High prevalence of metallo-beta-lactamase-mediated resistance challenging antimicrobial therapy against Pseudomonas aeruginosa in a Brazilian teaching hospital

Evaluation of phenotypic detection of carbapenemase-producing Pseudomonas spp. from clinical isolates

Carbapenems are considered last-resort antibiotics for the treatment of infections caused by multidrug-resistant Gram-negative bacteria. Although the main mechanism of carbapenem-resistance in Pseudomonas aeruginosa is the loss of OprD porin, carbapenemases continue to be a problem worldwide. The aim of this study was to evaluate the performance of phenotypic tests (Carba NP, Blue Carba, and mCIM/eCIM) for detection of carbapenemase-producing Pseudomonas spp. in Brazil. One hundred twenty-seven Pseudomonas spp. clinical isolates from different Brazilian states were submitted to phenotypic and molecular carbapenemase detection. A total of 90 carbapenemase-producing P. aeruginosa and 5 Pseudomonas putida (35, blaVIM-2; 17, blaSPM-1; 2, blaIMP-10; 1, blaVIM-24; 1, blaNDM-1; 39, blaKPC-2). The phenotypic Carba NP, Blue Carba, and mCIM/eCIM showed sensitivity of 94.7%, 93.6%, and 93.6%, and specificity of 90.6%, 100%, and 96.8%, respectively. However, only the Carba NP presented the highest sensitivity and showed the ability in differentiating the carbapenemases between class A and class B using EDTA. Blue Carba failed to detect most of the class B carbapenemases, having the worst performance using EDTA. Our results show changes in the epidemiology of the spread of carbapenemases and the importance of their detection by phenotypic and genotypic tests. Such, it is essential to use analytical tools that faithfully detect bacterial resistance in vitro in a simple, sensitive, rapid, and cost-effective way. Much effort must be done to improve the current tests and for the development of new ones.

Detection of Metallo Beta-Lactamase (MBL) Producing Pseudomonas aeruginosa in a Tertiary Care Hospital, Ghanpur, Medchal, India

Introduction:Pseudomonas aeruginosa is a leading cause of nosocomial infections and is especially prevalent among patients with burn wounds, cystic fibrosis, acute leukemia, organ transplants and intravenous-drug addiction. Acquired metallo-â-lactamases (MBLs) are carbapenemases which require zinc in the active site and are predominantly produced by P. aeruginosa. They belong to Ambler's class B and Bush-Jacoby Medeiros Group 3 and hydrolyse virtually all â-lactam agents, including the carbapenems. In India, only blaVIM and NDM-1 have been reported in P. aeruginosa. Metallo beta-lactamases have recently emerged as one of the most worrisome resistance mechanisms owing to their capacity to hydrolyse all beta-lactams, including carbapenems. Aims and objectives: The present study aimed to investigate the prevalence and resistance patterns of MBL-producing P. aeruginosa in a tertiary care hospital of Ghanpur, Medchal, India, and to compare the effectiveness of two different methods of screening and detecting MBL-producing P. aeruginosa in order to formulate a policy of empirical therapy and to take preventive measures in hospital settings. Methodology: In the present study, 60 isolates of Pseudomonas aeruginosa were obtained from various clinical specimens, including pus, urine, burns, wound, sputum, pleural fluid, and CSF, which were taken from inpatients and outpatients admitted to MIMS, Ghanpur, India. The study period was from January 2017 to July 2018. The microbial isolates were studied for the detection of the prevalence of MBL production, including their antibiogram. Results:Of the 60 Pseudomonas aeruginosa isolates, 12 were Imipenem resistant, of which nine were MBL producers. Most isolates (14) were collected in the age group of 21-30 years, followed by that of 31-40 years (13) and 1-10 years (2). Of the total number of samples, 40 strains were isolated in male subjects, with a male-female ratio of 2:1. Total wound swabs accounted for 40% of the studied specimens, followed by ear swabs (20%) and sputum samples (18.3%). Wound swabs also included most Imipenem-resistant isolates (41.6%). Metallo beta-lactamase producers accounted for 75% of all carbapenem-resistant isolates, using the combined disc method and E-test. By comparison, DDST retrieved 41% of Pseudomonas MBL producers. Isolates were 100% sensitive to Polymyxin-B and showed a 44.4% sensitivity to Piperacillin/Tazobactam, followed by 22.2% for Amikacin and Tobramycin and 11.1% for Ciprofloxacin and Gentamicin. Conclusion:The study found a relatively high prevalence of Pseudomonas MBL producers (9/60) with 100% Polymyxin susceptibility. Hence, our results warn against an expected high use of Polymyxins in clinical settings. Additionally, the study supports the use of E-tests, CDST and DDST for the screening of Pseudomonas MBL producers in regions where PCR detection cannot be performed.

