Septicemia caused by dysgonic fermenter 3 in a severely immunocompromised patient and isolation of the same microorganism from a stool specimen

Dysgonic fermenter 3 (DF-3)-associated bacteremia occurred in a febrile patient with acute myelocytic leukemia during aplasia. Another DF-3 isolate, identical by ribotyping, was grown 10 weeks later from stool collected in the absence of diarrhea. This is the first case in which DF-3 was isolated from blood and stool specimens from the same patient.

Detection of Bartonella henselae DNA by two different PCR assays and determination of the genotypes of strains involved in histologically defined cat scratch disease

Cat scratch disease (CSD) is a common cause of subacute regional lymphadenopathy, not only in children but also in adults. Serological and molecular studies demonstrated that Bartonella henselae is the etiologic agent in most cases of CSD. Amplification of B. henselae DNA in affected tissue and detection of antibodies to B. henselae are the two mainstays in the laboratory diagnosis of CSD. We designed a retrospective study and investigated formalin-fixed, paraffin-embedded lymph nodes from 60 patients (25 female, 35 male) with histologically suspected CSD by PCR amplification. The sensitivities of two different PCR assays were compared. The first primer pair amplified a 296-bp fragment of the 16S rRNA gene in 36 of the 60 samples, corresponding to a sensitivity of 60%. The second primer pair amplified a 414-bp fragment of the htrA gene in 26 of the 60 lymph nodes, corresponding to a sensitivity of 43.3%. Bartonella DNA could be detected in a total of 39 (65%) of the 60 lymph nodes investigated. However, histopathologic findings are typical but not specific for CSD and cannot be considered as a "gold standard" for diagnosis of CSD. The sensitivity of the PCR assays increased from 65 to 87% if two criteria (histology and serology) were used in combination for diagnosis of CSD. Two genotypes (I and II) of B. henselae are described as being involved in CSD. Genotype I was found in 23 (59%) and genotype II was found in 9 (23%) of the 39 PCR-positive lymph nodes. Seven (18%) lymph nodes were negative in both type-specific PCR assays. Thirty (50%) of our 60 patients were younger than 20 years old (15 were younger than 10 years), 20 (33%) were between 21 and 40 years old, and 10 (17%) patients were between 41 and 84 years old. Our data suggest that detection of Bartonella DNA in patients' samples might confirm the histologically suspected diagnosis of CSD.

Relapsing Whipple's disease presenting with hypopituitarism

A 44-year-old man with a history of Whipple's disease 8 years ago presented with recurrent grand mal seizures and signs of hypopituitarism on physical examination. Magnetic resonance imaging of the brain revealed a hypothalamic lesion of 1 cm diameter in the region of the rostral infundibulum. Hypopituitarism was confirmed by low levels of serum cortisol, free testosterone and free thyroxine without an elevated TSH. Whipple encephalitis with hypothalamic involvement was suggested and verified by positive polymerase chain reaction (PCR) for Tropheryma whippelii in the cerebrospinal fluid. PCR for T. whippelii has become an important diagnostic tool for establishing the diagnosis of Whipple's disease especially in patients with unusual presentations and if the diagnosis cannot be confirmed histologically. Whipple's disease should be included in the differential diagnosis in hypopituitarism caused by infectious disease.

Influence of residual uracil-DNA glycosylase activity on the electrophoretic migration of dUTP-containing PCR products

In diagnostic amplification protocols contamination by previously amplified nucleic acids is considered the major source of false positive results. Substituting dUTP for dTTP in the PCR and initial treatment with uracil-DNA glycosylase (UNG) virtually eliminates these carryover contaminations. Subsequent procedures to visualize the amplicons or to optimize sensitivity and specificity of the test are not always fully compatible with UNG-treated PCR products. Here we describe the more pronounced influence of residual UNG activity on the migration of PCR amplification products in polyacrylamide as compared to agarose gels.

Emergence of related nontoxigenic Corynebacterium diphtheriae biotype mitis strains in Western Europe

We report on 17 isolates of Corynebacterium diphtheriae biotype mitis with related ribotypes from Switzerland, Germany, and France. Isolates came from skin and subcutaneous infections of injecting drug users, homeless persons, prisoners, and elderly orthopedic patients with joint prostheses or primary joint infections. Such isolates had only been observed in Switzerland.

