Studies of the outer membrane proteins of Branhamella catarrhalis

FimH-based display of functional eukaryotic proteins on bacteria surfaces

The demand for recombinant proteins for analytic and therapeutic purposes is increasing; however, most currently used bacterial production systems accumulate the recombinant proteins in the intracellular space, which requires denaturating procedures for harvesting and functional testing. We here present a novel FimH-based expression system that enables display of fully functional eukaryotic proteins while preventing technical difficulties in translocating, folding, stabilizing and isolating the displayed proteins. As examples, Gaussia Luciferase (GLuc), epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and epiregulin (EPRG) were expressed as FimH fusion proteins on the surface of E. coli bacteria. The fusion proteins were functionally active and could be released from the bacterial surface by specific proteolytic cleavage into the culture supernatant allowing harvesting of the produced proteins. EGFR ligands, produced as FimH fusion proteins and released by proteolytic cleavage, bound to the EGF receptor (EGFR) on cancer cells inducing EGFR phosphorylation. In another application of the technology, GLuc-FimH expressed on the surface of bacteria was used to track tumor-infiltrating bacteria by bioluminescence imaging upon application to mice, thereby visualizing the colonization of transplanted tumors. The examples indicate that the FimH-fusion protein technology can be used in various applications that require functionally active proteins to be displayed on bacterial surfaces or released into the culture supernatant.

Identification of a bacteriocin and its cognate immunity factor expressed by Moraxella catarrhalis

Background

Bacteriocins are antimicrobial proteins and peptides ribosomally synthesized by some bacteria which can effect both intraspecies and interspecies killing.

Results

Moraxella catarrhalis strain E22 containing plasmid pLQ510 was shown to inhibit the growth of M. catarrhalis strain O35E. Two genes (mcbA and mcbB) in pLQ510 encoded proteins predicted to be involved in the secretion of a bacteriocin. Immediately downstream from these two genes, a very short ORF (mcbC) encoded a protein which had some homology to double-glycine bacteriocins produced by other bacteria. A second very short ORF (mcbI) immediately downstream from mcbC encoded a protein which had no significant similarity to other proteins in the databases. Cloning and expression of the mcbI gene in M. catarrhalis O35E indicated that this gene encoded the cognate immunity factor. Reverse transcriptase-PCR was used to show that the mcbA, mcbB, mcbC, and mcbI ORFs were transcriptionally linked. This four-gene cluster was subsequently shown to be present in the chromosome of several M. catarrhalis strains including O12E. Inactivation of the mcbA, mcbB, or mcbC ORFs in M. catarrhalis O12E eliminated the ability of this strain to inhibit the growth of M. catarrhalis O35E. In co-culture experiments involving a M. catarrhalis strain containing the mcbABCI locus and one which lacked this locus, the former strain became the predominant member of the culture after overnight growth in broth.

Conclusion

This is the first description of a bacteriocin and its cognate immunity factor produced by M. catarrhalis. The killing activity of the McbC protein raises the possibility that it might serve to lyse other M. catarrhalis strains that lack the mcbABCI locus, thereby making their DNA available for lateral gene transfer.

HIV infection and the pancreas: risk factors and potential management guidelines

One thousand and eighty-one evaluable HIV-infected patients were assessed for pancreatic abnormalities in a prospective case-control study including the whole follow-up period of each patient (minimum 12 months). The 435 patients (40.2%), who experienced at least one episode of confirmed pancreatic laboratory abnormality had a longer duration of seropositivity, exposure to protease inhibitors, a more frequent immunodeficiency, AIDS, chronic liver and/or biliary disease and hypertriglyceridaemia, while no relation was found with antiretroviral administration, and the duration of type of nucleoside analogues, when compared with the 646 controls. High and prolonged laboratory alterations eventually associated with signs of organ involvement occurred in 166 cases (38.2%), and were related to the administration of didanosine, stavudine, lamivudine, pentamidine, cotrimoxazole or antitubercular/antimycobacterial therapy, cytotoxic chemotherapy, illicit substance or alcohol abuse, opportunistic infections, chronic liver and/or biliary disease, a protease inhibitor-based highly active antiretroviral therapy (HAART) and hypertriglyceridaemia (usually associated with HAART administration). No difference was noticed between the 46 patients with clinical and/or imaging evidence of pancreatic involvement and the 120 asymptomatic subjects. Although recurrences of enzyme alterations involved 69.6% of patients, only in 30.1% of cases did a change of the underlying antiretroviral or antimicrobial therapy become necessary. An acute, uncomplicated pancreatitis occurred in nine of the 46 symptomatic subjects (19.6%). A two to four week gabexate and/or octreotide administration (performed in 79 cases of 166, 47.6%), achieved a significant laboratory, clinical and imaging cure or improvement in 82.3% of cases, with a better success rate of combined (gabexate mesilate plus octreotide) vs. single (gabexate mesilate or ocreotide) therapy. Reduced disease recurrences and a better tolerability of antiretroviral regimens, were also noticed.

