Experimental study of the efficacy of daptomycin for the treatment of cephalosporin-resistant pneumococcal meningitis.

OBJECTIVES: To determine the efficacy of daptomycin for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis using in vitro and in vivo methods. METHODS: In vitro killing curves were determined with clinically achievable CSF antibiotic concentrations. In a rabbit model of pneumococcal meningitis, we studied the efficacy (Δ cfu/mL) of daptomycin used at 15 and 25 mg/kg, comparing it with ceftriaxone 100 mg/kg/24 h and ceftriaxone plus vancomycin 30 mg/kg/24 h over a 26 h period against two different strains: HUB 2349 and ATCC 51916, with MICs of 2 and 32 mg/L of cefotaxime/ceftriaxone, respectively. RESULTS: The penetration of daptomycin into CSF ranged between 9% and 11%. Daptomycin therapy achieved an excellent response, being bactericidal within 2 h of antibiotic administration. Against strain HUB 2349, daptomycin at both doses was as effective as ceftriaxone plus vancomycin. Against the highly resistant strain, daptomycin 25 mg/kg was significantly better than ceftriaxone plus vancomycin at 2 and 6 h. CONCLUSIONS: Daptomycin at standard doses, and especially at high doses, may be a useful alternative for the treatment of penicillin- and cephalosporin-resistant pneumococcal meningitis.

Fosfomycin-daptomycin and other fosfomycin combinations as alternative therapies in experimental foreign-body infection by methicillin-resistant Staphylococcus aureus.

The efficacy of daptomycin, imipenem, or rifampin with fosfomycin was evaluated and compared with that of daptomycin-rifampin in a tissue cage model infection caused by methicillin-resistant Staphylococcus aureus (MRSA). Strain HUSA 304 was used. The study yielded the following results for MICs (in µg/ml): fosfomycin, 4; daptomycin, 1; imipenem, 0.25; and rifampin, 0.03. The study yielded the following results for minimum bactericidal concentration (MBC) (in µg/ml): fosfomycin, 8; daptomycin, 4; imipenem, 32; and rifampin, 0.5. Daptomycin-rifampin was confirmed as the most effective therapy against MRSA foreign-body infections. Fosfomycin combinations with high doses of daptomycin and rifampin were efficacious alternative therapies in this setting. Fosfomycin-imipenem was relatively ineffective and did not protect against resistance.

Impact of multidrug resistance on Pseudomonas aeruginosa ventilator-associated pneumonia outcome: predictors of early and crude mortality.

The prevalence of multidrug-resistant (MDR) Pseudomonas aeruginosa has increased over the past decade and a significant rise in these isolates in ventilator-associated pneumonia (VAP) has been observed. However, the impact of MDR on VAP outcome has not been analysed in depth. We investigated the risk factors for early and crude mortality in a retrospective study of microbiologically and clinically documented VAP. Ninety-one VAP episodes in 83 patients were included, 31 caused by susceptible P. aeruginosa and 60 by MDR strains, of which 42 (70 %) were extensively drug-resistant (XDR) P. aeruginosa. Thirteen episodes concomitantly presented P. aeruginosa bacteraemia, in seven of which the origin was the respiratory tract. Whereas susceptible P. aeruginosa episodes were more likely than MDR episodes to receive adequate empirical (68 % vs. 30 %; p < 0.001) and definitive antimicrobial therapy (96 % vs. 50 %; p < 0.001), susceptible P. aeruginosa VAP presented a trend towards early mortality (29 % vs. 15 %; p = 0.06). A logistic regression model with early mortality as the dependent variable identified multiorgan dysfunction syndrome (MODS) [odds ratio (OR) 10.4; 95 % confidence interval (CI) 1.7-63.5; p = 0.01] and inadequate antibiotic therapy (OR 4.27; 95 % CI 0.98-18.4; p = 0.052) as independent risk factors for early mortality. A similar analysis identified MODS (OR 4.31; 95 % CI 1.14-16.2; p = 0.03) as the only independent predictor of crude mortality. The severity of acute illness clinical presentation was the main predictor of mortality. Despite adequate antibiotic therapy, susceptible P. aeruginosa seems to cause major early mortality. Although adequate therapy is essential to treat VAP, the severity of acute illness is a more important factor than drug resistance.

Detection of blaCTX-M-15 in an integrative and conjugative element in four extensively drug-resistant Haemophilus parainfluenzae strains causing urethritis.

