Time kill-assays of antibiotic combinations for multidrug resistant clinical isolates of OXA-48 carbapenemase producing Klebsiella pneumoniae.

Treatment of infections caused by OXA-48 carbapenemase producing multidrug-resistant isolates often necessitates combination therapy. In vitro effect of different antibiotic combinations against multidrug-resistant (MDR) Klebsiella pneumoniae isolates were evaluated in this study.Meropenem-tobramycin (MER+TOB), meropenem-ciprofloxacin (MER+CIP), colistin-meropenem (COL+MER), colistin-ciprofloxacin (COL+CIP) and colistin-tobramycin (COL+TOB) combinations were tested by time kill-assays. Each antibiotic alone and in combination at their Cmax values were tested against 4 clinical K. pneumoniae isolates at 1, 2, 4, 6, 8, 12 and 24 h. Effect of colistin and its associations were also assessed at 30 min. Bactericidal activity was defined as ≥3log10 CFU mL-1 decrease compared with initial inoculum. Synergy was defined as ≥2log10CFU mL-1 decrease by the combination compared with the most active single agent. Presence of blaOXA-48, blaNDM, blaVIM, blaIMP, blaKPC and blaCTX-M-1 genes was screened by PCR using specific primers.The blaOXA-48 gene was identified together with blaCTXM-1 group gene in all isolates. COL+MER demonstrated to be synergistic and bactericidal. MER+TOB showed synergistic and bactericidal effect on two strains although, regrowth was seen on other two strains at 24 h. MER+CIP exhibited indifferent effect on the strains.Combination therapy could be a potential alternative to treat MDR K. pneumoniae infections. This combination might prevent resistance development and secondary effects of colistin monotherapy. MER+TOB and MER+CIP might have an isolate-dependent effect, that may not always result in synergism.

Murepavadin antimicrobial activity against and resistance development in cystic fibrosis Pseudomonas aeruginosa isolates.

BACKGROUND: Murepavadin, a novel peptidomimetic antibiotic, is being developed as an inhalation therapy for treatment of Pseudomonas aeruginosa respiratory infection in people with cystic fibrosis (CF). It blocks the activity of the LptD protein in P. aeruginosa causing outer membrane alterations. OBJECTIVES: To determine the in vitro activity of murepavadin against CF P. aeruginosa isolates and to investigate potential mechanisms of resistance. METHODS: MIC values were determined by both broth microdilution and agar dilution and results compared. The effect of artificial sputum and lung surfactant on in vitro activity was also measured. Spontaneous mutation frequency was estimated. Bactericidal activity was investigated using time-kill assays. Resistant mutants were studied by WGS. RESULTS: The murepavadin MIC50 was 0.125 versus 4 mg/L and the MIC90 was 2 versus 32 mg/L by broth microdilution and agar dilution, respectively. Essential agreement was >90% when determining in vitro activity with artificial sputum or lung surfactant. It was bactericidal at a concentration of 32 mg/L against 95.4% of the strains within 1-5 h. Murepavadin MICs were 2-9 two-fold dilutions higher for the mutant derivatives (0.5 to >16 mg/L) than for the parental strains. Second-step mutants were obtained for the PAO mutS reference strain with an 8×MIC increase. WGS showed mutations in genes involved in LPS biosynthesis (lpxL1, lpxL2, bamA2, lptD, lpxT and msbA). CONCLUSIONS: Murepavadin characteristics, such as its specific activity against P. aeruginosa, its unique mechanism of action and its strong antimicrobial activity, encourage the further clinical evaluation of this drug.

Anti-biofilm activity of murepavadin against cystic fibrosis Pseudomonas aeruginosa isolates.

