Ana Isabel Suárez

Roles of β-Lactamases and Porins in Activities of Carbapenems and Cephalosporins against Klebsiella pneumoniae

ABSTRACT Two clinical isolates of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae were noted to be less susceptible than expected to imipenem. Both were missing outer membrane proteins that serve as channels for antibiotic entry. The role of β-lactamase in resistance was investigated by eliminating the original ESBL and introducing plasmids encoding various ESBLs and AmpC β-lactamase types, by studying the effect of an increased inoculum, and by evaluating interactions with β-lactamase inhibitors. The contribution of porin deficiency was investigated by restoring a functional ompK36 gene on a plasmid. Plasmids encoding AmpC-type β-lactamases provided resistance to imipenem (up to 64 μg/ml) and meropenem (up to 16 μg/ml) in strains deficient in porins. Carbapenem resistance showed little inoculum effect, was not affected by clavulanate but was blocked by BRL 42715, and was diminished if OmpK36 porin was restored. Plasmids encoding TEM- and SHV-type ESBLs conferred resistance to cefepime and cefpirome, as well as to earlier oxyimino-β-lactams. This resistance was magnified with an increased inoculum, was blocked by clavulanate, and was also lowered by OmpK36 porin restoration. In addition, SHV-2 β-lactamase had a small effect on carbapenem resistance (imipenem MIC, 4 μg/ml, increasing to 16 μg/ml with a higher inoculum) when porins were absent. In K. pneumoniae porin loss can thus augment resistance provided either by TEM- or SHV-type ESBLs or by plasmid-mediated AmpC enzymes to include the latest oxyimino-β-lactams and carbapenems.

Initial Use of Echinocandins Does Not Negatively Influence Outcome in Candida parapsilosis Bloodstream Infection: A Propensity Score Analysis

BACKGROUND Concerns have arisen regarding the optimal antifungal regimen for Candida parapsilosis bloodstream infection (BSI) in view of its reduced susceptibility to echinocandins. METHODS The Prospective Population Study on Candidemia in Spain (CANDIPOP) is a prospective multicenter, population-based surveillance program on Candida BSI conducted through a 12-month period in 29 Spanish hospitals. Clinical isolates were identified by DNA sequencing, and antifungal susceptibility testing was performed by the European Committee on Antimicrobial Susceptibility Testing methodology. Predictors for clinical failure (all-cause mortality between days 3 to 30, or persistent candidemia for ≥72 hours after initiation of therapy) in episodes of C. parapsilosis species complex BSI were assessed by logistic regression analysis. We further analyzed the impact of echinocandin-based regimen as the initial antifungal therapy (within the first 72 hours) by using a propensity score approach. RESULTS Among 752 episodes of Candida BSI identified, 200 (26.6%) were due to C. parapsilosis species complex. We finally analyzed 194 episodes occurring in 190 patients. Clinical failure occurred in 58 of 177 (32.8%) of evaluable episodes. Orotracheal intubation (adjusted odds ratio [AOR], 2.81; P = .018) and septic shock (AOR, 2.91; P = .081) emerged as risk factors for clinical failure, whereas early central venous catheter removal was protective (AOR, 0.43; P = .040). Neither univariate nor multivariate analysis revealed that the initial use of an echinocandin-based regimen had any impact on the risk of clinical failure. Incorporation of the propensity score into the model did not change this finding. CONCLUSIONS The initial use of an echinocandin-based regimen does not seem to negatively influence outcome in C. parapsilosis BSI.

Time trends in the aetiology of prosthetic joint infections: a multicentre cohort study

It is important to know the spectrum of the microbial aetiology of prosthetic joint infections (PJIs) to guide empiric treatment and establish antimicrobial prophylaxis in joint replacements. There are no available data based on large contemporary patient cohorts. We sought to characterize the causative pathogens of PJIs and to evaluate trends in the microbial aetiology. We hypothesized that the frequency of antimicrobial-resistant organisms in PJIs has increased in the recent years. We performed a cohort study in 19 hospitals in Spain, from 2003 to 2012. For each 2-year period (2003-2004 to 2011-2012), the incidence of microorganisms causing PJIs and multidrug-resistant bacteria was assessed. Temporal trends over the study period were evaluated. We included 2524 consecutive adult patients with a diagnosis of PJI. A microbiological diagnosis was obtained for 2288 cases (90.6%). Staphylococci were the most common cause of infection (1492, 65.2%). However, a statistically significant rising linear trend was observed for the proportion of infections caused by Gram-negative bacilli, mainly due to the increase in the last 2-year period (25% in 2003-2004, 33.3% in 2011-2012; p 0.024 for trend). No particular species contributed disproportionally to this overall increase. The percentage of multidrug-resistant bacteria PJIs increased from 9.3% in 2003-2004 to 15.8% in 2011-2012 (p 0.008), mainly because of the significant rise in multidrug-resistant Gram-negative bacilli (from 5.3% in 2003-2004 to 8.2% in 2011-2012; p 0.032). The observed trends have important implications for the management of PJIs and prophylaxis in joint replacements.

