Fungal infection risks associated with the use of cytokine antagonists and immune checkpoint inhibitors.

IMPACT STATEMENT: The risk of opportunistic infections due to fungi is relatively less well addressed in patients receiving biologic agents, compared with other opportunistic bacterial and viral infections. There is a lack of consensus guideline on the screening, prophylaxis, and management of fungal infection in patients anticipated to receive or actively receiving biologic therapy. In addition, invasive mycosis in immunocompromised patients is associated with high mortality and morbidity. This review highlighted the risk of fungal infection in patients receiving cytokine antagonists and immune checkpoint inhibitors, two big categories of biologic agents that are widely used in the treatment of various autoimmune and malignant conditions, often in combination with other immunomodulatory or immunosuppressive agents but also as standalone therapy. The adverse outcomes of opportunistic fungal infection in these patients can be reduced by heightened awareness, active case finding, and prompt treatment.

Clinical characteristics and molecular epidemiology of hepatitis E in Shenzhen, China: a shift toward foodborne transmission of hepatitis E virus infection.

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis in China. Recently, a shift in molecular epidemiology from hepatitis E genotype 1 (HEV-1) to hepatitis E genotype 4 (HEV-4) has been observed in Northern China, marking a switch from human-to-human transmission to zoonosis. However, similar data from cities in Southern China are lacking. This observational study of human hepatitis E cases in Shenzhen, a metropolitan city in the Pearl River Delta region, aimed to describe the clinical features and molecular epidemiology of hepatitis E in Southern China. Over a 55-month period, we identified 20 patients with acute hepatitis E. Most were middle-aged men, and 50% of patients had concomitant liver disease, of whom 70% were identified to have non-alcoholic fatty liver disease; such patients had a trend toward higher liver enzymes. Quantitative real-time RT-PCR using archived serum samples showed that 12 patients had hepatitis E viremia at presentation. Sequencing of the RNA-dependent RNA polymerase gene was performed for five of these patients, and phylogenetic analysis revealed that these five HEV isolates belonged to subgenotype 4b and were clustered with swine HEV isolates from Southern China. Combined with other studies showing similar findings, this suggests that the molecular epidemiology of hepatitis E in China is evolving toward low-level endemicity driven by foodborne transmission from seafood or pork products. The importance of concomitant liver disease, in particular non-alcoholic fatty liver disease, as a risk factor for severe hepatitis E requires further study.

Coronavirus HKU15 in respiratory tract of pigs and first discovery of coronavirus quasispecies in 5'-untranslated region.

Coronavirus HKU15 is a deltacoronavirus that was discovered in fecal samples of pigs in Hong Kong in 2012. Over the past three years, Coronavirus HKU15 has been widely detected in pigs in East/Southeast Asia and North America and has been associated with fatal outbreaks. In all such epidemiological studies, the virus was generally only detected in fecal/intestinal samples. In this molecular epidemiology study, we detected Coronavirus HKU15 in 9.6% of the nasopharyngeal samples obtained from 249 pigs in Hong Kong. Samples that tested positive were mostly collected during winter. Complete genome sequencing of the Coronavirus HKU15 in two nasopharyngeal samples revealed quasispecies in one of the samples. Two of the polymorphic sites involved indels, but the other two involved transition substitutions. Phylogenetic analysis showed that the two nasopharyngeal strains in the present study were most closely related to the strains PDCoV/CHJXNI2/2015 from Jiangxi, China, and CH/Sichuan/S27/2012 from Sichuan, China. The outbreak strains in the United States possessed highly similar genome sequences and were clustered monophyletically, whereas the Asian strains were more diverse and paraphyletic. The detection of Coronavirus HKU15 in respiratory tracts of pigs implies that in addition to enteric infections, Coronavirus HKU15 may be able to cause respiratory infections in pigs and that in addition to fecal-oral transmission, the virus could possibly spread through the respiratory route. The presence of the virus in respiratory samples provides an alternative clinical sample to confirm the diagnosis of Coronavirus HKU15 infection. Quasispecies were unprecedentedly observed in the 5'-untranslated region of coronavirus genomes.

