Serological responses in patients with severe acute respiratory syndrome coronavirus infection and cross-reactivity with human coronaviruses 229E, OC43, and NL63

The serological response profile of severe acute respiratory syndrome (SARS) coronavirus (CoV) infection was defined by neutralization tests and subclass-specific immunofluorescent (IF) tests using serial sera from 20 patients. SARS CoV total immunoglobulin (Ig) (IgG, IgA, and IgM [IgGAM]) was the first antibody to be detectable. There was no difference in time to seroconversion between the patients who survived (n = 14) and those who died (n = 6). Although SARS CoV IgM was still detectable by IF tests with 8 of 11 patients at 7 months postinfection, the geometric mean titers dropped from 282 at 1 month postinfection to 19 at 7 months (P = 0.001). In contrast, neutralizing antibody and SARS CoV IgGAM and IgG antibody titers remained stable over this period. The SARS CoV antibody response was sometimes associated with an increase in preexisting IF IgG antibody titers for human coronaviruses OC43, 229E, and NL63. There was no change in IF IgG titer for virus capsid antigen from the herpesvirus that was used as an unrelated control, Epstein-Barr virus. In contrast, patients who had OC43 infections, and probably also 229E infections, without prior exposure to SARS CoV had increases of antibodies specific for the infecting virus but not for SARS CoV. There is a need for awareness of cross-reactive antibody responses between coronaviruses when interpreting IF serology.

Escherichia coli Producing CTX-M β-Lactamases in Food Animals in Hong Kong

A study was conducted to evaluate the occurrence of extended-spectrum beta-lactamases (ESBLs)-producing Escherichia coli from fecal samples of healthy food animals in Hong Kong. Rectal or cloacal swabs were obtained from cattle, pigs, chicken, ducks, geese, and pigeons in slaughterhouses or wholesale markets over a 5- month period in 2002. Antibiotic-containing medium was used for selective isolation of potentially ESBL-producing E. coli. Of 734 samples analyzed, six (2%) from pigs, three (3.1%) from cattle, and one (3%) from pigeons had E. coli strains with the ESBL phenotype. The ESBL content for the 10 isolates include CTXM- 3 (n = 4), CTX-M-13 (n = 3), CTX-M-14 (n = 2), and CTX-M-24 (n = 1). In five isolates, the bla (CTX-M) gene was encoded on transferable plasmids (60 or 90 kb), and the gene was found to transfer to E. coli (J53 or JP995) with frequencies of 10(7) to 10(3) per donor cells. The ten isolates had five distinct pulsotypes with some clonal spread. However, the isolates from the different kinds of animals were not clonally related. These findings imply that bacteria of animal origins may serve as reservoirs of some ESBL genes.

Globicatella bacteraemia identified by 16S ribosomal RNA gene sequencing

BACKGROUND

Globicatella are streptococcus-like organisms that have been rarely isolated from clinical specimens. Their epidemiology and clinical significance remain largely unknown.

AIMS

To describe two cases of Globicatella bacteraemia identified by 16S ribosomal RNA (rRNA) gene sequencing.

METHODS

Two unidentified streptococcus-like bacteria isolated from blood cultures of patients were subject to 16S rRNA gene sequencing.

RESULTS

Two cases of Globicatella bacteraemia were identified by 16S rRNA gene sequencing. In the first case, a gram positive coccus was isolated from the blood culture of an 80 year old woman with diabetes mellitus and nosocomial sepsis, who died the day after developing the bacteraemia. The bacterium was unidentified by conventional phenotypic tests, the Vitek (gram positive identification) and the ATB expression (ID32 Strep) systems. In the second case, a similar bacterium was isolated from the blood culture of a 92 year old woman with polymicrobial acute pyelonephritis complicated by septic shock, who subsequently recovered after antibiotic treatment. 16S rRNA gene sequencing of the two isolates showed 0.5% nucleotide difference from that of G. sulfidifaciens and 0.7% nucleotide difference from that of G. sanguinis, indicating that they were Globicatella species.

