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Biomedical subjects

T J Rowbotham

Publications and source records attributed to T J Rowbotham.

17 recordsLinked to original sources
PubMed2000

Survival and growth of Burkholderia cepacia within the free-living amoeba Acanthamoeba polyphaga.

The aim of this study was to investigate whether Burkholderia cepacia is capable of survival and growth within the free-living amoeba Acanthamoeba polyphaga using a differential immunofluorescence assay of bacterial-amoebal cocultures and viable counts of bacteria determined after amoebal lysis. The numbers of intra-amoebal bacteria and the numbers of infected amoebae increased over time; although, when heat-killed bacteria were used, no intracellular bacteria were observed. These findings should be taken into account in future studies of environmental reservoirs of Burkholderia cepacia.

Acanthamoeba↗
PubMed2000

'Candidatus Odyssella thessalonicensis' gen. nov., sp. nov., an obligate intracellular parasite of Acanthamoeba species.

An intracellular bacterium, strain L13, was observed infecting an environmental isolate of an Acanthamoeba species. The bacterium could not be recovered on axenic medium but was recovered and cultivated in vitro using cultures of Acanthamoeba polyphaga. The 16S rRNA gene sequence of L13 was found to be new, sharing less than 84% similarity with other sequences in the GenBank/EMBL database. L13 was found to be a member of the alpha-Proteobacteria, sharing an evolutionary line of descent with a group of uniquely obligate intracellular organisms comprised of Caedibacter and Holospora species and the NHP bacterium. Viable bacteria appeared to be highly motile within amoebae. Ultrastructural analysis of the bacterium demonstrated that it is rod-shaped and possesses a typical Gram-negative cell wall, but has no other outstanding features except small vesicle-like structures often associated with the outer surface of each bacterium. The host range of L13 was found to be limited to the genus Acanthamoeba. In A. polyphaga, L13 infection was slow to manifest when cultures were incubated below 30 degrees C, but at higher temperatures bacteria multiplied prolifically and induced host cell lysis. The protein profile of the bacterium purified from the amoebae was assessed by SDS-PAGE and its G+C content was estimated to be 41 mol%. Although these results support the proposal of L13 as a new species, its obligate intracellular nature prevented isolation of a definitive type strain. L13 is therefore proposed as 'Candidatus Odyssella thessalonicensis' gen. nov., sp. nov.

Acanthamoeba↗
PubMed1998

Legionellosis associated with ships: 1977 to 1997.

Over one hundred cases of legionnaires' disease have been linked to ships, and ten cases are known to have died. Most of the cases were associated with cruise ships, but a variety of other vessels were also linked to cases. Few vessels were investigated microbiologically, and the cases associated with ferries were exposed to other sources of infection. Cases appear to be less common among crew members than among passengers. To prevent further cases, ship owners, operators, and captains need to be diligent in maintaining the water and air conditioning systems of their vessels. Whirlpool spas need particular care. Ship-associated cases of non-pneumonic legionellosis appear to be rare.

Humans↗
PubMed1996

Phylogenetic diversity of intra-amoebal legionellae as revealed by 16S rRNA gene sequence comparison.

Following a recent phylogenetic analysis of all 39 species of the genus Legionella and related organisms, the name Legionella lytica has been proposed for bacteria previously considered either as Sarcobium lyticum or as 'Legionella-like amoebal pathogens' (LLAPs). To investigate the phylogenetic integrity of this newly proposed species, we determined the 16S rRNA gene sequences of 10 LLAPs isolated from various environmental sources. All 10 isolates clustered within a monophyletic group containing all other members of the genus Legionella. Eight of the 10 isolates formed a monophyletic subgroup within the genus which also included the two previously characterized L. lytica strains. Four of these 10 isolates shared a specific and very close relationship with the L. lytica type strain (> 99% sequence similarity). However, although clearly legionellae, the remaining two LLAP strains bore no specific evolutionary relationship to either L. lytica or any other Legionella species (< 96% sequence similarity). Both isolates lay on their own relatively deep-rooted branches within the radiation of the Legionella cluster. LLAPs do not, therefore, represent a unique species or even a single line of descent within the genus, and investigation of more isolates may reveal them to be as evolutionarily diverse as the other presently recognized Legionella species.

Acanthamoeba↗
PubMed1991

Direct amplification and sequencing of the 16S ribosomal DNA of an intracellular Legionella species recovered by amoebal enrichment from the sputum of a patient with pneumonia.

DNA coding for the 16S rRNA of an intracellular bacterium was directly amplified from lysed cells of a host amoebae using the polymerase chain reaction and primers specific for eubacteria. The amoebae had been used to recover an uncultured bacterium observed in the sputum of a patient with pneumonia. The amplified DNA was sequenced directly and compared with published 16S rRNA sequences. The analysis revealed that the intracellular bacterium is a member of the genus Legionella and that it is different from species, including L. pneumophila, for which 16S ribosomal RNA sequence data are available.

Acanthamoeba↗
PubMed1990

Microbiological investigations into an outbreak of Pontiac fever due to Legionella micdadei associated with use of a whirlpool.

In the investigation of a large outbreak of non-pneumonic legionellosis at a leisure complex in Lochgoilhead, Scotland all direct cultures of environmental samples were initially negative for legionellae. Legionellae readily infect appropriate protozoa under suitable conditions, and following immunofluorescence to select specimens for special study, Legionella micdadei was isolated from whirlpool water via co-cultivation with Acanthamoeba polyphaga. L micdadei was also isolated, along with host amoebae, from the whirlpool filter. The use of amoebae in the isolation of legionellae from environmental (and other) sources can be of great value, especially if specimens shown by indirect immunofluorescence to contain legionellae fail to yield legionellae on routine culture.

Acanthamoeba↗
PubMed1986

Current views on the relationships between amoebae, legionellae and man.

Amoebae are natural hosts for legionellae. The significance of this with regard to the multiplication of legionellae in the environment, the protection of legionellae from biocides, and the epidemiology of Legionnaires' Disease and Pontiac fever are discussed. A vesicle, or small amoeba, containing many legionellae is suggested as the main infective particle for man. We believe Pontiac fever can be explained as involving hypersensitivity to acanthamoebae, and comment on the lack of phages for legionellae. Legionella-like amoebal pathogen 1 (LLAP-1) was isolated, and probably belongs to a new species of Legionella. Further amoebal hosts for legionellae were found.

Amoeba↗
PubMed1983

Isolation of Legionella pneumophila from clinical specimens via amoebae, and the interaction of those and other isolates with amoebae.

The development of an amoebal enrichment method, for the recovery of viable Legionella pneumophila from clinical materials is described. The method has been used successfully in five of six cases of Legionnaires' disease in which L pneumophila was isolated. Studies on those L pneumophila isolates led to the discovery that virulent legionellae are attracted to, and attack suitable host amoebae, rather than infection following chance ingestion.

Aged↗
PubMed1980

Preliminary report on the pathogenicity of Legionella pneumophila for freshwater and soil amoebae.

Legionella pneumophila, the causative organism of Legionnaires' disease, is pathogenic for free living, ubiquitous, freshwater, and soil amoebae of the genera Acanthamoeba and Naegleria. Some species support the growth of strains from serogroups 1 to 6, others only strains from certain serogroups. Initial studies with seeded material indicate that amoebal enrichment could be utilised for the isolation of legionellae from clinical specimens and natural habitats. It is suggested that a vacuole, or amoeba, full of legionellae, rather than free legionellae, could be the infective particle for man.

Amoeba↗