One-step cloning and expression of Clostridium difficile toxin B gene (tcdB)

The toxin genes of Clostridium difficile have been previously cloned by reconstructing the entire gene in a series of steps in sequence using several cloned fragments. Amplification of a 7.9 kb fragment corresponding to the toxin B gene (tcdB) was obtained with EXPAND Long Template PCR system. The amplified fragment was inserted into the E. coli expression vector pBAD and cloned into competent E. coli TOP 10 cells. tcdB gene sequences representing the complete toxin gene were detected in 3/120 (2.5%) clones analyzed. Culture filtrates of 2/3 clones were found to have cytotoxic activity in human lung fibroblasts. The recombinant protein expressed in E. coli was identified as toxin B by Western immunoblot analysis using C. sordellii antitoxin. This rapid cloning method may be useful in determining the role that individual genes in the pathogenicity locus (PaLoc) play in the virulence of C. difficile. Our results also suggest that the activity of toxin B is independent of other genes in the PaLoc.

Electroporation of DNA sequences from the pathogenicity locus (PaLoc) of toxigenic Clostridium difficile into a non-toxigenic strain

Toxigenic Clostridium difficile is the etiologic agent of C. difficile-associated diarrhoea (CDAD), the most common cause of hospital-acquired infectious diarrhoea. The genes tcdA and tcdB, which encode for the toxin A and B proteins, are part of the pathogenicity locus (PaLoc) of toxigenic C. difficile. Genetic and virulence studies at the molecular level in C. difficile have been hindered by the lack of techniques for DNA manipulation in this species. We describe the electroporation of DNA fragments from a toxigenic isolate into a non-toxigenic strain of C. difficile. Using previously described methods of electroporation into Clostridium spp., the complete toxin B gene and polymerase chain reaction (PCR) fragments of the PaLoc were cloned and electroporated into a non-toxigenic strain of C. difficile. The resulting transformed clones were screened for the introduced gene fragments by PCR, which confirmed their presence. This is the first description of introduction of DNA into C. difficile by electroporation.

Rapidly growing tumor-like brain lesion

Listeria monocytogenes accounts for 8-11% of the cases of bacterial meningitis which is associated with high mortality in patients with serious underlying diseases or those receiving immunosuppressive treatment. Brain abscess due to L. monocytogenes is a very rare occurrence. The case reported here concerns a 54-year-old female patient with a rapidly growing tumor-like brain lesion. L. monocytogenes type 4b could be cultured from blood and brain biopsy. Despite antimicrobial therapy with ampicillin and gentamicin, the patient died 11 days after admission to the hospital. The growing numbers of elderly and immunocompromised patients will increasingly confront physicians with patients with listeriosis. Delayed therapy in patients treated with corticosteroids may result in a fatal outcome.

Comparative in vitro activities of gemifloxacin, other quinolones, and nonquinolone antimicrobials against obligately anaerobic bacteria

The in vitro activity of gemifloxacin was compared to that of other quinolone and nonquinolone antimicrobials against 204 anaerobes by the agar dilution technique. The data indicate that gemifloxacin has a rather selective anaerobic activity. Most Peptostreptococcus, Porphyromonas, and Fusobacterium species are susceptible, while gemifloxacin's activity against other gram-negative anaerobes appears to be variable.

Infections caused by Stenotrophomonas maltophilia--a prospective study

BACKGROUND

Stenotrophomonas maltophilia is an opportunistic microorganism, often highly resistant to routinely tested antibiotics. This microorganism is isolated in specimens from patients with nosocomial infections with increasing frequency.

PATIENTS AND METHODS

During a 1-year period (1998/1999) S. maltophilia was isolated from 137 specimens (0.26% of all investigated specimens) from 80 patients who were treated in a 1,500 bed major tertiary care teaching hospital in Leipzig. The data of 76 patients (133 specimens) could be collected and analyzed completely.

RESULTS

The pathogen was most frequently detected in specimens from the respiratory tract (54%). In five patients (six cases) S. maltophilia was isolated from blood cultures (0.3% of all positive blood cultures; 1.4% of all gram-negative isolates from blood cultures). 70 of the infected patients were inpatients and 32 (42%) of them were treated on the internal medicine wards. Of these 32 patients only six (19%) were pretreated with imipenem. The Length of stay at the hospital resulted in an independent increased risk of infection with S. maltophilia. In addition, this organism was detected in six infected outpatients.

