Differentiation of Bartonella species by a microimmunofluorescence assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western immunoblotting

Bacterial Whole Cell Protein Profiling: Methodology, Applications and Constraints

Background:

In the era of modern microbiology, several methods are available for identification and typing of bacteria, including whole genome sequencing. However, in microbiological laboratories or hospitals where genomic based molecular typing methods and/or trained manpower are unavailable, whole cell protein profiling using sodium dodecyl sulfate polyacrylamide gel electrophoresis might be a useful alternative/supplementary method for bacterial identification, strain typing and epidemiology. Whole cell protein profiling by SDS-PAGE is based on the principle that under standard growth conditions, a bacterial strain expresses the same set of proteins, the pattern of which can be used for bacterial identification.

Objective:

The objective of this review is to assess the current status of whole cell protein profiling by SDS-PAGE and its advantages and constraints for bacterial identification and typing.

Results and Conclusions:

Several earlier and recent studies prove the potential and utility of this technique as an adjunct or supplementary method for bacterial identification, strain typing and epidemiology. There is no denying the fact that utility of this technique as an adjunct or supplementary method for bacterial identification and typing has already been demonstrated and its practical applications need to be evaluated further.

Bartonella Species, an Emerging Cause of Blood-Culture-Negative Endocarditis

Since the reclassification of the genus Bartonella in 1993, the number of species has grown from 1 to 45 currently designated members. Likewise, the association of different Bartonella species with human disease continues to grow, as does the range of clinical presentations associated with these bacteria. Among these, blood-culture-negative endocarditis stands out as a common, often undiagnosed, clinical presentation of infection with several different Bartonella species. The limitations of laboratory tests resulting in this underdiagnosis of Bartonella endocarditis are discussed. The varied clinical picture of Bartonella infection and a review of clinical aspects of endocarditis caused by Bartonella are presented. We also summarize the current knowledge of the molecular basis of Bartonella pathogenesis, focusing on surface adhesins in the two Bartonella species that most commonly cause endocarditis, B. henselae and B. quintana. We discuss evidence that surface adhesins are important factors for autoaggregation and biofilm formation by Bartonella species. Finally, we propose that biofilm formation is a critical step in the formation of vegetative masses during Bartonella-mediated endocarditis and represents a potential reservoir for persistence by these bacteria.

High prevalence of fastidious bacteria in 1520 cases of uveitis of unknown etiology

The etiologic evaluation of uveitis is frequently unsuccessful when noninvasive methods are used. We conducted a prospective study to evaluate systematic screening for pathogens of uveitis. All patients with uveitis referred to the participating tertiary ophthalmology departments from January 2001 to September 2007 underwent intraocular and serum specimen collection. The standardized protocol for laboratory investigations included universal polymerase chain reaction (PCR)-based detection of any bacteria and mycoses, specific PCR-based detection of fastidious (difficult-to-grow) bacteria and herpes viruses, and culture of vitreous fluid. Sera were tested for fastidious bacteria. Among the 1321 included patients (1520 specimens), infection was diagnosed in 147 (11.1%) patients: 78 (53%) were caused by fastidious bacteria that included spirochetes, Bartonella species, intracellular bacteria (Chlamydia species, Rickettsia species, Coxiella burnetii), and Tropheryma whipplei; 18 by herpes viruses; and 9 by fungi. Bartonella quintana, Coxiella burnetii, Paracoccus yeei, Aspergillus oryzae, and Cryptococcus albidus were found to be associated with uveitis for the first time, to our knowledge. We recommend applying a 1-step diagnostic procedure that incorporates intraocular, specific microbial PCR with serum analyses in tertiary centers to determine the etiology of uveitis.

The Bartonella henselae sucB gene encodes a dihydrolipoamide succinyltransferase protein reactive with sera from patients with cat-scratch disease

Bartonella henselae is a recently recognized pathogenic bacterium associated with cat-scratch disease, bacillary angiomatosis and bacillary peliosis. A recombinant clone expressing an immunoreactive antigen of B. henselae was isolated by screening a genomic DNA cosmid library by Western blotting with sera pooled from patients positive for B. henselae IgG antibodies by indirect immunofluorescence (IFA). The deduced amino acid sequence of the 43.7 kDa encoded protein was found to be 76.3 % identical to the dihydrolipoamide succinyltransferase enzyme (SucB) of Brucella melitensis. SucB has been shown to be an immunogenic protein during infections by Brucella melitensis, Coxiella burnetii and Bartonella vinsonii. The agreement between reactivity with a recombinant SucB fusion protein on immunoblot analysis and the results obtained by IFA was 55 % for IFA-positive sera and 88 % for IFA-negative sera. Cross-reactivity was observed with sera from patients with antibodies against Brucella melitensis, Mycoplasma pneumoniae, Francisella tularensis, Coxiella burnetii and Rickettsia typhi.

