Evaluation of AISI Type 304 stainless steel as a suitable surface material for evaluating the efficacy of peracetic acid-based disinfectants against Clostridium difficile spores.

Disinfectants play an important role in controlling microbial contamination on hard surfaces in hospitals. The effectiveness of disinfectants in real life can be predicted by laboratory tests that measure killing of microbes on carriers. The modified Quantitative Disk Carrier Test (QCT-2) is a standard laboratory method that employs American Iron and Steel Institute (AISI) Type 430 stainless steel carriers to measure hospital disinfectant efficacy against Clostridium difficile spores. The formation of a rust-colored precipitate was observed on Type 430 carriers when testing a peracetic acid (PAA)-based disinfectant with the QCT-2 method. It was hypothesized that the precipitate was indicative of corrosion of the Type 430 carrier, and that corrosion could impact efficacy results. The objective of this study was to compare the suitability of AISI Type 430 to Type 304 stainless steel carriers for evaluating PAA-based disinfectants using the QCT-2 method. Type 304 is more corrosion-resistant than Type 430, is ubiquitous in healthcare environments, and is used in other standard methods. Suitability of the carriers was evaluated by comparing their impacts on efficacy results and PAA degradation rates. In efficacy tests with 1376 ppm PAA, reductions of C. difficile spores after 5, 7 and 10 minutes on Type 430 carriers were at least about 1.5 log10 lower than reductions on Type 304 carriers. In conditions simulating a QCT-2 test, PAA concentration with Type 430 carriers was reduced by approximately 80% in 10 minutes, whereas PAA concentration in the presence of Type 304 carriers remained stable. Elemental analyses of residues on each carrier type after efficacy testing were indicative of corrosion on the Type 430 carrier. Use of Type 430 stainless steel carriers for measuring the efficacy of PAA-based disinfectants should be avoided as it can lead to an underestimation of real life sporicidal efficacy. Type 304 stainless steel carriers are recommended as a suitable alternative.

Phylogenetic relationships among clonal groups of extraintestinal pathogenic Escherichia coli as assessed by multi-locus sequence analysis.

The evolutionary origins of extraintestinal pathogenic Escherichia coli (ExPEC) remain uncertain despite these organisms' relevance to human disease. A valid understanding of ExPEC phylogeny is needed as a framework against which the observed distribution of virulence factors and clinical associations can be analyzed. Accordingly, phylogenetic relationships were defined by multi-locus sequence analysis among 44 representatives of selected ExPEC clonal groups and the E. coli Reference (ECOR) collection. Recombination, which significantly obscured the phylogenetic signal for several strains, was dealt with by excluding strains or specific sequences. Conflicting overall phylogenies, and internal phylogenies for virulence-associated phylogenetic group B2, were inferred depending on the specific dataset (i.e., how extensively purged of recombination), outgroup (Salmonella enterica and/or Escherichia fergusonii), and analysis method (neighbor joining, maximum parsimony, maximum likelihood, or Bayesian likelihood). Nonetheless, the major E. coli phylogenetic groups A, B1, and B2 were consistently well resolved, as was a major sub-component of group D and an ECOR 37-O157:H7 clade. Moreover, nine important ExPEC clonal groups within groups B2 and D, characterized by serotypes O6:K2:H1, O18:K1:H7, O6:H31, and O4:K+:H+ (from group B2), and O1:K1:H-, O7:K1:H-, O157:K+:H (non-7), O15:K52:H1, and O11/17/77:K52:H18 ("clonal group A") (from group D), were consistently well resolved, regardless of clinical background (cystitis, pyelonephritis, neonatal meningitis, sepsis, or fecal), host group, geographical origin, and virulence profile. Among the group B2-derived clonal groups the O6:K2:H1 clade appeared basal. Within group D, "clonal group A" and the O15:K52:H1 clonal group were consistently placed with ECOR 47 and ECOR 44, respectively, as nearest neighbors. These findings clarify phylogenetic relationships among key ExPEC clonal groups but also emphasize that recombination appears to obscure the oldest evolutionary relationships, despite extensive targeted sequencing and use of a wide range of analysis techniques.

Bacterial characteristics in relation to clinical source of Escherichia coli isolates from women with acute cystitis or pyelonephritis and uninfected women.

Characteristics differentiating Escherichia coli strains that cause cystitis or pyelonephritis from fecal E. coli remain incompletely defined, particularly among adult women in the United States. Accordingly, phylogenetic group, O antigens, and virulence factors (VFs) were analyzed among 329 E. coli isolates from the mid-to-late 1990s from women in the United States with acute pyelonephritis (n = 170), cystitis (n = 83), or no infection (fecal; n = 76). Compared with fecal and cystitis isolates, pyelonephritis isolates exhibited a greater prevalence of phylogenetic group B2, most virulence-associated O antigens, and most VFs and had higher VF scores. In contrast, cystitis and fecal isolates differed minimally. By stepwise multivariable logistic regression, significant (P < or = 0.015) predictors of cystitis and/or pyelonephritis (versus fecal) included afa/dra (Dr-binding adhesins), ibeA (invasion of brain endothelium), iha (putative adhesin-siderophore), malX (pathogenicity island marker), the O75 antigen, papEF (P fimbriae), papG allele II (P adhesin variant), group B2, and sfa/foc (S and F1C fimbriae). However, virulence profiles overlapped considerably among source groups and varied greatly within each group. E. coli "clonal group A" (CGA) and the O2:K5/K7:H1 and O75:K+ clonal groups were significantly associated with cystitis and/or pyelonephritis. These findings identify potential vaccine targets, suggest that urovirulence is multiply determined, and confirm the urovirulence of specific E. coli clonal groups, including recently recognized CGA.