Most current fluoroquinolone-resistant E. coli clinical isolates, and the largest share of multidrug-resistant isolates, represent a highly clonal subgroup that likely originated from a single rapidly expanded and disseminated ST131 strain. Focused attention to this strain will be required to control the fluoroquinolone and multidrug-resistant E. coli epidemic.

Summary In this work we describe the identification of a copper‐inducible regulon in Mycobacterium tuberculosis (Mtb). Among the regulated genes was Rv0190/MT0200, a paralogue of the copper metalloregulatory repressor CsoR. The five‐locus regulon, which includes a gene that encodes the copper‐protective metallothionein MymT, was highly induced in wild‐type Mtb treated with copper, and highly expressed in an Rv0190/MT0200 mutant. Importantly, the Rv0190/MT0200 mutant was hyper‐resistant to copper. The promoters of all five loci share a palindromic motif that was recognized by the gene product of Rv0190/MT0200. For this reason we named Rv0190/MT0200 RicR for regulated in copper repressor. Intriguingly, several of the RicR‐regulated genes, including MymT, are unique to pathogenic Mycobacteria. The identification of a copper‐responsive regulon specific to virulent mycobacterial species suggests copper homeostasis must be maintained during an infection. Alternatively, copper may provide a cue for the expression of genes unrelated to metal homeostasis, but nonetheless necessary for survival in a host.

Propionibacterium acnes is increasingly recognized as an important agent of prosthetic joint infection (PJI).However, the optimum culture conditions for recovery of this organism from PJI specimens have not been determined. By applying a prolonged 28-day culture incubation to all periprosthetic specimens received for bacterial culture from 198 revision arthroplasty procedures, we retrospectively determined that a 13-day culture incubation period is necessary for the recovery of P. acnes from patients with PJI. Incubation beyond this period was associated with increasing recovery of nondiagnostic isolates: 21.7% of P. acnes isolates believed to be clinically unimportant were recovered after 13 days of incubation. Importantly, a diagnosis of P. acnes PJI would have been missed in 29.4% of patients had extended culture incubation been applied only to anaerobic culture media. Although specimens from P. acnes PJIs were more commonly associated with the presence of >2 culture media positive for growth, acute inflammation (>5 neutrophils/high-power field) was observed in only 40% of patients with PJIs that had more than one specimen submitted for bacterial culture. These results support the need for a minimum culture incubation period of 13 days to be applied to both aerobic and anaerobic culture media for all periprosthetic specimens. Optimal recovery of infecting organisms from PJI specimens will be an important component in generating a universal definition for PJI due to indolent agents of infection, such as P. acnes.

Multilocus sequence typing (MLST) is usually based on the sequencing of 5 to 8 housekeeping loci in the bacterial chromosome and has provided detailed descriptions of the population structure of bacterial species important to human health. However, even strains with identical MLST profiles (known as sequence types or STs) may possess distinct genotypes, which enable different eco-or pathotypic lifestyles. Here we describe a two-locus, sequence-based typing scheme for Escherichia coli that utilizes a 489-nucleotide (nt) internal fragment of fimH (encoding the type 1 fimbrial adhesin) and the 469-nt internal fumC fragment used in standard MLST. Based on sequence typing of 191 model commensal and pathogenic isolates plus 853 freshly isolated clinical E. coli strains, this 2-locus approach-which we call CH (fumC/fimH) typing-consistently yielded more haplotypes than standard 7-locus MLST, splitting large STs into multiple clonal subgroups and often distinguishing different within-ST ecoand pathotypes. Furthermore, specific CH profiles corresponded to specific STs, or ST complexes, with 95% accuracy, allowing excellent prediction of MLST-based profiles. Thus, 2-locus CH typing provides a genotyping tool for molecular epidemiology analysis that is more economical than standard 7-locus MLST but has superior clonal discrimination power and, at the same time, corresponds closely to MLST-based clonal groupings. E scherichia coli infections, which encompass both intestinal syndromes (e.g., diarrhea, dysentery) and extraintestinal syndromes (e.g., urinary tract infection [UTI], septicemia, newborn meningitis), represent a significant public health burden worldwide (17). Most extraintestinal E. coli infections are caused by strains from phylogenetic groups B2 and D, within which are concentrated the horizontally mobile genetic determinants associated with extraintestinal virulence, such as toxins, adhesins, protectins, and iron-scavenging systems (17).Multilocus sequence typing (MLST) is currently the preferred method for characterizing the relatedness of strains within bacterial species (19). Standardized MLST schemes have been established for numerous human pathogens, including E. coli (38). Certain E. coli sequence types (STs, in which MLST profiles are identical) are epidemiologically associated with specific extraintestinal syndromes, e.g., ST127 and ST73 with pyelonephritis (15, 16), while others have been associated with important emerging antimicrobial resistance properties, e.g., ST69 with trimethoprimsulfamethoxazole resistance (20) and ST131 with fluoroquinolone resistance and extended-spectrum beta-lactamase production (22).However, STs are not uniform with regard to genetic properties or ecotypic/pathotypic behaviors. Within ST95, for example, strains from the North American OMP6 clade of serotype O18: K1:H7 encode P fimbriae and hemolysin and are strongly associated with both newborn meningitis and UTI (14), while strains from the European OMP9 clade of O18:K1:H7 encode neither element and are associated only w...