title: SHV-1 beta-lactamase is mainly a chromosomally encoded species-specific enzyme in Klebsiella pneumoniae.
abstract: The nature of the SHV-1 beta-lactamase gene was analyzed in 97 epidemiologically unrelated Klebsiella pneumoniae strains isolated from clinical samples. beta-Lactamase bands that focused at a pI of 7.6 (SHV-1-type) in 74 strains, at a pI of 7.1 (LEN-1-type) in 13 strains, and at a pI of 5.4 (TEM-1-type) in 10 strains were detected by analytical isoelectric focusing (IEF). Among the 74 SHV-1-producing strains, 40 had, in addition to the pI 7.6 band, an additional band on IEF: 20 had a band with a pI of 7.1 and 20 had a band with a pI of 5.4. Most of the 74 SHV-1-producing strains (76.7%) carried plasmids. Transfer of beta-lactam resistance by conjugation was possible in only 9.3% of the strains tested. SHV-1 gene-specific PCR-restriction fragment length polymorphism (PCR-RFLP) analysis of the chromosomal DNA was positive for 93 of the 97 strains and negative for only 4 of the 10 samples with K. pneumoniae TEM-1 producers. In an attempt to approximate the location of the SHV gene locus by endonuclease restriction analysis, RFLP analysis with Southern blotting of chromosomal DNA with a labeled SHV-1 fragment as a probe was used to study the 97 strains. A trial with EcoRI showed at least one positive hybridization band for 96 strains; two bands were detected for 8 strains. The hybridization was negative for only one TEM-1 beta-lactamase-producing strain. DNA sequence analysis showed no differences in promoter regions or extra stop-triplet sequences; only point mutations determined different allelic variants. The novel SHV-type variants are designated SHV-32 and SHV-33. As a result of the RFLP and sequencing analyses, it can be postulated that the loci for SHV-1 and LEN-1 genes are arranged in tandem. Our results strongly support the hypothesis that the ancestor of the SHV-1 beta-lactamase originated from the K. pneumoniae chromosome.
authors.affiliation: Department of Pharmacology, Municipal Institute of Medical Investigation, 08003 Barcelona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Chaves
authors.forename: M G
authors.initials: MG
authors.lastname: Ladona
authors.forename: C
authors.initials: C
authors.lastname: Segura
authors.forename: A
authors.initials: A
authors.lastname: Coira
authors.forename: R
authors.initials: R
authors.lastname: Reig
authors.forename: C
authors.initials: C
authors.lastname: Ampurdanés
mesh_terms: D002876:Chromosomes, Bacterial; D004269:DNA, Bacterial / Q000032:analysis; D006801:Humans; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D013045:Species Specificity; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; C054882:beta-lactamase PIT-2; D001618:beta-Lactamases