Diagnostic tool for surveillance, detection and monitoring of the high-risk clone K. pneumoniae ST15.

BACKGROUND: The global spread of Klebsiella pneumoniae ST15, causing multi-continental outbreaks, contributes to the movement of resistance genes between clones increasing the antimicrobial resistance crisis. The genomic traits providing it with the ability to outcompete other bacteria and cause epidemics remain unclear. AIM: To identify the specific genomic traits of K. pneumoniae ST15 to develop a diagnostic test. METHODS: An outbreak caused by K. pneumoniae occurred in Hospital A Coruña, Spain. Antimicrobial susceptibility analysis and molecular typing (PGFE and MLST) were performed. One isolate of each sequence type was selected for whole-genome sequencing analysis. Comparative analysis of genomes was performed using RAST. BLASTn was used to evaluate the presence of the fhaC and kpiD genes. Two hundred and ninety-four K. pneumoniae from a Spanish nationwide collection were analysed by PCR. FINDINGS: Genotyping showed that 87.5% of the isolates tested belonged to a clone with a unique PFGE pattern which corresponded to ST15. Comparative genomic analysis of the different STs enabled us to determine the specific genomic traits of K. pneumoniae ST15. Two adherence-related systems (Kpi and KpFhaB/FhaC) were specific markers of this clone. Multiplex-PCR analysis with kpiD and fhaC oligonucleotides revealed that K. pneumoniae ST15 is specifically detected with a sensitivity of 100% and a specificity of 97.76%. The PCR results showed 100% concordance with the MLST and whole-genome sequencing data. CONCLUSION: K. pneumoniae ST15 possesses specific genomic traits that could favour its dissemination. They could be used as targets to detect K. pneumoniae ST15 with high sensitivity and specificity.

The role of the microbiology laboratory in the diagnosis of multidrug-resistant Gram-negative bacilli infections. The importance of the determination of resistance mechanisms.

Early diagnosis and treatment has an important impact on the morbidity and mortality of infections caused by multidrug-resistant bacteria. Multidrug-resistant gram-negative bacilli (MR-GNB) constitute the main current threat in hospitals and especially in intensive care units (ICU). The role of the microbiology laboratory is essential in providing a rapid and effective response. This review updates the microbiology laboratory procedures for the rapid detection of BGN-MR and its resistance determinants. The role of the laboratory in the surveillance and control of outbreaks caused by these bacteria, including typing techniques, is also studied. The importance of providing standardized resistance maps that allow knowing the epidemiological situation of the different units is emphasized. Finally, the importance of effective communication systems for the transmission of results and decision making in the management of patients infected by BGN-MR is reviewed.

Development of an Anti-Acinetobacter baumannii Biofilm Phage Cocktail: Genomic Adaptation to the Host.

The need for alternatives to antibiotic therapy due to the emergence of multidrug resistant bacteria (MDR), such as the nosocomial pathogen Acinetobacter baumannii, has led to the recovery of phage therapy. In addition, phages can be combined in cocktails to increase the host range. In this study, the evolutionary mechanism of adaptation was utilized in order to develop a phage adapted to A. baumannii, named phage Ab105-2phiΔCI404ad, from a mutant lytic phage, Ab105-2phiΔCI, previously developed by our group. The whole genome sequence of phage Ab105-2phiΔCI404ad was determined, showing that four genomic rearrangements events occurred in the tail morphogenesis module affecting the ORFs encoding the host receptor binding sites. As a consequence of the genomic rearrangements, 10 ORFs were lost and four new ORFs were obtained, all encoding tail proteins; two inverted regions were also derived from these events. The adaptation process increased the host range of the adapted phage by almost 3-fold. In addition, a depolymerase-expressing phenotype, indicated by formation of a halo, which was not observed in the ancestral phage, was obtained in 81% of the infected strains. A phage cocktail was formed by combining this phage with the A. baumannii phage vB_AbaP_B3, known to express a depolymerase. Both the individual phages and the phage cocktail showed strong antimicrobial activity against 5 clinical strains and 1 reference strain of A. baumannii tested. However, in all cases resistance to the bacterial strains was also observed. The antibiofilm activity of the individual phages and the cocktail was assayed. The phage cocktail displayed strong antibiofilm activity.

