[Effects of millimeter wave combined with gamma-ray radiation on human tongue squamous cell carcinoma cell]

OBJECTIVE

To observe the effects of millimeter wave combined with (60)Co gamma-ray radiation on human tongue squamous cell carcinoma cell(Tca8113).

METHODS

Using mm-wave combined with (60)Co gamma-ray to irradiate Tca8113 cell suspensions. The colony forming inhibition efficiency was observed three weeks later. 24 hours after radiation, the samples were observed under electron microscope.

RESULTS

The study showed that the radiation could result in significant decrease of the colony forming efficiency (P<0.001). The inhibition efficiency was higher when the samples were exposed to high power density mm-wave or for a long duration (P<0.05 or P<0.01). The inhibiting effect in combined groups was more obvious than in singly radiated group (P<0.001 or P<0.05). There was no difference between 'R+HL' group and 'HL+R' group (P>0.05). Electron microscopy showed the cells' suprastructures had some injuries and regressive changes. And more serious changes existed in 'H' group.

CONCLUSION

It could be concluded that mm-wave radiation could efficiently inhibit the colony forming capability of Tca8113 cell. And mm-wave radiation could lead to morphological changes of exterior or interior ultrastructures of Tca8113 cell.

Molecular typing methods for the epidemiological identification of Clostridium difficile strains

Toxigenic Clostridium difficile is the etiologic agent of C. difficile-associated diarrhea (CDAD), the most common cause of nosocomial diarrhea. Cross-infection between patients and transmission through the environment and medical personnel are important factors in the acquisition of CDAD. In order to understand differences in epidemiology and pathogenesis, a number of typing schemes have been developed. We will review the typing methods used to study the epidemiology of C. difficile infections and how they have evolved from a phenotypic identification to state of the art molecular methods, detecting genetic polymorphisms among strains. These molecular methods include PCR-based methods (arbitrarily primed-PCR [AP-PCR] and PCR ribotyping), restriction endonuclease analysis (REA) and pulse field gel electrophoresis (PFGE). The application, usefulness and feasibility of these methods are compared and discussed. Finally, the role of genomics as a tool to investigate CDAD is introduced.

Anaerobic bacteria and intrahepatic stones: detections of Clostridium sp. and Bacteroides fragilis

OBJECTIVE

To detect anaerobic bacteria Clostridium sp. and Bacteroides fragilis in intrahepatic stones by molecular genetic method.

METHODS

DNA was extracted from 59 stone samples and subjected to polymerase chain reaction (PCR) amplification targeting the 16S rRNA gene of Clostridium sp. and the glutamine synthetase gene of Bacteroides fragilis. Single-strand conformational polymorphism (SSCP) analysis was performed to identify the Clostridium sp.

RESULTS

16S rRNA gene sequences for Clostridium sp. were identified in 49 stones (83%, 49/59). The two most common groups were detected in 19 (41%) and 17 (37%) of the 46 samples using SSPC analysis, and 25/59 (42%) stones were tested positive for Bacteroides fragilis.

CONCLUSIONS

Anaerobes such as Clostridium sp. and Bacteroides fragilis present in intrahepatic stones and may play a role in stone formation. PCR is a useful technique to detect fastidious pathogens, which are difficult to culture. SSCP of PCR products is a rapid method in differentiating bacterial species.

Genotyping of Bacteroides fragilis isolates from stool specimens by arbitrarily-primed-PCR

In order to determine genetic relatedness of Bacteroides fragilis isolates from different clinical sources, arbitrarily primed polymerase chain reaction (PCR) (AP-PCR) was used to compare 17 strains isolated from patients with inflammatory bowel disease (IBD) and 20 strains isolated from foals with diarrhea. Three reference ATCC strains were also analyzed. Eighteen unique types were identified with a 22-mer arbitrary primer (ERIC-2) among the 20 patient isolates. Types 1 (enterotoxigenic) and 9 (nonenterotoxigenic), were each found in the stools of two patients. All other isolates showed a distinct and unique DNA banding pattern indicating a high degree of genotypic variability. Eleven types were identified among the foal isolates. Type 20, a nonenterotoxigenic type, was present in 30% of the foals. No correlation was found between the human and horse isolates. No clear relationship between a disease state (diarrhea or IBD) and specific types was observed. AP-PCR will be useful as a rapid method to determine genetic relatedness and in future epidemiologic studies of diarrheal diseases due to B. fragilis.

