Carbapenem-resistant Pseudomonas aeruginosa: association with virulence genes and biofilm formation

Identification of bla OXA-23 gene in resistant Pseudomonas aeruginosa strains isolated from cows and humans in Basra province, Iraq

Background and Aim

Pseudomonas aeruginosa is an infectious agent of great importance for animals and humans. It causes serious infections that show high resistance to antibiotics. This study investigated the molecular detection of blaOXA-23 gene in antibiotic-resistant P. aeruginosa strains isolated from cows and humans.

Materials and Methods

In total, 120 samples, comprised 60 from cows (30 milk and 30 nasal discharge) and 60 from their owners (30 urine and 30 sputum), were individually collected, cultured, and tested for P. aeruginosa through molecular analysis targeting the blaOXA-23 gene. P. aeruginosa antibiotic-resistant isolates were identified by performing antibiotic susceptibility testing and detecting biofilm formation.

Results

In total, 74.17% positive P. aeruginosa isolates, including 66.67% and 81.67% for cows and humans, respectively. Subsequently, positive cow isolates were detected in 60% of milk samples and 73.33% of nasal discharge samples; while positive human isolates were detected in 76.67% of urine samples and 86.66% of sputum samples. Targeting blaOXA-23 gene, 58.43% of cultured isolates were positive for P. aeruginosa by polymerase chain reaction. Respectively, positive isolates were detected in 66.67% and 45.46% of cow milk and nasal discharges as well as in 60.87% and 61.54% of human urine and sputum. The antibiotic susceptibility test revealed that all isolates were resistant to all applied antibiotics, particularly imipenem. Results of biofilm formation revealed 67.31% total positives, including 51.43% strong, 34.285% moderate, and 14.285% weak reactions. In addition, although values of the total positive cows and humans differed insignificantly, total positives showed insignificant variation between values of milk and nasal discharges of cows as well as between urine and sputum of humans; however, significant differences were identified in the distribution of strong, moderate, and weak positivity of these samples.

Conclusion

Antibiotic overuse contributes extensively to increasing the prevalence of resistant P. aeruginosa isolates carrying the blaOXA-23 gene in both cows and humans. Furthermore, studies in other Iraqi areas are necessary to support our findings. The main limitations include that the number of tested samples is relatively low, and there is a need to use a large number of samples from different sources. Also, the current methods for detection of resistant isolates are still culture-based approaches.

Application of coliphage as biocontrol agent in combination with gamma irradiation to eliminate multi-drug-resistant E. coli in minimally processed vegetables

Biofilm formation is a rising concern in the food industry. Escherichia coli (E. coli) is one of the most important food-borne pathogens that can survive in food and food-related environments and eventually produce biofilms. This study suggested that both coliphages used were successful in preventing the creation of new biofilms as well as removing existing ones. Confocal laser scanning microscopy verified these findings. According to the findings, neither coliphage survived at 37 °C, but both remained stable at 4 °C and - 20 °C for extended periods of time. The study revealed that both coliphages demonstrated a greater degree of gamma irradiation resistance when compared to E. coli. The study's results indicate that the implementation of a dual method, which incorporates gamma irradiation (1.5 kGy) and coliphage treatment, on various kinds of vegetables that were infected with E. coli, resulted in a significant reduction in bacterial count (surpassing 99.99%) following a 24-h incubation period. Combining gamma irradiation and the coliphage approach was significantly effective at lowering polysaccharide concentrations and proteins in the biofilm matrix. The results revealed that the pairing of gamma irradiation and coliphages acted in conjunction to cause disruptions in the matrix of biofilm, thereby promoting cell removal compared with either of the individual treatments. Ca+ ions strengthen the weak virion interaction with the relevant bacterial host cell receptors during the adsorption process. In conclusion, use of coliphage in combination with gamma irradiation treatment can be applied to improve fresh produce's microbial safety and enhance its storability in supermarkets.

