Laura Calatayud

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 β-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).

Bacteraemia due to extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) in cancer patients: clinical features, risk factors, molecular epidemiology and outcome

OBJECTIVES To assess the clinical features, risk factors, molecular epidemiology and outcome of extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) bacteraemia in hospitalized cancer patients. METHODS Episodes of ESBL-EC bacteraemia were compared with a susceptible control group in a 3 year prospective study. ESBL-EC strains were studied by PCR and isoelectric focusing, and molecular typing was performed by PFGE. RESULTS Out of 531 episodes of bacteraemia, 135 were caused by E. coli. Seventeen of these cases involved ESBL-EC-producing strains (12.6%). In the multivariate analysis, female gender [odds ratio (OR) 3.43; 95% confidence interval (CI) 1.03-11.4] and previous antibiotic therapy (OR 3.22; 95% CI 1.00-10.3) were found to be independent risk factors for ESBL acquisition. An analysis of ESBL-EC isolates revealed a polyclonal distribution with CTX-M predominance (59%). Patients with ESBL-EC bacteraemia were more likely to have received an inadequate empirical antibiotic therapy (65% versus 6%; P = 0.000), and the time to adequate therapy was longer in this group (0 versus 1.50 days; P = 0.000). The overall mortality rate was 22%, ranging from 20% to 35% (P = 0.20). Risk factors for mortality were solid tumour (OR 19.41; 95% CI 4.66-80.83), corticosteroid therapy (OR 3.04 95% CI 1.05-8.81) and intensive care unit admission (OR 248.24, 95% CI 18.49-3332.14). In neutropenic patients, ESBL-EC bacteraemia was associated with poorer outcome and a higher overall mortality rate (37.5% versus 6.5%; P = 0.01). CONCLUSIONS In our centre, ESBL-EC bacteraemia is frequent among cancer patients, especially in those exposed to antibiotic pressure. All ESBL-EC strains were unrelated and most of them carried a CTX-M group enzyme. Patients with ESBL-EC bacteraemia received inadequate empirical antibiotic therapy more frequently than patients carrying a susceptible strain, but significant differences in mortality could not be demonstrated.

Serotypes, Clones, and Mechanisms of Resistance of Erythromycin-Resistant Streptococcus pneumoniae Isolates Collected in Spain

ABSTRACT The aim of this study was to analyze the distributions of antibiotic susceptibility patterns, serotypes, phenotypes, genotypes, and macrolide resistance genes among 125 nonduplicated erythromycin-resistant Streptococcus pneumoniae clinical isolates collected in a Spanish point prevalence study. The prevalence of resistance to macrolides in this study was 34.7%. Multiresistance (to three or more antimicrobials) was observed in 81.6% of these strains. Among 15 antimicrobials studied, cefotaxime, moxifloxacin, telithromycin, and quinupristin-dalfopristin were the most active drugs. The most frequent serotypes of erythromycin-resistant isolates were 19F (25%), 19A (17%), 6B (12%), 14 (10%), and 23F (10%). Of the 125 strains, 109 (87.2%) showed the MLSB phenotype [103 had the erm(B) gene and 6 had both erm(B) and mef(E) genes]. Sixteen (12.8%) strains showed the M phenotype [14 with mef(E) and 2 with mef(A)]. All isolates were tested by PCR for the presence of the int, xis, tnpR, and tnpA genes associated with conjugative transposons (Tn916 family and Tn917). Positive detection of erm(B), tet(M), int, and xis genes related to the Tn916 family was found in 77.1% of MLSB phenotype strains. In 16 strains, only the tndX, erm(B), and tet(M) genes were detected, suggesting the presence of Tn1116, a transposon recently described for Streptococcus pyogenes. Five clones, namely, Sweden15A-25, clone19F ST87, Spain23F-1, Spain6B-2, and clone19A ST276, accounted for half of the MLSB strains. In conclusion, the majority of erythromycin-resistant pneumococci isolated in Spain had the MLSB phenotype, belonged to multiresistant international clones, and carried the erm(B), tet(M), xis, and int genes, suggesting the spread of transposons of the Tn916 family.