Homogeneity of 16S-23S ribosomal intergenic spacer regions of Tropheryma whippelii in Swiss patients with Whipple's disease

The current genetic strategies used to identify Tropheryma whippelii, the putative agent of Whipple's disease, are based on PCR-mediated amplification of a part of its 16S rRNA gene (16S rDNA). Because there is very little intraspecies variation in these molecules, they are not suitable as targets for epidemiologic investigations. However, the intergenic spacer region between the 16S and 23S rDNAs is usually much more variable and has repeatedly been used for epidemiologic purposes. We have therefore amplified the spacer region of T. whippelii directly from clinical specimens from nine independent Swiss patients with Whipple's disease by PCR with primers complementary to the 3' and 5' ends of the 16S and 23S rDNAs, respectively. The amplicons were directly sequenced and the sequences were compared to the T. whippelii reference sequence in GenBank/EMBL (accession no. X99636). Complete sequence homogeneity was found between the samples from our nine patients; the spacer sequence was also identical to the reference sequence. However, the sequences corresponding to the 3' and 5' ends of the 16S and the 23S rDNAs of T. whippelii, respectively, differed from the respective sequences in GenBank/EMBL. The same sequence found in our patients was then found in a sample from the German patient from which the published sequence had been derived. We conclude that the 16S-23S rDNA spacer region seems to be very conserved in T. whippelii and that the respective reference entry in public databases should be revised.

An outbreak of nontoxigenic Corynebacterium diphtheriae infection: single bacterial clone causing invasive infection among Swiss drug users

From 1990 to 1996, a total of 65 patients from whom Corynebacterium diphtheriae had been isolated were reported to the Swiss Federal Office of Public Health. A retrospective review of medical and microbiological records as well as results of ribotyping of available isolates was performed. Twenty-seven patients had acquired their infection without evidence of use of illicit drugs, mostly as a skin infection imported from subtropical areas (20 patients); 38 isolations were associated with intravenous drug use (IVDU) (skin, 15; respiratory tract, 10; blood, 13). Endocarditis was documented in nine patients with bloodstream infection, four of whom died. There were two additional deaths due to overwhelming sepsis. The same ribotype of nontoxigenic C. diphtheriae was found in 31 of the 32 examined isolates associated with IVDU. All non-IVDU isolates had different ribotypes. Among Swiss drug users, a single clone of nontoxigenic C. diphtheriae was found over a period of several years with a high potential to cause severe invasive infection.

Lethal maternal sepsis caused by Campylobacter jejuni: pathogen preserved in placenta and identified by molecular methods

Campylobacter jejuni is one of the most common organisms in the etiology of febrile diarrhea. Bacteremia is reported to be rare. In pregnant women, however, C. jejuni (previous name, Vibrio fetus) can cause fetal death. We report the case of a pregnant woman with enterocolitis and sepsis that caused the death of the fetus and, 11 days later, the death of the mother. C. jejuni was detected by culture techniques at the time of the first symptoms but not during the subsequent course of disease. Bacteria were detected by silver staining and electron microscopic examination in the placenta, but for identification, we used molecular methods. From formalin-fixed, paraffin-embedded placental tissues, a part of the bacterial 16S rRNA was amplified by broad-range polymerase chain reaction, which resulted in a 461-nucleotide sequence. Direct sequencing and comparison to reference sequences revealed C. jejuni as the causative agent for the sepsis and deaths. With this approach, the adverse outcome could be related etiologically to the same infectious agent identified at the onset of the disease. From this and other recent reports, we conclude that C. jejuni must be considered an important pathogen in pregnancy.

Molecular diagnosis of bacterial endocarditis by broad-range PCR amplification and direct sequencing

Broad-range PCR amplification of part of the 16S rRNA gene followed by single-strand sequencing was applied to samples of 18 resected heart valves from patients with infective endocarditis. The PCR results were compared with those of cultures of valves and with those of previous blood cultures. For two patients there was agreement with the cultures of the valves; for nine patients there was agreement with the previous blood cultures, which were positive, while the cultures of the valves were negative; a Streptococcus sp. and Tropheryma whippelii each were found in one patient with negative cultures (valve and blood); for two patients the cultures of the valves as well as the PCR results were negative but the blood cultures were positive; for one patient amplification was inhibited; and for two patients the PCR results were positive but the amplicons could not be sequenced. It is concluded that broad-range PCR is a promising tool for patients with culture-negative endocarditis and allows the detection of rare, noncultivable organisms.

Inclusion of Aeromonas DNA hybridization group 11 in Aeromonas encheleia and extended descriptions of the species Aeromonas eucrenophila and A. encheleia