The Prevalence of Metallo-Beta-Lactamese-(MβL)-Producing Pseudomonas aeruginosa Isolates in Brazil: A Systematic Review and Meta-Analysis

The purpose of the current study is to describe the prevalence of Pseudomonas aeruginosa (PA)-producing MβL among Brazilian isolates and the frequency of blaSPM-1 in MβL-PA-producing isolates. From January 2009 to August 2023, we carried out an investigation on this subject in the internet databases SciELO, PubMed, Science Direct, and LILACS. A total of 20 papers that met the eligibility requirements were chosen by comprehensive meta-analysis software v2.2 for data retrieval and analysis by one meta-analysis using a fixed-effects model for the two investigations. The prevalence of MβL-producing P. aeruginosa was 35.8% or 0.358 (95% CI = 0.324-0.393). The studies' differences were significantly different from one another (x2 = 243.15; p < 0.001; I2 = 92.18%), so they were divided into subgroups based on Brazilian regions. There was indication of asymmetry in the meta-analyses' publishing bias funnel plot; so, a meta-regression was conducted by the study's publication year. According to the findings of Begg's test, no discernible publishing bias was found. blaSPM-1 prevalence was estimated at 66.9% or 0.669 in MβL-PA isolates (95% CI = 0.593-0.738). The analysis of this one showed an average heterogeneity (x2 = 90.93; p < 0.001; I2 = 80.20%). According to the results of Begg's test and a funnel plot, no discernible publishing bias was found. The research showed that MβL-P. aeruginosa and SPM-1 isolates were relatively common among individuals in Brazil. P. aeruginosa and other opportunistic bacteria are spreading quickly and causing severe infections, so efforts are needed to pinpoint risk factors, reservoirs, transmission pathways, and the origin of infection.

Genotypic characterization and clonal relatedness of metallo-β-lactamase-producing non-fermentative gram negative bacteria in the first 5 years of their circulation in Paraguay (2011-2015)

Pseudomonas aeruginosa and species of Acinetobacter calcoaceticus-baumanii complex are multiresistant intrahospital opportunistic pathogens, able to acquire carbapenemases and produce outbreaks with high morbidity and mortality. Pseudomonas putida has also emerged with similar characteristics. The aim of this research was to characterize the Metallo-β-lactamases (MBLs) detected by surveillance in Paraguay in the first 5 years of their circulation in hospitals. The coexistence of KPC and OXA-type carbapenemases was also investigated. 70 MBL-producing strains from inpatients were detected from clinical samples and rectal swab from 11 hospitals. The strains were identified by manual, automated, and molecular methods. Antimicrobial susceptibility was studied by Kirby-Bauer and automated methods, while colistin susceptibility was determined by broth macrodilution. MBLs were investigated by synergy with EDTA against carbapenems and PCR, and their variants by sequencing. KPC and OXA-carbapenemases were investigated by PCR. Clonality was studied by pulsed-field gel electrophoresis (PFGE). The results demonstrated the circulation of blaVIM-2 (60%), blaNDM-1 (36%), and blaIMP-18 (4%). The MBL-producing species were P. putida (45.7%), P. aeruginosa (17.2%), A. baumannii (24.3%), A. pittii (5.7%), A. nosocomialis, (4.3%) A. haemolyticus (1.4%), and A. bereziniae (1.4%). PFGE analysis showed one dominant clone for A. baumannii, a predominant clone for half of the strains of P. aeruginosa, and a polyclonal spread for P. putida. In the first 5 years of circulation in Paraguay, MBLs were disseminated as unique variants per genotype, appeared only in Pseudomonas spp. and Acinetobacter spp., probably through horizontal transmission between species and vertical by some successful clones.

