Taxonomy of Australian clinical isolates of the genus Photorhabdus and proposal of Photorhabdus asymbiotica subsp. asymbiotica subsp. nov. and P. asymbiotica subsp. australis subsp. nov.

The relationship of Photorhabdus isolates that were cultured from human clinical specimens in Australia to Photorhabdus asymbiotica isolates from human clinical specimens in the USA and to species of the genus Photorhabdus that are associated symbiotically with entomopathogenic nematodes was evaluated. A polyphasic approach that involved DNA-DNA hybridization, phylogenetic analyses of 16S rRNA and gyrB gene sequences and phenotypic characterization was adopted. These investigations showed that gyrB gene sequence data correlated well with DNA-DNA hybridization and phenotypic data, but that 16S rRNA gene sequence data were not suitable for defining species within the genus Photorhabdus. Australian clinical isolates proved to be related most closely to clinical isolates from the USA, but the two groups were distinct. A novel subspecies, Photorhabdus asymbiotica subsp. australis subsp. nov. (type strain, 9802892T=CIP 108025T=ACM 5210T), is proposed, with the concomitant creation of Photorhabdus asymbiotica subsp. asymbiotica subsp. nov. Analysis of gyrB sequences, coupled with previously published data on DNA-DNA hybridization and PCR-RFLP analysis of the 16S rRNA gene, indicated that there are more than the three subspecies of Photorhabdus luminescens that have been described and confirmed the validity of the previously proposed subdivision of Photorhabdus temperata. Although a non-luminescent, symbiotic isolate clustered consistently with P. asymbiotica in gyrB phylogenetic analyses, DNA-DNA hybridization indicated that this isolate does not belong to the species P. asymbiotica and that there is a clear distinction between symbiotic and clinical species of Photorhabdus.

Recurrent Achromobacter piechaudii bacteremia in a patient with hematological malignancy.

We describe a recurrent bacteremia caused by Achromobacter (formerly Alcaligenes) piechaudii in association with an intravenous catheter in an immunocompromised 73-year-old man. This is the first reported case of bacteremia due to A. piechaudii.

Isolation, identification, and molecular characterization of strains of Photorhabdus luminescens from infected humans in Australia.

We describe the isolation of Photorhabdus (Xenorhabdus) luminescens from four Australian patients: two with multiple skin lesions, one with bacteremia only, and one with disseminated infection. One of the patients had multiple skin lesions following the bite of a spider, while the lesions in the other patient were possibly associated with a spider bite. The source of infection for the remaining two patients is unknown. As a member of the family Enterobacteriaceae, P. luminescens is unusual in that it fails to reduce nitrate and ferments only glucose and mannose. It gives negative reactions for lysine decarboxylase, arginine dihydrolase, and ornithine decarboxylase (Moeller). The species is motile, utilizes citrate, hydrolyzes urea, and usually produces a unique type of annular hemolysis on sheep blood agar plates incubated at 25 degrees C. A weak bioluminescence is the defining characteristic. P. luminescens is an insect pathogen and is symbiotically associated with entomopathogenic nematodes. Its isolation from human clinical specimens has been reported previously from the United States. Restriction fragment length polymorphism-PCR analysis of the 16S rRNA gene demonstrated a high level of similarity among the Australian clinical strains and significant differences between the Australian clinical strains and the U.S. clinical strains. However, numerical analyses of the data suggest that the two groups of clinical strains are more similar to each other than they are to the symbiotic strains found in nematodes. This is the first report of the isolation of P. luminescens from infected humans in Australia and the second report of the isolation of this species from infected humans worldwide.

Control of attachment, morphology, and proliferation of skeletal myoblasts on silanized glass.

