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.

Biochemical and exoenzymatic properties of Aeromonas species.

One hundred twenty-seven isolates of Aeromonas comprising the three currently recognizable species (A. hydrophila, A. sobria, and A. caviae) were evaluated for biochemical and exoenzymatic properties. Aeromonas species were generally (greater than 90%) characterized as gram-negative fermentative rods that were oxidase-, catalase-, and beta-galactosidase-positive, produced arginine dihydrolase, and failed to decarboxylate ornithine. More than 95% of all isolates tested failed to grow on 6.5% salt or thiosulfate-citrate bile salts agar and were resistant to the vibriostatic agent 0/129. Most Aeromonas species produced acid from hexoses while failing to ferment alcoholic sugars or trisaccharides. In exoenzymatic studies, Aeromonas species were uniformly found to produce several exoenzymes, including amylase, DNase, RNase, esterase, lipase, gelatinase, protease, fibrinolysin, and chitinase. Within the genus, a number of biochemical and enzymatic properties were found to be associated with one or more of the taxonomically recognizable species. These properties included glycoside utilization, Heiberg grouping based upon fermentation of arabinose, sucrose, and mannose, and the elaboration of several extracellular enzymes (elastase, hemolysin, lecithinase, phosphatase). In addition, phenotypic markers previously associated with enterotoxigenic Aeromonas isolates were almost exclusively found among A. hydrophila and A. sobria species, suggesting that these species are the major enteric pathogens.

Morphologic aberration associated with colonial tenacity of Pseudomonas aeruginosa.

A blood isolate of Pseudomonas aeruginosa was encountered which produced, on subculture to Mueller-Hinton agar, markedly adherent, tenacious colonies which were characterized microscopically by the presence of serpentine rows of interlocking bacilli. Factors accounting for the observed morphologic aberration, which was lost upon subculture, remain unknown.

Enhanced recovery of Pseudomonas aeruginosa from diverse clinical specimens on a new selective agar.

A new agent, 9-chloro-9-(diethylaminophenyl)-10-phenylacridan (C-390), was compared to currently available selective agars for the recovery of Pseudomonas aeruginosa. Media containing C-390 were highly selective for P. aeruginosa and enhanced recovery of the organism from clinical specimens because of the low background level of contaminating microorganisms.

Evaluation of five rapid systems for the identification of Neisseria gonorrhoeae.

Five commercial kit systems for the rapid identification of Neisseria gonorrhoeae were evaluated. The systems were tested with various pathogenic and saprophytic Neisseria and Branhamella strains having reactions typical for their individual species. Three systems (RIM-N, quadFERM, and RapID NH) were found to be 100% sensitive and specific.

Aeromonas species in clinical microbiology: significance, epidemiology, and speciation.

Over a one-year period, 32 strains (31 clinical, 1 environmental) of Aeromonas sp. were recovered. Chief sources of isolation were the gastrointestinal tract (48%), wounds (19%), and blood (13%). Gastrointestinal isolates were most often recovered from young (less than 5 yrs) children with diarrhea; wound or blood isolates were recovered more often from an older (avg. 56 yrs) population with one of several underlying disorders. Regardless of body site of isolation, most strains of Aeromonas appeared to be community acquired and not nosocomially transmitted. Over 70% of all isolates recovered during this year period were isolated during summer or fall months, suggesting a seasonal distribution of this microorganism. Speciation of Aeromonas isolates revealed A. hydrophila to be the predominant species isolated from clinical specimens, although significant percentages of other Aeromonas sp. were also recovered from clinical material.

Preliminary studies on the use of carbon substrate utilization patterns for identification of Brucella species.

