Antimicrobial Resistance In Gram-negative Bacteria Research Articles

Isolation of Pseudomonas aeruginosa Coproducing Metallo-β-Lactamase SPM-1 and 16S rRNA Methylase RmtD1 in an Urban River

Pseudomonas aeruginosa (strain 48-1997A) producing Sao Paulo metallo-beta-lactamase (MBL)-1 (SPM-1) was described for the first time in 1997 and came from a 4-year-old leukemic girl in Sao Paulo, Brazil (15). Since then, SPM-1-producing P. aeruginosa has become endemic in Brazilian hospitals, being recurrently associated with outbreaks of nosocomial infection (8, 11, 12). More recently, the first reports of the MBL SPM-1 were described in Europe (14) and western Asia (GenBank accession no. {type:entrez-nucleotide,attrs:{text:HM370523.1,term_id:307949947,term_text:HM370523.1}}HM370523.1), denoting the potential for SPM-1 to become endemic worldwide (6). Unfortunately, carbapenem-resistant P. aeruginosa isolates carrying the SPM-1 enzyme have exhibited additional resistance to aminoglycosides, which has been mediated by a novel 16S rRNA methylase defined as RmtD (3), rendering ineffective a potent double-coverage regimen of a carbapenem plus an aminoglycoside and contributing to the emergence of panresistant phenotypes (3, 4). In this letter, we report the first environmentally isolated Pseudomonas aeruginosa carrying the blaSPM-1 and rmtD1 genes, providing additional data on the epidemiology of these genetic determinants of resistance. In August of 2010, during a surveillance study established to monitor the occurrence of antimicrobial resistance in Gram-negative bacteria from urban rivers in southeastern Brazil, a panresistant P. aeruginosa isolate (TIES-04900) was recovered from the Tiete River. Tiete is one of the main rivers of the region, which runs across Sao Paulo state from east to west for about 1,100 km. The water sample was collected from a dam located downstream of many important cities, including Sao Paulo, the largest and most populous metropolitan area in Brazil. P. aeruginosa strain TIES-04900 was resistant to imipenem, meropenem, ertapenem, ceftazidime, cefotaxime, cefepime, piperacillin-tazobactam, amikacin, tobramycin, gentamicin, ciprofloxacin, levofloxacin, and trimethoprim-sulfamethoxazole; remaining susceptible only to aztreonam and polymyxin B (Table 1). MBL production was confirmed by using an MBL Etest strip. Based on the antimicrobial susceptibility pattern and genetic backgrounds of multidrug-resistant P. aeruginosa strains reported from Brazil (4, 8), antibiotic resistance genes were studied by PCR and sequencing, confirming the presence of the blaSPM-1, blaOXA-56, rmtD1, aacA4, aadA7, sul1, and dhfr genes (GenBank accession numbers {type:entrez-nucleotide,attrs:{text:HQ876773,term_id:323099809,term_text:HQ876773}}HQ876773 to {type:entrez-nucleotide,attrs:{text:HQ876777,term_id:323099817,term_text:HQ876777}}HQ876777). This resistance genotype has been previously reported in clinical isolates of P. aeruginosa (3) and most likely has contributed to the endemicity of this panresistant phenotype in Brazilian hospitals (3, 4, 6, 8, 11, 12). In fact, enterobacterial repetitive intergenic consensus-PCR fingerprint analysis (Dice similarity coefficient and unweighted-pair group method using average linkages clustering), undertaken to ascertain the relatedness of TIES-04900 to clinical SPM-1- and RmtD-1-positive P. aeruginosa isolates (3, 15), showed that environmental P. aeruginosa TIES-04900 was clonally related to human P. aeruginosa strains PA0905 (95.2% similarity) and 48-1997A (90% similarity), previously identified in Sao Paulo (3, 15). Table 1. MICs of antibiotics for environmental Pseudomonas aeruginosa strain TIES-04900 carrying the blaSPM-1, blaOXA-56, rmtD1, aacA4, aadA7, sul1, and dhfr genesa In summary, we report the presence of SPM-1- and RmtD-1-coproducing P. aeruginosa in an urban river, showing that strains harboring the blaSPM-1 and rmtD1 genes seem not to be restricted to the hospital setting, a fact that emphasizes the importance of surveying environmental strains that might act as a source and/or reservoir of resistance genes with clinical relevance (1, 5, 7, 13) and have the potential for dissemination in communities through river environments (1, 10).

