Use of the human colorectal adenocarcinoma (Caco-2) cell line for isolating respiratory viruses from nasopharyngeal aspirates

The human colorectal adenocarcinoma‐derived Caco‐2 cell line was evaluated as a means isolating common respiratory viruses from nasopharyngeal aspirates for the diagnosis of respiratory diseases. One hundred eighty‐nine direct immunofluorescence positive nasopharyngeal aspirates obtained from patients with various viral respiratory diseases were cultured in the presence of Caco‐2 cells or the following conventional cell lines: LLC‐MK2, MDCK, HEp‐2, and A549. Caco‐2 cell cultures effectively propagated the majority (84%) of the viruses present in nasopharyngeal aspirate samples compared with any positive cultures obtained using the panel cells (78%) or individual cell line MDCK (38%), HEp‐2 (21%), LLC‐MK2 (27%), or A549 (37%) cell lines. The differences against individual cell line were statistically significant (P = < 0.000001). Culture in Caco‐2 cells resulted in the isolation of 85% (36/42) of viruses which were not cultivated in conventional cell lines. By contrast, 80% (24/30) of viruses not cultivated in Caco‐2 cells were isolated using the conventional panel. The findings indicated that Caco‐2 cells were sensitive to a wide range of viruses and can be used to culture a broad range of respiratory viruses. J. Med. Virol. 85:874–879, 2013. © 2013 Wiley Periodicals, Inc.

Toxic scarlet fever complicating cellulitis: early clinical diagnosis is crucial to prevent a fatal outcome

We describe a case of toxic scarlet fever in a healthy adult with streptococcal cellulitis of the right elbow as a result of skin abrasion. The clinical picture mimicked that of drug eruption after treatment of cellulitis with antibiotics. Among the five cases of scarlet fever complicating cellulitis, including the present one, reported in the English literature, four had severe systemic complications and two died. As a result of re-emergence of invasive streptococcal infections, clinicians should be aware of the differential diagnosis of scarlet fever in patients presenting with cellulitis and skin rash. Early clinical diagnosis is crucial to exclude drug eruptions, prompt initiation of antibiotic treatment, and prevention of the potentially fatal outcome.

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.

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.

A crucial role of macrophages in the immune responses to oral DNA vaccination against hepatitis B virus in a murine model

In the previous study, we had shown that live oral vaccination with Salmonella typhimurium delivering plasmid DNA-HBsAg (oral DNA vaccine) evoked a vigorous T cell response and a weak antibody response with predominant subclass IgG2a in mice, suggesting a significant involvement by professional antigen presenting cells (APC). In the present study, this possibility was further studied by infecting peritoneal macrophages (MPhi) with the oral DNA vaccine. Although, the infected cells could only express low level of the viral antigen, they nevertheless stimulated a vigorous lymphocyte proliferation of splenocytes from immune mice, induced these cells to elaborate interferon-gamma and stimulated development of HBV-specific cytotoxicity against target cells expressing the viral antigen. Infusion of the infected MPhi evoked a vigorous Th 1 and cytotoxic T lymphocyte (CTL) response and a weak IgG2a antibody response in mice, which was essentially the same as response to the oral DNA vaccine. In contrast, recombinant protein vaccine evoked a vigorous IgG1 antibody response and a weak T cell response. While, given intramuscularly, the same plasmid DNA vaccine as that contained in the oral DNA vaccine evoked a vigorous IgG1 antibody response and a moderate T cell response in these animals. It was concluded that professional APC may orchestrate the immune response to live oral DNA vaccine and it was of interest to note that different vaccine formulation and routes of administration evoke distinct immune response to HBV.

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.

Ultrasonographic features of pseudotumorous form of ascariasis

We report the ultrasonographic findings of a 60 year old woman with pseudotumorous form of ascariasis. Real-time ultrasonographic examination using a curved array transducer revealed grossly thickened small bowel loops, multiple small circular deposits throughout the peritoneal cavity, and a moderate amount of ascites. The English literature on the different forms of abdominal ascariasis is reviewed. Specific signs, which include the 'strip' sign, the 'four-lines', 'inner tube', or 'double tube' sign, the 'bull's eye' or 'target' sign, a 'worm mass' or 'spaghetti-like' appearance, and the 'zig-zag' sign can be present in any form of abdominal ascariasis, as they represent the image of the Ascaris worms visualized under ultrasonographic examination. However, the non-specific signs are not peculiar to A. lumbricoides infections, but are results of secondary changes due to A. lumbricoides infections in the corresponding organs.

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.

Two cases of pyomyositis caused by Klebsiella pneumoniae and review of the literature

Two patients with diabetes mellitus developed Klebsiella pneumoniae pyomyositis involving multiple muscles and other metastatic foci associated with bacteraemia. The cases are presented here, and the 22 cases of gram-negative pyomyositis reported previously in the literature are reviewed. As gram-positive cocci cause 99% of pyomyositis, it is postulated that the pathogenesis of pyomyositis may be associated with the ability of the bacteria to adhere to muscles by various cell surface adhesins that are not present in gram-negative bacilli. It is also postulated that a high serum glucose concentration may facilitate the growth and formation of the Klebsiella pneumoniae capsule, hence increasing its virulence and causing serious disseminated Klebsiella infections in diabetic patients.

Identification of Arcobacter cryaerophilus isolated from a traffic accident victim with bacteremia by 16S ribosomal RNA gene sequencing

Traditional ways of identifying slow growing bacteria is slow and often difficult. In this study, a small, Gram-negative, facultative anaerobic, slow growing bacillus was isolated from the blood culture of a 7-year old traffic accident victim. The bacterium was non-hemolytic, catalase and oxidase positive. An attempt to use the Vitek system (GNI+) and the API system (20NE) to identify the strain was unsuccessful as the growth controls showed negative results. 16S ribosomal RNA gene sequencing showed that there was 1 base difference between the isolate and Arcobacter cryaerophilus (GenBank Accession no. U25805), 1 base difference between the isolate and A. cryaerophilus (GenBank Accession no. U34387), 10 base differences between the isolate and A. cryaerophilus (GenBank Accession no. L14624), 34 base differences between the isolate and A. butzleri (GenBank Accession no. U34386), 34 base differences between the isolate and A. butzleri (GenBank Accession no. U34387), and 38 base differences between the isolate and A. butzleri (GenBank Accession no. L14626), indicating that the isolate most closely resembled a strain of A. cryaerophilus. Identification of the isolate in our case by conventional methods was difficult, as the absence of a curved morphology has made it confused with other Gram-negative non-fermentative bacteria, and the slow growth rate has made it unidentifiable by both the Vitek and API systems. Although the exact source of infection and route of transmission in our case remains elusive, we speculate that the bacteria were transmitted through the respiratory tract while the boy was suffocated in the mud. The present report represents an example of showing the usefulness of 16S rRNA gene sequencing for identification of slow growing bacteria.

