Cloning and expression of class A beta-lactamase gene blaA(BPS) in Burkholderia pseudomallei

The beta-lactamase gene blaA(BPS) in Burkholderia pseudomallei was cloned and expressed in Escherichia coli. BPS-1 is a cephalosporinase with an isoelectric point of 7.7. Sequence analysis of BPS-1 revealed conserved motifs typical of class A beta-lactamases and a relationship to the PenA (in B. cepacia) and BlaI (in Yersinia enterocolitica) lineages.

Candida tropicalis fungaemia in adult patients with haematological malignancies: clinical features and risk factors

Candida tropicalis fungaemia is a serious opportunistic infection. Eighteen consecutive patients with C. tropicalis fungaemia diagnosed within a five-year period were studied retrospectively. All patients had haematological malignancies treated by chemotherapy or bone marrow transplantation (BMT). Antifungal prophylaxis included nystatin (20 mg daily) for patients receiving chemotherapy, and fluconazole (200 mg daily) for patients undergoing BMT. Sixteen patients had refractory and advanced haematological malignancies. All patients were neutropenic, had central venous catheters, and were receiving treatment with broad-spectrum antibiotics at the time of fungaemia. Septic shock with skin emboli were the most common presenting features. In seven cases, fungaemia was preceded by a positive culture of C. tropicalis in the urine. Concomitant bacteraemia was found in 11 cases, of which six cases were due to Staphylococcus aureus. The overall mortality rate was 56%. The predominance of chemotherapy-treated patients developing fungaemia in this series might be attributable to the omission of fluconazole prophylaxis. The clinicopathologic features and risk factors identified in this study may help design better treatment strategies for this often-lethal complication.

Clinicopathological features and risk factors of clinically overt haemorrhagic cystitis complicating bone marrow transplantation

Haemorrhagic cystitis (HC) is an important complication after bone marrow transplantation (BMT). Overt HC (grade > or =2, gross haematuria, clot retention and impairment of renal function), clinically more important than mild and occult HC (grade 1, microscopic haematuria), leads to substantial morbidity and occasional mortality. We retrospectively analyzed 32 cases of clinically overt HC from a series of 236 BMT patients. Significant risk factors included the use of busulphan during conditioning, allogeneic BMT and acute GVHD. Logistic regression showed GVHD to be the most important risk factor. According to the time of engraftment, HC could be divided into pre- and post-engraftment subtypes. Pre-engraftment HC was brief, not more severe than grade 2, and subsided with supportive treatment. In contrast, post-engraftment HC was protracted, often of grade > or =3, associated with severe GVHD, and required surgical intervention in many cases. Polyoma BK viruria, but not adenoviruria, could be demonstrated in both types of HC. The increased severity and association with GVHD of post-engraftment HC suggested that attack of urothelium by immunocompetent cells, possibly directed against BK viral antigens, might play a pathogenetic role.

Emergence of cotrimoxazole- and quinolone-resistant Campylobacter infections in bone marrow transplant recipients

Clinical and microbiological data were collected prospectively from 704 patients who underwent bone marrow transplantation (BMT) during an 11-year period (1991-2001), and the first two cases of Campylobacter infection occurring in BMT recipients in the pre-engraftment period were identified. The two cases occurred on days 2 and 3 post-BMT, respectively. Both patients had Campylobacter jejuni enteritis, and one case was complicated by bacteraemia. In both cases the presenting symptoms were indistinguishable from hospital-acquired pre-engraftment diarrhoea, which is commonly caused by Clostridium difficile. Both of the Campylobacter jejuni isolates were resistant to cotrimoxazole and ciprofloxacin. Both patients responded to intravenous meropenem and subsequently had uneventful marrow engraftment.

Speechless after bone marrow transplantation: a rare complication of parainfluenza virus related group in an adult

Upper respiratory tract (URT) viral infections may cause severe consequences during myeloablative bone marrow transplantation (BMT). We present a patient with parainfluenza virus (PIV) infection during the course of BMT. He remained relatively asymptomatic during the course of cytopenia, but presented with complete loss of voice and severe laryngitis a few days after engraftment, which is not usual for adult PIV infections. Seroconversion to PIV and marked increase in antibody titres was demonstrated, with complete lymphoid engraftment. Our case illustrated that the virulence of some URT viral infections depend on host immune factors, and may remain latent until graft versus host responses can be mounted.