OBJECTIVES: To determine the activity of murepavadin in comparison with tobramycin, colistin and aztreonam, against cystic fibrosis (CF) Pseudomonas aeruginosa isolates growing in biofilms. The biofilm-epidemiological cut-off (ECOFF) values that include intrinsic resistance mechanisms present in biofilms were estimated. METHODS: Fifty-three CF P. aeruginosa isolates from respiratory samples were tested using the Calgary (closed system) device, while 4 [2 clinical (one smooth, one mucoid) and 2 reference strains] were tested using the BioFlux, a microfluidic open model of biofilm testing. Biofilm was stained with SYTO9® and propidium iodide. The minimal biofilm inhibitory concentration (MBIC) and the minimal biofilm eradication concentration (MBEC) were determined. The MBIC-ECOFF and the MBEC-ECOFF were calculated. RESULTS: Colistin, tobramycin and murepavadin presented similar MBIC50/MBIC90 values (4/32, 8/64 and 2/32, respectively). Murepavadin exhibited the lowest MBEC90 (64 mg/L). Aztreonam MBIC and MBEC values were higher than those of the other antibiotics tested. Tobramycin and murepavadin had the lowest MBEC-ECOFF (64 and 128 mg/L, respectively), while those of aztreonam and colistin exceeded 512 mg/L. Using the BioFlux, for the PAO1, PAO mutS and the smooth clinical strain, a significant difference (P < 0.0125) was observed when comparing the fluorescence of treated and untreated biofilms. For the mucoid strain, only the biofilm treated with aztreonam (MBIC and MBEC) and tobramycin (MBEC) showed differences with respect to the untreated biofilm. CONCLUSIONS: Murepavadin demonstrated good activity against P. aeruginosa biofilms both in open and closed systems. The MBIC-ECOFF and the MBEC-ECOFF are proposed as new parameters to estimate the activity of antibiotics on biofilms.

Susceptibility of Pseudomonas aeruginosa Recovered from Cystic Fibrosis Patients to Murepavadin and 13 Comparator Antibiotics.

The objective was to determine the in vitro antimicrobial susceptibility of Pseudomonas aeruginosa isolates cultured from cystic fibrosis (CF) patients and explore associations between strain sequence type and susceptibility. Fourteen antibiotics and antibiotic combinations, including the novel antibacterial peptide murepavadin, were tested for activity against 414 Pseudomonas aeruginosa isolates cultured from respiratory samples of CF patients. The complete genomes of the isolates were sequenced, and minimum spanning trees were constructed based on the sequence types (STs). Percentages of resistance according to CLSI 2019 breakpoints were as follows: cefepime, 14%; ceftazidime, 11%; ceftazidime-avibactam, 7%; ceftolozane-tazobactam, 3%; piperacillin-tazobactam, 12%; meropenem, 18%; imipenem, 32%; aztreonam, 23%; ciprofloxacin, 30%; gentamicin, 30%; tobramycin, 12%; amikacin, 18%; and colistin, 4%. Murepavadin MIC50 and MIC90 were 0.12 mg/liter and 2 mg/liter, respectively. There were no apparent clonal clusters associated with resistance, but higher MICs did appear to occur more often in STs with multiple isolates than in single ST isolates. In general, the CF isolates showed a wide genetic distribution. P. aeruginosa CF isolates exhibited the lowest resistance rates against ceftolozane-tazobactam, ceftazidime-avibactam, and colistin. Murepavadin demonstrated the highest activity on a per-weight basis and may therefore become a valuable addition to the currently available antibiotics for treatment of respiratory infection in people with CF.

Use of Calgary and Microfluidic BioFlux Systems To Test the Activity of Fosfomycin and Tobramycin Alone and in Combination against Cystic Fibrosis Pseudomonas aeruginosa Biofilms.

Pseudomonas aeruginosa is a major cause of morbidity and mortality in chronically infected cystic fibrosis patients. Novel in vitro biofilm models which reliably predict the therapeutic success of antimicrobial therapies against biofilm bacteria should be implemented. The activity of fosfomycin, tobramycin, and the fosfomycin-tobramycin combination against 6 susceptible P. aeruginosa strains isolated from respiratory samples from cystic fibrosis patients was tested by using two in vitro biofilm models: a closed system (Calgary device) and an open model based on microfluidics (BioFlux). All but one of the isolates formed biofilms. The fosfomycin and tobramycin minimal biofilm inhibitory concentrations (MBIC) were 1,024 to >1,024 µg/ml and 8 to 32 µg/ml, respectively. According to fractional inhibitory concentration analysis, the combination behaved synergistically against all the isolates except the P. aeruginosa ATCC 27853 strain. The dynamic formation of the biofilm was also studied with the BioFlux system, and the MIC and MBIC of each antibiotic were tested. For the combination, the lowest tobramycin concentration that was synergistic with fosfomycin was used. The captured images were analyzed by measuring the intensity of the colored pixels, which was proportional to the biofilm biomass. A statistically significant difference was found when the intensity of the inoculum was compared with the intensity of the microchannel in which the MBIC of tobramycin, fosfomycin, or their combination was used (P < 0.01) but not when the MIC was applied (P > 0.01). Fosfomycin-tobramycin was demonstrated to be synergistic against cystic fibrosis P. aeruginosa strains in the biofilm models when both the Calgary and the microfluidic BioFlux systems were tested. These results support the clinical use of this combination.

