Natural evolution of skin test sensitivity in patients allergic to beta-lactam antibiotics

BACKGROUND

Subjects with immediate reactions to penicillins and positive skin test responses may lose sensitivity if penicillin is avoided. The longer the interval between the reaction and the skin test, the greater the likelihood of having a negative result.

OBJECTIVE

We sought to study prospectively the evolution of skin test sensitivity in a group of subjects allergic to penicillin with positive skin test responses to different penicillin determinants.

METHODS

Skin tests were performed with major and minor determinants of benzylpenicillin (BPO/MDM), amoxicillin (AX), and ampicillin at the initial evaluation and repeated 1, 3, and 5 years later if the responses were still positive. Subjects were divided into 2 groups. Group A consisted of patients with a positive skin test response to benzylpenicilloyl or minor determinant mixture, and group B consisted of those with a selective response to amoxicillin and good tolerance to benzylpenicillin.

RESULTS

In group A (n = 31) after 1 year, 25 patients continued to have positive responses and 6 began to have negative responses; after 3 years, 18 continued to have positive responses, 5 began to have negative responses, and 2 were lost to follow-up; and after 5 years, 12 continued to have positive responses, 5 began to have negative responses, and 1 was lost to follow-up. In group B (n = 24) 12 had positive responses, and 12 had negative responses after 1 year; 6 had positive responses, 5 had negative responses, and 1 was lost to follow-up after 3 years; and no patients had positive responses, 5 had negative responses, and 1 was lost to follow-up after 5 years. Survival analysis showed significant differences between groups (log-rank test = 12.8; P <. 0003).

CONCLUSION

Patients with a selective response to amoxicillin tended to lose sensitivity faster than those who responded to several penicillin determinants, supporting the existence of at least 2 distinct types of IgE response in patients allergic to beta-lactam.

Association of HLA-DR11 with the anaphylactoid reaction caused by nonsteroidal anti-inflammatory drugs

BACKGROUND

Several HLA alleles have been associated with asthma induced by nonsteroidal anti-inflammatory drugs (NSAIDs). The existence of HLA markers linked to other NSAID-induced reactions, such as cutaneous and anaphylactoid reactions, has not been established.

OBJECTIVE

The purpose of our work was to study the HLA-DRB1 and HLA-DQB1 alleles in patients with cutaneous and anaphylactoid reactions caused by NSAIDs.

METHODS

We have analyzed 114 HLA DRB1 and 26 HLA-DQB1 alleles in 21 patients with anaphylactoid reactions caused by NSAIDs, 47 patients who had exclusively cutaneous reactions during single-blind, placebo-controlled oral challenges with NSAIDs, and 167 tolerant control subjects (29 of whom had also had an IgE-mediated anaphylaxis to different agents). HLA-DRB1 and HLA-DQB1 alleles were typed by the polymerase chain reaction sequence-specific primers method with genomic DNA.

RESULTS

The frequency of HLA-DR11 alleles was 58.8% in the anaphylactoid reaction group, compared with 15.9% in the NSAID-tolerant healthy control subjects (OR, 7:3; 95% confidence interval, 2.8-19.0; P <.02) and 6.3% in the group of the patients with a tolerance for NSAIDs and with IgE-mediated anaphylaxis (OR, 18.75; 95% confidence interval, 4.3-81.1; P <.004). No differences were observed among HLA-DR11 alleles analyzed. There were no significant HLA-DQB1 associations with NSAID-induced anaphylactoid reactions. Patients with cutaneous reactions had HLA frequencies that did not differ significantly from the tolerant control subjects.

CONCLUSION

The HLA-DRB1*11 alleles showed a positive association with NSAID-induced anaphylactoid reactions.

[Characterization of the rpoB gene mutations in clinical isolates of rifampicin-resistant Mycobacterium tuberculosis]

OBJECTIVES

Characterization and frequency of the rpoB gene mutations associated with rifampin resistance in Mycobacterium tuberculosis clinical isolates in Sevilla.

