Pseudomonas aeruginosa GW-1 was isolated in 2000 in South Africa from blood cultures of a 38-year-old female who developed nosocomial pneumonia. This isolate harbored a self-transferable ca. 100-kb plasmid that conferred an expanded-spectrum cephalosporin resistance profile associated with an intermediate susceptibility to imipenem. A ␤-lactamase gene, bla GES-2 , was cloned from whole-cell DNA of P. aeruginosa GW-1 and expressed in Escherichia coli. GES-2, with a pI value of 5.8, hydrolyzed expanded-spectrum cephalosporins, and its substrate profile was extended to include imipenem compared to that of GES-1, identified previously in Klebsiella pneumoniae. GES-2 activity was less inhibited by clavulanic acid, tazobactam and imipenem than GES-1. The GES-2 amino acid sequence differs from that of GES-1 by a glycine-to-asparagine substitution in position 170 located in the omega loop of Ambler class A enzymes. This amino acid change may explain the extension of the substrate profile of the plasmid-encoded ␤-lactamase GES-2.Clavulanic acid-inhibited extended-spectrum ␤-lactamases (ESBLs) conferring resistance to expanded-spectrum cephalosporins have been reported, first in Enterobacteriaceae and then in Pseudomonas aeruginosa (11,23). Rare reports of TEM-and SHV-type ESBLs in P. aeruginosa are known (SHV2a, 23,31]), while they have been extensively described in Enterobacteriaceae (11). Three non-TEM-, non-SHV-type ESBLs have been reported in P. aeruginosa, i.e., PER-1, VEB-1, and OXA-18 ␤-lactamases (20,25,27,38). The PER-1 ␤-lactamase gene is widespread in Turkey, although not reported as plasmid mediated in P. aeruginosa (39). VEB-1 ␤-lactamase, originally described in Escherichia coli and Klebsiella pneumoniae isolates in Vietnam, has been found in P. aeruginosa and enterobacterial isolates in Thailand (8,29,38).We have recently identified another Ambler class A ␤-lactamase, GES-1, in a K. pneumoniae isolate in French Guiana (28). It was found to be remotely related to other ESBLs. This ESBL differs by two amino acid substitutions from IBC-1 ␤-lactamase recently found in an Enterobacter cloacae isolate in Greece (7). bla VEB-1 , bla GES-1 , and bla IBC-1 are plasmid located and are part of gene cassettes integrated into class 1 integrons (7,28,29).Mobile cassettes contain genes most often mediating antibiotic resistance and a cassette recombination site, designated the 59-base element (59-be) (9, 10). The 59-be sites vary in length (57 to 141 bp) and structure, but they are all bounded by a core site (GTTRRRY) at the recombinant crossover point and an inverse core site (RYYYAAC) at the 3Ј end of the inserted gene (4, 9). Integrons are genetic elements capable of integrating individual gene cassettes by a site-specific recombination mechanism that involves a DNA integrase, IntI; an integron-specific recombination site, attI; and 59-be (4, 9, 10). The 5Ј conserved segment (5Ј-CS) of the integrons contains the integrase gene (intI) and the recombination site attI1. The 3Ј-CS of class 1 integrons carries the antiseps...

The aim of this study was to identify and characterize 97 methicillin-resistant Staphylococcus aureus (MRSA) isolates. Two conventional multiplex PCR assays, a real-time PCR assay and two PCR-based genotyping techniques including the spa- and hypervariable region (HVR)-typing methods were used to identify and characterize 97 MRSA strains isolated between April 2006 to September 2007 from the Steve Biko Academic Hospital. All MRSA isolates were positive for 16S rRNA gene, 99% were positive for the mecA gene and 4% positive for the Panton-Valentine leukocidin (PVL) gene. Staphylococcal cassette chromosome mec (SCCmec) typing showed 67% of isolates were SCCmec II [health-care-associated MRSA (HA-MRSA)], 14% were SCCmec III (HA-MRSA) and 4% were SCCmec IVd [community-associated MRSA (CA-MRSA)]. These CA-MRSA isolates showed a prevalence of 100% for the PVL gene. Using spa typing, three distinct clusters could be identified while HVR typing revealed six different clusters. CA-MRSA isolates were clustered together using spa and HVR typing. This study showed the prevalence of the CA-MRSA strains, PVL genes, the SCCmec types and the clonality of the MRSA strains. The high prevalence of the PVL gene in CA-MRSA isolates already residing in intensive care units was alarming and indicated the emergence of new MRSA lineages with a particular fitness for community and hospital transmission.

Extended-spectrum beta-lactamases (ESBLs) are considered to be one of the most important antibiotic resistance mechanisms. This study reported the ESBL-producing genes in 53 randomly selected clinical bacterial isolates from the Steve Biko Academic Hospital. The presence of the bla(SHV), bla(TEM) and bla(CTX-M) genes was determined, and the overall prevalence of these genes detected in this study was 87% (46/53) in comparison with the literature; these results were higher when compared with 33% for Escherichia coli in Europe and 0.8% in Denmark for similar pathogens. These research findings indicated that it is crucial to routinely monitor the prevalence of these resistance genes.

No abstract

Haemophilus parainfluenzae isolates recovered from patients with respiratory diseases were studied for their ability to undergo genetic transformation by isogenic DNA. Two chromosomal markers, streptomycin resistance and nalidixic acid resistance, were tested for transformation efficiencies in H. parainfluenzae recipients from three biotypes. Most efficient in transformation was biotype II, followed by biotype I, while biotype III was nontransformable. Lack of transformation was not owing to poor donor activity of DNA, but to inability of the cells to develop competence. Strains that formed clumps in liquid media were nontransformable. Since the transformable biotype II is one of the prevalent biotypes world wide, one can speculate that DNA transformation probably plays a major role in the spread of drug resistance in H. parainfluenzae.