Klebsiella pneumoniae ORI-1 was isolated in 1998 in France from a rectal swab of a 1-month-old girl who was previously hospitalized in Cayenne Hospital, Cayenne, French Guiana. This strain harbored a ca. 140-kb nontransferable plasmid, pTK1, that conferred an extended-spectrum cephalosporin resistance profile antagonized by the addition of clavulanic acid, tazobactam, or imipenem. The gene for GES-1 (Guiana extended-spectrum ␤-lactamase) was cloned, and its protein was expressed in Escherichia coli DH10B, where this pI-5.8 ␤-lactamase of a ca. 31-kDa molecular mass conferred resistance to oxyimino cephalosporins (mostly to ceftazidime). GES-1 is weakly related to the other plasmid-located Ambler class A extended-spectrum ␤-lactamases (ESBLs). The highest percentage of amino acid identity was obtained with the carbenicillinase GN79 from Proteus mirabilis; with YENT, a chromosome-borne penicillinase from Yersinia enterocolitica; and with L-2, a chromosome-borne class A cephalosporinase from Stenotrophomonas maltophilia (36% amino acid identity each). However, a dendrogram analysis showed that GES-1 clustered within a class A ESBL subgroup together with ESBLs VEB-1 and PER-1. Sequencing of a 7,098-bp DNA fragment from plasmid pTK1 revealed that the GES-1 gene was located on a novel class 1 integron named In52 that was characterized by (i) a 5 conserved segment containing an intI1 gene possessing two putative promoters, P 1 and P 2 , for coordinated expression of the downstream antibiotic resistance genes and an attI1 recombination site; (ii) five antibiotic gene cassettes, bla GES-1 , aac(6)Ib (gentamicin resistance and amikacin susceptibility), dfrXVb (trimethoprim resistance), a novel chloramphenicol resistance gene (cmlA4), and aadA2 (streptomycin-spectinomycin resistance); and (iii) a 3 conserved segment consisting of qacE⌬1 and sulI. The bla GES-1 and aadA2 gene cassettes were peculiar, since they lacked a typical 59-base element. This work identified the second class A ESBL gene of a non-TEM, non-SHV series which was located in the plasmid and integron, thus providing it additional means for its spread and its expression.

Six non‐clonally related enterobacterial isolates producing a same extended‐spectrum β‐lactamase CTX‐M‐15 were isolated in 1999 from patients hospitalized in a New Delhi hospital. CTX‐M‐15 differed from CTX‐M‐3 by an asparagine to glycine substitution in position ABL238. Its gene was located on large plasmids varying in size. In each case, a same insertion sequence ISEcp1 was identified upstream of the 5′ end of blaCTX‐M‐15. Typical −35 and −10 promoter sequences of Enterobacteriaceae were identified in the 3′ end of ISEcp1. The location of ISEcp1 upstream of plasmid‐mediated CTX‐M‐type β‐lactamase genes may contribute to their spread or/and their expression.

Over a 2 1 ⁄2-month period in 1999, 37 ceftazidime-resistant nonrepetitive enterobacterial isolates were collected from 37 patients in a Bangkok hospital, Thailand. Eighty-one percent of these strains expressed a clavulanic acid-inhibited extended-cephalosporin resistance profile. An identical extended-spectrum ␤-lactamase (ESBL), VEB-1, was found in 16 unrelated enterobacterial isolates (Escherichia coli, n ‫؍‬ 10; Enterobacter cloacae, n ‫؍‬ 2; Enterobacter sakazakii, n ‫؍‬ 1; and Klebsiella pneumoniae, n ‫؍‬ 3) and in two clonally related E. cloacae isolates. The bla VEB-1 gene was located on mostly self-conjugative plasmids (ca. 24 to 200 kb) that conferred additional non-␤-lactam antibiotic resistance patterns. Additionally, the bla VEB-1 gene cassette was part of class 1 integrons varying in size and structure. The bla VEB-1 -containing integrons were mostly associated with bla OXA-10 -like and arr-2-like gene cassettes, the latter conferring resistance to rifampin. These data indicated the spread of bla VEB-1 in Bangkok due to frequent transfer of different plasmids and class 1 integrons and rarely to clonally related strains. Plasmid-and integron-mediated resistance to rifampin was also found in enterobacterial isolates.