Multiple-locus variable number of tandem repeats (VNTR) fingerprinting (MLVF) and antibacterial resistance profiles of extended spectrum beta lactamase (ESBL) producing Pseudomonas aeruginosa among burnt patients in Tehran

Phenotypic and genotypic identification of class C and D β-lactamases in clinical isolates of Pseudomonas aeruginosa: a cross-sectional study

Background and Aims

The emergence of Pseudomonas aeruginosa (P. aeruginosa) antibiotic resistance is an important public health problem worldwide that can negatively affect infection control. Therefore, obtaining knowledge about antibiotic resistance mechanisms is necessary for infection control policies. This study aimed to determine the frequency of class C and D β-lactamases in P. aeruginosa strains isolated from patients referred to Ardabil hospitals using phenotypic and genotypic tests.

Methods

Phenotypic detection of β-lactamases including AmpC cephalosporinase, oxacillinase (OXA)-type extended-spectrum β-lactamases (ESBLs), and OXA-type carbapenemases were performed using the disk diffusion-based methods. Amplification of genes encoding classes C (ampC and FOX genes) and D (OXA-1, OXA-2, OXA-10, OXA-23, and OXA-48 genes) β-lactamases was performed using the polymerase chain reaction (PCR) method. A quantitative reverse transcription PCR (qRT-PCR) method was used to determine the expression level of the ampC gene among multiple drug-resistant and imipenem-resistant P. aeruginosa strains.

Results

In phenotypic tests, the prevalence of AmpC cephalosporinase, OXA-type ESBLs, and OXA-type carbapenemases were 52.5%, 7.2%, and 95.8%, respectively. In genotypic tests, the prevalence of ampC, FOX, OXA-1, OXA-2, OXA-10, OXA-23, and OXA-48 genes were 100%, 0%, 4.3%, 60.8%, 42%, 29.7%, and 2.9%, respectively. In addition, the ampC gene overexpression was seen in 16 (33.3%) drug-resistant P. aeruginosa clinical isolates.

Conclusion

Given the presence of class C and D β-lactamases in clinical isolates of P. aeruginosa in Ardabil hospitals, early detection of these strains can help prevent the spread of resistant strains in hospital environments and subsequent treatment failure.

T3SS and alginate biosynthesis of Pseudomonas aeruginosa impair healing of infected rabbit wounds

Pseudomonas aeruginosa (a Gram-negative bacterium) is an opportunistic pathogen found in many infected wounds and is known to impair healing. To test the hypothesis that knocking out P. aeruginosa genes that are overexpressed during wound infection can cripple a pathogen's ability to impair healing, we assessed two pathways: the Type III secretion system (T3SS) and alginate biosynthesis. We generated single- and double-mutant strains of ExsA (T3SS activator), AlgD (GDP- mannose 6-dehydrogenase of alginate biosynthesis) and their complemented strains and evaluated their pathogenicity in a rabbit ear full-thickness excision-wound infection model. Wounds were inoculated with different strains (wild type, mutants, and complementary strains) at 10⁶ CFU/wound on post-wounding day 3. After 24 h, 5 days and 9 days post-infection, wounds were harvested for measuring bacterial counts (viable and total) and wound healing (epithelial gap). On day 9 post-infection, the viable counts of the double mutant, (exsA/algD)‾ were 100-fold lower than the counts of the wild type (PAO1), single mutants, or the complement double-mutant, (exsA/algD)‾^/+. Also, when compared to wounds infected with wild type or control strains, wounds infected with the double-knockout mutant was less inhibitory to wound healing (p < 0.05). Additionally, the double mutant showed greater susceptibility to macrophage phagocytosis in vitro than all other strains (p < 0.001). In conclusion, compared to single gene knockouts, double knockout of virulence genes in T3SS pathway and alginate biosynthesis pathway is more effective in reducing P. aeruginosa pathogenicity and its ability to impair wound healing. This study highlights the necessity of a dual-targeted anti-virulence strategy to improve healing outcomes of P. aeruginosa-infected wounds.