First isolation of West Nile virus from a dromedary camel.

Although antibodies against West Nile virus (WNV) have been detected in the sera of dromedaries in the Middle East, North Africa and Spain, no WNV has been isolated or amplified from dromedary or Bactrian camels. In this study, WNV was isolated from Vero cells inoculated with both nasal swab and pooled trachea/lung samples from a dromedary calf in Dubai. Complete-genome sequencing and phylogenetic analysis using the near-whole-genome polyprotein revealed that the virus belonged to lineage 1a. There was no clustering of the present WNV with other WNVs isolated in other parts of the Middle East. Within lineage 1a, the dromedary WNV occupied a unique position, although it was most closely related to other WNVs of cluster 2. Comparative analysis revealed that the putative E protein encoded by the genome possessed the original WNV E protein glycosylation motif NYS at E154-156, which contained the N-linked glycosylation site at N-154 associated with increased WNV pathogenicity and neuroinvasiveness. In the putative NS1 protein, the A70S substitution observed in other cluster 2 WNVs and P250, which has been implicated in neuroinvasiveness, were present. In addition, the foo motif in the putative NS2A protein, which has been implicated in neuroinvasiveness, was detected. Notably, the amino-acid residues at 14 positions in the present dromedary WNV genome differed from those in most of the closely related WNV strains in cluster 2 of lineage 1a, with the majority of these differences observed in the putative E and NS5 proteins. The present study is the first to demonstrate the isolation of WNV from dromedaries. This finding expands the possible reservoirs of WNV and sources of WNV infection.

Comparative analysis of the activation of unfolded protein response by spike proteins of severe acute respiratory syndrome coronavirus and human coronavirus HKU1.

BACKGROUND: Whereas severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) is associated with severe disease, human coronavirus HKU1 (HCoV-HKU1) commonly circulates in the human populations causing generally milder illness. Spike (S) protein of SARS-CoV activates the unfolded protein response (UPR). It is not understood whether HCoV-HKU1 S protein has similar activity. In addition, the UPR-activating domain in SARS-CoV S protein remains to be identified. RESULTS: In this study we compared S proteins of SARS-CoV and HCoV-HKU1 for their ability to activate the UPR. Both S proteins were found in the endoplasmic reticulum. Transmembrane serine protease TMPRSS2 catalyzed the cleavage of SARS-CoV S protein, but not the counterpart in HCoV-HKU1. Both S proteins showed a similar pattern of UPR-activating activity. Through PERK kinase they activated the transcription of UPR effector genes such as Grp78, Grp94 and CHOP. N-linked glycosylation was not required for the activation of the UPR by S proteins. S1 subunit of SARS-CoV but not its counterpart in HCoV-HKU1 was capable of activating the UPR. A central region (amino acids 201-400) of SARS-CoV S1 was required for this activity. CONCLUSIONS: SARS-CoV and HCoV-HKU1 S proteins use distinct UPR-activating domains to exert the same modulatory effects on UPR signaling.

Burkholderia pseudomallei in soil samples from an oceanarium in Hong Kong detected using a sensitive PCR assay.