Prevalence and Phenotypic and Genotypic Resistance Mechanisms of Multidrug-Resistant Pseudomonas aeruginosa Strains Isolated from Clinical, Environmental, and Poultry Litter Samples from the Ashanti Region of Ghana

Background

Antibiotic resistance in bacteria is a major global health challenge. Reports on the prevalence of multidrug-resistant P. aeruginosa, a common pathogenic bacterium implicated in nosocomial infections and poultry diseases, are limited in Ghana. This study therefore sought to determine the prevalence of P. aeruginosa from hospitals, poultry farms, and environmental samples from the Ashanti region of Ghana. Methodology. Stool, urine, and blood samples from 364 patients from two hospitals in the Ashanti region of Ghana were randomly sampled. P. aeruginosa was isolated and confirmed using routine selective media and PCR-based oprL gene amplification. The Kirby-Bauer disk diffusion method employing EUCAST breakpoint values was used to identify multidrug-resistant strains. The occurrence of common antibiotic inactivating enzymes and resistance encoding genes and the assessment of strain efflux capacity were investigated with double disc synergy test (DDST), imipenem-EDTA synergy test, phenylboronic acid test, D-test, routine PCR, and ethidium bromide agar-cartwheel method.

Results

A total of 87 (9.7%, n = 87/900) P. aeruginosa isolates were confirmed from the samples. 75% (n = 65/87) were resistant to more than one group of antipseudomonal agents, while 43.6% (n = 38/87) were multidrug-resistant (MDR). High prevalence of extended spectrum β-lactamases (84.2%), metallo-β-lactamases (34.1%), and AmpC inducible cephalosporinases (50%) was observed in the MDR strains. About 57.8% of the MDR strains showed moderate to very high efflux capacity. Class 1 integrons were detected in 89.4% of the MDR isolates but β-lactamase encoding genes (bla SHV , bla TEM , bla CTX-M , bla VIM , and bla IMP ) were not detected.

Conclusion

Surveillance of antibiotic-resistant strains of bacteria should be routinely conducted in clinical and veterinary practice in Ghana to inform selection of antibiotics for therapeutic use.

Antibacterial effect of silver nanoparticles in Pseudomonas aeruginosa

Pseudomonas aeruginosa has great intrinsic antimicrobial resistance limiting the number of effective antibiotics. Thus, other antimicrobial agents such as silver nanoparticles (AgNPs) are considered potential agents to help manage and prevent infections. AgNPs can be used in several applications against bacteria resistant to common antibiotics or even multi-resistant bacteria such as P. aeruginosa. This study assessed the antimicrobial activity of commercial 10 nm AgNPs on two hospital strains of P. aeruginosa resistant to a large number of antibiotics and a reference strain from a culture collection. All strains were susceptible to 5 µg/mL nanoparticles solution. Reference strains INCQS 0230 and P.a.1 were sensitive to AgNPs at concentrations of 1.25 and 0.156 µg/mL, respectively; however, this was not observed for hospital strain P.a.2, which was more resistant to all antibiotics and AgNPs tested. Cytotoxicity evaluation indicated that AgNPs, up to a concentration of 2.5 µg/mL, are very safe for all cell lines tested. At 5.0 µg/mL, AgNPs had a discrete cytotoxic effect on tumor cells HeLa and HepG2. Results showed the potential of using AgNPs as an alternative to conventional antimicrobial agents that are currently used, and a perspective for application of nanosilver with antibiotics to enhance antimicrobial activity.

The epidemiology of carbapenemases in Latin America and the Caribbean

INTRODUCTION

Enterobacteriaceae, Pseudomonas spp., and Acinetobacter spp. infections are major causes of morbidity and mortality, especially due to the emergence and spread of β-lactamases. Carbapenemases, which are β-lactamases with the capacity to hydrolyze or inactivate carbapenems, have become a serious concern as they have the largest hydrolytic spectrum and therefore limit the utility of most β-lactam antibiotics. Areas covered: Here, we present an update of the current status of carbapenemases in Latin America and the Caribbean. Expert commentary: The increased frequency of reports on carbapenemases in Latin America and the Caribbean shows that they have successfully spread and have even become endemic in some countries. Countries such as Brazil, Colombia, Argentina, and Mexico account for the majority of these reports. Early suspicion and detection along with implementation of antimicrobial stewardship programs in all healthcare settings are crucial for the control and prevention of carbapenemase-producing bacteria.

Carbapenem resistance in Pseudomonas aeruginosa and Acinetobacter baumannii in the nosocomial setting in Latin America

Increasing prevalence of carbapenem-resistant Pseudomonas aeruginosa and Acinetobacter baumannii strains in the nosocomial setting in Latin America represents an emerging challenge to public health, as the range of therapeutic agents active against these pathogens becomes increasingly constrained. We review published reports from 2002 to 2013, compiling data from throughout the region on prevalence, mechanisms of resistance and molecular epidemiology of carbapenem-resistant strains of P. aeruginosa and A. baumannii. We find rates of carbapenem resistance up to 66% for P. aeruginosa and as high as 90% for A. baumannii isolates across the different countries of Latin America, with the resistance rate of A. baumannii isolates greater than 50% in many countries. An outbreak of the SPM-1 carbapenemase is a chief cause of resistance in P. aeruginosa strains in Brazil. Elsewhere in Latin America, members of the VIM family are the most important carbapenemases among P. aeruginosa strains. Carbapenem resistance in A. baumannii in Latin America is predominantly due to the oxacillinases OXA-23, OXA-58 and (in Brazil) OXA-143. Susceptibility of P. aeruginosa and A. baumannii to colistin remains high, however, development of resistance has already been detected in some countries. Better epidemiological data are needed to design effective infection control interventions.