Acinetobacter sp: importància com a patogen nosocomial en l'actualitat

El gènere Acinetobacter està format per bacils gramnegatius immòbils àmpliament distribuïts en la natura. Des de la seva descripció, els membres d'aquest gènere han patit nombrosos canvis taxonòmics, en part a causa de l'absència de característiques bioquímiques diferencials. Els avenços en les tècniques d'hibridació d'àcid desoxiribonucleic (DNA) han permès la identificació de 21 grups o genoespècies dins del gènere Acinetobacter. La majoria de laboratoris de microbiologia clínica no disposen de tècniques genètiques, i per tant la identificació es basa en proves fenotípiques tradicionals com la utilització de carbohidrats, el creixement a diferents temperatures (37ºC, 41ºC i 44ºC) i l'hemòlisi, entre d'altres. La principal espèciemassociada a infecció és A. baumannii, mentre que altres espècies com A. Iwoffii o A. haemolyticus s'aïllen amb poca freqüència en les mostres clíniques

Drug-resistant Streptococcus pneumoniae

To the Editor: since the first description of infection caused by β-lactam-resistant Streptococcus pneumoniae, the optimal empirical antibiotic therapy for patients with suspected meningitis caused by this microorganism has remained unknown. Hofmann et al. (Aug. 24 issue)1 reported a 25 percent prevalence of penicillin-resistant S. pneumoniae isolates and a 9 percent prevalence of cephalosporin-resistant isolates among 431 patients with invasive pneumococcal infections in Atlanta. The authors recommended adding vancomycin to the initial therapeutic regimen of patients with suspected pneumococcal meningitis

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

<p>Abstract</p> <p>Background</p> <p>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).</p> <p>Results</p> <p>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, Spain¹⁴-ST18, Colombia⁵-ST289, Sweden¹-ST306, Denmark¹⁴-ST230 and Sweden¹-ST304 clones. Clade 3 was associated with Spain^23F-ST81, Spain^9V-ST156, Tennessee¹⁴-ST67, Netherlands³-ST180 and Netherlands^7F-ST191 clones. Clade 4 was related to Sweden^15A-ST63, Netherlands^18C-ST113 and Greece²¹-ST193 clones. In contrast, PspA clade was not related to serotype, age or clinical origin of the isolates.</p> <p>Conclusion</p> <p>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.</p

Clonal spread of Klebsiella pneumoniae producing OXA-1 betalactamase in a Spanish hospital

Multi-drug resistant Klebsiella pneumoniae isolates are associated with nosocomial infections, in which colonized patients act as a reservoir and source of cross-infection for other patients. In this study, the antimicrobial susceptibility of K. pneumoniae was tested by microdilution using the commercial method MicroScan (Siemens). The genetic relatedness of K. pneumoniae strains was determined by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). PCR experiments were carried out to obtain primer sets and positive PCR products were purified and sequenced. From May 2007 until December 2009, 98 clonally related K. pneumoniae isolates were detected from clinical samples of 38 patients admitted to the University Hospital of Bellvitge, Barcelona, Spain, including 27 admitted to the intensive care unit (ICU). The most important sources of the isolates were: lower respiratory tract (n = 12), urine (n = 12), and blood (n = 11). The strains were resistant to amoxicillin/clavulanic acid, piperacillin/tazobactam, tobramycin, amikacin, and ciprofloxacin, and had diminished susceptibility to cefepime. All the isolates shared a common PFGE pattern related to sequence type 14 after MLST analysis. In K. pneumoniae isolates and their transconjugants, the blaOXA-1 gene was located in the variable region of a class I integron that also contains the aac(6&prime;)Ib-cr gene. Sequencing of the quinolone resistance determinant regions of gyrA and parC revealed a S83F change in GyrA and no changes in ParC. [Int Microbiol 2013; 16(4):227-233]Keywords: Klebsiella pneumoniae &middot; sequence type ST14 &middot; gene blaOXA-1 &middot; integrons &middot; nosocomial outbreak

Molecular characterization of resistance to Rifampicin in an emerging hospital-associated Methicillin-resistant Staphylococcus aureus clone ST228, Spain