Preparation and Evaluation of the ZnO NP-Ampicillin/Sulbactam Nanoantibiotic: Optimization of Formulation Variables Using RSM Coupled GA Method and Antibacterial Activities

Nanoparticles (NPs) possessing antibacterial activity represent an effective way of overcoming bacterial resistance. In the present work, we report a novel formulation of a nanoantibiotic formed using Ampicillin/sulbactam (Ams) and a zinc oxide nanoparticle (ZnO NP). 'ZnO NP-Ams' nanoantibiotic formulation is optimized using response surface methodology coupled genetic algorithm approach. The optimized formulation of nanoantibiotic (ZnO NP: 49.9 μg/mL; Ams: 33.6 μg/mL; incubation time: 27 h) demonstrated 15% enhanced activity compared to the unoptimized formulation against K. pneumoniae. The reactive oxygen species (ROS) generation was directly proportional to the interaction time of nanoantibiotic and K. pneumoniae after the initial lag phase of ~18 h as evident from 2'-7'-Dichlorodihydrofluorescein diacetate assay. A low minimum inhibitory concentration (6.25 μg/mL) of nanoantibiotic formulation reveals that even a low concentration of nanoantibiotic can prove to be effective against K. pneumoniae. The importance of nanoantibiotic formulation is also evident by the fact that the 100 μg/mL of Ams and 25 µg of ZnO NP was required individually to inhibit the growth of K. pneumonia, whereas only 6.25 μg/mL of optimized nanoantibiotic formulation (ZnO NP and Ams in the ratio of 49.9: 33.6 in μg/mL and conjugation time of 27 h) was needed for the same.

Hospital Drains as Reservoirs of Pseudomonas aeruginosa: Multiple-Locus Variable-Number of Tandem Repeats Analysis Genotypes Recovered from Faucets, Sink Surfaces and Patients

Identifying environmental sources of Pseudomonas aeruginosa (Pa) related to hospital-acquired infections represents a key challenge for public health. Biofilms in water systems offer protection and favorable growth conditions, and are prime reservoirs of microorganisms. A comparative genotyping survey assessing the relationship between Pa strains recovered in hospital sink biofilm and isolated in clinical specimens was conducted. Environmental strains from drain, faucet and sink-surface biofilm were recovered by a culture method after an incubation time ranging from 48 to 240 h. The genotyping of 38 environmental and 32 clinical isolates was performed using a multiple-locus variable-number of tandem repeats analysis (MLVA). More than one-third of Pa isolates were only cultivable following ≥48 h of incubation, and were predominantly from faucet and sink-surface biofilms. In total, 41/70 strains were grouped within eight genotypes (A to H). Genotype B grouped a clinical and an environmental strain isolated in the same ward, 5 months apart, suggesting this genotype could thrive in both contexts. Genotype E grouped environmental isolates that were highly prevalent throughout the hospital and that required a longer incubation time. The results from the multi-hospital follow-up study support the drain as an important reservoir of Pa dissemination to faucets, sink surfaces and patients. Optimizing the recovery of environmental strains will strengthen epidemiological investigations, facilitate pathway identification, and assist in identifying and controlling the reservoirs potentially associated to hospital-acquired infections.

Systematic review and meta-analysis of imipenem-resistant Pseudomonas aeruginosa prevalence in Iran

INTRODUCTION

Imipenem-resistant Pseudomonas aeruginosa (IRPA), due to resistance to different classes of antibiotics and its remarkable capacity to survive in harsh and adverse conditions such as those in the hospital environment, is considered a serious threat to the healthcare system. Given the great impact of IRPA on patients' outcome and in order to possibly improve antibiotic prescription, this study was conducted to determine the prevalence of clinical isolates of IRPA in different parts of Iran.

METHODS

A systematic literature search was performed in PubMed, Web of Science, Google Scholar and Scopus, as well as in two Iranian domestic search engines, i.e., Iranian Scientific Information Database and Magiran. Finally, after applying exclusion and inclusion criteria 37 articles with full-texts describing the prevalence of imipenem-resistant P. aeruginosa were selected for meta-analysis and systematic review.

RESULTS

The pooled estimation of 5227 P. aeruginosa isolates in this analysis showed that the percentage of imipenem-resistant P. aeruginosa is about 54% in the Iranian population (95%CI: 0.47-0.62, logit event rate=0.19, 95%CI: -0.12,0.49).

CONCLUSION

The findings of this analysis show that in the majority of Iranian hospitals the relative frequency of IRPA is high, therefore, in order to prevent further dissemination of IRPA, more appropriate antibiotic prescription and infection control policies must be implemented by decision-makers.

MLVF analysis of anginosus (milleri) group streptococci

We developed a new method of typing for anginosus group streptococci (SAG). It is the first SAG-dedicated, PCR-based method, which allows to determine the relationship between strains. The method is based on the detection of tandem repeats among 9 genomic loci and is classified as multilocus variable number tandem repeats fingerprint (MLVF) type of analysis. Using the described method, it is possible to detect over half million MLVF patterns, which correlate with pulsed-field gel electrophoresis profiles. The other advantage of the method is relatively short time from "cell to data", low costs, and easy application for epidemiological and evolutionary studies.