CONCLUSION

S. maltophilia is not only a nosocomial pathogen. Pretreatment with a carbapenem is no longer an unequivocal risk factor for an infection with S. maltophilia.

Resistance to moxifloxacin in toxigenic Clostridium difficile isolates is associated with mutations in gyrA

Clostridium difficile is the etiological agent of antibiotic-associated colitis and the most common cause of hospital-acquired infectious diarrhea. Fluoroquinolones such as ciprofloxacin are associated with lower risks of C. difficile-associated diarrhea. In this study, we have analyzed 72 C. difficile isolates obtained from patients with different clinical courses of disease, such as toxic megacolon and relapses; the hospital environment; public places; and horses. They were investigated for their susceptibilities to moxifloxacin (MXF), metronidazole (MEO), and vancomycin (VAN). Mutants highly resistant to fluoroquinolones were selected in vitro by stepwise exposure to increasing concentrations of MXF. The resulting mutants were analyzed for the presence of mutations in the quinolone resistance-determining regions of DNA gyrase (gyrA), the production of toxins A and B, and the epidemiological relationship of these isolates. These factors were also investigated using PCR-based methods. All strains tested were susceptible to MEO and VAN. Twenty-six percent of the clinical isolates (19 of 72) were highly resistant to MXF (MIC > or = 16 microg/ml). Fourteen of these 19 strains contained nucleotide changes resulting in amino acid substitutions at position 83 in the gyrA protein. Resistant strains selected in vitro did not contain mutations at that position. These findings indicate that resistance to MXF in a majority of cases may be due to amino acid substitution in the gyrA gene.

Phototherapy of psoriasis: comparative experience of different phototherapeutic approaches

BACKGROUND

Broad-band UVB alone or in combination with different topical drugs (anthralin, calcipotriol), systemic PUVA and bath-PUVA therapy are very effective and well-established treatment modalities for psoriasis.

OBJECTIVE

The aim of this retrospective study was to assess which of these routinely applied phototherapeutic modalities might be most effective and safe for the treatment of plaque-type psoriasis.

METHODS

Patients (n = 203) with moderate to severe (pretreatment Psoriasis Area and Severity Index score between 12 and 35) chronic plaque-type psoriasis treated between 1992 and 1998 at our department with either UVB (with/without anthralin or calcipotriol; n = 97), systemic PUVA (n = 19) or bath-PUVA therapy (n = 87) were evaluated for efficacy, duration of treatment, number of treatments necessary for complete remission (CR), cumulative light dose, side effects of therapy and duration of remission after therapy.

RESULTS

No statistically significant difference comparing the efficacy of bath-PUVA (CR in 72.4%), PUVA (CR in 89.5%) and UVB phototherapy (CR in 69.1%) was found. Although the duration of therapy was significantly longer for bath-PUVA (66 +/- 42 days) as compared to UVB treatment (50 +/- 27 days), the mean number of treatments did not differ significantly between bath-PUVA (28 +/- 12), UVB therapy (30 +/- 12) and PUVA (26 +/- 13). Significantly fewer side effects of phototherapy were observed with bath-PUVA (14.9%) therapy compared to UVB treatment (30.9%). Also, the duration of remission after successful therapy was significantly longer for bath-PUVA (8.4 +/- 3.5 months) as compared to UVB phototherapy (5.1 +/- 4.2 months).

CONCLUSION

Bath-PUVA therapy has some advantages over UVB phototherapy in the treatment of psoriasis: fewer UV-related acute side effects and a longer period of remission after therapy. However, the choice of treatment with either UVB, bath-PUVA or systemic PUVA should also be based on a history of previous response to treatment and patient considerations, including compliance and responsibility for following the precautions to avoid potential side effects.

Isolation of Clostridium innocuum from cases of recurrent diarrhea in patients with prior Clostridium difficile associated diarrhea

Clostridium innocuum isolates resistant to vancomycin (MIC values of 16-24 microg/mL) were isolated from three patients with recurrent Clostridium difficile -associated diarrhea (CDAD). We discuss the clinical significance and problems associated with the identification and differentiation of these two clostridial species, which may result in misdiagnosis of patients.