Generating skeletal muscle in vitro is an attractive approach to overcome problems associated with autologous transfer of muscle and donor site morbidity during plastic surgery. Such tissue engineering requires application of biomaterials that selectively control the attachment, morphology, and proliferation of muscle progenitor ("satellite") cells. This study examined the initial attachment, morphological characteristics, and proliferative behavior of murine C2C12 myoblasts on glass substrata derivatized with self-assembled monolayers (SAMs) of the organosiloxanes N-(2-aminoethyl)(3-aminopropyl)trimethoxysilane (EDA) and tridecafluoro-1,1,2,2-tetrahydrooctyl-1-dimethylchlorosil ane (13F). The fraction of myoblasts resisting detachment upon rinsing was greater on EDA than on 13F. Application of a quantitative moments-based analysis of cell morphology demonstrated that projected area and two size-invariant metrics of shape (extension and dispersion) for these cells were greater for EDA than for 13F. Myoblasts also proliferated faster on EDA than on 13F. These data indicate that EDA-derivatized glass provides a superior substratum for myoblast culture compared to 13F-derivatized glass. Understanding myoblast behavior on these biomaterials that promotes contrasting cellular responses is the first step toward using patterned SAMs to control myotube alignment for tissue engineering skeletal muscle.

Effect of cell-cell interactions on the observable strength of adhesion of sheets of cells.

Previous research in cellular adhesion has focused primarily on studying isolated cells under conditions where cells do not interact with each other. However, in vivo cells form sheets where both cell-substratum and cell-cell interactions contribute to the overall adhesive behavior. Our understanding of how cell-cell and cell-substratum interactions affect the overall process of cell adhesion in these situations is limited. To address this problem, we developed a systematic approach to evaluate how cell-cell and cell-substratum interactions affect the critical shear stress for detachment for semi-confluent and confluent sheets of cells. Our studies were based on subjecting cultures of adherent cells to a defined hydrodynamic flow in a radial-flow chamber with a gap height of 140 microm. Using phase-contrast microscope imaging and analysis we measured shear-dependent patterns of detachment as a function of the extent of cell confluency. Our results show that the critical shear stress for detachment is maximum at intermediate extents of confluency of 10%-40%. These results have important implications for sodding vascular grafts and tissue engineering.

Isolation of Clostridium tetani from anaerobic empyema.

We report the isolation of Clostridium tetani (along with Fusobacterium mortiferum) from empyema pus. The patient, a 68 year old retired farmer from rural NSW, had recently undergone cholecystectomy, had heart failure and developed an empyema. He improved after drainage of the empyema and penicillin therapy, but died suddenly during convalescence.

Actinobacillus equuli septicemia: an unusual zoonotic infection.

We describe the isolation of Actinobacillus equuli from the blood of a 53-year-old butcher with septicemia. This species of the genus Actinobacillus is primarily associated with animals and animal diseases, especially septicemia in foals. This is the first report of the isolation of A. equuli from a human with septicemia.

Isolation of Lautropia mirabilis from sputa of a cystic fibrosis patient.

An aggregate-forming coccus, isolated twice as the predominant microorganism in sputa from a cystic fibrosis patient on consecutive days, was shown to belong to the species Lautropia mirabilis on the bases of similarities of 16S rRNA gene sequences and phenotype. These isolates of L. mirabilis appear to be the first reported from a patient with cystic fibrosis and outside of Denmark.

Human lymphadenitis due to Corynebacterium pseudotuberculosis: report of ten cases from Australia and review.

Corynebacterium pseudotuberculosis commonly causes caseous lymphadenitis in Australian sheep. We describe 10 cases of human lymphadenitis due to C. pseudotuberculosis; in all cases, isolates were submitted to a reference laboratory in Victoria, Australia. Most of the patients were occupationally exposed to sheep. We also review the 12 previously published cases of this infection, most of which were reported from Australia. No patient had any underlying disease or predisposing condition. Surgical excision of the affected lymph glands is the mainstay of management, and antibiotic therapy is supplementary treatment. Diagnosis was delayed for some patients, and some patients had a protracted or recurrent clinical course and/or a slow recovery. These 10 additional cases from one Australian state indicate that human lymphadenitis caused by C. pseudotuberculosis has not been as rare as the number of published reports indicates, at least in Australia. However, the increasing use of a vaccine against caseous lymphadenitis in sheep in Australia should result in the decreasing human incidence of this zoonosis.

Helcococcus kunzii as sole isolate from an infected sebaceous cyst.

Helcococcus kunzii was isolated in pure culture from pus drained from an infected sebaceous cyst associated with marked cellulitis. The cyst was excised one month later after the inflammation had subsided with flucloxacillin treatment. This is the first report of the isolation of H. kunzii as the sole pathogen from an infected site.

Dog-associated bacterial infections in humans: isolates submitted to an Australian reference laboratory, 1981-1992.