Melioidosis, caused by Burkholderia pseudomallei, is an emerging infectious disease with an expanding geographical distribution. Although assessment of the environmental load of B. pseudomallei is important for risk assessment in humans or animals in endemic areas, traditional methods of bacterial culture for isolation have low sensitivities and are labor-intensive. Using a specific polymerase chain reaction (PCR) assay targeting a Tat domain protein in comparison with a bacterial culture method, we examined the prevalence of B. pseudomallei in soil samples from an oceanarium in Hong Kong where captive marine mammals and birds have contracted melioidosis. Among 1420 soil samples collected from various sites in the oceanarium over a 15-month period, B. pseudomallei was detected in nine (0.6%) soil samples using bacterial culture, whereas it was detected in 96 (6.8%) soil samples using the specific PCR assay confirmed by sequencing. The PCR-positive samples were detected during various months, with higher detection rates observed during summer months. Positive PCR detection was significantly correlated with ambient temperature (P<0.0001) and relative humidity (P=0.011) but not with daily rainfall (P=0.241) or a recent typhoon (P=0.787). PCR-positive samples were obtained from all sampling locations, with the highest detection rate in the valley. Our results suggest that B. pseudomallei is prevalent and endemic in the oceanarium. The present PCR assay is more sensitive than the bacterial culture method, and it may be used to help better assess the transmission of melioidosis and to design infection control measures for captive animals in this unique and understudied environment.

An adult zebrafish model for Laribacter hongkongensis infection: Koch's postulates fulfilled.

Laribacter hongkongensis is a gram-negative emerging bacterium associated with invasive bacteremic infections in patients with liver disease and fish-borne community-acquired gastroenteritis and traveler's diarrhea. Although the complete genome of L. hongkongensis has been sequenced, no animal model is available for further study of its pathogenicity mechanisms. In this study, we showed that adult zebrafish infected with L. hongkongensis by immersion following dermal abrasion or intraperitoneal injection suffered mortality in a dose-dependent manner, with lethal dose 50 (LD50) of 2.1×10(4) and 1.9×10(4) colony-forming units (CFU)/mL, respectively. All mortalities occurred in the first four days post-infection. Zebrafish that died showed characteristic clinicopathological features: swimming near water surface, marked lethargy and sidestroke; abdominal hemorrhage, ulcers and marked swelling with ascites; and hydropic degeneration and necrosis of hepatocytes around central vein and inflammatory cells infiltration. L. hongkongensis was recovered from the ascitic fluid and tissues of zebrafish that died. Of the 30 zebrafish infected with 2.1×10(4) CFU/mL (LD50) L. hongkongensis isolated from dead zebrafish using the immersion following dermal abrasion method, 18 (60%) died. All zebrafish that died also showed the characteristic clinical and pathological features. Histopathological studies also showed dilation of hepatic central vein and hydropic degeneration. L. hongkongensis was isolated from the zebrafish that died. The Koch's postulates for L. hongkongensis as an infectious agent have been fulfilled. This highly reproducible and effective zebrafish model is of crucial importance for future studies on virulence factors for L. hongkongensis infection.

A novel MLST sequence type discovered in the first fatal case of Laribacter hongkongensis bacteremia clusters with the sequence types of other human isolates.

Laribacter hongkongensis is a gram-negative, facultative anaerobic, motile, S-shaped, asaccharolytic, urease-positive bacillus in the Neisseriaceae family of ß-proteobacteria. To date, all patients with L. hongkongensis infection have survived, including the two patients with L. hongkongensis bacteremia and patients with L. hongkongensis gastroenteritis. In this study, we describe the clinical, microbiological and molecular characterization of the first fatal case associated with L. hongkongensis bacteremia in a patient with colonic carcinoma that metastasized to the liver. The identity of the isolate was confirmed via phenotypic tests and 16S rRNA gene sequencing. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), using the Bruker database extended with L. hongkongensis reference strains, also identified the isolate as L. hongkongensis, with a top match score of 2.473. Multilocus sequence typing revealed a new sequence type (ST), and phylogenetic analysis and eBURST demonstrated unambiguously that the ST of the isolate was clustered with two other STs found exclusively in human patients, consistent with the theory that some clones of L. hongkongensis could be more virulent than others. Underlying liver diseases and ascites potentially represent distinct risk factors for invasive L. hongkongensis infection. More widespread use of MALDI-TOF MS for identification and improvements of selective media should facilitate the identification of more cases of L. hongkongensis infection.

Genetic relatedness of the novel human group C betacoronavirus to Tylonycteris bat coronavirus HKU4 and Pipistrellus bat coronavirus HKU5.