A review of bacterial pathogens inCtenocephalides felisin New Zealand

The cat flea, Ctenocephalides felis, is the recognised vector of Bartonella henselae, B. clarridgeiae and Rickettsia felis. Although these Gram-negative bacteria were only described in the last decade, they are already known to cause a variety of diseases in people, particularly children and the immunosuppressed. Such diseases include cat-scratch disease, bacillary angiomatosis, endocarditis, bacteraemia, encephalopathy, neuroretinitis, osteomyelitis and peliosis hepatis. Although most infections in cats and dogs appear to be subclinical, recent studies have provided growing evidence that the bartonellas can also cause serious problems in pets, including hepatitis, endocarditis, central nervous system (CNS) signs, lymphadenopathy, uveitis, cataracts and reproductive failure. In 2004, DNA of B. henselae, B. clarridgeiae and R. felis was demonstrated in cat fleas from New Zealand and pets and their owners in the country are thus at risk of infection. While flea control programmes have traditionally been advocated by veterinarians to prevent pruritus and tapeworms in pets, they should now also be recommended to prevent infections with the new flea-borne bacterial pathogens. To raise awareness of the organisms amongst veterinarians and animal health workers, this review describes: the biology of the organisms; clinical and laboratory features of infections in cats, dogs and people; diagnosis; and possible treatments and control of infections with these organisms.

Molecular characterization of the sucB gene encoding the immunogenic dihydrolipoamide succinyltransferase protein of Bartonella vinsonii subsp. berkhoffii and Bartonella quintana

Members of the genus Bartonella have historically been connected with human disease, such as cat scratch disease, trench fever, and Carrion's disease, and recently have been recognized as emerging pathogens causing other clinical manifestations in humans. However, because little is known about the antigens that elicit antibody production in response to Bartonella infections, this project was undertaken to identify and molecularly characterize these immunogens. Immunologic screening of a Bartonella vinsonii subsp. berkhoffii genomic expression library with anti-Bartonella antibodies led to the identification of the sucB gene, which encodes the enzyme dihydrolipoamide succinyltransferase. Antiserum from a mouse experimentally infected with live Bartonella was reactive against recombinant SucB, indicating the mounting of an anti-SucB response following infection. Antigenic cross-reactivity was observed with antiserum against other Bartonella spp. Antibodies against Coxiella burnetti, Francisella tularensis, and Rickettsia typhi also reacted with our recombinant Bartonella SucB. Potential SucB antigenic cross-reactivity presents a challenge to the development of serodiagnostic tests for other intracellular pathogens that cause diseases such as Q fever, rickettsioses, brucelloses, tularemia, and other bartonelloses.

Western immunoblotting for Bartonella endocarditis

To differentiate infectious endocarditis (IE) from other Bartonella infections and to identify infecting Bartonella bacteria at the species level on a serological basis, we used Western immunoblotting to test sera from 51 patients with Bartonella IE (of which 27 had previously benefited from species identification by molecular techniques), 11 patients with chronic Bartonella quintana bacteremia, and 10 patients with cat scratch disease. Patients with IE were Western blot positive in 49 of 51 cases, and significant cross-reactivity with three heterologous Bartonella antigens was found in 45 of 49 cases. Sera from bacteremic patients did not react with more than one heterologous antigen, and sera from patients with cat scratch disease gave negative results. Sera reacted only with B. henselae in four cases of IE, including one with a positive PCR result for valve tissue. Western blot and cross-adsorption performed on serum samples from patients with IE (the identity of the causative species having been determined by PCR) were demonstrated to identify efficiently the causative species in all cases. When applied to patients diagnosed on the basis of serological tests only, this technique allowed identification of the causative species in 20 of 22 cases. The results were in accordance with epidemiological features. Six reactive bands of B. quintana (of molecular sizes from 10 to 83 kDa) demonstrated significant association with sera from patients with B. quintana endocarditis. Overall, Western blotting and cross-adsorption made it possible to identify the causative species in 49 of 51 (96%) IE cases.

Genotypic characteristics of two serotypes of Bartonella henselae

The study of 16S rRNA gene sequences of all isolates of Bartonella henselae obtained in our laboratory and others from human patients or cats has revealed two genotypes according to the sequence of the 16S rRNA gene. Two isolates of these genotypes have previously been related to two different serotypes, and lack of cross-protection of the two serotypes has been demonstrated in cats. We investigated the grouping of eight strains of B. henselae on the basis of 16S ribosomal DNA, 35-kDa protein, Pap 31 protein, and internal transcribed spacer (ITS) gene sequencing; sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles; and monoclonal antibody reactivity studies. Houston-1, 90-615, and SA2 strains showed the same patterns in SDS-PAGE, but they differed from the patterns of B. henselae isolates URBHLLY8, URBHLIE9, Cat6, Fizz, and CAL-1. Nine monoclonal antibodies derived from BALB/c mice immunized with B. henselae Houston-1 strain reacted only with strains Houston-1, 90-615, and SA2, and not with any other Bartonella strains. The two serogroups corresponded with two genotypes based on differences in the sequences of the genes encoding 16S rRNA, 35-kDa protein, and Pap 31 protein. Sequences of ITS genes were highly divergent among strains, as each had a unique sequence and the subdivision was not supported by DNA-DNA relatedness study. Study of 22 additional strains of B. henselae isolated from French bacteremic cats demonstrated that they all belong to one or the other of the proposed serotype or genotype.