METHODS

Characterization of rpoB mutations in 21 rifampicin-resistant strains of M. tuberculosis isolated during a three-year period (1994-1996) by three different molecular methods: a nonradioactive Single-strand conformation polymorphism (SSCP) analysis, DNA sequence analysis and a commercial method the line probe assay InnoLiPA.

RESULTS

Five distinct rpoB mutations were identified. Ser531-->Leu mutation was detected in 14 strains (66.7%), H526-->Asp in 3 strains (14.3%), Ans512-->Ser in 1 strain (4.8%), Glu513-->Leu in 1 strain (4.8%). A nine nucleotide deletion (codon 510-513) was found in one strain (4.8%) while in the remaining resistant strain (4.8%) no mutation was detected.

CONCLUSIONS

The frequency of the different mutations found in the rpoB gene, associated with rifampicin resistance in Mycobacterium tuberculosis clinical isolates in Seville, are similar to those previously reported. However, two new mutations has been detected: a nine nucleotide deletion (codon 510-513), and the Asn512-->Ser point mutation. The characterization of the mutations in the rpoB gene could serve as epidemiological marker for the rifampicin resistant clinical isolates of M. tuberculosis.

Circulating CLA+ lymphocytes from children with atopic dermatitis contain an increased percentage of cells bearing staphylococcal-related T-cell receptor variable segments

BACKGROUND

Atopic dermatitis is an allergic T-cell mediated skin inflammation. Staphylococcus aureus colonization is very common in cutaneous atopic dermatitis lesions. The cutaneous lymphocyte-associated antigen (CLA) is a T cell skin homing receptor that defines T lymphocytes associated with the cutaneous immune response.

OBJECTIVE

To study whether CLA+ T cells from atopic dermatitis children present a selective expression for Staphylococcus aureus-related TCR Vbeta segments.

METHODS

Peripheral blood T cells were stained with HECA-452 (anti-CLA) and a panel of TCR Vbeta specific monoclonal antibodies and analysed by flow cytometry.

RESULTS

Atopic dermatitis patients have a higher percentage of circulating CLA+ CD3+ lymphocytes compared with healthy controls. Patients with active atopic dermatitis during the study expressed a higher percentage of cells positive for the TCR Vbeta2 and Vbeta5.1 segments in the CLA+ but not in the CLA- subset. These TCR Vbetas are recognized by staphylococcal superantigens. Moreover, there was an increased percentage of HLA-DR+ expression by CLA+ Vbeta5.1+ T cells in patients with active atopic dermatitis, but those patients whose eczema was inactive had very similar values to healthy controls regarding TCR Vbeta and HLA-DR phenotype in circulating CLA+ T lymphocytes.

CONCLUSION

Our data indicate that circulating skin-homing T cells of patients with active atopic dermatitis contain an increased percentage of cells bearing TCR Vbeta segments related with Staphylococcus aureus. Staphylococcus superantigens may therefore trigger expansion or at least circulation of appropriate CLA+ T cells.

New aspects in betalactam recognition

The data presented in this review confirm that penicillin continues to be the most well defined model for studying drug allergy. The identification of new specificities has improved the understanding of allergy to penicillins, and different well defined subgroups now exist. The capacity of humans to respond to unique penicillin determinants has shown that although penicillin is a very small molecule it can be recognized in different ways by different IgE antibodies. These well defined models have left open the possibility that other betalactams can also induce specific reactions which implies that for diagnostic purposes, in addition to classical determinants, others are required for in vitro and/or in vivo evaluation. When the different subgroups now recognized are compared, not only are there differences in the manner of hapten recognition but also in the evolution of the natural sensitivity and in the capacity for recognizing other structures. The recognition of betalactams by T cells is also important and a number of studies have shown that subjects respond specifically to some aminopenicillins or cephalosporins with good tolerance to benzylpenicillin. The confirmation that these responses can be a T-cell-mediated reaction have been reported not only in vitro by the generation of T cell lines and T cell clones but also in vivo doing skin biopsies in subjects who have developed different types of delayed cutaneous reactions [44]. More studies are needed to determine the structure of T cell epitopes and this will help for a better understanding of both the IgE and IgG-mediated reactions.