The recently reported chemotaxonomic and genotypic description of two well-separated subgroups (I and II) in Aeromonas eucrenophila and their affiliation to Aeromonas encheleia and the unnamed Aeromonas DNA hybridization group (HG) 11 (G. Huys, M. Altwegg, M.-L. Hänninen, M. Vancanneyt, L. Vauterin, R. Coopman, U. Torck, J. Lüthy-Hottenstein, P. Janssen, and K. Kersters, Syst. Appl. Microbiol. 19:616-623, 1996) has questioned the original species descriptions of A. eucrenophila and A. encheleia. In order to elucidate the unclear taxonomic status of these taxa in the genus Aeromonas, we have further investigated a collection of 14 reference strains and 14 related isolates encompassing the taxa A. eucrenophila subgroups I and II, A. encheleia, and HG11 by DNA-DNA hybridization (on 17 of the 28 strains) and phenotypic characterization (on all 28 strains). Genotypically, the investigated strains could be grouped into two DNA hybridization groups that exhibited between-group homologies ranging from 42 to 52%. The members of DNA homology group I (DNA binding, 76 to 100%) were strains of A. eucrenophila subgroup I, including the type strain LMG 3774, and two A. eucrenophila-like isolates, leading to the conclusion that these strains should be considered true representatives of the species A. eucrenophila. The strains of A. eucrenophila subgroup II, HG11, and A. encheleia, on the other hand, were closely joined in DNA homology group II (DNA binding, 74 to 105%) together with two presumptive A. encheleia isolates. The fact that strain LMG 16330T of A. encheleia was the only type strain residing in DNA homology group II implies that HG11 and A. eucrenophila subgroup II should be classified in the species A. encheleia. Except for the somewhat aberrant phenotypic positions of HG11 strains LMG 13075 and LMG 13076, the establishment of DNA homology groups I and II was supported by the delineation of phena 1 and 2 (level of correlation, 90%), respectively, as revealed by numerical analysis of 136 phenotypic test results. These data indicate that A. eucrenophila and A. encheleia are phenotypically highly related but can be easily separated by testing the production of acid from D-cellobiose and lactose and the assimilation of D-cellobiose. Extended descriptions of both species are given.

Aeromonas popoffii sp. nov., a mesophilic bacterium isolated from drinking water production plants and reservoirs

We examined the taxonomic position of seven Aeromonas isolates, recovered from Flemish and Scottish drinking water production plants and reservoirs, which were previously recognized by numerical analysis of genomic AFLP fingerprints as members of an unknown Aeromonas taxon that most closely resembled the species Aeromonas bestiarum (DNA hybridization group [HG] 2). The new phenotypic and DNA-DNA hybridization data obtained in this study show that the A. bestiarum-like strains constitute a separate Aeromonas species, for which the name Aeromonas popoffii sp. nov. is being proposed. The new species exhibited an internal DNA relatedness ranging from 79 to 100% and was 22 to 63% related to the type or reference strains of other Aeromonas spp. The highest DNA binding values were determined with A. bestiarum (51 to 63%), followed by Aeromonas hydrophila sensu stricto (HG1; 50 to 60%) and Aeromonas salmonicida (HG3; 39 to 55%). Although fingerprints generated by ribotyping and cellular fatty acid analysis often were highly similar, minor differences between the respective fingerprints were of significance for the differentiation of A. popoffii from its closest taxonomic neighbors, HG1, HG2, and HG3. Phenotypically, all seven strains of A. popoffii were positive for acid and gas production from D-glucose and glycerol, growth in KCN broth, arginine dihydrolase, DNase, Voges-Proskauer reaction, and resistance to vibriostatic agent O/129 and ampicillin but displayed negative reactions for production of urease, tryptophan deaminase, ornithine decarboxylase, and lysine decarboxylase (LDC). None of the strains displayed strong hemolytic activity. The lack of D-sucrose fermentation and LDC production and the ability to utilize DL-lactate as the sole energy and carbon source were useful characteristics for the biochemical separation of A. popoffii from A. bestiarum. Other Aeromonas spp. could be differentiated phenotypically from the new species by at least two features. The chromosomal G+C content of A. popoffii ranges from 57.7 to 59.6 mol%. Strain LMG 17541 is proposed as the type strain.

Deactivation of macrophages with interleukin-4 is the key to the isolation of Tropheryma whippelii

Whipple's disease is a systemic illness caused by a specific agent. Despite recognition of bacteria in lesions, efforts to isolate the causative agent remained futile. A novel strategy was devised to culture Whipple bacilli in deactivated mononuclear phagocytes. Infected tissue was inoculated into human phagocytes deactivated with interleukin (IL)-4, IL-10, and dexamethasone. Within 8-10 days, diastase-resistant periodic acid-Schiff-positive inclusions appeared, corresponding to intact and degenerating bacteria shown to be Tropheryma whippelii by electron microscopy and molecular analyses. T. whippelii was passaged several times in deactivated monocytes and a monoblastic cell line. Time-kinetics growth studies and comparative polymerase chain reaction analysis documented multiplication of T. whippelii in deactivated macrophages. Complementary studies showed that IL-4 rendered phagocytes permissive for T. whippelii, a strong indication that host factors contribute to the pathogenesis of Whipple's disease. The propagation of T. whippelii will permit microbiologic, immunologic, seroepidemiologic, and therapeutic studies of this pathogen.

[Molecular biology detection and antibiotic sensitivities of Shigella spp. and entero-invasive Escherichia coli (EIEC) in patients returning from the tropics]

1579 stool samples from patients with travel-associated diarrhea were examined by conventional culture methods to detect Shigella spp. (48 positive samples or 3.2%) and by PCR to detect shigellae and enteroinvasive Escherichia coli (EIEC) (87 positive samplers or 5.8%). The numerical relation of shigellae to EIEC in PCR-positive samples was about 60 to 40%. However, the lack of discrimination between shigellae and EIEC is not important for the physician because the choice of antibiotics remains the same.

