Factors that influence the interaction of Campylobacter jejuni with cultured mammalian cells.

Although Campylobacter jejuni is now recognised as a common enteric pathogen, the mechanisms by which this organism produces enteritis remain ill-defined. It has been proposed that its abilities to adhere to and enter epithelial cells represent properties essential to virulence. However, the characteristics of these interactions and factors that may influence the association of C. jejuni with epithelial cells are incompletely described. We have determined that the ability of C. jejuni to bind to epithelial cell lines in vitro is significantly affected by the growth temperature and growth stage of the bacteria, but not by growth-medium composition. Binding of C. jejuni to cultured cells is not affected by temperature or phylogenetic origin of the target cell, and exhibits a non-uniform or patchy distribution. In contrast, internalisation is markedly diminished at low temperature, appears to involve active invagination of the target cell membrane via pseudopod formation, and is maximal when cells of human origin are employed.

Group B streptococcal opacity variants.

Colony opacity variants were detected for type III group B streptococci (GBS). Transparent colonies predominate in the parent GBS, with occasional colonies having opaque portions. Two stable opaque variants (1.1 and 1.5) were compared with three transparent clones (1.2, 1.3, and 1.4). All grew well on blood agar and on GC medium, but variant 1.1 failed to grow on Todd-Hewitt medium. Scanning and transmission electron microscopy demonstrated that colony opacity correlated with bacterial aggregation status, with opaque variants forming longer and more organized chains. Opaque-transparent switches were observed in both directions for most variants, with transparent to opaque noted most frequently, but 1.5 did not switch at all. Switching of the opacity phenotype was observed both in vitro and in neonatal mice. Relationships between colony opacity and several cell surface phenomena were explored. (i) Opaque variant 1.1 had two surface proteins (46 and 75 kDa) that were either unique or greatly overexpressed. (ii) Variant 1.1 was deficient in type III polysaccharide, while 1.5 lacked group B antigen. Diminished capsular polysaccharide of variant 1.1 was reflected in reduced negative electrophoretic mobility and in increased buoyant density. (iii) Transparent variant colonies growing closest to a penicillin disk were opaque, but colonial variants did not differ in their sensitivity to penicillin. These data indicate that GBS can exist in both opaque and transparent forms, with opaque appearance occurring by multiple routes. Opaque variants grow poorly on Todd-Hewitt medium generally used for isolation of GBS, so any possible relationships between opacity variation and pathogenesis of GBS infection are unknown.

Argas (Argas) monolakensis, new species (Acari: Ixodoidea: Argasidae), a parasite of California gulls on islands in Mono Lake, California: description, biology, and life cycle.

Argas (Argas) monolakensis, n. sp., is described from adults, nymphs, and larvae collected from under and around nests of California gulls, Larus californicus Lawrence, on islands in Mono Lake, Mono County, Calif., and from specimens reared in the laboratory. This species is closely related to A. cooleyi Kohls & Hoogstraal, a parasite of cliff swallows, Hirundo pyrrhonota Vieillot, but is easily distinguished by hypostome dentition and roof of Haller's organ in all stages and chaetotaxy of the larvae. This tick was successfully reared and maintained in the laboratory by feeding them on domestic chickens. Larvae require 5-8 d to feed, whereas all postlarval stages feed rapidly within 9-62 min. At Mono Lake, ticks are above ground and seek hosts only at night. The number of nymphal stages varies from 2 to 5 depending on the developmental temperature and sex of the tick. Ticks over winter at Mono Lake as second- to fifth-stage nymphs and adults. Ovarian diapause is common with preoviposition periods in extreme cases lasting up to 20 mo. This tick will readily feed on humans and has the potential to transmit Mono Lake virus, which has been isolated from an estimated 2-8% of ticks on various islands. To date, A. monolakensis is known only from islands in Mono Lake, Calif.

Structural features of Borrelia burgdorferi--the Lyme disease spirochete: silver staining for nucleic acids.