Pericarditis after allogeneic peripheral blood stem cell transplantation caused by Legionella pneumophila (non-serogroup 1)

A case of Legionella pericarditis caused by a Legionella pneumophila isolate other than serogroup 1 is reported in a 59-year-old man after allogeneic peripheral blood stem cell transplantation. On admission a 5 mm pericardial effusion was detected on echocardiography. Antibodies were detected against L. pneumophila serogroups 7 to 14 using the antigen pool and against serogroup 12 alone. Antibodies were not detected against the serogroup 1 to 6 antigen pool. The patient's clinical condition improved dramatically after treatment with clarithromycin and an echocardiography revealed the total disappearance of the pericardial effusion.

[Fluorescence-assisted biopsy of basal cell carcinomas]

BACKGROUND AND OBJECTIVE

The diagnosis of precancerous and cancerous skin lessons in pretreated or scarred skin can be difficult. The determination of the right biopsy site in a suspected area depends largely on the physician's experience.

PATIENTS/METHODS

The possibility of using a CCD-camera system and measuring tumor fluorescence following topical application of 5-aminolevulinic acid was employed in a single case to facilitate accurate choice of biopsy site.

RESULTS

An user-independent evaluation of the induced fluorescence intensity was achieved by means of the described optical system and digital imaging. The contrast of the acquired fluorescence images can be significantly enhanced and allows the determination of a threshold. As result an initial, clinically not visible basal cell carcinoma was detected and excised by a punch biopsy in toto.

CONCLUSIONS

Using the described optical system the early recognition of a superficial basal cell carcinoma and the determination of the exact biopsy site was achieved in pretreated skin. The routine employment of the system will be assessed in a prospective study.

In vitro activities of fourteen antimicrobial agents against obligately anaerobic bacteria

The in vitro activities of fourteen antimicrobial agents were tested against 292 clinical isolates of obligately anaerobic bacteria using the broth microdilution technique. Taking all strains as a group the MIC(50/90) (mg/l) values were metronidazole and imipenem 0.25/1, meropenem 0.25/0.5, trovafloxacin 0.25/1, gatifloxacin and moxifloxacin 0.5/2, levofloxacin 2/16, ciprofloxacin 4/32, clindamycin 0.5/8, amoxycillin/clavulanate 1/4, doxycycline and chloramphenicol 2/4, erythromycin 4/>32 and penicillin G 16/>32.

In vitro activity of telithromycin (HMR 3647) and seven other antimicrobial agents against anaerobic bacteria

We assessed the in vitro activity of telithromycin (HMR 3647) and seven other antimicrobials against 292 strains of obligately anaerobic bacteria. MICs were determined with the microdilution technique and Wilkins-Chalgren broth according to DIN 58940-83. MIC50/MIC90s (mg/L) for telithromycin were 4/4 for Bacteroides fragilis, Bacteroides ovatus and Bacteroides thetaiotaomicron, 2/4 for Fusobacterium spp. and Bilophila wadsworthia, 2/2 for Bacteroides caccae, 1/4 for Bacteroides vulgatus, 0.25/4 for Prevotella spp., > or =0.03/0.5 for Clostridium spp. and 0.125/4 for Peptostreptococcus spp.

Comparative activity of moxifloxacin in vitro against obligately anaerobic bacteria

The antimicrobial activity of moxifloxacin and seven other antibiotics (four of them quinolones) against 292 strains of obligately anaerobic bacteria was assessed employing a broth microdilution technique performed in Wilkens-Chalgren broth. MIC50/MIC90 values (mg/l) for moxifloxacin were as follows: Bacteroides fragilis (n = 62) 0.25/2, Bacteroides ovatus (n = 70) 1/4, Bacteroides vulgatus (n = 29) 0.25/1, Bacteroides thetaiotaomicron (n = 17) 2/2, Bacteroides caccae (n = 11) 1/2, Prevotella spp. (n = 11) 0.25/2, Fusobacterium spp. (n = 17) 1/4, Bilophila wadsworthia (n = 29) 0.5/1, and Clostridium spp. (n = 29) 0.125/0.5, respectively. MIC50 values (mg/l) for Bacteroides distasonis (n = 8) and Peptostreptococcus spp. (n = 9) were 0.25. The results indicated that moxifloxacin was almost as active as trovafloxacin, as active as gatifloxacin, and more active than levofloxacin and ciprofloxacin against the anaerobes tested.