[Acute gonarthritis--application of current diagnostic study methods exemplified by a case report]

The evaluation of acute inflammatory knee arthritis deserves special emphasis, because immediate benefit may result from identification and treatment of the underlying disease. The diagnostic approach to and the differential diagnosis of an acute knee arthritis are presented. By means of a case report, the use of the needle arthroscopy and the polymerase chain reaction (PCR) method for analysis of synovial fluid and synovial tissue in the diagnosis and evaluation of treatment of Lyme disease is described. The significance of this approach in diagnostic and therapeutic procedures has yet to be defined.

Spondylodiscitis caused by Tropheryma whippelii

We describe the first case of spondylodiscitis caused by Tropheryma whippelii in which this so far unculturable organism was shown to be present at the site of infection in a patient without significant gastrointestinal symptoms. The methods used included broad-range PCR amplification with universal primers complementary to constant sequences of the gene coding for 16S rRNA, direct sequencing of the amplified fragment, and comparison of the sequence determined with those deposited in sequence databases. In addition to demonstrating the presence of this organism in the affected vertebral body, we found in our patient that the specific PCR is more sensitive than histology for detecting Whipple's bacilli in bowel biopsy specimens. Because histology of small bowel biopsies from the duodenum were-in contrast to PCR from the same site-not diagnostic for Whipple's disease in our patient, we recommend PCR whenever Whipple's disease has to be excluded.

Stool cultures for Shigella spp: improved specificity by using MacConkey agar with xylose

A total of 678 stool specimens were cultured on four different agars: on xylose-lysine-desoxycholate agar (XLD), MacConkey agar (Mac), MacConkey agar supplemented with xylose (Mac-X), and Hektoen enteric agar (HE). Isolation rates for shigellae were 77% on HE, 86% on Mac and Mac-X, and 91% on XLD. The specificities of the media were 61% for Mac, 75% for HE, and 78% for XLD and Mac-X. After overnight incubation, Mac-X is much easier to read than XLD, which requires incubation for at least 22 hours. Based on these results and also on the practical aspect that incubation for 22-21 hours does not fit well in our schedule, we now use Mac-X whenever shigellae need to be looked for (i.e. mainly patients with recent travel to tropical countries). As compared to our previous procedure the workload in the laboratory could be reduced by about 20%.

[Detection of Bartonella (Rochalimaea) henselae/B. quintana by polymerase chain reaction (PCR)]

Bartonella (Rochalimaea) henselae and/or B. quintana are the causative agents of a variety of infections such as trench fever, bacillary angiomatosis, septicemia, peliosis hepatis and endocarditis. Recently, B. henselae has been identified as a major cause of cat scratch disease. Diagnosis of such infections is based on clinical information, histopathology, culture and serology. However, none of these methods alone is sufficiently sensitive or specific. We have used the PCR to search for DNA specific for B. henselae/B. quintana in 33 clinical samples and in 6 controls. In comparison with clinical data and histopathology, PCR was extremely specific (100%) and reasonably sensitive (61%). Possible explanations for the limited sensitivity of PCR are discussed. We conclude that PCR provides a useful adjunct for the diagnosis of infections caused by B. henselae and B. quintana.

Molecular analysis of Salmonella enteritidis by pulsed-field gel electrophoresis and ribotyping

A total of 61 isolates of Salmonella enteritidis were analyzed by the techniques of pulsed-field gel electrophoresis (PFGE) and ribotyping. Twenty-three of the isolates were from Zurich, Switzerland, and 38 isolates were from the University Hospital, Kuala Lumpur, Malaysia. Five of the Malaysian isolates were hospital-related outbreak strains and were shown to be indistinguishable by PFGE analysis following digestion with three different restriction endonucleases, XbaI (5'-TCTAGA-3'), SpeI (5'-ACTAGT-3'), and AvrII (5'-CCTAGG-3'). The PFGE pattern of an isolate from a suspected carrier staff nurse was found to be identical to those of the hospital outbreak isolates. These isolates were also indistinguishable by ribotyping with SmaI and SphI. The same single PFGE pattern was also detected in 29 of 32 sporadic isolates of S. enteritidis. Four closely related ribotypes were detected among these 29 isolates. Similarly, outbreak-related strains from Switzerland showed close genetic identity by PFGE and ribotyping. Strains obtained from poultry showed more variations in their PFGE patterns and ribotypes, although the patterns were still closely related. In addition, SphI ribotypes A and D among the Swiss strains correlated with phage types 4 and 8, respectively. No correlation of phage types with PFGE pattern was noted. Both PFGE and ribotyping indicate that the S. enteritidis strains circulating in Malaysia and Switzerland are very similar and may be clonally related. Comparison of the PFGE patterns with the ribotypes for 23 Swiss and 16 Malaysian isolates showed that there was a 69% concordance in the grouping of isolates. We conclude that the close genetic similarity observed between epidemiologically unrelated and outbreak-related isolates of S. enteritidis suggests that both PFGE and ribotyping are of limited value in the epidemiological analysis of these particular isolates, possibly because of the highly clonal nature of pathogenic strains of S. enteritidis.