Persistence of an endemic (toxigenic) isolate of Clostridium difficile in the environment of a general medicine ward

The epidemiology of Clostridium difficile-associated diarrhea (CDAD) in an endemic setting was investigated by use of DNA typing methods to determine the strain identity of C. difficile isolates. Two predominant toxigenic clones were found in the environment and accounted for 29.8% (type 1) and 15.5% (type 2) of CDAD cases, respectively. In endemic settings, the environment and cross-transmission may play a role in acquisition of CDAD.

Occurrence of Bacteroides fragilis enterotoxin gene-carrying strains in Germany and the United States

Ninety-three Bacteroides fragilis isolates from different geographic locations were analyzed for the presence of an enterotoxin-encoding gene. It was shown that blood culture isolates were more likely to carry this gene than strains from other sources. All enterotoxin-positive strains belonged to the PCR fingerprint group I.

Isolation and molecular characterization of Clostridium difficile strains from patients and the hospital environment in Belarus

Toxigenic Clostridium difficile is the most common etiologic agent of hospital-acquired diarrhea in developed countries. The role of this pathogen in nosocomial diarrhea in Eastern Europe has not been clearly established. The goal of this study was to determine the prevalence of C. difficile in patients and the hospital environment in Belarus and to characterize these isolates as to the presence of toxin genes and their molecular type. C. difficile was isolated from 9 of 509 (1.8%) patients analyzed and recovered from 28 of 1,300 (2. 1%) environmental sites cultured. A multiplex PCR assay was used to analyze the pathogenicity locus (PaLoc) of all isolates, and strain identity was determined by an arbitrarily primed PCR (AP-PCR). The targeted sequences for all the genes in the PaLoc were amplified in all C. difficile strains examined. A predominantly homogeneous group of strains was found among these isolates, with five major AP-PCR groups being identified. Eighty-three percent of environmental isolates were classified into two groups, while patient isolates grouped into three AP-PCR types, two of which were also found in the hospital environment. Although no data on the role of C. difficile infection or epidemiology of C. difficile-associated diarrhea (CDAD) in this country exist, the isolation of toxigenic C. difficile from the hospital environment suggests that this pathogen may be responsible for cases of diarrhea of undiagnosed origin and validates our effort to further investigate the significance of CDAD in Eastern Europe.

Analysis of the pathogenicity locus in Clostridium difficile strains

The genes for Clostridium difficile toxins A and B (tcdA and tcdB) are part of a 19.6-kb pathogenicity locus (PaLoc) that includes the genes tcdD, tcdE, and tcdC. To determine whether the C. difficile PaLoc is a stable and conserved genetic unit in toxigenic strains, a multiplex polymerase chain reaction was used to analyze 50 toxigenic, 39 nontoxigenic, and 2 toxin-defective isolates. The respective amplicons were identified for tcdA-E in the toxigenic isolates; these were absent in the nontoxigenic isolates. C. difficile P-829 lacked at least a fragment of tcdD, tcdB, tcdE, and tcdC, but tcdA was present. C. difficile 8864 had deletions in the tcdA and tcdC genes. These data suggest that the PaLoc is highly stable in toxigenic C. difficile, nontoxigenic isolates lack the unit, and isolates with a defective PaLoc can still cause clinical disease. Further studies are needed to define the role of individual genes in the pathogenesis of C. difficile-associated diarrhea.

Bacteroides fragilis enterotoxin gene sequences in patients with inflammatory bowel disease

We identified enterotoxigenic Bacteroides fragilis in stool specimens of patients with inflammatory bowel disease and other gastrointestinal disorders. The organism was detected in 11 (13.2%) of 83 patients with inflammatory bowel disease. Of 57 patients with active disease, 19.3% were toxin positive; none of those with inactive disease had specimens positive for enterotoxigenic Bacteroides fragilis gene sequences.