Haemophilus parainfluenzae is a commensal organism with rising numbers of multidrug-resistant (MDR) strains. This pathogen is of increasing clinical relevance in urogenital infection. The aim of this work was to identify and characterise the molecular mechanisms of resistance associated with four cephalosporin-resistant H. parainfluenzae strains collected from patients with urethritis. Antimicrobial resistance was determined by microdilution following European Committee on Antimicrobial Susceptibility Testing criteria. Strains were then analysed by whole-genome sequencing to determine clonal relationship and the molecular basis of antimicrobial resistance. Finally, a phylogenetic analysis was performed on all urogenital MDR strains of H. parainfluenzae previously isolated in our hospital. All strains were resistant to ß-lactams, macrolides, tetracycline, fluoroquinolones, chloramphenicol, cotrimoxazole, and aminoglycosides. The resistance profile was compatible with the presence of an extended-spectrum ß-lactamase (ESBL). Whole-genome sequencing detected blaCTX-M-15 that conferred high minimum inhibitory concentrations to cephalosporins in two novel integrative and conjugative elements (ICEHpaHUB6 and ICEHpaHUB7) that also harboured a blaTEM-1 ß-lactamase. This study shows a novel blaCTX-M-15 ESBL carried in an integrative conjugative element in four extensively drug-resistant H. parainfluenzae strains. This resistance determinant could be transmitted to other sexually transmitted pathogens and this is a cause for concern.

Activity of imipenem/relebactam against Enterobacterales and Pseudomonas aeruginosa in Spain. SMART 2016-2020.

OBJECTIVE: To determine susceptibility to the novel ß-lactam/ß-lactamase inhibitor combination imipenem/relebactam in clinical isolates recovered from intra-abdominal (IAI), urinary (UTI), respiratory (RTI) and bloodstream (BSI) infections in the SMART (Study for Monitoring Antimicrobial Resistance Trends) study in SPAIN during 2016 - 2020. METHODS: Broth microdilution MICs for imipenem/relebactam and comparators were determined by a central laboratory against isolates of Enterobacterales and Pseudomonas aeruginosa. MICs were interpreted using EUCAST-2021 breakpoints. RESULTS: In total, 5,210 Enterobacterales and 1,418 P. aeruginosa clinical isolates were analyzed. Imipenem/relebactam inhibited 98.8% of Enterobacterales. Distinguishing by source of infection susceptibility was 99.1% in BSI, 99.2% in IAI, 97.9% in RTI, and 99.2% in UTI. Of intensive care unit isolates (ICU) 97.4% were susceptible and of non-ICU isolates 99.2% were susceptible. In Enterobacterales, activity against Class A, Class B and Class D carbapenemases was 96.2%, 15.4% and 73.2%, respectively. In P. aeruginosa, imipenem/relebactam was active in 92.2% of isolates. By source of infection it was 94.8% in BSI, 92.9% in IAI, 91.7% in RTI, and 93.1% in UTI. An 88.7% of ICU isolates and 93.6% of non-ICU isolates were susceptible to imipenem/relebactam. Imipenem/relebactam remained active against P. aeruginosa ceftazidime-resistant (76.3%), cefepime-resistant (73.6%), imipenem-resistant (71.5%) and piperacillin-resistant (78.7%) isolates. Of all multidrug-resistant or difficult-to-treat resistance P. aeruginosa isolates, 75.1% and 46.2%, respectively, were susceptible to imipenem/relebactam. CONCLUSIONS: Imipenem/relebactam showed high rates of susceptibility in Enterobacterales and P. aeruginosa isolates from different sources of infection as well as depending on patients' location (ICU or non-ICU scenarios).

Efficacy of daptomycin-cloxacillin combination in experimental foreign-body infection due to methicillin-resistant Staphylococcus aureus.