Allergic reactions to ampicillin. Studies on the specificity and selectivity in subjects with immediate reactions

BACKGROUND

Ampicillin (AMP) is a drug that has been prescribed extensively. Reactions that have been reported include exanthema, desquamative contact eczema, urticaria and anaphylaxis. Experimental evidence indicates that the side chain of AMP is a structure that may induce a selective immune response either at the humoral or lymphocyte T-cell level. With regard to IgE reactions, the selectivity and specificity of the response needs to be studied in humans.

OBJECTIVES

To study the specificity of the IgE response in a group of subjects who had an immediate allergic reaction after the administration of AMP.

METHODS

Subjects developing an immediate response (anaphylaxis or urticaria) after the administration of AMP or an aminopenicillin derivative with the same side chain as AMP were studied. Skin tests were made to determinants generated from benzyl penicillin (BP): benzyl penicilloyl (BPO) and minor determinant mixture (MDM), as well as amoxicillin (AX) and AMP. Specific IgE antibodies were determined to benzyl penicilloyl polylisine (BPO-PLL), amoxicilloyl-polylisine (AX-PLL) and ampicilloyl-polylisine (AMP-PLL). The specificity of the IgE antibody response was studied by RAST and RAST inhibition. Subjects were classified in three categories: group A: those who were skin test and/or RAST positive to determinants derived from benzylpenicillin, group B: those who were negative to determinants derived from benzylpenicillin but were skin test and/or RAST positive to determinants derived from AX and AMP and group C: those who were exclusively positive to determinants derived from AMP.

RESULTS

A total of 48 subjects was included in the study. In group A there were 35 cases, in group B 10 cases, and in group C three cases. RAST inhibition studies showed that in some instances the side chain of AMP could induce specific responses with a variable degree of crossreactivity between BP and AX.

CONCLUSIONS

Although AMP can induce an immediate IgE response in subjects allergic to betalactams and the structure of the side chain may contribute to the specificity of the response, our results indicate that in most instances crossreactivity with the other penicillins exists and that in the groups studied selective reactions to just AMP derived determinants were uncommon.

Successful administration of cytarabine after a previous anaphylactic reaction

Cytarabine (Cyt) is an antimetabolite used primarily in the treatment of leukemia, and both immediate and delayed hypersensitivity reactions have been reported. We studied a 9-year-old girl with lymphoblastic leukemia, who developed three anaphylactoid reactions during Cyt treatment courses over a 1-year period. Three years later, Cyt was required again. Although a skin test was negative to Cyt at the concentration of 4 micrograms/ml, we decided on placebo-controlled administration of the drug. The Cyt was well tolerated, and urine values of N-methylhistamine showed no important variations throughout this period compared to those during the placebo administration. Skin tests carried out 14 days after the study were positive at the concentration of 4 micrograms/ml. The history of different episodes of allergic reactions to Cyt, the last one being the most severe, indicated the possible participation of an immediate hypersensitivity phenomenon, but because no studies had been carried out initially, we could not establish the presence of IgE antibodies. These results indicate that good tolerance existed after the control administration procedure. The long interval, 3 years, between the allergic episode and our protocol and the appearance of a positive skin test 14 days after the protocol indicated that the subject had lost sensitivity and become resensitized after the controlled administration procedure.

IgG and IgE antibodies in subjects allergic to penicillins recognize different parts of the penicillin molecule

BACKGROUND

IgE and IgG antibodies to penicillins can have different specificities. However, this response, including the recognition of the different parts of penicillin, has never been studied in the same subject.

OBJECTIVE

Study of the specificity of IgE and IgG antibodies and the relevant parts of the penicillin molecule that contribute to the hapten binding site in sera from human.

METHODS

Specific IgE antibodies were determined by RAST and specific IgG antibodies by ELISA. The recognition of the different molecules was studied by inhibition studies.