Comparative activity of a polyhexanide-betaine solution against biofilms produced by multidrug-resistant bacteria belonging to high-risk clones.

The aim of this study was to investigate the effect of polyhexanide (polyhexamethylene biguanide)-betaine (PHMB-B) compared with 2% chlorhexidine against biofilms of high-risk and/or multidrug-resistant bacterial clones. The minimum inhibitory concentrations of both biocides were determined by microdilution. The effect of PHMB-B and chlorhexidine on biofilm was evaluated by spectrophotometry and cell viability assays. At commercial concentrations, PHMB-B reduced 24 h, 48 h and 1-week biofilms of all pathogens tested. PHMB-B was more active than 2% chlorhexidine against Gram-negative bacterial 24 h and 48 h biofilms and Gram-positive bacterial 7-day biofilms. In summary, the activity of PHMB-B was superior to that of 2% chlorhexidine in those biofilms.

Application of BioFire FilmArray Blood Culture Identification panel for rapid identification of the causative agents of ventilator-associated pneumonia.

OBJECTIVE: To evaluate the ability of the BioFire FilmArray Blood Culture Identification (BCID) panel to rapidly detect pathogens producing late-onset ventilator-associated pneumonia (VAP), a severe infection often produced by Gram-negative bacteria. These microorganisms are frequently multidrug resistant and typically require broad-spectrum empiric treatment. METHODS: In the context of an international multicentre clinical trial (MagicBullet), respiratory samples were collected at the time of suspicion of VAP from 165 patients in 32 participating hospitals in Spain, Greece and Italy. Microorganisms were identified using the BCID panel and compared with results obtained by conventional microbiologic techniques. RESULTS: Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae were the most commonly identified species, representing 54.7% (70/128) of microorganisms. The BCID panel showed high global specificity (98.1%; 95% confidence interval, 96-100) and negative predictive values (96.6%) and a global sensitivity and positive predictive value of 78.6% (95% confidence interval, 70-88) and 87.3%, respectively, for these microorganisms. Importantly, the BCID panel provided results in only 1 hour directly from respiratory samples with minimal sample processing times. CONCLUSIONS: The BCID panel may have clinical utility in rapidly ruling out microorganisms causing VAP, specifically multidrug-resistant Gram-negative species. This could facilitate the optimization of empiric treatment.

Resistant Cytomegalovirus Infection After Renal Transplantation: Literature Review.

BACKGROUND: Resistant cytomegalovirus (R-CMV) is an emerging problem in the renal transplantation population. The most frequent CMVs are high-resistance mutations (UL97 gene). METHODS: We describe our experience in management of R-CMV after renal transplant at our center (2012-2016). RESULTS: We encountered 3 cases of R-CMV infection after renal transplant (all primary infections). All 3 patients received induction therapy with corticosteroids, tacrolimus, and mycophenolate mofetil. The first patient (basiliximab induction, preemptive CMV) developed CMV replication on day +53, which responded poorly both to standard-dose valganciclovir (vGCV) and high-dose ganciclovir (GCV) (creatinine clearance [CrCl] >70 mL/min; vGCV 900 mg twice daily for 50 days and GCV 7.5 mg/kg twice daily for 8 days). Hematologic toxicity occurred. The R-CMV test was positive and foscarnet (FOS) was initiated (90 mg/kg twice daily for 21 days). The second patient presented CMV infection (day +30, thymoglobulin induction, CMV prophylaxis), which was not controlled with the high dose (CrCl 23 mL/min; GCV 3.5 mg/kg twice daily and vGCV 900 mg twice daily), resulting in severe neutropenia. R-CMV was detected and FOS initiated (FOS 50 mg/kg twice daily for 7 days and 50 mg/kg every 2 days for 13 days). The third patient's infection occurred on day +22 (basiliximab induction, preemptive CMV). Standard-dose vGCV was uneffective (CrCl >70 mL/min, vGCV 900 mg twice daily) and it did not respond to the high dose (GCV 7.5 mg/kg twice daily and vGCV 2700 mg/d). Moderate hematologic toxicity occurred. R-CMV was diagnosed and FOS treatment begun (FOS 70 mg/kg per day for 2 weeks). CONCLUSIONS: Resistant CMV infection may be severe due to viral infection and side effects of high-dose antiviral treatment. We presented 3 cases requiring the use of FOS in the absence of response or toxic effects from the usual treatment, with an optimal sustained response (temporary in case 2) and without serious side effects.