Despite the use of daptomycin alone at high doses (greater than 6 mg/kg of body weight/day) against difficult-to-treat infections, clinical failures and resistance appeared. Recently, the combination daptomycin-cloxacillin showed enhanced efficacy in clearing bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA). The aim of this study was to evaluate the efficacy of daptomycin at usual and high doses (equivalent to 6 and 10 mg/kg/day in humans, respectively) in combination with cloxacillin in a rat tissue cage infection model by MRSA and to compare its efficacy to that of daptomycin-rifampin. We used MRSA strain ATCC BAA-39. In the log- and stationary-phase kill curves, daptomycin-cloxacillin improved the bactericidal activity of daptomycin, especially in log phase. For in vivo studies, therapy was administered intraperitoneally for 7 days with daptomycin at 100 mg/kg/day and 45/mg/kg/day (daptomycin 100 and daptomycin 45), daptomycin 100-cloxacillin at 200 mg/kg/12 h, daptomycin 45-cloxacillin, and daptomycin 100-rifampin at 25 mg/kg/12 h. Daptomycin-rifampin was the best therapy (P < 0.05). Daptomycin 45 was the least effective treatment and did not protect against the emergence of resistant strains. There were no differences between the two dosages of daptomycin plus cloxacillin in any situation, and both protected against resistance. The overall effect of the addition of cloxacillin to daptomycin was a significantly greater cure rate (against adhered bacteria) than that for daptomycin alone. In conclusion, daptomycin-cloxacillin enhanced modestly the in vivo efficacy of daptomycin alone against foreign-body infection by MRSA and was less effective than daptomycin plus rifampin. The benefits of adding cloxacillin to daptomycin should be especially evaluated against infections by rifampin-resistant MRSA and for protection against the emergence of daptomycin nonsusceptibility.

Extensively drug-resistant Pseudomonas aeruginosa: risk of bloodstream infection in hospitalized patients.

Several studies have suggested that resistance determinants usually reduce virulence. However, their contribution to decrease bloodstream infections is unclear. Our aim was to identify risk factors of extensively drug-resistant (XDR) Pseudomonas aeruginosa (PA) bacteremia and to assess the prevalence of XDR-PA bacteremia. A retrospective study of PA bloodstream infections in our patient population with at least one clinical sample isolate due to PA (2006-2007) was carried out. A total of 2,131 patients with PA clinical samples were detected. Among 1,657 patients with susceptible-PA isolates, 95 developed PA-susceptible bacteremia. Concomitantly, among 474 patients with multidrug-resistant (MDR)-PA isolates, 265 with XDR-PA, and 209 with non-XDR MDR-PA, 43 developed XDR-PA bacteremia and 13 non-XDR MDR-PA bacteremia, respectively. Pulsed-field gel electrophoresis (PFGE) revealed the clonal nature of the two predominant XDR-PA phenotypes and genetic heterogeneity in non-XDR MDR-PA phenotypes. The proportion of XDR-PA bacteremia was higher than the proportion of bacteremia in the susceptible-PA population (16 % vs. 6 %; p < 0.001). A logistic regression model identified prior exposure to fluoroquinolones [odds ratio (OR) 2.80; 95 % confidence interval (CI) 1.02 to 7.70] as the independent variable associated with XDR-PA bacteremia. Our study suggests that XDR-PA strains have a greater ability to develop bacteremia. It remains unclear as to whether this invasive capacity depends on clonal traits or on other virulence determinants.

Bacteraemia due to multidrug-resistant Gram-negative bacilli in cancer patients: risk factors, antibiotic therapy and outcomes.

OBJECTIVES: To assess the risk factors, antibiotic therapy and outcomes of multidrug-resistant Gram-negative bacilli (MDRGNB) bacteraemia in hospitalized patients with cancer. METHODS: Episodes of MDRGNB bacteraemia were compared with a susceptible control group in a 4 year prospective study. RESULTS: Of 747 bacteraemias, 372 (49.7%) were caused by a Gram-negative bacilli (GNB). Fifty-one of these (13.7%) were caused by a multidrug-resistant (MDR) strain. Previous antibiotics [odds ratio (OR) 3.57; 95% confidence interval (CI) 1.63-7.80] and urinary catheter (OR 2.41; 95% CI 1.01-5.74) were identified as independent risk factors for MDRGNB acquisition. The most frequent mechanism of resistance was extended-spectrum ß-lactamase (ESBL) production (45%), mainly by Escherichia coli, followed by Amp-C cephalosporinase hyperproduction (24%). Patients with MDRGNB bacteraemia more frequently received inadequate initial antibiotic therapy (69% versus 9%; P < 0.001) and time to adequate therapy was longer in this group (41% versus 4%; P < 0.001). Patients in the resistant group more frequently required intensive care unit (ICU) admission (14% versus 5%; P = 0.023), had greater need for mechanical ventilation (14% versus 3%; P = 0.005) and had a higher overall case-fatality rate (41% versus 21%; P = 0.003). Risk factors for mortality were solid tumour (OR 5.04; 95% CI 2.49-10.19), current corticosteroid use (OR 4.38; 95% CI 2.39-8.05), ICU admission (OR 11.40; 95% CI 3.19-40.74) and MDRGNB bacteraemia (OR 3.52; 95% CI 1.36-9.09). CONCLUSIONS: MDRGNB bacteraemia was common among cancer patients, especially in those exposed to antibiotics and urinary catheter. The most frequent mechanism of resistance was ESBL production. Patients with MDRGNB more frequently received inadequate empirical antibiotic therapy and presented poorer outcomes with a higher overall case-fatality rate (within 30 days).

