Cellular and Molecular Mechanisms of Toxicity of Ingested Titanium Dioxide Nanomaterials.

An exponential increase in products containing titanium dioxide nanomaterials (TiO2), in agriculture, food and feed industry, lead to increased oral exposure to these nanomaterials (NMs). Thus, the gastrointestinal tract (GIT) emerges as a possible route of exposure that may drive systemic exposure, if the intestinal barrier is surpassed. NMs have been suggested to produce adverse outcomes, such as genotoxic effects, that are associated with increased risk of cancer, leading to a concern for public health. However, to date, the differences in the physicochemical characteristics of the NMs studied and other variables in the test systems have generated contradictory results in the literature. Processes like human digestion may change the NMs characteristics, inducing unexpected toxic effects in the intestine. Using TiO2 as case-study, this chapter provides a review of the works addressing the interactions of NMs with biological systems in the context of intestinal tract and digestion processes, at cellular and molecular level. The knowledge gaps identified suggest that the incorporation of a simulated digestion process for in vitro studies has the potential to improve the model for elucidating key events elicited by these NMs, advancing the nanosafety studies towards the development of an adverse outcome pathway for intestinal effects.

Overview of Adverse Outcome Pathways and Current Applications on Nanomaterials.

Nanomaterials (NMs) have important and useful applications in chemical industry, electronics, pharmaceuticals, food and others. Their rapid proliferation presents a dilemma to regulators regarding hazard identification and increased concerns for public health.The Adverse Outcome Pathways (AOPs) are innovative central elements of a toxicological knowledge framework, developed for supporting chemical risk assessment based on mechanistic reasoning. AOPs describe a sequence of causally linked events at different levels of biological organisation, triggered by exposure to a stressor (like chemicals or NMs) leading to an adverse health effect in humans or wildlife. The integrative analysis of the cellular and molecular mechanisms of nanotoxicity towards the identification of connected adverse outcomes drives a sequential line - an AOP landscape definition. Each defined AOP is available for crossing data, linking known and unknown landscapes, reducing the reliance on animal studies, associated costs and ethical issues. NMs have unique properties, with specific associated toxicological challenges, which may represent unknown AOP landscapes.In this chapter, an overview of AOPs as important novel strategic tools in nanotoxicology is presented, highlighting the current applications in hazard identification and human health risk assessment.

Structure and Function of the PiuA and PirA Siderophore-Drug Receptors from Pseudomonas aeruginosa and Acinetobacter baumannii.

The outer membrane of Gram-negative bacteria presents an efficient barrier to the permeation of antimicrobial molecules. One strategy pursued to circumvent this obstacle is to hijack transport systems for essential nutrients, such as iron. BAL30072 and MC-1 are two monobactams conjugated to a dihydroxypyridone siderophore that are active against Pseudomonas aeruginosa and Acinetobacter baumannii Here, we investigated the mechanism of action of these molecules in A. baumannii We identified two novel TonB-dependent receptors, termed Ab-PiuA and Ab-PirA, that are required for the antimicrobial activity of both agents. Deletion of either piuA or pirA in A. baumannii resulted in 4- to 8-fold-decreased susceptibility, while their overexpression in the heterologous host P. aeruginosa increased susceptibility to the two siderophore-drug conjugates by 4- to 32-fold. The crystal structures of PiuA and PirA from A. baumannii and their orthologues from P. aeruginosa were determined. The structures revealed similar architectures; however, structural differences between PirA and PiuA point to potential differences between their cognate siderophore ligands. Spontaneous mutants, selected upon exposure to BAL30072, harbored frameshift mutations in either the ExbD3 or the TonB3 protein of A. baumannii, forming the cytoplasmic-membrane complex providing the energy for the siderophore translocation process. The results of this study provide insight for the rational design of novel siderophore-drug conjugates against problematic Gram-negative pathogens.

Identification of NDM-1 in a Putatively Novel Acinetobacter Species ("NB14") Closely Related to Acinetobacter pittii.