Identification and characterization of a novel outer membrane protein (OMP J) of Moraxella catarrhalis that exists in two major forms

Moraxella catarrhalis is a common commensal of the human respiratory tract that has been associated with a number of disease states, including acute otitis media in children and exacerbations of chronic obstructive pulmonary disease in adults. During studies to investigate the outer membrane proteins of this bacterium, two novel major proteins, of approximately 19 kDa and 16 kDa (named OMP J1 and OMP J2, respectively), were identified. Further analysis indicated that these two proteins possessed almost identical gene sequences, apart from two insertion/deletion events in predicted external loops present within the putative barrel-like structure of the proteins. The development of a PCR screening strategy found a 100% (96/96) incidence for the genes encoding the OMP J1 and OMP J2 proteins within a set of geographically diverse M. catarrhalis isolates, as well as a significant association of OMP J1/OMP J2 with both the genetic lineage and the complement resistance phenotype (Fisher's exact test; P < 0.01). Experiments using two DeltaompJ2 mutants (one complement resistant and the other complement sensitive) indicated that both were less easily cleared from the lungs of mice than were their isogenic wild-type counterparts, with a significant difference in bacterial clearance being observed for the complement-resistant isolate but not for its isogenic DeltaompJ2 mutant (unpaired Student's t test; P < 0.001 and P = 0.32). In this publication, we characterize a novel outer membrane protein of Moraxella catarrhalis which exists in two variant forms associated with particular genetic lineages, and both forms are suggested to contribute to bacterial clearance from the lungs.

Human antibody response to outer membrane protein G1a, a lipoprotein of Moraxella catarrhalis

Moraxella catarrhalis is an important cause of respiratory infections in adults with chronic obstructive pulmonary disease (COPD) and of otitis media in children. Outer membrane protein (OMP) G1a is an approximately 29-kDa surface lipoprotein and is a potential vaccine candidate. The gene that encodes OMP G1a was expressed and purified using a novel plasmid vector. [(3)H]palmitic acid labeling demonstrated that both native and recombinant OMP G1a contain covalently bound palmitic acid. To assess the expression of OMP G1a during human infection, paired sera and sputum supernatants from adults with COPD followed prospectively were studied by enzyme-linked immunosorbent assays with recombinant lipidated OMP G1a to detect antibodies made specifically during carriage of M. catarrhalis. Overall, 23% of patients developed either a serum immunoglobulin G (IgG) response (9%) or sputum IgA response (21%) to OMP G1a, following 100 episodes of acquisition and clearance of M. catarrhalis. Patients developed antibody responses at similar rates following episodes of clinical exacerbation compared to asymptomatic colonization. Serum IgG antibodies following natural infection were directed predominantly at OMP G1a epitopes that are not exposed on the bacterial surface. These data show that OMP G1a is expressed during infection of the human respiratory tract and is a target of systemic and mucosal antibodies. These observations indicate that OMP G1a, a highly conserved surface protein, should be evaluated further as a vaccine candidate.

Identification and characterization of outer membrane proteins G1a and G1b of Moraxella catarrhalis

Moraxella catarrhalis is an important cause of otitis media, sinusitis, and lower respiratory tract infections in patients with chronic obstructive pulmonary disease. The purified outer membrane of M. catarrhalis contains a 29 kDa band, previously named outer membrane protein G1 (OMP G1). Polyclonal antiserum to the OMP G1 band was used to screen a genomic lambda phage library and the gene for OMP G1a was cloned and sequenced. Analysis of outer membrane by isoelectric focusing and amino-terminal protein sequence of the 29 kDa band revealed that the band is actually two individual proteins designated OMP G1a and OMP G1b. OMP G1a is a lipoprotein with an isoelectric point of 4. OMP G1b contains an unblocked amino-terminus and has an isoelectric point of 9. Analysis of the sequence of OMP G1a and OMP G1b from 25 clinical isolates revealed a high degree of conservation among strains. The sequence conservation of OMP G1a and OMP G1b among strains, combined with previous observations that OMP G1a and OMP G1b contain epitopes on the bacterial surface, indicate that OMP G1a and OMP G1b are potential vaccine antigens for M. catarrhalis.

