Development of ceftazidime resistance in an acute Burkholderia pseudomallei infection.

Burkholderia pseudomallei, a bacterium that causes the disease melioidosis, is intrinsically resistant to many antibiotics. First-line antibiotic therapy for treating melioidosis is usually the synthetic β-lactam, ceftazidime (CAZ), as almost all B. pseudomallei strains are susceptible to this drug. However, acquired CAZ resistance can develop in vivo during treatment with CAZ, which can lead to mortality if therapy is not switched to a different drug in a timely manner. Serial B. pseudomallei isolates obtained from an acute Thai melioidosis patient infected by a CAZ susceptible strain, who ultimately succumbed to infection despite being on CAZ therapy for the duration of their infection, were analyzed. Isolates that developed CAZ resistance due to a proline to serine change at position 167 in the β-lactamase PenA were identified. Importantly, these CAZ resistant isolates remained sensitive to the alternative melioidosis treatments; namely, amoxicillin-clavulanate, imipenem, and meropenem. Lastly, real-time polymerase chain reaction-based assays capable of rapidly identifying CAZ resistance in B. pseudomallei isolates at the position 167 mutation site were developed. The ability to rapidly identify the emergence of CAZ resistant B. pseudomallei populations in melioidosis patients will allow timely alterations in treatment strategies, thereby improving patient outcomes for this serious disease

Molecular Epidemiology of Anthrax Cases Associated with Recreational Use of Animal Hides and Yarn in the United States

To determine potential links between the clinical isolate to animal products and their geographic origin, we genotyped (MLVA-8, MVLA-15, and canSNP analysis) 80 environmental and 12 clinical isolates and 2 clinical specimens from five cases of anthrax (California in 1976 [n = 1], New York in 2006 [n = 1], Connecticut in 2007 [n = 2], and New Hampshire in 2009[n = 1]) resulting from recreational handling of animal products. For the California case, four clinical isolates were identified as MLVA-8 genotype (GT) 76 and in the canSNP A.Br.Vollum lineage, which is consistent with the Pakistani origin of the yarn. Twenty eight of the California isolates were in the A.Br.Vollum canSNP lineage and one isolate was in the A.Br. 003/004 canSNP sub-group. All 52 isolates and both clinical specimens related to the New York and Connecticut cases were MLVA-8 GT 1. The animal products associated with the NY and CT cases were believed to originate from West Africa, but no isolates from this region are available to be genotyped for comparison. All isolates associated with the New Hampshire case were identical and had a new genotype (GT 149). Isolates from the NY, CT and NH cases diverge from the established canSNP phylogeny near the base of the A.Br.011/009. This report illustrates the power of the current genotyping methods and the dramatically different epidemiological conditions that can lead to infections (i.e., contamination by a single genotype versus widespread contamination of numerous genotypes). These cases illustrate the need to acquire and genotype global isolates so that accurate assignments can be made about isolate origins

An attenuated strain of Bacillus anthracis (CDC 684) has a large chromosomal inversion and altered growth kinetics

BackgroundAn isolate originally labeled Bacillus megaterium CDC 684 was found to contain both pXO1 and pXO2, was non-hemolytic, sensitive to gamma-phage, and produced both the protective antigen and the poly-D-glutamic acid capsule. These phenotypes prompted Ezzell et al., (J. Clin. Microbiol. 28:223) to reclassify this isolate to Bacillus anthracis in 1990.ResultsWe demonstrate that despite these B. anthracis features, the isolate is severely attenuated in a guinea pig model. This prompted whole genome sequencing and closure. The comparative analysis of CDC 684 to other sequenced B. anthracis isolates and further analysis reveals: a) CDC 684 is a close relative of a virulent strain, Vollum A0488; b) CDC 684 defines a new B. anthracis lineage (at least 51 SNPs) that includes 15 other isolates; c) the genome of CDC 684 contains a large chromosomal inversion that spans 3.3 Mbp; d) this inversion has caused a displacement of the usual spatial orientation of the origin of replication (ori) to the termination of replication (ter) from 180° in wild-type B. anthracis to 120° in CDC 684 and e) this isolate also has altered growth kinetics in liquid media.ConclusionsWe propose two alternative hypotheses explaining the attenuated phenotype of this isolate. Hypothesis 1 suggests that the skewed ori/ter relationship in CDC 684 has altered its DNA replication and/or transcriptome processes resulting in altered growth kinetics and virulence capacity. Hypothesis 2 suggests that one or more of the single nucleotide polymorphisms in CDC 684 has altered the expression of a regulatory element or other genes necessary for virulence

Dendrogram of MLVA-8 analysis of <i>B. anthracis</i> isolates collected from the 1976 California, 2006 New York, 2007 Connecticut anthrax cases, and 2009 New Hampshire case.

<p>All other genotypes are reference genotypes from Keim et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028274#pone.0028274-Keim1" target="_blank">[8]</a>. For the California case, the clinical isolates were GT 76 (n = 4), while environmental isolates were GT 71 (n = 2), GT 72 (n = 2), GT 92 (n = 1), and GT 105 (n = 1). All clinical and environmental isolates from the New York (one clinical, 35 environmental) and Connecticut cases (one clinical specimen, 15 environmental isolates) were GT 1. All clinical (n = 2) and environmental (n = 9) isolates from the NH case were GT 149. Scale bar indicates amount of evolutionary change <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028274#pone.0028274-McDonald1" target="_blank">[12]</a>.</p

Phylogeny of the major groups of <i>B. anthracis</i> after Pearson et al. (2004) and VanErt et al. (2007).

<p>The new branch, “A.Br.011,” is flanked by branches A.Br.008 and A.Br.009. Thus, the group A.Br.008/009 is now subdivided into two groups: A.Br.008/011 and A.Br.011/009. The canSNP signature and assay that defines this new branch is provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028274#pone-0028274-t003" target="_blank">Table 3</a>.</p

MLVA-8 results of clinical and environmental <i>B. anthracis</i> isolates associated with the California, New York, Connecticut, and New Hampshire anthrax cases.

<p>—, plasmid loci not detected.</p><p>NA, not applicable.</p><p>*, new allele size not previously described by Keim et al.</p