Shen-Wu Ho

Molecular Evidence for Strain Dissemination of Penicillium marneffei: An Emerging Pathogen in Taiwan

From January 1987 through December 1998, Penicillium marneffei infection (23 patients) or colonization (1 patient) was diagnosed in a total of 24 patients in Taiwan. Of these 24 patients, 16 (67%) had AIDS and 20 (83%) had disseminated P. marneffei infection. The majority (63%) of the infections were considered indigenous. The number of cases has increased markedly in recent years, with 17 of the 24 cases diagnosed from 1996 through 1998. Twenty preserved isolates of P. marneffei, recovered from 11 patients treated at National Taiwan University Hospital during the period of January 1996 through December 1998, were studied to determine the epidemiology of P. marneffei infections. Among the 20 isolates, a total of 8 strains (highly related isolates) were identified on the basis of tests for susceptibility to 5 antifungal agents, for chromosomal DNA restriction fragment-length polymorphism types, and for randomly amplified polymorphic DNA patterns. One of the strains (6 isolates) was isolated from 4 patients treated in 1997 and 1998. Strain spreading of P. marneffei may partially contribute to the increased number of infections caused by this organism in immunosuppressed patients in Taiwan.

Pandrug-Resistant Acinetobacter baumannii Causing Nosocomial Infections in a University Hospital, Taiwan

The rapid emergence (from 0% before 1998 to 6.5% in 2000) of pandrug-resistant Acinetobacter baumannii (PDRAB) was noted in a university hospital in Taiwan. To understand the epidemiology of these isolates, we studied 203 PDRAB isolates, taken from January 1999 to April 2000: 199 from 73 hospitalized patients treated at different clinical settings in the hospital and 4 from environmental sites in an intensive-care unit. Pulsed-field gel electrophoresis analysis and random amplified polymorphic DNA (RAPD) generated by arbitrarily primed polymerase chain reaction of these 203 isolates showed 10 closely related genotypes (10 clones). One (clone 5), belonging to pulsotype E and RAPD pattern 5, predominated (64 isolates, mostly from patients in intensive care). Increasing use of carbapenems and ciprofloxacin (selective pressure) as well as clonal dissemination might have contributed to the wide spread of PDRAB in this hospital.

Antimicrobial drug resistance in pathogens causing nosocomial infections at a university hospital in Taiwan, 1981-1999.

To determine the distribution and antimicrobial drug resistance in bacterial pathogens causing nosocomial infections, surveillance data on nosocomial infections documented from 1981 to 1999 at National Taiwan University Hospital were analyzed. During this period, 35,580 bacterial pathogens causing nosocomial infections were identified. Candida species increased considerably, ranking first by 1999 in the incidence of pathogens causing all nosocomial infections, followed by Staphylococcus aureus and Pseudomonas aeruginosa. Candida species also increased in importance as bloodstream infection isolates, from 1.0% in 1981-1986 to 16.2% in 1999. The most frequent isolates from urinary tract infections were Candida species (23.6%), followed by Escherichia coli (18.6%) and P. aeruginosa (11.0%). P. aeruginosa remained the most frequent isolates for respiratory tract and surgical site infections in the past 13 years. A remarkable increase in incidence was found in methicillin-resistant S. aureus (from 4.3% in 1981-1986 to 58.9% in 1993-1998), cefotaxime-resistant E. coli (from 0% in 1981-1986 to 6.1% in 1993-1998), and cefotaxime-resistant Klebsiella pneumoniae (from 4.0% in 1981-1986 to 25.8% in 1993-1998). Etiologic shifts in nosocomial infections and an upsurge of antimicrobial resistance among these pathogens, particularly those isolated from intensive care units, are impressive and alarming.

The LuxR family protein SpnR functions as a negative regulator of N‐acylhomoserine lactone‐dependent quorum sensing in Serratia marcescens