[Dalbavancin breakpoints and recommendations for in vitro study of its activity]. / Puntos de corte de dalbavancina y recomendaciones para el estudio de su actividad in vitro.

Dalbavancin is a semisynthetic lipoglycopeptide approved for the treatment of acute skin and soft tissue infections due to Gram-positive microorganisms susceptible to this antimicrobial agent. The FDA (Food and Drug Administration) and the EUCAST (European Committee on Antimicrobial Susceptibility Testing) have established clinical breakpoints to interpret the results of the antibiogram (expressed as MIC [minimum inhibitory concentration]) with approved doses (1g intravenously [IV] followed by 0.5g IV at day 8 or 1.5g IV in a single dose). The EUCAST has also determined PK/PD (pharmacokinetic/pharmacodynamic) breakpoints -susceptible, ≤ 0.25mg/L; resistant, > 0.25mg/L-, established recommendations for in vitro susceptibility testing (addition of polysorbate-80 to the growth media) and subrogate values based on the vancomycin-susceptible category to interpret dalbavancin susceptibility in the absence of in vitro study of this antimicrobial.

Is a New Standard Needed for Diffusion Methods for In Vitro Susceptibility Testing of Fosfomycin against Pseudomonas aeruginosa?

We analyzed fosfomycin susceptibility results in Pseudomonas aeruginosa clinical isolates obtained by MIC gradient strips and disk diffusion methods using two different inocula, 10(8) and 10(6) CFU/ml, and compared them to the agar dilution reference method. Essential and categorical agreements were 93.6% and 95%, respectively, for the 10(6) CFU/ml alternative inoculum, and they were 67.6% and 78.2%, respectively, for the standard inoculum (10(8) CFU/ml). The use of the 10(6) CFU/ml inoculum improves the agreement values and inhibition zone readings.

Antimicrobial Activity of Fosfomycin-Tobramycin Combination against Pseudomonas aeruginosa Isolates Assessed by Time-Kill Assays and Mutant Prevention Concentrations.

The antibacterial activity of fosfomycin-tobramycin combination was studied by time-kill assay in eight Pseudomonas aeruginosa clinical isolates belonging to the fosfomycin wild-type population (MIC = 64 µg/ml) but with different tobramycin susceptibilities (MIC range, 1 to 64 µg/ml). The mutant prevention concentration (MPC) and mutant selection window (MSW) were determined in five of these strains (tobramycin MIC range, 1 to 64 µg/ml) in aerobic and anaerobic conditions simulating environments that are present in biofilm-mediated infections. Fosfomycin-tobramycin was synergistic and bactericidal for the isolates with mutations in the mexZ repressor gene, with a tobramycin MIC of 4 µg/ml. This effect was not observed in strains displaying tobramycin MICs of 1 to 2 µg/ml due to the strong bactericidal effect of tobramycin alone. Fosfomycin presented higher MPC values (range, 2,048 to >2,048 µg/ml) in aerobic and anaerobic conditions than did tobramycin (range, 16 to 256 µg/ml). Interestingly, the association rendered narrow or even null MSWs in the two conditions. However, for isolates with high-level tobramycin resistance that harbored aminoglycoside nucleotidyltransferases, time-kill assays showed no synergy, with wide MSWs in the two environments. glpT gene mutations responsible for fosfomycin resistance in P. aeruginosa were determined in fosfomycin-susceptible wild-type strains and mutant derivatives recovered from MPC studies. All mutant derivatives had changes in the GlpT amino acid sequence, which resulted in a truncated permease responsible for fosfomycin resistance. These results suggest that fosfomycin-tobramycin can be an alternative for infections due to P. aeruginosa since it has demonstrated synergistic and bactericidal activity in susceptible isolates and those with low-level tobramycin resistance. It also prevents the emergence of resistant mutants in either aerobic or anaerobic environments.