Evaluation of five new plating media for isolation of Salmonella species

A three-phase study was conducted to compare Hektoen enteric agar (HE), Rambach agar (Ra), SM-ID medium (SM), xylose-lysine-Tergitol 4 agar (XLT4), novobiocin-brilliant green-glycerol-lactose agar (NBGL), and modified semisolid Rappaport-Vassiliadis medium (MSRV) for the recovery of nontyphoid salmonellae from stool specimens. After evaluation of the first two phases, which resulted in the elimination of Ra, SM, and NBGL, 593 consecutive stool samples were investigated by plating them directly and after tetrathionate enrichment at 37 degrees C on HE, XLT4, and MSRV. A total of 82 Salmonella-positive stool specimens were detected (positivity rate, 13.8%). Sensitivities for direct plating and after tetrathionate enrichment were 32.9 and 86.6%, respectively, for XLT4, 63.4 and 100.0%, respectively, for MSRV, and 34.1 and 79.3%, respectively, for HE. Specificities (percentage of morphologically suspicious colonies that were indeed salmonellae) were 100.0 and 99.8%, respectively, for XLT4, 99.0 and 98.8%, respectively, for MSRV, and 67.9 and 75.0%, respectively, for HE. The use of MSRV instead of HE increased the isolation rate of salmonellae by 26.2% (65 versus 82 strains isolated from HE and MSRV, respectively). We conclude that MSRV is the most sensitive medium tested and is a very specific medium for the isolation of nontyphoid salmonellae from stool specimens. However, its semisolid nature is a disadvantage and requires careful handling in the laboratory, especially when salmonellae are present. XLT4 had a sensitivity comparable to that of HE and a nearly 100% specificity and can be regarded as an alternative for the isolation of nontyphoid salmonellae from stool samples.

Analysis of restriction fragment length polymorphism and ribotyping of multiresistant Stenotrophomonas maltophilia isolated from persisting lung infection in a cystic fibrosis patient

A cystic fibrosis patient was infected by Stenotrophomonas maltophilia over at least 15 months. The bacteria became increasingly resistant to antimicrobial agents. Determination of restriction fragment length polymorphism and ribotyping showed that resistance was due to changes in that S. maltophilia rather than to infection by another strain.

Detection of shigellae, enteroinvasive and enterotoxigenic Escherichia coli using the polymerase chain reaction (PCR) in patients returning from tropical countries

We have used the polymerase chain reaction (PCR) to detect shigellae, EIEC and ETEC in stool specimens of diarrhoeic patients returning from tropical countries. As compared to culture (7.1% positive specimens), which recognizes only Shigella strains, PCR performed on bacterial growth from directly inoculated MacConkey agar plates and directed against virulence-associated genes present in both Shigella and EIEC was positive in 19.8% of the samples. We assumed that these additional positive results represent true rather than false positive samples because identical results for each single specimen were obtained using two different PCR systems and because positive results (culture as well as PCR) were exclusively found in patients with recent travel but not in those who acquired diarrhoea in a developed country where these organisms are not endemic. PCR detecting LT- and ST-specific sequences was positive in 18.5% of the patients with recent travel. Again no positive cases were identified in controls. Combining PCR and culture results, at least one bacterial pathogen was found in more than 50% of the patients with recent travel. We conclude that PCR is superior to culture methods for the detection of Shigella, EIEC and ETEC in travel-associated diarrhoea.

Development of resistance to macrolide antibiotics in an AIDS patient treated with clarithromycin for Campylobacter jejuni diarrhea

In an AIDS patient with diarrhea, identical isolates of Campylobacter jejuni susceptible and, later, resistant to macrolide antibiotics were isolated from feces before and after treatment with clarithromycin. Results of rRNA gene restriction analysis and serotyping suggest that development of resistance rather than simultaneous infection with a susceptible and a resistant strain was responsible for this phenomenon. This is the first report of in vivo development of resistance by Campylobacter jejuni in a patient treated with a macrolide for Campylobacter jejuni infection.

Comparison of two methods for detecting intrathecal synthesis of Borrelia burgdorferi-specific antibodies and PCR for diagnosis of Lyme neuroborreliosis

An indirect immunofluorescence assay (IFA), a commercial capture enzyme-linked immunosorbent assay (ELISA), and PCR were compared for the diagnosis of Lyme neuroborreliosis in 16 individuals. Borrelia burgdorferi-specific intrathecal immunoglobulin G was found in 10 of 16 patients by IFA and in 8 of 12 patients by capture ELISA. PCRs performed on cerebrospinal fluid samples stored at -70 degrees C were positive for one of eight children and one of four adults with intrathecal antibody production and negative for all four adults without intrathecal antibody production. For two children with facial palsy following erythema chronicum migrans, neither IFA nor capture ELISA detected specific intrathecal antibodies and PCR was also negative. We conclude that both clinical manifestations and laboratory parameters are important for the diagnosis of Lyme neuroborreliosis.