Efficacy of fosfomycin and its combination with linezolid, vancomycin and imipenem in an experimental peritonitis model caused by a Staphylococcus aureus strain with reduced susceptibility to vancomycin.

The objective of this study was to evaluate the in vitro and in vivo efficacies of therapies including fosfomycin against clinical Staphylococcus aureus isolates with reduced susceptibility to vancomycin (hGISA). Time-kill curves were performed over 24 h. Peritonitis in C57BL/6 mice was induced by intraperitoneal inoculation of 10(8) CFU/ml. Four hours later (0 h), therapy was started and the treatment groups were: control (not treated), fosfomycin (100 mg/kg/5 h), vancomycin (60 mg/kg/5 h), imipenem (30 mg/kg/5 h), fosfomycin plus linezolid, fosfomycin plus vancomycin and fosfomycin plus imipenem, receiving subcutaneous therapy over 25 h. Bacterial counts in peritoneal fluid, bacteraemia and mortality rates were determined. In vitro, fosfomycin showed a synergistic effect when combined with the other antimicrobials tested. In the animal model, fosfomycin combinations were effective and significantly reduced the bacteraemia rates achieved in the control, imipenem and vancomycin groups (p < 0.05). The best combination in vivo was fosfomycin plus imipenem. Also, fosfomycin plus linezolid was significantly better than vancomycin alone, reducing the bacterial concentration in the peritoneal fluid. In conclusion, in vitro and in vivo, fosfomycin in combination with linezolid, vancomycin or imipenem exerted a good activity. Fosfomycin plus imipenem was the most active combination, decreasing 3 log CFU/ml, and appears to be a promising combination for clinical practice.

Antimicrobial activity of ceftolozane-tazobactam against Enterobacterales and Pseudomonas aeruginosa recovered during the Study for Monitoring Antimicrobial Resistance Trends (SMART) program in Spain (2016-2018).

OBJECTIVE: To analyse the susceptibility to ceftolozane-tazobactam and comparators in Enterobacterales and Pseudomonas aeruginosa isolates recovered from intraabdominal (IAI), urinary (UTI), respiratory (RTI) and bloodstream infection (BSI) in the SMART (Study for Monitoring Antimicrobial Resistance Trends) study. METHODS: The susceptibility of 5,351 isolates collected in 11 Spanish hospitals (2016-2018) were analysed (EUCAST-2020 criteria) by broth microdilution and were phenotypically studied for the presence of extended-spectrum beta-lactamases (ESBL). Ceftolozane-tazobactam and/or carbapenem resistant isolates were genetically characterized for ESBL and carbapenemases. RESULTS: Escherichia coli was the most frequent pathogen (49.3% IAI, 54.9% UTI, 16.7% RTI and 50% BSI), followed by Klebsiella pneumoniae (11.9%, 19.1%, 13.1% and 15.4%, respectively). P. aeruginosa was isolated in 9.3%, 5.6%, 32% and 9%, respectively. The frequency of isolates with ESBLs (2016-2017) was: 30.5% K. pneumoniae, 8.6% E. coli, 2.3% Klebsiella oxytoca and 0.7% Proteus mirabilis. Ceftolozane-tazobactam was very active against non-ESBL-(99.3% susceptible) and ESBL-(95.2%) producing E. coli being less active against K. pneumoniae (98% and 43.1%, respectively) isolates. CTX-M-15 was the most prevalent ESBL in E. coli (27.5%) and K. pneumoniae (51.9%) frequently associated with OXA-48-like carbapenemase. Overall, 93% of P. aeruginosa isolates were susceptible to ceftolozane-tazobactam, preserving this activity (>75%) in isolates resistant to other beta-lactams except in those resistant to meropenen or ceftazidime-avibactam. GES-5, PER-1, VIM-1/2 were the most prevalent enzymes in isolates resistant to ceftolozane-tazobactam. CONCLUSIONS: Ceftolozane-tazobactam showed high activity rates against isolates recovered in the SMART study although it was affected in K. pneumoniae and P. aeruginosa isolates with ESBL and/or carbapenemases.