Performance of EUCAST and CLSI approaches for co-amoxiclav susceptibility testing conditions for clinical categorization of a collection of Escherichia coli isolates with characterized resistance phenotypes.

OBJECTIVES: There are different methodological recommendations for in vitro testing of the co-amoxiclav combination. Performance of co-amoxiclav MIC testing for Escherichia coli by the standard ISO microdilution method (ISO 20776-1) was compared using EUCAST (fixed 2 mg/L clavulanate concentration) and CLSI (2 : 1 ratio) interpretive criteria. METHODS: MICs were determined by broth microdilution using a 2 : 1 ratio and fixed clavulanate concentrations (2 and 4 mg/L) for 160 clinical E. coli isolates with characterized resistance mechanisms. Essential agreements, categorical agreements and relative errors were determined. RESULTS: For all isolates, essential agreement between microdilution using 2 mg/L clavulanate and a 2 : 1 ratio was 25.6%. For ESBL-producing isolates, considering EUCAST breakpoints, 55% of isolates tested with 2 mg/L clavulanate were classified as resistant; conversely, 95% of isolates tested with 4 mg/L clavulanate were susceptible. When using CLSI breakpoints and a 2 : 1 ratio, 90% of isolates were susceptible and 10% were intermediate. CONCLUSIONS: Variation in the clavulanate concentration gave different susceptibility testing results, particularly among ESBL-producing E. coli isolates. The in vitro concentration of clavulanate that better correlates with clinical outcome is still under debate and should be established.

Patients infected with HIV are at high-risk for hepatitis E virus infection in Spain.

Hepatitis E virus is responsible for sporadic cases of acute, self-limited viral hepatitis not only in endemic but also in industrialized countries. In addition, some reports confirm that it can cause chronic infection and even cirrhosis in immunosuppressed and also in patients infected with HIV. There are few data about prevalence and incidence of HEV chronic infection in HIV-HEV coinfected individuals in Spain. The aim of this study is to investigate the prevalence of anti-HEV IgG in a representative sample of 448 patients infected with HIV and determine the role of age, gender, and CD4 counts in the detection of anti-HEV IgG antibodies in blood. In addition, the clinical features and ALT levels in relation to the presence of anti-HEV IgM and/or HEV-RNA in the blood of these patients were investigated. Anti-HEV IgG antibodies were detected in serum using a commercial enzyme immunoassay. All positive samples were studied further for the presence of anti-HEV IgM antibodies. In addition, HEV RNA was amplified by reverse transcriptase (RT)-nested PCR in all serum samples with IgM anti-HEV. The overall prevalence of anti-HEV IgG was 10.4% (45/448, 95% C.I. 7.2-12.8%). HEV-RNA was found in only one patient out of the 45 anti-HEV IgG positive samples studied. Regarding to gender and CD4 count, no difference in seroprevalence could be observed. This prevalence data suggest that patients infected with HIV can be considered a risk group for HEV infection and that chronic coinfection HEV-HIV seems to be a very rare event.

In vitro activity of fosfomycin against a collection of clinical Pseudomonas aeruginosa isolates from 16 Spanish hospitals: establishing the validity of standard broth microdilution as susceptibility testing method.

The broth microdilution method for fosfomycin and Pseudomonas aeruginosa was assessed and compared with the approved agar dilution method in 206 genetically unrelated P. aeruginosa clinical isolates. Essential agreement between the two methods was 84%, and categorical agreement was 89.3%. Additionally, Etest and disk diffusion assays were performed. Results validate broth microdilution as a reliable susceptibility testing method for fosfomycin against P. aeruginosa. Conversely, unacceptable concordance was established between Etest and disk diffusion results with agar dilution results.

[Acute, chronic and fulminant hepatitisE: seven years of experience (2004-2011)]. / Hepatitis agudas, crónicas y fulminantes por virus de la hepatitisE: 7años de experiencia (2004-2011).