Analysis of Moraxella catarrhalis outer membrane antigens cross-reactive with Neisseria meningitidis and Neisseria lactamica

Mouse sera against outer membrane proteins from Moraxella catarrhalis, Neisseria meningitidis and Neisseria lactamica, and human sera from both healthy individuals and patients convalescing from meningococcal meningitis were used to identify cross-reactive antigens. Mouse anti-N. meningitidis and anti-N. lactamica sera recognized 77, 62 and 32 kDa outer membrane antigens in M. catarrhalis strains; on the contrary, the meningococcal porin PorB (38-42 kDa) was recognized by one of the two anti-M. catarrhalis sera. Human sera from both healthy individuals and patients convalescing from meningococcal meningitis also showed cross-reactive antibodies against these proteins. The existence of cross-reactive antigens in M. catarrhalis and N. meningitidis (as well as in N. lactamica) could favor the development of natural immunization against both pathogens.

Comparison of Moraxella catarrhalis isolates from children and adults for growth on modified New York City medium and potential virulence factors

Initial studies found that Moraxella catarrhalis isolates from adults that grew on modified New York City medium (MNYC(+)) that contained antibiotics selective for pathogenic neisseriae differed from strains that did not grow on this medium (MNYC(-)) in their potential virulence properties. It was predicted that higher usage of antibiotics to treat respiratory illness in children might result in higher proportions of MNYC(+) isolates if antibiotics were an important selective pressure for this phenotype. Two of 100 adult isolates (2 %) were MNYC(+), compared to 88 of 88 isolates (100 %) from children (P = 0.000). MNYC(+) strains were serum-resistant and bound in higher numbers to HEp-2 cells that were infected with respiratory syncytial virus (RSV). Endotoxin from an MNYC(+) isolate induced significantly higher pro-inflammatory response levels than endotoxin from an MNYC(-) strain. MNYC(-) adult isolates expressed haemagglutinins and bound in lower numbers to RSV-infected cells, but serum resistance was variable. All isolates from children were MNYC(+), serum-resistant and bound in greater numbers to RSV-infected cells. These results indicate that both RSV infection and antibiotic usage select for the MNYC(+) phenotype.

Moraxella catarrhalis: from emerging to established pathogen

Moraxella catarrhalis (formerly known as Branhamella catarrhalis) has emerged as a significant bacterial pathogen of humans over the past two decades. During this period, microbiological and molecular diagnostic techniques have been developed and improved for M. catarrhalis, allowing the adequate determination and taxonomic positioning of this pathogen. Over the same period, studies have revealed its involvement in respiratory (e.g., sinusitis, otitis media, bronchitis, and pneumonia) and ocular infections in children and in laryngitis, bronchitis, and pneumonia in adults. The development of (molecular) epidemiological tools has enabled the national and international distribution of M. catarrhalis strains to be established, and has allowed the monitoring of nosocomial infections and the dynamics of carriage. Indeed, such monitoring has revealed an increasing number of B-lactamase-positive M. catarrhalis isolates (now well above 90%), underscoring the pathogenic potential of this organism. Although a number of putative M. catarrhalis virulence factors have been identified and described in detail, their relationship to actual bacterial adhesion, invasion, complement resistance, etc. (and ultimately their role in infection and immunity), has been established in a only few cases. In the past 10 years, various animal models for the study of M. catarrhalis pathogenicity have been described, although not all of these models are equally suitable for the study of human infection. Techniques involving the molecular manipulation of M. catarrhalis genes and antigens are also advancing our knowledge of the host response to and pathogenesis of this bacterial species in humans, as well as providing insights into possible vaccine candidates. This review aims to outline our current knowledge of M. catarrhalis, an organism that has evolved from an emerging to a well-established human pathogen.