Efficacy of usual and high doses of daptomycin in combination with rifampin versus alternative therapies in experimental foreign-body infection by methicillin-resistant Staphylococcus aureus.

The treatment of prosthetic joint infections caused by methicillin-resistant Staphylococcus aureus (MRSA) continues to be a challenge for the clinician. The aim of this study was to evaluate the efficacies of daptomycin at usual and high doses (equivalent to 6 and 10 mg/kg of body weight/day, respectively, in humans) and in combination with rifampin and to compare the activities to those of conventional anti-MRSA therapies. We used MRSA strain HUSA 304, with the following MICs and minimal bactericidal concentrations (MBCs), respectively: daptomycin, 1 µg/ml and 4 µg/ml; vancomycin, 2 µg/ml and 4 µg/ml; linezolid, 2 µg/ml and >32 µg/ml; and rifampin, 0.03 µg/ml and 0.5 µg/ml. In time-kill curves, only daptomycin and its combinations with rifampin achieved a bactericidal effect in log and stationary phases. For in vivo studies, we used a rat foreign-body infection model. Therapy was administered for 7 days with daptomycin at 100 mg/kg/day and 45/mg/kg/day, vancomycin at 50 mg/kg/12 h, rifampin at 25 mg/kg/12 h, and linezolid at 35 mg/kg/12 h, and each antibiotic was also combined with rifampin. Among monotherapies, daptomycin at 100 mg/kg/day and rifampin performed better than vancomycin and linezolid. In combination with rifampin, both dosages of daptomycin were significantly better than all other combinations, but daptomycin at 100 mg/kg/day plus rifampin achieved better cure rates at day 11 (P < 0.05) than daptomycin at 45 mg/kg/day plus rifampin. Resistant strains were found in monotherapies with rifampin and daptomycin at 45 mg/kg/day. In conclusion, daptomycin at high doses was the most effective monotherapy and also improved the efficacy of the combination with rifampin against foreign-body infections by MRSA. Clinical studies should confirm whether this combination may be considered the first-line treatment for foreign-body infections by MRSA in humans.

Pneumococcal pneumonia presenting with septic shock: host- and pathogen-related factors and outcomes.

BACKGROUND: Host- and pathogen-related factors associated with septic shock in pneumococcal pneumonia are not well defined. The aim of this study was to identify risk factors for septic shock and to ascertain patient outcomes. Serotypes, genotypes and antibiotic resistance of isolated strains were also analysed. METHODS: Observational analysis of a prospective cohort of non-severely immunosuppressed hospitalised adults with pneumococcal pneumonia. Septic shock was defined as a systolic blood pressure of <90 mm Hg and peripheral hypoperfusion with the need for vasopressors for >4 h after fluid replacement. RESULTS: 1041 patients with pneumococcal pneumonia diagnosed by Gram stain and culture of appropriate samples and/or urine antigen test were documented, of whom 114 (10.9%) had septic shock at admission. After adjustment, independent risk factors for shock were current tobacco smoking (OR, 2.11; 95% CI, 1.02 to 4.34; p = 0.044), chronic corticosteroid treatment (OR, 4.45; 95% CI, 1.75 to 11.32; p = 0.002) and serotype 3 (OR, 2.24; 95% CI, 1.12 to 4.475; p = 0.022). No significant differences were found in genotypes and rates of antibiotic resistance. Compared with the remaining patients, patients with septic shock required mechanical ventilation more frequently (37% vs 4%; p<0.001) and had longer length of stay (11 vs 8 days; p<0.001). The early (10% vs 1%; p<0.001) and overall case fatality rates (25% vs 5%; p<0.001) were higher in patients with shock. CONCLUSIONS: Septic shock is a frequent complication of pneumococcal pneumonia and causes high morbidity and mortality. Current tobacco smoking, chronic corticosteroid treatment and infection caused by serotype 3 are independent risk factors for this complication.

In vitro and in vivo activities of linezolid alone and combined with vancomycin and imipenem against Staphylococcus aureus with reduced susceptibility to glycopeptides.

