Enterobacter cancerogenus ("Enterobacter taylorae") infections associated with severe trauma or crush injuries.

Five cases of Enterobacter cancerogenus infections (wound, n = 4; bacteremia, n = 1) in adults are described. All infections seemed to be community acquired and occurred after precipitating events such as multiple trauma to the head or severe crush injuries. All five strains of E cancerogenus were recovered in pure culture, and three of these were isolated on multiple occasions. The results indicate that E cancerogenus can cause wound infections and septicemia in persons environmentally exposed to these organisms during traumatic events.

A new diagnostic problem: isolation of Escherichia coli O157:H7 strains with aberrant biochemical properties.

Over a five-year period (1995-1999) the Microbial Diseases Laboratory received 34 strains of E. coli O157:H7 each with a single aberrant biochemical property. In addition, 27 O157 strains with negative or delayed motility were noted during the same time period. These observations suggest that there may be an increased likelihood to misdiagnose O157:H7 infections using commercial systems in the future due to increasing phenotypic variability.

Expression of an iron-regulated hemolysin by Edwardsiella tarda.

The ability of Edwardsiella tarda to hemolyse red blood cells was investigated. Most E. tarda strains (> 80%) produced a hemolysin when assayed by either an agar overlay or contact-dependent hemolysis technique. This activity was cell-associated (CAH) and not released into the culture supernatant under routine conditions. When quantified, E. tarda strains significantly produced 30-40-fold higher levels of hemolytic activity against guinea pig, sheep, or rabbit erythrocytes than either E. hoshinae or E. ictaluri. When grown under iron restricted-conditions in the presence of ethylenediamine di(o-hydroxyphenylacetic acid), hemoglobin, hematin and hemin were found to stimulate growth in both liquid and agar bioassays. Hemolysin activity could be released from selected E. tarda strains when grown in L broth supplemented with EDDA; hemolytic activity was 3- to > 40-fold under these conditions when compared to L broth alone. Preliminary characterization of the hemolysin of strain ET-13 indicates that it is a heat-labile protein with active sulphydryl and thiol groups. These results indicate that, in addition to its invasive capabilities, E. tarda produces a hemolysin which is at least partially regulated by the relative availability of iron and may play a role in human disease.

Unusual food-borne pathogens. Listeria monocytogenes, Aeromonas, Plesiomonas, and Edwardsiella species.

Although these four groups of organisms are perceived as infrequent food-borne pathogens or of dubious significance, increasing epidemiologic data indicate that L. monocytogenes is an emerging cause of infections, particularly gastroenteritis. Furthermore, if data are ever generated that prove that most fecal isolates of Aeromonas are involved in bacterial diarrhea, then aeromonads will become recognized as important food-borne pathogens. For Plesiomonas and Edwardsiella, recognition of possible involvement in food-borne disease requires detailed medical histories, including foreign travel, contact with pets or animals, and food consumption histories.

High incidence of extra-intestinal infections in a Salmonella Havana outbreak associated with alfalfa sprouts.

OBJECTIVE: To determine a vehicle and point source for an outbreak of Salmonella Havana. METHODS: The authors conducted a case-control study and traceback investigation of 14 residents of California and four from Arizona with onsets of illness from Apr 15, 1998, to June 15, 1998, and Salmonella Havana infections with identical PFGE patterns. RESULTS: Seventeen of 18 patients were women. Seventeen were adults 20-89 years of age. Nine (50%) had diarrheal illness, 6 (33%) had urinary tract infections, 2 (11%) had sepsis, and one had an infected surgical wound after appendectomy. Four patients were hospitalized, and one died. Eating alfalfa sprouts was associated with S. Havana infection (OR = 10.0; 95% confidence interval 1.2, 83.1; P = 0.01). CONCLUSIONS: This outbreak resulted in a high incidence of extra-intestinal infections, especially urinary tract infections, and high morbidity. Raw alfalfa sprouts, often considered a safe "heath food," can be a source of serious foodborne disease outbreaks.

Isolation of toxigenic Hafnia alvei from a probable case of hemolytic uremic syndrome.

An 11-year-old girl presented to a central California children's hospital with a 3-day history of erythematous lesions on her forehead, neck, and trunk, abdominal pain, persistent emesis, and decreased urinary output. One day prior to admission she had a mild bout of diarrhea with a small amount of blood in her stool. Upon admission her condition rapidly worsened with acute renal failure, anemia, and thrombocytopenia. One of the possible causes of this condition included hemolytic uremic syndrome. Stool cultures of this patient tested at the children's hospital and at a state reference laboratory were repeatedly negative for Escherichia coli O157:H7. However, the state reference laboratory detected a toxigenic strain of Hafnia alvei active on Vero cells from two consecutive stool cultures during the acute phase of her illness.

Severe gastroenteritis associated with Vibrio hollisae infection: report of two cases and review.

