Chromosome-Level Genome Assembly of the Bioluminescent Cardinalfish Siphamia tubifer: An Emerging Model for Symbiosis Research.

The bioluminescent symbiosis involving the sea urchin cardinalfish Siphamia tubifer and the luminous bacterium Photobacterium mandapamensis is an emerging vertebrate model for the study of microbial symbiosis. However, little genetic data are available for the host, limiting the scope of research that can be implemented with this association. We present a chromosome-level genome assembly for S. tubifer using a combination of PacBio HiFi sequencing and Hi-C technologies. The final assembly was 1.2 Gb distributed on 23 chromosomes and contained 32,365 protein coding genes with a BUSCO score of 99%. A comparison of the S. tubifer genome to that of another nonluminous species of cardinalfish revealed a high degree of synteny, whereas a comparison to a more distant relative in the sister order Gobiiformes revealed the fusion of two chromosomes in the cardinalfish genomes. The complete mitogenome of S. tubifer was also assembled, and an inversion in the vertebrate WANCY tRNA genes as well as heteroplasmy in the length of the control region were discovered. A phylogenetic analysis based on whole the mitochondrial genome indicated that S. tubifer is divergent from the rest of the cardinalfish family, highlighting the potential role of the bioluminescent symbiosis in the initial divergence of Siphamia. This high-quality reference genome will provide novel opportunities for the bioluminescent S. tubifer-P. mandapamensis association to be used as a model for symbiosis research.

Mutations in topoisomerase genes of fluoroquinolone-resistant salmonellae in Hong Kong.

A total of 88 salmonella isolates (72 clinical isolates for which the ciprofloxacin MIC was >0.06 microg/ml, 15 isolates for which the ciprofloxacin MIC was < or =0.06 microg/ml, and Salmonella enterica serotype Typhimurium ATCC 13311) were studied for the presence of genetic alterations in four quinolone resistance genes, gyrA, gyrB, parC, and parE, by multiplex PCR amplimer conformation analysis. The genetic alterations were confirmed by direct nucleotide sequencing. A considerable number of strains had a mutation in parC, the first to be reported in salmonellae. Seven of the isolates sensitive to 0.06 micro g of ciprofloxacin per ml had a novel mutation at codon 57 of parC (Tyr57-->Ser) which was also found in 29 isolates for which ciprofloxacin MICs were >0.06 micro g/ml. Thirty-two isolates had a single gyrA mutation (Ser83-->Phe, Ser83-->Tyr, Asp87-->Asn, Asp87-->Tyr, or Asp87-->Gly), 34 had both a gyrA mutation and a parC mutation (29 isolates with a parC mutation of Tyr57-->Ser and 5 isolates with a parC mutation of Ser80-->Arg). Six isolates which were isolated recently (from 1998 to 2001) were resistant to 4 micro g of ciprofloxacin per ml. Two of these isolates had double gyrA mutations (Ser83-->Phe and Asp87-->Asn) and a parC mutation (Ser80-->Arg) (MICs, 8 to 32 microg/ml), and four of these isolates had double gyrA mutations (Ser83-->Phe and Asp87-->Gly), one parC mutation (Ser80-->Arg), and one parE mutation (Ser458-->Pro) (MICs, 16 to 64 micro g/ml). All six of these isolates and those with a Ser80-->Arg parC mutation were S. enterica serotype Typhimurium. One S. enterica serotype Typhi isolate harbored a single gyrA mutation (Ser83-->Phe), and an S. enterica serotype Paratyphi A isolate harbored a gyrA mutation (Ser83-->Tyr) and a parC mutation (Tyr57-->Ser); both of these isolates had decreased susceptibilities to the fluoroquinolones. The MICs of ciprofloxacin, levofloxacin, and sparfloxacin were in general the lowest of those of the six fluoroquinolones tested. Isolates with a single gyrA mutation were less resistant to fluoroquinolones than those with an additional parC mutation (Tyr57-->Ser or Ser80-->Arg), while those with double gyrA mutations were more resistant.

What have we learnt from community-acquired infections in Hong Kong?