Correlation between antibiotic consumption and resistance of Gram-negative bacteria causing healthcare-associated infections at a university hospital in Taiwan from 2000 to 2009

This study investigated the correlation between antibiotic consumption and antimicrobial resistance in Gram-negative bacteria causing healthcare-associated infections at a university hospital in Taiwan from 2000 to 2009. Disc susceptibility data of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Proteus spp., Pseudomonas aeruginosa, Acinetobacter spp., Stenotrophomonas maltophilia and other non-fermentative Gram-negative bacilli causing healthcare-associated infections were evaluated. Data on annual patient-days and annual consumption (defined daily doses per 1000 patient-days) of extended-spectrum cephalosporins, β-lactam/β-lactamase inhibitor combinations, carbapenems, aminoglycosides and fluoroquinolones were analysed. The trend of total consumption of extended-spectrum cephalosporins, β-lactam/β-lactamase inhibitor combinations, carbapenems, aminoglycosides and fluoroquinolones significantly increased between 2000 and 2003 and remained stable between 2004 and 2009. The decreasing use of gentamicin and amikacin in recent years was associated with increasing susceptibility of E. coli, E. cloacae, S. marcescens and P. aeruginosa to gentamicin, as well as increasing susceptibility of P. aeruginosa to amikacin. The use of piperacillin/tazobactam was positively correlated with the prevalence of piperacillin/tazobactam-resistant E. coli and S. maltophilia. In contrast, the use of cefotaxime and piperacillin/tazobactam was negatively correlated with the prevalence of cefotaxime-resistant E. coli and piperacillin/tazobactam-resistant S. maltophilia, respectively. The consumption of fluoroquinolones was positively correlated with the rates of ciprofloxacin-resistant E. coli, piperacillin/tazobactam-resistant P. aeruginosa and ceftazidime-resistant S. maltophilia. The relationship between antibiotic prescription and the rates of resistance for Gram-negative bacteria is complicated; every type of antimicrobial agent or even individual agent can have distinct associations with different pathogens.

Does the Wide Use of Quaternary Ammonium Compounds Enhance the Selection and Spread of Antimicrobial Resistance and Thus Threaten Our Health?

Quaternary ammonium compounds (QACs) are widely used biocides that possess antimicrobial effect against a broad range of microorganisms. These compounds are used for numerous industrial purposes, water treatment, antifungal treatment in horticulture, as well as in pharmaceutical and everyday consumer products as preserving agents, foam boosters, and detergents. Resistance toward QACs is widespread among a diverse range of microorganisms and is facilitated by several mechanisms such as modifications in the membrane composition, expression of stress response and repair systems, or expression of efflux pump genes. Development of resistance in both pathogenic and nonpathogenic bacteria has been related to application in human medicine and the food industry. QACs in cosmetic products will inevitably come into intimate contact with the skin or mucosal linings in the mouth and thus are likely to add to the selection pressure toward more QAC-resistant microorganisms among the skin or mouth flora. There is increasing evidence of coresistance and cross-resistance between QACs and a range of other clinically important antibiotics and disinfectants. Use of QACs may have driven the fixation and spread of certain resistance cassette collectors (class 1 integrons), currently responsible for a major part of antimicrobial resistance in gram-negative bacteria. More indiscriminate use of QACs such as in cosmetic products may drive the selection of further new genetic elements that will aid in the persistence and spread of antimicrobial resistance and thus in limiting our treatment options for microbial infections.

