
389 K. pneumoniae blood culture isolates1998-2002Seoul National University Hospital, Seoul, South Korea65 isolates made ESBLs or AmpC enzymes; 28 of 61 strains characterized had AmpCs (7.2% of total)DHA-1, CMY-1-like244
99 cefoxitin- and extended-spectrum cephalosporin-resistant K. pneumoniae isolates1999-2002Teaching hospital, Taiwan77 had AmpC enzymes (in 35 strains combined with ESBLs)DHA-1, CMY-2, CMY-8346
37 cefoxitin-resistant E. coli strains from 103 cephalosporin-resistant strains screened1995-2003Health Protection Agency, London, United Kingdom25 cefoxitin-resistant strains (68%) or 24% of totalCMY-2, CMY-7, CMY-21132
116 cefoxitin-resistant E. coli and 122 cefoxitin-resistant K. pneumoniae strains200316 hospitals in South Korea33% of E. coli strains made CMY-2-like enzymes, and 76% of K. pneumoniae strains made DHA-1DHA-1, CMY-2-like, CMY-10-like, CMY-18170
CLSI screening test-positive E. coli isolates (291 isolates) and K. pneumoniae isolates (282 isolates)20037 medical centers in Taiwan44% of E. coli and 15% of K. pneumoniae isolates had AmpC-like enzymesCMY-2-like in E. coli; DHA-1 and CMY-2-like in K. pneumoniae345
1,429 E. coli isolates collected as part of a surveillance program200430 North American medical centers65 isolates were screen test positive for ESBLs; 26 were screen test-negative AmpC producers13 CMY-2, 3 FOX-5, 1 DHA-173
1,122 cephalosporin-resistant Enterobacteriaceae200416 hospitals in London and Southeast England502 CTX-M ESBL producers, 149 other ESBL producers, and 190 (16.9%) high-level AmpC β-lactamase producersEnterobacter spp. and E. coli mostly overproduced their chromosomal AmpC enzymes; the fewer plasmid-mediated AmpCs were of the Citrobacter type263
746 screening test-positive gram-negative clinical isolates out of 6,421 evaluated2000-200242 ICU and 21 non-ICU sites in the United StatesESBLs found in 4.9% of Enterobacteriaceae, and transferable AmpCs found in 3.3% of K. pneumoniae isolates and in 61% of isolates along with ESBLs; AmpCs also found in 3.6% of K. oxytoca and 1.4% of P. mirabilis isolatesFOX-5, DHA-like, ACT-1-like217
359 cefoxitin-resistant E. coli strains from a total of 78,275 screened2000-2003Calgary Health Region, Canada125 cefoxitin-resistant strains (35%) or 0.16% of totalCMY-2257
123 enterobacterial isolates from 112 inpatients2001University Hospital, Rio de Janeiro, Brazil35 isolates made ESBLs; 5 E. coli isolates also overproduced AmpC; no strains had a plasmid-mediated AmpCNone70
327 cefoxitin-resistant isolates from 1,203 E. coli and 732 Klebsiella sp. isolates collected consecutively2003-2005Hospital, Shanghai, China54 cefoxitin-resistant strains (17%) or 2.8% of total41 DHA-1, 13 CMY-2174
135 E. coli and 38 Klebsiella sp. isolates suspected of AmpC-mediated resistance2004-2006Health Protection Agency, London, United KingdomE. coli, 49%; K. pneumoniae, 55%60 CIT type including CMY-23, 14 ACC type, 11 FOX type, 3 DHA type342
124 cefoxitin-resistant strains from 3,217 Enterobacteriaceae normally lacking inducible chromosomal ampC genes2006-2007University Hospital, Basel, Switzerland5 of 103 cefoxitin-resistant E. coli isolates had plasmid-mediated AmpCs; cause of cefoxitin resistance in 3 K. oxytoca and 18 K. pneumoniae isolates not identifiedNot specified2
2,388 isolates of Enterobacteriaceae from inpatients2003-200413 hospitals in PolandPlasmid-mediated AmpCs identified only in 71 P. mirabilis isolates (20.5% of all P. mirabilis isolates); ESBLs in 11.1% of all isolates24 of 71 sequenced; 19 CMY-15, 4 CMY-12, 1 CMY-38 isolates82
75 E. coli and 14 Klebsiella isolates out of 1,647 strains testing nonsusceptible to cefoxitin or cefpodoxime200530 nursing homes, various outpatient clinics, and Creighton University Medical Center, United States9 E. coli isolates and 1 K. pneumoniae isolateAll CMY-2117
86 screening test-positive strains from 8,048 Enterobacteriaceae strains normally lacking or poorly expressing chromosomal ampC genes1999-2007Seattle Children's Hospital and Regional Medical Center, Seattle, Washington36 had AmpC-type enzymes including 4 with class A β-lactamase as well; 47 had class A ESBLs alone, and 3 had carbapenemases29 CMY-2-like and 6 DHA-types, and 1 uncharacterized267
637 K. pneumoniae and 494 E. coli isolates2005-20065 children's hospitals in China207 were cefoxitin insusceptible, 128 were AmpC+ by test with 3-aminophenylboronic acid, and 74 were AmpC+ by multiplex PCR; occurrence rate of 10.1% in K. pneumoniae and 2.0% in E. coli69 DHA-1, 4 CMY-2, 1 new CMY75
  • a Corrected enzyme designations after resequencing are shown in parentheses (15).