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(See the Editorial Commentary by Lautenbach on pages 1266–9.) Escherichia coli causes diverse extraintestinal infections, including urinary tract infection, bacteremia, and meningitis, resulting in considerable morbidity, mortality, and increased costs [1]. Management of such infections is complicated by the rising prevalence of resistance to preferred antimicrobial agents such as trimethoprim-sulfamethoxazole (TMP-SMZ), fluoroquinolones (FQs), and extended-spectrum cephalosporins [1–4]. Contributing to this problem is E. coli sequence type 131 (ST131), a newly emerged, disseminated lineage of multidrug-resistant E. coli [2, 5–9]. In recent surveys ST131 has accounted for up to 10%–27% of the total clinical E. coli population in various locales, and for up to 52%–67% of all extended-spectrum β-lactamase (ESBL)–producing or FQ-resistant (FQ-R) E. coli [2, 10–12]. The Department of Veterans Affairs (VA) operates the largest integrated healthcare system in the United States. [13]. Escherichia coli infections, especially urinary tract infections, are quite common among veterans [14]. Based on associations of ST131 with older age and health care contact [15], and the high prevalence of these characteristics among veterans, we hypothesized that ST131 may contribute importantly to antimicrobial resistance in E. coli among veterans. Accordingly, we assessed the prevalence, geographic distribution, and contribution to antimicrobial resistance of E. coli ST131 among US veterans during 2010–2011 at multiple VA medical centers (VAMCs) across the United States, and explored associations of ST131 with source and fitness-promoting bacterial traits.

Objectives: The aim of this study was to identify changes in the gene expression profile of Streptococcus pneumoniae in response to a subinhibitory concentration of penicillin in an effort to better understand mechanisms by which this organism copes with this stress. Methods: S. pneumoniae serotype 2 strain D39 was grown for 1 h in the presence or absence of penicillin at a concentration equivalent to half the MIC (0.03 mg/L). RNA was isolated and gene expression profiles were compared using DNA microarrays. Differential expression of select genes was confirmed by real-time RT‐PCR. Results: A total of 386 genes were found to be responsive to penicillin. Up-regulated genes included those of the ciaR‐ciaH operon, luxS, genes encoding cell envelope proteins and genes of the pst locus. Down-regulated genes included genes involved in competence, genes encoding capsular polysaccharide biosynthesis proteins, genes involved in fatty acid chain elongation and genes of the polyamine transporter operon. Conclusions: Altered expression of these genes reflects a protective response to perturbation of the bacterial cell wall by penicillin. Such genes may represent potential therapeutic targets for enhancing the activity of penicillin against this organism and provide insight into novel mechanisms of penicillin resistance.

Aims: To investigate the use of a Staphylococcus epidermidis transcriptional regulator gene as target for species-specific determination. Methods and Results: Staph. epidermidis genes encoding putative transcriptional regulators were retrieved from GenBank and those showing no homology with other bacterial sequences were selected. Of the four PCR primer sets analysed, the primers Serp0107F/R from serp0107 amplified a specific product of 581 bp from Staph. epidermidis DNA only, and they did not cross-react in PCR with nonepidermidis staphylococci and other common bacteria. Conclusion: Being uniquely present in Staph. epidermidis, putative transcriptional regulator gene serp0107 offers a valuable target for specific identification of Staph. epidermidis. Significance and Impact of the Study: As a member of a specialized gene group, putative transcriptional regulator gene serp0107 may be important to Staph. epidermidis adaptation to its niche environment. Further analysis of serp0107 and its related protein may help reveal new insights on the molecular regulation of Staph. epidermidis survival and virulence.

Infections caused by Streptococcus pneumoniae (pneumococcus) are a major cause of mortality throughout the world. This organism is primarily a commensal in the upper respiratory tract of humans, but can cause pneumonia in high-risk persons and disseminate from the lungs by invasion of the bloodstream. Currently, prevention of pneumococcal infections is by immunization with vaccines which contain capsular polysaccharides from the most common serotypes causing invasive disease. However, there are more than 90 antigenically distinct serotypes and there is concern that serotypes not included in the vaccines may become more prevalent in the face of continued use of polysaccharide vaccines. Also, certain high-risk groups have poor immunological responses to some of the polysaccharides in the vaccine formulations. Protein antigens that are conserved across all capsular serotypes would induce more effective and durable humoral immune responses and could potentially protect against all clinically relevant pneumococcal capsular types. This review provides a summary of work on pneumococcal proteins that are being investigated as components for future generations of improved pneumococcal vaccines.

Streptococcus pneumoniae encodes a transporter for polyamines that contributes to virulence in an animal model. The putative polyamine-binding protein, PotD, has an amino-terminal secretory peptide but no other domains known to be involved in anchoring proteins to the surface of Gram-positive bacteria. Cell fractionation and immunoblotting, along with flow cytometry, suggest that PotD is surface-exposed and anchored to the cytoplasmic membrane by a potentially novel mechanism.

Strains of Providencia stuartii were collected from a chronic-care geriatric ward of a large Veteran's Administration hospital. Two strains of P. stuartii, and one of Escherichia coli isolated from the same ward, were transferred five times in the presence of gentamicin or netilmicin. At the fifth transfer the MICs of both gentamicin and netilmicin for the two P. stuartii strains had increased at least ten-fold. The MICs for the E. coli remained essentially unchanged. Enzyme assay demonstrated increased activity of an aminoglycoside-2'-acetylating enzyme in P. stuartii during the period of the transfers. Five subsequent transfers in the absence of aminoglycosides resulted in return of enzyme activity to the initial level. Neither of the P. stuartii strains tested contained any detectable plasmid DNA. The 2'-acetylating enzyme in some strains of P. stuartii can be induced to high levels of activity by exposure to gentamicin or netilmicin.