Pseudoappendicitis caused by Plesiomonas shigelloides.

A 20-year-old patient was hospitalized with clinical signs of acute appendicitis. After surgery, the histological findings in the appendix and a lymphatic node suggested the diagnosis of pseudoappendicitis caused by Plesiomonas shigelloides, which was isolated in pure culture from the lymphatic node. The strain of P. shigelloides was found to elaborate a heat-stable toxin and harbored two plasmids of 280 and 4 kilobases. A large plasmid has previously been implicated as a virulence marker in P. shigelloides infections.     

Plesiomonas shigelloides in South Australia

Plesiomonas shigelloides, a motile, oxidase-positive, Gram-negative rod that may possess shigella antigens, was isolated from the faeces of 36 children and two adults. In 13 children the organism was thought to be possibly the cause of enteritis and in eight children there was no evidence of intestinal disease. In nine children with gastroenteritis other enteropathogenic bacteria were found in addition, and six children had intestinal disease due, or possibly due, to other factors. Only four of the 38 strains had shigella antigens.     

Expression of hemolytic activity by Plesiomonas shigelloides.

More than 90% of the Plesiomonas shigelloides strains that we tested produced a beta-hemolysin, as judged by the results of agar overlay and contact-dependent hemolysis assays. The hemolysin was cell associated, was active against the erythrocytes of various animal species, and was synthesized at both 25 and 35 degrees C. Activity was lost after thermal or proteolytic treatments or after preincubation in the presence of gentamicin; hemolytic activity did not appear to correlate with the previously established 50% lethal doses for seven of these strains. The hemolysin may play a role in iron acquisition in vivo via the lysis of erythrocytes, liberating hemoglobin, or, alternatively, may be involved in gastrointestinal disease.     

Cellular fatty acid composition of Plesiomonas shigelloides.

The cellular fatty acid compositions of 29 strains of Plesiomonas shigelloides and 5 strains of Aeromonas hydrophila were studied. The cellular fatty acid compositions of all the Plesiomonas strains were identical and characterized by the presence of hexadecanoate (16:0) (33%), hexadecenoate (16:1) (28%), octadecenoate (18:1) (9%), and octadecanoate (18:0) (6%). The cellular fatty acid composition of A. hydrophila was similar to that of the Plesiomonas strains, except that the former contained an average of 25% 16:0, 29% 16:1, 12% 18:1, and 2% 18:0 acids compared with 33, 28, 9, and 6%, respectively, for the latter. The percentage ratios of 16:1 to 16:0 and 18:1 to 18:0 could be used to differentiate P. shigelloides from A. hydrophila. These ratios were 0.8 and 1.5 for the former and 1.2 and 6.0 for the latter.     

Diarrhea due to Plesiomonas shigelloides in cancer patients.

Plesiomonas shigelloides was isolated from the stools of two patients with gastrointestinal malignancies and from one "healthy" patient with diarrhea. No other enteric pathogens were isolated. One patient was neutropenic after antineoplastic chemotherapy. The two cancer patients had crampy abdominal pain and severe diarrhea and required antibiotic therapy for resolution of symptoms. The third patient responded to symptomatic treatment. Patients with gastrointestinal malignancies may be more susceptible to gastroenteritis caused by P. shigelloides than normal individuals, and these infections may be more severe than those seen in normal individuals.     

In vitro and in vivo pathogenicity of Plesiomonas shigelloides.

Epidemiologic evidence suggests that Plesiomonas shigelloides is an enteric pathogen. We conducted in vitro, animal, and volunteer studies on P. shigelloides isolates from patients with diarrhea. Five strains gave a negative keratoconjunctivitis reaction in guinea pigs and did not invade HeLa cells. Genetic probes for heat-stable enterotoxins related to those of enterotoxigenic Escherichia coli and for gene sequences common to the invasiveness plasmids of Shigella spp. and enteroinvasive E. coli were negative. Heat-labile enterotoxins were not found when a modified GM1-enzyme-linked immunosorbent assay was used. Rabbits did not develop diarrhea but were transiently colonized when inoculated with up to 10(11) P. shigelloides CFU using the reversible intestinal tie adult rabbit diarrhea model. A very large plasmid (between 118 and 312 megadaltons) was found in all isolates. Strain P012 was cured of its plasmid by novobiocin. This strain, but not its cured derivative, invaded the mucosa of the distal ileum of gnotobiotic piglets given 10(10) CFU. At a lower inoculum (10(9) CFU), strain P012 induced inflammation of the colonic mucosa and diarrhea at day 6. The same isolate was fed to 33 healthy volunteers in doses of 1 X 10(3) to 4 X 10(9) CFU. Thirty-six percent of the volunteers shed the organism, but none became ill. These data are only weakly supportive of a role for P. shigelloides in diarrheal illness and suggest the need for more studies with other strains to better understand its pathogenicity.     

