Chlorhexidine resistance in Proteus mirabilis

A total of 104 clinical isolates of Pr. mirabilis from three hospitals were screened for their sensitivity to chlorhexidine. The minimum inhibitory concentrations of the antiseptic for these strains ranged from 10 to 800 mug/ml. Two strains sensitive to 20 mug of chlorhexidine/ml were adapted to resistance by growth in subinhibitory concentrations of the antiseptic, their MIC values increasing to 200 and 800 mug/ml. These derived strains exhibited slightly reduced sensitivity to cetrimide and benzalkonium chloride. The chlorhexidine-resistant clinical isolates also exhibited this partially decreased sensitivity to the quaternary ammonium compounds. Both the chlorhexidine-sensitive and -resistant strains were uniformly sensitive to chloroxylenol (Dettol), glutaraldehyde, and 2-phenoxyethanol.     

Uropathogenic properties of Proteus mirabilis and Proteus vulgaris

A group of faecal isolates of Proteus vulgaris and P. mirabilis was studied for the presence of possible virulence factors such as growth rates in urine and broth, haemolysin production, hydrophobicity, sensitivity to the bactericidal activity of human serum and cell invasiveness. Differences were found in haemolysin production, cell invasiveness and experimental virulence in a mouse model. These differences might explain why P. mirabilis is much more common in human urinary-tract infections than P. vulgaris.     

ECA-immunogenicity of Proteus mirabilis strains

Introduction  Bacteria of the genus Proteus are opportunistic pathogens and cause mainly urinary tract infections. They also play a role in the pathogenesis of reactive arthritis (RA). Patients suffering from Yersinia-triggered RA often carry high titers of antibodies specific to enterobacterial common antigen (ECA). The immunogenicity of ECA has not received much attention thus far and studies have focused mainly on the ECA of Escherichia coli and Yersinia enterocolitica. In this paper the ECA-immunogenicity of Proteus mirabilis is elucidated using two wild-type strains (S1959 and O28) as well as their rough (R) derivative strains R110/1959, which expresses lipopolysaccharide (LPS) with a full core, and R4/O28, which expresses LPS with only an inner core. Materials and Methods  Rabbit polyclonal antisera were produced by immunization with boiled suspensions of the four P. mirabilis strains. The antisera were tested for the presence of antibodies specific to ECA by Western blotting using glycerophospholipid- linked ECA (ECA _PG ) of Salmonella montevideo as antigen. Lipopolysaccharide (LPS) was isolated from the four strains by the hot phenol/water procedure in which ECA _PG is co-extracted with LPS and by the phenol/chloroform/petroleum ether extraction that results in the isolation of LPS and/or LPS-linked ECA (ECA _LPS ) free of ECA _PG . The LPS preparations were tested for the presence of ECA by Western blotting using ECA-specific antibodies. Results  The results demonstrated that all four P. mirabilis strains were ECA immunogenic. The rabbit antisera immunized by the four strains all contained ECA-specific antibodies. Analysis of the LPS preparations demonstrated that the P. mirabilis wild-type strains O28 and S1959 and the Ra mutant strain R110/1959 expressed ECA _LPS , suggesting that it induced the anti-ECA antibody responses. Only the presence of ECA _PG could be demonstrated in the Rc mutant strain R4/O28. Conclusions  These results therefore suggest that, similar to E. coli, LPS with a full core is also required as the acceptor of ECA for P. mirabilis strains to produce ECA _LPS . Since ECA _PG is not immunogenic unless combined with some proteins, it is likely that ECA _PG -protein complexes formed during the intravenous immunization with the Rc mutant strain R4/O28.     

Emerging extended-spectrum beta-lactamases in Proteus mirabilis

Beta-lactamase production was detected in 147 (52%) of 282 consecutive nonduplicate Proteus mirabilis isolates obtained over a 1-year period from the S. Matteo Hospital of Pavia (northern Italy). Seventy isolates (48% of the beta-lactamase producers) were found to produce extended-spectrum beta-lactamases (ESBLs), identified as PER-1 (first report in this species) and TEM-52 in 52 and 18 isolates, respectively. Analysis of clonal diversity of the ESBL producers suggested different spreading patterns for the two ESBL determinants.     