CONCLUSIONS

Because Globicatella is rarely encountered in clinical microbiology laboratories, it may have been overlooked or misidentified in these cases. 16S rRNA gene sequencing is a useful tool to better characterise the epidemiology and clinical significance of Globicatella.

Molecular characterization of isoniazid resistance in Mycobacterium tuberculosis: identification of a novel mutation in inhA

Multiplex allele-specific PCRs detecting katG codon 315 and mabA (bp -15) mutations could specifically identify 77.5% of isoniazid-resistant Mycobacterium tuberculosis strains in the South China region. One clinical isolate harboring InhA Ile194Thr was characterized to show strong association with isoniazid resistance in Mycobacterium tuberculosis.

Polyoma BK virus and haemorrhagic cystitis in haematopoietic stem cell transplantation: a changing paradigm

Haemorrhagic cystitis (HC) is a distinct clinical disorder of multiple aetiologies. It is characterized by painful haematuria due to haemorrhagic inflammation of the urinary bladder mucosa. In allogeneic haematopoietic stem cell transplantation (HSCT), HC occurring before engraftment is mostly transient and self-limiting, whereas that after engraftment is severe and sometimes life-threatening. Pre- and post-engraftment HC represent distinct disorders with different aetiologies and treatment implications. Recent data suggest that reactivation of the polyoma BK virus (BKV) plays a pivotal role in post-engraftment HC. Urotoxicity of the conditioning regimen and alloimmune reaction accompanying graft-versus-host disease (GVHD) upon engraftment are also important pathogenetic factors. Based on data from BKV studies, we propose that HC may be divided into three phases. In the first phase, the conditioning regimen damages uroepithelial cells, providing a milieu for BKV replication. In the second phase, unchecked uroepithelial BKV replication leads to BK viruria. In the last phase after engraftment, alloimmunity against BKV-infected uroepithelial cells leads to HC. The quinolone antibiotics suppress BKV replication in vivo and in vitro, suggesting that their prophylactic use may prevent the occurrence of HC.

Clinical utility of genotyping resistance test on determining the mutation patterns in HIV-1 CRF01_AE and subtype B patients receiving antiretroviral therapy in Hong Kong

BACKGROUND

HIV-1 genotypic resistance test (GRT) has been widely used to monitor HIV infection but only few reports revealed the mutation patterns of non-B HIV-1 subtypes.

OBJECTIVE

To evaluate the concordance of GRT and clinical treatment outcomes on different HIV-1 subtypes and monitor the mutation patterns and frequencies.

STUDY DESIGN

Pre- and post-treatment plasma samples from 123 patients (39 treatment naïve and 84 treatment experienced) were tested by ViroSeq HIV-1 Genotyping System followed by analysis using the Stanford HIV database. The mutation patterns and frequencies developed in the pol gene were compared among subtypes.

RESULTS

HIV-1 subtypes among patients in Hong Kong were mainly subtype B and CRF01_AE. Primary mutation was not detected among all pre-treatment samples. For post-treatment samples, primary mutations were only detected in the treatment failure group. The mutation patterns and frequencies were similar between CRF01_AE and subtype B viruses. However, the frequencies of L74V/I and K103N in the reverse transcriptase region were different between CRF01_AE and subtype B viruses. VirtualPhenotype was unable to analyze an in-frame insertion of arginine and isoleucine at protease codon 35 of one CRF01_AE isolate.

CONCLUSIONS

This is the first report to demonstrate the high degree of concordance of longitudinal genotyping data and clinical treatment outcome in patients harboring different HIV-1 subtypes. Our findings shed light to the emergence of resistance mutations and its testing in CRF01_AE, which is relevant to other prevailing places in Asia.

Usefulness of the MicroSeq 500 16S rDNA bacterial identification system for identification of anaerobic Gram positive bacilli isolated from blood cultures

Using full 16S ribosomal RNA (rRNA) gene sequencing as the gold standard, 20 non-duplicating anaerobic Gram positive bacilli isolated from blood cultures were analysed by the MicroSeq 500 16S rDNA bacterial identification system. The MicroSeq system successfully identified 13 of the 20 isolates. Four and three isolates were misidentified at the genus and species level, respectively. Although the MicroSeq 500 16S rDNA bacterial identification system is better than three commercially available identification systems also evaluated, its database needs to be expanded for accurate identification of anaerobic Gram positive bacilli.