The objective of this study was to evaluate the in vitro and in vivo efficacies of linezolid (35 mg/kg/5 h), vancomycin (60 mg/kg/5 h), imipenem (30 mg/kg/5 h), linezolid+imipenem, linezolid+vancomycin and vancomycin+imipenem against two clinical Staphylococcus aureus isolates with reduced susceptibility to glycopeptides using time-kill curves and the murine peritonitis model. Time-kill curves were performed over 24 h. For the murine peritonitis model, peritonitis was induced by the intraperitoneal inoculation of 10(8) CFU/ml of each bacterial strain. Four hours later (0 h), the mice were randomly assigned to a control group or to therapeutic groups receiving subcutaneous treatment for 25 h. Bacterial counts in peritoneal fluid, bacteraemia and mortality rates were determined. The time-kill curves showed that the addition of linezolid to imipenem yielded synergistic results after 24 h. The addition of linezolid decreased vancomycin activity. In the animal model, vancomycin and linezolid monotherapies produced comparable bacterial decreases in mice infected with each strain but linezolid achieved higher rates of blood sterilisation. Linezolid tested either in monotherapy or in combination showed similar efficacy against both strains in terms of bacterial killing, number of negative blood cultures and survival. Linezolid and vancomycin were moderately bactericidal and similar in efficacy against glycopeptide-intermediate or -resistant S. aureus. Linezolid combinations, as effective as linezolid tested alone, could be considered as alternative options for the treatment of glycopeptide-intermediate S. aureus (GISA) infections.

Assessment of trimethoprim-sulfamethoxazole susceptibility testing methods for fastidious Haemophilus spp.

OBJECTIVES: To compare the determinants of trimethoprim-sulfamethoxazole resistance with established susceptibility values for fastidious Haemophilus spp., to provide recommendations for optimal trimethoprim-sulfamethoxazole measurement. METHODS: We collected 50 strains each of Haemophilus influenzae and Haemophilus parainfluenzae at Bellvitge University Hospital. Trimethoprim-sulfamethoxazole susceptibility was tested by microdilution, E-test and disc diffusion using both Mueller-Hinton fastidious (MH-F) medium and Haemophilus test medium (HTM) following EUCAST and CLSI criteria, respectively. Mutations in folA, folP and additional determinants of resistance were identified in whole-genome-sequenced isolates. RESULTS: Strains presented generally higher rates of trimethoprim-sulfamethoxazole resistance when grown on HTM than on MH-F, independent of the methodology used (average MIC 2.6-fold higher in H. influenzae and 1.2-fold higher in H. parainfluenzae). The main resistance-related determinants were as follows: I95L and F154S/V in folA; 3- and 15-bp insertions and substitutions in folP; acquisition of sul genes; and FolA overproduction potentially linked to mutations in -35 and -10 promoter motifs. Of note, 2 of 19 H. influenzae strains (10.5%) and 9 of 33 H. parainfluenzae strains (27.3%) with mutations and assigned as resistant by microdilution were inaccurately considered susceptible by disc diffusion. This misinterpretation was resolved by raising the clinical resistance breakpoint of the EUCAST guidelines to ≤30 mm. CONCLUSIONS: Given the routine use of disc diffusion, a significant number of strains could potentially be miscategorized as susceptible to trimethoprim-sulfamethoxazole despite having resistance-related mutations. A simple modification to the current clinical resistance breakpoint given by the EUCAST guideline for MH-F ensures correct interpretation and correlation with the reference standard method of microdilution.

Weighting the impact of virulence on the outcome of Pseudomonas aeruginosa bloodstream infections.

OBJECTIVES: We assessed the association between the lethality of Pseudomonas aeruginosa in a Caenorhabditis elegans model and outcomes of P. aeruginosa bloodstream infections. METHODS: A total of 593 P. aeruginosa bloodstream isolates recovered from a prospective Spanish multicentre study were analysed. Clinical variables, susceptibility profiles and Type III Secretion System (TTSS) genotypes (exoU/exoS genes) were available from previous studies. A C. elegans virulence score (CEVS) was used, classifying the isolates into high (CEVS 4-5), intermediate (CEVS 3) and low (CEVS 1-2) virulence. The main outcome analysed was 30-day mortality. RESULTS: Up to 75% (446/593) of the isolates showed a high-virulence phenotype, and 17% (101/593) a low-virulence one. No association between virulence phenotype and the main outcome variable (30-day mortality) was found (29/101 (28.7%) versus 127/446 (28.5%), p 1). However, an inverse association between C. elegans virulence and multidrug-resistant and extensively drug-resistant profiles was documented (OR 0.655 (95% CI 0.571-0.751) and OR 0.523 (95% CI 0.436-0.627), p <0.001, respectively), whereas the exoU genotype was significantly more frequent among isolates showing high virulence (10/101 (9.9%) versus 112/446 (25.1%), p <0.001). Moreover, although significance was not reached, strains showing a high-virulence phenotype tended to be associated with community-acquired infections (1/101 (1%) versus 25/446 (5.6%), p 0.065), whereas low-virulence phenotypes tended to be associated with a higher illness severity (such as higher median Pitt score: 2 (1-4) versus 1 (0-3), p 0.036, or initial multiorgan dysfunction: 17/101 (16.8%) versus 41/446 (9.2%), p 0.024), with some underlying conditions (such as chronic renal failure 24/101 (23.8%) versus 59/446 (13.2%), p 0.013), and with the respiratory source of infections (17/101 (16.8%) versus 45/446 (10.1%), p 0.058). CONCLUSIONS: Our results indicate that the P. aeruginosa virulence phenotype in a C. elegans model correlates with virulence genotype (TTSS) and resistance profile, but it is a poor prognostic marker of mortality in bloodstream infections.