RESULTS

Seven sera with IgG and IgE antibodies to amoxicillin and benzyl penicillin were analyzed. IgE antibodies recognized mainly two different epitopes: in one, the side chain was a relevant part of the epitope, in the other, it was the nuclear portion. IgG antibodies recognized the nuclear portion in all instances. In the same subject, antibodies of different isotype and specificity were found.

CONCLUSIONS

Subjects who develop simultaneously IgE and IgG antibodies to penicillins show different specificities. This proves that different populations of antibodies recognize different epitopes.

[Subspecific classification of 11 clinical strains of Klebsiella pneumoniae based on their biochemical, antibiotic and plasmid profiles]

The paper summarizes at a subspecific level 11 clinical strains of K. pneumoniae. The objective of the work was to determine in a simple and effective way differences between different strains of the mentioned taxon. Biochemical characteristics, antibiogram and part of the plasmid spectrum were used for assessment of inter-species differences between different strains and at the same time their use as simple markers of epidemiological analyses is presented.

Loss of an HLA haplotype in pancreas cancer tissue and its corresponding tumor derived cell line

A combination of immunohistochemical, biochemical, and recombinant DNA techniques were used to investigate class I expression in 26 pancreatic adenocarcinomas and 6 autologous tumor-derived cells. The prevalence of HLA losses was found to be comparable to that observed in other tumor types (> 35%), using monomorphic and locus-specific antibodies. In one patient, the original tumor tissue, a tumor derived cell line (IMIM-PC-2), and EBV-transformed lymphocytes were available for study. The patient's phenotype was A25, A30, B18, B18. However, A30 allele product could not be detected in the original tumor not in the cultured tumor cells. In addition, A30 allele could not be isolated from cDNA or genomic clones from the cultured tumor cells whereas it was isolated from the autologous lymphoblastoid cell line. Using isoelectric focusing analysis a significant reduction in the B18 heavy chain product was also observed in the tumor cell line, IMIM-PC-2, suggesting the absence of expression of one allele. Further studies revealed loss of heterozygosity at DR and other loci of chromosome 6 and cytogenetic data strongly suggested deletion of a full chromosome 6. This work indicates for the first time that loss of a full HLA haplotype occurs in tumor tissue and suggests that this mechanism may contribute to the progression of human cancer.

Selective allergic reaction to oral cloxacillin

BACKGROUND

Previous observations indicate that in some instances subjects allergic to penicillins may experience an allergic reaction after taking the drug by one route but have good tolerance after being administered the same drug by a different route.

OBJECTIVE

The purpose was to establish if cloxacillin (CLX) induced a selective response only after oral route administration in a suspected case and to study if there were differences between the oral and parenteral formulations.

METHODS

Skin tests were carried out using benzylpenicillin (BP) conjugated to poly-L-lysine (BPO-PLL), minor determinant mixture of benzylpenicillin (MDM), ampicillin (AMP), amoxicillin (AX) and cloxacillin (CLX). Radioallergosorbent assay (RAST) was carried out using BPO-PLL, AX-PLL and CLX-PLL sensitized discs. In the case the skin tests and RAST were negative, a controlled challenge administering the drug by both oral and parenteral route was made. Urine samples were taken at prechallenge (basal levels) and at three periods after challenge (1-3, 3-6 and 6-9 h). Analysis of oral and parenteral formulations was made by HPLC chromatography.

RESULTS

All skin tests and RASTs were negative. With the challenge tests the patient tolerated parenteral BP and oral phenoxymethyl penicillin (PV) and oral and parenteral AMP up to therapeutic concentrations. Parenteral CLX (500 mg) was also tolerated but 30 min after administering 50 mg by the oral route progressive generalized erythema with pruritus, facial angioedema and tachycardia developed. Urine samples taken during the challenge tests showed an increased excretion of N-methyl histamine (N-MH) 3 h after challenge with oral CLX but no change in N-MH levels after challenge with parenteral CLX or the other penicillins, indicating that histamine was released during the allergic episode with oral CLX. HPLC analysis of the oral and parenteral CLX formulations indicated that there were no differences and that neither polymers no other contaminant materials were present.