Evolution of the Quorum network and the mobilome (plasmids and bacteriophages) in clinical strains of Acinetobacter baumannii during a decade.

In this study, we compared eighteen clinical strains of A. baumannii belonging to the ST-2 clone and isolated from patients in the same intensive care unit (ICU) in 2000 (9 strains referred to collectively as Ab_GEIH-2000) and 2010 (9 strains referred to collectively as Ab_GEIH-2010), during the GEIH-REIPI project (Umbrella BioProject PRJNA422585). We observed two main molecular differences between the Ab_GEIH-2010 and the Ab_GEIH-2000 collections, acquired over the course of the decade long sampling interval and involving the mobilome: i) a plasmid harbouring genes for blaOXA 24/40 ß-lactamase and abKA/abkB proteins of a toxin-antitoxin system; and ii) two temperate bacteriophages, Ab105-1ϕ (63 proteins) and Ab105-2ϕ (93 proteins), containing important viral defence proteins. Moreover, all Ab_GEIH-2010 strains contained a Quorum functional network of Quorum Sensing (QS) and Quorum Quenching (QQ) mechanisms, including a new QQ enzyme, AidA, which acts as a bacterial defence mechanism against the exogenous 3-oxo-C12-HSL. Interestingly, the infective capacity of the bacteriophages isolated in this study (Ab105-1ϕ and Ab105-2ϕ) was higher in the Ab_GEIH-2010 strains (carrying a functional Quorum network) than in the Ab_GEIH-2000 strains (carrying a deficient Quorum network), in which the bacteriophages showed little or no infectivity. This is the first study about the evolution of the Quorum network and the mobilome in clinical strains of Acinetobacter baumannii during a decade.

Prevalence and distribution of hepatitis C virus genotypes in Spain during the 2000-2015 period (the GEHEP 005 study).

We report the largest study on the prevalence and distribution of HCV genotypes in Spain (2000-2015), and we relate them with clinical, epidemiological and virological factors. Patients from 29 hospitals in 10 autonomous communities (Andalusia, Aragon, Castilla-Leon, Catalonia, Galicia, Canary Islands, Madrid Community, Valencian Community, Murcia Region and Basque Country) have been studied. Annual distribution of HCV genotypes and subtypes, as well as gender, age, transmission route, HIV and/or HBV coinfection, and treatment details were recorded. We included 48595 chronically HCV-infected patients with the following characteristics: median age 51 years (IQR, 44-58), 67.9% male, 19.1% HIV-coinfected, 23.5% HBV-coinfected. Parenteral transmission route was the most frequent (58.7%). Genotype distribution was 66.9% GT1 (24.9% subtype 1a and 37.9% subtype 1b), 2.8% GT2, 17.3% GT3, 11.4% GT4 and 0.1% GT5 and 0.02% GT6. LiPA was the most widely HCV genotyping test used (52.4%). HCV subtype 1a and genotypes 3 and 4 were closely associated with male gender, parenteral route of infection and HIV and HBV coinfection; in contrast, subtype 1b and genotype 2 were associated with female gender, nonparenteral route and mono-infection. Age was related to genotype distribution, and different patterns of distribution and biodiversity index were observed between different geographical areas. Finally, we describe how treatment and changes in transmission routes may have affected HCV genotype prevalence and distribution patterns. We present the most recent data on molecular epidemiology of hepatitis C virus in Spain. This study confirms that genotype distributions vary with age, sex, HIV and HBV coinfection and within geographical areas and epidemiological groups.

KIR2DS2 as predictor of thrombocytopenia secondary to pegylated interferon-alpha therapy.