Molecular Analysis of Antimicrobial Resistance in Gram-Negative Bacteria Isolated from Fish Farms in Egypt

As little is known about antimicrobial resistance genes in fish farms, this study was conducted to monitor the incidence and prevalence of a wide range of antimicrobial resistance genes in Gram-negative bacteria isolated from water samples taken from fish farms in the northern part of Egypt. Ninety-one out of two hundred seventy-four (33.2%) non-repetitive isolates of Gram-negative bacteria showed multidrug resistance phenotypes and harbored at least one antimicrobial resistance gene. PCR and DNA sequencing results showed that 72 (26.3%) isolates contain tetracycline resistance genes and 19 (6.9%) isolates were positive for class 1 integrons with 12 different gene cassettes. The beta-lactamase-encoding genes were identified in 14 (5.1%) isolates. The plasmid-mediated quinolone resistance genes, qnr and aac(6')-Ib-cr, were identified in 16 (5.8%) and 3 (1.1%) isolates, respectively. Finally, the florphenicol resistance gene, floR, was identified in four (1.5%) isolates. To the best of our knowledge, this is the first report for molecular characterization of antimicrobial resistance in Gram-negative bacteria isolated from fish farms in Africa.

Multiple Antimicrobial Resistance of Gram-Negative Bacteria from Natural Oligotrophic Lakes Under Distinct Anthropogenic Influence in a Tropical Region

The aim of this study was to evaluate the resistance to ten antimicrobial agents and the presence of bla ( TEM1 ) gene of Gram-negative bacteria isolated from three natural oligotrophic lakes with varying degrees of anthropogenic influence. A total of 272 indigenous bacteria were recovered on eosin methylene blue medium; they were characterized for antimicrobial resistance and identified taxonomically by homology search and phylogenetic comparisons. Based on 16S ribosomal RNA sequences analysis, 97% of the isolates were found to be Gram-negative bacteria; they belonged to 11 different genera. Members of the genera Acinetobacter, Enterobacter, and Pseudomonas predominated. Most of the bacteria were resistant to at least one antimicrobial. The incidence of resistance to beta-lactams, chloramphenicol, and mercury was high, whereas resistance to tetracycline, aminoglycosides, and nalidixic acid was low. There was a great frequency of multiple resistances among the isolates from the three lakes, although no significant differences were found among the disturbed and reference lakes. The ampicillin resistance mechanism of 71% of the isolates was due to the gene bla ( TEM1 ). Our study suggests that multiresistant Gram-negative bacteria and the bla ( TEM1 ) gene are common in freshwater oligotrophic lakes, which are subject to different levels of anthropogenic inputs.

Emergence of extensively drug-resistant and pandrug-resistant Gram-negative bacilli in Europe

International and local surveillance networks as well as numerous reports in the biomedical literature provide evidence that the prevalence of antibiotic resistant Gram-negative bacteria is escalating in many European countries. Furthermore, isolates characterised as multidrug-resistant (i.e. resistant to three or more classes of antimicrobials), extensively drug resistant (i.e. resistant to all but one or two classes) or pandrug-resistant (i.e. resistant to all available classes) are increasingly frequently isolated in hospitalised patients causing infections for which no adequate therapeutic options exist. Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae are specifically addressed in this review as the most problematic and often extensively or pandrug-resistant pathogens. According to the available multicentre surveillance studies, the proportion of imipenem-resistant A. baumannii strains is reported to be as high as 85% in bloodstream isolates from intensive care unit patients in Greece and 48% in clinical isolates from hospitalised patients in Spain and Turkey. Among 33 European countries participating in the European Antimicrobial Resistance Surveillance System (EARSS) in 2007, six countries reported carbapenem resistance rates of more than 25% among P. aeruginosa isolates, the highest rate reported from Greece (51%). According to EARSS, Greece has also the highest resistance rates among K. pneumoniae; 46% to carbapenems, 58% to quinolones and 63% to third generation cephalosporins. This review describes the magnitude of antimicrobial resistance in Gram-negative bacteria in Europe highlighting where the efforts of the scientific communities, the academia, the industry and the government should focus in order to confront this threat.

Microbiological surveillance of gram-negative bactaeremia in the intensive care unit: a teaching hospital experience

Background: The choice of empirical regimens for the treatment of Gram-negative bactaeremia requires a detailed knowledge of local susceptibility patterns. The emergence of multi-drug resistant pathogens and organisms producing extended-spectrum beta-lactamases limits the choice of suitable antimicrobial agents. We conducted surveillance of antimicrobial resistance in Gram-negative bacteria causing nosocomial bacteraemia in an adult intensive care unit in a London teaching hospital over an 18-month period.