CONCLUSION

Although the nature of the allergenic determinant involved in the induction of the reaction is not yet known, the oral route may have favoured the production of a metabolite not generated by the parenteral route.

Nonimmediate reactions to betalactams: prevalence and role of the different penicillins

In patients treated with penicillins, adverse cutaneous reactions can occur within minutes or may take several days to develop. IgE antibody-mediated reactions are well documented, but other mechanisms may also be involved. In particular, nonimmediate reactions have not been studied extensively, and the purpose of the present work was to establish the incidence of such reactions among a large group of patients and to study the penicillins involved. A total of 380 subjects with a history of a cutaneous reaction following administration of a penicillin antibiotic was included in the study. Skin tests and specific IgE measurements (RAST) were carried out using various penicillins and penicillin-related reagents, and patients were also challenged with various penicillins. In some patients with delayed skin test responses, skin biopsies were carried out. The tests confirmed that 74 subjects (19.4% of total investigated) had suffered a cutaneous reaction to a penicillin derivative, and 29 of these subjects (7.6% of total or 39% of confirmed) showed evidence of having suffered a nonimmediate reaction. The latter group were identified by giving a positive delayed direct challenge, and in 65% of the cases a delayed skin test response was detected. In most cases, these responses were to amino penicillins. Skin biopsies showed a lymphomonocytic cell infiltrate. Nonimmediate reactions to penicillins are a reproducible phenomenon, suggesting that a specific mechanism is responsible. By direct challenge, 93% of responders were positive to amino penicillins (10.3% ampicillin, 82.7% amoxicillin), indicating a major role for these penicillins in nonimmediate reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative study between European and American species of Polistes using sera from European sensitized subjects

Although the different vespid species of the genus Polistes are found all over the world, studies about allergy sensitization to these species have been made mainly in North America. We studied the specific IgE in a large group of sera from patients sensitized to Polistes dominulus (PD) and determined the crossreactivity with another important European Polistes (P. gallicus [PG]) and with five American relevant species of this genus: P. exclamans (PE), P. fuscatus (PF), P. metricus (PM), P. annularis (PAN) and P. apachus (PAP). Studies indicated that 96.7% of sera with IgE positive to PD were positive to PG. No case positive to just PG was found. The comparison of these two European species with the American relatives indicated that most cases were positive to all the insects although there were significant differences in the radioallergosorbent test (RAST) value. These results were confirmed by RAST inhibition studies, and indicate that although the European and American species are closely related, species specific allergenic differences exist. These data suggest that in vivo studies should be carried out in order to determine the sensitivity and specificity of the European venoms compared with the American species.

Comparison of Vespula germanica venoms obtained from different sources

This study was carried out to compare the allergenic potency of Vespula germanica (VG) venoms extracted by different methods and commercially available venoms from Vespula species currently used for in vivo and in vitro studies including immunotherapy. Pure VG venom was used as the reference material. Protein content and enzymatic and allergenic properties of all venoms studied were determined by dye stain reagent, hyaluronidase and phospholipase A1B enzyme activities, and radioallergosorbent test inhibition studies, respectively. Radioallergosorbent test discs sensitized with commercial and pure VG venom were compared using specific IgE antibodies from subjects allergic to VG venom. The data obtained indicate that there were important differences in the allergenic potency between the Vespula species venoms employed for in vivo and/or in vitro assays, VG venom obtained by sac dissection, and pure VG venom. These results indicate that venoms from Vespula species used for in vitro and in vivo tests have a lower concentration of allergens and contain nonvenom proteins. These data should be taken into account when these vespid venoms are used for diagnostic purposes and also when evaluating immunotherapy studies.

[Evaluation of intestinal pathogenicity of Yersinia spp. strains isolated from human feces]

BACKGROUND

Yersinia enterocolitica is a human pathogen which an acts on the intestine by basically enteroinvasive mechanism. Its virulence has been related with the presence of a plasmid of 40-50 MD which codes a series of properties. There are strains of Y. enterocolitica and of other species assimilated to the Y. enterocolitica group which lack the virulence plasmid. In these cases there is a problem in evaluating the pathogenic ability on the intestine of these bacterias when isolated in faeces.