Serratia marcescens SS‐1 produces at least four N ‐acylhomoserine lactones (AHLs) which were identified using high‐resolution mass spectrometry and chemical synthesis, as N‐ (3‐oxohexanoyl) homo‐serine lactone (3‐oxo‐C6‐HSL), N ‐hexanoyl‐ (C6‐HSL), N ‐heptanoyl (C7‐HSL) and N ‐octanoyl‐ (C8‐HSL) homoserine lactone. These AHLs are synthesized via the LuxI homologue SpnI, and regulate via the LuxR homologue SpnR, the production of the red pigment, prodigiosin, the nuclease, NucA, and a biosurfactant which facilitates surface translocation. spnR overexpression and spnR gene deletion show that SpnR, in contrast to most LuxR homologues, acts as a negative regulator. spnI overexpression, the provision of exogenous AHLs and spnI gene deletion suggest that SpnR is de‐repressed by 3‐oxo‐C6‐HSL. In addition, long chain AHLs antagonize the biosurfactant‐mediated surface translocation of S. marcescens SS‐1. Upstream of spnI there is a gene which we have termed spnT . spnI and spnT form an operon and although database searches failed to reveal any spnT homologues, overexpression of this novel gene negatively affected both sliding motility and prodigiosin production.

Nosocomial Infections Caused by Sphingomonas paucimobilis: Clinical Features and Microbiological Characteristics

From January 1995 to September 1996, 14 isolates of Sphingomonas paucimobilis, including 11 from clinical specimens from six patients with nosocomial infection and three from environmental sources, were collected. Two of the six patients had intravascular catheter-related bacteremia and one each had bacteremic biliary tract infection, urinary tract infection, ventilator-associated pneumonia, and wound infection. The S. paucimobilis isolates were identified according to biochemical profiles established with use of the API 20NE system and Vitek GNI card and the characteristic cellular fatty acid chromatogram. Ten biotypes, 11 antibiograms (by the Etest), and 12 random amplified polymorphic DNA (RAPD) patterns (by arbitrarily primed polymerase chain reaction) were identified. The identical biotype, antibiogram, and RAPD pattern of the two isolates (one each from blood and bile) from a patient with biliary tract infection indicated the invasiveness of the organism. Two patients with intravascular catheter-related bacteremia had isolates of this organism repeatedly recovered, and these isolates had heterogeneous RAPD patterns. The present study highlights the wide distribution in hospital environments of various clones of S. paucimobilis, which may cause recurrent infections by a single strain or several episodes of infection due to two or more clones of this organism in hospitalized patients.

Quinupristin-Dalfopristin Resistance among Gram-Positive Bacteria in Taiwan

ABSTRACT To understand quinupristin-dalfopristin resistance among clinical isolates of gram-positive bacteria in Taiwan, where this agent is not yet available for clinical use, we evaluated 1,287 nonduplicate isolates recovered from January 1996 to December 1999 for in vitro susceptibility to quinupristin-dalfopristin and other newer antimicrobial agents. All methicillin-susceptible Staphylococcus aureus (MSSA) isolates were susceptible to quinupristin-dalfopristin. High rates of nonsusceptibility to quinupristin-dalfopristin (MICs, ≥2 μg/ml) were demonstrated for the following organisms: methicillin-resistant S. aureus (MRSA) (31%), coagulase-negative staphylococci (CoNS) (16%),Streptococcus pneumoniae (8%), viridans group streptococci (51%), vancomycin-susceptible enterococci (85%), vancomycin-resistantEnterococcus faecalis (100%), vancomycin-resistantEnterococcus faecium (66%), Leuconostoc spp. (100%), Lactobacillus spp. (50%), andPediococcus spp. (87%). All isolates of MSSA, MRSA,S. pneumoniae, and viridans group streptococci were susceptible to vancomycin and teicoplanin. The rates of nonsusceptibility to vancomycin and teicoplanin were 5 and 7%, respectively, for CoNS, ranging from 12 and 18% for S. simulans to 0 and 0% for S. cohnii and S. auricularis. Moxifloxacin and trovafloxacin had good activities against these isolates except for ciprofloxacin-resistant vancomycin-resistant enterococci and methicillin-resistant staphylococci. In Taiwan, virginiamycin has been used in animal husbandry for more than 20 years, which may contribute to the high rates of quinupristin-dalfopristin resistance.

High Prevalence of Antimicrobial Resistance in Rapidly Growing Mycobacteria in Taiwan