The recent outbreak of severe respiratory infections associated with a novel group C betacoronavirus (HCoV-EMC) from Saudi Arabia has drawn global attention to another highly probable "SARS-like" animal-to-human interspecies jumping event in coronavirus (CoV). The genome of HCoV-EMC is most closely related to Tylonycteris bat coronavirus HKU4 (Ty-BatCoV HKU4) and Pipistrellus bat coronavirus HKU5 (Pi-BatCoV HKU5) we discovered in 2006. Phylogenetically, HCoV-EMC is clustered with Ty-BatCoV HKU4/Pi-BatCoV HKU5 with high bootstrap supports, indicating that HCoV-EMC is a group C betaCoV. The major difference between HCoV-EMC and Ty-BatCoV HKU4/Pi-BatCoV HKU5 is in the region between S and E, where HCoV-EMC possesses five ORFs (NS3a-NS3e) instead of four, with low (31%-62%) amino acid identities to Ty-BatCoV HKU4/Pi-BatCoV HKU5. Comparison of the seven conserved replicase domains for species demarcation shows that HCoV-EMC is a novel CoV species. More intensive surveillance studies in bats and other animals may reveal the natural host of HCoV-EMC.

A significant number of reported Absidia corymbifera (Lichtheimia corymbifera) infections are caused by Lichtheimia ramosa (syn. Lichtheimia hongkongensis): an emerging cause of mucormycosis.

Recently, we and others reported the discovery of Lichtheimia ramosa (syn. Lichtheimia hongkongensis). We also hypothesized that a proportion of 'Absidia corymbifera (Lichtheimia corymbifera)' reported in the literature could be L. ramosa. In this study, we characterized 13 strains that had been reported as 'A. corymbifera (L. corymbifera)' in the literature over an 11-year period. Microscopic examination of agar block smear preparations of all 13 strains showed abundant circinate side branches and pleomorphic giant cells with finger-like projections of L. ramosa. ITS1-5.8S-ITS2 rRNA gene cluster (internal transcribed spacer (ITS)) and partial elongation factor-1alpha (EF1α) gene sequencing showed that all 13 strains were clustered with L. ramosa; partial ß-actin gene sequencing showed that most of the 13 strains were clustered with L. ramosa; and partial 28S rRNA gene sequencing showed that all 13 strains were clustered with L. ramosa, but one strain of L. corymbifera (HKU25) was also clustered with other strains of L. ramosa. A significant number of reported A. corymbifera (L. corymbifera) infections are L. ramosa infections which are of global distribution. In clinical microbiology laboratories, L. ramosa should be suspected if an Absidia-like mold that possesses abundant circinate side branches on the sporangiophores and pleomorphic giant cells with finger-like projections is observed. ITS and partial EF1α gene sequencing are more reliable than partial ß-actin and 28S rRNA gene sequencing for identification of the Lichtheimia species.

Transport genes and chemotaxis in Laribacter hongkongensis: a genome-wide analysis.

BACKGROUND: Laribacter hongkongensis is a Gram-negative, sea gull-shaped rod associated with community-acquired gastroenteritis. The bacterium has been found in diverse freshwater environments including fish, frogs and drinking water reservoirs. Using the complete genome sequence data of L. hongkongensis, we performed a comprehensive analysis of putative transport-related genes and genes related to chemotaxis, motility and quorum sensing, which may help the bacterium adapt to the changing environments and combat harmful substances. RESULTS: A genome-wide analysis using Transport Classification Database TCDB, similarity and keyword searches revealed the presence of a large diversity of transporters (n = 457) and genes related to chemotaxis (n = 52) and flagellar biosynthesis (n = 40) in the L. hongkongensis genome. The transporters included those from all seven major transporter categories, which may allow the uptake of essential nutrients or ions, and extrusion of metabolic end products and hazardous substances. L. hongkongensis is unique among closely related members of Neisseriaceae family in possessing higher number of proteins related to transport of ammonium, urea and dicarboxylate, which may reflect the importance of nitrogen and dicarboxylate metabolism in this assacharolytic bacterium. Structural modeling of two C4-dicarboxylate transporters showed that they possessed similar structures to the determined structures of other DctP-TRAP transporters, with one having an unusual disulfide bond. Diverse mechanisms for iron transport, including hemin transporters for iron acquisition from host proteins, were also identified. In addition to the chemotaxis and flagella-related genes, the L. hongkongensis genome also contained two copies of qseB/qseC homologues of the AI-3 quorum sensing system. CONCLUSIONS: The large number of diverse transporters and genes involved in chemotaxis, motility and quorum sensing suggested that the bacterium may utilize a complex system to adapt to different environments. Structural modeling will provide useful insights on the transporters in L. hongkongensis.