Clostridium difficile: a survey of fecal carriage in cats in a veterinary medical teaching hospital

Fecal samples collected from 245 cats over a 6-month period were analyzed for the presence of Clostridium difficile. After culture on selective media, isolates were identified by a latex agglutination test, and the presence of toxin A and toxin B gene sequences was determined by polymerase chain reaction. Clostridium difficile was isolated from 23 (9.4%) of the cats, and 34.8% of that group were colonized with toxigenic strains. All of the cats colonized with toxigenic C. difficile had > or = 1 of the risk factors (antibiotic use, antineoplastic therapy, immunosuppressive virus infection) associated with C. difficile infection in humans. Clostridium difficile was not found in any of the cats from a clinically healthy outpatient group of cats examined from the same hospital nor in cats from a specific-pathogen-free research colony on the same campus tested during the same time period. The data obtained in this study confirm the presence of C. difficile in cats at a veterinary teaching hospital. DNA fingerprinting analysis of these isolates allowed separation of the strains into 5 groups. Type 4 strain found in 7 cats was also recovered from the floor drain in the same hospital, suggesting a possible source of infection. Whether the organism is of clinical significance in diarrheal diseases of cats remains to be determined.

Detection of Bacteroides fragilis enterotoxin gene by PCR

Bacteroides fragilis constitutes about 1% of the bacterial flora in intestines of normal humans. Enterotoxigenic strains of B. fragilis have been associated with diarrheal diseases in humans and animals. The enterotoxin produced by these isolates induces fluid changes in ligated intestinal loops and an in vitro cytotoxic response in HT-29 cells. We developed a nested PCR to detect the enterotoxin gene of B. fragilis in stool specimens. After DNA extraction, a 367-bp fragment was amplified with two outer primers. The amplicon from this reaction was subjected to a second round of amplification with a set of internal primers. With these inner primers, a 290-bp DNA fragment was obtained which was confirmed as part of the B. fragilis enterotoxin gene by Southern blotting with a nonradioactive internal probe and a chemiluminescence system. By this approach, B. fragilis enterotoxin gene sequences were detected in eight known enterotoxigenic human isolates and nine enterotoxigenic horse isolates. No amplification products were obtained from DNA extracted from 28 nonenterotoxigenic B. fragilis isolates or B. distasonis, B. thetaiotaomicron, B. uniformis, B. ovatus, Escherichia coli, or Clostridium difficile. The sensitivity of this assay allowed us to detect as little as 1 pg of enterotoxin DNA sequences or 100 to 1,000 cells of enterotoxigenic B. fragilis/g of stool. Enterotoxin production of all isolates was confirmed in vitro in HT-29 cells. A 100% correlation was obtained between enterotoxin detection by cytotoxin assay and the nested PCR assay. This rapid and sensitive assay can be used to identify enterotoxigenic B. fragilis and may be used clinically to determine the role of B. fragilis in diarrheal diseases.

Isolation of a toxin B-deficient mutant strain of Clostridium difficile in a case of recurrent C. difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CDAD) recurs in approximately 15%-20% of patients after discontinuation of metronidazole or vancomycin therapy. Most recurrences are believed to be endogenous relapses due to the persistence of spores. However, there is evidence that reinfection with a different strain is a cause of recurrence. We report the case of a patient with a history of multiple episodes of C. difficile colitis. The patient, a 56-year-old female, has had 5 years of repeated recurrences, each shortly after discontinuing vancomycin therapy. During the course of these episodes, three isolates were cultured from her stools at different times. These isolates were analyzed for the presence of toxin A and B gene sequences and genotyped by means of arbitrarily primed polymerase chain reaction (AP-PCR). The original two isolates contained the toxin A and B genes, as determined by PCR, and were of the same AP-PCR type. During her last relapse, a C. difficile strain lacking at least a portion of the toxin B gene was isolated. AP-PCR analysis of this isolate showed a different DNA banding pattern from that of the previous isolates. A vancomycin susceptibility assay revealed a slight decrease in vancomycin activity as compared with that against the prior isolate. This case demonstrates two unique features: (1) recurrent infections can be due to reinfections and (2) toxin B mutants can possibly cause CDAD. This study also raises concerns about long-term vancomycin use and the development of resistance of C. difficile to vancomycin.