Genetic characterization of Pseudomonas aeruginosa-resistant isolates at the university teaching hospital in Iran

Background:

Pseudomonas aeruginosa is an opportunistic pathogen that is commonly responsible for nosocomial infections. The aim of this study was to perform a genotyping analysis of the Pseudomonas aeruginosa-resistant isolates by the multilocus sequence typing (MLST) method at the university teaching hospital in Iran.

Materials and Methods:

Antimicrobial susceptibility was analyzed for P. aeruginosa isolates. Ceftazidime-resistant (CAZ_res) isolates with a positive double-disc synergy test were screened for the presence of extended-spectrum β-lactamase-encoding genes. Phenotypic tests to detect the metallo-β-lactamase strains of P. aeruginosa were performed on imipenem-resistant (IMP_res) isolates. Selected strains were characterized by MLST.

Results:

Of 35 P. aeruginosa isolates, 71%, 45% and 45% of isolates were CAZ_res, IMP_res and multidrug resistant (MDR), respectively. Fifty-seven percent of the isolates carried the bla_OXAgroup-1. All the five typed isolates were ST235. Isolates of ST235 that were MDR showed a unique resistance pattern.

Conclusion:

This study shows a high rate of MDR P. aeruginosa isolates at the university teaching hospital in Iran. It seems MDR isolates of P. aeruginosa ST235 with unique resistance pattern disseminated in this hospital.

Prevalence of Extended-Spectrum and Metallo β-Lactamase Production in AmpC β-Lactamase Producing Pseudomonas aeruginosa Isolates From Burns

BACKGROUND

Pseudomonas aeruginosa is one of the most common causes of nosocomial infections. Resistance of P. aeruginosa to β-lactam antibiotics may be the result of acquired resistance through mutation and over production of various antibiotic inactivating enzymes. This research aimed to determine the prevalence of extended-spectrum β-lactamases (ESBL) and metallo β-lactamase (MBL) production as well as the presence of their related genes among AmpC β-lactamase producing P. aeruginosa isolated from burns.

OBJECTIVES

The current study aimed to determine the prevalence of class A ESBL and MBL production in relation to the presence of their related genes among AmpC β-lactamase producing P. aeruginosa isolated from burns.

MATERIALS AND METHODS

The antimicrobial susceptibility of 51 P. aeruginosa isolates from patients with burns was examined against 13 antibiotics by the disc diffusion method. Minimum inhibitory concentrations (MIC) for imipenem and ceftazidime were measured by the microdilution method. AmpC production was detected by AmpC disc and the modified three-dimensional extract tests. ESBL phenotype was confirmed by the double disc synergy test (DDST). Presence of β-lactamase genes was detected by specific primers and polymerase chain reaction (PCR).

RESULTS

All isolates were multidrug resistant. AmpC, ESBL and MBL production were observed in 35 (68.6%), 20 (39.2%) and 19 (37.3%) isolates, respectively. Overall, 43 isolates (84.3%) carried β-lactamase genes, out of which 31 (60.8%) harbored bla AmpC , 20 (39.2%) had bla TEM and 11 (21.6%) carried bla PER -1 genes. Among the AmpC producers, two isolates (6.5%) carried bla AmpC + bla ESBL , 13 (41.9%) had bla AmpC + bla MBL and six (19.4%) produced the three enzymes.

CONCLUSIONS

A high prevalence of multiple β-lactamase production was observed among the AmpC producers (60%), of which the majority co-produced AmpC and MBL. The current study results showed correlation between β-lactamase production and the presence of antibiotic resistance genes in the isolates.

Antimicrobial resistance pattern and their beta-lactamase encoding genes among Pseudomonas aeruginosa strains isolated from cancer patients