In this study, we describe the molecular characterization of a plasmid-located blaNDM-1 harbored by an Acinetobacter clinical isolate recovered from a patient in Turkey that putatively constitutes a novel Acinetobacter species, as shown by its distinct ARDRA (amplified 16S ribosomal DNA restriction analysis) profile and molecular sequencing techniques. blaNDM-1 was carried by a conjugative plasmid widespread among non-baumannii Acinetobacter isolates, suggesting its potential for dissemination before reaching more clinically relevant Acinetobacter species.

Serotype 5 pneumococci causing invasive pneumococcal disease outbreaks in Barcelona, Spain (1997 to 2011).

In this study, we analyzed the clinical and molecular epidemiology of invasive serotype 5 (Ser5) pneumococcal isolates in four teaching hospitals in the Barcelona, Spain, area (from 1997 to 2011). Among 5,093 invasive pneumococcal isolates collected, 134 (2.6%) Ser5 isolates were detected. Although the overall incidence of Ser5-related invasive pneumococcal disease (IPD) was low (0.25 cases/100,000 inhabitants), three incidence peaks were detected: 0.63/100,000 in 1999, 1.15/100,000 in 2005, and 0.37/100,000 in 2009. The rates of Ser5 IPD were higher among young adults (18 to 64 years old) and older adults (>64 years old) in the first two peaks, whereas they were higher among children in 2009. The majority (88.8%) of the patients presented with pneumonia. Comorbid conditions were present in young adults (47.6%) and older adults (78.7%), the most common comorbid conditions being chronic obstructive pulmonary disease (20.6% and 38.3%, respectively) and cardiovascular diseases (11.1% and 38.3%, respectively). The mortality rates were higher among older adults (8.5%). All Ser5 pneumococci tested were fully susceptible to penicillin, cefotaxime, erythromycin, and ciprofloxacin. The resistance rates were 48.5% for co-trimoxazole, 6.7% for chloramphenicol, and 6% for tetracycline. Two major related sequence types (STs), ST1223 (n = 65) and ST289 (n = 61), were detected. The Colombia(5)-ST289 clone was responsible for all the cases in the Ser5 outbreak in 1999, whereas the ST1223 clone accounted for 73.8% and 61.5% of the isolates in 2005 and 2009, respectively. Ser5 pneumococci are a frequent cause of IPD outbreaks in the community and involve children and adults with or without comorbidities. The implementation of the new pneumococcal conjugated vaccines (PCV10 and PCV13) might prevent such outbreaks.

Investigation of the genotoxicity of digested titanium dioxide nanomaterials in human intestinal cells.

The widespread use of titanium dioxide nanomaterials (TiO2 NMs) in food and consumer products such as toothpaste or food contact materials, suggests the relevance of human oral exposure to these nanomaterials (NMs) and raises the possibility of adverse effects in the gastrointestinal tract (GIT). We previously showed that the in vitro digestion of TiO2 NMs may increase their toxicity in intestinal cells. In this work, we analyzed the genotoxicity and the intracellular reactive oxygen species induction by physiologically relevant concentrations of three different TiO2 NMs (NM-102, NM-103 and NM-105) in Caco-2 and HT29-MTX-E12 intestinal cells, while considering the potential influence of the digestion process in the NMs' physiochemical characteristics. The results evidenced a DNA-damaging effect dependent on the NM, more relevant for the rutile/anatase NM-105, possibly due to its lower hydrodynamic size in the cells medium. In addition, the results of the micronucleus assay suggest effects on chromosomal integrity, an indicator of cancer risk, in the HT29-MTX-E12 cells, for all the tested TiO2 NMs, especially after the in vitro digestion. This work supports the evidence for concerns on the use of TiO2 NMs as a food additive, recently reported by EFSA, and for their use in applications in consumer products that may drive human exposure through ingestion.

Adverse Outcome Pathways Associated with the Ingestion of Titanium Dioxide Nanoparticles-A Systematic Review.