Lymphopenia at presentation is associated with increased risk of infections in patients with systemic lupus erythematosus

BACKGROUND

Patients with systemic lupus erythematosus (SLE) frequently suffer from infections, but the predisposing risk factors, as well as the exact frequency and nature of such infections, are not fully understood.

AIM

To describe the frequency, types and risk factors for infections in a group of Chinese patients in the early stage of SLE in Hong Kong.

DESIGN

Retrospective record study.

METHODS

We reviewed the case records of 91 Chinese SLE patients, presenting <12 months after SLE diagnosis. Details of major infections (requiring intravenous antimicrobial therapy, or any confirmed mycobacterial infection) and minor infections were reviewed. Clinical and laboratory features, the systemic lupus erythematosus disease activity index (SLEDAI) at presentation and drug treatment were recorded and analysed.

RESULTS

There were 48 major infections and 62 minor infections during 260 patient-years of follow-up. A lymphocyte count < or =1.0 x 10(9)/l at presentation was independently associated with an increased risk for major infection: hazard ratio 4.7 (95%CI 1.6-13.7), p = 0.005. SLEDAI, use of corticosteroids and immunosuppressive therapy were all not associated with increased risk of infection.

DISCUSSION

Lymphopenia was an important risk factor for major infections in this group of Chinese patients in the early stages of SLE. SLE patients with lymphopenia at presentation should be closely monitored for the development of infective complications.

Molecular diagnostics in tuberculosis

Molecular diagnostics in tuberculosis has enabled rapid detection of Mycobacterium tuberculosis complex in clinical specimens, identification of mycobacterial species, detection of drug resistance, and typing for epidemiological investigation. In the laboratory diagnosis of tuberculosis, the nucleic acid amplification (NAA) test is rapid and specific but not as sensitive as culture of mycobacteria. The primary determinant of successful NAA testing for tuberculosis depends on the shedding of mycobacterial DNA in secretions from caseating granulomas and its dissemination into sterile body fluids or tissue biopsies. In multibacillary diseases with a high mycobacterial load, a positive Ziehl-Neelsen smear with a positive NAA test is diagnostic of active tuberculosis, whereas a positive Ziehl-Neelsen smear with a negative NAA test in the absence of inhibitors would indicate nontuberculous mycobacterial disease. The role of the NAA test is more important in paucibacillary diseases with low mycobacterial loads. The presence of polymerase chain reaction (PCR) inhibitors, however, especially in extrapulmonary specimens, may produce false-negative results. Although this problem can be overcome to some extent by extra extraction steps, the additional processing invariably leads to the loss of mycobacterial DNA. To circumvent this problem, a brief culture augmentation step is carried out before the NAA test is performed, which can enhance the mycobacterial load while concomitantly diluting inhibitors, thereby maintaining the sensitivity of the test without excessively increasing turnaround time.

Human infection with an avian H9N2 influenza A virus in Hong Kong in 2003

Avian H9N2 influenza A virus has caused repeated human infections in Asia since 1998. Here we report that an H9N2 influenza virus infected a 5-year-old child in Hong Kong in 2003. To identify the possible source of the infection, the human isolate and other H9N2 influenza viruses isolated from Hong Kong poultry markets from January to October 2003 were genetically and antigenically characterized. The findings of this study show that the human H9N2 influenza virus, A/Hong Kong/2108/03, is of purely avian origin and is closely related to some viruses circulating in poultry in the markets of Hong Kong. The continued presence of H9N2 influenza viruses in poultry markets in southern China increases the likelihood of avian-to-human interspecies transmission.