Isolation of various genotypes of Clostridium difficile from patients and the environment in an oncology ward

The epidemiology of Clostridium difficile-associated diarrhea (CDAD) is not well defined in nonepidemic situations because precise biotyping techniques have only recently become available. Arbitrarily primed polymerase chain reaction (AP-PCR) was used to determine strain identity of C. difficile isolates recovered on our oncology ward, at an incidence rate of 0.84%. Twenty-one strains of C. difficile, which were grouped into 18 different AP-PCR types, were isolated from patients' specimens. Forty-two C. difficile isolates recovered from the environment (33 toxigenic and 9 nontoxigenic) represented 9 different AP-PCR types. The most commonly found type, a toxigenic strain accounting for 29% of the environmental isolates, was widespread throughout the ward. None of the environmental types were found among the isolates from patients. Three patients' isolates were of the same AP-PCR type, and two of these patients had occupied neighboring rooms at the same time. The diversity of C. difficile isotypes suggests that endemic nosocomial CDAD is not necessarily clonally spread.

Detection of Cryptosporidium parvum DNA in human feces by nested PCR

Cryptosporidium parvum is a coccidian protozoan that causes diarrhea in humans, often chronic and severe in patients with AIDS. Conventionally, diagnosis is made by concentration of stools followed by acid-fast staining (AF) or immunofluorescent staining. The threshold of detection in human stool specimens by these methods may require the presence of 50,000 (immunofluorescent staining) to 500,000 (AF) oocysts per g of stool. In this study, a nested PCR assay was developed to detect C. parvum DNA directly from stool specimens. After extraction of DNA from formalinized stool, a 400-bp fragment of C. parvum DNA was amplified with two 26-mer outer primers. The amplicon from this reaction was amplified with a second primer pair. With these nested primers, a 194-bp DNA fragment was amplified and confirmed as C. parvum DNA by internal probing with an enzyme-linked chemiluminescence system. This PCR-based test allowed the detection of 500 oocysts per g of stool or 100 ng of C. parvum DNA. Studies indicate that the primers utilized are specific for the DNA of C. parvum. DNA sequences were also detected in stool specimens from 4 of 28 patients previously reported negative by AF. In summary, a rapid, sensitive, and specific assay for the detection of C. parvum directly from stool specimens has been developed. This test has the potential for detecting asymptomatic infection, monitoring the response to therapy, and detecting the organism in environmental sources.

Comparison of arbitrarily primed PCR with restriction endonuclease and immunoblot analyses for typing Clostridium difficile isolates

Arbitrarily primed PCR (AP-PCR) was used to genotype 26 clinical isolates of Clostridium difficile previously analyzed by immunoblotting (IB) and 20 isolates typed by restriction endonuclease analysis (REA) with HindIII. Two levels of differentiation were achieved with the AP-PCR approach by use of two different arbitrary primers. With the 19-mer arbitrary primer T-7 (first level of differentiation), a good correlation was found between IB and AP-PCR typing. Twenty isolates grouped into six IB types were separated into seven major AP-PCR types. These seven AP-PCR groups were further discriminated into 12 subtypes after genotyping with the arbitrary primer PG-05 (second level of differentiation). The remaining six isolates, all of different IB types, showed a unique and distinct DNA banding pattern with both of the arbitrary primers, T-7 and PG-05. Twenty isolates representing 20 REA types from 15 REA groups were resolved into 13 AP-PCR DNA profiles with the arbitrary primer T-7. A good correlation was found at this level of differentiation between the major REA groups, Y and M, and AP-PCR typing. While AP-PCR with this primer failed to differentiate isolates in REA groups J, G, R, and B, AP-PCR with PG-05 resolved these four isolates into four distinct AP-PCR types. In addition, one of three M strains and one of four Y strains displayed a slightly different DNA banding pattern by AP-PCR (with PG-05) from that of the other strains in the group. We conclude that AP-PCR is a rapid and sensitive method which not only complements other typing schemes but also may be a substitute and prove to be especially suited for immediate epidemiological tracking of nosocomial infections due to C. difficile.