Secular trends of antimicrobial resistance of blood isolates in a newly founded Greek hospital

BackgroundAntimicrobial resistance is one of the most challenging issues in modern medicine.MethodsWe evaluated the secular trends of the relative frequency of blood isolates and of the pattern of their in vitro antimicrobial susceptibility in our hospital during the last four and a half years.ResultsOverall, the data regarding the relative frequency of blood isolates in our newly founded hospital do not differ significantly from those of hospitals that are functioning for a much longer period of time. A noteworthy emerging problem is the increasing antimicrobial resistance of Gram-negative bacteria, mainly Acinetobacter baumannii and Klebsiella pneumoniae to various classes of antibiotics. Acinetobacter baumannii isolates showed an increase of resistance to amikacin (p = 0.019), ciprofloxacin (p = 0.001), imipenem (p < 0.001), and piperacillin/tazobactam (p = 0.01) between the first and second period of the study.ConclusionAn alarming increase of the antimicrobial resistance of Acinetobacter baumannii isolates has been noted during our study.

Relationships between antimicrobial use and antimicrobial resistance in Gram-negative bacteria causing nosocomial infections from 1991–2003 at a university hospital in Taiwan

This study was conducted to evaluate the relationship between antimicrobial resistance and antimicrobial use in a university hospital in Taiwan. Disk susceptibility data of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Proteus spp., Pseudomonas aeruginosa, Acinetobacter spp., Stenotrophomonas maltophilia and other non-fermentative Gram-negative bacilli causing nosocomial infections were evaluated. Data on annual patient-days and annual consumption (defined daily dose (DDD) per 1000 patient-days) of extended-spectrum cephalosporins (cefotaxime, ceftriaxone, ceftazidime, flumoxef, cefepime and cefpirome), β-lactam–β-lactamase inhibitor combinations (ticarcillin/clavulanic acid and piperacillin/tazobactam), carbapenems (imipenem and meropenem), aminoglycosides (amikacin, gentamicin and tobramycin), fluoroquinolones (ciprofloxacin (oral and injectable) and oral levofloxacin and moxifloxacin) from 1991 to 2003 were analysed. Increasing trends of incidences of several of these bacteria causing all nosocomial infections or nosocomial bloodstream infections were noted from 1991 to 2003. The annual patient-days of the hospital significantly increased, from 360 210 in 1991 to 672 676 in 2002 (linear regression analysis, P < 0.05), but slightly decreased in 2003 (629 168) owing to the severe acute respiratory syndrome epidemic in Taiwan. The rise in cefotaxime-resistant or ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa was significantly correlated with increased consumption of extended-spectrum cephalosporins, β-lactam–β-lactamase inhibitor combinations, carbapenems, fluoroquinolones and aminoglycosides (for ciprofloxacin-resistant E. coli and meropenem-resistant P. aeruginosa only) in the hospital (Pearson's correlation coefficient, r > 0.72 (or <−0.72) and P-value < 0.05). Increased ciprofloxacin-resistant K. pneumoniae and meropenem-resistant Acinetobacter spp. was significantly associated with the increased usage of extended-spectrum cephalosporins but not with the other four classes of antibiotics. This 13-year study in a hospital demonstrated significant changes in antimicrobial use, which may have affected antimicrobial resistance in certain Gram-negative bacteria at the hospital.

Occurrence and antimicrobial resistance of Gram-negative bacteria isolated in haemodialysis water and dialysate of renal units: results of a Greek multicentre study.