Non-invasive biomedical sensors for early detection and monitoring of bacterial biofilm growth at the point of care

Bacterial infections have long been a serious global health issue. Biofilm formation complicates matters even more. The biofilm's extracellular polymeric substances (EPSs) matrix protects bacteria from the host's immune responses, yielding strong adhesion and drug resistance as the biofilm matures. Early bacterial biofilm detection and bacterial biofilm growth monitoring are crucial to treating biofilm-associated infections. Current detection methods are highly sensitive but not portable, are time-consuming, and require expensive equipment and complex operating procedures, limiting their use at the point of care. Therefore, there is an urgent need to develop affordable, on-body, and non-invasive biomedical sensors to continuously monitor and detect early biofilm growth at the point of care through personalized telemedicine. Herein, recent advances in developing non-invasive biomedical sensors for early detection and monitoring bacterial biofilm growth are comprehensively reviewed. First, biofilm's life cycle and its impact on the human body, such as biofilm-associated disease and infected medical devices, are introduced together with the challenges of biofilm treatment. Then, the current methods used in clinical and laboratory settings for biofilm detection and their challenges are discussed. Next, the current state of non-invasive sensors for direct and indirect detection of bacterial biofilms are summarized and highlighted with the detection parameters and their design details. Finally, commercially available products, challenges of current devices, and the further trend in biofilm detection sensors are discussed.

Decoding Genetic Features and Antimicrobial Susceptibility of Pseudomonas aeruginosa Strains Isolated from Bloodstream Infections

Pseudomonas aeruginosa is a Gram-negative rod and an etiological factor of opportunistic infections. The infections of this etiology appear mostly among hospitalized patients and are relatively hard to treat due to widespread antimicrobial resistance. Many virulence factors are involved in the pathogenesis of P. aeruginosa infection, the coexistence of which have a significant impact on the course of an infection with a particular localization. The aim of this study was to assess the antimicrobial susceptibility profiles and the frequency of genes encoding selected virulence factors in clinical P. aeruginosa strains isolated from bloodstream infections (BSIs). The following genes encoding virulence factors of enzymatic activity were assessed: lasB, plC H, plC N, nan1, nan2, aprA and phzM. The frequency of the genes encoding the type III secretion system effector proteins (exoU and exoS) and the genes encoding pilin structural subunits (pilA and pilB) were also investigated. The occurrence of virulence-factor genes was assessed using polymerase chain reactions, each in a separate reaction. Seventy-one P. aeruginosa strains, isolated from blood samples of patients with confirmed bacteremia hospitalized at the University Hospital No. 1 of Dr. Antoni Jurasz in Bydgoszcz, Poland, were included in the study. All the investigated strains were susceptible to colistin, while the majority of the strains presented resistance to ticarcillin/clavulanate (71.8%), piperacillin (60.6 %), imipenem (57.7%) and piperacillin/tazobactam (52.1%). The presence of the lasB and plC H genes was noted in all the tested strains, while the plC N, nan2, aprA, phzM and nan1 genes were identified in 68 (95.8%), 66 (93.0%), 63 (88.7%), 55 (77.5%) and 34 (47.9%) isolates, respectively. In 44 (62.0%) and 41 (57.7%) strains, the presence of the exoU and exoS genes was confirmed, while the pilA and pilB genes were noted only in 14 (19.7%) and 3 (4.2%) isolates, respectively. This may be due to the diverse roles of these proteins in the development and maintenance of BSIs. Statistically significant correlations were observed between particular gene pairs’ coexistence (e.g., alkaline protease and neuraminidase 2). Altogether, twenty-seven distinctive genotypes were observed among the studied strains, indicating the vast variety of genetic compositions of P. aeruginosa strains causing BSIs.