Borrelia burgdorferi--the Lyme disease spirochete--was grown in modified Kelly medium and characterized by transmission and by scanning electron microscopy. Using silver staining procedures which preferentially bind to nuclear components of eukaryotic cells, signal could be detected by backscattered electron imaging throughout the length of the prokaryotic spirochete. Interestingly, however, the highest levels of backscattered signal were observed in naturally elaborated membrane blebs that were visible attached to cell surfaces and free in the medium. These membrane vesicles could be enriched by filtration through nitrocellulose or Anopore membranes and by differential centrifugation. The possibility of contaminating cellular DNA coating the membrane vesicles was ruled out by exhaustive digestion with pancreatic DNAse I. Intact DNA was demonstrated both by lysing blebs directly on the surface of microscope grids and by extracting molecules from purified bleb preparation with detergents and solvents. Both linear and circular DNA molecules could be identified in purified membrane blebs. A simple, one-step, alternative silver staining procedure is described which appears to effectively label the protein-nucleic acid complexes contained in the membrane vesicles of the human pathogen B. burgdorferi, and may provide an important method to track and to define the biological function of these structures.

Bat ticks of the genus Argas (Ixodoidea: Argasidae). 13. Haller's organ roof and anterior pit setae in Carios and Chiropterargas.

Adults of 4 of the 6 species constituting the subgenus Carios and of 3 of the 4 species constituting the subgenus Chiropterargas were studied by scanning electron microscopy. All species parasitize Old World cave-dwelling insectivorous bats (Microchiroptera). The anterior pit setae number 10 in Carios and 10 or 11 in Chiropterargas. In most Carios, the setiform seta is replaced by a second serrate seta. In 2 of the 3 studied Chiropterargas species, 1 of the 2 grooved setae is exceptionally long. Porose setae number 3 in Carios and 3 or 4 in Chiropterargas. The Haller's organ roof in both subgenera is solid, lacking perforations; the aperture is narrowly transverse in Carios, irregularly wide or wide and transverse in Chiropterargas; uniquely, 1 or 2 sensilla protrude from the aperture of Chiropterargas species. The protruding sensilla and long grooved seta of Chiropterargas suggest a probably distinctive sensory-behavior pattern common to these ticks. Other morphological characters are discussed and compared to show relationships between these 2 subgenera and the subgenera Argas and Persicargas and distinctive characters present only in adult and/or larval Carios and Chiropterargas.

Observations on the subgenus Argas (Ixodoidea: Argasidae: Argas). 18. Haller's organ roof and anterior pit setae.

Adults of 18 of the 22 species constituting the subgenus Argas, which parasitize birds nesting and resting in rocky habitats in each faunal region of the world (15 species) or in trees (e species) (2 Neotropical, 1 Nearctic), were studies by SEM. In each except three Neotropical species, the nine setae of the anterior pit of tarsus I are arranged in an anterior group (1 serrate, 1 setiform, 1 conical) and a posterior group (2 fine, e porose, 2 grooved), or the two groups are more or less confluent. Abnormally, additional setae may occur on one or both tarsi of a single specimen. In one Neotropical species, only the three anterior group setae are present. In three Neotropical species, only these three setae and a fourth seta are present (whether 6 or 5 additional setae are concealed within the tarsal structure should be investigated). The Haller's organ capsule is entirely open (unroofed) (3 species), roofed posteriorly and open anteriorly (7 species), or mostly roofed by a plate which is pierced by one large aperture and by more or less numerous, small, or medium-sized perforations (8 species plus one other not studied by use). This study suggests that the structure of Haller's organ has evolved in different lines in response to a multiplicity of biologic al factors related to the behavior and habitat of individual species.

Rhipicephalus zambeziensis sp. Nov., a new tick from eastern and southern africa, together with a redescription of Rhipicephalus appendiculatus Neumann, 1901 (Acarina, Ixodidae).

All stages of Rhipicephalus zambeziensis sp. nov. are described from laboratory-reared specimens of a strain originating from cattle near West Nicholson, Gwanda District, Zimbabwe. The redescription of all stages of Rhipicephalus appendiculatus is based primarily on laboratory-reared specimens of a strain originating from a mountain reedbuck (Redunca fulvorufula), Loskop Dam Nature Reserve, Transvaal, Republic of South Africa. The differences between these 2 species are discussed briefly. Details of the life cycle of R. zambeziensis under laboratory conditions are given, and attempts to cros-breed this species with R. appendiculatus are described and discussed.