Titanium dioxide nanoparticles (TiO2-NPs) are widely used, and humans are exposed through food (E171), cosmetics (e.g., toothpaste), and pharmaceuticals. The oral and gastrointestinal (GIT) tract are the first contact sites, but it may be systemically distributed. However, a robust adverse outcome pathway (AOP) has not been developed upon GIT exposure to TiO2-NPs. The aim of this review was to provide an integrative analysis of the published data on cellular and molecular mechanisms triggered after the ingestion of TiO2-NPs, proposing plausible AOPs that may drive policy decisions. A systematic review according to Prisma Methodology was performed in three databases of peer-reviewed literature: Pubmed, Scopus, and Web of Science. A total of 787 records were identified, screened in title/abstract, being 185 used for data extraction. The main endpoints identified were oxidative stress, cytotoxicity/apoptosis/cell death, inflammation, cellular and systemic uptake, genotoxicity, and carcinogenicity. From the results, AOPs were proposed where colorectal cancer, liver injury, reproductive toxicity, cardiac and kidney damage, as well as hematological effects stand out as possible adverse outcomes. The recent transgenerational studies also point to concerns with regard to population effects. Overall, the findings further support a limitation of the use of TiO2-NPs in food, announced by the European Food Safety Authority (EFSA).

Characterization of invasive Pneumococci of serogroup 6 from adults in Barcelona, Spain, in 1994 to 2008.

A total of 91 of 1,480 invasive isolates (6.1%) collected from adults in Barcelona, Spain, in the period of 1994 to 2008 were of serogroup 6 (6B, 47 isolates; 6A, 28; and 6C, 16). Throughout this period, serotype 6B (Spain(6B)-ST90) decreased, and serotype 6A remained stable. An increase in serotype 6C (ST224) in the 2004-2008 period was observed.

Trends of invasive serotype 6C pneumococci in Spain: emergence of a new lineage.

OBJECTIVES: To analyse the epidemiology of isolates of serotype 6C among invasive pneumococci isolated from children and adults in Spain between 1997 and 2009, and to characterize serotype 6C clones and macrolide and quinolone resistance mechanisms. METHODS: Antimicrobial susceptibility was determined following CLSI guidelines. Phenotypic characterization of macrolide-resistant isolates was performed by the double disc diffusion method. Genes associated with resistance to erythromycin and tetracycline were sought by PCR, while quinolone resistance was analysed by restriction fragment length polymorphism of the quinolone resistance-determining region. Isolates were typed by multilocus sequence typing. RESULTS: Seven hundred and eighty-nine of 866 serotype 6A pneumococci collected from 1997 to 2009 were available. Of these, 213 (27.0%) were serotype 6C; 16/163 (9.8%) in the 1997-2001 (pre-PCV7) period, 37/322 (11.5%) in the 2002-05 (early-PCV7) period and 160/381 (42.0%) in the 2006-09 (late-PCV7) period. The overall proportions of serotype 6C increased from 0.1% (pre-PCV7) to 1% (late-PCV7) for paediatric isolates and from 0.3% to 1.7% among adult isolates. A major serotype 6C lineage (ST224/ST1150/ST4821), accounting for 66.7% of the isolates, was identified across the whole period. In the late-PCV7 period the antimicrobial non-susceptibility of serotype 6C increased in association with the emergence of the ST386/ST4310/ST4825 lineage, which carried a Tn6002 transposon [erm(B) and tet(M) genes]. CONCLUSIONS: Serotype 6C pneumococci were identified in Spain during the period 1997-2009. The increase in serotype 6C in the late-PCV7 period was associated with the spread of the ST224/ST1150/ST4821 lineage and the emergence of the ST386/ST4310/ST4825 lineage.

Emergence of ciprofloxacin-nonsusceptible Streptococcus pyogenes isolates from healthy children and pediatric patients in Portugal.

We describe 66 ciprofloxacin-nonsusceptible Streptococcus pyogenes isolates recovered from colonized and infected children. The ParC S79A substitution was frequent and associated with the emm6/sequence type 382 (emm6/ST382) lineage. The ParC D83G substitution was detected in two isolates (emm5/ST99 and emm28/ST52 lineages). One isolate (emm89/ST101) had no quinolone resistance-determining region codon substitutions or other resistance mechanisms. Five of 66 isolates were levofloxacin resistant. Although fluoroquinolones are not used in children, they may be putative disseminators of fluoroquinolone-nonsusceptible strains in the community.

Serotype and genotype replacement among macrolide-resistant invasive Pneumococci in adults: mechanisms of resistance and association with different transposons.