Management and Prevention of Opportunistic Infections in the HIV-Infected Patient

With the introduction of potent antiretroviral therapy, the incidence of opportunistic infections (OIs) as well as death has dramatically decreased since 1996. Opportunistic infections are seen mainly in three groups: (1) newly diagnosed patients not receiving antiretroviral therapy and presenting with an OI, (2) patients nonadherent to antiretroviral and OI treatment regimens or (3) patients whose antiretroviral therapy has failed. This article will review the most common opportunistic infections (OIs) seen in the HIV-infected individual and their treatment. The current guidelines for the prophylaxis against these OIs will also be discussed.

Acute pancreatitis during immunosuppression with tacrolimus following an allogeneic umbilical cord blood transplantation

Tacrolimus is increasingly used for graft-versus-host disease (GVHD) prophylaxis and therapy in the allogeneic stem cell transplant (allo-SCT) setting. Pancreatitis, previously described as a side-effect of cyclosporine, has not been reported in allo-SCT recipients receiving tacrolimus. We present here a case of acute pancreatitis in a 28-year-old patient with chronic myelogenous leukemia (CML) who received an unrelated umbilical cord blood transplant (UCBT) and tacrolimus for GVHD prophylaxis. On day +31 post-transplant, she developed severe acute pancreatitis with multiorgan failure, from which she recovered completely. Tacrolimus was the probable cause of pancreatitis in this patient.

The lipopolysaccharide of moraxella catarrhalis structural relationships and antigenic properties

Moraxella catarrhalis has recently been shown to be both widespread and pathogenic, in contrast to previous reports. Several factors have been suggested as virulence factors, lipopolysaccharide (LPS) being one. Recent studies have shown the LPS to be without the O-chain, i.e. the polysaccharide part, and to have specific structural features corresponding to each of the three serogroups, A, B and C. The structures resemble in many respects those present in other Gram-negative nonenteric bacteria, with a galabiosyl element as a prominent common denominator. The presence of such common structures suggests that the LPS of these bacteria might be a part of a mechanism of survival for bacteria colonizing the human host.

Acute pancreatitis. A fatal complication of AIDS therapy

Pancreatic disease in patients with AIDS often is so mild that the diagnosis may be missed. The pancreas can be affected by systemic illness caused by opportunistic infections, Kaposi's sarcoma, or lymphoma. More commonly, drugs used to treat patients infected with human immunodeficiency virus can cause pancreatitis and result in significant morbidity and, rarely, mortality. We report one such case in a 47-year-old patient with AIDS in whom pancreatitis developed while taking 2',3'-dideoxyinosine (ddI). His condition improved on ddI withdrawal, but he suffered a fatal relapse while receiving 2',3'-dideoxycytidine and trimethoprim-sulfamethoxazole. This case gives me the opportunity to review the literature regarding the incidence, causes, and diagnosis of human immunodeficiency virus-associated pancreatitis.

Antigenic characterization and analysis of the human immune response to outer membrane protein E of Branhamella catarrhalis

Outer membrane protein E (OMP E) is a 50-kDa major OMP of Branhamella catarrhalis. Polyclonal antisera and four monoclonal antibodies (MAbs) to OMP E were generated to study its antigenic structure. All antibodies recognized epitopes in all 19 B. catarrhalis strains tested by immunoblot assays. By flow cytometry, it was determined that MAbs 1B3 and 9G10d recognized epitopes which are expressed on the surface of the intact bacterium, while MAbs IC11 and 7C10 recognized epitopes which were buried within the outer membrane. A competitive enzyme-linked immunosorbent assay showed that MAbs 1B3 and 9G10d recognize the same or closely related epitopes. Proteinase K treatment of whole bacterial cells revealed that MAbs 1B3 and 9G10d recognize a surface-exposed epitope located in the 17-kDa region towards the amino terminus of OMP E. The human serum and mucosal antibody responses to OMP E in adults with chronic bronchitis were studied. A majority of these patients had immunoglobulin A to OMP E in sputum supernatants. None of ten adults who experienced lower respiratory tract infections due to B. catarrhalis demonstrated a clear-cut rise in antibody titer to OMP E in serum or sputum supernatant. This study has demonstrated that OMP E has at least one surface-exposed epitope which is highly conserved among strains of B. catarrhalis and which is located in the amino-terminal 184 amino acids of the molecule.

Human immunoglobulin isotype and IgG subclass response to different antigens of Moraxella catarrhalis

Enzyme immunoassays were tested for the determination of antibodies of different isotypes and IgG subclasses to Moraxella catarrhalis in human sera. An assay based on an outer membrane protein preparation (OMP) as antigen was compared to assays using whole bacterial cells and a purified lipopolysaccharide preparation. There was a good correlation between the results obtained with the OMP preparation and the whole-cell antigen. In paired sera, optimal sensitivity was obtained by using the OMP preparation as coating antigen and testing for a rise in IgG3 antibodies. However, patients with high levels of antibodies in acute serum had no or only an insignificant antibody response during infection.