Turicella otitidis gen. nov., sp. nov., a coryneform bacterium isolated from patients with otitis media

The partial 16S rRNA gene sequences of some coryneform bacteria isolated from middle-ear fluids from patients with otitis media were determined. A comparative analysis performed with rRNA sequences of other high-G + C-content gram-positive bacteria showed that the coryneform bacteria isolated from otitis media patients were only remotely related to members of previously described genera. On the basis of the results of the phylogenetic analysis and previously published biochemical and chemotaxonomic data, we propose that the strains isolated from middle-ear infections should be classified in a new genus, Turicella, as Turicella otitidis gen. nov., sp. nov. The type strain of T. otitidis is strain DSM 8821.

Molecular epidemiology of Salmonella enteritidis

Sixteen strains of Salmonella enteritidis isolated in 1991 from 13 unrelated poultry-associated sources, 7 strains from 2 community outbreaks, and 18 human sporadic isolates were investigated by phage typing, analysis of rRNA gene restriction patterns (ribotyping) and plasmid profiles. Four different phage types and 10 SphI patterns were found, whereas plasmids were identical in all but 4 isolates. Only one ribotype (RT A) occurred among both human and avian strains. This particular ribotype was also responsible for the two outbreaks investigated, suggesting that such strains may be of special significance for the increase of S. enteritidis infections.

Nontoxigenic Corynebacterium diphtheriae isolated from intravenous drug users

During a prospective study 117 intravenous drug users were screened for infection with Corynebacterium diphtheriae. Nontoxigenic C. diphtheriae was found in 5 of 132 throat swab specimens and in 5 of 28 skin ulcer specimens taken from July 1991 to April 1992. When phenotypic and molecular typing methods were used, these 10 strains were shown to belong to a single clone. During the same period no strain was isolated from 200 controls. Clinical manifestations of infection were not clearly attributable to C. diphtheriae--no typical membranous pharyngitis was present. The presence of a single clone among homeless intravenous drug users in Zurich indicates the presence of C. diphtheriae in parts of the population with poor standards of hygiene and low socioeconomic status.

[Effect of ciprofloxacin therapy in duration of bacterial excretion in acute salmonella gastroenteritis]

In view of the increasing incidence of non-typhoid salmonellosis, the effect of early treatment with ciprofloxacin on the permanent elimination of salmonella was evaluated. In a prospective study, 14 patients with non-typhoid salmonellosis were treated with 2 x 500 mg/d ciprofloxacin for 10 days within 5 days of onset of symptoms. Relapse occurred in 4/14 (29%) patients 2-3 weeks after termination of therapy. Using sero- and ribotyping, relapse was confirmed and reinfection ruled out in 4/4 patients. Furthermore, ribotyping suggested double infection in one patient. Development of resistance to ciprofloxacin was not observed. We conclude that the use of antimicrobial chemotherapy to treat non-institutional salmonellosis in immunocompetent patients cannot generally be recommended but must be considered carefully in each case. Indications for ciprofloxacin therapy in the treatment of non-typhoid salmonellosis are discussed.

Isolation of Escherichia fergusonii from four different sites in a patient with pancreatic carcinoma and cholangiosepsis

Escherichia fergusonii was isolated from a 69-year-old male with pancreatic carcinoma and cholangiosepsis from gallbladder fluid, three blood cultures, feces, and a superficial wound of the abdomen. Biochemical reactions, antimicrobial susceptibility patterns, susceptibility to polyvalent phage 0-1, and rRNA gene restriction analysis suggested that the four strains were of clonal origin. Our data indicate that E. fergusonii possesses a pathogenic potential in humans.

Ribotyping of Pseudomonas aeruginosa strains isolated from surgical intensive care patients

To elucidate the sources of Pseudomonas aeruginosa on a surgical intensive care unit, rDNA restriction fragment length polymorphism analysis (ribotyping) was applied to analyze strains isolated during a 4-month prospective study. Samples included 1635 from 153 patients, 2463 from 97 staff members, and 581 from the environment. Only 18 patients were colonized. Isolation from their animate and inanimate environment was very low, with 3 and 2 samples, respectively, being positive. Samples from tap water were negative. Ribotyping could easily distinguish 16 different digest patterns with identical follow-up isolates of the same patient. Horizontal transmission occurred only twice. The discriminatory power of ribosomal DNA in differentiating strains was dependent on the restriction enzymes used; among eight different enzymes, PvuII was the most sensitive, producing 15 different patterns. Ribotyping showed high sensitivity in typing P. aeruginosa isolates and confirmed that colonization occurs from endogenous rather than from exogenous sources.