Vibrio hollisae, one of the more recently described halophilic Vibrio species, is infrequently associated with gastrointestinal disease and only rarely recovered from individuals presenting with gram-negative sepsis. In this report we describe two cases of severe gastrointestinal disease associated with V. hollisae in otherwise healthy individuals. In one of these individuals, severe epigastric pain was apparently associated with signs of pseudoappendicitis, necessitating exploratory surgery. In both individuals, infection was associated with the ingestion of raw shellfish. These cases are discussed in light of previous reports on the epidemiology, pathogenesis, and spectrum of disease caused by this unusual pathogen.

Isolation of Yokenella regensburgei ("Koserella trabulsii") from a patient with transient bacteremia and from a patient with a septic knee.

Yokenella regensburgei ("Koserella trabulsii") was isolated from a 74-year-old male with a septic knee and from a 35-year-old immunocompromised female whose transient bacteremia occurred without overt signs of sepsis. Neither strain was correctly identified by laboratories using a variety of techniques.

Evolving concepts regarding the genus Aeromonas: an expanding Panorama of species, disease presentations, and unanswered questions.

It has been almost 10 years since a major review on the association of Aeromonas with human disease has been published. During that period the number of valid species in the genus has grown to 14, with a new family (Aeromonadaceae) established to house this genus. Despite this explosion in the number of new genomospecies, only five (Aeromonas hydrophila, A. caviae, A. veronii, A. jandaei, and A. schubertii) are currently recognized as human pathogens. New syndromes attributed to this genus include hemolytic uremic syndrome, burn-associated sepsis, and a variety of respiratory tract infections, including epiglottitis. Convincing evidence suggests that some aeromonads do cause gastroenteritis, but it is presently unclear whether many of the strains isolated from feces are involved in diarrheal disease. Many questions regarding this genus remain unanswered.

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.

Infections associated with the genus Edwardsiella: the role of Edwardsiella tarda in human disease.

The role of the genus Edwardsiella in human illness is reviewed. Of the three recognized species, only Edwardsiella tarda has been demonstrated to be pathogenic for humans. Chief infections associated with this species include bacterial gastroenteritis, wound infections such as cellulitis or gas gangrene associated with trauma to mucosal surfaces, and systemic disease such as septicemia, meningitis, cholecystitis, and osteomyelitis. Risk factors that are associated with E. tarda infections include exposure to aquatic environments or exotic animals (e.g., reptiles or amphibia), preexisting liver disease, conditions leading to iron overload, and dietary habits (e.g., raw fish ingestion). Although studies indicate that this bacterium is susceptible to most commonly prescribed antibiotics, fatal gastrointestinal and extraintestinal infections have been described.

Sucrose-positive Edwardsiella tarda mimicking a biogroup 1 strain isolated from a patient with cholelithiasis.

An unusual strain of Edwardsiella tarda mimicking a biogroup 1 isolate was recovered in a mixed infection from a woman suffering from cholelithiasis. Rare biochemical characteristics (e.g., H2S negativity) originally detected were related to an unusual biochemical property in this species, sucrose fermentation; other points of interest regarding this strain included the site of isolation (bile) and the failure of this isolate to produce many of the in vitro virulence markers associated with E. tarda.

Case of Aeromonas veronii (DNA group 10) bacteremia.

We describe the first case report of bacteremia due to Aeromonas veronii biotype veronii. The infection occurred in a 77-year-old man suffering from multiple underlying conditions which included cancer of the sigmoid colon. Because of the unusual biochemical phenotype of this group (ornithine decarboxylase positive), it was originally identified as Vibrio cholerae.

Overview of the etiology of wound infections with particular emphasis on community-acquired illnesses.

Wound cultures represent a general catchall category for a group of extremely diverse anatomic samples that range from superficial specimens of cutaneous structures (folliculitis, cellulitis) to specimens revealing invasive infections involving deep fascial planes and muscle (myonecrosis). Because of the complex nature of these infective processes, the terminology associated with such infections is often imprecise and confusing. Wounds are the result of trauma, either intentionally or accidentally induced. Nosocomial wound infections result primarily from surgical procedures, the development of pressure sores, or catheterization. Community-acquired wound infections are often preceded by injuries resulting from occupational exposure or recreational activities and are associated with a greater diversity of microorganisms due to the exposure of open wounds to inhabitants of the microbial biosphere. This review provides a general overview of the categories of wound infections and describes their acquisition and clinical significance. Particular emphasis is placed on selected community-acquired wound infections and the etiologic agents associated with such conditions.

Penetration and replication of Edwardsiella spp. in HEp-2 cells.