Evidence of Virulent Multi-Drug Resistant and Biofilm-Forming Listeria Species Isolated from Various Sources in South Africa

Listeriosis is a foodborne disease caused by Listeria monocytogenes species and is known to cause severe complications, particularly in pregnant women, young children, the elderly, and immunocompromised individuals. The aim of this study was to investigate the presence of Listeria species in food and water using both biochemical and species-specific PCR analysis. L. monocytogenes isolates were further screened for the presence of various antibiotic resistance, virulence, and biofilm-forming determinants profiles using phenotypic and genotypic assays. A total of 207 samples (composed of meat, milk, vegetables, and water) were collected and analyzed for presence of L. monocytogenes using species specific PCR analysis. Out of 267 presumptive isolates, 53 (19.85%) were confirmed as the Listeria species, and these comprised 26 L. monocytogenes, 3 L. innocua, 2 L. welshimeri, and 1 L. thailandensis. The remaining 21 Listeria species were classified as uncultured Listeria, based on 16SrRNA sequence analysis results. A large proportion (76% to 100%) of the L. monocytogenes were resistant to erythromycin (76%), clindamycin (100%), gentamicin (100%), tetracycline (100%), novobiocin (100%), oxacillin (100%), nalidixic acid (100%), and kanamycin (100%). The isolates revealed various multi-drug resistant (MDR) phenotypes, with E-DA-GM-T-NO-OX-NA-K being the most predominant MDR phenotypes observed in the L. monocytogenes isolates. The virulence genes prfA, hlyA, actA, and plcB were detected in 100%, 68%, 56%, and 20% of the isolates, respectively. In addition, L. monocytogenes isolates were capable of forming strong biofilm at 4 °C (%) after 24 to 72 h incubation periods, moderate for 8% isolates at 48 h and 20% at 72 h (p < 0.05). Moreover, at 25 °C and 37 °C, small proportions of the isolates displayed moderate (8−20%) biofilm formation after 48 and 72 h incubation periods. Biofilm formation genes flaA and luxS were detected in 72% and 56% of the isolates, respectively. These findings suggest that proper hygiene measures must be enforced along the food chain to ensure food safety.

Presence of quorum sensing system, virulence genes, biofilm formation and relationship among them and class 1 integron in carbapenem-resistant clinical Pseudomonas aeruginosa isolates

Carbapenems are the most effective agents for treating clinical P. aeruginosa (PsA) infections. During an infection, a quorum-sensing (QS) system and its regulating virulence genes have a great role. The aim of the study was to detect the presence of a las and rhl QS system and related virulence genes, biofilm formation and a class 1 (Cls1) integron. A total of 52 carbapenem-resistant PsA (CRPsA) isolates obtained from Kastamonu, Turkey was analyzed. For the isolation and identification of CRPsA isolates, a conventional culture method, an automated VITEK-2 compact system, and oprL gene-based molecular technique were applied. The two QS system genes were detected in 51 (98.1%), and co-existed of four two QS system genes (lasI/R and rhIl/R genes) were determined in 41 (78.8%) of the isolates. algD, lasB, toxA and aprA genes were detected in between 46.1 and 88.5%, and co-existence of four two QS system genes with four virulence genes were detected in 40.4% of the isolates. Biofilm formation using microtiter plate assay and slime production using Congo Red Agar and Cls1 integron were determined in 84.6%, 67.3% and 51.9% of the isolates, respectively. According to statistical analyses results, there was a significant positive correlation (p < .10) between the las and the rhl systems and a strongly and positive correlation (p < .01 or p < .05) between the rhl system-three virulence genes and slime production-and among some virulence genes. In conclusion, the CRPsA isolates tested in the study are highly virulent and QS systems have a significant role in pathogenesis.

Phenotypic and Molecular Characterization of Nonfermenting Gram-Negative Bacilli Causing Peritonitis in Peritoneal Dialysis Patients

