Meropenem-resistant Strains Research Articles

Pseudomonas aeruginosa-producing Metallo-β-lactamases (VIM, IMP, SME, and AIM) in the Clinical Isolates of Intensive Care Units, a University Hospital in Isfahan, Iran.

Background:Pseudomonas aeruginosa is a severe challenge for antimicrobial therapy, due to the chromosomal mutations or exhibition of intrinsic resistance to various antimicrobial agents such as most β-lactams. We undertook this study to evaluate the existence of SME, IMP, AIM, and VIM metallo-β-lactamases (MBL) encoding genes among P. aeruginosa strains isolated from Intensive Care Unit (ICU) patients in Al-Zahra Hospital in Isfahan, Iran.Materials and Methods:In a retrospective cross-sectional study that was conducted between March 2012 and April 2013, a total of 48 strains of P. aeruginosa were collected from clinical specimens of bedridden patients in ICU wards. Susceptibility test was performed by disc diffusion method. All of the meropenem-resistant strains were subjected to modified Hodge test for detection of carbapenemases. Multiplex polymerase chain reaction was performed for detection of blaVIM, blaIMP, blaAIM, and blaSME genes.Results:In disk diffusion method, imipenem and meropenem showed the most and colistin the least resistant antimicrobial agents against P. aeruginosa strains. Of the 48 isolates, 36 (75%) were multidrug resistant (MDR). Amplification of β-lactamase genes showed the presence of blaVIM genes in 7 (%14.6) strains and blaIMP genes in 15 (31.3%) strains. All of the isolates were negative for blaSME and blaAIM genes. We could not find any statistically significant difference among the presence of this gene and MDR positive, age, or source of the specimen.Conclusion:As patients with infections caused by MBL-producing bacteria are at an intensified risk of treatment failure, fast determination of these organisms is necessary. Our findings may provide useful insights in replace of the appropriate antibiotics and may also prevent MBLs mediated resistance problem.

Analysis of the pathogenic characteristics of 162 severely burned patients with bloodstream infection