Environmental adaptability and stress tolerance of Laribacter hongkongensis: a genome-wide analysis.

BACKGROUND: Laribacter hongkongensis is associated with community-acquired gastroenteritis and traveler's diarrhea and it can reside in human, fish, frogs and water. In this study, we performed an in-depth annotation of the genes in its genome related to adaptation to the various environmental niches. RESULTS: L. hongkongensis possessed genes for DNA repair and recombination, basal transcription, alternative σ-factors and 109 putative transcription factors, allowing DNA repair and global changes in gene expression in response to different environmental stresses. For acid stress, it possessed a urease gene cassette and two arc gene clusters. For alkaline stress, it possessed six CDSs for transporters of the monovalent cation/proton antiporter-2 and NhaC Na+:H+ antiporter families. For heavy metals acquisition and tolerance, it possessed CDSs for iron and nickel transport and efflux pumps for other metals. For temperature stress, it possessed genes related to chaperones and chaperonins, heat shock proteins and cold shock proteins. For osmotic stress, 25 CDSs were observed, mostly related to regulators for potassium ion, proline and glutamate transport. For oxidative and UV light stress, genes for oxidant-resistant dehydratase, superoxide scavenging, hydrogen peroxide scavenging, exclusion and export of redox-cycling antibiotics, redox balancing, DNA repair, reduction of disulfide bonds, limitation of iron availability and reduction of iron-sulfur clusters are present. For starvation, it possessed phosphorus and, despite being asaccharolytic, carbon starvation-related CDSs. CONCLUSIONS: The L. hongkongensis genome possessed a high variety of genes for adaptation to acid, alkaline, temperature, osmotic, oxidative, UV light and starvation stresses and acquisition of and tolerance to heavy metals.

Virulence determinants, drug resistance and mobile genetic elements of Laribacter hongkongensis: a genome-wide analysis.

BACKGROUND: Laribacter hongkongensis is associated with community-acquired gastroenteritis and traveler's diarrhea. In this study, we performed an in-depth annotation of the genes in its genome related to the various steps in the infective process, drug resistance and mobile genetic elements. RESULTS: For acid and bile resistance, L. hongkongensis possessed a urease gene cassette, two arc gene clusters and bile salt efflux systems. For intestinal colonization, it possessed a putative adhesin of the autotransporter family homologous to those of diffusely adherent Escherichia coli (E. coli) and enterotoxigenic E. coli. To evade from host defense, it possessed superoxide dismutase and catalases. For lipopolysaccharide biosynthesis, it possessed the same set of genes that encode enzymes for synthesizing lipid A, two Kdo units and heptose units as E. coli, but different genes for its symmetrical acylation pattern, and nine genes for polysaccharide side chains biosynthesis. It contained a number of CDSs that encode putative cell surface acting (RTX toxin and hemolysins) and intracellular cytotoxins (patatin-like proteins) and enzymes for invasion (outer membrane phospholipase A). It contained a broad variety of antibiotic resistance-related genes, including genes related to ß-lactam (n = 10) and multidrug efflux (n = 54). It also contained eight prophages, 17 other phage-related CDSs and 26 CDSs for transposases. CONCLUSIONS: The L. hongkongensis genome possessed genes for acid and bile resistance, intestinal mucosa colonization, evasion of host defense and cytotoxicity and invasion. A broad variety of antibiotic resistance or multidrug resistance genes, a high number of prophages, other phage-related CDSs and CDSs for transposases, were also identified.