The aim of this study was to analyze trends in adult invasive pneumococcal disease (IPD) due to macrolide-resistant strains and to study the evolution of serotypes, genotypes, and macrolide-resistant determinants of strains collected in a prospective study between 1999 and 2007 in Barcelona, Spain. IPD due to macrolide-resistant strains of serotypes included in the 7-valent conjugate vaccine (PCV7) decreased from 2.16/100,000 (pre-PCV7 period, 1999 to 2001) to 0.80/100,000 (late-PCV7 period, 2005 to 2007) (P = 0.001), whereas IPD due to macrolide-resistant strains of non-PCV7 serotypes increased from 1.08/100,000 to 2.83/100,000 (P < 0.001). These changes were related to a fall of clones of PCV7 serotypes (ST81 [P < 0.05], ST90, ST315, and ST17) and an increase in new clones of serotypes 19A and 24F (ST230) and 33F (ST717) in the late-PCV7 period. The most common phenotype was MLS(B) (90.9%), related to the erm(B) gene. The frequent association between MLS(B) phenotype and tetracycline resistance [tet(M) gene], was related to transposons of the Tn916-family such as Tn6002 or Tn3872. In conclusion, overall adult IPD rates due to macrolide-resistant pneumococci stabilized between 1999 and 2007 in Barcelona. The decrease in macrolide-resistant PCV7 pneumococci was balanced by the increase in macrolide-resistant non-PCV7 pneumococci.

Molecular characterization of macrolide- and multidrug-resistant Streptococcus pyogenes isolated from adult patients in Barcelona, Spain (1993-2008).

OBJECTIVES: The increase in erythromycin resistance among Streptococcus pyogenes isolates is a cause for concern. We analysed trends in macrolide resistance, phenotypes, genotypes, resistance determinants and transposons among erythromycin-resistant S. pyogenes isolates collected from adults in a Barcelona hospital (1993-2008). METHODS: Antibiotic susceptibility was studied by microdilution. Molecular typing was performed by PFGE, emm typing and multilocus sequence typing (MLST). Macrolide resistance genes and those related to the Tn916 family of transposons were detected by PCR. RESULTS: Ninety-nine (18.3%) of 541 isolates were erythromycin resistant. Erythromycin resistance rates progressively increased from 0% (0/24) in 1993-1994 to 34.2% (50/146, P < 0.001) in 2001-2004, then falling to 7.4% (8/108, P = 0.02) in 2007-2008. Sixty-six erythromycin-resistant isolates were available for molecular studies. Of these, 26 had an M phenotype [mef(A)] and 40 had an MLS(B) phenotype [erm(B), n = 33; and erm(TR), n = 7]. Among M-phenotype isolates, the most frequent genotypes (88.5%) were emm4-ST39, emm6-ST382 and emm75-ST49, whereas genotypes emm11-ST403, emm28-ST52 and emm25-ST350 accounted for 72.5% of MLS(B)-phenotype isolates. Twenty-five isolates harboured both erm(B) and tet(M) genes related to the Tn916 family of transposons, Tn6002 being the most frequent. Ten isolates (10.1%) were ciprofloxacin non-susceptible, related to the emm6-ST382 clone with a ParC S79A change. CONCLUSIONS: The peak of macrolide resistance rates among S. pyogenes observed in the 2001-2004 period was associated with an increase in the MLS(B) phenotype caused by the spread of emm11-ST403 and emm28-ST52 clones harbouring transposons of the Tn916 family. However, erythromycin resistance rates decreased significantly in the 2007-2008 period.

Analysis of the Characteristics and Cytotoxicity of Titanium Dioxide Nanomaterials Following Simulated In Vitro Digestion.