This study was initiated throughout Hong Kong, to reveal the characteristics of community-acquired infections. All specimens collected by general practitioners from infected patients were followed prospectively, and those that were culture-positive were analysed. Four thousand seven hundred and forty-one specimens were collected from 3977 patients by 89 doctors from July 2000 to October 2001. The most common specimens were throat swabs (33%), urine (26%) and sputa (16%). The average culture-positive rate was 28%. The most common organisms were Escherichia coli (18%), beta-haemolytic streptococci (15%) and Staphylococcus aureus (12%). Fluoroquinolone resistance was relatively high (up to 35%) in organisms commonly causing urinary tract infection (E. coli, Proteus and Morganella). Although none of the pneumococci was resistant to penicillin 1 mg/L, the proportion with intermediate resistance (0.1-1 mg/L) was alarming (81%). There were three strains of methicillin-resistant S. aureus. A decrease in ampicillin resistance but a high prevalence of macrolide resistance were noted in Haemophilus influenzae. All Neisseria gonorrhoeae isolates were resistant to penicillin, up to 79% to the fluoroquinolones, 15% to spectinomycin, but all were susceptible to ceftriaxone. Respiratory pathogens (Streptococcus pneumoniae, beta-haemolytic streptococci and H. influenzae) were relatively susceptible to the newer fluoroquinolones (0-2%, 0.5-6% and 2% resistant, respectively) or third-generation cephalosporins (0-2% resistant). The distribution of organisms and their antibiotic resistance varied over time. Thus frequent surveillance is needed to provide information on the drugs of choice for different infections.

Results of fixation of clavicle alone in managing floating shoulder.

AIM OF STUDY: A retrospective review on the outcomes of four floating shoulder, ipsilateral scapular neck and clavicular fractures, treated with open reduction and internal fixation of the clavicle alone using plate and screws. METHODS: All patients were evaluated by interview, physical examination and radiological examination at an average follow up period of 3.3 years (range: 2-4 years). Functional outcomes were rated using Rowe's score. RESULTS: Radiological union of both fractures occurred at an average of 2.8 months (range: 8-12 weeks). Excellent result was seen in three cases and good in one. CONCLUSION: Plating of clavicle alone restored stability of shoulder and allowed early range of motion exercises. All cases gained good and excellent function.

Trucut needle biopsy through superior orbital fissure for the diagnosis of rabies.

Necropsy diagnosis of rabies can be done by taking a brain biopsy specimen with a trucut needle inserted through the superior orbital fissure into the cranial cavity. This technique reduces the number of personnel who require post-exposure prophylaxis and avoids full necropsy if the deceased's relatives are opposed.

Disconnection of a venous Port-A-Cath followed by embolization after saline flush: rare case report.

A 77-year-old man presented with painful swelling of his Port-A-Cath insertion site soon after flushing with normal saline. No discomfort or abnormality was found during the saline flush. A chest roentgenogram showed that the disconnected catheter had separated from the disc and was absent from its original location. The disconnected catheter was found embolized, by chest roentgenogram and CT scan, to the right atrium and hepatic vein. The patient was treated successfully with an X-ray guided extraction of the catheter. The possibility of catheter disconnection with embolization should be considered and a chest roentgenogram performed immediately in cases of rapid swelling of subcutaneous tissue around the port chamber after fluid infusion.

The antimicrobial activity and beta-lactamase stability of cefpirome, a new fourth-generation cephalosporin in comparison with other agents.

The antimicrobial activity of cefpirome was compared with amoxycillin/clavulanic acid, ampicillin/sulbactam, cefuroxime, ceftazidime, gentamicin and amikacin against 743 non-duplicate clinical isolates. MIC50 and MIC90 showed that the antibiotic was active against both Gram-negative and Gram-positive organisms. Cefpirome was highly active against most of the Enterobacteriaceae, including indole-positive Proteus spp., Aeromonas spp. (MIC < or = 1 mg/L) and Salmonella spp. (MIC < or = 0.5 mg/L). Neisseria gonorrhoeae and Haemophilus influenzae (including beta-lactamase producers) were all susceptible, with MIC less than 0.5 and 0.25 mg/L respectively. Cefpirome was more active than cefuroxime and ceftazidime against Campylobacter spp. (MIC < or = 2 mg/L), but less active than ceftazidime against Pseudomonas aeruginosa. Cefpirome was active against Streptococcus pneumoniae. Streptococcus bovis and coagulase-negative staphylococci (MIC < or = 0.5 mg/L) and methicillin-sensitive Staphylococcus aureus (MIC < or = 2 mg/L). Methicillin-resistant S. aureus, Gram-positive and Gram-negative anaerobes were resistant to cefpirome. The stability of cefpirome to TEM-1, TEM-2, PSE-1, SHV-1 and the chromosomal-mediated P99 and K-1 beta-lactamases was comparable to ceftazidime.