Our aim was to evaluate the killer cell immunoglobulin-like receptors (KIRs) as a marker for the development of thrombocytopenia secondary to Peg-interferon (IFN) therapy in a cohort of human immunodeficiency virus (HIV)/hepatitis C virus (HCV) co-infected patients. Patients were naive to HCV treatment, receiving a first course of Peg-IFN/Ribavirin combination therapy. Total platelet count (cells ml-1) was determined at each visit, determining platelet decline from baseline to weeks 1, 2, 4, 8 and 12 after starting therapy. The end point of the study was development of thrombocytopenia, defined as a platelet count of <1 50 000 cells ml-1. Fifty-eight HIV/HCV co-infected patients were included in the study, of whom 20 (34.4%) developed thrombocytopenia. The absence of KIR2DS2 was associated with higher and faster rate of thrombocytopenia (54.2% vs 22.5%; P=0.012; 6.6 vs 10.3 weeks; P=0.008). The absence of KIR2DS2 was associated with a greater decline in platelet count and development of thrombocytopenia during Peg-IFN treatment in HIV/HCV co-infected patients.

Genomic Evolution of Two Acinetobacter baumannii Clinical Strains from ST-2 Clones Isolated in 2000 and 2010 (ST-2_clon_2000 and ST-2_clon_2010).

Acinetobacter baumannii is a successful nosocomial pathogen due to its ability to persist in hospital environments by acquiring mobile elements such as transposons, plasmids, and phages. In this study, we compared two genomes of A. baumannii clinical strains isolated in 2000 (ST-2_clon_2000) and 2010 (ST-2_clon_2010) from GenBank project PRJNA308422.

Monotherapy versus combination therapy for sepsis due to multidrug-resistant Acinetobacter baumannii: analysis of a multicentre prospective cohort.

BACKGROUND: Treatment of multidrug-resistant Acinetobacter baumannii (MDRAB) infection presents a challenge because of the scarcity of available options. Even though combination therapy (CT) is frequently used in clinical practice, data are needed to support its use instead of monotherapy (MT). METHODS: A prospective observational study was conducted in 28 Spanish hospitals. Patients with sepsis caused by MDRAB, defined according to strict criteria, and who received active antibiotic treatment (according to in vitro susceptibility testing) for at least 48 h, were included. The main outcome variable was all-cause 30 day mortality after initiation of targeted therapy. Multivariate analysis, including a propensity score (for receiving CT), was performed by Cox regression. RESULTS: One hundred and one patients were included in the analysis; 68 (67.3%) received MT and 33 (32.7%) received CT. Pneumonia was the most common infection (50.5%), 68.6% of cases being associated with mechanical ventilation. Colistin (67.6%) and carbapenems (14.7%) were the most common drugs used in MT; colistin plus tigecycline (27.3%) and carbapenem plus tigecycline (12.1%) were the most frequent combinations. Crude 30 day mortality was 23.5% and 24.2% for the MT and CT groups, respectively (RR = 1.03; 95% CI 0.49-2.16; P = 0.94). Multivariate analysis of 30 day survival showed no trend towards reduced 30 day mortality with CT (HR = 1.35; 95% CI 0.53-3.44; P = 0.53). Subgroup analysis showed similar results. CONCLUSIONS: Our data do not support an association of CT with reduced mortality in MDRAB infections. More data for specific types of infection and combinations are needed.

Contribution of efflux pumps, porins, and ß-lactamases to multidrug resistance in clinical isolates of Acinetobacter baumannii.