Plesiomonas shigelloides overgrowth in the small intestine

An 83-year-old male presented with chronic diarrhea and protein malnutrition associated with Plesiomonas shigelloides overgrowth in the small intestine. This overgrowth was related to achlorhydria and small-bowel diverticula. Tests for heat-labile and heat-stable enterotoxin were negative on the P. shigelloides isolated from both the small bowel aspirate (3 x 10(8) bacteria per ml) and the patient's stool. The patient responded satisfactorily to tetracycline, to which this unusual isolate was susceptible in vitro. The ability to correctly identify and determine the antimicrobial susceptibility of P. shigelloides in the setting of small-bowel overgrowth will help determine appropriate therapy.     

Laboratory investigations on the low pathogenic potential of Plesiomonas shigelloides.

The pathogenic properties of 16 Plesiomonas shigelloides strains recovered from humans with extraintestinal and intestinal illnesses, infected animals, and environmental sources were investigated. Most strains possessed a high cell charge and low surface hydrophobicity analogous to those of Shigella spp.; additionally, serogroup O:17 strains reacted with Shigella group D antisera. However, unlike the shigellae, P. shigelloides strains did not universally bind Congo red, were noninvasive in HEp-2 cell assays, and did not produce a Shiga-like toxin on Vero cells. On HEp-2, Y1, and possibly Vero cells, a low-level cytolysin was consistently produced by all 16 P. shigelloides strains when grown in either Evan Casamino Acids-yeast extract or Penassay broth. The median 50% lethal dose for all 16 P. shigelloides strains in outbred Swiss Webster mice was 3.5 x 10(8) CFU (range, 3.2 x 10(7) to greater than 1 x 10(9) CFU). Animal pathogenicity did not correlate with cytolysin expression, possession of a greater than or equal to 120-MDa plasmid, protein profile, or resistance to complement-mediated lysis. No strain analyzed produced siderophores or a heat-stable enterotoxin. The results suggest that members of the genus Plesiomonas have an overall low pathogenic potential, irrespective of the site of isolation or phenotypic, serologic, or surface properties shared with other traditional enteropathogens.     

Plesiomonas shigelloides in acute cholecystitis: a case report.

Plesiomonas shigelloides was isolated as the sole pathogen from gallbladder bile and wall in a 58-year-old woman with acute cholecystitis. The patient developed an unusual postoperative complication characterized by culture-negative discharge from the wound in combination with extensive abdominal cellulitis and afebrility. Agglutinating antibodies to P. shigelloides were demonstrated in the serum of the patient by the microscopic Widal agglutination test.     

Laboratory observations on Plesiomonas shigelloides strains isolated from children with diarrhea in Peru.

Eleven strains of Plesiomonas shigelloides isolated from 10 Peruvian children with diarrhea were examined. All the strains were resistant to two or more antibiotics, most commonly ampicillin, gentamicin, erythromycin, kanamycin, and streptomycin. The strains were all negative in the Sereny and cell culture assays used to test for enteroinvasiveness. One strain showed cytotoxic activity on Vero cells. The strains showed no antigenic relationship with Shigella organisms. Both bioassays and enzyme-linked immunosorbent assays used for detection of Escherichia coli enterotoxins were negative. Nucleic acid probes for such toxins likewise gave negative results. The strains all possessed a large (approximately 200-megadalton) plasmid in addition to one or more other plasmids. Several different plasmid profiles were observed among these 11 P. shigelloides strains, indicating that the isolates were not acquired from a common source or from a single bacterial clone.     

Plesiomonas shigelloides bacteremia in a healthy girl with mild gastroenteritis.

A previously healthy 15-year-old girl fell ill with febrile gastroenteritis; Plesiomonas shigelloides was isolated from the blood 6 h after she had received one tablet of trimethoprim-sulfadiazine on the third day of symptoms. She recovered uneventfully. P. shigelloides may be isolated from the blood in immunocompetent patients with mild, uncomplicated gastroenteritis.     

Production of a heat stable enterotoxin by Plesiomonas shigelloides

Eight strains of Plesiomonas shigelloides were assayed for enterotoxin production in the rabbit ileal loop assay. Seven strains required serial in vivo passage in the rabbit's intestine before enterotoxin activity was detected in the cells' filtrate. Enterotoxin production was readily lost with subculture of these toxinogenic cells. Heat treatment of the cells' filtrate from three strains that had never been passed in vivo led to detectable enterotoxin activity in three of six separate assays. Using LT, CT, STIa, STIb and STII as probes, no homology to the whole cell DNA of the eight strains was detected on Southern hybridization under low stringency conditions. The enterotoxin of P. shigelloides appears to be novel since production is induced by in vivo passage, activity is seen with heat treatment of cells' filtrate and there is no DNA homology to the cloned enterotoxin genes of Escherichia coli and Vibrio cholerae.     