To analyze the distribution and drug resistance of pathogen isolated from severely burned patients with bloodstream infection, so as to provide reference for the clinical treatment of these patients. Blood samples of 162 severely burned patients (including 120 patients with extremely severe burn) with bloodstream infection admitted into our burn ICU from January 2011 to December 2014 were collected. Pathogens were cultured by fully automatic blood culture system, and API bacteria identification panels were used to identify pathogen. Kirby-Bauer paper disk diffusion method was used to detect the drug resistance of major Gram-negative and -positive bacteria to 37 antibiotics including ampicillin, piperacillin and teicoplanin, etc. (resistance to vancomycin was detected by E test), and drug resistance of fungi to 5 antibiotics including voriconazole and amphotericin B, etc. Modified Hodge test was used to further identify imipenem and meropenem resistant Klebsiella pneumonia. D test was used to detect erythromycin-induced clindamycin resistant Staphylococcus aureus. The pathogen distribution and drug resistance rate were analyzed by WHONET 5.5. Mortality rate and infected pathogens of patients with extremely severe burn and patients with non-extremely severe burn were recorded. Data were processed with Wilcoxon rank sum test. (1) Totally 1 658 blood samples were collected during the four years, and 339 (20.4%) strains of pathogens were isolated. The isolation rate of Gram-negative bacteria, Gram-positive bacteria, and fungi were 68.4% (232/339), 24.5% (83/339), and 7.1% (24/339), respectively. The top three pathogens with isolation rate from high to low were Acinetobacter baumannii, Staphylococcus aureus, and Pseudomonas aeruginosa in turn. (2) Except for the low drug resistance rate to polymyxin B and minocycline, drug resistance rate of Acinetobacter baumannii to the other antibiotics were relatively high (81.0%-100.0%). Pseudomonas aeruginosa was sensitive to polymyxin B but highly resistant to other antibiotics (57.7%-100.0%). Enterobacter cloacae was sensitive to imipenem and meropenem, while its drug resistance rates to ciprofloxacin, levofloxacin, cefoperazone/sulbactam, cefepime, piperacillin/tazobactam were 25.0%-49.0%, and those to the other antibiotics were 66.7%-100.0%. Drug resistance rates of Klebsiella pneumoniae to cefoperazone/sulbactam, imipenem, and meropenem were low (5.9%-15.6%, two imipenem- and meropenem-resistant strains were identified by modified Hodge test), while its drug resistance rates to amoxicillin/clavulanic acid, piperacillin/tazobactam, cefepime, cefoxitin, amikacin, levofloxacin were 35.3%-47.1%, and those to the other antibiotics were 50.0%-100.0%. (3) Drug resistance rates of methicillin-resistant Staphylococcus aureus (MRSA) to most of the antibiotics were higher than those of the methicillin-sensitive Staphylococcus aureus (MSSA). MRSA was sensitive to linezolid, vancomycin, and teicoplanin, while its drug resistance rates to compound sulfamethoxazole, clindamycin, minocycline, and erythromycin were 5.3%-31.6%, and those to the other antibiotics were 81.6%-100.0%. Except for totally resistant to penicillin G and tetracycline, MSSA was sensitive to the other antibiotics. Fourteen Staphylococcus aureus strains were resistant to erythromycin-induced clindamycin. Enterococcus was sensitive to vancomycin and teicoplanin, while its drug resistance rates to linezolid, chloramphenicol, nitrofurantoin, and high unit gentamicin were low (10.0%-30.0%), and those to ciprofloxacin, erythromycin, minocycline, and ampicillin were high (60.0%-80.0%). Enterococcus was fully resistant to rifampicin. (4) Fungi was sensitive to amphotericin B, and drug resistance rates of fungi to voriconazole, fluconazole, itraconazole, and ketoconazole were 7.2%-12.5%. (5) The mortality of patients with extremely severe burn was higher than that of patients with non-extremely severe burn. The variety of infected pathogens in patients with extremely severe burn significantly outnumbered that in patients with non-extremely severe burn (Z=-2.985, P=0.005). The variety of pathogen in severely burned patients with bloodstream infection is wide, with the main pathogens as Acinetobacter baumannii, Staphylococcus aureus, and Pseudomonas aeruginosa, and the drug resistance situation is grim. The types of infected pathogen in patients with extremely severe burn are more complex, and the mortality of these patients is higher when compared with that of patients with non-extremely severe burn.

In vitro and in vivo activity of ML302F: a thioenolate inhibitor of VIM-subfamily metallo β-lactamases

The thioenol ML302F, recently identified as an inhibitor of class B metallo-β-lactamases (MBLs), restores antibiotic susceptibility to meropenem resistant strains in cells and the Galleria mellonella invertebrate model.

Characterization of a potential β-lactamase inhibitory metabolite from a marine Streptomyces sp. PM49 active against multidrug-resistant pathogens.

Actinobacteria is a prolific producer of complex natural products; we isolated a potential marine Streptomyces sp. PM49 strain from Bay of Bengal coastal area of India. The strain PM49 exhibited highly efficient antibacterial properties on multidrug-resistant pathogens with a zone of inhibition of 14-17 mm. SSF was adopted for the production of the secondary metabolites from PM49 with ISP2; utilizing agricultural wastes for compound extraction was also attempted. Bioactive fraction of Rf value 0.69 resolved using chloroform and ethyl acetate (1:1, v/v) was obtained and subjected to further analysis. Based on UV, IR, ESI-MS, and (1)H and (13)C NMR spectral analysis, it was revealed that the compound is closely similar to cyslabdan with a molecular mass of 467.66 corresponding to the molecular formula C25H41NO5S. ESBL and MBL production was screened in the hospital test isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus aureus. PCR amplification in the phenotypically positive strains was positive for bla IMP, bla SHV, bla CTX-M, and mec genes. The β-lactamase enzyme from tested strains had cephalosporinase activity with a 31-kDa protein and isolated compound from the strain possessing β-lactamase inhibitory potential. MIC of the active fraction was 16-32 μg/ml on ATCC strains; the ceftazidime and meropenem sensitive and resistant test strains showed MIC of 64-256 μg/ml. The Streptomyces sp. PM49 aerial mycelium was rectiflexibile; the 16S rRNA showed 99 % identity with Streptomyces rochei and submitted at Genbank with accession no JX904061.1.