Several metallic nanomaterials (NMs), such as titanium dioxide nanomaterials (TiO2), present beneficial properties with a broad range of innovative applications. The human population is exposed to TiO2, particularly by ingestion, due to its increasing use as a food additive and inclusion in dietary supplements and food packaging materials. Whether this oral exposure may lead to adverse local or systemic outcomes has been the subject of research, but studies have generated contradictory results, reflecting differences in the physicochemical properties of the TiO2 studied, effects of the surrounding matrix, and modifications during digestion. This work aimed to investigate the toxic effects of three different TiO2 NMs (NM-103, NM-103 and NM-105) on the gastrointestinal tract cells, Caco-2 and HT29-MTX-E12, after the use of the standardized static INFOGEST 2.0 in vitro digestion method to mimic human digestion of TiO2, contributing to hazard assessment. The results show that, for one of the digested TiO2 NMs studied (NM-105), a more pronounced toxicity occurs after exposure of HT29-MTX-E12 intestinal cells, as compared to undigested NM, concomitantly with subtle changes in characteristics of the NM. Thus, the inclusion of the digestion simulation in the safety evaluation of ingested NMs through in vitro bioassays can better integrate the modifications that NMs suffer in the organism. It is expected that such an approach will reduce uncertainties in the hazard assessment of ingested NMs for human health.

Epidemiology of invasive pneumococcal disease among adult patients in barcelona before and after pediatric 7-valent pneumococcal conjugate vaccine introduction, 1997-2007.

BACKGROUND: A dramatic decrease in the incidence of invasive pneumococcal disease (IPD) was observed among children and adults in the United States after the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7). Little is known about the incidence of IPD after PCV7 licensure in Europe. The objective of this study was to examine changes in the prevalence of IPD among adults in the PCV7 era. METHODS: We undertook a prospective study involving adults with IPD who required hospital admission in the southern area of Barcelona, Spain. Three periods were studied: the pre-PCV7 period (1997-2001), the early PCV7 period (2002-2004), and the late PCV7 period (2005-2007). RESULTS: A total of 1007 episodes of IPD were observed. Rates of IPD among adults increased from 13.9 to 14.6 episodes per 100,000 population between the pre-PCV7 period and the early PCV7 period (P = .6) and then to 19.55 episodes per 100,000 population in the late PCV7 period (P < .001). The rates of IPD among adults due to non-PCV7 serotypes increased from 8.4 to 9.7 episodes per 100,000 population between the pre-PCV7 period and the early PCV7 period (P = .15) and then to 15.3 episodes per 100,000 population in the late PCV7 period (P < .001); IPD due to PCV7 serotypes decreased from 5.6 to 4.9 episodes per 100,000 population between the pre-PCV7 period and the early PCV7 period (P = .3), then to 4.3 episodes per 100,000 population in the late PCV7 period (P = .056). Among people aged > or = 65 years, IPD due to PCV7 serotypes decreased from 19.5 to 14.6 episodes per 100,000 population between the pre-PCV7 period and the early PCV7 period (P = .13), then to 12.3 episodes per 100,000 population in the late PCV7 period (P = .02). A decrease in the prevalence of antibioticresistant pneumococci in the late PCV7 period was associated with a decrease in the prevalence of multidrugresistant PCV7 clones (Spain(23F)-ST81, Spain(6B)-ST90, and ST88(19F)) and an increase in the prevalence of non-PCV7 antibiotic-susceptible clones (ST306(1), ST191(7F), ST989(12F), and ST433(22F)). CONCLUSIONS: Rates of IPD among adults increased in Barcelona in the late PCV7 period, coinciding with a clonal expansion of non-PCV7 serotypes. In contrast, rates of IPD caused by PCV7 serotypes decreased among people aged > or = 65 years, which suggests the development of a herd immunity.

Emergence of a multidrug-resistant clone (ST320) among invasive serotype 19A pneumococci in Spain.