Infectious diseases emerging from Chinese wet-markets: zoonotic origins of severe respiratory viral infections.

PURPOSE OF REVIEW: In China, close contacts between humans and food animals have resulted in the transmission of many microbes from animals to humans. The two most notable infectious diseases in recent years are severe acute respiratory syndrome and avian influenza. In this review, these two severe zoonotic viral infections transmitted by the respiratory route, with pandemic potential, are used as models to illustrate the role of Chinese wet-markets in their emergence, amplification and dissemination. RECENT FINDINGS: Two research groups independently discovered the presence of severe acute respiratory syndrome coronavirus-like viruses in horseshoe bats. An astonishing diversity of coronaviruses was also discovered in different species of bats. For the recent and still ongoing avian influenza H5N1 outbreak that originated in Southeast Asia, from 2003 to 21 April 2006, 204 humans have been infected, with 113 deaths. Most patients had recent direct contacts with poultry. SUMMARY: In Chinese wet-markets, unique epicenters for transmission of potential viral pathogens, new genes may be acquired or existing genes modified through various mechanisms such as genetic reassortment, recombination and mutation. The wet-markets, at closer proximity to humans, with high viral burden or strains of higher transmission efficiency, facilitate transmission of the viruses to humans.

Anaerobic, non-sporulating, Gram-positive bacilli bacteraemia characterized by 16S rRNA gene sequencing.

Owing to the difficulties in identifying anaerobic, non-sporulating, Gram-positive bacilli in clinical microbiology laboratories, the epidemiology and clinical spectrum of disease of many of these bacteria have been poorly understood. The application of 16S rRNA gene sequencing in characterizing bacteraemia due to anaerobic, non-sporulating Gram-positive bacilli during a 4-year period is described. The first case of Olsenella uli bacteraemia, in a patient with acute cholangitis, is also reported. Among 165 blood culture isolates of anaerobic, Gram-positive bacilli, 75 were identified as Propionibacterium acnes by phenotypic tests and 21 as members of other anaerobic, non-sporulating Gram-positive bacilli by 16S rRNA gene sequencing. Of these 96 isolates, 16 (17 %) were associated with cases of clinically significant bacteraemia, among which 10 (63 %) were caused by Eggerthella, four (25 %) by Lactobacillus and one (6 %) by each of Eubacterium tenue and O. uli. Five of the 10 Eggerthella isolates were Eggerthella lenta, whereas the other five belonged to two novel Eggerthella species, with Eggerthella hongkongensis being almost as prevalent as Eggerthella lenta. Underlying disease in the gastrointestinal tract, isolation of Eggerthella and Lactobacillus, and monomicrobial bacteraemia were associated with clinically significant bacteraemia, whereas isolation of P. acnes and polymicrobial bacteraemia were associated with pseudobacteraemia. Most patients with clinically significant bacteraemia had underlying diseases, with diseases in the gastrointestinal tract being most common. The overall mortality rate was 31 %. Immunocompromised patients with clinically significant bacteraemia due to anaerobic, non-sporulating, Gram-positive bacilli other than P. acnes should be treated with appropriate antibiotics. The unexpected frequency of isolation of Eggerthella from blood cultures and its association with clinically significant disease suggest that this genus is probably of high pathogenicity. Further studies to look for specific virulence factors are warranted.

Streptococcus sinensis may react with Lancefield group F antiserum.