OBJECTIVE: To study the clinical and epidemiological profiles of in 43cases of acute hepatitis, 5cases of fulminant hepatitis, and one of chronic hepatitis due to hepatitis E virus (HEV), detected over a 7-year period. PATIENTS: Forty-nine individuals (33male and 10female) treated between 2004 and 2011 in the Hospital Ramón y Cajal (Comunidad de Madrid, Spain). The diagnosis was made by the detection of IgG and IgM anti-HEV and RNA HEV in serum samples. Acute hepatitisE was defined by the presence of IgM anti-HEV and/or RNA HEV in serum, and chronic hepatitisE if the ARN was detectable more than 6months. Fulminant hepatitisE was diagnosed if encephalopathy was observed in addition to IgM anti-HEV and/or RNA HEV in serum. RESULTS: The median age was 46.67 and 49.6years in acute hepatitisE and fulminant hepatitisE, respectively. The risk factors recorded were travel to endemic areas in 13patients, 4were in contact with animals, 4suffered from hepatic steatosis due to alcohol consumption, 3consumed uncontrolled foods, and 2drank water from streams. DISCUSSION: HEV is the cause of acute self-limited hepatitis, although 36.73% of the studied cases had to be hospitalised. However a small number of patients, 10.2%, had fulminant hepatitis requiring liver transplant. Chronic hepatitisE is very infrequent in immunocompetent individuals. The increase in incidence of hepatitisE is due to the introduction of better diagnostic tests in recent years.

Establishing Antimicrobial Susceptibility Testing Methods and Clinical Breakpoints for Inhaled Antibiotic Therapy.

Inhaled antibiotics are a common and valuable therapy for patients suffering from chronic lung infection, with this particularly well demonstrated for patients with cystic fibrosis. However, in vitro tests to predict patient response to inhaled antibiotic therapy are currently lacking. There are indications that antimicrobial susceptibility testing (AST) may have a role in guidance of therapy, but which tests would correlate best still needs to be researched in clinical studies or animal models. Applying the principles of European Committee on Antimicrobial Susceptibility Testing methodology, the analysis of relevant and reliable data correlating different AST tests to patients' outcomes may yield clinical breakpoints for susceptibility, but these data are currently unavailable. At present, we believe that it is unlikely that standard determination of minimum inhibitory concentration will prove the best predictor.

Whole-genome analysis of Haemophilus influenzae strains isolated from persons with cystic fibrosis.

Introduction. Haemophilus influenzae is a commensal of the respiratory tract that is frequently present in cystic fibrosis (CF) patients and may cause infection. Antibiotic resistance is well described for CF strains, and virulence factors have been proposed.Hypothesis/Gap. The genetic diversity of H. influenzae strains present in the lungs of persons with CF is largely unknown despite the fact that this organism is considered to be a pathogen in this condition. The aim was to establish the genetic diversity and susceptibility of H. influenzae strains from persons with CF, and to screen the whole genomes of these strains for the presence of antibiotic resistance determinants and proposed virulence factors.Methods. A total of 67 strains, recovered from respiratory samples from persons with CF from the UK (n=1), Poland (n=2), Spain (n=24) and the Netherlands (n=40), were subjected to whole-genome sequencing using Illumina technology and tested for antibiotic susceptibility. Forty-nine of these strains (one per different sequence type) were analysed for encoded virulence factors and resistance determinants.Results. The 67 strains represented 49 different sequence types. Susceptibility testing showed that all strains were susceptible to aztreonam, ciprofloxacin, imipenem and tetracycline. Susceptibility to ampicillin, ampicillin/sulbactam, amoxicillin/clavulanic acid, cefuroxime, cefixime, ceftriaxone, cefepime, meropenem, clarithromycin, co-trimoxazole and levofloxacin ranged from 70.2-98.5%. Only 6/49 strains (12.2%) harboured acquired resistance genes. Mutations associated with a ß-lactamase-negative ampicillin-resistant phenotype were present in four strains (8.2 %). The potential virulence factors, urease, haemoglobin- and haptoglobin-binding protein/carbamate kinase, and OmpP5 (OmpA), were encoded in more than half of the strains. The genes for HMW1, HMW2, H. influenzae adhesin, a IgA-specific serine endopeptidase autotransporter precursor, a TonB-dependent siderophore, an ABC-transporter ATP-binding protein, a methyltransferase, a BolA-family transcriptional regulator, glycosyltransferase Lic2B, a helix-turn-helix protein, an aspartate semialdehyde dehydrogenase and another glycosyltransferase were present in less than half of the strains.Conclusion. The H. influenzae strains showed limited levels of resistance, with the highest being against co-trimoxazole. Sequences encoding a carbamate kinase and a haemoglobin- and haemoglobin-haptoglobin-binding-like protein, a glycosyl transferase and an urease may aid the colonization of the CF lung. The adhesins and other identified putative virulence factors did not seem to be necessary for colonization.