We investigated the mechanisms of resistance to carbapenems, aminoglycosides, glycylcyclines, tetracyclines, and quinolones in 90 multiresistant clinical strains of Acinetobacter baumannii isolated from two genetically unrelated A. baumannii clones: clone PFGE-ROC-1 (53 strains producing the OXA-58 ß-lactamase enzyme and 18 strains with the OXA-24 ß-lactamase) and clone PFGE-HUI-1 (19 strains susceptible to carbapenems). We used real-time reverse transcriptase PCR to correlate antimicrobial resistance (MICs) with expression of genes encoding chromosomal ß-lactamases (AmpC and OXA-51), porins (OmpA, CarO, Omp33, Dcap-like, OprB, Omp25, OprC, OprD, and OmpW), and proteins integral to six efflux systems (AdeABC, AdeIJK, AdeFGH, CraA, AbeM, and AmvA). Overexpression of the AdeABC system (level of expression relative to that by A. baumannii ATCC 17978, 30- to 45-fold) was significantly associated with resistance to tigecycline, minocycline, and gentamicin and other biological functions. However, hyperexpression of the AdeIJK efflux pump (level of expression relative to that by A. baumannii ATCC 17978, 8- to 10-fold) was significantly associated only with resistance to tigecycline and minocycline (to which the TetB efflux system also contributed). TetB and TetA(39) efflux pumps were detected in clinical strains and were associated with resistance to tetracyclines and doxycycline. The absence of the AdeABC system and the lack of expression of other mechanisms suggest that tigecycline-resistant strains of the PFGE-HUI-1 clone may be associated with a novel resistance-nodulation-cell efflux pump (decreased MICs in the presence of the inhibitor Phe-Arg ß-naphthylamide dihydrochloride) and the TetA(39) system.

Contribution of OqxAB efflux pumps to quinolone resistance in extended-spectrum-ß-lactamase-producing Klebsiella pneumoniae.

OBJECTIVES: The aims of this study were to analyse the presence of oqxA and oqxB genes in a collection of extended-spectrum ß-lactamase (ESBL)-producing Klebsiella pneumoniae strains, to determine their chromosomal and/or plasmidic locations and to analyse expression levels in relation to susceptibility or resistance to quinolones. METHODS: A collection of 114 non-repetitive isolates of ESBL-producing K. pneumoniae was used. K. pneumoniae ATCC 27799 and K. pneumoniae ATCC 700603 were also included. Detection of oqxA and oqxB genes was performed by PCR. Testing for chromosomal and/or plasmidic location was carried out using plasmid DNA and subsequent hybridization. oqxA gene expression was analysed using real-time RT-PCR. Transfer of the plasmid-encoded OqxAB was evaluated. RESULTS: The prevalence of both oqxA and oqxB detected in K. pneumoniae was high: 76% and 75%, respectively. Hybridization assays showed that oqxA (16%) and oqxB (13%) were simultaneously present in locations on the chromosome and on large plasmids. The plasmids were transferable by transformation into K. pneumoniae. RT-PCR assays showed higher expression (4-fold) in strains with reduced susceptibility to quinolones than in susceptible strains. Interestingly, K. pneumoniae ATCC 700603 showed an 18-fold higher expression than K. pneumoniae ATCC 27799. These differences were in accordance with quinolone susceptibility. CONCLUSIONS: The prevalence of the OqxAB efflux pump (both chromosomal and plasmid encoded) in ESBL-producing K. pneumoniae is high in Spain and represents a potential reservoir for the spread of these genes. High expression of this pump contributes to reduced susceptibility to quinolones in clinical isolates of ESBL-producing K. pneumoniae.

First report of an OXA-23 carbapenemase-producing Acinetobacter baumannii clinical isolate related to Tn2006 in Spain.

A carbapenem-resistant Acinetobacter baumannii clinical isolate belonging to European clone II and sequence type 2 was recovered from a patient in the Son Espases hospital in Mallorca, Spain. Genetic analysis showed the presence of the bla(OXA-23) gene in association with the widely disseminated transposon Tn2006. This is the first reported identification of A. baumannii carrying bla(OXA-23) in Spain.

Predictive baseline criteria of primary therapeutic failure in chronic hepatitis C genotype 1.

BACKGROUND AND AIMS: more than half of patients with genotype 1 chronic hepatitis C (CHC) do not achieve a sustained viral response (SVR) to current antiviral therapy due to primary non-response, relapse or intolerance. Factors related to each of these unfavorable outcomes are different and the last two may be partially prevented. Our aim was to identify basal criteria to predict the risk of primary failure. PATIENTS AND METHODS: we included 251 consecutive patients (152 males) from a single centre, infected with HCV genotype 1 and not previously treated. SVR was achieved in 141 patients and primary failure in 110. RESULTS: high vs. low viral load (> 400,000 IU/mL, OR = 6.17; 95% CI: 2.50-15.23), high serum GGT (> 60 IU/mL, OR = 4.25; 95% CI: 2.49-7.24), low serum cholesterol ( < 178 mg/dL, OR = 2.93; 95% CI: 1.75-4.92) and older age (> 47 yrs., OR = 1.79; 95% CI: 1.08-2.96) were associated to the risk of primary failure in the lineal logistic regression analysis. From the 58 patients carrying all the first three negative criteria, 46 (79.3%) were primary non-responders. CONCLUSIONS: the negative basal profile identified in this study is based on easily available data and provides information about the risk of primary therapeutic failure, and may help to decide whether antiviral therapy should be offered to a single patient.