Unilateral piriformis syndrome in a patient with previous melanoma.

Several years after undergoing surgery for a malignant melanoma on his left lower back, a 51 year old man developed intermittently severe pain in his left posterior thigh. Plain X-rays showed no abnormality, but computerized tomography and magnetic resonance imaging scans demonstrated an abnormal soft tissue mass in the left sciatic notch. Although a metastasis from the original melanoma was suspected, exploration of the suspicious area revealed only hypertrophy of the left piriformis muscle. This was due to regular gymnasium exercises designed to selectively build up the musculature of the left lower limb, which the patient had undertaken in the firm belief that it would help to prevent a recurrence of his left-sided melanoma. Complete relief of the unilateral piriformis syndrome was achieved by division of the hypertrophied piriformis muscle, thereby relieving the pressure on the left sciatic nerve as it passed through the greater sciatic foramen.

Pharmacokinetics of parenteral imipenem/cilastatin in patients on continuous ambulatory peritoneal dialysis.

We investigated the pharmacokinetics of two intravenous (iv) dose regimens of imipenem/cilastatin in Chinese patients on chronic ambulatory peritoneal dialysis (CAPD), who had an average creatinine clearance of 3.2 ml/min/1.73 m2. Doses of 0.5 and 1.0 g produced mean peak serum imipenem concentrations of 30 and 70 mg/l respectively, about 60% of cilastatin. Peritoneal dialysis fluid (PDF) imipenem concentrations reached 20-30% of the serum peak 4-5 h after iv injection, and the lowest maximum PDF concentrations were 2 mg/l after the 0.5 g dose and 14 mg/l after 1.0 g. Thus both regimes produced PDF imipenem concentrations above the MICs of susceptible pathogens. The half-life of imipenem was 6.4 h and the plasma clearance 66 ml/min; serum and PDF imipenem were in equilibration after about 5 h. Cilastatin had a prolonged half-life of 19 h and a plasma clearance of 10 ml/min, and accumulated in both serum and PDF. With a 0.5 g dose, the pharmacokinetics of imipenem/cilastatin suggest that the combination may prove an effective treatment for peritonitis associated with CAPD.

Effect of tumour necrosis factor and lipid A on functional and structural vascular volume in solid murine tumours.

Effects of recombinant tumour necrosis factor (TNF) on functional and structural vascular volumes in solid murine Meth A tumours were investigated by injection of Hoechst 33342 and staining for the vascular basement membrane component laminin, respectively. Systemic injection of 3 x 10(4) U TNF caused an initial increase in functional volume in the tumour, but a strong decrease from 1 to 48 h after treatment. Early effects of intralesional treatment were more moderate. Systemic injection of 10(4) U TNF or 0.3 or 3 micrograms lipid A caused a fall in functional volume at 4 h, but a recovery was seen at 24 h. This recovery did not occur after treatment with a combination of 10(4) U TNF and 0.3 micrograms lipid A. Structural vascular volume was not markedly reduced until 24 h after treatment with the high doses of the separate agents and the combination. All effects appeared generally more prominent in the tumour centre than in the borders. Data suggest that TNF induces initially an active hyperaemia that rapidly converts to passive hyperaemia. A prolonged disturbance of tumour blood supply is probably necessary for therapeutic activity. Breakdown of laminin in the vascular basement membrane may be a cause of loss of vascular integrity.

Kinetics and morphology of chemically induced popliteal lymph node reactions compared with antigen-, mitogen-, and graft-versus-host-reaction-induced responses.