Influenza vaccination: options and issues

Currently available vaccines have similar efficacy if they are matched to the most prevalent circulating strains. They also have comparable adverse effect profiles. The choice of a specific preparation of vaccine therefore requires consideration of cost, purity of the vaccine preparation in terms of the amount of egg protein and endotoxin, allergy to different constituents of the vaccine, reactogenicity profiles, as well as the preferred route of administration. Intradermal injection of the vaccine appears to be a viable alternative to the traditional intramuscular administration with the additional benefit of requiring a smaller volume of vaccine. Despite the documented benefits in various community and institutional settings, influenza vaccination has been underutilised by most target groups. A major obstacle to broader coverage of vaccination is the perceived ineffectiveness of the vaccine and the relatively benign nature of the illness in most patients. Uptake of vaccine among target populations, especially health care workers, needs to be improved through a concerted effort between frontline clinicians and health authorities.

Pulmonary artery thrombosis in a patient with severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is an emerging infectious disease with both pulmonary and extra-pulmonary manifestations. Although coagulation abnormalities are common in these patients, clinically overt thromboembolic events are rarely reported. This report describes the first case of pulmonary artery thrombosis in a patient with laboratory confirmed SARS.

Identification of a novel coronavirus in bats

Exotic wildlife can act as reservoirs of diseases that are endemic in the area or can be the source of new emerging diseases through interspecies transmission. The recent emergence of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) highlights the importance of virus surveillance in wild animals. Here, we report the identification of a novel bat coronavirus through surveillance of coronaviruses in wildlife. Analyses of the RNA sequence from the ORF1b and S-gene regions indicated that the virus is a group 1 coronavirus. The virus was detected in fecal and respiratory samples from three bat species (Miniopterus spp.). In particular, 63% (12 of 19) of fecal samples from Miniopterus pusillus were positive for the virus. These findings suggest that this virus might be commonly circulating in M. pusillus in Hong Kong.

Two Probable Cases of Serious Drug Interaction Between Clarithromycin and Colchicine

Although colchicine is a commonly used medication in patients with gouty arthritis and various multisystem disorders, its safety margin in therapeutic use is not well understood. This report describes two fatal cases of agranulocytosis presumed to result from a drug interaction involving colchicine and clarithromycin.

Fatal Interaction between Clarithromycin and Colchicine in Patients with Renal Insufficiency: A Retrospective Study

BACKGROUND

Clarithromycin is frequently used to treat community-acquired pneumonia in elderly persons. Like erythromycin, it may interact with other drugs by interfering with metabolism by cytochrome P450 enzymes and with the P-glycoprotein transporter system. Colchicine, used for treatment of acute gout and for prophylaxis, may cause bone marrow toxicity. It is metabolized by CYP3A4 and is transported by P-glycoprotein. Initial case reports suggested potentially fatal interactions between clarithromycin and colchicine.

METHODS

A retrospective study was conducted with 116 patients who were prescribed clarithromycin and colchicine during the same clinical admission. Case-control comparisons were made between patients who received concomitant therapy with the 2 drugs and patients who received sequential therapy. We assessed the clinical presentations and outcomes of the 2 patient groups and analyzed the risk factors associated with fatal outcomes.

RESULTS

Nine (10.2%) of the 88 patients who received the 2 drugs concomitantly died. Only 1 (3.6%) of the 28 patients who received the drugs sequentially died. Multivariate analysis of the 88 patients who received concomitant therapy showed that longer overlapped therapy (relative risk [RR], 2.16; 95% confidence interval [CI], 1.41-3.31; P< or =.01), the presence of baseline renal impairment (RR, 9.1; 95% CI, 1.75-47.06; P<.001), and the development of pancytopenia (RR, 23.4; 95% CI, 4.48-122.7; P<.001) were independently associated with death.

CONCLUSIONS

Clarithromycin increases the risk of fatal colchicine toxicity, especially for patients with renal insufficiency. Since there are other drugs for treatment of pneumonia and gout, these 2 drugs should not be coprescribed, because of the risk of fatality.