In vitro activities of gatifloxacin, two other quinolones, and five nonquinolone antimicrobials against obligately anaerobic bacteria

The activity of the new fluoroquinolone gatifloxacin was compared with those of other quinolones and antimicrobial agents of other classes against 294 anaerobes by the broth microdilution technique. For all strains tested, gatifloxacin MICs at which 50 and 90% of the isolates were inhibited were 0.5 and 2 mg/liter, respectively, and were 3 to 4 dilution steps lower than, e.g., ciprofloxacin.

Simulations on the selectivity of 5-aminolaevulinic acid-induced fluorescence in vivo

The knowledge of the exact time course of a photosensitizer in tumour and surrounding host tissue is fundamental for effective photodynamic therapy (PDT) and fluorescence-based diagnosis. In this study the time course of porphyrin fluorescence following topical application of 5-aminolaevulinic acid (ALA) using different formulations, concentrations and incubation times has been measured in amelanotic melanomas (A-Mel-3) (n = 54) grown in transparent dorsal skinfold chambers of Syrian golden hamsters and in human basal cell carcinomas (BCCs) (n = 40) in vivo. To simulate the accumulation of ALA-induced protoporphyrin IX (Pp IX), a three-compartment model has been developed and rate constants have been determined. The kinetics of both the A-Mel-3 tumours and the BCCs show a significantly higher fluorescence intensity in tumour as compared to normal surrounding host tissue. Maximal fluorescence intensity in A-Mel-3 tumours as a percentage of the reference standard used occurs 150 min post incubation (p.i.) using a 1, 3 or 10% (vol.) ALA solution buffered to pH 7.4 and 1 h incubation time. After a 4 h incubation time maximal fluorescence intensity in tumour is measured shortly p.i. A concentration of 10% ALA does not increase the fluorescence intensity as compared to 3% ALA following 4 h incubation, but either 3 or 10% ALA yields a significantly higher fluorescence after 4 h incubation time as compared to 1 h. The fluorescence intensity following an 8 h incubation reaches its maximum directly p.i. for all concentrations and then decreases exponentially. The fluorescence intensity in the surrounding host tissue shows no statistically significant difference regarding concentration or incubation time. At least during the first hour p.i., the fluorescence intensity measured in the surrounding tissue is lower as compared to that in the tumour in all groups. 24 h after topical application hardly any fluorescence is detectable in tumour or surrounding host tissue in all experimental groups. Incubating human BCCs with a 20% ALA cream (water-in-oil emulsion) or a 20% ALA gel (containing 40% dimethyl sulfoxide) for approximately 2 h yields a similar fluorescence intensity directly after incubation for either cream or gel. However, while yielding a maximum 120 min p.i. with cream, the fluorescence intensity increases for a longer time (about 2-3 h p.i.) and up to higher values using the gel formulation. In surrounding normal skin, cream as well as gel formulation yields a similar fluorescence intensity directly after incubation. Afterwards the fluorescence intensity decreases slowly using the cream whereas a further increase of the fluorescence intensity is measured in the normal skin with a maximum 240 min p.i. using the gel formulation. The results of the proposed three-compartment model indicate that the observed selectivity of accumulated porphyrins following topical application of ALA is mainly governed by an increased ALA penetration of the stratum corneum of the skin, an accelerated ALA uptake into the cell and a higher porphyrin formation in tumour as compared to normal skin tissue, but not by a reduced ferrocheletase activity.

Mapping of linear antigenic determinants on glycoprotein C of herpes simplex virus type 1 and type 2 recognized by human serum immunoglobulin G antibodies

