Clinical features, antimicrobial susceptibilities, and outcomes of Elizabethkingia meningoseptica (Chryseobacterium meningosepticum) bacteremia at a medical center in Taiwan, 1999-2006.

A total of 118 patients with Elizabethkingia meningoseptica bacteremia at a medical center in Taiwan from 1999 to 2006 were studied. Minimum inhibitory concentrations (MICs) of 99 preserved isolates were determined. The incidence (per 100,000 admissions) of E. meningoseptica bacteremia increased from 7.5 in 1996 to 35.6 in 2006 (p = 0.006). Among them, 84% presented with fever, 86% had nosocomial infections, and 60% had acquired the infection in intensive care units (ICUs). The most common underlying diseases were malignancy (36%) and diabetes mellitus (25%). Seventy-eight percent of patients had primary bacteremia, followed by pneumonia (9%), soft tissue infection, and catheter-related bacteremia (6%). Forty-five patients (38%) had polymicrobial bacteremia. Overall, the 14-day mortality was 23.4%. Multivariate analysis revealed E. meningoseptica bacteremia acquired in an ICU (p = 0.048, odds ratio [OR] 4.23) and presence of effective antibiotic treatment after the availability of culture results (p = 0.049, OR 0.31) were independent predictors of 14-day mortality. The 14-day mortality was higher among patients receiving carbapenems (p = 0.046) than fluoroquinolones or other antimicrobial agents. More than 80% of the isolates tested were susceptible to trimethoprim-sulfamethoxzole, moxifloxacin, and levofloxacin. The MIC(50) and MIC(90) of the isolates to tigecycline and doxycycline were both 4 µg/mL and 8 µg/ml, respectively.

Multidrug-resistant Acinetobacter baumannii bacteraemia: clinical features, antimicrobial therapy and outcome.

Nosocomial infections caused by Acinetobacter baumannii have increased in recent years. Isolates of multidrug-resistant A. baumannii (MDRAB) have been recovered in Taiwan since 1999. The characteristics of 55 patients with MDRAB bacteraemia infections occurring between January 2003 and February 2005 were analysed retrospectively. The overall 30-day mortality rate was 49%. The portal of entry was identified in 80% of patients, with the respiratory tract being implicated most frequently. Among the different antimicrobial regimens prescribed, the combination of a carbapenem and ampicillin-sulbactam was associated with a better outcome than the combination of a carbapenem and amikacin, or a carbapenem alone.

Analysis of native microflora and selection of strains antagonistic to human pathogens on fresh produce.

The native microflora of three types of produce (green bell peppers, Romaine lettuce, and prepeeled baby carrots) and two types of sprouting seeds (alfalfa and clover) were investigated. Aerobic plate count (APC) for each produce or seed type as determined on Pseudomonas agar F (PAF) with incubation at 28 degrees C was in the range of 4 to 7 log CFU per g of tissue or seed. There was no significant difference (P > or = 0.05) in APC when the determinations were made with three agar media including PAF, brain heart infusion agar, and plate count agar. However, the APC as determined from plates that were incubated at 28 degrees C was significantly (P < or = 0.05) higher than with incubation at 37 degrees C. Fluorescent pseudomonads accounted for 23 to 73% of APC and 6 to 18% of APC recovered from carrots, pepper, and lettuce were pectolytic. Forty-eight strains of pectolytic bacteria were randomly isolated and identified, respectively, as members of the genera of Pseudomonas, Erwinia, Bacillus, Xanthomonas, or Flavobacterium. Lactic acid bacteria and/or yeast were consistently isolated from baby carrots, lettuce, and sprouting seeds (alfalfa or clover) but not from green bell peppers. Approximately 120 strains of indigenous microflora were tested for their ability to inhibit the growth of Salmonella Chester, Listeria monocytogenes, Escherichia coli, or Erwinia carotovora subsp. carotovora on PAF. Six isolates capable of inhibiting the growth of at least one pathogen were isolated and identified, respectively, as Bacillus spp. (three strains), Pseudomonas aeruginosa (one strain), Pseudomonas fluorescens (strain A3), and yeast (strain D1). When green pepper disks were inoculated with strains A3 and D1, the growth of Salmonella Chester and L. monocytogenes on the disks was reduced by 1 and 2 logs, respectively, over a period of 3 days. Application of strains A3 and D1 as potential biopreservatives for enhancing the quality and safety of fresh produce is discussed.

Response to trisodium phosphate treatment of Salmonella Chester attached to fresh-cut green pepper slices.

A laboratory model using green pepper disks was developed to investigate the attachment of Salmonella Chester on plant tissue and to evaluate the effectiveness of sanitizer agents in inactivating attached bacteria on fruits. Pepper disks (14 mm in diam, and 3-4 mm in thickness) were immersed in a bacterial suspension containing 1.5 x 107 cfu x mL(-1) of S. Chester for 30 s and subsequently air-dried at room temperature for 10 min. Approximately 30% of the bacteria retained on the disk after immersion were firmly attached and could not be removed by two washes and agitation. A positive correlation was observed between the number of bacteria attached and the concentration of bacteria in the suspension. Population studies and scanning electron microscopic examinations revealed that attachment of S. Chester on pepper disks occurred mainly on the surfaces of injured (cut) tissue but rarely on the unbroken skin. When inoculated disks were treated with 3% to 12% (w/v) of trisodium phosphate (TSP) at pH 12.3 for 5 min, the population of bacteria on the disk was reduced by 10- to 100-fold. A small portion (0.7% to 7.1%) of bacteria attached to the disk were either resistant to or protected from the TSP treatment. When the pH of TSP solution was reduced from 12.3 to 4.5, the effectiveness of TSP in inactivating S. Chester on pepper disks was reduced by 26%. This study shows that surfaces of injured fruit tissue are the principal sites for bacterial attachment, and a small portion of the bacteria attached to the tissue are resistant to the sanitizer treatment. Avoiding mechanical injuries to fresh fruits during and after harvest would reduce the chance of pathogen attachment and contamination on green pepper and fruits of similar nature.