To evaluate the occurrence, identity and antimicrobial resistance of Gram-negative bacteria isolated from municipal water supplies, treated water, and dialysate of all 85 Greek haemodialysis centres. A total of 141 Gram-negative bacterial isolates (98 non-fermentative and 43 enterobacteria) were recovered from 255 water samples. Twenty-four of them were isolated from tap water, 31 from treated water, and 86 from dialysate samples. The mean concentrations (CFU per 100 ml +/- s.d.) of the positive Gram-negative bacteria samples were 69.2 +/- 43.9, 31.2 +/- 28.7 and 3552.3 +/- 4485.0, respectively. The most common isolates, in order of frequency were Pseudomonas aeruginosa (22.7%), Chryseobacterium meningosepticum (14.9%), Stenotrophomonas maltophilia (13.5%), Escherichia coli (12.8%) and Enterobacter cloacae (7.8%), representing 71.6% of all isolates. Ps. aeruginosa was the most prevalent isolate in all types of water sample followed by C. meningosepticum in tap and treated water and by E. coli in dialysate. Nineteen per cent of the enterobacteria and 35% of the non-fermenters were resistant against three or more of the nine antibiotics tested. These data suggest that dialysate and treated water could be a source of infection for several non-fermentative and enterobacterial species. Microbiological monitoring of such samples is needed in order to know the identity and antibiotic resistance profiles of their potentially pathogenic bacterial population.

Antimicrobial resistance in Gram-negative bacteria from Intensive Care Units and Urology Services. A nationwide study in The Netherlands 1995–2000

A nationwide 6-year surveillance of resistance in Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Pseudomonas aeruginosa from clinical specimens of patients from ten Intensive Care Units and ten Urology Services was started in 1995. MICs of amoxycillin, amoxycillin/clavulanate, trimethoprim, cotrimoxazole, norfloxacin, ciprofloxacin, cefaclor, ceftazidime, imipenem and gentamicin were determined by broth microdilution. Intensive Care Units had higher resistance levels of amoxycillin/clavulanate, cefaclor and ceftazidime ( P<0.005) and lower resistance levels of nitrofurantoin, trimethoprim, cotrimoxazole and quinolones ( P<0.01) than Urology Services. Changes in MIC distributions in time and development of resistant clusters were observed for nitrofurantoin ( E. coli), amoxycillin ( E. coli, P. mirabilis), amoxycillin/clavulanate ( E. coli) and for quinolones ( E. coli). The overall resistance level of ceftazidime and gentamicin was <5%, but this fluctuated with the appearance and disappearance of resistant clones in some Intensive Care Units. Quinolone resistance among P. aeruginosa from Intensive Care Units fluctuated between 7 and 14%.

Outer Membranes and Efflux: The Path to Multidrug Resistance in Gram- Negative Bacteria

Intrinsic and acquired multidrug resistance in Gram-negative bacteria owes much to the synergy between limited outer membrane permeability and energy-dependent multidrug efflux. The importance of the outer membrane vis-a-vis resistance is aptly demonstrated by the impact of mutational changes in outer membrane constituents on drug susceptibility. Changes in lipopolysaccharide (LPS) that correlate with increased drug susceptibility confirm, for example, the significance of this macromolecule in the intrinsic antimicrobial resistance of Gram-negative bacteria. Alterations in LPS and porins correlating with increased resistance to a variety of antimicrobials are also known and highlight the significance of the outer membrane vis-a-vis acquired antimicrobial resistance. Efflux systems accommodating a range of structurally distinct antimicrobials, including antibiotics, detergents, dyes, biocides and aromatic hydrocarbons have been identified in a number of Gram-negative organisms. Mutational studies have confirmed the importance of these systems to intrinsic and acquired antimicrobial resistance in important disease-causing organisms. As such, strategies aimed at thwarting efflux and or the outer membrane barrier are effective at reversing antimicrobial resistance in these organisms.

Antimicrobial resistance in gram-negative bacteria isolated from the urinary tract in community-residing persons with spinal cord injury

Antimicrobial resistance in gram-negative bacteria isolated from the urinary tract in community-residing persons with spinal cord injury

Antimicrobial resistance in gram-negative bacteria isolated from the urinary tract in community-residing persons with spinal cord injury

