María Eliecer Cano

Plasmid-mediated quinolone resistance: an update

In 1998, the first plasmid-mediated gene involved in quinolone resistance (currently named qnrA1) was reported. Extra qnr-like plasmid-mediated genes (qnrB, qnrS, qnrC, qnrD) and their chromosomal homologues have also been characterized. These genes code for a pentapeptide repeat protein that protects type II topoisomerases from quinolones. Since then, there have been reports of two other plasmid-mediated resistance mechanisms: the modification of quinolones with a piperazinyl substituent by the acetyltransferase, Aac(6′)-Ib-cr; and active efflux by QepA and OqxAB, pumps related to major facilitator superfamily (MFS) transporters. These genes have a wide geographic distribution (mainly in Enterobacteriaceae). Because of the difficulties of phenotypic detection of this type of resistance, its real prevalence is only partially known. One important point is that although these mechanisms cause only low-level resistance, they favor and complement the selection of other resistance mechanisms.

Plasmid-mediated quinolone resistance.

The first plasmid-mediated gene involved in quinolone resistance (qnrA1) was reported in 1998. It codes for a pentapeptide-repeat protein that protects type II topoisomerases from quinolones. Additional related plasmid-mediated genes (qnrB, qnrS and qnrC) and chromosomal homologs of them have also been discovered. Two other plasmid-mediated resistance mechanisms were later reported: modification of quinolones with a piperazinyl substituent by the acetyltransferase Aac(6´)-Ib-cr and active efflux by QepA, a pump related to the major facilitator superfamily transporters. These genes have a wide geographical distribution (essentially in enterobacteria), although their real prevalence is only partially known because of the difficulty of phenotypic detection of this type of resistance. Although these mechanism cause low-level resistance, they favor and complement the selection of additional mechanisms of resistance.

Mutant Prevention Concentrations of Fluoroquinolones for Enterobacteriaceae Expressing the Plasmid-Carried Quinolone Resistance Determinant qnrA1

ABSTRACT The influence of qnrA1 on the development of quinolone resistance in Enterobacteriaceae was evaluated by using the mutant prevention concentration parameter. The expression of qnrA1 considerably increased the mutant prevention concentration compared to strains without this gene. In the presence of qnrA1, mutations in gyrA and parC genes were easily selected to produce high levels of quinolone resistance.

Effect of appropriate combination therapy on mortality of patients with bloodstream infections due to carbapenemase-producing Enterobacteriaceae (INCREMENT): a retrospective cohort study

BACKGROUND The best available treatment against carbapenemase-producing Enterobacteriaceae (CPE) is unknown. The objective of this study was to investigate the effect of appropriate therapy and of appropriate combination therapy on mortality of patients with bloodstream infections (BSIs) due to CPE. METHODS In this retrospective cohort study, we included patients with clinically significant monomicrobial BSIs due to CPE from the INCREMENT cohort, recruited from 26 tertiary hospitals in ten countries. Exclusion criteria were missing key data, death sooner than 24 h after the index date, therapy with an active antibiotic for at least 2 days when blood cultures were taken, and subsequent episodes in the same patient. We compared 30 day all-cause mortality between patients receiving appropriate (including an active drug against the blood isolate and started in the first 5 days after infection) or inappropriate therapy, and for patients receiving appropriate therapy, between those receiving active monotherapy (only one active drug) or combination therapy (more than one). We used a propensity score for receiving combination therapy and a validated mortality score (INCREMENT-CPE mortality score) to control for confounders in Cox regression analyses. We stratified analyses of combination therapy according to INCREMENT-CPE mortality score (0-7 [low mortality score] vs 8-15 [high mortality score]). INCREMENT is registered with ClinicalTrials.gov, number NCT01764490. FINDINGS Between Jan 1, 2004, and Dec 31, 2013, 480 patients with BSIs due to CPE were enrolled in the INCREMENT cohort, of whom we included 437 (91%) in this study. 343 (78%) patients received appropriate therapy compared with 94 (22%) who received inappropriate therapy. The most frequent organism was Klebsiella pneumoniae (375 [86%] of 437; 291 [85%] of 343 patients receiving appropriate therapy vs 84 [89%] of 94 receiving inappropriate therapy) and the most frequent carbapenemase was K pneumoniae carbapenemase (329 [75%]; 253 [74%] vs 76 [81%]). Appropriate therapy was associated with lower mortality than was inappropriate therapy (132 [38·5%] of 343 patients died vs 57 [60·6%] of 94; absolute difference 22·1% [95% CI 11·0-33·3]; adjusted hazard ratio [HR] 0·45 [95% CI 0·33-0·62]; p<0·0001). Among those receiving appropriate therapy, 135 (39%) received combination therapy and 208 (61%) received monotherapy. Overall mortality was not different between those receiving combination therapy or monotherapy (47 [35%] of 135 vs 85 [41%] of 208; adjusted HR 1·63 [95% CI 0·67-3·91]; p=0·28). However, combination therapy was associated with lower mortality than was monotherapy in the high-mortality-score stratum (30 [48%] of 63 vs 64 [62%] of 103; adjusted HR 0·56 [0·34-0·91]; p=0·02), but not in the low-mortality-score stratum (17 [24%] of 72 vs 21 [20%] of 105; adjusted odds ratio 1·21 [0·56-2·56]; p=0·62). INTERPRETATION Appropriate therapy was associated with a protective effect on mortality among patients with BSIs due to CPE. Combination therapy was associated with improved survival only in patients with a high mortality score. Patients with BSIs due to CPE should receive active therapy as soon as they are diagnosed, and monotherapy should be considered for those in the low-mortality-score stratum. FUNDING Spanish Network for Research in Infectious Diseases, European Development Regional Fund, Instituto de Salud Carlos III, and Innovative Medicines Initiative.