Isolated splenic tuberculosis presenting with pyrexia of unknown origin

We report a case of a 62-y-old man who presented with fever, malaise and weight loss. He was diagnosed with pyrexia of unknown origin due to tuberculosis of the spleen. Combination anti-tuberculous therapy was administered and fever gradually subsided after 6 weeks. A 12-month course of anti-tuberculous treatment would appear to be appropriate for the treatment of most patients with splenic tuberculosis.

Ralstonia pickettii bacteraemia in a cord blood transplant recipient

A seven-year old boy with acute lymphoblastic leukemia underwent an HLA mismatched cord blood transplant. He developed grade 2 mucositis requiring morphine infusion and grade 3-4 hyperacute graft-versus-host disease affecting the skin, gastrointestinal tract, and liver requiring pulse methylprednisolone. On days 21, 23, and 24 post-transplant, blood culture obtained through the central line and periphery were positive for Ralstonia pickettii. The same strain (with the same biochemical profile and antibiotic susceptibility pattern) was also recovered from surveillance throat swab cultures from day 11 to day 24 and surveillance rectal swab cultures from day 16 to day 24. The patient responded to intravenous cefoperazone/sulbactam and ciprofloxacin and blood culture became negative 3 days after commencement of the antibiotics. Although R. pickettii is of low virulence and is a frequent contaminant of blood cultures, it should not be overlooked when it is repeatedly recovered from sterile body fluids, especially in immunocompromised hosts.

Laribacter hongkongensis gen. nov., sp. nov., a novel gram-negative bacterium isolated from a cirrhotic patient with bacteremia and empyema

A bacterium was isolated from the blood and empyema of a cirrhotic patient. The cells were facultatively anaerobic, nonsporulating, gram-negative, seagull shaped or spiral rods. The bacterium grows on sheep blood agar as nonhemolytic, gray colonies 1 mm in diameter after 24 h of incubation at 37 degrees C in ambient air. Growth also occurs on MacConkey agar and at 25 and 42 degrees C but not at 4, 44, and 50 degrees C. The bacterium can grow in 1 or 2% but not 3, 4, or 5% NaCl. No enhancement of growth is observed with 5% CO(2). The organism is aflagellated and nonmotile at both 25 and 37 degrees C. It is oxidase, catalase, urease, and arginine dihydrolase positive, and it reduces nitrate. It does not ferment, oxidize, or assimilate any sugar tested. 16S rRNA gene sequencing showed that there are 91 base differences (6.2%), 112 base differences (7.7%), and 116 base differences (8.2%) between the bacterium and Microvirgula aerodenitrificans, Vogesella indigofera, and Chromobacterium species, respectively. The G+C content (mean and standard deviation) is 68.0% +/- 2.43%, and the genomic size is about 3 Mb. Based on phylogenetic affiliation, the bacterium belongs to the Neisseriaceae family of the beta-subclass of Proteobacteria. For these reasons, a new genus and species, Laribacter hongkongensis gen. nov., sp. nov., is proposed, for which HKU1 is the type strain. Further studies should be performed to ascertain the potential of this bacterium to become an emerging pathogen.

Differences in clinical and laboratory diagnostic characteristics of penicilliosis marneffei in human immunodeficiency virus (HIV)- and non-HIV-infected patients

We compared the clinical and laboratory features of human immunodeficiency virus (HIV)- and non-HIV-infected patients with penicilliosis marneffei. HIV-infected patients had a higher incidence of fungemia. A total of 85.7% of the HIV-negative patients had underlying diseases including hematologic malignancies or had received therapy with corticosteroids or cytotoxic agents. By a Penicillium marneffei-specific mannoprotein Mp1p enzyme-linked immunosorbent assay, serum antigen titers were found to be higher in HIV-positive patients, whereas serum antibody levels were found to be higher in HIV-negative patients.