Frequency of extended-spectrum β-lactamase (ESBL)-producing Gram-negative bacilli in a 200-bed multi-specialty hospital in Vellore district, Tamil Nadu, India

Extended-spectrum β-lactamase (ESBL) producers were reported only from hospital settings previously, but, nowadays, its common presence in community settings is evident from reports. Our primary aim was to assess the frequency of ESBL-producing Gram-negative bacteria (GNB) and their antibiogram pattern among the clinical isolates received during an 8-month time period. The clinical isolates which belonged to the family Enterobacteriaceae from the clinical specimens were included in the study. These clinical isolates were tested for ESBL production using the double-disk synergy test. In total, 301 patients were included in this study, of which 146 (48.50%) were found to harbor strains of ESBL producers. The acquisition of ESBL in relation to age, sex, inhabitancy, inpatients, and outpatients was also analyzed. In our study, 50.29% of inpatients and 45.86% of outpatients were found to harbor ESBL producers. The difference between the two groups was not statistically significant. We found five meropenem-resistant ESBL-producing strains among the 146 ESBL producers. Rural inhabitants were found to contain more ESBLs when compared to peri-urban inhabitants. The study showed a high frequency of ESBLs in both community-acquired and hospital-acquired infections. The frequency of ESBLs was higher among isolates from patients who were from rural populations than those from peri-urban populations. The data on ESBL frequency suggests the need for a rational antibiotic use which would reduce the spread of ESBL-producing members of the family Enterobacteriaceae.

Carbapenem resistance and phenotypic detection of carbapenemases in clinical isolates of acinetobacter baumannii

Multidrug-resistant Acinetobacter baumannii (MDR-Ab) reported worldwide has become one of the most difficult nosocomially acquired Gram-negative pathogens to control and treat. The clinical utility of carbapenems is under threat with the emergence of acquired carbapenemases, particularly Ambler class B metallo-lactamases (MBL). Because of the global increase in the occurrence and dissemination of MBLs, early detection is critical. This study was undertaken to detect resistance to carbapenems in clinical isolates of A. baumannii from hospitalized patients by both disk-diffusion and minimum inhibitory concentration (MIC) methods and to assess the rate of carbapenemase and MBL production among the isolates. A. baumannii were identified from various clinical samples and antibiotic susceptibility profile was determined by the standard disk-diffusion method. Meropenem-resistant strains were tested further by agar dilution MIC for meropenem. Resistant isolates were screened for carbapenemase production by the modified Hodge test and positive isolates were further checked for metallo-β-lacatmase production by the EDTA disk synergy test. 42 isolates (31.81%) showed resistance to meropenem by the disk diffusion method. 47.6% were carbapenemase positive by the modified Hodge test and 19% were MBL producers phenotypically by the EDTA disc synergy test (EDS). These meropenem-resistant isolates were resistant to most of the other antibiotics tested. These 42 isolates were recovered mostly from patients admitted to intensive care units. Four isolates of the A. baumannii complex were pan drug resistant and showed resistance to even tigecycline and polymyxin B. Carbapenem resistance has been increasingly reported, necessitating their detection. This study reports simple, carbapenemase, and MBL detection method that can be easily incorporated into the daily routine of a clinical laboratory.