Activities of Gemifloxacin and Five Other Antimicrobial Agents against Listeria monocytogenes and Coryneform Bacteria Isolated from Clinical Samples

ABSTRACT The in vitro activities of gemifloxacin, ciprofloxacin, ampicillin, doxycycline, gentamicin, and vancomycin were evaluated against 15Listeria monocytogenes strains and 205 coryneform bacteria isolated from clinical samples. The percentages of strains inhibited by gemifloxacin at 0.5 μg/ml were 100% (L. monocytogenes), 93.3% (Brevibacterium spp.), 90% (Corynebacterium minutissimum), 42.5% (Corynebacterium amycolatum), 20% (Corynebacterium striatum), 12.5% (Corynebacterium jeikeium), and 10% (Corynebacterium urealyticum). One hundred percent of the L. monocytogenes strains were inhibited by 0.25 μg of gemifloxacin per ml, whereas 0% of the strains were inhibited by 0.25 μg of ciprofloxacin per ml. Vancomycin at 2 μg/ml inhibited all strains. Doxycycline and gentamicin at 4 μg/ml inhibited 94 and 49% of the strains, respectively, while ampicillin at 0.5, 2, and 8 μg/ml inhibited 24, 61, and 66% of the strains, respectively. It is concluded that gemifloxacin shows good in vitro activity againstL. monocytogenes and coryneform bacteria exceptC. jeikeium and C. urealyticum.

Comparative in vitro activities of new quinolones against coryneform bacteria.

The in vitro activities of eight quinolones against 115 coryneform bacteria (20 Corynebacterium jeikeium, 15 Corynebacterium minutissimum, 15 Corynebacterium striatum, 25 Corynebacterium urealyticum, 10 Corynebacterium xerosis, 10 Corynebacterium group ANF-1, 10 Corynebacterium group 12, and 10 Listeria monocytogenes) were determined. The MICs of ciprofloxacin, ofloxacin, and sparfloxacin for 90% of C. jeikeium, C. urealyticum, and C. xerosis isolates tested were > 16 micrograms/ml. Those of BAY Y 3118 and clinafloxacin against these species were 0.5 and 1 to 2 micrograms/ml, respectively. The MICs for 90% of all 115 strains tested were 0.5 microgram/ml for BAY Y 3118, 1 microgram/ml for clinafloxacin, 2 micrograms/ml for E-5068, 4 micrograms/ml for E-5065, and > 16 micrograms/ml for ciprofloxacin, ofloxacin, sparfloxacin, and E-4868.

Comparative activities of eight quinolones against members of the Bacteroides fragilis group.

The in vitro activities of five new quinolones (clinafloxacin [CI-960 or PD-127391], BAY Y 3118, E-4868, E-5065, and E-5068) against 100 Bacteroides fragilis group bacterial isolates were compared with those of ciprofloxacin, ofloxacin, and sparfloxacin. Overall, E-5068 was the most active in vitro (MIC for 90% of isolates tested [MIC90], 0.25 microgram/ml); this was followed by clinafloxacin and BAY Y 3118 (MIC90, 0.5 microgram/ml). Ciprofloxacin, sparfloxacin, and ofloxacin were the least active (MIC90s, 64, 16, and 16 micrograms/ml, respectively). B. fragilis and Bacteroides caccae were more susceptible than the other members of the B. fragilis group to all of the quinolones tested.