Characterization of AFMP1: a novel target for serodiagnosis of aspergillosis

We cloned the AFMP1 gene, which encodes the first antigenic cell wall galactomannoprotein in Aspergillus fumigatus. AFMP1 codes for a protein, Afmp1p, of 284 amino acid residues, with a few sequence features that are present in Mp1p, the antigenic cell wall mannoprotein in Penicillium marneffei that we described previously, as well as several other cell wall proteins of Saccharomyces cerevisiae and Candida albicans. It contains a serine- and threonine-rich region for O glycosylation, a signal peptide, and a putative glycosylphosphatidyl inositol attachment signal sequence. Specific anti-Afmp1p antibody was generated with recombinant Afmp1p protein purified from Escherichia coli to allow further characterization of Afmp1p. Afmp1p has a high affinity for Galanthus nivalis agglutinin, a characteristic indicative of a mannoprotein. Furthermore, it was recognized by a rat monoclonal antibody against the galactofuran side chain of galactomannan, indicating that it is a galactomannoprotein. Ultrastructural analysis by immunogold staining indicated that Afmp1p is present in the cell walls of the hyphae and conidia of A. fumigatus. Finally, it was observed that patients with aspergilloma and invasive aspergillosis due to A. fumigatus develop a specific antibody response against Afmp1p. This suggested that the recombinant protein and its antibody may be useful for serodiagnosis in patients with aspergilloma or invasive aspergillosis, and the protein may represent a good cell surface target for host humoral immunity.

Nasopharyngeal carriage of antimicrobial-resistant Streptococcus pneumoniae among young children attending 79 kindergartens and day care centers in Hong Kong

Resistance to penicillin and multiple antimicrobial agents among Streptococcus pneumoniae strains is becoming an increasing problem worldwide and in Asia. To determine the prevalence of carriage of S. pneumoniae isolates not susceptible to penicillin in young children, we obtained nasopharyngeal swab specimens from 1,978 children (ages, 2 to 6 years) attending 79 day care centers or kindergartens. Three hundred eighty-three strains of S. pneumoniae were isolated from these children. Fifty-eight percent of these isolates had reduced susceptibility to penicillin, 123 (32.1%) were intermediate, and 100 (26.1%) were resistant. A very high penicillin MIC (4 microg/ml) was found in 3.3% of the isolates. The isolates also demonstrated high rates of resistance to other antimicrobial agents (51.2% to cefaclor, 50.2% to cefuroxime, 42.8% to cefotaxime, 80.7% to trimethoprim-sulfamethoxazole, 77% to erythromycin, 60% to clindamycin, and 33.7% to chloramphenicol). No isolate was resistant to fluoroquinolone. Multidrug resistance (not susceptible to the beta-lactams and three or more other classes) was found in 39.4% of the isolates. Risk factors for the carriage of S. pneumoniae not susceptible to penicillin were multiple physician visits in the preceding 3 months and use of antimicrobial agents by the individual or by household members in the preceding 3 months. In the logistic regression analysis, only the use of antimicrobial agents in the preceding 3 months was an independent risk factor (P = 0.004; odds ratio, 2; 95% confidence interval, 1.2 to 3.2). This study demonstrated the high prevalence of antibiotic-resistant S. pneumoniae in healthy young children in the community in Hong Kong.

Adoptive transfer of autologous Epstein-Barr virus-specific cytotoxic T cells for nasopharyngeal carcinoma

Tumor cells from NPC patients are regularly and latently infected with EBV. To examine whether the virus serves as target for immune intervention of the cancer, we determined levels of EBV-specific CTLp in peripheral blood from NPC patients, long-term survivors of the cancer and healthy subjects. CTLp levels of test subjects varied between 3- 3,000/10(6) PBMCs. The plasma EBV burden increased when the CTLp level fell below 150, whereas the EBV burden of PBMCs was not correlated with CTLp level. Compared with healthy carriers, CTLp levels of patients were lower and varied over a wider range, between 3-1,500/10(6) PBMCs. The quantitative immune deficit was probably attributed to the tumor because, first, CTLp in survivors was restored to levels similar to those in healthy carriers after the tumor had been successfully treated. Second, the CTLp level changed as disease progressed, being lower in local disease, increased in locoregional disease and decreased again when the tumor metastasized. Based on these findings, 4 patients with advanced disease were infused with 5 x 10(7)-3 x 10(8) autologous EBV CTLs. The treatment was safe and unaccompanied by inflammatory or other complications, but whether it improved tumor control could not be discerned from the large tumor bulk. Nevertheless, the treatment regularly increased CTLp levels of patients, maintained it at higher levels for protracted periods and, in 3 patients, restored host surveillance of EBV replication, reducing the plasma EBV burden. Taken together, these results provided a rationale to further explore EBV as a target of immune intervention of NPC.