Nosocomial Outbreak Due to Extended-Spectrum-Beta-Lactamase- Producing Enterobacter cloacae in a Cardiothoracic Intensive Care Unit

ABSTRACT Enterobacter cloacae has been associated with several outbreaks, usually involving strains that overproduce chromosomal β-lactamase or, uncommonly, strains expressing extended-spectrum β-lactamases (ESBL). Only sporadic cases of ESBL-producing E. cloacae have been identified in our hospital in recent years. We describe the epidemiology and clinical and microbiological characteristics of an outbreak caused by ESBL-producing E. cloacae in a cardiothoracic intensive care unit (CT-ICU). Prospective surveillance of patients with infection or colonization by ESBL-producing E. cloacae among patients admitted to the CT-ICU was performed during the outbreak. Production of ESBL was determined by decreased susceptibility to expanded-spectrum cephalosporins and a positive double-disk test result. Clone relatedness was determined by pulsed-field gel electrophoresis (PFGE). From July to September 2005, seven patients in the CT-ICU with ESBL-producing E. cloacae were identified (four males; median age, 73 years; range, 45 to 76 years); six patients had cardiac surgery. Four patients developed infections; three had primary bacteremia, one had ventilator-associated pneumonia, and one had tracheobronchitis. ESBL-producing E. cloacae showed resistance to quinolones and aminoglycosides. PFGE revealed two patterns. Five isolates belonged to clone A; two carried a single ESBL (pI 8.2 and a positive PCR result for the SHV type), and three carried two ESBLs (pIs 8.1 and 8.2 and positive PCR results for the SHV and CTX-M-9 types). Isolates belonging to clone B carried a single ESBL (pI 5.4 and a positive PCR result for the TEM type). Review of antibiotic consumption showed increased use of cefepime and quinolones during June and July 2005. The outbreak was stopped by the implementation of barrier measures and cephalosporin restriction. ESBL production could be increasingly common in nosocomial pathogens other than Escherichia coli or Klebsiella pneumoniae.

Comparative In Vitro Activities of Linezolid, Telithromycin, Clarithromycin, Levofloxacin, Moxifloxacin, and Four Conventional Antimycobacterial Drugs against Mycobacterium kansasii

ABSTRACT Mycobacterium kansasii is one of the most pathogenic and frequent nontuberculous mycobacteria isolated from humans. Patients with adverse drug reactions, resistant isolates, or suboptimal response require alternative treatment regimens. One hundred forty-eight consecutive clinical isolates of M. kansasii were tested for antimicrobial susceptibilities by the BACTEC 460 system (NCCLS) with two different inoculation protocols, one conventional and one alternative. In the alternative protocol, the inoculum 12B vial was incubated until the growth index was between 250 and 500. Four conventional antimycobacterial drugs (isoniazid, rifampin, streptomycin, and ethambutol) were studied with standard critical concentrations. The in vitro activities of linezolid, telithromycin, clarithromycin, levofloxacin, and moxifloxacin were determined by measuring radiometric MICs. All isolates tested were identified as M. kansasii genotype I and were resistant to isoniazid at a concentration of 0.4 μg/ml. One hundred twenty isolates (81.1%) were inhibited by 1 μg of isoniazid per ml. A high level of resistance to isoniazid (>10 μg/ml) was observed in six isolates (4.1%). Only five strains (3.4%) were resistant to rifampin (>1 μg/ml). All isolates studied were susceptible to streptomycin and ethambutol. The MICs at which 90% of the isolates were inhibited (in micrograms per milliliter) were as follows: linezolid, 1 (range, ≤0.25 to 2); telithromycin, >16 (range, 4 to >16); clarithromycin, 0.5 (range, ≤0.03 to 1); levofloxacin, 0.12 (range, 0.12 to 0.25); and moxifloxacin, 0.06 (range, ≤0.06 to 0.12). The susceptibility testing results with both inoculation protocols showed perfect correlation. In conclusion, all M. kansasii isolates showed decreased susceptibility to isoniazid, but resistance to rifampin was infrequent. Quinolones, especially moxifloxacin, were the most active antimicrobial agents tested, followed by clarithromycin. Linezolid also showed good activity against these microorganisms, but telithromycins in vitro activity was poor.