Efficacy of extended infusion of ß-lactam antibiotics for the treatment of febrile neutropenia in haematologic patients: protocol for a randomised, multicentre, open-label, superiority clinical trial (BEATLE).

BACKGROUND: Febrile neutropaenia (FN) is a very common complication in patients with haematological malignancies and is associated with considerable morbidity and mortality. Broad-spectrum antipseudomonal ß-lactam antibiotics (BLA) are routinely used for the treatment of cancer patients with FN. However, the clinical efficacy of BLA may be diminished in these patients because they present with pathophysiological variations that compromise the pharmacokinetic (PK) parameters of these antibiotics. Optimised administration of BLA in prolonged infusions has demonstrated better clinical outcomes in critically ill patients. However, there is a paucity of data on the usefulness of this strategy in patients with FN. The aim of this study is to test the hypothesis that the administration of BLA would be clinically more effective by extended infusion (EI) than by intermittent infusion (II) in haematological patients with FN. METHODS: A randomised, multicentre, open-label, superiority clinical trial will be performed. Patients with haematological malignancies undergoing chemotherapy or haematopoietic stem-cell transplant and who have FN and receive empirical antibiotic therapy with cefepime, piperacillin-tazobactam or meropenem will be randomised (1:1) to receive the antibiotic by EI (during half the time of the dosing interval) in the study group, or by II (30 min) in the control group. The primary endpoint will be clinical efficacy, defined as defervescence without modifying the antibiotic treatment administered within the first 5 days of therapy. The primary endpoint will be analysed in the intention-to-treat population. The secondary endpoints will be pharmacokinetic/pharmacodynamic (PK/PD) target achievement, bacteraemia clearance, decrease in C-reactive protein, overall (30-day) case-fatality rate, adverse events and development of a population PK model of the BLA studied. DISCUSSION: Data on the usefulness of BLA administration in patients with FN are scant. Only three clinical studies addressing this issue have been published thus far, with contradictory results. Moreover, these studies had some methodological flaws that limit the interpretation of their findings. If this randomised, multicentre, phase IV, open-label, superiority clinical trial validates the hypothesis that the administration of BLA is clinically more effective by EI than by II in haematological patients with FN, then the daily routine management of these high-risk patients could be changed to improve their outcomes. TRIAL REGISTRATION: European Clinical Trials Database: EudraCT 2018-001476-37. ClinicalTrials.gov, ID: NCT04233996.

Long-term follow-up trial of oral rifampin-cotrimoxazole combination versus intravenous cloxacillin in treatment of chronic staphylococcal osteomyelitis.

Oral therapies alternative to fluoroquinolones against staphylococcal chronic osteomyelitis have not been evaluated in comparative studies. Consecutive nonaxial Staphylococcus aureus chronic osteomyelitis cases were included in a comparative trial after debridement. Fifty patients were randomized: group A (n = 22) was treated with cloxacillin for 6 weeks intravenously plus 2 weeks orally (p.o.), and group B (n = 28) was treated with rifampin-cotrimoxazole for 8 weeks p.o. During follow-up (10 years), five relapses occurred: two (10%) in group A and three (11%) in group B. Foreign-body maintenance was associated with relapse (P = 0.016). Oral rifampin-cotrimoxazole treatment showed outcomes comparable to those for intravenous cloxacillin treatment.