Isolation of gram-positive rods that resemble but are clearly distinct from Actinomyces pyogenes from mixed wound infections

Beginning in 1990, gram-positive rods resembling Actinomyces pyogenes were found with increasing frequency in mixed cultures from various infectious processes, most of them from patients with otitis, empyema, pilonidal cysts, perianal abscesses, and decubitus ulcers. Ribotyping and hybridization showed that these gram-positive rods could be divided into five groups not related to known Actinomyces species. Biochemical markers for reliable differentiation into these groups, however, could not be found. Therefore, naming new species is not warranted unless parameters are discovered that allow identification without DNA hybridization. These gram-positive rods have been isolated only in mixed cultures with anaerobes, Staphylococcus aureus, Streptococcus "milleri," enterococci, and gram-negative rods. Their exact role in these possibly synergistic infections needs further investigation.

Characterization of Listeria strains from a foodborne listeriosis outbreak by rDNA gene restriction patterns compared to four other typing methods

The rDNA gene restriction patterns of 134 isolates of Listeria species were determined with pKK3535--a pBR322 derived plasmid containing an Escherichia coli rRNA operon--used as a probe following digestion of chromosomal DNA by EcoRI endonuclease. Nineteen reference and type strains representing all species and serotypes of Listeria showed 17 distinct ribotypes. One hundred and fifteen wild strains of Listeria monocytogenes were ribotyped and the results were compared to those of serotyping, phage typing, multilocus enzyme electrophoresis (MEE) and restriction endonuclease analysis (REA). Ninety-six Listeria monocytogenes serotype 4b wild strains displayed six distinct ribotypes (I-VI), 72% (69/96) of them clustering in two very close rDNA patterns (I and II) of eight and nine bands, respectively. The same 96 strains displayed six REA patterns and eight MEE electrotypes. Among the 96 Listeria monocytogenes 4b isolates, the 34 epidemic strains defined by phage typing and by epidemiological data all belonged to one ribotype (ribotype I) representing 56% of the strains belonging to this ribotype. These same 34 epidemic strains were also grouped by REA and MEE typing in a unique profile (REA-A) and MEE electrotype (ET 1). Twenty-two Listeria monocytogenes strains of serogroup 1/2 analyzed by rDNA typing showed nine distinct ribotypes. For the 96 Listeria monocytogenes 4b strains studied, the discriminatory index was highest for phage typing and for any combination including phage typing. Ribotyping appears to be a well reproducible molecular typing method and could be a useful complement to other typing methods for the epidemiological study of listeriosis.

Comparison of Rambach agar, SM-ID medium, and Hektoen Enteric agar for primary isolation of non-typhi salmonellae from stool samples

Stool samples (n = 504) were streaked simultaneously onto Rambach agar (R agar; E. Merck, Darmstadt, Germany), SM-ID medium (bioMérieux S.A., Montalieu-Vercieu, France), and Hektoen Enteric (HE) agar (BBL Becton-Dickinson, Baltimore, Md.) in order to evaluate the performances of the first two media in comparison with that of the well-established HE agar. Following overnight cultivation at 37 degrees C, 29 samples (5.8%) were positive for non-typhi salmonellae on at least one of the three media. Sensitivities and specificities were 69 and 98%, 79 and 85%, and 100 and 79% for R, SM-ID, and HE agars, respectively. On the basis of the poor sensitivities, R and SM-ID agars are not recommended as primary plating media when screening for non-typhi salmonellae. However, the high specificity of R agar may help to reduce the work load when this medium is used for plating after enrichment.

[Bacterial pathogens in diarrhea: demonstration of verotoxin-producing Escherichia coli using the polymerase chain reaction]

In 23% of 576 diarrhea patients we were able to demonstrate putative bacterial pathogens. Not included in this number is Clostridium difficile which was found in 8 of 48 (8.3%) specimens analyzed. In addition to Salmonella (8.2%), Campylobacter (6.0%), Aeromonas (2.7%), Shigella (1.9%) and Yersinia (0.8%) we identified verotoxin-producing Escherichia coli (VTEC) in 10 patients (1.9%). VTEC were found as frequently as Shigella (occurring exclusively in patients returning from the tropics) and we propose that VTEC should be routinely assayed in patients with travel-associated diarrhea as well as in those with diarrhea presumably acquired in Switzerland. Established methods for identification of E. coli O157:H7, which include screening for sorbitol-negative Enterobacteriaceae and agglutination, are laborious and insensitive (only 1 of 10 patients with proven VTEC infection positive). The other 9 patients were identified by means of the polymerase chain reaction (PCR). In 7 of these 9 patients we were able to isolate a verotoxigenic strain following a positive PCR result by screening large numbers of colonies. None of them belonged to the O157:H7 serogroup and, in addition, all were sorbitol-positive. The polymerase chain reaction as performed in this study is easy to use, is applicable to large numbers of specimens, and can be regarded as the method of choice for demonstration of VTEC in the clinical diagnostic laboratory.