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.

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.

Polymicrobial outbreak of intermittent peritoneal dialysis peritonitis during external wall renovation at a dialysis center

OBJECTIVE

To investigate an outbreak of peritonitis in intermittent peritoneal dialysis (IPD) patients.

DESIGN

An outbreak investigation was performed to identify the etiology of the polymicrobial outbreak, and a retrospective case-control study was conducted to assess the risk factors for development of peritonitis.

SETTING

Renal dialysis center.

PATIENTS

Ten episodes of peritonitis occurred in 8 of 61 patients over a 6-month period in which 669 IPD procedures were analyzed.

INTERVENTIONS

Field visit to renal dialysis center to examine the entire IPD procedure, inspect the hospital environment, and perform air bacterial count.

MAIN OUTCOME MEASURES

The environmental factors and risk factors contributing to the polymicrobial peritonitis outbreak in IPD patients. The incidence of IPD peritonitis was determined before and after interventions.

RESULTS

The causative organisms included Acinetobacter baumanii (6), Stenotrophomonas maltophilia (2), Pseudomonas aeruginosa (1), Candida albicans (1), C. tropicalis (1), Enterococcus (3), and Enterobacteriaceae (2). Four episodes of peritonitis involved infection by more than one organism. Air sampling of the environment detected a median of 110 colony forming units of bacteria per cubic meter of air, 10% of which were found to be Acinetobacter baumanii. The source of this polymicrobial outbreak was attributed to the bamboo scaffolding structure covering the external wall of the hospital during renovation. A retrospective case-control study indicated that the absence of the flush-before-fill step was a risk factor for development of peritonitis.

CONCLUSION

In addition to invasive aspergillosis in transplant or oncology patients, Acinetobacter peritonitis in dialysis patients should be considered another microbial cause of outbreak associated with hospital renovation.

Unique immunogenicity of hepatitis B virus DNA vaccine presented by live-attenuated Salmonella typhimurium

A novel vaccine for hepatitis B virus (HBV) was designed by putting a naked DNA vaccine carrying hepatitis B surface antigen (HBsAg) into live-attenuated Salmonella typhimurium. Mucosal immunization by the oral route in mice showed significantly stronger cytotoxic T lymphocyte (CTL) response than recombinant HBsAg vaccination (P < 0.01 at an effector:target ratio of 100:1), while comparable to intramuscular naked DNA immunization at all effector:target ratios. Contrary to previous reports on naked DNA vaccines given intramuscularly, the IgG antibody response induced by the mucosal DNA vaccine is relatively weak when compared to recombinant HBsAg vaccine (P < 0.001 at day 21). These findings are supported by a high interferon-gamma but a low interleukin-4 level detected in the supernatant of splenic cell cultures obtained from mucosally immunized mice. As distinct to recombinant HBsAg vaccine which is effective for protection, oral mucosal DNA vaccine should be considered as a candidate for therapeutic immunization in chronic HBV infection, donor immunization before adoptive transfer of HBV-specific CTL to HBsAg positive bone marrow transplant recipients, and immunization of non-responders to recombinant HBsAg vaccine. This strongly cellular and relatively absent humoral response may make this vaccine a better candidate as a therapeutic vaccine for chronic HBV carriers than naked DNA vaccines, as the humoral response is relatively less important for the clearance of HBV from hepatocytes, but its presence may lead to side effects such as serum sickness and immune complex deposition in chronic HBV carriers.

Adult croup: a rare but more severe condition

We report the first adult patient with virologically confirmed croup caused by parainfluenza virus type 3 and review 10 cases of adult croup described in the English-language literature. Circumstantial evidence of viral infection was present in only 1 other case, in which there was a rise in antibody titer against influenza B virus. Ten patients (91%) required intensive care support. None of the 11 patients died. A comparison was also made between the 11 adults with croup and 43 children hospitalized with severe croup described in a representative paper published in 1984. Adult croup represents an apparently more severe disease entity than pediatric croup.

Biotyping of Penicillium marneffei reveals concentration-dependent growth inhibition by galactose

Thirty-two isolates of the dimorphic fungus Penicillium marneffei were studied for their biochemical properties. All isolates possessed the enzyme urease and were inhibited by 500 mg of cycloheximide per liter. No strain fermented glucose, and thus no strain fermented any of the other five sugars tested. All assimilated glucose, maltose, and cellobiose; only one of the isolates did not assimilate salicin. Totals of 65.6, 84.4, and 71.9% of the isolates assimilated trehalose, xylose, and nitrate, respectively. Twelve strains possessed the enzyme beta-galactosidase. Overall, 17 different biotypes were recognized, but no association was found between the human immunodeficiency virus status of the patients and the biotype. A novel finding of concentration-dependent growth inhibition of P. marneffei by galactose is described. Inhibition of growth occurred at a low concentration of galactose (0.015 to 0.25%) when galactose was the sole carbon source in the medium. Morphological changes of the fungal cells were observed in the presence of galactose.

Cell-wall-deficient bacteria and culture-negative febrile episodes in bone-marrow-transplant recipients

BACKGROUND

Although about 75-80% of neutropenic fevers are thought to be caused by infections, a causal organism can be confirmed microbiologically or suspected clinically in only 30-50%, and even fewer of these cases (16%) have a documented bacteraemia. The cause of neutropenic fever in the remaining cases remains elusive. We investigate the role of cell-wall-deficient bacteria in bone-marrow transplantation (BMT).

METHODS

Blood cultures were obtained from bone-marrow-transplant recipients and were inoculated into an aerobic bottle with resin, an anaerobic bottle, and a bottle to isolate cell-wall deficient bacteria. When growth was detected in the blood-culture bottle for cell-wall-deficient bacteria, 20 microL of the broth was subcultured and the isolate identified by standard biochemical methods. The microbiological findings were correlated with the clinical characteristics of the patients.

FINDINGS

From the 86 BMT recipients enrolled into the study, 798 sets of blood cultures were sent for laboratory analysis. 55 blood cultures were positive in the aerobic bottle, and the same isolates were also detected in 52 blood-culture bottles for cell-wall-deficient forms. For 20 sets of blood cultures, the isolates were detected only in the bottle for cell-wall-deficient forms. Blood for 13 (65%) of these 20 sets were sampled in the pre-engraftment neutropenic period, three (15%) during conditioning when the absolute neutrophil count was above 0.5 x 10(3)/L, and four (20%) in the post-engraftment period. 17 (85%) of the isolates were gram positive: four (20%) were Staphylococcus spp and ten (50%) were Bacillus spp. Antibiotic treatment was successful in 19 (95%) of 20 episodes.