[Seasonal variation in the ultrastructure and calcium uptake rate of cardiac sarcoplasmic reticulum in ground sqirrel]

The ultrastructure and calcium uptake rate of the cardiac sarcoplasmic reticulum (SR) was quantatively compared between the ground squirrels (Citellus dauricus) in hibernating and non-hibernating season. (1) In our ultrastructural investigation, OsFeCN post-fixation method was used to enhance the staining of SR, which made the SR structure more recognizable. (2) The results of morphometrical analysis demonstrated that the volume density of SR and lipid droplet in the cardio-myocyte was significantly higher (P < 0.01) in the hibernating animal than in the summer active one, and the subcompartment of SR with this difference was non-junctional SR. (3) The cardiac SR from hibernating ground squirrels had a higher (P < 0.01) calcium uptake rate as measured by the absorbence of arsenazo-III Ca2+ indicator, than that from autumn active ones. Altogether, our results suggested that the function of SR in the uptake of cytosolic calcium was enhanced in hibernating season, which may play an important role in the cold tolerance of myocardium of a hibernator.

Apparent outbreaks of Clostridium difficile-associated diarrhea in horses in a veterinary medical teaching hospital

Intestinal colonization with toxigenic strains of Clostridium difficile was documented in 9 of 10 horses with acute onset diarrhea in a veterinary medical teaching hospital, whereas a similar isolate was detected in only 1 of 23 other horses without diarrhea in the hospital. One horse with diarrhea was infected simultaneously with both C. difficile and Salmonella krefeld. Clostridium difficile was detected by fecal culture on selective medium, confirmed with a latex particle agglutination test, and identified as toxigenic by polymerase chain reaction amplification of toxin A and toxin B gene sequences. Using an arbitrarily-primed polymerase chain reaction, 6 distinct C. difficile isolates were detected in the feces of the 9 affected horses at the time of the outbreak of diarrhea.

Genomic fingerprinting of epidemic and endemic strains of Stenotrophomonas maltophilia (formerly Xanthomonas maltophilia) by arbitrarily primed PCR

Arbitrarily primed PCR (AP-PCR) was used to type 64 clinical isolates of Stenotrophomonas maltophilia from 60 patients and the hands of one nurse. Forty-seven different patterns were observed, most patients having isolates with unique genomic fingerprints. A single pattern, however, was obtained from six of eight patients involved in an intensive care nursery outbreak, confirming the suspected nosocomial transmission of this microorganism. This strain was also found in four other patients hospitalized at the same time but in different units. AP-PCR typing results had a good correlation with the 49 patterns obtained when the isolates were typed by contour-clamped homogeneous electric field gel electrophoresis. Although AP-PCR is slightly less discriminatory than contour-clamped homogeneous electric field gel electrophoresis, it offers several advantages and should be considered as a practical option for molecular typing during investigations of outbreaks.

Specific detection of Clostridium difficile toxin A gene sequences in clinical isolates

The polymerase chain reaction (PCR) was used to specifically detect toxin A gene sequences of Clostridium difficile in DNA isolated from human faeces. A set of oligonucleotide primers derived from the non-repetitive region of the toxin A gene was developed to amplify a 634-bp DNA fragment. All 28 cytotoxic strains of C. difficile, previously characterized by a toxin B-PCR assay, were positive for the presence of toxin A gene sequences. No amplification products were obtained from DNAs extracted from non-toxigenic strains, strains of C. sordellii, or C. bifermentans. In addition, amplification of DNA extracted from C. difficile 8864, a strain which does not produce toxin A, resulted in multiple bands which probed negative for toxin A gene sequences. DNAs extracted from nine stool specimens which were positive for toxin B by the cytotoxicity assay and by the toxin B-PCR assay were also positive in this assay. Toxin A gene sequences were detected in DNAs obtained from 4/11 stool specimens which were negative by the toxin B cytotoxicity assay. These four specimens were from patients who had a history of relapses due to C. difficile-associated colitis, and whose stools had previously been found to be positive by the toxin B-PCR test despite no detectable toxin B in the specimens. These data indicate a comparable degree of clinical sensitivity between these two toxin-gene PCR-based assays. This rapid, sensitive and specific assay may be useful not only in the diagnosis of C. difficile infections, but also in molecular studies of the toxin A gene in C. difficile strains.