Mucoid Pseudomonads in Patients With Noncystic Fibrosis Bronchiectasis

To the Editor: Mucoid Pseudomonas aeruginosa is isolated in up to 40% of noncystic fibrosis patients with chronic bronchitis and other obstructive lung diseases.1 Apart from P. aeruginosa, mucoid strains of other species of pseudomonads are infrequently discussed; and in most of the laboratories that lack automated systems, their identification is not attempted and is reported as "Pseudomonas species not aeruginosa." Mucoid pseudomonads are lung colonizers in patients with bronchiectasis and frequently cause secondary infections leading to increased mortality and morbidity.2 In this study, we have characterized and determined the antimicrobial susceptibility of mucoid pseudomonads strains, isolated from sputum of adult patients with noncystic fibrosis bronchiectasis using simple biochemical tests, which are routinely available in a microbiology laboratory. Antimicrobial susceptibility testing and metallo-β-lactamase production were done using standard methods.3 A total of 97 strains were isolated from 871 sputum samples during the study period. Among them, P. aeruginosa (n = 49, 50.5%) was the commonest isolate, followed by Pseudomonas fluorescens (n = 15), Pseudomonas putida (n = 8), Pseudomonas pseudoalcaligenes (n = 5), Brevundimonas vesicularis (n = 5), CDC group Vb-3 (n = 4), Pseudomonas spp group 1(n = 3), Pseudomonas mendocina (n = 2), Burkholderia cepacia complex (n = 2), Ralstonia pickettii (n = 2), Pseudomonas luteola (n = 1), and Brevundimonas diminuta (n = 1). Antimicrobial susceptibility pattern showed that majority of isolates were multidrug resistant, and polymyxin B was found to be most effective antibiotic. Metallo-β-lactamase production was determined in 19 meropenem resistant strains, and 12 (63%) of 19 isolates were metallo-β-lactamase positive (Table 1).TABLE 1: Antimicrobial Susceptibility Pattern of the Common Mucoid Pseudomonads IsolatesAmong pseudomonads, P. aeruginosa is the most common human pathogen. The first report of mucoid P. aeruginosa isolation came in 1927 from a patient with a fistulating abscess of the gallbladder.2 In the first detailed study, Elston and Hoffman4 reported an incidence of mucoid forms as 1.7%, and Fujita et al5 were the first worker to report mucoid P. putida causing pulmonary infection in an immunocompetent host. Generally, "Pseudomonas non-aeruginosa" species are considered as environment contaminant; however, results of this study indicate that Pseudomonas non-aeruginosa constituted 49.5% of mucoid pseudomonal isolates in patients with bronchiectasis and are an emerging cause of respiratory infections in patients with bronchiectasis. Antimicrobial resistance among them is of increasing concern as not only P. aeruginosa but also other pseudomonads were also found to be multidrug resistant, and these probably demonstrate the changing pattern of antimicrobial resistance in pseudomonads. Further large-scale studies are required to look for epidemiological distribution of mucoid strains and study their antimicrobial susceptibility pattern. Atul Garg, MD, DNB S. Sujatha, MD Jaya Garg, MD, DNB Nasreen H., MSc S. C. Parija, MD, FRCPath Department of Microbiology Jawaharlal Institute of Postgraduate Medical Education and Research Pondicherry, India [email protected]

Novel genetic environment of the plasmid-mediated KPC-3 gene detected in Escherichia coli and Citrobacter freundii isolates from China

The imipenem and meropenem-resistant strains Citrobacter freundii HS70 and Escherichia coli HS510 were isolated from patients in Shanghai, China. By isoelectric focusing, PCR amplification and sequencing, these strains were each found to produce four β-lactamases: TEM-1, KPC-3, SHV-7 and CTX-M-14. A conjugation experiment and plasmid restriction digestion revealed that the bla KPC-3 gene was located on the same plasmid in both isolates. Bidirectional primer walking sequencing showed that the nucleotide sequence surrounding the 3.8 kb bla KPC-3 contained a 671-bp insertion similar to that previously characterized in China. The insertion was located between the promoter and the coding region of the bla KPC-3 gene. Susceptibility testing performed on recombinant strains carrying the bla KPC-3 gene with or without the insertion revealed that minimum inhibitory concentrations of imipenem, meropenem, cefepime, and cefotaxime for E. coli EMU-KPC3 (without insertion) were four times higher than that of E. coli EKPC3 (with insertion). The 671 bp insertion reduced bla KPC-3 expression significantly. Taken together, these results suggest that KPC-3-producing C. freundii and E. coli have begun to emerge in our hospital.

Combined effects of meropenem and aminoglycosides on Pseudomonas aeruginosa in vitro.

To investigate combinations of antibiotics against Pseudomonas aeruginosa, the in vitro effects of combinations of meropenem with each of three aminoglycosides, arbekacin, amikacin and netilmicin, were evaluated using an agar dilution chequerboard technique. The combinations of meropenem and aminoglycosides were effective against almost all P. aeruginosa strains tested, which included meropenem-resistant strains. Increased synergic effects were observed in combinations that included arbekacin or amikacin. None of the combinations had an antagonistic effect. Most of the synergic and additive effects were achieved at clinically relevant concentrations.

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.