Our aim was to determine if the detection rate of infection of total hip replacements could be improved by examining the removed prostheses. Immediate transfer of prostheses to an anaerobic atmosphere, followed by mild ultrasonication to dislodge adherent bacteria, resulted in the culture of quantifiable numbers of bacteria, from 26 of the 120 implants examined. The same bacterial species were cultured by routine microbiological techniques from only five corresponding tissue samples. Tissue removed from 18 of the culture-positive implants was suitable for quantitative tissue pathology and inflammatory cells were present in all samples. Furthermore, inflammatory cells were present in 87% of tissue samples taken from patients whose implants were culture-negative. This suggests that these implants may have been infected by bacteria which were not isolated by the techniques of culture used. The increased detection of bacteria from prostheses by culture has improved postoperative antibiotic therapy and should reduce the need for further revision.

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In this study the detection rates of bacterial infection of hip prostheses by culture and nonculture methods were compared for 120 patients with total hip revision surgery. By use of strict anaerobic bacteriological practice during the processing of samples and without enrichment, the incidence of infection by culture of material dislodged from retrieved prostheses after ultrasonication (sonicate) was 22%. Bacteria were observed by immunofluorescence microscopy in 63% of sonicate samples with a monoclonal antibody specific forPropionibacterium acnes and polyclonal antiserum specific for Staphylococcus spp. The bacteria were present either as single cells or in aggregates of up to 300 bacterial cells. These aggregates were not observed without sonication to dislodge the biofilm. Bacteria were observed in all of the culture-positive samples, and in some cases in which only one type of bacterium was identified by culture, both coccoid and coryneform bacteria were observed by immunofluorescence microscopy. Bacteria from skin-flake contamination were readily distinguishable from infecting bacteria by immunofluorescence microscopy. Examination of skin scrapings did not reveal large aggregates of bacteria but did reveal skin cells. These were not observed in the sonicates. Bacterial DNA was detected in 72% of sonicate samples by PCR amplification of a region of the bacterial 16S rRNA gene with universal primers. All of the culture-positive samples were also positive for bacterial DNA. Evidence of high-level infiltration either of neutrophils or of lymphocytes or macrophages into associated tissue was observed in 73% of patients. Our results indicate that the incidence of prosthetic joint infection is grossly underestimated by current culture detection methods. It is therefore imperative that current clinical practice with regard to the detection and subsequent treatment of prosthetic joint infection be reassessed in the light of these results.

Phytoplasmas were found in 33 plant species that were not described as host plants in an earlier Australian survey. Plants displayed characteristic symptoms of little leaf, proliferation, and floral abnormalities. Restriction fragment length polymorphism analysis revealed 13 different restriction patterns. The majority of phytoplasmas showed a restriction pattern identical to that of either the tomato big bud (TBB) or sweet potato little leaf V4 (SPLL-V4) phytoplasma. Phytoplasmas from 6 plant species showed a restriction pattern similar to that of the pigeonpea little leaf (PLL) phytoplasma. One phytoplasma from garden bean displayed a restriction pattern identical to that found in papaya dieback and Australian grapevine yellows (AGY) phytoplasmas. Seven new restriction fragment patterns have been detected and sequence analysis of the 16S/23S spacer region revealed that 3 of these phytoplasmas are related to the faba bean phyllody (FBP) group. The spacer region of a graminaceous phytoplasma was most similar to phytoplasmas from the sugarcane white leaf group. Another graminaceous phytoplasma was identical to a phytoplasma from Indonesia. The spacer region of a phytoplasma from poinsettia (PoiBI) was identical to the western X-disease phytoplasma from North America and Europe. The spacer region of a phytoplasma in stylosanthes contained no tRNAIle. Full-length 16S rRNA gene sequences from selected new phytoplasmas were determined to corroborate results obtained from the spacer region analyses. Three of these phytoplasmas (galactia little leaf, vigna little leaf, and stylosanthes little leaf) are, along with the PoiBI phytoplasma and the graminaceous phytoplasmas, members of phytoplasma groups that have not been reported before in Australia.