Antiplatelet effect of marchantinquinone, isolated from Reboulia hemisphaerica, in rabbit washed platelets.

Platelet activation is involved in serious pathological situations, including atherosclerosis and restenosis. It is important to find efficient antiplatelet medicines to prevent fatal thrombous formation during the course of these diseases. Marchantinquinone, a natural compound isolated from Reboulia hemisphaerica, inhibited platelet aggregation and ATP release stimulated by thrombin (0.1 units mL(-1)), platelet-activating factor (PAF; 2 ng mL(-1)), collagen (10 microg mL(-1)), arachidonic acid (100 microM), or U46619 (1 microM) in rabbit washed platelets. The IC50 values of marchantinquinone on the inhibition of platelet aggregation induced by these five agonists were 62.0 +/- 9.0, 86.0 +/- 7.8, 13.6 +/- 4.7, 20.9 +/- 3.1 and 13.4 +/- 5.3 microM, respectively. Marchantinquinone inhibited thromboxane B2 (TxB2) formation induced by thrombin, PAF or collagen. However, marchantinquinone did not inhibit TxB2 formation induced by arachidonic acid, indicating that marchantinquinone did not affect the activity of cyclooxygenase and thromboxane synthase. Marchantinquinone did inhibit the rising intracellular Ca2+ concentration stimulated by the five platelet-aggregation inducers. The formation of inositol monophosphate induced by thrombin was inhibited by marchantinquinone. Platelet cAMP and cGMP levels were unchanged by marchantinquinone. The results indicate that marchantinquinone exerts antiplatelet effects by inhibiting phosphoinositide turnover.

Influence of soft rot bacteria on growth of Listeria monocytogenes on potato tuber slices.

Growth of Listeria monocytogenes on potato tuber slices and its interaction with four representative species of soft rot bacteria (Pseudomonas fluorescens, P. viridiflava, Erwinia carotovora subsp. carotovora, and Xanthomonas campestris) were investigated. When potato tuber slices were inoculated with one of two L. monocytogenes strains (Scott A and ATCC 15313), an increase in numbers of 3 to 4 logs per gram of tissue was observed with samples that were stored at 20 degrees C for 6 days. However, an increase of about 2 logs was observed with samples that were stored at 8 degrees C for 12 days. When potato slices were simultaneously inoculated with L. monocytogenes and one of the four soft rot bacteria, the growth of L. monocytogenes was inhibited in the presence of P. fluorescens or P. viridiflava but was not significantly affected in the presence of E. carotovora or X. campestris. The antagonism of the two pseudomonads to L. monocytogenes was also observed in potato tuber extract and in culture media. Formation of inhibition zones was observed only in iron-deficient media but not in the medium supplemented with FeCl3. In addition, production of fluorescent siderophore (pyoverdin) by these two pseudomonads was demonstrated. L. monocytogenes was unable to colonize macerated plant tissue induced by soft-rotting bacteria 2 days before inoculation of the pathogen. These results indicate that growth of L. monocytogenes on potato tuber slices is differentially affected by soft rot bacteria and that antagonism of fluorescent pseudomonads to L. monocytogenes is possibly caused by the production of iron-chelating siderophore by these pseudomonads.

Cloning and characterization of a pectate lyase gene from the soft-rotting bacterium Pseudomonas viridiflava.

Pseudomonas viridiflava is a soft-rotting pathogen of harvested vegetables that produces an extracellular pectate lyase (PL) responsible for maceration of plant tissue. A pel gene encoding PL was cloned from the genome of strain SJ074 and efficiently expressed in Escherichia coli. After a series of deletion subclonings and analysis by transposon mutagenesis, the pel gene was located in a 1.2-kb PstI-BglII genomic fragment. This fragment appears to contain a promoter at the PstI end required for pel gene expression. The PL produced by pectolytic E. coli clones is identical to those produced by strain SJ074 and by other strains of P. viridiflava in terms of molecular weight (42 kDa) and pI (9.7). A mutant of strain SJ074, designated MEI, which had Tn5 specifically inserted in the pel locus was constructed by site-directed mutagenesis. The MEI mutant produced 70- to 100-fold less PL than the wild type and failed to cause tissue maceration in plants. PL production and soft-rot pathogenicity in MEI and in a Pel- mutant previously isolated from strain SF312 were restored to the wild-type level by complementation in trans with the cloned pel gene. By using the 1.2-kb fragment as a probe, pel homologs were detected in four bacteria that are pathologically unrelated to P. viridiflava. These include three pathovars of P. syringae (pv. lachrymans, pv. phaseolicola, and pv. tabaci) and Xanthomonas campestris pv. malvacearum. No DNA fragments showing homology to pel of P. viridiflava were detected in genomic digests prepared from two strains of soft-rot erwinias.(ABSTRACT TRUNCATED AT 250 WORDS)