METHODS

A study of 30 Yersinia spp. strains including growth in a magnesium oxalate medium, Reg-Congo and agar (CR-MOX), sculine hydrolisis (Sc), pyrazinamidase activity (Pyz) and salicine fermentation (Sal) was performed. In addition, the presence of virulence plasmid (VP) was determined.

RESULTS

Twenty-two strains identified as Y. enterocolitica presented the virulence pattern (CR-MOX+, Pyz-, Sal/Sc-) and 21 were VP+. Seven strains isolated were CR-MOX-, Pyz+, Sal/Sc+ and VP- being typed as Y. fredericksenii (6) and Y. kristensenii (1). The remaining strain was CR-MOX- and VP- but Pyz, Sal/Sc were also negative, being identified as Y. enterocolitica.

CONCLUSIONS

By the tests referred the authors were able to identify and evaluate the pathogenicity of Yersinia spp. isolated in faeces. These techniques may be used in the microbiology laboratory as a method which aids to evaluate the diagnosis of intestinal infections caused by Yersinia spp.

Dual genitotropic human papillomavirus infections in genital warts

BACKGROUND AND METHODS

We have carried out a prospective study of dual genitotropic human papillomavirus (HPV) infections by means of two different DNA detection methods in biopsy specimens obtained from patients who were examined for genital warts at the STD clinic of the School of Medicine in Seville, between January 1990 and December 1991.

RESULTS

100 patients with a clinical diagnosis of condilomata acuminata were seen during the study period. DNA of the genitotropic HPV 6/11, 16/18 and 31/33/35 was detected by an in situ hybridisation method in 75 (77%) of the 98 evaluable samples; one of the genotypes tested in 59 (61%) samples, and two or more genotypes tested in the remaining 16 (15%) samples. In 21 (98%) of the 23 negative samples by in situ hybridisation, we were able to detect DNA of genital HPV using a polymerase chain reaction amplification method (PCR). Among the 34 samples where PCR was applied we confirmed the presence of two different HPV genotypes in eight samples.

CONCLUSIONS

The frequency of dual infections with human genitotropic papillomavirus in genital warts was 8%, although we believe that this rate should be higher as we have not used the PCR method in all of the samples.

Evaluation of a fluorescent DNA hybridization assay for the detection of Neisseria gonorrhoeae

This study evaluates a four-hour fluorescent DNA hybridization assay using both known bacterial isolates and clinical specimens. A biotinylated oligonucleotide probe from a sequence of the plasmid-encoded gene cppB was used. Hybrids were detected by addition of a streptavidin-alkaline phosphatase conjugate, followed by incubation for 30 min in a fluorescent substrate for alkaline phosphatase. The level of detection of the fluorescent assay was 0.1 pg of cryptic plasmid DNA or 200 cfu of the plasmid-containing strain NG 34/85 of Neisseria gonorrhoeae. A total of 119 reference strains of Neisseria gonorrhoeae and other related bacteria were tested for reactivity with the probe. All Neisseria gonorrhoeae strains, including eight plasmid-free strains, hybridized with the probe. Fluorescence ratios were 2.67 for plasmid-free strains and 3.85 for plasmid-containing strains. Of the heterologous microorganisms tested, only one of six strains of Neisseria cinerea gave a fluorescence ratio above the 2.0 cut-off value for positivity with the probe at a cell density of 1 x 10(4) cfu. The probe was also evaluated using clinical specimens from 100 patients attending a clinic for sexually transmitted diseases. The sensitivity of the assay was 100% while the specificity was 97.5%. Positive and negative predictive values were 91.2% and 100%, respectively. The fluorescent DNA hybridization assay for the detection of Neisseria gonorrhoeae described here thus appears to be a highly specific and sensitive assay.