rRNA gene restriction patterns as taxonomic tools for the genus Aeromonas

In the genus Aeromonas there are at least 13 DNA hybridization groups, which are difficult to differentiate biochemically. We investigated the usefulness of rRNA gene restriction patterns for characterization and identification of the various groups. Genomic DNA was digested with restriction endonuclease SmaI, transferred to a nylon membrane, and hybridized with biotinylated plasmid pKK3535 containing the rrnB operon of Escherichia coli. The SmaI bands at 0.8 to 4 kb but not those at positions corresponding to sizes larger than 4 kb showed a good correlation with hybridization groups, allowing identification of strains to the level of genetic species. We demonstrated that the 567-bp fragment localized between positions 80 and 647 of the 16S ribosomal gene of E. coli was essential for hybridization to the low-molecular-weight fragments, whereas the remainder of the operon did not hybridize to these fragments. On the basis of these results, we concluded that the Aeromonas chromosome contains multiple rRNA operons which may be used for species identification.

Application of ribotyping for differentiating aeromonads isolated from clinical and environmental sources

We have investigated the usefulness of ribotyping for the differentiation of aeromonads isolated from five patients with gastroenteritis and from the source water, treatment plant, and distribution system of a small public water supply. Aeromonas hydrophila and Aeromonas caviae were isolated from fecal specimens preserved in Cary-Blair transport medium by using blood ampicillin agar or alkaline peptone water (pH 8.4) subcultured to blood ampicillin agar plates. A. hydrophila, Aeromonas sobria, and A. caviae were isolated from duplicate 100-ml water samples by the membrane filter technique by using ampicillin dextrin agar for quantitative determination of growth and alkaline peptone water enrichment for detection of the presence or absence of aeromonads below the detection limit of the membrane filter method. In addition, free chlorine residuals and pH values were determined for all water samples and heterotrophic plate counts and total and fecal coliform analyses were performed on them. Ribotyping patterns of aeromonads recovered from well 1, detention basin, sand filter, softener, and distribution samples were compared with those of the five clinical isolates. All patient strains were unique; however, identical ribotypes of A. hydrophila and A. sobria isolated from multiple sites in the water system indicated colonization of a well, sand filters, and the softener, with the potential for sporadic contamination of distribution water. Plant operational deficiencies were noted and corrected. Ribotyping can effectively differentiate otherwise indistinguishable strains of bacteria, thus providing a powerful tool for investigation of waterborne diseases and bacteriological problems within water treatment plants and distribution systems.

Genetic variation among Malaysian isolates of Salmonella typhi as detected by ribosomal RNA gene restriction patterns

Genetic variation among Malaysian isolates of Salmonella typhi was determined by analysis of ribosomal RNA gene restriction patterns. Of the 20 isolates analyzed, eight different pattern combinations were detected. The amount of variation observed was also dependent upon the restriction endonuclease used; PstI produced more different patterns than did SmaI. The results suggested that disease activity was due to a number of different clones circulating simultaneously rather than a single strain. Further implications of the data are discussed.

Numerical classification and identification of Aeromonas genospecies

A total of 176 Aeromonas strains representing all currently characterized genospecies were tested for 329 biochemical characters. Overall similarities of all strains were determined by numerical taxonomic techniques, the UPGMA algorithm and the SSM and the SJ coefficients as measures of similarity. Sixteen clusters (two or more strains) and seven unclustered strains were recovered at the 93.5% similarity level (SSM). Genospecies 1, 4, 5, 6, 7, 9, 12 and 13 were largely represented by single phena, whereas strains of genospecies 2 and 3 were found in closely-related phena. Strains belonging to genospecies 8 formed two distinct biotypes. Strains belonging to genospecies 11 formed a subcluster within a cluster representing different genospecies. In general, similar groupings were obtained with the Jaccard coefficient at a similarity level of 80.0% (SJ) with minor changes in the definition of clusters. The phenetic data showed good correlation with the taxa defined by DNA/DNA hybridization and those obtained by multilocus enzyme analysis. For all genospecies (independent from cluster assignment) 30 diagnostic characters were selected to construct a matrix for probabilistic identification. The correct identification rate of the matrix was 71.51% taking a Willcox probability greater than 0.99, and 83.7% taking a Willcox probability greater than 0.9 as identification threshold levels.

Siderophore production and DNA hybridization groups of Aeromonas spp

A correlation between the genospecies (DNA-DNA hybridization group) and the type of siderophore produced by 118 isolates of the genus Aeromonas was established. Organisms in hybridization groups 1 through 5 (including 5A, 5B, and 5AB) and group 12 predominantly produced the siderophore amonabactin, while an enterobactinlike siderophore was prevalent in groups 8/10 and 9. The siderophore produced by strains in group 6 may be an as-yet-unidentified nonphenolate, nonhydroxamate compound, and group 7 isolates synthesized no siderophores. Determination of the indigeneous siderophore (or the absence of one) produced by an isolate of the genus Aeromonas may assist in identification of the organism's genetic species and may suggest the presence of certain virulence properties.