Changes in the popliteal lymph node (PLN) in mice evoked by a local graft-versus-host (GVH) reaction and by a single injection of various agents into the hind footpad were compared. The drug diphenylhydantoin induced similar weight changes in time as the GVH reaction. More vigorous and protracted reactions were induced by the drug nitrofurantoin and the contact sensitizer dinitrochlorobenzene, whereas the antigens lipopolysaccharide and sheep erythrocytes caused very moderate and short-lasting weight changes. Alterations of lymph node architecture upon injection of diphenylhydantoin resembled those observed during the GVH response. Some quantitative and qualitative differences were noted for nitrofurantoin, but clearly deviant morphological alterations were seen in response to lipopolysaccharide and sheep erythrocytes. The PLN reaction to dinitrochlorobenzene had features of both the GVH reaction and the antigen-induced responses. These findings support the concept that some drugs and chemicals may induce or exacerbate lymphoproliferative disorders by GVH-like mechanisms.

Rapid HPLC assay of fluoroquinolones in clinical specimens.

A simple isocratic HPLC procedure was developed for the analysis of seven quinolones and their metabolites in clinical specimens. It is likely that this system can be used for the assay of many other quinolone compounds, but not for nalidixic acid and the ciprofloxacin metabolite sulpho-ciprofloxacin which appear to be adsorbed in the column. Sample preparation takes approximately 20 min, and HPLC analysis is completed within 15 min with a simple solvent system eluted on a reversed phase column. The procedure is rapid, sensitive and specific, and is a modification of an assay for chloramphenicol and beta-lactam antibiotics. This method is therefore particularly useful for clinical laboratories, since a single HPLC system can be used for assays of chloramphenicol, beta-lactams and quinolones.

Susceptibilities of Hong Kong isolates of multiply resistant Shigella spp. to 25 antimicrobial agents, including ampicillin plus sulbactam and new 4-quinolones.

Seventy-two percent of 129 shigella isolates from two Hong Kong hospitals were Shigella flexneri. Twenty-six percent were S. sonnei, and there was only one isolate each of S. dysenteriae and S. boydii. Ninety-six percent of the isolates were resistant to two or more antibiotics, and up to 11 resistances were seen in a single isolate. Fifty-seven percent or more of these isolates were resistant to ampicillin, streptomycin, tetracycline, chloramphenicol, and sulfamethoxazole; and up to twenty-three percent were resistant to kanamycin, trimethoprim, trimethoprim-sulfamethoxazole, and gentamicin. All the isolates were susceptible to amikacin, nalidixic acid, and the newer 4-quinolone agents; and all but one were susceptible to the cephalosporins tested. Only three isolates remained resistant to ampicillin in the presence of sulbactam. Ampicillin plus sulbactam or the newer 4-quinolone agents may be alternatives for the treatment of severe infections caused by multiply resistant shigellas.

Comparative evaluation of the Abbott TDX, the Abbott ABA200, and the Syva LAB5000 for assay of serum gentamicin.

Three automated chemical assays for serum gentamicin were compared for accuracy, reproducibility and cost. One method utilized fluorescence polarization (Abbott TDX), and the other two enzyme-multiplied immunoassay (Abbott ABA200, and the Syva Lab5000). All three systems produced a high degree of accuracy and reproducibility with spiked samples when the concentrations of gentamicin were within the range of 3.0-8.0 mg/l. However, with concentrations below 2.0 mg/l or above 8.0 mg/l, only the TDX system gave acceptable coefficients of variation and accurate recoveries. Similarly, excellent correlations were obtained between all three systems for assays of clinical specimens containing 2.0-8.0 mg/l gentamicin, but above and below this range, the correlations were poor except between TDX and Lab5000 within the range of 0.0-2.0 mg/l. The Abbott TDX was thus the most accurate and reproducible of the three systems for the assay of serum gentamicin in the critical concentrations below 2.0 mg/l and above 8.0 mg/l. The cost per assay by the Abbott TDX was US$4.57 compared with US$5.40 for the Abbott ABA200, and US$3.20 for the Syva Lab5000.