Cell invasiveness of Proteus mirabilis and Proteus vulgaris strains

Cell penetration ability of haemolytic and non haemolytic Proteus rods was compared. Among four Proteus strains all were able to invade the tested cells (Vero 135, HeLa, L-929 and human blood lymphocytes) but the expression of this feature by haemolytic strains was markedly higher. The survival and multiplication of intracellular bacteria, especially in the case of fresh human blood lymphocytes may be of importance for the development of infection in higher organisms.     

Vero cell invasiveness of Proteus mirabilis

Vero cell invasiveness was studied for a group of Proteus mirabilis strains isolated from the urinary tract and feces and for a limited group of urinary isolates of Escherichia coli. Experimental conditions affecting this invasiveness were studied. All of the P. mirabilis strains tested were capable of cell invasion, whereas none of the E. coli strains was. Correlation between the hemolytic activity of the P. mirabilis strains and their invasive ability suggested that the bacterial hemolysin may be involved in the invasion process. Other experimental evidence supporting this hypothesis is discussed. The differences in the invasive capacities of P. mirabilis and of E. coli may be important for the apparent differences in the pathogenesis of urinary tract infection by both species.     

CTX-M-1 extended-spectrum beta-lactamase-producing Proteus mirabilis in Greece

To examine the dissemination of CTX-M-type extended-spectrum beta-lactamases (ESBLs) in clinical isolates of Proteus mirabilis, 91 nonrepetitive ESBL-producing P. mirabilis were collected from infected patients in a tertiary Greek hospital during September, 2001, to May, 2004. A bla (CTX-M) gene was amplified in one isolate (strain A328), but bla (CTX-M) was not detected in any of the remaining ESBL producers. Sequencing results showed that P. mirabilis A328 produced a CTX-M-1 enzyme while PCR mapping of the genetic element carrying bla (CTX-M-1) revealed that the gene was located downstream of an ISEcp1B element. The cefotaxime resistance determinant was easily transferable and carried on a 70-kb plasmid. The emergence of CTX-M-1- producing P. mirabilis indicates the need for early recognition of such strains to be able to control their spread in our hospital and community environment.     

Characterisation of p-nitrophenylglycerol-resistant Proteus mirabilis super-swarming mutants.

p-Nitrophenylglycerol (PNPG) inhibits the co-ordinately regulated activities of swarming behaviour and virulence factor expression in Proteus mirabilis. The inhibitory action of PNPG was investigated by the isolation of Tn5 insertion mutants that could swarm, albeit with much reduced ability, in the presence of PNPG. The mutants exhibited a super-swarming phenotype in the absence of PNPG; i.e., they migrated further in a given time than did the wild-type cells. Cloning and sequence analysis of the mutants indicated that Tn5 was inserted into the rsbA gene, which may encode a membrane sensor histidine kinase of the bacterial two-component signalling system. In the absence of PNPG, the mutants exhibited several swarming-related phenotypes that were different from those of the wild type; they initiated swarming earlier and had a less conspicuous consolidation phase, they differentiated earlier and maintained a differentiated state for longer, they started to express virulence factors earlier and maintained high expression levels of these factors for longer, and they had higher cell invasion ability than the wild type. These mutant phenotypes could be complemented by a plasmid-borne copy of rsbA. Together, these data suggest that RsbA may act as a repressor of swarming and virulence factor expression. In the presence of PNPG, these rsbA-mutated mutants could still swarm, differentiate and express virulence factors, whereas the wild type could not, suggesting that PNPG may target RsbA or RsbA-regulated pathways to exert its inhibitory effect. Together, these data reveal a novel mechanism through which bacteria may negatively regulate swarming differentiation and virulence factor expression and identify a potential target of PNPG action.     

Immunochemical studies on the O-antigens of Proteus mirabilis O23 and Proteus vulgaris O23

Analysis by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy demonstrated that the O-specific polysaccharides of Proteus mirabilis PrK 42/57 and P. vulgaris PrK 43/57 are structurally similar to that of P. vulgaris PrK 44/57 and different from the polysaccharide of P. mirabilis PrK 41/57 studied earlier. The lipopolysaccharides of these strains were tested using enzyme immunosorbent assay, passive hemolysis and Western blot with O-antisera against P. mirabilis 42/57 and P. vulgaris 43/57 and 44/57, as well as with cross-absorbed O-antisera. The chemical and serological data revealed the basis for combining the four strains into Proteus serogroup O23 and division of this serogroup to three subgroups, one for P. vulgaris 43/57 and 44/57 and two others for P. mirabilis 41/57 and 42/57.