Nosocomial outbreak of a non-cefepime-susceptible ceftazidime-susceptible Pseudomonas aeruginosa strain overexpressing MexXY-OprM and producing an integron-borne PSE-1 betta-lactamase.

Cefepime (FEP) and ceftazidime (CAZ) are broad-spectrum cephalosporins that display similar MICs for wild-type Pseudomonas aeruginosa strains. Recently, P. aeruginosa isolates showing a discordance in susceptibility to CAZ and FEP have been noted at the Hospital de Bellvitge in Barcelona, Spain, and a clustering was suspected. During the study period (March to December 2007), 51 patients, particularly those in an intensive care units (ICUs) (n = 29 [57%]), infected or colonized with at least one P. aeruginosa non-FEP-susceptible and CAZ-susceptible (Fep(ns) Caz(s)) phenotype strain were detected. Twenty-three (45%) patients were infected, and the respiratory tract was the most frequent site of infection. Changes in the consumption of antimicrobials in the ICUs were observed over time: a progressive reduction in the levels of consumption of carbapenems (247 defined daily doses [DDD]/1,000 patient days to 66 DDD/1,000 patient days; P = 0.008), after restriction of its use in 2006, and an expected increase in the rate of piperacillin-tazobactam use (42 DDD/1,000 patient days in 2004 to 200 DDD/1,000 patient days in 2007; P < 0.001). Throughout the whole study period, only a single clone of a P. aeruginosa Fep(ns) Caz(s) phenotype strain was identified by pulsed-field gel electrophoresis analysis to be associated with the hyperexpression of MexXY-OprM and the production of an integron-borne PSE-1 ss-lactamase. In conclusion, we identified an epidemic P. aeruginosa clone of an Fep(ns) Caz(s) phenotype strain involving 51 patients, in particular, ICU patients. The combination of the overexpression of an efflux pump and PSE-1 ss-lactamase production is associated with the multidrug-resistant phenotype. The dominant use of a single class of antibiotics could have provided the selective pressure required for the emergence and spread of this P. aeruginosa strain.

Influence of testing methodology on the tigecycline activity profile against presumably tigecycline-non-susceptible Acinetobacter spp.

OBJECTIVES: To compare the tigecycline activity profile against Acinetobacter spp. by Etest versus broth microdilution in isolates with high Etest MIC. METHODS: Acinetobacter spp. isolates with tigecycline MICs of >or=0.5 mg/L determined by commercially developed Etests strips (January 2006 to July 2007) in five Spanish hospitals were considered. Values were rounded to the nearest upper double-dilution. Susceptibility by broth microdilution following CLSI (formerly NCCLS) recommendations, as the reference method, was determined in a central laboratory. BSAC breakpoints were used: susceptible 2 mg/L. RESULTS: One hundred and forty-eight isolates were collected: 12 isolates with a tigecycline Etest MIC of 0.5 mg/L, 14 with 1 mg/L, 86 with 2 mg/L, 31 with 4 mg/L and 5 with 8 mg/L. Isolates with Etest MICs of 0.5-1 mg/L showed the same values by broth microdilution. Among isolates with Etest MICs of 2 mg/L, only 5.8% of strains showed the same value by both methods (88.4% showed values that were one or two dilutions lower by microdilution). None of the 36 isolates with Etest MICs of 4-8 mg/L showed the same value by both methods, with values at least two dilutions lower by microdilution. Weak correlation (R = 0.238; P or=2 mg/L for Acinetobacter spp. since strains with Etest MICs of 2-4 mg/L are susceptible when tested by microdilution. False non-susceptibility by Etest may exclude tigecycline as a therapeutic option in a field where multiresistance is the rule.

Evaluation of meropenem alone and combined with rifampin in the guinea pig model of pneumococcal meningitis.

Meropenem is a broad-spectrum carbapenem antibiotic that is highly active against the pathogens causing meningitis. The aims of this study was to determine the efficacies of meropenem alone and combined with rifampin against two Streptococcus pneumoniae strains with different susceptibility to beta-lactams using the guinea pig meningitis model and compare them with the standard ceftriaxone plus vancomycin therapy. All treatments except rifampin were bactericidal from 6 h. The addition of rifampin did not improve the activity of meropenem alone. Our results provide good evidence of the efficacy of meropenem in the treatment of penicillin- and cephalosporin-susceptible and -resistant pneumococcal meningitis similar to that of ceftriaxone plus vancomycin, suggesting that meropenem might be a good option in the management of this infection.