Lack of serotype-specific antibody response to lipopolysaccharide antigens of Moraxella catarrhalis during lower respiratory tract infection

An enzyme immunoassay (EIA) was used to determine the antibody response to different serotypes of lipopolysaccharide (LPS) antigens of Moraxella catarrhalis in adult patients with lower respiratory tract infections (LRTI). Moraxella catarrhalis was isolated from sputum or nasopharyngeal samples from 20 patients with LRTI. Sixteen of the isolates were serotype A, four were type B and none were type C. The antibody response to the different LPS serotypes was determined in paired sera from patients suffering from LRTI. In addition to the 20 patients with Moraxella catarrhalis isolated (Group 1), a group of seven patients with LRTI of unknown etiology (Group 2) and a group of ten patients with LRTI of known other bacterial etiology (Group 3) were selected for this study. An increase in antibody levels of > 1.5-fold (convalescent-/acute-phase serum) was recorded in approximately half of the patients, not only in the first group (Moraxella catarrhalis isolated) but also in the other two groups. However, in the first and second groups there was a correlation between an increase in antibody levels in the LPS EIA and in an EIA using whole bacterial cells as antigen. In the group of patients in whom Moraxella catarrhalis was isolated, the antibody response to LPS antigens was not serotype specific. The antibody response to type-A and type-B LPS was more predominant than the response to type-C LPS in most patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Paromomycin-associated pancreatitis in HIV-related cryptosporidiosis

OBJECTIVE

To report a case of pancreatitis related to paromomycin administration.

CASE SUMMARY

A 39-year-old man with AIDS developed pancreatitis concurrent with successful treatment of intestinal cryptosporidiosis with paromomycin. The hyperamylasemia resolved with discontinuation of the agent and recurred when paromomycin treatment was reinstituted.

DISCUSSION

To our knowledge, this is the first reported case of pancreatitis believed to be induced by paromomycin. Although pancreatitis in HIV-infected patients has multiple causes, the nature of this case suggests the involvement of paromomycin. The mechanism of action is unclear.

CONCLUSIONS

Pancreatitis should be considered in the differential diagnosis of abdominal pain in patients who are treated with paromomycin.

Molecular cloning and characterization of outer membrane protein E of Moraxella (Branhamella) catarrhalis

Outer membrane protein E (OMP E) is a 50-kDa protein of Moraxella (Branhamella) catarrhalis. It is a potential vaccine antigen because it is expressed on the surface of the bacterium and has antigenic determinants which are conserved among most strains of M. catarrhalis. To clone the gene encoding OMP E, an EMBL-3 genomic library of strain 25240 was screened with a family of degenerate oligonucleotides based on the amino-terminal protein sequence. The OMP E gene was identified in one of the six positive clones by Southern blot analysis. An open reading frame of 1,377 bp encoding a protein of 460 amino acids was identified. The calculated molecular mass of the mature protein of 436 amino acid residues was 47.03 kDa, which correlated well with the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein product of the OMP E gene had a leader peptide of 25 amino acids and a signal peptidase 1 cleavage site similar to those of known OMPs of Escherichia coli. The transcription initiation site of the OMP E gene was mapped by primer extension to be 78 nucleotides upstream of the ATG start codon. Borderline homology was found to the FadL protein of E. coli (49.1% similarity and 25.6% identity), which is involved in the binding and transport of fatty acids. Analysis of restriction fragment length polymorphisms of the OMP E genes of 19 different strains of M. catarrhalis showed that the OMP E gene is highly conserved. The high degree of conservation of sequences of the OMP E genes of M. catarrhalis from diverse sources, along with earlier observations that the protein contains antigenic determinants on the bacterial surface, indicates that OMP E should be studied further as a potential vaccine antigen.