INTERPRETATION

Bacteraemia due to cell-wall-deficient forms causes a significant proportion of so-called culture-negative febrile episodes in BMT recipients.

Isolation and characterization of a Salmonella enterica serotype Typhi variant and its clinical and public health implications

We report the isolation and characterization of a member of the family Enterobacteriaceae isolated from the gallbladder pus of a food handler. Conventional biochemical tests suggested Salmonella enterica serotype Typhi, but the isolate agglutinated with poly(O), 2O, 9O, and Vi Salmonella antisera but not with poly(H) or any individual H Salmonella antisera. 16S rRNA gene sequencing showed that there were two base differences between the isolate and Salmonella enterica serotype Montevideo, four base differences between the isolate and serotype Typhi, five base differences between the isolate and Salmonella enterica serotype Typhimurium, and six base differences between the isolate and Salmonella enterica serotype Dublin, indicating that the isolate was a strain of S. enterica. Electron microscopy confirmed that the isolate was aflagellated. The flagellin gene sequence of the isolate was 100% identical to that of the H1-d flagellin gene of serotype Typhi. Sequencing of the rfbE gene, which encoded the CDP-tyvelose epimerase of the isolate, showed that there was a point mutation at position +694 (G-->T), leading to an amino acid substitution (Gly-->Cys). This may have resulted in a protein of reduced catalytic activity and hence the presence of both 2O and 9O antigens. We therefore concluded that the isolate was a variant of serotype Typhi. Besides antibiotic therapy and cholecystectomy, removal of all stones in the biliary tree was performed for eradication of the carrier state.

Identification by 16S ribosomal RNA gene sequencing of an Enterobacteriaceae species with ambiguous biochemical profile from a renal transplant recipient

Traditional ways of identification of bacteria by phenotypic characteristics cannot be used for non-cultivable organisms and organisms with unusual biochemical profiles. In this study, an Enterobacteriaceae was isolated in pure growth from the mid-stream urine of a 67-year old renal transplant recipient with urinary tract infection. Conventional biochemical tests did not reveal a pattern resembling any known member of the Enterobacteriaceae family. The Vitek system (GNI+) showed that it was 18% Leclercia adecarboxylata and 55% Klebsiella ozaenae; whereas the API system (20E) showed that it was 99.8% Rahnella aquatilis. 16S ribosomal RNA gene sequencing showed that there was 7 base differences between the isolate and Enterobacter cloacae, 18 base differences between the isolate and Enterobacter asburiae, 17 base differences between the isolate and Enterobacter cancerogenus, 35 base differences between the isolate and K. ozaenae, 27 base differences between the isolate and L. adecarboxylata, and 72 base differences between the isolate and R. aquatilis, indicating that the isolate most closely resembled a strain of E. cloacae. Identification of the organism in this study is important, as the choice of antibiotics would be radically different. In this case, cephalosporins should be avoided regardless of in-vitro susceptibility as cephalosporins are well-known to select for AmpC derepressed mutants in Enterobacter, and previous administration of third-generation cephalosporins is more likely to be associated with multidrug resistant Enterobacter isolates than is administration of antibiotics that do not include a third-generation cephalosporin.

Candida tropicalis and Penicillium marneffei mixed fungaemia in a patient with Waldenström's macroglobulinaemia

A patient with Waldenstrom's macroglobulinaemia who had previously been treated with cladribine presented with septic arthritis caused by Escherichia coli. The patient's condition subsequently deteriorated, and he succumbed to pneumonia and mixed fungaemia due to Candida tropicalis and Penicillium marneffei. Profound lymphopenia coexisted with fungaemia. This is the first reported case of mixed Penicillium marneffei and Candida fungaemia and penicilliosis marneffei in a patient with Waldenstrom's macroglobulinaemia. Penicilliosis marneffei should be considered as a potential complication in patients with markedly impaired cell-mediated immunity who have travelled to or resided in endemic areas. Patients who have undergone therapy with purine nucleoside analogues such as fludarabine and cladribine are also at risk.

Clarithromycin attenuates mastectomy-induced acute inflammatory response

Based on the observation that administration of clarithromycin led to an attenuation of the inflammatory response induced by surgical trauma in a guinea pig model, we investigated the potential beneficial effects of clarithromycin on the local and systemic inflammatory response in patients undergoing mastectomy in an open-label prospective study. During a 16-month period, 54 patients who underwent mastectomy were randomly divided into two groups. In one group, the patients received oral clarithromycin at a dose of 500 mg twice a day, from the day before to 3 days after mastectomy. There was no significant difference in the incidence of antibiotic prophylaxis-related toxicities or postoperative infections between the patients who received clarithromycin and those who did not. Clarithromycin treatment was significantly associated with an attenuation of febrile response, tachycardia, tachypnea, and an increase in monocyte counts (P, <0.0001, <0.01, <0.05, and <0.01, respectively). Clarithromycin also reduced the intensity and duration of postoperative pain (P, <0.05 and <0.005, respectively) and increased the range of motion of the involved shoulder (P < 0.05 for abduction and flexion). We conclude that clarithromycin effectively modulates the acute inflammatory response associated with mastectomy and produces a better clinical outcome.

Intestinal inflammatory pseudotumour with regional lymph node involvement: identification of a new bacterium as the aetiological agent

Inflammatory pseudotumours are the morphological expression of diverse processes such as reactive/reparative, infective, and neoplastic. This paper reports an example of intestinal inflammatory pseudotumour, with identification of a newly characterized bacterium in the lesion. The patient presented with intestinal obstruction. Laparotomy revealed a tumour in the terminal ileum causing stricture, and multiple enlarged regional lymph nodes. Histologically, the tumour and lymph nodes were composed of plump spindle cells disposed in a vague storiform pattern, and associated with lymphocytes and plasma cells. Immunohistochemical studies showed that most of the spindle cells were histiocytes (CD68 positive), prompting a search for a bacterial aetiology, akin to mycobacterial spindle cell pseudotumour. All histochemical stains for micro-organisms were unrewarding. Ultrastructural studies, however, revealed abundant bacteria within the spindle histiocytes. Polymerase chain reaction, using conserved oligonucleotide primers complementary to the 16S rRNA genes of eubacteria, was employed to amplify 16S rRNA gene fragments directly from the involved lymph node tissue. Phylogenetic analysis of the amplified DNA sequences revealed an organism with 99% sequence conformity to Pseudomonas veronii, a bacterium which has hitherto not been implicated in human infection. The importance of searching for an infective agent in inflammatory pseudotumour in the appropriate setting is re-emphasized.