Evaluation of Rapid Polymyxin Pseudomonas test in clinical Pseudomonas aeruginosa isolates with various degrees of multidrug resistance.

BACKGROUND: Pseudomonas aeruginosa is of great concern among MDR bacteria and rapid and reliable in vitro antibiotic susceptibility testing methods are extremely necessary. Colistin is, in many cases, among the limited useful alternatives for these isolates. Unfortunately, only a few reliable in vitro methods are validated for testing susceptibility to colistin. Although EUCAST and CLSI recommend broth microdilution (BMD) as the standard method for antibiotic susceptibility testing, this method is not routinely performed in microbiology laboratories. However, some commercial products based upon BMD have tested well and offer consistent results. OBJECTIVES: To evaluate the performance of the colorimetric Rapid Polymyxin Pseudomonas Test (RPPT) (ELITech Microbiology, France). METHODS: Eighty-seven clinical P. aeruginosa strains, prospectively collected in two microbiology laboratories exhibiting either susceptibility or various degrees of multidrug resistance, including to colistin, were used. Different susceptibility testing methods were simultaneously performed and compared with reference BMD and interpreted using 2020 EUCAST criteria. RESULTS: Results indicate an essential agreement (EA) of 97.7% for RPPT while the other tests did not reach 90% of EA [66.7% MicroScan, 63.2% Etest (bioMérieux, France) and 60.9% other MIC Test Strips (MTS, Liofilchem, Italy)]. The categorical agreement was 98.9% for RPPT, 87.4% for MTS, 85.1% for Etest and 64.4% for MicroScan. CONCLUSIONS: The RPPT was able to accurately detect both colistin-susceptible and -resistant isolates within 4 h, offering a rapid alternative for a prompt decision about the inclusion of this antibiotic in a patient's treatment.

Draft genome sequence of the strain 16-537536, isolated from a patient with bronchiectasis and its relationship to the Pseudomonas koreensis group of the Pseudomonas fluorescens complex.

OBJECTIVE: The Pseudomonas koreensis group bacteria are usually found in soil and are associated with plants. Currently they are poorly described. Here we report on the whole genome sequence of a bacterial isolate from a patient with bronchiectasis that was first identified as P. koreensis, and on its position in the P. koreensis group. RESULTS: Strain 16-537536 was isolated from a patient with bronchiectasis from Spain and initially identified by MALDI-TOF as P. koreensis, a member of the Pseudomonas fluorescens complex. However, the average nucleotide identity analysis (ANIb) and whole genome alignments of the draft genome sequence of this strain showed it to be a member of the P. koreensis group of the P. fluorescens complex, but belonging to an undescribed species. In addition, based on ANIb analysis, the P. koreensis group contains several other unnamed species. Several genes for putative virulence factors were identified. The only antibiotic resistance gene present in strain 16-537536 was a class C ß-lactamase. The correct identification of bacterial species from patients is of utmost importance in order to understand their pathogenesis and to track the potential spread of pathogens between patients. Whole genome sequence data should be included for the description of new species.

Whole-genome analysis of Pandoraea species strains from cystic fibrosis patients.

Aim: Genetic characterization of Pandoraea strains recovered from cystic fibrosis patients. Materials & methods: The whole-genome sequence of 12 Pandoraea strains was determined using Illumina technology. The position of the strains within the genus Pandoraea was analyzed using selected partial gene sequences, core genome multi-locus sequence typing and average nucleotide identity analysis. Furthermore, the sequences were annotated. Results: The results show that some strains previously identified as Pandoraea pnomenusa, Pandoraea sputorum, Pandoraea oxalativorans and Pandoraea pulmonicola belong to novel species. The strains did not harbor acquired antibiotic resistance genes but encoded an OXA-type ß-lactamase. Conclusion: The taxonomy of the genus Pandoraea needs to be revised.

Antimicrobial susceptibility of non-fermenting Gram-negative pathogens isolated from cystic fibrosis patients.