OBJECTIVES: Multidrug-resistant Streptococcus pneumoniae isolates of serotype 19A have emerged all over the world in recent years. The aim of this study was to characterize highly penicillin-resistant pneumococcal strains of the 19A serotype, collected in Spain from 1997 to 2007 from patients with invasive disease. METHODS: Antibiotic susceptibility was studied by microdilution. All penicillin-resistant pneumococci were typed by PFGE and selected strains were studied by multilocus sequence typing (MLST). The presence of genes related to the Tn916 family of transposons was investigated by PCR. RESULTS: From a total of 1197 invasive pneumococcal isolates of serotype 19A received at the Spanish Reference Laboratory between 1997 and 2007, 51 (4.3%) strains showed high-level resistance to penicillin (MICs of 2-4 mg/L). These 51 isolates belonged to three multiresistant clones related to sequence type (ST)81 (n = 21), ST320 (n = 19) and ST276 (n = 11). All 51 serotype 19A pneumococci were tetracycline-resistant and had the tet(M) gene, and 41 strains were macrolide-resistant, harbouring the erm(B) gene. The presence of int and xis genes was detected in all strains associated with other genes of the Tn916 family. CONCLUSIONS: The rise in penicillin-resistant serotype 19A invasive pneumococci in Spain was associated with the emergence and clonal spread of two worldwide-disseminated multiresistant clones (ST276 and ST320). The Spain(23F)-1-19A (ST81) clone remained stable throughout the study period. Multidrug resistance was associated with transposons of the Tn916 family.

Diversity of pneumococcal surface protein A (PspA) among prevalent clones in Spain.

BACKGROUND: PspA is recognized as a major pneumococcal virulence factor and a possible vaccine candidate. The aim of this study was to analyze the PspA family and clade distribution among 112 Spanish pneumococci representatives of dominant clones among patients with invasive disease (n = 66) and nasopharyngeal healthy carriage in children (n = 46). RESULTS: PspA family 2 was predominant among invasive (63.6%) and carriage (54.3%) pneumococcal isolates. No PspA family 3 isolates were detected and only one strain was PspA negative. Although four clonal complexes contained strains of different clades, a clear association between clade and multi locus sequence typing results was found. Clades 1, 3 and 4 were associated with a wide variety of sequence types (ST) related to multiresistant and antibiotic-susceptible worldwide-disseminated clones. Clade 1 was associated with Spain 6B-ST90, Spain 14-ST18, Colombia 5-ST289, Sweden 1-ST306, Denmark 14-ST230 and Sweden 1-ST304 clones. Clade 3 was associated with Spain 23F-ST81, Spain 9V-ST156, Tennessee 14-ST67, Netherlands 3-ST180 and Netherlands 7F-ST191 clones. Clade 4 was related to Sweden 15A-ST63, Netherlands 18C-ST113 and Greece 21-ST193 clones. In contrast, PspA clade was not related to serotype, age or clinical origin of the isolates. CONCLUSION: PspA clades were associated with genotypes. PspA family 2 and family 1 were dominant among major Spanish pneumococcal clones isolated from patients with invasive disease and nasopharyngeal carriage in children.

Relationship Between Different Resistance Mechanisms and Virulence in Acinetobacter baumannii.

Aim: This study analyzed the virulence of several Acinetobacter baumannii strains expressing different resistance mechanisms using the Caenorhabditis elegans infection model. Results: Strains susceptible/resistant to carbapenems (presenting class D (OXA-23, OXA-24), class B metallo-ß-lactamase (MBL) (NDM-1), penicillin binding protein (PBP) altered and decreased expression of Omp 33-36 kDa) and isogenic A. baumannii strains susceptible/resistant to colistin (presenting loss of lipopolysaccharide (LPS) and pmrA mutations) were included to evaluate the virulence using the C. elegans infection model. The nematode killing assay, bacterial ingestion in worms, and bacterial lawn avoidance assay were performed with the Fer-15 mutant line. A. baumannii strains generally presented low virulence, showing no difference between carbapenem-resistant strains (expressing class D, MBLs, or altered PBP) and their isogenic susceptible strains. In contrast, the absence of the Omp 33-36 kDa protein in the knockout was associated with a decrease of virulence, and a significant difference was observed between colistin-resistant mutants and their susceptible counterpart when the mechanism of resistance was associated with the loss of LPS but not with its modification. Conclusions: Resistance to carbapenems in A. baumannii associated with the production of OXA-type or NDM-type enzymes does not seem to affect their virulence in the C. elegans infection model. In contrast, the presence of Omp 33-36 kDa, and high level resistance to colistin related with the loss of LPS, might contribute with the virulence profile in A. baumannii.

Relationship Between Biofilm Formation and Antimicrobial Resistance in Gram-Negative Bacteria.