Objective: To assess the epidemiology of antimicrobial resistance among community-residing persons with spinal cord injury (SCI).Design: Retrospective analysis of existing data.Setting: Data were obtained from persons with SCI attending clinic for annual examinations.Participants: Two hundred eighty-seven SCI outpatients.Intervention: None.Main Outcome Measure: Occurrence of bacteriuria with gram-negative organisms demonstrating resistance to antimicrobial agents in 2 or more classes.Results: There were 706 gram-negative isolates from 444 urine specimens. Resistance to drugs in 2 or more classes occurred in 33% of bacterial isolates, but did not significantly increase in frequency among those injured for longer periods or more severely. Significantly higher rates of multidrug-resistant bacteria occurred in specimens from males, younger age group (≤45 yrs), and persons with indwelling and condom catheters.Conclusions: Antimicrobial resistance in outpatients with SCI is common and is related to widespread use of specific drugs, type of bladder management, and other host factors.

A surveillance study of antimicrobial resistance of gram-negative bacteria isolated from intensive care units in eight hospitals in Turkey.

This study was carried out with the participation of eight hospitals in Turkey to determine the frequency of gram-negative bacteria isolated in intensive care units (ICU) and to compare their resistance rates to selected antibiotics. Aerobic gram-negative bacteria isolated from ICUs during 1996 were studied. Antibiotic susceptibilities to imipenem, ceftazidime, ceftazidime-clavulanate, ceftriaxone, cefotaxime, cefepime, cefodizime, cefuroxime, piperacillin/tazobactam, amoxycillin-clavulanate, gentamicin, amikacin and ciprofloxacin were determined by Etest. A total of 748 isolates were obtained from 547 patients. The majority of organisms were isolated from the respiratory (38.8%) and urinary tracts (30.9%). Pseudomonas spp. were the most frequently isolated gram-negative species (26.8%), followed by Klebsiella spp. (26.2%). Escherichia coli, Acinetobacter spp. and Enterobacter spp. were the other commonly isolated organisms. High resistance rates were observed for all antibiotics studied. Imipenem appeared to be the most active agent against the majority of isolates. Although resistance rates exceeded 50%, ciprofloxacin, cefepime and amikacin were found to be relatively effective. Extended-spectrum beta-lactamase (ESBL) production appeared to be a major mechanism of resistance to beta-lactam antibiotics. In contrast to ceftazidime-clavulanate, piperacillin/tazobactam showed poor activity against organisms thought to produce ESBL, suggesting the presence of an enzyme resistant to tazobactam action. This study has yielded high rates of resistance in aerobic gram-negative isolates from ICUs in Turkey. High resistance rates to all the other antibacterials studied leave imipenem as the only reliable agent for the empirical treatment of ICU infections in Turkey.

Antimicrobial resistance of gram-negative bacteria isolated from foods in Mexico.

When trimethoprim-sulfamethoxazole was given to US travelers in Mexico to prevent diarrheal illness, high-level resistance to the drug emerged [2], although in previous studies such resistance had not been observed among enteric flora following administration of trimethoprim-sulfamethoxazole as prophylaxis against urinary tract infection [3]. Since food has been shown to be an important vehicle of transmission of travelers' diarrhea, food samples were examined for the presence of drug-resistant bacteria to explain the acquisition of high-level resistance among enteric flora of individuals taking antibiotics as prophylaxis against traveler's diarrhea. Of 34 strains of ETEC isolated from US students in Guadalajara, Mexico, who had acute gastroenteritis, one was resistant to trimethoprim and one was resistant to trimethoprim-sulfamethoxazole. Eight of the ETEC strains tested demonstrated multiple drug resistance. Twenty-two of 149 isolates from food produced enterotoxin. Only one isolate, which was nontoxigenic, was resistant to trimethoprim, and no coliforms were resistant to trimethoprim-sulfamethoxazole; however, 16 isolates demonstrated multiple drug resistance. Of 235 gram-negative organisms recovered from frozen food samples grown on antibiotic-containing media and tested for enterotoxin production, no isolates were enterotoxigenic. Thirty-four isolates were resistant to trimethoprim, 15 were resistant to trimethoprim-sulfamethoxazole, and 33 demonstrated multiple resistance. Multiple drug resistance was demonstrated among gram-negative organisms isolated from patients' stools and foods in Mexico.(ABSTRACT TRUNCATED AT 250 WORDS)