Invasive Pneumococcal Disease in Healthy Adults: Increase of Empyema Associated with the Clonal-Type Sweden1-ST306

Background Adult invasive pneumococcal disease (IPD) occurs mainly in the elderly and patients with co-morbidities. Little is known about the clinical characteristics, serotypes and genotypes causing IPD in healthy adults. Methods We studied 745 culture-proven cases of IPD in adult patients aged 18–64 years (1996–2010). Patients were included in two groups: 1.) adults with co-morbidities, and 2.) healthy adults, who had no prior or coincident diagnosis of a chronic or immunosuppressive underlying disease. Microbiological studies included pneumococcal serotyping and genotyping. Results Of 745 IPD episodes, 525 (70%) occurred in patients with co-morbidities and 220 (30%) in healthy adults. The healthy adults with IPD were often smokers (56%) or alcohol abusers (18%). As compared to patients with co-morbidities, the healthy adults had (P<0.05): younger age (43.5+/−13.1 vs. 48.7+/−11.3 years); higher proportions of women (45% vs. 24%), pneumonia with empyema (15% vs. 7%) and infection with non-PCV7 serotypes including serotypes 1 (25% vs. 5%), 7F (13% vs. 4%), and 5 (7% vs. 2%); and lower mortality (5% vs. 20%). Empyema was more frequently caused by serotype 1. No death occurred among 79 patients with serotype 1 IPD. There was an emergence of virulent clonal-types Sweden1-ST306 and Netherlands7F-ST191. The vaccine serotype coverage with the PCV13 was higher in healthy adults than in patients with co-morbidities: 82% and 56%, respectively, P<0.001. Conclusion In this clinical study, one-third of adults with IPD had no underlying chronic or immunosuppressive diseases (healthy adults). They were often smokers and alcohol abusers, and frequently presents with pneumonia and empyema caused by virulent clones of non-PCV7 serotypes such as the Sweden1-ST306. Thus, implementing tobacco and alcohol abuse-cessation measures and a proper pneumococcal vaccination, such as PCV13 policy, in active smokers and alcohol abusers may diminish the burden of IPD in adults.

Serotype and Genotype Replacement among Macrolide-Resistant Invasive Pneumococci in Adults: Mechanisms of Resistance and Association with Different Transposons

ABSTRACT The aim of this study was to analyze trends in adult invasive pneumococcal disease (IPD) due to macrolide-resistant strains and to study the evolution of serotypes, genotypes, and macrolide-resistant determinants of strains collected in a prospective study between 1999 and 2007 in Barcelona, Spain. IPD due to macrolide-resistant strains of serotypes included in the 7-valent conjugate vaccine (PCV7) decreased from 2.16/100,000 (pre-PCV7 period, 1999 to 2001) to 0.80/100,000 (late-PCV7 period, 2005 to 2007) (P = 0.001), whereas IPD due to macrolide-resistant strains of non-PCV7 serotypes increased from 1.08/100,000 to 2.83/100,000 (P < 0.001). These changes were related to a fall of clones of PCV7 serotypes (ST81 [P < 0.05], ST90, ST315, and ST17) and an increase in new clones of serotypes 19A and 24F (ST230) and 33F (ST717) in the late-PCV7 period. The most common phenotype was MLSB (90.9%), related to the erm(B) gene. The frequent association between MLSB phenotype and tetracycline resistance [tet(M) gene], was related to transposons of the Tn916-family such as Tn6002 or Tn3872. In conclusion, overall adult IPD rates due to macrolide-resistant pneumococci stabilized between 1999 and 2007 in Barcelona. The decrease in macrolide-resistant PCV7 pneumococci was balanced by the increase in macrolide-resistant non-PCV7 pneumococci.