ABSTRACT An increasing number of clinical isolations of rapidly growing mycobacteria (RGM) at the National Taiwan University Hospital were noted from 1992 to 2001. Broth microdilution MICs of 15 antimicrobial agents were determined for 200 clinical isolates of RGM, including the Mycobacterium fortuitum group (69 isolates), M. chelonae (39 isolates), and M. abscessus (92 isolates). Our results showed that the resistance rates of these isolates to the currently available agents were remarkably high. Amikacin was active against nearly all RGM isolates. Clarithromycin was usually active against M. abscessus (79% susceptibility) and the M. fortuitum group (65% susceptibility). The majority of M. fortuitum group isolates were susceptible to ciprofloxacin (62%) and imipenem (61%). The susceptibilities to other conventional anti-RGM agents of these isolates were poor but differed markedly by species. The newer fluoroquinolones (levofloxacin, moxifloxacin, and gatifloxacin) and meropenem showed better in vitro activities against the M. fortuitum group isolates than against the other two species of RGM. Linezolid had fairly good activity against these RGM isolates, particularly against M. chelonae isolates (82% susceptible). Telithromycin had poor activity against these RGM isolates (the MICs at which 50% of the isolates tested are inhibited [MIC50s] were 32 to 64 μg/ml, and the MIC90s were >64 μg/ml).

High Incidence of Erythromycin Resistance among Clinical Isolates of Streptococcus agalactiae in Taiwan

ABSTRACT The in vitro susceptibilities of 266 isolates ofStreptococcus agalactiae determined by the agar dilution method showed that 6% of isolates were nonsusceptible to penicillin and 46% was resistant to erythromycin. Of the erythromycin-resistant isolates, 86.3% had the macrolide-lincosamide-streptogramin (MLS) resistance phenotype (constitutive MLS, 85.5%; inducible MLS, 0.8%) and 13.7% had the M phenotype.

groESL Sequence Determination, Phylogenetic Analysis, and Species Differentiation for Viridans Group Streptococci

ABSTRACT The full-length sequences of the groESL genes (also known as cpn10/60) of Streptococcus anginosus, Streptococcus constellatus, Streptococcus gordonii, and Streptococcus sanguis and the near full-length sequence of the groESL genes of Streptococcus intermedius, Streptococcus bovis, Streptococcus mitis, Streptococcus mutans, Streptococcus oralis, and Streptococcus salivarius were determined. The lengths of the groES genes from the 10 species listed above ranged from 282 to 288 bp, and the full-length sequences of groEL determined for 4 species (S. anginosus, S. constellatus, S. gordonii, and S. sanguis) revealed that each was 1,623 bp. The intergenic region (spacer) between the groES and groEL genes varies in size (15 to 111 bp) and sequence between species. The variation of the groES sequences among the species tested was greater (62.1 to 95.1% nucleotide sequence identities) than that of the groEL sequences (77.2 to 95.2% nucleotide sequence identities). Phylogenetic analysis of the groES and groEL genes yielded evolutionary trees similar to the tree constructed by use of the 16S rRNA gene. The intraspecies variation of the spacer was minimal for clinical isolates of some species. The groESL sequence data provide an additional parameter for identification of viridans group streptococcal species.

The RssAB Two-Component Signal Transduction System in Serratia marcescens Regulates Swarming Motility and Cell Envelope Architecture in Response to Exogenous Saturated Fatty Acids

Serratia marcescens swarms at 30 degrees C but not at 37 degrees C on a nutrient-rich (LB) agar surface. Mini-Tn5 mutagenesis of S. marcescens CH-1 yielded a mutant (WC100) that swarms not only vigorously at 37 degrees C but also earlier and faster than the parent strain swarms at 30 degrees C. Analysis of this mutant revealed that the transposon was inserted into a gene (rssA) predicted to encode a bacterial two-component signal transduction sensor kinase, upstream of which a potential response regulator gene (rssB) was located. rssA and rssB insertion-deletion mutants were constructed through homologous recombination, and the two mutants exhibited similar swarming phenotypes on LB swarming agar, in which swarming not only occurred at 37 degrees C but also initiated at a lower cell density, on a surface with a higher agar concentration, and more rapidly than the swarming of the parent strain at 30 degrees C. Both mutants also exhibited increased hemolysin activity and altered cell surface topologies compared with the parent CH-1 strain. Temperature and certain saturated fatty acids (SFAs) were found to negatively regulate S. marcescens swarming via the action of RssA-RssB. Analysis of the fatty acid profiles of the parent and the rssA and rssB mutants grown at 30 degrees C or 37 degrees C and under different nutrition conditions revealed a relationship between cellular fatty acid composition and swarming phenotypes. The cellular fatty acid profile was also observed to be affected by RssA and RssB. SFA-dependent inhibition of swarming was also observed in Proteus mirabilis, suggesting that either SFAs per se or the modulation of cellular fatty acid composition and hence homeostasis of membrane fluidity may be a conserved mechanism for regulating swarming motility in gram-negative bacteria.