Identification of Mycobacterium neoaurum isolated from a neutropenic patient with catheter-related bacteremia by 16S rRNA sequencing

A rapidly growing pigmented mycobacterial strain with an ambiguous biochemical profile was isolated from the blood culture taken through the Hickman catheter of a 9-year-old girl with acute lymphoblastic leukemia. Whole-cell fatty acid analysis showed that the best match profile was that of Mycobacterium aurum, but the similarity index was only 0.217, meaning that there were no good matches between the isolate and the organisms in the database of the Microbial Identification System. The 16S rRNA gene of the mycobacterial strain was amplified, agarose gel purified, and sequenced. There were 44 base differences between the gene sequence of the isolate and that of M. aurum but only one base difference between the sequence of the isolate and that of Mycobacterium neoaurum, showing that the isolate was indeed a strain of M. neoaurum by using this "gold standard." This represents the first case of M. neoaurum infection documented by 16S rRNA sequencing.

Leukocytoclastic vasculitis complicating Klebsiella pneumoniae bacteremia

A 79-year old woman, with a history of hypertension, presented with clinical features of congestive heart failure, fever, a purpuric rash, and left lower quadrant abdominal tenderness. Contrast computed tomography scan of the abdomen showed features of acute diverticulitis, and blood culture was subsequently positive for Klebsiella pneumoniae. Histological examination of a biopsy of the rash confirmed a diagnosis of leukocytoclastic vasculitis (LCV). The bacteremia responded to intravenous amoxycillin/clavulanic acid and gentamicin and the rash subsided. This case represents the first case of LCV complicating K. pneumoniae bacteremia in the English literature. The English literature on bacteria-associated LCV is reviewed. Taking aside organisms such as Rickettsia that cause endothelial invasion, the associated bacterial species tends to be subacute or chronic pathogens e.g. Mycoplasma pneumoniae, Mycobacterium tuberculosis, and Yersinia enterocolitica; or the disease process is of a subacute or chronic nature e.g. endocarditis, bronchiectesis, and cystic fibrosis, leading to prolonged exposure to pathogens that apparently cause acute pyogenic infections, such as K. pneumoniae.

Identification by 16S ribosomal RNA gene sequencing of an Enterobacteriaceae species from a bone marrow transplant recipient

AIMS

To ascertain the clinical relevance of a strain of Enterobacteriaceae isolated from the stool of a bone marrow transplant recipient with diarrhoea. The isolate could not be identified to the genus level by conventional phenotypic methods and required 16S ribosomal RNA (rRNA) gene sequencing for full identification.

METHODS

The isolate was investigated phenotypically by standard biochemical methods using conventional biochemical tests and two commercially available systems, the Vitek (GNI+) and API (20E) systems. Genotypically, the 16S bacterial rRNA gene 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 database by multiple sequence alignment.

RESULTS

Conventional biochemical tests did not reveal a pattern resembling any known member of the Enterobacteriaceae family. The isolate was identified as Salmonella arizonae (73%) and Escherichia coli (76%) by the Vitek (GNI+) and API (20E) systems, respectively. 16S rRNA sequencing showed that there was only one base difference between the isolate and E coli K-12, but 48 and 47 base differences between the isolate and S typhimurium (NCTC 8391) and S typhi (St111), respectively, showing that it was an E coli strain. The patient did not require any specific treatment and the diarrhoea subsided spontaneously.

CONCLUSIONS

16S rRNA gene sequencing was useful in ascertaining the clinical relevance of the strain of Enterobacteriaceae isolated from the stool of the bone marrow transplant recipient with diarrhoea.

Enhancement by ampicillin of antibody responses induced by a protein antigen and a DNA vaccine carried by live-attenuated Salmonella enterica serovar Typhi

Live-attenuated Salmonella species are effective carriers of microbial antigens and DNA vaccines. In a mouse model, the immunoglobulin M (IgM) and total antibody levels directed toward the lipopolysaccharide of Salmonella enterica serovar Typhi were significantly enhanced at day 21 after oral immunization with live-attenuated serovar Typhi (strain Ty21a) when ampicillin was concomitantly administered (P < 0.05 and P < 0.005, respectively). The heat-killed Ty21a-stimulated lymphocyte proliferation indices for the ampicillin group at day 21 were significantly higher than those for the normal saline (NS) group (P < 0.005, P < 0.001, and P < 0.01) for all three doses of antigen (10(4), 10(5), and 10(6) heat-killed Ty21a per well, respectively). The 50% lethal doses for mice from the ampicillin and NS groups immunized with Ty21a with pBR322 after wild-type serovar Typhi challenge on day 24 were 3.4 x 10(7) and 5.0 x 10(6) CFU, respectively. The fecal bacterial counts for the ampicillin group at days 1, 3, and 5 were significantly lower than those for the NS group (P < 0.01, P < 0.01, and P < 0.05, respectively), and there was a trend toward recovery of Ty21a in a larger number of mice from the ampicillin group than from the NS group. Furthermore, the IgG2a levels directed toward tetanus toxoid were significantly enhanced at days 7 and 21 after oral immunization with Ty21a that carried the fragment c of tetanus toxoid when ampicillin was concomitantly administered (P < 0.05 and P < 0.005, respectively), and the IgM and total hepatitis B surface antibody levels were significantly enhanced at days 7 (P < 0.005 and P < 0.05, respectively) and 21 (P < 0.01 and P < 0.05, respectively) after oral immunization with Ty21a that carried the DNA vaccine that encodes hepatitis B surface antigen when ampicillin was concomitantly administered. The present observation may improve the efficacy of the protein antigens and DNA vaccines carried in live-attenuated bacteria, and further experiments should be carried out to determine the best antibiotics and dosage regimen to be used, as well as the best carrier system for individual protein antigens and DNA vaccines.

Clarithromycin attenuates cyclophosphamide-induced mucositis in mice

No universally recognized agent is available for prophylaxis or therapy of mucositis induced by chemotherapy or chemo-radiotherapy. The effect of clarithromycin on the severity of mucositis induced by cyclophosphamide was investigated using a mouse model. Four cross-sections of small intestine (levels A, B, C, and D) were taken at equivalent intervals at day 5 after cyclophosphamide (400 mg kg(-1)) administration. The sections were stained with haematoxylin and eosin, and were graded for the degree of mucositis histologically. At section level B, the number of mice with no mucositis (grade 0) in the clarithromycin group was significantly greater than that in the ceftriaxone group (P<0.05). At levels B and C, the number of mice with no mucositis (grade 0) in the clarithromycin group was significantly greater than that in the normal saline (NS) group (P<0.05). At level C, the number of mice with grade 2 mucositis in the ceftriaxone group was significantly greater than that in the NS group (P<0.05). When the number of sections at all levels were analyzed together, the number of mice with no mucositis (grade 0) in the clarithromycin group was significantly greater than that in the ceftriaxone and NS groups (P<0.05). The present observation suggests that clarithromycin and ceftriaxone attenuates and aggravates cyclophosphamide-induced mucositis. It prompts clinical trials in bone marrow transplant (BMT) recipients receiving cyclophosphamide for conditioning, and reconsideration in the use of ceftriaxone in the treatment of neutropenic fever in BMT recipients.