Fecal shedding of Clostridium difficile in dogs: a period prevalence survey in a veterinary medical teaching hospital

The goal of this study was to determine the fecal prevalence of Clostridium difficile in dogs who were patients at a veterinary medical teaching hospital. Stool specimens collected from 152 dogs (in- and outpatients) were analyzed for the presence of C. difficile. An additional 42 stool specimens were collected and examined from dogs recently housed at local animal shelters. Following culture on selective medium, C. difficile was identified by a latex agglutination test, and the presence of the toxin A and B genes was determined individually by polymerase chain reaction. Clostridium difficile was isolated from the feces of 28 of the veterinary hospital patients (18.4%); isolates from 14 of these patients (50.0%) were toxigenic. Diarrhea was a clinical finding in 5 (35.7%) of the dogs carrying toxigenic isolates of C. difficile, whereas diarrhea was noted in only 2 of 14 dogs (14.3%) shedding nontoxigenic isolates. Three of 14 dogs (21.4%) shedding toxigenic isolates of C. difficile were receiving antibiotics at the time of stool collection, whereas 5 of 14 dogs (37.5%) shedding nontoxigenic strains of C. difficile were receiving antibiotics. The carriage rate of C. difficile was significantly higher for animals categorized as inpatients of the veterinary hospital. The carriage rate also provided evidence for an increased risk for fecal shedding with increasing age. Clostridium difficile was not isolated from any of the 42 dogs recently housed at local animal shelters. This study confirms the presence of toxigenic C. difficile in dogs at a veterinary teaching hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Genotyping of Clostridium difficile isolates

Arbitrarily primed polymerase chain reaction (AP-PCR) was used to genotype Clostridium difficile isolates from various sources. Four major molecular types were identified among strains from the American Type Culture Collection previously typed by serogroup and from isolates from patients at the University of California, Davis Medical Center, from a patient at a Utah institution, and from the environment. These groups contained subgroups that displayed, in addition to the common group bands, at least one unique band. Two strains isolated from patients at our institution had the same DNA banding patterns. These patients were hospitalized during the same period, raising the possibility of cross-infection through hospital contact or another common source. These results suggest that this AP-PCR approach will be useful in epidemiologic studies of C. difficile infections.

Diagnosis and monitoring of Clostridium difficile infections with the polymerase chain reaction

Toxigenic Clostridium difficile is the etiologic agent of pseudomembranous colitis. We have developed an assay system for the rapid direct detection of toxigenic C. difficile in human stool samples. After DNA extraction, polymerase chain reaction (PCR) amplification is undertaken with primers targeting specific sequences in the C. difficile 16S rRNA gene. Next, toxigenic strains of C. difficile are distinguished from nontoxigenic strains by PCR amplification of toxin A and/or B gene sequences. This study included 12 patients with C. difficile colitis, seven of whom had clinical relapses after discontinuation of vancomycin therapy. We detected toxigenic C. difficile in stools from four (57%) of these seven patients before relapse--at a time when no toxin B was detectable in stools and results of anaerobic culture were negative. The PCR assay is 100-fold more sensitive than anaerobic culture methods. The course of the infection in one patient (both during and after therapy) was monitored by the PCR technique. The multigene analysis approach permitted the detection of colonization with a nontoxigenic strain when this patient's relapses had cleared. This clinically applicable assay allows earlier detection of infection with toxigenic C. difficile. The result is more timely therapeutic intervention.