Phylogenetic and recombination analysis of coronavirus HKU1, a novel coronavirus from patients with pneumonia

Phylogenetic trees constructed using predicted amino acid sequences of putative proteins of coronavirus HKU1 (CoV-HKU1) revealed that CoV-HKU1 formed a distinct branch among group 2 coronaviruses. Of the 14 trees from p65 to nsp10, nine showed that CoV-HKU1 was clustered with murine hepatitis virus. From nsp11, the topologies of the trees changed dramatically. For the eight trees from nsp11 to N, seven showed that the CoV-HKU1 branch was the first branch. The codon usage patterns of CoV-HKU1 differed significantly from those in other group 2 coronaviruses. Split decomposition analysis revealed that recombination events had occurred between CoV-HKU1 and other coronaviruses.

Human infection by avian influenza A H5N1

The Southeast Asian outbreak of the highly lethal avian influenza A H5N1 infection in humans is unlikely to abate because of the enormous number of backyard farms providing poultry as the main source of food protein in developing countries. This increases the risk of the emergence of a reassortant pandemic influenza virus with improved human-to-human transmissibility. Currently triage of suspected cases by epidemiological risk factors remains the only practical way of case identification for laboratory investigation and infection control. The clinical usefulness of rapid diagnostic laboratory tests requires more vigorous evaluation. The lethality of this disease may reflect systemic viral dissemination, cytokine storm, or alveolar flooding due to inhibition of cellular sodium channels. The present circulating genotype Z is intrinsically resistant to amantadine and rimantadine. Prognosis may be improved by early treatment with a neuraminidase inhibitor with good systemic drug levels, and post-exposure prophylaxis for health care workers is recommended. The role of immunomodulators and other modalities of therapy requires evaluation in randomised controlled trials, with prospective monitoring of the viral load and cytokine profiles in various clinical specimens. In view of the high fatality of the disease, a combination of contact, droplet, and airborne precautions are recommended as long as resources allow despite the fact that the relative importance of these three modes in nosocomial transmission of avian influenza is still unknown.

Clinical evaluation of real-time PCR assays for rapid diagnosis of SARS coronavirus during outbreak and post-epidemic periods

BACKGROUND

The protocols of WHO network laboratories facilitated development of rapid diagnosis for SARS coronavirus (CoV) using reverse transcription (RT)-PCR assays. However, several reports have shown that conventional and real-time PCR assays were very specific for SARS CoV but lack sensitivity depending on the assay, specimen, and time course of disease.

OBJECTIVE

To evaluate an automatic nucleic acid extraction system and two standardized real-time PCR assays for rapid diagnosis of SARS CoV during outbreak and post-epidemic periods in Hong Kong.

STUDY DESIGN

Specimens from clinically suspected SARS patients collected during outbreak and post-epidemic periods were tested by an automatic nucleic acid extraction system followed by our first generation conventional RT-PCR and two standardized real-time PCR assays (Artus GmbH, Germany and Roche Diagnostics, Germany). Paired serum samples were assayed for increasing titer against SARS CoV.

RESULTS

In the SARS epidemic, Artus and Roche PCR assays exhibited sensitivities of 87% and 85% for respiratory specimens (n = 64), 91% and 88% for stool (n = 44), and 82% for urine (n = 29). A specificity of 100% was exhibited by both PCR assays except Artus attained only a 92% specificity for stool. For post-epidemic period, no SARS CoV was identified among 56 respiratory specimens by all PCR assays. Inhibitors to PCR assays were detected at an average rate of 7-8% among 202 clinical specimens.

CONCLUSION

This study highlights the high throughput and performance of automatic RNA extraction in coordination with standardized real-time PCR assays suitable for large-scale routine diagnosis in case of future SARS epidemic. As no SARS CoV was detected among specimens collected during post-epidemic period, the positive predictive value of real-time PCR assays for detection of SARS CoV during low epidemic requires further evaluation.

Occurrence and molecular analysis of extended-spectrum β-lactamase-producing Proteus mirabilis in Hong Kong, 1999–2002

OBJECTIVES

A study was conducted to evaluate the occurrence and characterization of extended-spectrum beta-lactamases (ESBLs) among blood isolates of Proteus mirabilis collected over a 4 year period in Hong Kong.

METHODS

Production of ESBLs among 99 consecutive and non-duplicate isolates was evaluated by the double-disc synergy test. The ESBLs were characterized by isoelectric focusing and PCR sequencing using specific primers. The epidemiological relationship of the isolates was studied by the Dienes test and PFGE.

