ABSTRACT
BACKGROUND/PURPOSE: The aim of this study was to investigate clinical presentation, serotype distribution and genetic correlation of group B streptococcus (GBS) diseases. Since serotype VI prevalence far exceeded that reported in prior studies, genetic relationship of isolates was further analyzed. METHODS: GBS isolates obtaining from patients with invasive diseases and pregnant women with colonization between June 2007 and December 2010 were analyzed. All isolates were tested for serotypes by multiplex PCR assay and pulsed-field gel electrophoresis (PFGE). Serotype VI isolates were further analyzed by multilocus sequence typing (MLST). RESULTS: A total of 134 GBS isolates were recovered from blood of 126 patients with invasive disease (94.0%) and anogenital swabs of 8 pregnant women (6.0%). Most common serotype was Ib (21.6%), followed by V (20.1%), VI (18.7%), III (15.7%), II (11.9 %), Ia (11.2%), and IX (0.7%). Serotype VI was also the leading type in infants with early onset disease (EOD; 3/8, 37.5%) and colonizing pregnant women (3/8, 37.5%). PFGE distinguished 33 pulsotypes, reflecting genetic diversity among GBS isolates. Among 25 serotype VI isolates tested, 14 were ST-1, seven were ST-679, three were ST-678, one was ST-681, and distributed into four PFGE pulsotypes. ST-678, ST-679, and ST-681 were novel sequence types; ST-678 and ST-679 are single-locus variants of ST-1 that belongs to clonal complex (CC) 1. CONCLUSION: CC1 dissemination of serotype VI GBS thus emerges as an important invasive pathogen in infants and nonpregnant adults in central Taiwan. Serotype prevalence of GBS must be continuously monitored geographically to guide prevention strategy of GBS vaccines.
Subject(s)
Bacteremia/epidemiology , Pregnancy Complications, Infectious/microbiology , Serogroup , Streptococcal Infections/epidemiology , Streptococcus agalactiae/isolation & purification , Adult , Aged , Aged, 80 and over , Bacteremia/drug therapy , Bacteremia/microbiology , Electrophoresis, Gel, Pulsed-Field , Female , Humans , Infant , Infant, Newborn , Male , Microbial Sensitivity Tests , Middle Aged , Multilocus Sequence Typing , Pregnancy , Streptococcal Infections/drug therapy , Streptococcal Infections/microbiology , Streptococcus agalactiae/genetics , Streptococcus agalactiae/pathogenicity , Taiwan/epidemiologyABSTRACT
Stenotrophomonas maltophilia KH has two acid beta-lactamases with isoelectric points (pIs) of 4.6 and 5.4, and several basic beta-lactamases (pIs >7.0) that produce a ladder-shaped pattern by IEF. An isogenic L2 mutant, KHL2(xylE), was constructed by gene replacement. From IEF and native PAGE zymograms of strains KH and KHL2(xylE), it was demonstrated that the basic beta-lactamases and the acid beta-lactamase with pI 5.4 are encoded by the same L2 gene and that the active types of these L2 charge variants were dependent on the buffer pH. The beta-lactamase activities of these L2 charge variants in phosphate buffer at pH 7.0 and 8.0 were 1075+/-29 and 1114+/-81 U mg(-1), respectively. These results indicate that L2 charge variants give S. maltophilia a better chance of adapting and surviving in response to changes in the environment.
Subject(s)
Stenotrophomonas maltophilia/enzymology , beta-Lactamases/genetics , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Base Sequence , Cefepime , Cephalosporins/pharmacology , Conjugation, Genetic , DNA, Bacterial/chemistry , Electrophoresis, Polyacrylamide Gel , Environmental Microbiology , Genetic Variation , Hydrogen-Ion Concentration , Isoelectric Focusing , Molecular Sequence Data , Polymerase Chain Reaction , Sequence Analysis, DNA , Stenotrophomonas maltophilia/drug effects , Stenotrophomonas maltophilia/genetics , Stenotrophomonas maltophilia/isolation & purification , beta-Lactamases/chemistry , beta-Lactamases/metabolismABSTRACT
Stenotrophomonas maltophilia is known to produce at least two chromosomal-mediated inducible beta-lactamases, L1 and L2. Gene L2, which encodes a class A beta-lactamase, and the adjacent ampR gene form an ampR-class A beta-lactamase module. L1 belongs to the class B beta-lactamase and has no neighbor ampR-like regulatory gene. In this study, the ampR-L2 module from S. maltophilia KH was compared with ampR-beta-lactamase modules from several microorganisms with respect to the AmpR and beta-lactamase proteins and the intergenic (IG) region. S. maltophilia and Xanthomonas campestris showed the most closely phylogenetic relationship among the microorganisms considered. The regulatory role of AmpR towards L1 and L2 was further analyzed. In the absence of an inducer, AmpR acted as an activator for L1 expression and as a repressor for L2 expression, whereas AmpR was an activator for both genes in an induced state. In addition, inducibility of L1 and L2 genes depended on the presence of AmpR. The ampR transcript was weakly and constitutively expressed, but was not autoregulated.