Enhancement of humoral and protective immune response induced by live-attenuated Salmonella typhi by ampicillin

Efficacy of live-attenuated Salmonella vaccines delivered by the mucosal route is limited by the dose and interference from mucosal flora of the alimentary tract. In a mouse model, the total antibody response towards lipopolysaccharide of S. typhi was significantly enhanced at day 21 post-immunization with live-attenuated S. typhi (Ty21a) when ampicillin was concomitantly administered (p<0.005), and the lethal dose 50 of mice in the ampicillin and control groups immunized with Ty21a after wild-type S. typhi challenge on day 24 was 4x10(7) and 1x10(7), respectively. The faecal bacterial counts of the ampicillin group at days 1 and 3 were significantly lower than those of the control group (p<0.01 and <0.05). On day 1, the number of mice with > or =10 Ty21a colonies isolated from the spleen was significantly higher in the ampicillin group than the control group (p<0.05). Furthermore, on the same day, Ty21a was isolated from the faeces of three mice from the ampicillin group, but only one from the control group. We conclude that ampicillin may have enhanced the humoral and protective immune responses by giving the Ty21a a selective advantage over the normal bacterial flora. This concept of antibiotic enhancement of immunization could have important implications for other live-attenuated vaccines, as well as the delivery of microbial antigens and DNA vaccines by live-attenuated Salmonella carriers.

Bacteremia due to Staphylococcus aureus with reduced susceptibility to vancomycin

Four cases of bacteremia caused by Staphylococcus aureus with heteroresistance to vancomycin (hetero-VRSA) were described. In at least two of these four mortalities, the cause of death was temporally related to the hetero-VRSA bacteremia. The vancomycin and teicoplanin MICs of the resistant subpopulations of these four hetero-VRSA were 8 and 24 microg/ml, respectively. All isolates were producers of beta-lactamase, produced penicillin-binding protein PBP2a, and possessed the mecA gene accounting for methicillin resistance. Thickening of the peptidoglycan cell wall was observed by electron microscopy. When ampicillin was combined with vancomycin, in vitro synergism was detected using the checkerboard titration method (epsilonFIC = 0.13). The use of vancomycin plus ampicillin-sulbactam could be a viable option in treating severe hetero-VRSA infection in view of the higher affinity of ampicillin toward PBP2a.

Cellulitis complicating lymphoedema

In ten hospitalised patients with cellulitis complicating lymphoedema encountered over a 3-year period (1996-1998), the underlying diseases were carcinoma of the cervix (n = 4), uterus (n = 1), vagina (n = 1), breast (n=2) and nasopharynx (n= 1), and retroperitoneal squamous cell carcinoma (n = 1). Three of the ten patients had positive blood cultures, compared to none of the 20 age-matched, sex-matched controls hospitalised for cellulitis without lymphoedema. The mean duration of fever, tachycardia and cellulitis was significantly longer in patients with lymphoedema than in those without (P<0.05, P<0.05, and P<0.005 respectively). Early treatment initiated by patients themselves may help stop bacterial replication in the initial stages and minimise further damage to the lymphatic system.

Antibiotics modulate vaccine-induced humoral immune response

The effects of antibiotics on the antigen-specific humoral immune response are not known. Macrolides, tetracyclines, and beta-lactams are commonly prescribed antibiotics. The first two are known to have immunomodulatory activities. The effects of clarithromycin, doxycycline, and ampicillin on the primary and secondary antibody responses to tetanus toxoid, a pneumococcal polysaccharide vaccine, a hepatitis B virus surface antigen (HBsAg) vaccine, and live attenuated Salmonella typhi (Ty21a) were investigated using a mouse model. For the mice receiving the tetanus toxoid, the immunoglobulin M (IgM) level of the clarithromycin group at day 7 was significantly lower than the corresponding antibody level of the normal saline (NS) group. For the mice receiving the pneumococcal polysaccharide vaccine, the total antibody and IgM levels of the clarithromycin group and the IgM level of the doxycycline group at day 7 were significantly lower than the corresponding antibody levels of the ampicillin and NS groups. For the mice receiving the HBsAg vaccine, the IgM level of the doxycycline group at day 7 was significantly lower than the corresponding antibody levels of the clarithromycin and NS groups, while the IgM level of the clarithromycin group at day 28 was significantly lower than the corresponding antibody levels of the doxycycline, ampicillin, and NS groups. For the mice receiving all three vaccines, there were no statistically significant differences between any of the antibody levels of the ampicillin group and the corresponding antibody levels of the NS group. For the mice receiving Ty21a, the total antibody levels of the ampicillin group at days 7 and 21 were significantly higher than the corresponding antibody levels of the NS group. Moreover, the IgM levels of the clarithromycin, doxycycline, and ampicillin groups at days 7 and 21 were significantly higher than the corresponding antibody levels of the NS group. Furthermore, the total antibody level of the ampicillin group at day 21 was significantly higher than the corresponding antibody level of the doxycycline group. For all four vaccines, there were no statistically significant differences among the serum levels of interleukin-10 and gamma interferon for the mice treated with the various antibiotics. We conclude that clarithromycin and doxycycline, but not ampicillin, suppress the antibody responses of mice to T-cell-dependent and T-cell-independent antigens, whereas all three antibiotics enhance the antibody response to live attenuated mucosal bacterial vaccines.

Bacteremia caused by staphylococci with inducible vancomycin heteroresistance

The clinical significance of bacteremia due to vancomycin-heteroresistant staphylococci and a rapid laboratory screening method were examined; 203 strains of staphylococci isolated from patients with clinically significant bacteremia were screened by the disk-agar method with use of vancomycin-salt agar to demonstrate satellitism around an aztreonam disk as well as by conventional population screening. Eighteen isolates (three Staphylococcus aureus and 15 coagulase-negative staphylococci) were shown to be heteroresistant to vancomycin. A case-control clinical study showed that the interval between admission and bacteremia, admission to the intensive care unit, prior use of vancomycin and/or beta-lactams, and isolation of methicillin-resistant staphylococci were significantly more common among patients with bacteremia due to staphylococci with heteroresistance to vancomycin; these patients had an overall mortality of 44.4%. The use of vancomycin and admission to the intensive care unit were independently significant risk factors on multivariate analysis. Vancomycin heteroresistance is inducible by salt and beta-lactams. Indiscriminate sequential use of beta-lactams and glycopeptides may facilitate the emergence of glycopeptide resistance.