Background: Methicillin-resistant S. aureus (MRSA) has been endemic in Hospital Universitari de Bellvitge, Barcelona, since 1990. During the 1990-95 period the Iberian clone (ST-247; SCCmec-I) was dominant. Isolates of clonal complex 5 (ST-125; SCCmec-IV) gradually replaced the Iberian clone from 1996 to 2003. A new multiresistant MRSA phenotype showing rifampicin resistance emerged in 2004 and rapidly increased from 25% in 2004 to 45% in 2006. The aims of this study were i) the molecular characterisation of rifampicin resistant MRSA isolates, ii) the study of the rifampicin resistance expression by disk diffusion, microdilution and E-test, and iii) the analysis of the rpoB gene mutations involved in rifampicin resistance. Results: A sample of representative 108 rifampicin-resistant MRSA isolates belonged to a single PFGE genotype, ST-228, SCCmec type I and spa type t041. Of 108 isolates, 104 (96%) had a low-level rifampicin resistance (MICs, 2 to 4 mg/L) and 4 a high-level rifampicin resistance (MICs, 128 - ≥ 256 mg/L). Disk diffusion and E-test methods failed to identify a low-level rifampicin resistance in 20 and 12 isolates, respectively. A low-level rifampicin resistance was associated with amino acid substitution 481His/Asn in the beta-subunit of RNA polymerase. Isolates with a high-level rifampicin resistance carried additional mutations in the rpoB gene. Conclusions: The emergence of MRSA clone ST228-SCCmec I, related to the Southern Germany clone, involved a therapeutical challenge for treating serious MRSA infections. Decreased susceptibility to rifampicin in MRSA strains of ST228-SCCmecI was associated with one or two specific mutations in the rpoB gene. One fifth of isolates with low-level rifampicin-resistance were missed by the diffusion methods

Emerging, non-PCV13 serotypes 11A and 35B of Streptococcus pneumoniae show high potential for biofilm formation in vitro

Background: Since the use of pneumococcal conjugate vaccines PCV7 and PCV13 in children became widespread, invasive pneumococcal disease (IPD) has dramatically decreased. Nevertheless, there has been a rise in incidence of Streptococcus pneumoniae non-vaccine serotypes (NVT) colonising the human nasopharynx. Nasopharyngeal colonisation, an essential step in the development of S. pneumoniae-induced IPD, is associated with biofilm formation. Although the capsule is the main pneumococcal virulence factor, the formation of pneumococcal biofilms might, in fact, be limited by the presence of capsular polysaccharide (CPS). Methodology/Principal Findings: We used clinical isolates of 16 emerging, non-PCV13 serotypes as well as isogenic transformants of the same serotypes. The biofilm formation capacity of isogenic transformants expressing CPSs from NVT was evaluated in vitro to ascertain whether this trait can be used to predict the emergence of NVT. Fourteen out of 16 NVT analysed were not good biofilm formers, presumably because of the presence of CPS. In contrast, serotypes 11A and 35B formed >45% of the biofilm produced by the non-encapsulated M11 strain. Conclusions/Significance This study suggest that emerging, NVT serotypes 11A and 35B deserve a close surveillance

Molecular characterization of Streptococcus pneumoniae invasive serotype 19A isolates from adults in two Spanish regions (1994-2009)

From 1994 to 2009, the incidence of invasive serotype 19A pneumococci isolated from adults in Barcelona and San Sebastian almost doubled every 4 years. Genotyping of the 167 invasive isolates studied showed serotype 19A to be highly heterogeneous, with 35 different sequence types (STs) and a different clonal structure in each region and time period. Multiresistance, defined as non-susceptibility to three or more antimicrobials, was found in 86 (51.5%) isolates. The most frequent ST was the multidrug-resistant ST276 (n = 28), which is a single-locus variant of the Denmark14-ST230 global clone. The ST276 clone, only present in San Sebastian before 2001, was successfully disseminated from 2002 in both cities and was the main contributor to the overall increase of serotype 19A infections

A Novel Typing Method for Streptococcus pneumoniae Using Selected Surface Proteins