[Use of PCR in the epidemiological identification of Campylobacter spp]

BACKGROUND

With arbitrary primer PCR technique it is possible to obtain amplification lane patterns easily and with good reproducibility from the genomic DNA of bacteria studied. There is also no need for prior information regarding the DNA sequence.

METHOD

This method implies two cycles of amplification with low stringency, followed by a PCR of high stringency.

RESULTS

Using the above mentioned technique, we were able to show that Campylobacter spp from clinical samples could be separated as well as different strains from the same species.

CONCLUSIONS

According to our results as well as the ones from different authors applied to other microorganisms, we can assume that the method could be used in any bacterial species for epidemiologic studies purposes.

Detection of salmonellas by DNA hybridization with a fluorescent alkaline phosphatase substrate

This study evaluates a DNA hybridization assay for salmonella with AttoPhos (JBL Scientific, San Luis Obispo, CA), a fluorescent substrate for alkaline phosphatase. The probe used (50 ng/ml) was a biotinylated 600 bp fragment consisting of a tandem repeat of an insertion sequence (IS200) found in most Salmonella spp. evaluated. The hybridization was carried out at 65 degrees C for 2 h without prior prehybridization and hybrids were detected by the addition of a streptavidin-alkaline phosphatase conjugate. Circles (5 mm) were cut from the membrane and placed in a cuvette containing 1 ml of 1 mmol/l AttoPhos. The reaction was evaluated after 30 min at 37 degrees C with a fluorometer with an excitation wavelength of 440 nm and an emission wavelength of 550 nm. The sensitivity of the probe was estimated to be 10,000 copies of target DNA or 5 x 10(-20) mol of DNA. All 74 salmonella strains tested reacted with the probe but none of the 98 heterologous species tested gave positive results. The results of this study indicate that our assay method, which employs a biotinylated tandem repeat of IS200 and AttoPhos, is a specific and highly sensitive quantitative method for the detection of salmonellas.

[Chlamydia trachomatis detection by DNA-RNA hybridization]

BACKGROUND

A one-chain DNA probe, that complements ribosomal RNA of Chlamydia trachomatis was used as a detection method for this microorganism on clinical samples. We compare the method with the cell culture one.

METHODS

A total of 175 samples (cervix swabs) from women seen at the STD center of the Facultad de Medicina de Sevilla were examined by both diagnostic techniques. When the results were different, a third method (ELISA) was also used.

RESULTS

Using serial dilutions of a C. trachomatis cell culture as reference pattern, we determine the minimum number of inclusion forming units needed in order to be detected by the probe was 1000. Of all 175 samples, in 24 (14%) cell culture was positive for C. trachomatis, and 26 were positive using the DNA probe test. Sensitivity and specificity for this test were 93% and 95%, respectively.

CONCLUSIONS

We believe that the DNA probe test was similar to the cell culture test as screening test in Chlamydia trachomatis infections diagnosis, specially among high risk populations.

DNA hybridization assay using ATTOPHOS, a fluorescent substrate for alkaline phosphatase

A fluorometric procedure for the detection of DNA-DNA hybrids is described. The procedure involved the detection of probe-bound alkaline phosphatase with the fluorescent substrate ATTOPHOS. This substrate is converted to ATTOFLUOR by alkaline phosphatase and fluoresces strongly at 550 nm when excited with a wavelength of 440 nm. DNA hybridization assays were performed both with dilutions of purified target plasmid DNA (pSE9 or PBR322) and whole bacterial cells. Streptavidin-alkaline phosphatase conjugates were added to react with bound probe. Fluorometric assays, as well as colorimetric assays, using 5-bromo-4-chloro-3-indolylphosphate + nitroblue tetrazolium for alkaline phosphatase activity were performed. The fluorescence of the substrate was measured at time intervals, and the slope of the regression line calculated. A slope four times greater than that of background was considered positive. One hundred femtograms or 2.2 x 10(4) molecules of homologous DNA were detected with the fluorescent assay as compared with 10,000 femtograms or 2.2 x 10(6) molecules of homologous DNA with the colorimetric assay. Similar results were obtained with whole cells. Approximately 1 x 10(3) homologous cells were detected fluorometrically and 1 x 10(5) cells were detected colorimetrically. Based on these results, we conclude that, in our hands, the DNA hybridization assay described here using ATTOPHOS as the substrate for alkaline phosphatase is a very sensitive assay for the detection of DNA-DNA hybrids.