Detection of Plasmid-Mediated Quinolone Resistance Genes in Clinical Isolates of Enterobacter spp. in Spain

ABSTRACT We have studied by PCR and DNA sequencing the presence of the qnrA, qnrB, qnrS, aac(6′)-Ib-cr, qepA, intI1, and ISCR1 genes in 200 clinical isolates of Enterobacter cloacae (n = 153) and E. aerogenes (n = 47) consecutively collected between January 2004 and October 2005 in two hospitals located in Santander (northern Spain) and Seville (southern Spain). Mutations in the quinolone resistance-determining region of gyrA and parC also were investigated in organisms containing plasmid-mediated quinolone resistance genes. The isolates had different resistant phenotypes, including AmpC hyperproduction, extended-spectrum β-lactamase production, resistance or decreased susceptibility to quinolones, and/or resistance to aminoglycosides. Among the 116 E. cloacae isolates from Santander, qnrS1, qnrB5, qnrB2, and aac(6′)-Ib-cr were detected in 22 (19%), 1 (0.9%), 1 (0.9%), and 3 (2.6%) isolates, respectively. Twenty-one, 17, and 2 qnrS1-positive isolates also contained blaLAP-1, intI1, and ISCR1, respectively. A qnrB7-like gene was detected in one E. aerogenes isolate from Santander. No plasmid-mediated quinolone resistance gene was detected in the isolates from Seville. The qnrS1-containing isolates corresponded to four pulsed-field gel electrophoresis patterns and showed various levels of resistance to quinolones. Six isolates were susceptible to nalidixic acid and presented reduced susceptibility to ciprofloxacin. The qnrS1 gene was contained in a conjugative plasmid of ca. 110 kb, and when the plasmid was transferred to recipient strains that did not have a specific mechanism of quinolone resistance, the ciprofloxacin MICs ranged from 0.047 to 0.125 μg/ml.

Epidemiologic and clinical impact of Acinetobacter baumannii colonization and infection: a reappraisal.

AbstractAcinetobacter baumannii is one of the most important antibiotic-resistant nosocomial bacteria. We investigated changes in the clinical and molecular epidemiology of A. baumannii over a 10-year period. We compared the data from 2 prospective multicenter cohort studies in Spain, one performed in 2000 (183 patients) and one in 2010 (246 patients), which included consecutive patients infected or colonized by A. baumannii. Molecular typing was performed by repetitive extragenic palindromic polymerase chain reaction (REP-PCR), pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST).The incidence density of A. baumannii colonization or infection increased significantly from 0.14 in 2000 to 0.52 in 2010 in medical services (p < 0.001). The number of non-nosocomial health care-associated cases increased from 1.2% to 14.2%, respectively (p < 0.001). Previous exposure to carbapenems increased in 2010 (16.9% in 2000 vs 27.3% in 2010, p = 0.03). The drugs most frequently used for definitive treatment of patients with infections were carbapenems in 2000 (45%) and colistin in 2010 (50.3%). There was molecular-typing evidence of an increase in the frequency of A. baumannii acquisition in non-intensive care unit wards in 2010 (7.6% in 2000 vs 19.2% in 2010, p = 0.01). By MSLT, the ST2 clonal group predominated and increased in 2010. This epidemic clonal group was more frequently resistant to imipenem and was associated with an increased risk of sepsis, although not with severe sepsis or mortality.Some significant changes were noted in the epidemiology of A. baumannii, which is increasingly affecting patients admitted to conventional wards and is also the cause of non-nosocomial health care-associated infections. Epidemic clones seem to combine antimicrobial resistance and the ability to spread, while maintaining their clinical virulence.