Lancefield group F streptococci have been found almost exclusively as members of the 'Streptococcus milleri' group, although they have been reported very occasionally in some other streptococcal species. Among 302 patients with bacteraemia caused by viridans streptococci over a 6-year period, three cases were caused by Streptococcus sinensis (type strain HKU4T, HKU5 and HKU6). All three patients had infective endocarditis complicating their underlying chronic rheumatic heart diseases. Gene sequencing showed no base differences between the 16S rRNA gene sequences of HKU5 and HKU6 and that of HKU4T. All three strains were Gram-positive, non-spore-forming cocci arranged in chains. All grew on sheep blood agar as alpha-haemolytic, grey colonies of 0.5-1 mm in diameter after 24 h incubation at 37 degrees C in ambient air. Lancefield grouping revealed that HKU5 and HKU6 were Lancefield group F, but HKU4T was non-groupable with Lancefield groups A, B, C, D, F or G antisera. HKU4T was identified by the Vitek system (GPI), API system (20 STREP) and ATB system (ID32 STREP) as 99 % Streptococcus intermedius, 51.3 % S. intermedius and 99.9 % Streptococcus anginosus, respectively. Using the same tests, HKU5 was identified as 87 % Streptococcus sanguinis/Streptococcus gordonii, 59 % Streptococcus salivarius and 99.6 % S. anginosus, respectively, and HKU6 as 87 % S. sanguinis/S. gordonii, 77 % Streptococcus pneumoniae and 98.3 % S. anginosus, respectively. The present data revealed that a proportion of Lancefield group F streptococci could be S. sinensis. Lancefield group F streptococci should not be automatically reported as 'S. milleri'.

Thermo-tolerant Campylobacter fetus bacteraemia identified by 16S ribosomal RNA gene sequencing: an emerging pathogen in immunocompromised patients.

Eight Campylobacter isolates that were able to grow at 25 degrees C and 42 degrees C and had the same biochemical profile were isolated from the blood of eight immunocompromised patients. Conventional biochemical tests were unable to determine whether they were isolates of thermo-tolerant C. fetus, H2S-negative C hyointestinalis, or a new Campylobacter species. Sequencing of the 16S ribosomal RNA genes showed that all eight isolates had the same nucleotide sequence and this was identical to that of C. fetus (GenBank accession no. AF219233). All eight patients had underlying disease and two died despite antibiotic treatment. Because of the ability of C fetus to grow over a wide range of temperatures and a higher incidence of bacteraemia by this organism than C. jejuni in the past 5 years in Hong Kong, thermo-tolerant C fetus may be an emerging pathogen in immunocompromised patients in the years to come.

Cloning and characterisation of malE in Burkholderia pseudomallei.

No recombinant protein is available for serodiagnosis or skin test in the diagnosis of melioidosis. This report describes the cloning of the malE gene, which encodes an immunogenic protein of Burkholderia pseudomallei. Bi-directional DNA sequencing of malE revealed that the gene contained a single open reading frame encoding 416 amino acid residues with a predicted molecular mass of 44.4 kDa. BLAST analysis showed that the putative protein encoded by malE is homologous to the maltose-binding protein (MBP) of other bacteria. It has 48% and 63% amino acid identity and similarity with the MBP of Brucella abortus, and malE complementation assay showed that it partially complemented the function of the MBP of Escherichia coli. Several highly conserved regions among the MBP of B. pseudomallei, Br. abortus, Salmonella enterica serotype Typhimurium, E. coli and Enterobacter aerogenes were observed. These regions represent signatures A, B, C, D and F identified in the MBP of E. coli. Further sequence analysis revealed that the first 24 amino acid residues of the MBP of B. pseudomallei probably represent the N-terminal signal peptide of the protein. Similar to the signal peptide of the MBP of E. coli, Ent. aerogenes and S. Typhimurium, the MBP of B. pseudomallei contains two basic residues in the first eight amino acids, followed by a hydrophobic core, with the last three amino acids in the signal peptide being Ala-Gln-Ala, conforming to the consensus sequence Ala-X-Ala at positions -3 to -1 relative to the site of proteolytic cleavage for recognition by signal peptidase I. Further studies on serodiagnosis of melioidosis with recombinant MBP should be performed.