Using membrane-based dekapeptides, the reactivity of human serum antibodies with linear antigenic determinants of herpes simplex virus (HSV) type 1 and type 2 glycoprotein C (gC-1, gC-2) was studied by pep scan and immunodot assay. The entire coding sequences of gC-1 and gC-2 were screened for the presence of linear epitopes by pep scan. Peptides recognized in an HSV-1 type-specific manner were mainly identified within the N-terminal third and at the C-terminus of gC-1, whereas most type-common antibodies were directed against colinear peptides within the central parts of gC-1 and gC-2. The type-specific reaction of human sera with gC-2 peptides in pep scan was poor. Eight peptides identified as immunoreactive by pep scan were further tested in immunodot assay for their reactivity with a human serum panel. None of the eight HSV-negative sera gave positive results by immunodot assay. Positive reactions with gC peptides were found to be strongly age-dependent, i.e., the rate of positive reactions was significantly higher in HSV-positive adults than in HSV-positive children. Antibody reactivity with two type-common gC peptides was demonstrated in 17 out of 28 HSV-positive sera. A putative type-specific gC-2 peptide employed in immunodot assay was inconsistently recognized by human sera. Twenty HSV-positive sera reacted with at least 1 of 5 type-specific gC-1 peptides. Nine sera showing no reactivity with glycoprotein G of HSV-1 (gG-1) by immunobloting recognized type-specific gC-1 peptides in immunodot assay. Thus, gC-1 peptides might allow the detection of HSV-1-specific antibodies in individuals showing no reactivity with commonly employed HSV-1-specific diagnostic antigenes, i.e., purified or recombinant gG-1.

Biocompatibility testing of a silicone maxillofacial prosthetic elastomer: soft tissue study in primates

Little information exists on the biocompatibility of maxillofacial prosthetic materials. Cosmesil material is a purpose-designed facial prosthetic elastomer that has an established clinical profile in humans but results of biocompatibility testing have not been published. Cosmesil, acrylic resin (positive control), black surgical gutta-percha (negative control), and Silastic 382 material (Dow Corning, Midland, Mich.) (reference control) were processed as custom-designed implants. The implants were inserted into five chacma baboons for a 12-week period in intraosseous, subperiosteal, submucosal, and intramuscular sites. The histologic assessment was based on a modified form of the FDI-ISO Technical Report 7405 for subcutaneous implants. An evaluation was made of capsule formation and inflammatory response. The statistical analysis involved a three-way ANOVA and a Tukey-Kramer Student range test. The critical level of statistical significance chosen was p less than 0.05. The study found that gutta-percha provoked a statistically significantly thicker capsule and a severe inflammatory response. Acrylic resin, Cosmesil material, and Silastic 382 material produced capsule formations and an inflammatory response that did not differ significantly. Cosmesil material is not manufactured as an implant material, but from the present findings it is considered acceptably biocompatible for its intended use where there may be contact with internal tissue spaces that are contiguous to external surfaces.

Processing of holographic AgBr films studied by x-ray fluorescence analysis

The feasibility of using x-ray fluorescence techniques to determine the concentrations of silver, bromine, and iodine in silver halogenide holographic films is studied. A small apparatus employing a 30-mCi (57)Co radioactive source and a germanium photon detector is described. AgBr films were exposed to different amounts of light and subjected to several types of chemical processing, and their silver and halogen contents were investigated. In addition, the relationship between the concentration of absorbing silver in the emulsion and its optical density was determined.

The paradental cyst: a clinicopathologic study of 50 cases

The paradental cyst is an odontogenic cyst of inflammatory origin, which occurs on either the buccal, distal, or (rarely) mesial aspects of partially erupted mandibular third molars. In most cases there is an associated history of recurrent pericoronitis. The clinicopathologic features of 50 cases are reviewed. The frequency of the paradental cyst is 3% to 5% of all odontogenic cysts, although we believe its true incidence to be higher. All cases occur in the mandible, and there is a marked preponderance in males. White persons are affected more frequently than blacks. The size of the cysts varies from 1 to 2 cm; they are attached to the cementoenamel junction (CEJ) and the coronal third of the roots. Histologically, they cannot be distinguished from other inflammatory odontogenic cysts. While origin from junctional epithelium or cell rests of Malassez cannot be entirely excluded, we favor an origin from reduced enamel epithelium and suggest that cyst formation occurs as a result of unilateral expansion of the dental follicle secondary to inflammatory destruction of bone and periodontium.

Does a low-molecular extract of human placenta support ossification?

In the Anglo-American literature, the importance of endogenous resistance in healing traumatic fractures is pointed out. Decades of experimental and practical experience using low-molecular extract of human placenta for the treatment of cancer to intensify endogenous resistance, motivated me to try this therapy on bone lesions in addition to the surgical treatment. Experiments showed an exorbitant increase of alkaline serum-phosphatase, a remarkable atypical intermediate callus phase, and an earlier solid healing than it was observed with comparable control groups. The question about the efficiency of this extract and the relation to problems of resistance cannot be answered and it is not clear, either if the extract could be described as a mesenchymal activator.