Hot spot mutations in morphological transforming region II (ORF 79) of cytomegalovirus strains causing disease from bone marrow transplant recipients

Nested polymerase chain reaction (PCR) amplifying the morphological transforming region II (mtrII) of cytomegalovirus (CMV) has been shown to be useful in the detection of CMV DNA in bone marrow transplant (BMT) recipients. However, there has never been any report on mutation hot spots and subtypes of this open reading frame. Using primers derived from sequences upstream and downstream of mtrII (ORF 79), CMV DNA from peripheral blood leukocytes (PBL) and conventional CMV culture of 16 BMT recipients were amplified by PCR, cloned into pUC118, and sequenced. The amino acid sequences were predicted using the standard triplet code. The DNA sequences obtained from direct amplification of CMV in PBL obtained from the 16 patients were 100% identical to the corresponding ones obtained by amplification of CMV DNA extracted from conventional CMV culture. Within mtrII (ORF 79), hot spot single base mutations were observed at positions +40 (G-->A), +123 (A-->G), +213 (T-->C), and +219 (T-->C). However, because of third base degeneracy, only amino acid 14 was changed from valine to isoleucine in the predicted protein of 13 patients. This corresponded to the hot spot mutation at position +40 (GTC-->ATC), while the rest were silent mutations. An insertion of 3 bases (ACG) was observed in the CMV DNA of 10 patients at positions +91 to +93, leading to a threonine insertion at amino acid 31 in these patients. For patient no. 147 there was a 65 bp deletion in the CMV DNA amplified later in the course of BMT as compared with that early in the course. This gave rise to a frame shift mutation and a change of more than 70% in the predicted amino acid sequence of the protein.

Susceptibility testing of Clostridium difficile against metronidazole and vancomycin by disk diffusion and Etest

A prospective study on the susceptibility of Clostridium difficile to metronidazole and vancomycin using the Etest and disk diffusion test was performed over a 6-month period. One hundred strains were tested; one strain was highly resistant to metronidazole (MIC = 64 micrograms/mL). The zone size of inhibition by the disk diffusion test correlated with the MIC as determined by the Etest (regression coefficient = -0.043 for metronidazole and -0.044 for vancomycin, p < 0.001 for both antibiotics). However, the correlation coefficient was low for both metronidazole (r = 0.574) and vancomycin (r = 0.473); hence the zone of inhibition by disk diffusion test could not predict the MIC satisfactorily. Metronidazole is still the first-line antibiotic for the treatment of C. difficile-associated diarrhea because the incidence of metronidazole resistant strains remains very low. However, the efficacy of metronidazole in the treatment of infections attributable to isolates with high-level metronidazole resistance may be compromised because the fecal concentration of metronidazole is relatively low when compared with the MIC values of the less susceptible strains. Oral vancomycin is the drug of choice under such circumstances, as its fecal concentration is much higher than that of metronidazole.

Acinetobacter bacteremia in Hong Kong: prospective study and review

The epidemiological characteristics of 18 patients with acinetobacter bacteremia were analyzed. Patients (mean age, 55.5 years) developed bacteremia after an average of 14.1 days of hospitalization. Fifteen of 16 patients survived bacteremia caused by Acinetobacter baumannii. Cultures of blood from the remaining two patients yielded Acinetobacter lwoffii. Most patients (78%) resided in the general ward, while four patients (22%) were under intensive care. Genotyping by arbitrarily primed polymerase chain reaction analysis and the temporal sequence of isolation were more useful than phenotyping by antimicrobial susceptibility in the determination of the source of bacteremia, and the intravascular catheter was the leading infection source (39% of cases). The possibility of an association of glucose with the pathogenesis of acinetobacter infection was raised.

Clarithromycin attenuates the inflammatory response induced by surgical trauma in a guinea pig model

The effect of clarithromycin on the systemic and local inflammatory responses after surgical trauma was investigated using a guinea pig model. There was no statistically significant difference in the body temperature and respiratory rate of the guinea pigs between the clarithromycin and control groups, although there was a trend towards a lower temperature in the first 36 h after the operation, and a trend towards a lower respiratory rate on day 1 and day 2 (P=0.07 and 0.18, respectively) in the clarithromycin group. The total leukocyte count of both groups of animals increased from day -1 to day 4, and the increase was more marked in the control group (P=0.06 on day 1). The neutrophil and monocyte counts of the two groups of animals also increased after the operation. The neutrophil count of the control group was significantly higher than the clarithromycin group on day 1 and 2 (P<0.05 and 0.01, respectively), and the monocyte count of the control group was significantly higher than the clarithromycin group on day 1 (P<0.005). Moreover, the platelet count of the animals also increased after the operation, and the count in the control group was significantly higher than the clarithromycin group on day 1, 2 and 4 (P<0.05, 0.005 and 0.005, respectively). There was no difference between the haemoglobin concentration, lymphocyte count, eosinophil count and basophil count between the two groups of animals. The number of animals with wound discharge was lower in the clarithromycin group than the control group throughout the post-operative period, but the difference was not statistically significant. None of the animals developed signs of wound infection. The present observation suggests that clarithromycin suppressed both the systemic and local inflammatory response after surgical trauma, and it prompts further animal experiments for delineation of the mechanism of action, as well as clinical trials in major surgical procedures.

Risk factors for pulmonary tuberculosis in bone marrow transplant recipients

Little is known about the profile of infection with Mycobacterium tuberculosis in bone marrow transplant (BMT) recipients. Of five BMT series with a total of more than 5,000 patients, only 10 cases of M. tuberculosis infection were described, with an overall incidence of 0.19%. We have conducted a prospective evaluation of 183 consecutive BMT recipients, and 10 patients were found to develop pulmonary tuberculosis post-BMT, yielding an incidence of 5.5%. We described the clinical features of these 10 patients, and analyzed the risk factors for development of tuberculosis using age- and sex-matched case control subjects who did not develop the disease. The median age of the 10 patients who developed tuberculosis was 29 yr (range, 17 to 40 yr). The median time for onset of symptoms was 150 d (range, 23 to 550 d), mainly presenting with fever and cough, with infiltrates on chest radiograph. Respiratory tract specimens, mostly sputum, yielded positive smears for acid-fast bacilli in three and positive M. tuberculosis culture in eight, whereas lung tissue histology was the first diagnostic test in two patients. Treatment with standard antituberculosis drugs for a longer duration was highly effective, with no excessive side effects. Risk factors identified for development of tuberculosis included allogeneic BMT (p < 0.05, relative risk [RR] = 23.7), total body irradiation (p < 0. 05, RR = 4.9), and chronic graft-versus-host disease (GVHD) (p < 0. 05, RR = 3.6). It is postulated that chronic GVHD predisposed to development of tuberculosis mainly via disruption of host reconstitution of immune defenses against M. tuberculosis.