Smoking and alcohol abuse are the most preventable risk factors for invasive pneumonia and other pneumococcal infections

OBJECTIVES To determine the prevalence of smoking and alcohol abuse among patients with invasive pneumococcal disease (IPD) in order to promote prevention strategies. METHODS We prospectively studied all culture-proven IPD cases in patients aged ≥ 18 years during the period 1997-2011. The habits of smoking and alcohol abuse were evaluated. Pneumococcal serotyping was performed. RESULTS There were 1378 IPD cases, with a mean age of 61 ± 17 years; 65% were males. Compared to the general population aged 18-64 years, patients with IPD of the same age group were more often current smokers (57% vs. 35%, p < 0.001) and alcohol abusers (21% vs. 6%, p < 0.001). Among patients with IPD, young adults (aged 18-49 vs. 50-64 vs. ≥ 65 years) were more commonly current smokers (71% vs. 40% vs.14%, p < 0.001) and alcohol abusers (23% vs. 18% vs. 6%, p < 0.001). Males were more frequently smokers and alcohol abusers than females. Smokers and alcohol abusers more often had underlying diseases such as HIV infection and chronic liver disease. Pneumonia was more common in smokers and peritonitis in alcohol abusers. Alcohol abuse conferred higher mortality. Certain pneumococcal serotypes, such as serotypes 1, 8, and 23F, more frequently caused IPD in smokers, and serotypes 4, 11A, and 19F in alcohol abusers. CONCLUSIONS Smoking and alcohol abuse are the most preventable risk factors for IPD. Implementing smoking and alcohol abuse cessation programs and a pneumococcal vaccination schedule are essential to diminish the burden of pneumonia and other pneumococcal infections.

Molecular Epidemiology of Nontypeable Haemophilus influenzae Causing Community-Acquired Pneumonia in Adults

Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen which causes a variety of respiratory infections. The objectives of the study were to determine its antimicrobial susceptibility, to characterize the β-lactam resistance, and to establish a genetic characterization of NTHi isolates. Ninety-five NTHi isolates were analyzed by pulsed field gel electrophoresis (PFGE) and multi locus sequence typing (MLST). Antimicrobial susceptibility was determined by microdilution, and the ftsI gene (encoding penicillin-binding protein 3, PBP3) was PCR amplified and sequenced. Thirty (31.6%) isolates were non-susceptible to ampicillin (MIC≥2 mg/L), with 10 of them producing β-lactamase type TEM-1 as a resistance mechanism. After ftsI sequencing, 39 (41.1%) isolates showed amino acid substitutions in PBP3, with Asn526→ Lys being the most common (69.2%). Eighty-four patients were successfully treated with amoxicillin/clavulanic acid, ceftriaxone and levofloxacin. Eight patients died due either to aspiration or complication of their comorbidities. In conclusion, NTHi causing CAP in adults shows high genetic diversity and is associated with a high rate of reduced susceptibility to ampicillin due to alterations in PBP3. The analysis of treatment and outcomes demonstrated that NTHi strains with mutations in the ftsI gene could be successfully treated with ceftriaxone or fluoroquinolones.

Nontypable Haemophilus influenzae Displays a Prevalent Surface Structure Molecular Pattern in Clinical Isolates

Non-typable Haemophilus influenzae (NTHi) is a Gram negative pathogen that causes acute respiratory infections and is associated with the progression of chronic respiratory diseases. Previous studies have established the existence of a remarkable genetic variability among NTHi strains. In this study we show that, in spite of a high level of genetic heterogeneity, NTHi clinical isolates display a prevalent molecular feature, which could confer fitness during infectious processes. A total of 111 non-isogenic NTHi strains from an identical number of patients, isolated in two distinct geographical locations in the same period of time, were used to analyse nine genes encoding bacterial surface molecules, and revealed the existence of one highly prevalent molecular pattern (lgtF+, lic2A+, lic1D+, lic3A+, lic3B+, siaA−, lic2C+, ompP5+, oapA+) displayed by 94.6% of isolates. Such a genetic profile was associated with a higher bacterial resistance to serum mediated killing and enhanced adherence to human respiratory epithelial cells.