Epidemiologic and clinical impact of acinetobacter baumannii colonization and infection

AbstractAcinetobacter baumannii is one of the most important antibiotic-resistant nosocomial bacteria. We investigated changes in the clinical and molecular epidemiology of A. baumannii over a 10-year period. We compared the data from 2 prospective multicenter cohort studies in Spain, one performed in 2000 (183 patients) and one in 2010 (246 patients), which included consecutive patients infected or colonized by A. baumannii. Molecular typing was performed by repetitive extragenic palindromic polymerase chain reaction (REP-PCR), pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST).The incidence density of A. baumannii colonization or infection increased significantly from 0.14 in 2000 to 0.52 in 2010 in medical services (p < 0.001). The number of non-nosocomial health care-associated cases increased from 1.2% to 14.2%, respectively (p < 0.001). Previous exposure to carbapenems increased in 2010 (16.9% in 2000 vs 27.3% in 2010, p = 0.03). The drugs most frequently used for definitive treatment of patients with infections were carbapenems in 2000 (45%) and colistin in 2010 (50.3%). There was molecular-typing evidence of an increase in the frequency of A. baumannii acquisition in non-intensive care unit wards in 2010 (7.6% in 2000 vs 19.2% in 2010, p = 0.01). By MSLT, the ST2 clonal group predominated and increased in 2010. This epidemic clonal group was more frequently resistant to imipenem and was associated with an increased risk of sepsis, although not with severe sepsis or mortality.Some significant changes were noted in the epidemiology of A. baumannii, which is increasingly affecting patients admitted to conventional wards and is also the cause of non-nosocomial health care-associated infections. Epidemic clones seem to combine antimicrobial resistance and the ability to spread, while maintaining their clinical virulence.

Klebsiella pneumoniae strains producing extended-spectrum beta-lactamases in Spain: microbiological and clinical features.

ABSTRACT Extended-spectrum β-lactamases (ESBL) of the CTX-M, SHV, and TEM families were recognized in 76 (67%), 31 (27%), and 6 (5%) isolates, respectively, among 162 ESBL-producing Klebsiella pneumoniae (ESBL-Kp) strains obtained in a multicenter study in Spain. Predisposing factors for ESBL-Kp acquisition included invasive procedures, mechanical ventilation, and previous antimicrobial use.

Cultivos de vigilancia epidemiológica de bacterias resistentes a los antimicrobianos de interés nosocomial

Los cultivos de vigilancia epidemiologica y la tipificacion molecular han sido importantes aportaciones de la Microbiologia Clinica al control de la infeccion nosocomial. En este documento se ofrece informacion sobre recogida, transporte, conservacion y procesamiento de muestras para cultivos de vigilancia, criterios para la interpretacion de los resultados y la emision de los mismos en relacion con las bacterias de mayor interes en infeccion nosocomial. Se incluyen Staphylococcus aureus resistente a meticilina (SARM), Enterococcus spp. resistentes a glucopeptidos, enterobacterias productoras de betalactamasas de espectro extendido (BLEE), Acinetobacter baumannii multirresistente y Pseudomonas aeruginosa resistente a carbapenems. Esta informacion pretende aportar una aproximacion general al problema, a partir de la cual el laboratorio desarrolle directrices propias, en funcion de las necesidades acordadas con el equipo multidisciplinar de control de infeccion nosocomial.

Outbreak of invasive group A streptococcal disease among children attending a day-care center.

Background: Most cases of invasive group A streptococcal (GAS) disease arise sporadically in the community, but outbreaks of severe invasive GAS infections have been reported in closed environments, such as military populations, family communities and hospitals. An outbreak of invasive GAS disease involving 3 cases of streptococcal toxic shock syndrome (TSS), one with a fatal course, occurred among children attending a day-care center located in Cantabria, Northern Spain. Objective: To determine the characteristics of GAS isolates obtained from the outbreak environment. Methods: GAS isolates obtained from children attending the same day-care facility, staff members, and family contacts were assayed for emm typing, pulse-field gel electrophoresis (PFGE), and toxin-gene content. One isolate obtained from the fatal case was also characterized by multilocus sequence typing. Antimicrobial susceptibility testing was done. Strains from patients unrelated to the outbreak were included for comparison. Results: All GAS isolates from children attending the day-care center, including those from streptococcal TSS cases, shared the same emm type 4, genomic pattern by PFGE (A) and toxin-gene profile. Neither the emm type nor the PFGE pattern or toxin gene profile of the outbreak-associated strains were encountered among GAS isolated from household or staff contacts. Conclusions: A clone of GAS belonging to emm type 4 and characterized by a specific PFGE pattern and toxin-gene profile was responsible for a community outbreak of streptococcal TSS disease in a child day-care center in Spain. This is the first day-care outbreak reported in our country.