Quantification of polyoma BK viruria in hemorrhagic cystitis complicating bone marrow transplantation

Polyoma BK virus (BKV) is frequently identified in the urine of bone marrow transplantation (BMT) patients with hemorrhagic cystitis (HC). However, viruria is common even in asymptomatic patients, making a direct causative role of BKV difficult to establish. This study prospectively quantified BK viruria and viremia in 50 BMT patients to define the quantitative relationship of BKV reactivation with HC. Adenovirus (ADV) was similarly quantified as a control. More than 800 patient samples were quantified for BKV VP1 gene with a real-time quantitative polymerase chain reaction. Twenty patients (40%) developed HC, 6 with gross hematuria (HC grade 2 or higher) and 14 with microscopic hematuria (HC grade 1). When compared with asymptomatic patients, patients with HC had significantly higher peak BK viruria (6 x 10(12) versus 5.7 x 10(7) genome copies/d, P <.001) and larger total amounts of BKV excreted during BMT (4.9 x 10(13) versus 7.7 x 10(8) genome copies, P <.001). There was no detectable increase in BK viremia. Binary logistic regression analysis showed that BK viruria was the only risk factor, with HC not related to age, conditioning regimen, type of BMT, and graft-versus-host disease. Furthermore, the levels of ADV viruria in patients with or without HC were similar and comparable with those of BK viruria in patients without HC, suggesting that the significant increase in BK viruria in HC patients was not due to background viral reactivation or damage to the urothelium. BK viruria was quantitatively related to the occurrence of HC after BMT.

Group G beta-hemolytic streptococcal bacteremia characterized by 16S ribosomal RNA gene sequencing

Little is known about the relative importance of the four species of Lancefield group G beta-hemolytic streptococci in causing bacteremia and the factors that determine the outcome for patients with group G beta-hemolytic streptococcal bacteremia. From 1997 to 2000, 75 group G beta-hemolytic streptococcal strains were isolated from the blood cultures of 66 patients. Sequencing of the 16S rRNA genes of the group G beta-hemolytic streptococci showed that all 75 isolates were Streptococcus dysgalactiae subspecies equisimilis. The API system (20 STREP) and Vitek system (GPI) successfully identified 65 (98.5%) and 62 (93.9%) isolates, respectively, as S. dysgalactiae subspecies equisimilis with >95% confidence, whereas the ATB Expression system (ID32 STREP) only successfully identified 49 isolates (74.2%) as S. dysgalactiae subspecies equisimilis with >95% confidence. The median age of the patients was 76 years (range, 33 to 99 years). Fifty-six patients (85%) were over 60 years old. All patients had underlying diseases. No source of the bacteremia was identified (primary bacteremia) in 34 patients (52%), whereas 17 (26%) had cellulitis and 8 (12%) had bed sore or wound infections. Fifty-eight patients (88%) had community-acquired group G streptococcal bacteremia. Sixty-two patients (94%) had group G Streptococcus recovered in one blood culture, whereas 4 patients (6%) had it recovered in multiple blood cultures. Fifty-nine patients (89%) had group G Streptococcus as the only bacterium recovered in their blood cultures, whereas in 7 patients other bacteria were recovered concomitantly with the group G Streptococcus in the blood cultures (Staphylococcus aureus in 3, Clostridium perfringens in 2, Citrobacter freundii in 1, and Bacteroides fragilis in 1). Overall, 10 patients (15%) died. Male sex, diagnosis other than cellulitis, hospital-acquired bacteremia, and multiple positive blood cultures were associated with mortality [P < 0.005 (relative risk [RR] = 7.6), P < 0.05 (RR = 3.7), P < 0.005 (RR = 5.6), and P < 0.05 (RR = 5.6), respectively]. Unlike group C beta-hemolytic streptococcal bacteremia, group G beta-hemolytic streptococcal bacteremia is not a zoonotic infection in Hong Kong.