A commercial system (Biolog, Hayward, CA) that uses reduction of an indicator dye to determine the oxidation of 95 different carbon substrates contained in a defined minimal medium was tested with 35 isolates of Brucella spp. to determine if the system could be used in place of respirometric methods to identify species. Of 95 substrates contained in this system, three were oxidized by all the Brucella strains tested, 48 were oxidized by none of the strains tested, and 44 were oxidized differentially. Brucella melitensis, B. abortus, and B. suis could be distinguished from each other on the basis of their oxidation reactions in seven in these substrates; epidemiologically related strains could not be unambiguously differentiated. This carbon substrate utilization method may prove to be a useful alternative to respirometry as a means to identify strains of Brucella spp. to species level, provided that personnel are protected from exposure to this highly infectious agent.

In vitro susceptibilities of Edwardsiella tarda to 22 antibiotics and antibiotic-beta-lactamase-inhibitor agents.

The in vitro susceptibilities of 22 isolates of Edwardsiella tarda were studied with 22 antibiotics and antibiotic-beta-lactamase-inhibitor agents. Results indicated that all isolates were susceptible to the aminoglycosides, cephalosporins, penicillins, imipenem, aztreonam, ciprofloxacin, and antibiotic-beta-lactamase-inhibitor agents. Each strain produced a beta-lactamase even though no resistance was detected to the beta-lactams.

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.

Diagnosis of herpesvirus infections: correlation of Tzanck preparations with viral isolation.

Evaluation of Giemsa-stained smears of scrapings from the base of vesicles or ulcers ( Tzanck preparation) for the presence of multinucleated giant cells and/or intracellular inclusions were diagnostic for herpesvirus in 18 of 21 cases (86%) of culturally proved herpesvirus infections. Smears from four patients with varicella-zoster infection also revealed cytologic alterations characteristic of herpesvirus.

Vibrio alginolyticus bacteremia in an immunocompromised patient.

Vibrio alginolyticus, an extremely halophilic member of this genus, was isolated from multiple sets of blood cultures drawn during a septic crisis of a patient with osteogenic sarcoma. No identifiable source of this infection could be determined.

The pathogenicity of Aeromonas strains relative to genospecies and phenospecies identification.

The relative pathogenicity of 80 Aeromonas strains typed by biochemical (phenospecies) and genetic (genospecies) methods was assessed by determining the 50% lethal dose for each isolate in Swiss-Webster mice by intraperitoneal injection. Overall, the maximum difference in virulence potential observed between the least and most pathogenic strains was a four log (10,000-fold) difference. Results according to phenospecies designation supported previous investigations indicating that both A. hydrophila and A. sobria are inherently more pathogenic for mice than A. caviae. According to genospecies designation, the relative virulence of individual groups in decreasing order was as follows: HG 9 (A. jandaei) greater than HG 1 (A. hydrophila) and HG 12 (A. schubertii) greater than HG 10 (A. veronii biotype veronii) greater than HG 8 (A. veronii biotype sobria) greater than HG 11 (unnamed) greater than HG 2 (unnamed) greater than HG 3 (A. salmonicida), HG 4 (A. caviae) and HG 6 (A. eucrenophila) greater than HG 5 (A. media) greater than HG 7 (A. sobria).

Iron utilization studies in Citrobacter species.

Seventy-one strains of Citrobacter were screened for iron scavenging mechanisms by biologic and chemical assays. Essentially all citrobacteria (70/71) were found to elaborate enterobactin-like siderophores by both biologic and chemical assays, however only c. koseri (C. diversus) was found to produce aerobactin. The concentration of ethylenediamine di(o-hydroxyphenylacetic acid) (EDDA) required to inhibit the growth of individual Citrobacter strains by depleting free iron ranged from 250 micrograms/ml to 100 micrograms/ml. Iron utilization studies of selected citrobacter isolates indicated that hemin and hematin could reverse the effects of iron limitation on growth under iron-stressed conditions (1000 micrograms/ml of EDDA). Two C. koseri strains grown under iron-restricted conditions showed similar changes in their whole cell protein profiles including induction of high molecular mass proteins (72-83 kDa) which may play a role in iron acquisition under iron-stressed conditions. The collective results support an additional virulence-associated mechanism for C. koseri strains which may help explain the greater pathogenic potential this group has for causing serious extraintestinal disease in humans.