This study was designed to investigate the prevalence of metallo-β-lactamases (MBL) and extended-spectrum β -lactamases (ESBL) in P. aeruginosa isolates collected from two different hospitals in Cairo, Egypt. Antibiotic susceptibility testing and phenotypic screening for ESBLs and MBLs were performed on 122 P. aeruginosa isolates collected in the period from January 2011 to March 2012. MICs were determined. ESBLs and MBLs genes were sought by PCR. The resistant rate to imipenem was 39.34%. The resistance rates for P. aeruginosa to cefuroxime, cefoperazone, ceftazidime, aztreonam, and piperacillin/tazobactam were 87.7%, 80.3%, 60.6%, 45.1%, and 25.4%, respectively. Out of 122 P. aeruginosa, 27% and 7.4% were MBL and ESBL, respectively. The prevalence of bla(VIM-2), bla(OXA-10(-)), bla(VEB-1), bla(NDM(-)), and bla(IMP-1)-like genes were found in 58.3%, 41.7%, 10.4%, 4.2%, and 2.1%, respectively. GIM-, SPM-, SIM-, and OXA-2-like genes were not detected in this study. OXA-10-like gene was concomitant with VIM-2 and/or VEB. Twelve isolates harbored both OXA-10 and VIM-2; two isolates carried both OXA-10 and VEB. Only one strain contained OXA-10, VIM-2, and VEB. In conclusion, bla(VIM-2)- and bla(OXA-10)-like genes were the most prevalent genes in P. aeruginosa in Egypt. To our knowledge, this is the first report of bla(VIM-2), bla(IMP-1), bla(NDM), and bla(OXA-10) in P. aeruginosa in Egypt.

Antimicrobial resistance pattern and their beta-lactamase encoding genes among Pseudomonas aeruginosa strains isolated from cancer patients

This study was designed to investigate the prevalence of metallo-β-lactamases (MBL) and extended-spectrum β -lactamases (ESBL) in P. aeruginosa isolates collected from two different hospitals in Cairo, Egypt. Antibiotic susceptibility testing and phenotypic screening for ESBLs and MBLs were performed on 122 P. aeruginosa isolates collected in the period from January 2011 to March 2012. MICs were determined. ESBLs and MBLs genes were sought by PCR. The resistant rate to imipenem was 39.34%. The resistance rates for P. aeruginosa to cefuroxime, cefoperazone, ceftazidime, aztreonam, and piperacillin/tazobactam were 87.7%, 80.3%, 60.6%, 45.1%, and 25.4%, respectively. Out of 122 P. aeruginosa, 27% and 7.4% were MBL and ESBL, respectively. The prevalence of bla(VIM-2), bla(OXA-10(-)), bla(VEB-1), bla(NDM(-)), and bla(IMP-1)-like genes were found in 58.3%, 41.7%, 10.4%, 4.2%, and 2.1%, respectively. GIM-, SPM-, SIM-, and OXA-2-like genes were not detected in this study. OXA-10-like gene was concomitant with VIM-2 and/or VEB. Twelve isolates harbored both OXA-10 and VIM-2; two isolates carried both OXA-10 and VEB. Only one strain contained OXA-10, VIM-2, and VEB. In conclusion, bla(VIM-2)- and bla(OXA-10)-like genes were the most prevalent genes in P. aeruginosa in Egypt. To our knowledge, this is the first report of bla(VIM-2), bla(IMP-1), bla(NDM), and bla(OXA-10) in P. aeruginosa in Egypt.

Evaluation of biofilm production and characterization of genes encoding type III secretion system among Pseudomonas aeruginosa isolated from burn patients

Pseudomonas aeruginosa is one of the common pathogenic causes of serious infections in burn patients throughout the world. Type III secretion toxins are thought to promote the dissemination of P. aeruginosa from the site of infection, the bacterial evasion of the host immune response and inhibition of DNA synthesis leading to host cell death. A total of 96 isolates of P. aeruginosa were collected from wound infections of burn patients, from April to July 2010. Antimicrobial susceptibility of the isolates were determined by disk agar diffusion method. Polymerase chain reaction (PCR)-based method was used for targeting the genes encoding the type III secretion toxins. The quantitative determination of biofilm-forming capacity was determined by a colorimetric microtiter plate assay. All the isolates were resistant to cefixime and ceftriaxone. More than 90% of the isolates were resistant to amikacin, carbenicillin, cefepime, cefotaxime, cefpodoxime, gatifloxacin, gentamicin, piperacillin/tazobactam, ticarcillin and tobramycin. All the isolates carried the exoT gene, 95% carried exoY, 64.5% carried exoU and 29% carried the exoS gene. Most of the isolates (58%) carried both exoY and exoU genes while 24% showed the concomitant presence of exoS and exoY and 1% carried both exoS and exoU. Coexistence of exoS, exoY and exoU was seen in 4% of the isolates. Biofilm formation was seen in more than 96% of the isolates among which 47% were strong biofilm producers, 26% were moderate and 22.9% were weak biofilm formers. In conclusion, the findings of this study show that the genes, particularly the exoU gene, encoding the type III secretion toxins, are commonly disseminated among the P. aeruginosa strains isolated from burn patients.