Identification of slide coagulase positive, tube coagulase negative Staphylococcus aureus by 16S ribosomal RNA gene sequencing

AIMS

To ascertain the clinical importance of a strain of slide coagulase positive but tube coagulase negative Staphylococcus species isolated from the blood culture of a 43 year old patient with refractory anaemia with excessive blasts in transformation who had neutropenic fever.

METHODS

The isolate was investigated phenotypically by standard biochemical methods using conventional biochemical tests and two commercially available systems, the Vitek (GPI) and API (Staph) systems. Genotypically, the 16S ribosomal RNA (rRNA) gene of the bacteria was amplified by the polymerase chain reaction (PCR) and sequenced. The sequence of the PCR product was compared with known 16S rRNA gene sequences in the GenBank by multiple sequence alignment.

RESULTS

Conventional biochemical tests did not reveal a pattern resembling a known Staphylococcus species. The Vitek system (GPI) showed that it was 94% S. simulans and 3% S. haemolyticus, whereas the API system (Staph) showed that it was 86.8% S. aureus and 5.1% S. warneri. 16S rRNA gene sequencing showed that there was a 0 base difference between the isolate and S. aureus, 28 base difference between the isolate and S. lugdunensis, 39 base difference between the isolate and S. schleiferi, 21 base difference between the isolate and S. haemolyticus, 41 base difference between the isolate and S. simulans, and 23 base difference between the isolate and S. warneri, indicating that the isolate was a strain of S. aureus. Vancomycin was subsequently prescribed and blood cultures taken four days after the start of treatment were negative.

CONCLUSIONS

16S rRNA gene sequencing was useful in ascertaining the clinical importance of the strain of slide coagulase positive but tube coagulase negative Staphylococcus species isolated from blood culture and allowing appropriate management.

Therapeutic efficacy of hepatitis B surface antigen-antibodies-recombinant DNA composite in HBsAg transgenic mice

Therapeutic efficacy of HBsAg-anti-HBs-recombinant DNA harboring hepatitis B virus (HBV) S gene complex was compared with three other therapeutic vaccine candidates (recombinant HBsAg, HBsAg complexed to anti-HBs antibodies and naked plasmid DNA encoding the HBV S gene). After four injections at 3-week intervals, the most pronounced decrease of serum HBsAg, the highest titer of anti-HBs response, the highest level of interferon-gamma produced by splenocytes and potent cytotoxicity T cell response were observed in the HBsAg-anti HBs-sDNA immunized group. Reduced expression of HBsAg in hepatocytes was also shown. The therapeutic mechanism of HBsAg-anti-HBs-DNA was speculated as modulation of HBsAg presentation via both endogenous and exogenous pathways.

Necrotising fasciitis of a limb

Between January 1992 and December 1998, we treated 24 patients with necrotising fasciitis of a limb. There were 15 men and nine women with a mean age of 59.8 years (5 to 86). The infection was usually confused with cellulitis. Exquisite pain and early systemic toxicity were the most consistent clinical features. Diabetes mellitus and hepatic cirrhosis were the most commonly associated medical diseases. One third of the patients died. Those with involvement of the limbs above the knee or elbow on admission had a significantly higher rate of mortality than those with distal lesions (Fisher's exact test, p = 0.027). There was no correlation between mortality and advanced age (Student's t-test, p = 0.22) or between amputation and survival (Fisher's exact test, p = 0.39).