Clonorchiasis in bone marrow transplant recipients

Among 380 bone marrow transplant (BMT) recipients, five cases (1.3%) of clonorchiasis were observed from 1991 to 1996. Clonorchis sinensis infection was evident in the results of stool examinations performed for screening purposes 7 days before bone marrow transplantation. Salmonella species were isolated concomitantly from the stools of two of the five patients. None of the patients had symptoms due to clonorchiasis. Ultrasonography did not show dilated hepatobiliary ducts, stones, or periportal fibrosis. Fatty liver changes were detected in one patient. All five patients received praziquantel (25 mg/kg po t.i.d. for 1 day) before bone marrow transplantation. Only two patients who underwent allogeneic transplantation had mild venoocclusive disease of the liver with transient hyperbilirubinemia and mildly elevated liver enzyme levels, whereas hyperbilirubinemia or elevated serum alanine aminotransferase levels, related to conditioning toxicity, occurred in two other patients. After treatment with praziquantel, stool examination for all five patients were negative for C. sinensis ova. In addition, Salmonella species were not detected after ciprofloxacin prophylaxis. All five patients survived for > 300 days. Given the availability of effective therapy and in the absence of excessive complications, clonorchiasis is not a contraindication to bone marrow transplantation.

Unique risk factors for bacteraemia in allogeneic bone marrow transplant recipients before and after engraftment

A study of the risk factors associated with bacteraemia in 191 allogeneic bone marrow transplant (BMT) recipients (1991-1996) was performed. In contrast to risk factors commonly cited for cancer chemotherapy, mucositis, degree of conditioning toxicity of the gut and lungs, duration of neutropenia, and severity of neutropenia and monocytopenia were not associated with bacteraemia in the pre-engraftment period, during which the only significant risk factor was late stage underlying disease (P < 0.05). After engraftment, Hickman catheter infection, and severe acute and chronic graft-versus-host disease (GVHD) were found to be independently associated with bacteraemia by multivariate analysis (P < 0.001, <0.05 and <0.05, respectively). This might be explained by intense antimicrobial prophylaxis, early empirical treatment, and non-routine use of haemopoietic growth factors. No significant difference in mortality was detected between bacteraemic and non-bacteraemic patients in both periods. Allogeneic BMT recipients are therefore a group of patients distinct from other cancer patients receiving chemotherapy at risk of developing bacteraemia. The study findings prompt consideration of a management protocol incorporating early and routine use of haemopoietic growth factors before engraftment in high-risk patients with late stage underlying malignancies, routine antimicrobial prophylaxis for acute GVHD with intense immunosuppression, and intravenous immunoglobulin therapy for chronic GVHD. Further cost-benefit analyses are warranted.

Serological diagnosis of nasopharyngeal carcinoma by enzyme linked immunosorbent assay: optimization, standardization and diagnostic criteria

OBJECTIVES

To produce an enzyme linked immunosorbent assay (ELISA) to detect antibodies against Epstein Barr virus (EBV) specified nuclear antigen 1 (EBNA 1) and the 18 kD EBV matrix protein, and to determine and optimize its sensitivity and specificity for the diagnosis of nasopharyngeal carcinoma (NPC).

METHODS

We used a combination of highly purified glutathione transferase fusion proteins of the 40 kD carboxy domain of EBNA1 and the 18 kD EBV matrix protein for coating ELISA plates. In three separate studies, we tested for IgA antibodies in serum specimens from 28 EBV seronegative donors, 284 EBV seropositive donors and 160 newly diagnosed NPC patients. By comparing the sensitivity and specificity of diagnosis obtained for different cutoff values, we derived several quantitative parameters to evaluate assay performance, establish objective diagnostic criteria which optimize the intrinsic diagnostic capability of the assay and assess the significance of individual test results, respectively. Optimum cutoff optical density (OD) is defined as the cutoff OD where sensitivity of the assay equals its specificity, and resolution of the assay is indicated by the value of sensitivity (or specificity) determined at the optimum cutoff OD. Diagnosis of NPC was achieved by setting a cutoff zone at +/- 20% of this value.

RESULTS

All the EBV seronegative donors tested were not reactive, and most of the EBV seropositive donors were weakly reactive, while the majority of NPC patients were moderately or strongly reactive. While the assay was thus shown to be specific for EBV, there was an overlap in the level of these serum antibodies between few individuals of the two latter groups. It was shown that the assay performed equally well in two separate studies conducted under different testing conditions and using different collections of sera in that assay resolution determined on these occasions were 86% and 87% respectively. Diagnosis of NPC can be achieved at the same expected sensitivity of 89% and 83% determined at the lower and upper limits of the cutoff zones, with the corresponding values of specificity being 78% and 91%. It was further shown in the third study that resolution of the assay can be increased to 90% using an assay produced with a higher concentration of the same antigens, and that diagnosis of NPC can be achieved at a higher sensitivity ranging between 86% and 95% at a corresponding specificity of 93% and 86%.

CONCLUSIONS

After optimization and standardization, the ELISA can achieve a sensitivity ranging from 86% to 95%, with corresponding specificities of 93% and 86% respectively for the diagnosis of NPC.

Identification of acinetobacters on blood agar in presence of D-glucose by unique browning effect

A positive phenotypic characteristic of glucose-oxidizing acinetobacters was demonstrated with blood agar containing D-glucose. Glucose-oxidizing Acinetobacter baumannii, Acinetobacter genospecies 3, Acinetobacter lwoffii, and Acinetobacter genospecies 13 sensu Tjernberg and Ursing caused a unique brown discoloration of media supplemented with 5% blood (of horse, sheep, or human origin) and an aldose sugar (0.22 M D-glucose, D-galactose, D-mannose, D-xylose, or lactose). The browning effect was not observed when a ketose sugar (D-fructose or sucrose) was substituted for the aldose sugar or under high osmolarity in the presence of mannitol, glycerol, or sodium chloride. Other gram-negative nonfermenters (non-glucose-oxidizing acinetobacters, Pseudomonas aeruginosa, other Pseudomonas spp., Stenotrophomonas maltophilia, Flavobacterium spp., and Moraxella spp.) did not cause similar discoloration. This novel browning effect may serve as an alternative trait for identifying glucose-oxidizing acinetobacters.