Gram-negative microorganisms are a significant cause of infection in both community and nosocomial settings. The increase, emergence, and spread of antimicrobial resistance among bacteria are the most important health problems worldwide. One of the mechanisms of resistance used by bacteria is biofilm formation, which is also a mechanism of virulence. This study analyzed the possible relationship between antimicrobial resistance and biofilm formation among isolates of three Gram-negative bacteria species. Several relationships were found between the ability to form biofilm and antimicrobial resistance, being different for each species. Indeed, gentamicin and ceftazidime resistance was related to biofilm formation in Escherichia coli, piperacillin/tazobactam, and colistin in Klebsiella pneumoniae, and ciprofloxacin in Pseudomonas aeruginosa. However, no relationship was observed between global resistance or multidrug-resistance and biofilm formation. In addition, compared with other reported data, the isolates in the present study showed higher rates of antimicrobial resistance. In conclusion, the acquisition of specific antimicrobial resistance can compromise or enhance biofilm formation in several species of Gram-negative bacteria. However, multidrug-resistant isolates do not show a trend to being greater biofilm producers than non-multiresistant isolates.

lytA-based identification methods can misidentify Streptococcus pneumoniae.

During surveillance studies we detected, among over 1500 presumptive pneumococci, 11 isolates displaying conflicting or novel results when characterized by widely accepted phenotypic (optochin susceptibility and bile solubility) and genotypic (lytA-BsaAI-RFLP and MLST) identification methods. We aimed to determine the genetic basis for the unexpected results given by lytA-BsaAI-RFLP and investigate the accuracy of the WHO recommended lytA real-time PCR assay to classify these 11 isolates. Three novel lytA-BsaAI-RFLP signatures were found (one in pneumococcus and two in S. mitis). In addition, one pneumococcus displayed the atypical lytA-BsaAI-RFLP signature characteristic of non-pneumococci and two S. pseudopneumoniae displayed the typical lytA-BsaAI-RFLP pattern characteristic of pneumococci. lytA real-time PCR misidentified these three isolates. In conclusion, identification of pneumococci by lytA real-time PCR, and other lytA-based methodologies, may lead to false results. This is of particular relevance in the increasingly frequent colonization studies relying solely on culture-independent methods.

Disease isolates of Streptococcus pseudopneumoniae and non-typeable S. pneumoniae presumptively identified as atypical S. pneumoniae in Spain.

We aimed to obtain insights on the nature of a collection of isolates presumptively identified as atypical Streptococcus pneumoniae recovered from invasive and non-invasive infections in Spain. One-hundred and thirty-two isolates were characterized by: optochin susceptibility in ambient and CO(2)-enriched atmosphere; bile solubility; PCR-based assays targeting pneumococcal genes lytA, ply, pspA, cpsA, Spn9802, aliB-like ORF2, and a specific 16S rRNA region; multilocus sequence analysis; and antimicrobial susceptibility. By multilocus sequence analysis, 61 isolates were S. pseudopneumoniae, 34 were pneumococci, 13 were S. mitis, and 24 remained unclassified as non-pneumococci. Among S. pseudopneumoniae isolates, 51 (83.6%) were collected from respiratory tract samples; eight isolates were obtained from sterile sources. High frequency of non-susceptibility to penicillin (60.7%) and erythromycin (42.6%) was found. Only 50.8% of the S. pseudopneumoniae isolates displayed the typical optochin phenotype originally described for this species. None harbored the cpsA gene or the pneumococcal typical lytA restriction fragment length polymorphism. The Spn9802 and the specific 16S rRNA regions were detected among the majority of the S. pseudopneumoniae isolates (n = 59 and n = 49, respectively). The ply and pspA genes were rarely found. A high genetic diversity was found and 59 profiles were identified. Among the S. pneumoniae, 23 were capsulated and 11 were non-typeable. Three non-typeable isolates, associated to international non-capsulated lineages, were recovered from invasive disease sources. In conclusion, half of the atypical pneumococcal clinical isolates were, in fact, S. pseudopneumoniae and one-fourth were other streptococci. We identified S. pseudopneumoniae and non-typeable pneumococci as cause of disease in Spain including invasive disease.