Detection of RTX toxin gene in Vibrio cholerae by PCR

A PCR that amplifies a recently discovered Vibrio cholerae RTX (repeat in toxin) toxin gene was developed. Among 166 clinical and environmental isolates of V. cholerae causing epidemics and sporadic cases of cholera in various parts of the world, all were found to be toxigenic by both PCR and HEp-2 cell cytotoxicity assay. Standard strains of the classical biotype containing a deletion within the gene cluster exhibited negative results by both assays. This is the first rapid genotyping method for differentiation of V. cholerae O1 classical biotype strains from El Tor biotype strains as well as strains of other non-O1 serogroups including serogroup O139. The PCR assay that was developed also specifically detects RTX toxin genes in V. cholerae, as clinical isolates of Vibrio parahaemolyticus, diarrheagenic Escherichia coli, Aeromonas species, and Plesiomonas species were all negative by the RTX toxin-specific PCR as well as the HEp-2 cytotoxicity assay. These findings highlight the characteristics of the RTX toxins in V. cholerae. Their role in the pathogenicity of the bacterium requires further investigation.

groEL encodes a highly antigenic protein in Burkholderia pseudomallei

No recombinant protein is available for serodiagnosis of melioidosis. In this study, we report the cloning of the groEL gene, which encodes an immunogenic protein of Burkholderia pseudomallei. Bidirectional DNA sequencing of groEL revealed that the gene contained a single open reading frame encoding 546 amino acid residues with a predicted molecular mass of 57.1 kDa. Basic Local Alignment Search Tool analysis showed that the putative protein encoded by groEL is homologous to the chaperonins encoded by the groEL genes of other bacteria. It has 98% amino acid identity with the GroEL of Burkholderia cepacia, 98% amino acid identity with the GroEL of Burkholderia vietnamiensis, and 82% amino acid identity with the GroEL of Bordetella pertussis. Furthermore, it was observed that patients with melioidosis develop a strong antibody response against GroEL, suggesting that the recombinant protein and its monoclonal antibody may be useful for serodiagnosis in patients with melioidosis and that the protein may represent a good cell surface target for host humoral immunity. Further studies in these directions would be warranted.

Invasive disease due to Mucorales: a case report and review of the literature

OBJECTIVE

To review the mycology, pathogenesis, clinical characteristics, investigations, and treatment modalities of mucormycosis.

DATA SOURCES

A local case of mucormycosis; MEDLINE and non-MEDLINE search of the literature.

STUDY SELECTION

Key words for the literature search were 'mucormycosis' and 'Mucorales'; all available years of study were reviewed.

DATA EXTRACTION

Original articles, review papers, meta-analyses, and relevant book chapters were reviewed.

DATA SYNTHESIS

Mucormycosis is a fungal infection that is rare but increasingly recognised in the growing population of immunocompromised patients. It is caused by saprophytic non-septate hyphae of the order Mucorales. The pulmonary and disseminated forms commonly occur in patients with haematological malignancy, especially acute leukaemia and lymphoma, and those receiving treatment with immunosuppressive effects. The rhinocerebral form is more prevalent in patients with diabetes mellitus, particularly those with the complication of diabetic ketoacidosis. The use of amphotericin B combined with surgery remains the mainstay of treatment. The prognosis largely depends on prompt correction of the underlying risk factors. New strategies to combat this life-threatening infection will result from better understanding of its pathogenesis.

CONCLUSION

A high index of suspicion is needed, in appropriate clinical settings, to diagnose and aggressively treat this infection in view of the high mortality rate for susceptible patients.

Immunorestitution diseases in patients not infected with HIV

The aim of this study was to assess the clinical spectrum of immunorestitution disease (IRD) in hospitalized patients over a 12-month period. In nine of 18 patients who presented with clinical deterioration during reduction or cessation of immunosuppressants (n = 6) or bone marrow engraftment (n = 3), IRD cases included the following infections: scabies infestation (n = 1); gastric strongyloidiasis (n = 1); hepatosplenic candidiasis (n = 1); methicillin-resistant Staphylococcus aureus abscess formation (n = 2); polyomavirus-related hemorrhagic cystitis (n = 3); and influenza A pneumonitis (n = 1). Immunopathological damage during withdrawal of immunosuppression is an incidental way to uncover an asymptomatic infectious disease. Serial monitoring of hematological and clinical profiles is essential in making a diagnosis of IRD.