No abstract

Rapid and specific detection of pathogenic bacteria is important for the proper treatment, containment and prevention of human, animal and plant diseases. Identifying unique biological probes to achieve a high degree of specificity and minimize false positives has therefore garnered much interest in recent years. Bacteriophages are obligate intracellular parasites that subvert bacterial cell resources for their own multiplication and production of disseminative new virions, which repeat the cycle by binding specifically to the host surface receptors and injecting genetic material into the bacterial cells. The precision of host recognition in phages is imparted by the receptor binding proteins (RBPs) that are often located in the tail-spike or tail fiber protein assemblies of the virions. Phage host recognition specificity has been traditionally exploited for bacterial typing using laborious and time consuming bacterial growth assays. At the same time this feature makes phage virions or RBPs an excellent choice for the development of probes capable of selectively capturing bacteria on solid surfaces with subsequent quick and automatic detection of the binding event. This review focuses on the description of pathogen detection approaches based on immobilized phage virions as well as pure recombinant RBPs. Specific advantages of RBP-based molecular probes are also discussed.

Campylobacter jejuni continues to be the leading cause of bacterial food-borne illness worldwide, so improvements to current methods used for bacterial detection and disease prevention are needed. We describe here the genome and proteome of C. jejuni bacteriophage NCTC 12673 and the exploitation of its receptor-binding protein for specific bacterial detection. Remarkably, the 135-kb Myoviridae genome of NCTC 12673 differs greatly from any other proteobacterial phage genome described (including C. jejuni phages CP220 and CPt10) and instead shows closest homology to the cyanobacterial T4-related myophages. The phage genome contains 172 putative open reading frames, including 12 homing endonucleases, no visible means of packaging, and a putative trans-splicing intein. The phage DNA appears to be strongly associated with a protein that interfered with PCR amplification and estimation of the phage genome mass by pulsed-field gel electrophoresis. Identification and analyses of the receptor-binding protein (Gp48) revealed features common to the Salmonella enterica P22 phage tailspike protein, including the ability to specifically recognize a host organism. Bacteriophage receptor-binding proteins may offer promising alternatives for use in pathogen detection platforms.Campylobacter belongs to the epsilon class of proteobacteria and is the leading cause of bacterial food-borne gastroenteritis worldwide (22). Campylobacter has also been associated with severe neurological disorders such as the Guillain-Barré and Miller-Fisher syndromes, as well as reactive arthritis and irritable bowel syndrome (32). Many Campylobacter phages have been characterized by their host-range characteristics, morphology, genome size, and susceptibility to restriction endonucleases (5,7,24). Only a few of the characterized Campylobacter phages are members of the B1 group of the family Siphoviridae (1), while most belong to the family Myoviridae possessing genomes which fall into three size classes: 110 to 150 kb (class III), 170 to 190 kb (class II), and 320 kb (class I) (24). One interesting characteristic of many of these phages is that their DNA appears to be resistant to cleavage by several common restriction endonucleases, thus making them "refractory to genomic analysis" (34). Two genomes of Campylobacter phages have been sequenced thus far: CPt10 and CP220 (34). Both appear to be closely related to each other and belong to the class II of Campylobacter Myoviridae phage genomes (34).Bacteriophages possess enormous diagnostic and therapeutic potential, which provides promise for the development of a wide range of novel antimicrobials and diagnostic tools (14). Numerous phages have been isolated against Campylobacter for use in phage typing schemes (9,10,12,18,25), but it has only recently been shown that bacteriophages can effectively decrease Campylobacter contamination (4, 20, 36). For example, Campylobacter-specific phages were able to reduce the numbers of Campylobacter coli and Campylobacter jejuni in chickens when added directly to the...