Expression of fimbriae and host response in Branhamella catarrhalis respiratory infections

Sputum during the acute exacerbation of chronic respiratory diseases were observed under the electron microscope, to determine the in vivo expression of surface structures of Branhamella catarrhalis (B. catarrhalis), the polymorphonuclear neutrophil (PMN) response to B. catarrhalis infections, and the composition of sputum. It was found that during infection fimbriae are expressed in B. catarrhalis. However, there were sparsely to densely fimbriated bacteria in each sputum sample. The length of the fimbriae were from 50 to 76 nm. In the sparsely fimbriated B. catarrhalis, external to the cell wall, a thin, granular, electron-dense layer was observed. Due to the presence of fimbriae, this layer was not seen in densely fimbriated B. catarrhalis. Blebs were also found in B. catarrhalis. PMNs were found to phagocytose both B. catarrhalis and debris. Evidence was found that debris were formed mainly by the destruction of PMNs. Bacteria as well as debris were phagocytosed by PMNs.

Pancreatitis during intravenous pentamidine therapy in an AIDS patient with prior exposure to didanosine

OBJECTIVE

To report a case of an HIV-positive man who received sequential didanosine and pentamidine treatment and subsequently developed acute clinical pancreatitis.

CASE SUMMARY

In June 1992 didanosine 200 mg po bid was initiated in a 30-year-old man with AIDS. After a 22-week course of didanosine, the patient was hospitalized and didanosine was discontinued on day 4. The patient then received 8 days of treatment for a presumed Pneumocystis carinii pneumonia (PCP) with pentamidine 4 mg/kg/d iv. As the patient responded clinically to therapy, he was discharged home to complete a 21-day course of pentamidine. On day 14 of therapy, the patient experienced nausea, vomiting, diarrhea, fatigue, and was hypotensive. The dosage of pentamidine was reduced by 50 percent. After receiving 18 doses of pentamidine, treatment was discontinued, as symptoms had worsened and serum amylase and lipase concentrations were elevated. The patient was hospitalized and the diagnosis of acute clinical pancreatitis was made. After a 21-day hospitalization, the patient was discharged home in fair condition on hyperalimentation.

DISCUSSION

Potential causes of pancreatitis, including opportunistic infections, neoplasms, and drugs, are discussed. The most probable factors associated with pancreatitis in our patient are didanosine and pentamidine therapy.

CONCLUSIONS

As our patient developed pancreatitis following sequential administration of didanosine and pentamidine, it would be prudent to monitor for signs and symptoms of pancreatitis in similar cases. In addition, didanosine should be discontinued during and for one week following treatment of PCP when pentamidine is used.

Purification and characterization of a high-molecular-weight outer membrane protein of Moraxella (Branhamella) catarrhalis

Moraxella (Branhamella) catarrhalis is an important bacterial cause of otitis media in children and lower respiratory tract infections in adults. In this study, we describe the presence of a novel high-molecular-weight outer membrane protein (HMW-OMP). This protein varies from 350 to 720 kDa in apparent molecular mass among strains by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The protein was detected on SDS-PAGE in 13 of 14 strains tested. We developed a monoclonal antibody and polyclonal antisera to this protein. In immunoblot assays, the protein was present in all 14 strains tested. The immunoblot assays suggest that the protein has at least one epitope that is conserved among strains. A purification method using anion-exchange chromatography is described. Treatment of outer membrane preparations and purified protein by heat and reducing agents did not change the apparent molecular mass of the HMW-OMP. Formic acid treatment of outer membrane preparations and purified HMW-OMP produced a single band with an apparent molecular mass of 120 to 140 kDa. We postulate that this may be the monomer of an oligomeric protein. The HMW-OMP, which varies in molecular mass among strains and is antigenically conserved, will be studied further to determine its role in the human immune response and may be useful as a marker in studying strain acquisition in patients.

Ceftriaxone-induced acute pancreatitis

OBJECTIVE

To report a case probable ceftriaxone-induced acute pancreatitis.

CASE SUMMARY

A patient with a history of short-bowel syndrome on home total parenteral nutrition developed fever, chills, and right flank pain. She was diagnosed with gram-negative catheter sepsis and prescribed antibiotic therapy to be administered for four weeks. After completion of the first week of therapy, the antibiotic regimen was changed to intravenous injections of ceftriaxone to be given daily at home. Prior to discharge the patient developed acute abdominal pain, leukocytosis, jaundice, and markedly elevated lipase and amylase concentrations consistent with acute pancreatitis. The patient's condition improved upon discontinuation of the ceftriaxone and the remainder of her stay was uneventful.

DISCUSSION

There is only one other case report in the literature of probable ceftriaxone-induced pancreatitis. Multiple other medications have been implicated in causing acute pancreatitis. The exact mechanism of this uncommon adverse effect of ceftriaxone is unknown.