Over the period 1981-92, 32 bacterial isolates were referred to the Microbiological Diagnostic Unit from infected dog-bite wounds and 10 isolates were submitted from blood cultures after dog bites or close contact with dogs. The isolates from the bite wounds were identified, or confirmed, as Pasteurella multocida (11 isolates), Pasteurella dagmatis (3), CDC group M-5 (9), CDC group EF-4a (8) and Streptococcus anginosus (1). Five of the 9 patients from whom CDC group M-5 was cultured had mixed infections: 2 with P. multocida one of which also had Bacteroides sp., one with P. dagmatis, one with CDC group EF-4a and another with Bacteroides sp. Nine of the 10 blood isolates were identified as Capnocytophaga canimorsus. The remaining one of Streptobacillus moniliformis, which is typically associated with rat-bite fever, was the result of a bite from a breed of dog (greyhound) that eats rodents. Clinical notes are provided for infections caused by the more unusual bacterial isolates and their laboratory identification is described.

Actinobacillus spp. and related bacteria in infected wounds of humans bitten by horses and sheep.

We describe the isolation of Actinobacillus lignieresii and an A. equuli-like bacterium from an infected horse-bite wound in a 22-year-old stable foreman and A. suis from a bite injury in a 35-year-old man who had been attacked by a horse. A. lignieresii was also isolated in pure culture from an infected sheep-bite wound in a rural worker. These species of the genus Actinobacillus are primarily associated with animals and animal diseases and are rarely isolated from humans. The purpose of this report is to raise awareness of the possible occurrence of Actinobacillus spp. in bite wounds inflicted by farm animals and to discuss the difficulties encountered in the identification of species of Actinobacillus and related bacteria.

Peritonitis caused by Pseudomonas mesophilica in a patient undergoing continuous ambulatory peritoneal dialysis.

We describe a case of recurrent peritonitis caused by Pseudomonas mesophilica in a diabetic man receiving continuous ambulatory peritoneal dialysis. Stagnant water on a bath rail used for support by the patient while showering was implicated as the probable source of these infections. We believe this to be the first report of the isolation of this water-associated bacterium in such infections.

Lung infection caused by Rhodococcus.

We report a case of lung infection, clinically resembling tuberculosis, caused by Rhodococcus rubropertinctus. The patient had no apparent immunosuppression which is unusual for disease caused by the 'rhodochrous' complex. The infection responded successfully to oral anti-tuberculous therapy, which included rifampicin, and to oral tetracycline.

Alcaligenes piechaudii from chronic ear discharge.

A recently described bacterium, Alcaligenes piechaudii, was isolated repeatedly from the ear discharge of a diabetic man. This appears to be the first report of human infection in which there is clinical evidence of a pathogenic role for this species.

Legionella pneumophila and water temperatures in Australian hospitals.

Thirty-four samples of warm waters from 12 psychiatric centres in Victoria and New South Wales were examined for legionellae by guinea-pig inoculation. Legionella pneumophila was isolated from 20 of the samples collected from ten of the establishments investigated. The detected prevalence proportion of L. pneumophila in waters of temperatures 36 to 43 degrees C was 0.9 (18/20), whereas the prevalence in waters of temperatures 45 to 54.2 degrees C was 0.14 (2/14). The two 'positive' waters within the latter range showed evidence of low numbers of L. pneumophila. No significant antibody titres to relevant serogroups were detected in the 112 exposed residents tested from seven psychiatric hospitals in New South Wales. The findings show that the temperature range with the greatest prevalence of L. pneumophila in warm waters is 36 to 43 degrees C. The presence of legionellae in these warm water-distribution systems contrasts with their absence from the water-distribution systems of Victorian hospitals in an earlier survey and underlines the value and simplicity of the usual Australian practice of maintaining hospital hot water temperatures at about 70 degrees C in the control of L. pneumophila.

Endocarditis caused by Rothia dentocariosa.

A case of infective endocarditis caused by Rothia dentocariosa is described in a 53 year old man with a history of rheumatic fever. R dentocariosa is a component of the oral microbiota and has only rarely and recently been recognised as a human pathogen. In this patient the oral flora was the probable source of infection, with a broken molar tooth providing the probable avenue for infection.