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.

Detection, quantitation and stability of the beta haemolysin of Aeromonas spp.

Amongst 58 isolates of motile aeromonads evaluated for the ability to produce beta haemolysin, haemolytic activity was significantly associated with strains belonging to the Aeromonas hydrophila and A. sobria groups. Of erythrocytes from nine animal species tested, mouse red blood cells provided the best indicator system for detection of beta-haemolysin activity. Furthermore, differences in the stability of the beta haemolysins of selected A. sobria and A. hydrophila isolates at different temperatures, and in the presence of urea or dithiothreitol were observed.

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.

Association of Neisseria cinerea with ocular infections in paediatric patients.

Twenty-two strains of Neisseria cinerea were recovered from paediatric patients over a 7-year period and forwarded to the Microbial Diseases Laboratory for biochemical identification and/or confirmation. Eighteen of these 22 strains (82%) were recovered from the eyes of very young children (< or = 1 year), > 50% occurring during the neonatal period. The majority of eye isolates were involved in a variety of ocular infections including orbital cellulitis, conjunctivitis, and eye discharge (most common); in four of the 13 instances (31%) where laboratory data was available, Neisseria cinerea was recovered in pure culture. Neisseria cinerea isolates were often submitted to the Microbial Diseases Laboratory as possible 'N. gonorrhoeae' or 'Neisseria species' due to problems resulting from the use of commercial assays or unfamiliarity with the organism. These observations indicate that N. cinerea can produce eye infections in very young children, who presumably acquire this organism vertically from the mother during birth. Accurate identification of N. cinerea in such infants can preclude the social trauma and possible legal ramifications which can initially result from its misidentification as N. gonorrhoeae.

Rat-bite fever (Streptobacillus moniliformis): a potential emerging disease.

OBJECTIVES: To determine the relative prevalence of human infections attributable to Streptobacillus moniliformis in California over the past 3 decades. METHODS: A retrospective analysis of all the data collected was conducted on S. moniliformis cultures identified by the Microbial Diseases Laboratory (MDL) from January 1970 to December 1998. RESULTS: Information on a total of 45 S. moniliformis isolates was analyzed. Overall, 91% of the isolates were from human sources; 58% were received since 1990. These strains were divided almost equally between males and females, with 50% of the isolates from patients 9 years old or younger. In 75% of the cases of human infections where a diagnosis was given, rat-bite fever (RBF) was suspected; 83% of these suspected cases involved either a known rat bite or exposure to rodents. CONCLUSIONS: As crowding becomes an increasing environmental reality, humans are more frequently being exposed to zoonotic diseases as a result of encounters with "wild" animals. Domesticated animals also are exposed more frequently to wild animals; thus, increasing human exposure to once rare zoonotic illnesses. Rat-bite fever is a disease that seems to be easily recognizable by clinicians, easily identified in the clinical laboratory (if suspected), and successfully treated when the appropriate therapy is administered. Physicians should consider RBF as a possible diagnosis when fever, rash, and exposure to rats are part of the patient's history.

Occurrence, characterisation and detection of potential virulence determinants of emerging aquatic bacterial pathogens from the Philippines and Thailand.

Strains of Aeromonas spp., 'non-cholera vibrios' (NCVs) and Plesiomonas shigelloides isolated from aquatic environments, fish and human diarrhoeal cases in the Philippines and Thailand were characterised for potential virulence markers. Thus, the production of cytotoxin, cell-associated and cell-free haemolysin and their capacity to adhere to human intestinal (Henle 407) cells in vitro was investigated. In addition, the occurrence of tlh and tdh haemolysin genes and urease activity among V. parahaemolyticus strains was investigated. The results showed that strains recovered from clinical sources (human and fish) produced these virulence factors, whereas these are absent in environmental strains.