CONCLUSIONS

There was a temporal relationship between the development of this patient's signs and symptoms and the administration of ceftriaxone. We could not identify any other factors that may have been responsible for the development of her acute pancreatitis. Ceftriaxone should be considered as a possible etiologic agent in patients who present with acute abdominal pain and elevated lipase and amylase concentrations.

Variability of surface-exposed antigens of different strains of Moraxella catarrhalis

For serological diagnosis of infection with Moraxella (Branhamella) catarrhalis it is important to determine if there is variability of antigenic properties among different strains. Cross-reactions of nine strains were investigated by an immunofluorescence test using sera from immunized rabbits. All titres but one were 1:256 or higher, the highest being 1:4096. Thus a high degree of antigenic similarity was demonstrated among different strains of Moraxella catarrhalis. However, the homologous titres of six sera were 2 to 16 times higher than the titres for other strains indicating strain variations in antigenic properties of some surface components. There was no correlation between lipopolysaccharide type and titre in the immunofluorescence test.

Characterization of an antigenically conserved heat-modifiable major outer membrane protein of Branhamella catarrhalis

Branhamella catarrhalis is a common cause of otitis media in children and of respiratory infections in adults with chronic bronchitis. Little is known about the antigenic structure of the outer membrane proteins (OMPs). In this study, two murine monoclonal antibodies, 7D6 and 5E8, were developed and used to characterize the major heat-modifiable OMP (OMP C/D) of B. catarrhalis. Immunoblot assays indicated that OMP C/D is heat modifiable, having a molecular mass of 55 kDa at room temperature and a mass of 60 kDa when heated under reducing conditions. Expression of the epitopes is independent of growth phase and growth media. Both epitopes are present in 51 of 51 strains of B. catarrhalis tested and are highly specific for Branhamella strains, being absent from a variety of other gram-negative species. Antibody 5E8 recognizes an epitope which is expressed on the surface of the intact bacterium. We conclude that OMP C/D is a major, heat-modifiable OMP antigen that expresses at least one stable, conserved epitope on the surface of B. catarrhalis. Future studies should focus on the role of OMP C/D in pathogenesis and on its potential role as a vaccine antigen.

Dideoxyinosine in children with symptomatic human immunodeficiency virus infection

BACKGROUND

2',3'-Dideoxyinosine (ddl) is a dideoxynucleoside with potent activity in vitro against the human immunodeficiency virus (HIV). In initial clinical trials in adults, ddl showed evidence of antiretroviral activity with little hematologic toxicity.

METHODS

We conducted a phase I-II study in 43 children with symptomatic (CDC class P-2) HIV infection. Of these children, 16 (median age, 10 years) had previously received zidovudine, and 27 (median age, 2.6 years) had not. ddl was administered orally in three divided doses totalling 60, 120, 180, 360, or 540 mg per square meter of body-surface area per day for 24 weeks. Eight of the 43 patients did not complete 24 weeks of ddl: 6 died, 1 was withdrawn because of progressive disease, and the other because of toxicity.

RESULTS

After oral administration, ddl was rapidly absorbed, although its bioavailability varied greatly among patients. Pancreatitis developed in two children, one receiving ddl at each of the two highest doses. The median CD4 cell count in 38 patients with paired counts increased from 0.218 x 10(9) per liter (218 per cubic millimeter) at base line to 0.327 x 10(9) per liter (327 per cubic millimeter) after 20 to 24 weeks (P = 0.001). Those with CD4 cell counts above 0.1 x 10(9) per liter (100 per cubic millimeter) at base line were significantly more likely to improve in this respect. The median levels of p24 antigen (in 27 patients with detectable levels at entry) declined from 272 pg per milliliter at base line to 77 pg per milliliter at 20 to 24 weeks (P = 0.005). The plasma concentration of ddl correlated significantly with both the degree of decline in the p24 antigen and the degree of improvement in IQ score. Improvement in clinical and immunologic measures occurred in both the previously untreated patients and in those who had been treated with zidovudine.

CONCLUSIONS

Dideoxyinosine was well tolerated and showed promising antiretroviral activity in HIV-infected children. The correlation between the clinical response and the plasma concentration of ddl indicates that bioavailability is an important consideration in the use of ddl to treat HIV infection and that individualized pharmacokinetic monitoring and dose adjustment may be important for optimal activity.