The ability of 22 Edwardsiella strains to penetrate and replicate in cultured epithelial cells was initially evaluated by light microscopy methods and by the recovery of gentamicin-resistant (Gmr) bacteria from the Triton X-100 cell lysates of HEp-2-infected monolayers. Giemsa-stained HEp-2 cells revealed the presence of numerous internalized bacteria 3 h postinfection, often appearing as parallel rows of replicated bacteria within the cytosol and sometimes obliterating the cytoplasm because of the large numbers of bacilli present. Invasive bacteria were also sometimes found within cytoplasmic vacuoles in infected cells; thin-section electron micrographs of HEp-2-infected cells supported these conclusions. Results of light microscopy studies and cell lysate assays indicated that most Edwardsiella tarda (92%) and some Edwardsiella hoshinae strains were invasion positive on one or more occasions, while Edwardsiella ictaluri isolates were uniformly negative. HEp-2 invasion by E. tarda was a microfilament-dependent (cytochalasin B- and D-sensitive) process, with maximum numbers of Gmr CFU recorded between 3 and 6 h postinfection. The small percentage (0.01 to 1.0%) of the challenge inoculum recoverable as Gmr progeny 3 to 6 h postinfection was attributed to a strong cell-associated (not filterable) hemolysin that was produced by a majority (85%) of the E. tarda strains but not by E. ictaluri and only minimally by E. hoshinae. This cytolysin/hemolysin was responsible for the toxic effects observed in HEp-2 cells during the infection-replication process of edwardsiellae and appears to play a role in the release of internalized and replicated bacteria from infected cells. The results suggest an invasion strategy with some similarities to and differences from those of other recognized enteroinvasive pathogens.

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.

Identification and initial characterization of elastase activity associated with Vibrio cholerae.

Strains of Vibrio cholerae O1 (Ogawa, Inaba) and non-O1 serogroups have been found to produce an elastolytic protease that can be detected on 0.3% elastin agar plates or in broth cultures. The elastase enzyme appears to be maximally expressed in late log phase (14-18 h postinoculation) and has optimum activity at a pH range between 7 and 8. Comparative studies indicate that more than 60% of V. cholerae strains analyzed quantitatively produce more elastase in broth (two- to fourfold higher) than other elastase-positive Vibrio species such as Vibrio vulnificus. The V. cholerae elastase enzyme was not inhibited by trypsin, serine-protease, or thiol-protease inhibitors, but was inhibited by phosphoramidon. Ultrafiltration studies indicate the V. cholerae elastase enzyme has a molecular weight >30,000, and a 34K protein with possible elastase activity has been detected by SDS-PAGE for one non-O1 isolate (strain 2396). Cumulative results suggest that the V. cholerae elastase is probably a member of the N-type metalloprotease family and shares similar properties with other elastase enzymes described for pathogenic and nonpathogenic species in this genus.

Prototypal diarrheagenic strains of Hafnia alvei are actually members of the genus Escherichia.

We analyzed five bacterial strains, designated 19982, 9194, 10457, 10790, and 12502, that were isolated from stool specimens of individuals with diarrheal illness by the International Centre for Diarrhoeal Disease Research in Dhaka, Bangladesh (M. J. Albert, S. M. Faruque, M. Ansaruzzaman, M. M. Islam, K. Haider, K. Alam, I. Kabir, and R. Robins-Browne, J. Med. Microbiol. 37:310-314, 1992). The strains were initially identified as Hafnia alvei with a commercial identification system and were reported to contain the eae gene of enteropathogenic Escherichia coli. Results of conventional biochemical analyses, testing of susceptibility to cephalothin, lysis by a Hafnia-specific phage, and amplification of the outer membrane protein gene phoE with species-specific primers support the identification of these strains as members of the genus Escherichia rather than Hafnia alvei. These strains varied from typical E. coli strains by their inability to produce acid from lactose or D-sorbitol and failure to elaborate the enzyme beta-D-glucuronidase. PCR analysis confirmed previous findings that the strains were positive for the eae gene and negative for other virulence markers present among recognized categories of diarrheagenic E. coli. Our findings support the hypothesis that these strains are a new category of diarrheagenic isolates belonging to the genus Escherichia and illustrate the importance of using multiple methodologies when identifying new bacterial agents of diarrheal disease.

Antimicrobial resistance and R factors in Salmonella isolated in California (1971-1972).

The antimicrobial resistance of 2,246 strains of Salmonella isolated from humans in California was determined. Resistance to one or more of the 12 antimicrobial agents tested was found in 32% of the isolates. Salmonella typhimurium strains represented 31% of the serotypes isolated; 49% of these strains were resistant. Fifty-one percent of S. heidelberg, 42.5% of S. newport, and 40% of S. saint paul strains were resistant. Seventy-seven percent of all resistant serotypes were resistant to two or more of the antimicrobial agents tested. R factors were demonstrated in 70% of the multiply resistant strains. Resistance of the Salmonella strains to one or more of the 12 antimicrobials tested and the frequency of resistance to tetracycline and ampicillin were significantly greater than resistance reported in other studies performed in this country. Chloramphenicol resistance was encountered in 33 (1.5%) of the Salmonella isolates; 19 of these were S. typhi demonstrating a pattern of resistance to streptomycin, sulfisoxazole, tetracycline, and chloramphenicol and carrying an R factor capable of transferring the complete pattern of resistance.