Empirical and targeted therapy of candidemia with fluconazole versus echinocandins: a propensity score–derived analysis of a population-based, multicentre prospective cohort

We compared the clinical efficacy of fluconazole and echinocandins in the treatment of candidemia in real practice. The CANDIPOP study is a prospective, population-based cohort study on candidemia carried out between May 2010 and April 2011 in 29 Spanish hospitals. Using strict inclusion criteria, we separately compared the impact of empirical and targeted therapy with fluconazole or echinocandins on 30-day mortality. Cox regression, including a propensity score (PS) for receiving echinocandins, stratified analysis on the PS quartiles and PS-based matched analyses, were performed. The empirical and targeted therapy cohorts comprised 316 and 421 cases, respectively; 30-day mortality was 18.7% with fluconazole and 33.9% with echinocandins (p 0.02) in the empirical therapy group and 19.8% with fluconazole and 27.7% with echinocandins (p 0.06) in the targeted therapy group. Multivariate Cox regression analysis including PS showed that empirical therapy with fluconazole was associated with better prognosis (adjusted hazard ratio 0.38; 95% confidence interval 0.17-0.81; p 0.01); no differences were found within each PS quartile or in cases matched according to PS. Targeted therapy with fluconazole did not show a significant association with mortality in the Cox regression analysis (adjusted hazard ratio 0.77; 95% confidence interval 0.41-1.46; p 0.63), in the PS quartiles or in PS-matched cases. The results were similar among patients with severe sepsis and septic shock. Empirical or targeted treatment with fluconazole was not associated with increased 30-day mortality compared to echinocandins among adults with candidemia.

Activities of ABT-773 against Listeria monocytogenes and Coryneform Bacteria of Clinical Interest

ABSTRACT The in vitro activities of ABT-773 were evaluated against 15 Listeria monocytogenes strains and 196 coryneform bacteria isolated from clinical samples. One hundred percent of the L. monocytogenes strains were inhibited by ≤0.015 μg of ABT-773/ml. MICs of ABT-773 (μg/ml) at which 50% of the isolates tested were inhibited (MIC50s) and MIC90s for other organisms were 0.125 and 0.5 (Corynebacterium amycolatum), 1 and >32 (Corynebacterium jeikeium), 0.03 and >32 (Corynebacterium minutissimum), >32 and >32 (Corynebacterium pseudodiphtheriticum and Corynebacterium urealyticum), 0.125 and >32 (Corynebacterium striatum), and 0.03 and 0.5 (Rhodococcus equi), respectively.

Evolution of the antimicrobial susceptibility of B. fragilis group at the university hospital of Seville (Spain) between 1977 and 1995

A susceptibility survey of the B. fragilis group divided into three periods was carried out between 1977 and 1995 at the University Hospital of Seville (Spain) using the agar dilution method. No chloramphenicol, imipenem or meropenem-resistant strains were found. Metronidazole-resistant strains (2%) were isolated only in the first period. The most active beta-lactam drugs were piperacillin and ceftizoxime (resistance rate 16%), followed by ticarcillin mezlocillin and azlocillin (25%) and cefotaxime, cefotetam, and cefmetazol (around 40%). All strains tested were resistant to ampicillin and 4% to ampicillin/sulbactam. Cefoxitin resistance increased from 10% in the first two periods to 21% in the third and that of clindamycin from 12% in 1982 to 29% in 1987 and 50% in 1995.

Evaluation of in vitro activity of a new fluoroquinolone trovafloxacin (cp-99,219) compared with other anti-anaerobic antimicrobials against members of the Bacteroides fragilis group

The in vitro activity of a new fluoroquinolone, trovafloxacin (CP-99,219) was compared with that of ten other agents against 100 clinical isolates in the Bacteroides fragilis group. Trovafloxacin was the most active quinolone (MIC(90), 1 microg/ml) followed by sparfloxacin (MIC(90), 8 microg/ml), levofloxacin (MIC(90), 16 microg/ml) and ofloxacin (MIC(90), 32 microg/ml). Ciprofloxacin was the least active quinolone (MIC(90), 64 microg/ml). Metronidazole, chloramphenicol, imipenem and piperacillin/tazobactam, showed excellent activity with an MIC(90) of 1, 8, 0.25 and 16 microg/ml, respectively. Cefoxitin showed good activity and piperacillin was the least active compound. B. vulgatus and B. ovatus were the most resistant species to trovafloxacin among those of the B.fragilis group with an MIC(90) of 4 microg/ml while B. fragilis and B. thetaiotaomicron were the most susceptible (MIC(90), 1 microg/ml).