Isolation of a rare serovar of Plesiomonas shigelloides]

The authors describe the isolation of a rare serovar Plesiomonas shigelloides from a patient with diarrhoea. The isolated strain belongs according to a combined Japanese-Czechoslovak antigenic scheme to serovar 024 H"o". The interesting finding draws attention to the possibility of routine departments to contribute to investigations of the incidence, importance and antigenic structure of this bacterial species.     

Clinical features, epidemiology, and treatment of Plesiomonas shigelloides diarrhea.

Recent studies have suggested that Plesiomonas shigelloides is a cause of diarrhea. The present study addresses the clinical features, epidemiology, and response to antimicrobial therapy of P. shigelloides diarrhea. Thirty cases of P. shigelloides infection were defined by isolation of the organism from stool specimens, and 30 age-matched control patients were identified by detection of other enteric pathogens. Clinical and epidemiological information was obtained by interviewing the referring physicians and the patients. Of the P. shigelloides-infected patients, 71% had a history of recent tropical travel, but 29% acquired their infections locally in association with the consumption of seafood or untreated water or both. Seventy-eight percent of the P. shigelloides-infected patients had findings suggestive of colitis, and P. shigelloides-infected patients had a history of tropical travel, acute illness, abdominal pain, and prolonged symptoms significantly more often than did the control patients. Antimicrobial therapy significantly reduced the duration of illness in patients with Plesiomonas diarrhea. These results suggest that P. shigelloides is a significant cause of both locally acquired and traveler's diarrhea that may respond to antimicrobial therapy.     

Effect of acidity and antimicrobial agent-like compounds on viability of Plesiomonas shigelloides.

Nineteen Plesiomonas shigelloides strains were evaluated for their stability at acidic and slightly alkaline pHs and for their susceptibility to antimicrobial agent-like compounds produced by enteric flora. Most P. shigelloides isolates were rapidly inactivated under high-acid (pH 4 or less) conditions. Screening of enteric bacteria for elaboration of factors active against P. shigelloides revealed two organisms (Pseudomonas aeruginosa and Streptococcus [Enterococcus] faecium) capable of secreting such inhibitory substances. The results of this study suggest some factors potentially important in regulating gastrointestinal colonization by P. shigelloides from environmental sources.     

Proctitis and fatal septicemia caused by Plesiomonas shigelloides in a bisexual man.

A case of proctitis and fatal septicemia caused by Plesiomonas shigelloides in a 42-year-old bisexual male is reported. The medical history of the patient was significant for an aortic valve replacement 3 years before but was otherwise unremarkable. A serum specimen obtained at autopsy was negative for antibody to human immunodeficiency virus by Western blot (immunoblot) analysis. P. shigelloides isolated from blood was susceptible to all antibiotics tested, agglutinated in Shigella group D antiserum, possessed a greater than 100-megadalton plasmid, and was noninvasive in a HeLa cell invasion assay. The previous reports of Plesiomonas bacteremic infections are reviewed, and possible pathogenic mechanisms are discussed.     

Enrichment medium and control system for isolation of Campylobacter fetus subsp. jejuni from stools.

Enrichment culture with a semisolid medium increased by 6% the isolation rate of Campylobacter fetus subsp. jejuni. The semisolid enrichment medium was also used successfully as a transport medium for Campylobacter isolates. A blood agar plate streaked with Pseudomonas aeruginosa, Clostridium perfringens, and a laboratory strain of Campylobacter was a good control system for the microaerophilic atmosphere. Good growth of all three organisms indicated satisfactory conditions for culturing Campylobacter.     

Iron uptake in Plesiomonas shigelloides: cloning of the genes for the heme-iron uptake system.

The iron uptake systems of Plesiomonas shigelloides strains were determined. Siderophore production was not detected by chemical or biological assays, and the strains tested were unable to use enterobactin, aerobactin, or vibriobactin for growth in low-iron media. Both hemin and hemoglobin supported full growth of the bacteria in media lacking other iron sources, but neither transferrin nor lactoferrin served as a source of iron. Hemolysin was detected, and the production of hemolysin was iron repressible. DNA sequences encoding hemolysin production and DNA sequences encoding the ability to use heme or hemoglobin as a sole source of iron were cloned from P. shigelloides and expressed in Escherichia coli. The abilities to use heme and hemoglobin as iron sources were closely linked, and the cloned sequences encoded the ability to transport the porphyrin, as well as iron, into the cells.