Oscillations in serum ferritin associated with antiviral therapy in chronic hepatitis C.

BACKGROUND: Hyperferritinemia is often found in patients with chronic hepatitis C (CHC) and is predictive of poorer response to antiviral therapy. OBJECTIVE: To investigate changes in ferritinemia during and after antiviral therapy. PATIENTS AND METHODS: serum ferritin levels were measured in 262 CHC patients (163 males, mean age 48.5 years +/- 10.1) before and during antiviral therapy, and six months post-treatment in all 154 patients with undetectable serum HCV-RNA after therapy completion. RESULTS: Baseline serum ferritin was higher in patients with primary therapeutic failure than in those reaching sustained viral response (330 +/- 291 ng/mL vs. 211 +/- 192 ng/mL, p = 0.002). Serum ferritin transiently increased during therapy from baseline (257 +/- 242 ng/mL vs. 875 +/- 630 ng/mL, p < 0.001). Six months after finishing therapy, serum ferritin decreased under baseline values both in sustained responders (117 +/- 102 ng/mL vs. 211+/- 192 ng/mL, p < 0.001) and, to a lesser extent, in relapsers (217 +/- 174 ng/mL vs. 257 +/- 221 ng/mL, p = 0.047). CONCLUSIONS: Baseline serum ferritin may predict response to antiviral treatment in chronic hepatitis C. Combined antiviral therapy induces a marked increase in serum ferritin that falls below baseline values after sustained viral response, suggesting that the cause of hyperferritinemia in many patients is HCV infection itself rather than iron overload.

[Results of the treatment of chronic hepatitis C genotype 4--a comparative analysis with genotype 1]. / Resultados del tratamiento de la hepatitis crónica por VHC genotipo 4. Un análisis comparativo con el genotipo 1.

INTRODUCTION: nearly all the data on the efficacy of combined antiviral therapy on chronic hepatitis C genotype 4 have been obtained in countries of Middle East. Genotype 4 is quite unusual in Spain. We report our experience in a group of Spanish patients treated with homogeneous criteria. PATIENTS AND METHODS: between 2001 and 2007 we have treated 30 patients with chronic hepatitis C genotype 4 (20 males) with pegylated Interferon alpha-2b (26 cases) or alpha-2a (4 cases) combined with ribavirin at a weight-adjusted dose. Results of therapy are known in all patients and liver biopsy is available in 24 cases. RESULTS: ten patients (33.3%) obtained sustained viral response (SVR: HCV-RNA undetectable in blood 6 months after the end of therapy), 12 were primary non-responders, 4 relapsed after reaching undetectable HCV-RNA at the end of therapy and 4 interrupted the treatment due to severe adverse events. These results are very close to those obtained in 355 patients infected with HCV genotype 1. CONCLUSION: HCV genotype 4 should be considered as "difficult to treat". The better results of therapy in other geographical areas (Middle East) may be due to a different distribution of the subtypes of HCV genotype 4.

Efficacy of amoxycillin-clavulanate in an experimental model of murine pneumonia caused by AmpC-non-hyperproducing clinical isolates of Escherichia coli resistant to cefoxitin.