Non-fermenting Gram-negative bacteria (NFGNB) are increasingly cultured in respiratory samples from cystic fibrosis (CF) patients. This study determined the antimicrobial susceptibility of clinical CF respiratory isolates from distinct geographical regions. A total of 286 isolates (106 Stenotrophomonas maltophilia, 100 Burkholderia spp., 59 Achromobacter spp., 12 Pandoraea spp., 9 Ralstonia spp.) from the Netherlands, Northern Ireland, Spain, USA and Australia were tested. MIC50/90 values and susceptibility categorisation were determined. Trimethoprim/sulfamethoxazole (SXT) was the most active compound for all micro-organisms (MIC50, 0.12-4 mg/L; MIC90, 1-16 mg/L). For S. maltophilia, 47% and 62% of isolates were susceptible to SXT according to CLSI and EUCAST breakpoints, respectively. Ceftazidime presented lower susceptibility (35%; MIC50, 32 mg/L; MIC90, 256 mg/L). MIC90 values for tobramycin and colistin were >128 mg/L and >16 mg/L, respectively. Regarding Burkholderia, 72%, 56% and 44% were susceptible to SXT, ceftazidime and meropenem, respectively. For both ceftazidime and meropenem, MIC50 and MIC90 values were within the intermediate or resistant category. The most active antibiotics for Achromobacter spp. were SXT (MIC50, 0.5 mg/L; MIC90, 8 mg/L) and imipenem (MIC50, 2 mg/L; MIC90, 8 mg/L). SXT, imipenem and ciprofloxacin were active against 12 Pandoraea spp. (MIC50, 0.12-4 mg/L; MIC90, 1-8 mg/L). Ciprofloxacin (MIC50, 4 mg/L) and SXT (MIC50, 1 mg/L) were the only active antibiotics for Ralstonia spp. There were no statistically significant differences in susceptibility rates between countries. NFGNB other than Pseudomonas aeruginosa are potential pathogens in CF. SXT was demonstrated to be the most active compound against these isolates.

Hypermucoviscous Klebsiella pneumoniae: A challenge in community acquired infection.

In 1986, a new syndrome was described in Taiwan secondary to hypervirulent K. pneumoniae (hvKP), and its main feature was the ability to cause severe infection in young and immunocompetent hosts. Their virulence is explained by the efficient acquisition of iron and an increase in capsule production, which confer the characteristic hypermucoviscous phenotype. Most of these cases have been described in Asia and subsequently spread to America and Europe, where their prevalence is much lower. We present four cases of bacteremia and liver abscesses secondary to hypervirulent K. pneumoniae, two of them associated with endophthalmitis. K. pneumoniae isolates recovered from two of the patients belonged to capsular serotype K1 (genes wzx_K1 and magA), while the other two were K2 (gene wzy_K2). Both of the K1 isolates were classified into a ST23, and isolates of serotype K2 belonged to the ST375 and ST881 clones. In Europe, hvKP isolates are less frequently recovered, mostly associated with Asian citizens or travelers, which was not the case in our patients. K1 capsular serotype is a major cause of primary liver abscess and secondary septic embolus, and K2 is associated with secondary liver abscess. Although these hypervirulent variants usually affect immunocompetent patients as in our cases, diabetes mellitus is a major risk factor for the most invasive cases, with concomitant poor prognosis. Identification of hypervirulent K. pneumoniae serotypes K1 and K2 should be considered as part of the microbiological diagnosis of community-acquired liver abscess due to their clinical implications.

Microbiological diagnosis of biofilm-related infections. / Diagnóstico microbiológico de las infecciones relacionadas con la formación de biopelículas.

Biofilm-related infections represent a serious health problem, accounting for 65- 80% of all infections. The infections are generally chronic and characterized by the persistence of the microorganism, due to the increased resistance of biofilms to both the immune system and antimicrobials. Biofilms can be located to almost every human body tissue and on exogenous devices such as catheters, pacemakers, prosthetic material, implants, urinary catheters, etc. Traditional antimicrobial susceptibility studies in clinical microbiology laboratories have lied on the study of planktonic form of microorganisms. However, this approach might lead to miss the biofilm characteristics and to a treatment failure. Microbiological diagnosis and antimicrobial susceptibility studies of biofilm-related infections are complex and, nowadays, represent a challenge that clinicians and microbiologists have to address as a team in the absence of consensus or standardized protocols.