Inpatient emergencies encountered by an infectious disease consultative service

The spectrum of infectious disease (ID) emergencies in hospitalized patients was assessed in a prospective study of 3,626 inpatient ID consultations in a 1,350-bed teaching hospital. ID emergencies, defined by a need or anticipated need for advanced life support or by irreversible organ damage leading to permanent functional loss, were encountered in 175 patients. Infections of the central nervous system (26.3%), cardiovascular system (14.9%), alimentary system (13.1%), and lower respiratory tract (7.4%) and adverse reactions to antimicrobial agents (7.4%) were most common. In 18.9% of the cases, the referring clinicians were unaware of the emergency at the time of referral. Drug reactions (46.1%), severe alimentary and peritoneal infections (32.0%), upper respiratory tract infections (28.6%), and skin and soft-tissue infections (27.3%) were most frequently missed. The emergency ID conditions were not recognized because they had an atypical presentation (51.5%), were not commonly seen in the referring specialty (24.2%), were due to rare organisms (15.2%), or had unusual anatomical sites of involvement (9.1%). A close liaison between clinicians and the ID team is crucial for recognition of ID emergencies at their early stages so that appropriate investigations and management can be instituted expediently, before the occurrence of irreversible damage.

Clinical significance of alimentary tract microbes in bone marrow transplant recipients

A prospective study on the microbes isolated from the alimentary tract in 120 bone marrow transplant (BMT) recipients (1991-1993) was undertaken to define the spectrum of organisms isolated under antimicrobial prophylaxis, their temporal sequence of emergence, and the associated morbidity and mortality. Clostridium difficile (n = 20), isolated in the pre-engraftment and early post-engraftment periods (day 2-45 post-BMT), was the most common microbe recovered from stool of patients with diarrhea. In contrast to previous reports, no significant difference in mortality was observed between patients with and without C. difficile isolated in stool. Two patients had neutropenic ileocecitis with concomitant bacteremia due to Escherichia coli and Klebsiella pneumoniae. One patient was found to have astrovirus gastroenteritis (day 7), and Giardia lamblia was recovered from the stool of another (day -7). Heavy growth of Staphylococcus aureus from direct smear-positive specimens was found from the upper airway of two patients with severe mucositis and complete dysphagia (day 12 and 23). Salmonella spp. of groups B and E were found in the stool of five asymptomatic patients at the time of conditioning. No specific organisms was recovered from the endoscopic brushing of two patients with lower end esophagitis, three patients with upper gastrointestinal bleeding, and three patients with perirectal cellulitis. During the post-engraftment period, five patients had documented cytomegalovirus gastroenterocolitis (days 34-97), one had Mycobacterium chelonae colitis (day 70), and another had nodular gastritis due to Acremonium falciforme (day 270). Overall, only 28% of patients with alimentary tract symptoms/syndrome had specific pathogens isolated from clinical specimens. Differentiation of the causation of alimentary tract symptoms was often difficult because noninfectious complications such as conditioning toxicity, graft-versus-host disease, and its treatment often caused alimentary tract symptoms in addition to predisposed BMT patient to infection. The reluctance of obtaining tissue biopsy for ascertaining the importance of those potential alimentary tract pathogens often dictate the use of empirical treatment.

Distinct genotypic distributions of cytomegalovirus (CMV) envelope glycoprotein in bone marrow and renal transplant recipients with CMV disease

A prospective study of the spectrum of glycoprotein B (gB) and glycoprotein H (gH) genotypes of cytomegalovirus (CMV) was conducted with five categories of patients: viremic bone marrow-transplant (BMT) recipients who developed CMV disease after BMT (n = 22), viremic BMT recipients without CMV disease (n = 11), viremic renal-transplant recipients who developed CMV disease after transplantation (n = 14), viremic renal-transplant recipients without CMV disease (n = 13), and premature babies with asymptomatic congenital CMV infections (n = 13). Genotypic stability was observed because the gB and gH genotypes of multiple isolates obtained from a single patient were identical. The distribution of gH genotypes in patients of all groups studied were similar. However, there was a unique distribution of the gB genotype in the first category of patients, i.e., BMT recipients with CMV disease, which was distinct from those of all other categories (P < 0.05). CMV isolates from 54% of BMT recipients with CMV disease exhibited gB type 2, while isolates from 46, 50, 69, and 77% of the BMT recipients without CMV disease, renal-transplant recipients with and those without CMV disease, and premature babies with congenital CMV infection, respectively, were of gB type 1. An analysis of the clinical characteristics of BMT recipients with CMV disease indicated that all underwent either an allogeneic or matched, unrelated donor transplant, and half had severe acute graft-versus-host disease (grades 2 to 4). The statistically significant genotypic difference between CMV isolates from BMT recipients with and without CMV disease was not observed between isolates from renal-transplant recipients with and without CMV disease. We speculate that differences in pathogenesis in different patient groups might account for these observations. These findings would also facilitate decision making about the choice of recombinant CMV glycoprotein vaccine required to immunize transplant donors and the subsequent adoptive transfer of immunity to BMT recipients. When the source of CMV DNA required for genotyping was investigated among renal-transplant recipients, direct use of peripheral blood leukocytes was 95% effective compared to the effectiveness of cells obtained from conventional culture of peripheral blood specimens.

Stage-specific manifestation of mold infections in bone marrow transplant recipients: risk factors and clinical significance of positive concentrated smears

Potassium hydroxide-concentrated smears, prepared from sedimented remains of clinical specimens, were used to distinguish between mold infection and exogenous contamination in fungal culture-positive specimens. This method was applied in the study of 3,857 clinical specimens from 230 bone marrow transplant recipients who were followed up prospectively for infectious complications. Concentrated smears of only 86 (from 21 infected patients) of 149 fungal culture-positive specimens were positive for hyphae; 82 of the strains were Aspergillus species. Concentrated smears of the remaining 63 fungal culture-positive specimens were negative; the strains identified by culture were considered as exogenous contaminants (87% of which were Penicillium species). A stage-specific manifestation of mold infection was observed: 67% of mold infections occurred during acute graft-vs.-host disease (GVHD) a median of 47 days after transplantation, whereas 9% of mold infections occurred as rapidly fatal invasive disease before engraftment. Overall, of the 21 patients with mold infection, 17 (81%) had invasive mold disease, and four (19%) had mold colonization of airways secondary to chronic GVHD after day 100. The significant risk factors for mold infection were total-body irradiation and grade 2-4 acute GVHD. Because of our high mortality rate (82%), the consideration of antimold prophylaxis for such patients may be warranted.