The algorithms included in most automated systems used for antimicrobial susceptibility testing (e.g., Vitek 2) consider that Escherichia coli isolates resistant to cefoxitin are AmpC-hyperproducers and, consequently, resistant also to amoxycillin-clavulanate. However, a recent study revealed that 30% of E. coli clinical isolates resistant to cefoxitin remained susceptible in vitro to amoxycillin-clavulanate. The aim of the present study was to evaluate the in-vivo efficacy of amoxycillin-clavulanate in the treatment of an experimental model of pneumonia, using two clonally related isolates (with identical repetitive extragenic palindromic sequence (REP)-PCR patterns) of AmpC-non-hyperproducing and OmpF-lacking E. coli (Ec985 and Ec571) that were resistant to cefoxitin and susceptible to cefotaxime and amoxycillin-clavulanate. MICs were determined using a microdilution technique, and in-vitro bactericidal activity was tested using time-kill assays. The in-vivo efficacy of amoxycillin, amoxycillin-clavulanate and cefotaxime against both isolates was tested in a murine pneumonia model using immunocompetent C57BL/6 mice. Ec571 (a TEM-1/2 producer) was resistant to amoxycillin, whereas Ec985 (a TEM-1/2 non-producer) was susceptible. Amoxycillin, amoxycillin-clavulanate and cefotaxime were bactericidal for Ec985, and amoxycillin-clavulanate and cefotaxime were bactericidal for Ec571 at different concentrations and time-points, as determined using time-kill assays. Treatment with amoxycillin, amoxycillin-clavulanate and cefotaxime reduced the bacterial lung concentration of Ec985 compared with non-treated controls (p <0.05), whereas amoxycillin-clavulanate and cefotaxime showed efficacy against Ec571 when compared with the control and amoxycillin groups (p <0.05). Regardless of the exact underlying mechanism(s) of resistance, amoxycillin-clavulanate was effective in the experimental murine model in the treatment of pneumonia caused by AmpC-non-hyperproducing strains of E. coli resistant to cefoxitin.

Biofilm formation in Acinetobacter baumannii: associated features and clinical implications.

Biofilm formation in 92 unrelated strains of Acinetobacter baumannii isolated in a multicentre cohort study was investigated using a microtitre plate assay. Fifty-six (63%) isolates formed biofilm. These isolates were less frequently resistant to imipenem or ciprofloxacin than were non-biofilm-forming isolates (25% vs. 47%, p 0.04; and 66% vs. 94%, p 0.004, respectively). All catheter-related urinary or bloodstream infections and the sole case of shunt-related meningitis were caused by biofilm-forming strains. Multivariate analysis revealed that treatment in an intensive care unit, ciprofloxacin resistance and isolation from a respiratory sample were associated with non-biofilm-forming isolates, while previous aminoglycoside use was associated with biofilm-forming isolates.

False extended-spectrum beta-lactamase detection in Acinetobacter spp. due to intrinsic susceptibility to clavulanic acid.

BACKGROUND: There are some reports showing the susceptibility of some strains of Acinetobacter baumannii to the beta-lactamase inhibitor clavulanic acid. To address this issue, we determined the MIC of clavulanic acid for a broad collection of Acinetobacter spp. isolates collected in a multicentre study. In addition, we showed the consequences of this susceptibility to yield false extended-spectrum beta-lactamase (ESBL) detection in this genus. METHODS: The strains used were 244 isolates of Acinetobacter (226 A. baumannii, 15 Acinetobacter genomic species 3 and 3 unidentified Acinetobacter spp.) and several A. baumannii as positive controls. The isolates were subjected to molecular typing. One isolate of each genotype was subjected to clavulanic acid MIC analysis. As no breakpoints for clavulanic acid are available, we arbitrarily established three categories of susceptibility: < or = 16, 32-128 and > or = 256 mg/L. The presence of ESBL in Acinetobacter spp. was analysed by using microdilution, double disc diffusion, combined discs, Etest and isoelectric focusing. RESULTS: A total of 100 different genotypes were detected. Among them, 44, 26 and 30 genotypes were inhibited by < or = 16, 32-128 and > or = 256 mg/L clavulanic acid, respectively. Representative isolates of each group were tested for ESBL production. Only those with the lower clavulanic acid MICs yielded a false-positive ESBL test with all methods tested with the exception of the double disc diffusion assay. CONCLUSIONS: Forty-four per cent of the genotypes tested were inhibited by < or = 16 mg/L clavulanic acid and these Acinetobacter isolates yielded a false ESBL-positive test. These results may have implications for susceptibility testing in routine microbiology laboratories.