RESULTS

ESBLs were identified in 13 isolates, from none in 1999-2000 and up to 18.5% (5/27) in 2001 and 25.8% (8/31) in 2002. The ESBL-producing isolates were more resistant to ceftriaxone than to ceftazidime, and were more likely than non-ESBL-producers to have resistance to ciprofloxacin (76.9% versus 14%) and gentamicin (38.5% versus 9.3%). The ESBL content included CTX-M-13 (n=8), CTX-M-14 (n=3), SHV-5 (n=2), TEM-11 (n=1), and an unidentified ESBL with a pI of 7.5. The Dienes test revealed that the genetic background in the 99 isolates was highly heterogeneous, with 54 distinct types among 92 isolates and seven were non-typeable. Among the 13 ESBL-producing isolates, five different backgrounds, including one cluster (Dienes-pulsotype A) with nine isolates, were identified by both Dienes test and PFGE, thus suggesting both clonal and multi-clonal spread of the CTX-M enzymes.

CONCLUSIONS

Our findings indicate the emergence of CTX-M enzymes among P. mirabilis in Hong Kong. More ESBL screening of this species is required to improve their recognition.

Duration of RT-PCR positivity in severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is a highly infectious respiratory infection with a high mortality. The duration of infectivity is unknown. The RT-PCR positivity for SARS-associated coronavirus (SARS-CoV) was followed in 45 virologically confirmed SARS patients. Serial RT-PCRs for SARS-CoV were performed in the nasopharyngeal aspirate, stool and urine of 45 SARS patients who survived until discharge. All patients had at least one site that was positive for SARS-CoV on presentation. Time to RT-PCR conversion was studied in all patients. There were 15 males (33.3%) and 30 females (66.7%), with a mean+/- SD age of 40.7+/-14.7 yrs. The median (range) time of RT-PCR conversion was 30 days (2-81). On discharge from the hospital, 18 (40%) remained RT-PCR positive in at least one site. For patients with positive RT-PCR on discharge, the median (range) time to RT-PCR conversion after discharge was 13 days (2-60). A significant proportion of severe acute respiratory syndrome patients remained RT-PCR positive for severe acute respiratory syndrome-associated coronavirus for a substantial duration after discharge. The clinical significance is unknown and this finding merits further study. It is prudent to advise patients to adhere to strict personal hygiene on discharge until RT-PCR becomes negative.

Clostridium bacteraemia characterised by 16S ribosomal RNA gene sequencing

BACKGROUND

Owing to problems in accurate species identification of the diverse genus clostridium, the epidemiology and pathogenicity of many species are not fully understood. Moreover, previous studies on clostridium bacteraemia have been limited and relied only on phenotypic species identification.

AIMS

To characterise the epidemiology, disease spectrum, and outcome of clostridium bacteraemia using 16S ribosomal RNA (rRNA) gene sequencing.

METHOD

During a four year period (1998-2001), all cases of clostridium bacteraemia were prospectively studied and all "non-perfringens" clostridium isolates identified to the species level by 16S rRNA gene sequencing.

RESULTS

Fifty one blood culture isolates were identified as Clostridium perfringens and 17 belonged to 11 other clostridium species. The first case of C disporicum infection and two cases of clostridium bacteraemia in children with intussusception were also described. Of the 68 clostridium isolates from 68 different patients, 38 were associated with clinically relevant bacteraemia. The gastrointestinal and hepatobiliary tracts were common sites of both underlying disease and portal of entry in these patients. Clostridium perfringens accounted for 79% of all clinically relevant bacteraemia, with the remainder caused by a diversity of species. The attributable mortality rate of clinically relevant clostridium bacteraemia was 29%. Younger age and underlying gastrointestinal/hepatobiliary tract disease were associated with mortality (p < 0.05).

CONCLUSIONS

Patients with clinically relevant clostridium bacteraemia should be investigated for the presence of underlying disease processes in the gastrointestinal or hepatobiliary tracts. 16S rRNA gene analysis will continue to be useful in further understanding the pathogenicity of various clostridium species.