The diverse pneumococcal diseases are associated with different pneumococcal lineages, or clonal complexes. Nevertheless, intra-clonal genomic variability, which influences pathogenicity, has been reported for surface virulence factors. These factors constitute the communication interface between the pathogen and its host and their corresponding genes are subjected to strong selective pressures affecting functionality and immunogenicity. First, the presence and allelic dispersion of 97 outer protein families were screened in 19 complete pneumococcal genomes. Seventeen families were deemed variable and were then examined in 216 draft genomes. This procedure allowed the generation of binary vectors with 17 positions and the classification of strains into surfotypes. They represent the outer protein subsets with the highest inter-strain discriminative power. A total of 116 non-redundant surfotypes were identified. Those sharing a critical number of common protein features were hierarchically clustered into 18 surfogroups. Most clonal complexes with comparable epidemiological characteristics belonged to the same or similar surfogroups. However, the very large CC156 clonal complex was dispersed over several surfogroups. In order to establish a relationship between surfogroup and pathogenicity, the surfotypes of 95 clinical isolates with different serogroup/serotype combinations were analyzed. We found a significant correlation between surfogroup and type of pathogenic behavior (primary invasive, opportunistic invasive, and non-invasive). We conclude that the virulent behavior of S. pneumoniae is related to the activity of collections of, rather than individual, surface virulence factors. Since surfotypes evolve faster than MLSTs and directly reflect virulence potential, this novel typing protocol is appropriate for the identification of emerging clones.This work was supported by a Miguel Servet contract from the Spanish Ministry of Health to AM, Plan Nacional de I+D+I of the Ministry of Science and Innovation (BIO2011-25343, BIO2014-555462-R, SAF2012-39444-C02), Fondo de Investigaciones Sanitarias de la Seguridad Social (PI11/00763) and Fondo Europeo de Desarrollo Regional (FEDER). CIBER Enfermedades Respiratorias is an initiative of the Instituto de Salud Carlos III.Peer reviewedPeer Reviewe

Clonal spread of Klebsiella pneumoniae producing OXA-1 betalactamase in a Spanish hospital

Multi-drug resistant Klebsiella pneumoniae isolates are associated with nosocomial infections, in which colonized patients act as a reservoir and source of cross-infection for other patients. In this study, the antimicrobial susceptibility of K. pneumoniae was tested by microdilution using the commercial method MicroScan (Siemens). The genetic relatedness of K. pneumoniae strains was determined by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). PCR experiments were carried out to obtain primer sets and positive PCR products were purified and sequenced. From May 2007 until December 2009, 98 clonally related K. pneumoniae isolates were detected from clinical samples of 38 patients admitted to the University Hospital of Bellvitge, Barcelona, Spain, including 27 admitted to the intensive care unit (ICU). The most important sources of the isolates were: lower respiratory tract (n = 12), urine (n = 12), and blood (n = 11). The strains were resistant to amoxicillin/clavulanic acid, piperacillin/tazobactam, tobramycin, amikacin, and ciprofloxacin, and had diminished susceptibility to cefepime. All the isolates shared a common PFGE pattern related to sequence type 14 after MLST analysis. In K. pneumoniae isolates and their transconjugants, the bla(OXA-1) gene was located in the variable region of a class I integron that also contains the aac(6')Ib-cr gene. Sequencing of the quinolone resistance determinant regions of gyrA and parC revealed a S83F change in GyrA and no changes in ParC

Oropharyngeal colonization by nontypeable Haemophilus influenzae among healthy children attending day care centers

Haemophilus influenzae colonizes the upper respiratory tract and can spread causing otitis and sinusitis. This work aimed to study the oropharyngeal carriage rate in healthy <5-year-old children attending day care centers in Oviedo, Spain in two consecutive years (January to March 2004-2005). The carriage rate was 42% (400/960) and highly variable among centers (range, 12% to 83%). Isolates were mainly identified as nontypeable H. influenzae (NTHi, 99%). Epidemiologically, 127 different genotypes were identified by PFGE with a minimum of two genotypes per center. One hundred fourteen children (12%) were included in both studies and none of them harbored the same strain over a period of time. The isolates only showed resistance to cotrimoxazol and ampicillin, presenting a shift in the level of ampicillin reduced susceptibility, showing a predominance of PBP3 mutations in 2004 and a predominance of β-lactamase production in 2005. This study proved the great genetic variability of NTHi isolates that present similar genotypic patterns in both years with no long-term carriage of the same strain