Outer membrane protein profiles and multilocus enzyme electrophoresis analysis for differentiation of clinical isolates of Proteus mirabilis and Proteus vulgaris

Tandem tetramer-based microsatellite fingerprinting for typing of Proteus mirabilis strains

Two microsatellite tandem repeated tetramers, (GACA)(4) and (CAAT)(4), were used for Proteus mirabilis strain differentiation. The microsatellite-based PCR tests were applied for the examination of interstrain diversity for 87 P. mirabilis strains. Forty-six of the investigated strains were clinical isolates (5 were hospital isolates and 39 were outpatient clinic isolates); 42 strains were derived from the Kauffmann-Perch collection of laboratory strains. Fingerprinting done with the tetramers had a high discrimination ability [0.992 and 0.940 for (GACA)(4) and (CAAT)(4), respectively]. The distributions of clinical isolates among well-defined laboratory strains, determined by numerical analysis (unweighted pair-group method with arithmetic averages; Dice similarity coefficient), proved their genetic similarity to reference strains in the Kauffmann-Perch collection. This analysis also indicated that it is possible to estimate some phenotypic properties of P. mirabilis clinical isolates solely on the basis of microsatellite fingerprinting.

Surface expression of O-specific lipopolysaccharide in Escherichia coli requires the function of the TolA protein

We investigated the involvement of Tol proteins in the surface expression of lipopolysaccharide (LPS). tolQ, -R, -A and -B mutants of Escherichia coli K-12, which do not form a complete LPS-containing O antigen, were transformed with the O7+ cosmid pJHCV32. The tolA and tolQ mutants showed reduced O7 LPS expression compared with the respective isogenic parent strains. No changes in O7 LPS expression were found in the other tol mutants. The O7-deficient phenotype in the tolQ and tolA mutants was complemented with a plasmid encoding the tolQRA operon, but not with a similar plasmid containing a frameshift mutation inactivating tolA. Therefore, the reduction in O7 LPS was attributed to the lack of a functional tolA gene, caused either by a direct mutation of this gene or by a polar effect on tolA gene expression exerted by the tolQ mutation. Reduced surface expression of O7 LPS was not caused by changes in lipid A-core structure or downregulation of the O7 LPS promoter. However, an abnormal accumulation of radiolabelled mannose was detected in the plasma membrane. As mannose is a sugar unique to the O7 subunit, this result suggested the presence of accumulated O7 LPS biosynthesis intermediates. Attempts to construct a tolA mutant in the E. coli O7 wild-type strain VW187 were unsuccessful, suggesting that this mutation is lethal. In contrast, a polar tolQ mutation affecting tolA expression in VW187 caused slow growth rate and serum sensitivity in addition to reduced O7 LPS production. VW187 tolQ cells showed an elongated morphology and became permeable to the membrane-impermeable dye propidium iodide. All these phenotypes were corrected upon complementation with cloned tol genes but were not restored by complementation with the tolQRA operon containing the frameshift mutation in tolA. Our results demonstrate that the TolA protein plays a critical role in the surface expression of O antigen subunits by an as yet uncharacterized involvement in the processing of O antigen.

Potential virulence factors of Proteus bacilli

The object of this review is the genus Proteus, which contains bacteria considered now to belong to the opportunistic pathogens. Widely distributed in nature (in soil, water, and sewage), Proteus species play a significant ecological role. When present in the niches of higher macroorganisms, these species are able to evoke pathological events in different regions of the human body. The invaders (Proteus mirabilis, P. vulgaris, and P. penneri) have numerous factors including fimbriae, flagella, outer membrane proteins, lipopolysaccharide, capsule antigen, urease, immunoglobulin A proteases, hemolysins, amino acid deaminases, and, finally, the most characteristic attribute of Proteus, swarming growth, enabling them to colonize and survive in higher organisms. All these features and factors are described and commented on in detail. The questions important for future investigation of these facultatively pathogenic microorganisms are also discussed.

A function of 40 kDa outer membrane protein in Serratia marcescens

The function of one of the outer membrane proteins of Serratia marcescens was investigated. S. marcescens with an abundant 40 kDa outer membrane protein was induced to form spheroplast at a high rate in an isotonic medium in the presence of calcium, although the spheroplasts were generally fragile in the isotonic environment. The degree of spheroplast induction was correlated to the amount of the 40 kDa protein present in the membrane. In the 40 kDa proteinless mutant strains, the spheroplast induction rate was remarkably decreased. Autoradiography of the outer membrane revealed the presence of a calcium-binding protein as a radioactive band whose position coincided with the 40 kDa protein. These results suggest that the 40 kDa protein has an important role in maintaining the structural integrity of the cell wall against osmotic shock.

Identification and typing of Proteus penneri and Proteus vulgaris biogroups 2 and 3, from clinical sources, by computerized analysis of electrophoretic protein patterns

Seventy-six strains of the Proteus vulgaris complex (Pr. penneri and Pr. vulgaris biogroups 2 and 3) were characterized by one-dimensional SDS-PAGE of cellular proteins. The protein patterns were highly reproducible. The strains came from various countries and were mainly of human origin: urine (28), respiratory tract (13), wounds (8), faeces (7), blood (3), miscellaneous sources (6) and unknown sources (11). The patterns of these strains, together with those of the type strains of seven Morganella, Proteus and Providencia species were subjected to two numerical analyses. In the first, in which the principal protein bands (in the 35.0-42.0 kDa range) were excluded, the strains of the Pr. vulgaris complex formed four clusters at the 83% similarity level. These corresponded to Pr. penneri, Pr. vulgaris biogroup 2, and two clusters (3a and 3b) represented biogroup 3. Each of these clusters was distinct from the Morganella, Proteus and Providencia reference strains. In the second analysis, which included all the protein bands, the 41 Pr. penneri strains showed little heterogeneity but 17 subphenons could be recognized among the 35 strains of Pr. vulgaris biogroups 2 and 3. These results support the division of biogroup 3 strains into at least two separate taxa. Other results indicate that biogroup 3 is heterogeneous and may contain further genomic groups. The method also provides a basis for typing clinical strains of Pr. vulgaris biogroups 2 and 3.

Arbitrarily primed polymerase chain reaction provides rapid differentiation of Proteus mirabilis isolates from a pediatric hospital

During a systematic survey, maternal carriage of Proteus mirabilis was found over a 25-day period in 18 pregnant women admitted to the delivery ward of our hospital maternity. Five neonates born to these mothers were found to be colonized with P. mirabilis. We report here on the use of DNA fingerprinting by the arbitrarily primed polymerase chain reaction technique (AP-PCR) for the epidemiological investigation of this sudden outbreak. This approach was compared with the analysis of restriction fragment length polymorphisms of ribosomal DNA regions (ribotyping). Results of the AP-PCR and of ribotyping were in complete agreement in showing the genetic unrelatedness of the isolates obtained from each mother. Moreover, the results showed mother-to-infant vertical transmission of P. mirabilis in the neonates. AP-PCR is a rapid and discriminative method which seems particularly well suited to the epidemiological study of P. mirabilis.