Evaluation of a DNA probe of plasmid origin for the detection of Neisseria gonorrhoeae in cultures and clinical specimens

This study evaluates a cryptic plasmid-derived DNA probe in a dot-blot hybridization assay of 4-h duration, using both known bacterial isolates and clinical specimens. The probe, consisting of a 237 bp segment of the plasmid-encoded gene cppB, sequences of which are also found in the chromosome, was labelled with digoxigenin-11-dUTP. The sensitivity of the probe was approximately 25 pg of DNA or 500 cfu of Neisseria gonorrhoeae. A total of 170 reference strains of Neisseria gonorrhoeae and other related bacteria were tested for reactivity with the probe. All N. gonorrhoeae strains, including three plasmid-free strains, hybridized with the probe. Among the heterologous bacterial cultures, only one strain of N. cinerea reacted with the probe when the cell concentration was 5 x 10(6) cfu. The probe was also evaluated in a clinical study. A total of 201 patients visiting the STD clinic at the University Hospital, University of Seville, participated in the study. The sensitivity of the assay was 95% while the specificity was 98%. Positive and negative predictive values were 97% and 98%, respectively. It appears that the plasmid-derived probe used in this study could serve as a useful tool in the rapid and specific detection of Neisseria gonorrhoeae in clinical specimens.

Cross-reactivity between penicillins and cephalosporins: clinical and immunologic studies

Nineteen well-characterized penicillin-allergic patients were investigated for their sensitivity to cephalosporins containing potentially cross-reactive side chains. All patients were administered cephamandole parenterally and, if this was tolerated, a course of oral cephaloridine was administered. Only two patients responded to the cephamandole; none of the remaining patients reacted to cephaloridine. Benzylpenicilloyl RAST-inhibition studies with sera from three subjects who had not reacted to the cephalosporins demonstrated that cephamandole linked to proteins was capable of recognizing benzylpenicilloyl-specific IgE antibody. It is concluded that consideration of side chain structures can help to predict possible cross-reactions between penicillins and cephalosporins, but carefully controlled challenge tests are advisable before penicillin-allergic patients are treated with cephalosporins. In relation to cross-reacting potential, in vitro experimental studies are difficult to interpret and may in some circumstances overestimate the risk.

Failure to thrive, wasting syndrome, and immunodeficiency in rabies: a hypophyseal/hypothalamic/thymic axis effect of rabies virus

Studies of rabies virus in several animal models consistently showed hypothalamic infection, hypophyseal infection, dramatic growth impairment (in the form of failure to thrive), wasting syndrome, and immune depletion. Rabies virus infection was studied through routine monoclonal antinucleocapsid antibody immunofluorescence and through a peroxidase-antiperoxidase immunoperoxidase method. The latter was modified to detect the in situ production of growth hormone by uninfected and rabies virus-infected adeno-a-pituicytes (with confirmation of the results both in vivo and in vitro). Infection with rabies virus made the specialized pituicytes produce less growth hormone. Growth before rabies virus infection and its reduction due to infection were investigated in a linear regression model. The fit was statistically significant (P less than .05) in all species studied: mouse, rat, rabbit, cow, and cat. Immune depression was studied in terms of alterations in the immunotopography of the thymus and also the specific T- and B-cell homing areas of the spleen (although spleen data are not presented here). On the basis of these results and a thorough review of wasting syndromes encountered in other diseases, a primary failure to thrive and an ensuing wasting syndrome were described and characterized for rabies, and their origin was assigned to a dysfunction of the hypophyseal/hypothalamic/thymic axis associated with at least (but not necessarily only) one of the centrally controlled growth hormones.