(1) Background: Peritonitis due to nonfermenting Gram-negative bacilli (NF-GNB) is a dramatic complication of peritoneal dialysis (PD) with bad outcomes. Previous studies of PD-related peritonitis due to Pseudomonas species have shown a low-resolution rate, without a high resistance rate to antipseudomonal antibiotics. This suggests that bacterial virulence factors can act and influence peritonitis evolution. This study aimed to describe the microbiological characteristics of NF-GNB causing PD-related peritonitis and analyze their influence on the outcome. (2) Methods: We analyze the 48 isolates from NF-GNB peritonitis, which were stored in our culture collection regarding bacterial resistance, biofilm, and other virulence factors’ production, and clonal profile. Additionally, we collected data on treatment and outcomes from patients’ clinical registers. (3) Results: The etiologies were species of Pseudomonas (50%), Acinetobacter (36%), and other NF-GNB (14%). There was a high (75%) proportion of biofilm producer lineages. The in vitro susceptibility rate of Pseudomonas spp. to amikacin, ciprofloxacin, and ceftazidime was significantly greater than that of Acinetobacter spp. and other species; however, there was a similar low-resolution rate (<45%) among the episodes attributable to them. Pseudomonas species have a polyclonal profile, while we found a clone of five multiresistant Acinetobacter baumannii over an 8-year interval (2000–2008), which suggest an origin from the healthcare environment. (4) Conclusions: We are not able to identify any predictor of outcome, but it is possible that biofilm and others virulence factors can act in concert and contribute to the bad outcome.

Bacteriophage therapy as an alternative biocontrol against emerging multidrug resistant E. coli in broilers

Avian pathogenic Escherichia coli (APEC) is considered a severe issue to both poultry business and health of the general public. In that context, 50 samples from 250 diseased broiler chickens in 10 chicken farms were employed to Escherichia coli isolation. Microbiological techniques were employed to detect isolates of E. coli from 250 diseased broiler chickens which were examined by antimicrobial susceptibility profiles against 11 antimicrobial agents using disc diffusion technique as well as their biofilm forming capacity were detected. In addition to, study the isolation and purification of phages based on spot technique to verify that lytic phages are present in E. coli isolates and plaque assay for titration of bacteriophages. In the present research, we also looked at the ability of bacteriophages to inhibit and dissolve previously formed biofilms by E. coli O78 isolate. Moreover, experimental testing of E. coli O78 bacteriophages for colibacillosis prevention and control in one day old broiler chicks were done. The obtained results showed that twenty-six E. coli isolates out of 50 examined samples were isolated (10.4%). The most prevalent serotypes were O78, O121:H7, O146:H2, O124, O113:H4, O112:H2, O1:H7, O55:H7, O2:H6, O91:H21, O26:H11. Antibiogram results demonstrated the resistance of E. coli isolates with high percentage 100% were against, Ampicillin, Amoxicillin and Tetracycline. Biofilm quantification analysis showed that 24/26 (92.3%) isolates were considered biofilm producer isolates. The characterization and the lytic activity of bacteriophage were performed based on Transmission electron microscopy and showed the greatest lytic activity against the evaluated host strains with effective activity at concentration of 10⁷ at 24 h and strong significant reduction of the established E. coli O 78 biofilm within 12 h. The result of experimental infection showed that the performance indicators of phage in treated and challenged group showed high significant increase in body weight, weight gain and improved FCR than infected –antibiotic treated and infected bacteriophage and antibiotic treated. Total viable cell counts of E. coli in the lungs of birds revealed that there is highly significant difference between the six groups count results. We concluded that phage therapy found to be an attractive option to prevent and control multidrug resistant colibacillosis in broilers.

Epidemiology, Molecular Characteristics, and Virulence Factors of Carbapenem-Resistant Pseudomonas aeruginosa Isolated from Patients with Urinary Tract Infections

Purpose

Pseudomonas aeruginosa is an important pathogen that causes urinary tract infections. Carbapenems are the drugs of choice for the treatment of P. aeruginosa infections. However, the emergence and spread of carbapenem-resistant P. aeruginosa (CRPA) is a serious global health threat. In this study, we investigated the epidemiology, molecular characteristics, drug resistance, and virulence factors of CRPA isolated from urine samples.

Methods

A total of 124 P. aeruginosa isolates were obtained from urine samples collected between March 2020 and February 2021. Clonal relatedness was evaluated using multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). We performed antimicrobial susceptibility tests and investigated the presence of carbapenemase genes and virulence factors in CRPA isolates.

Results

The carbapenem resistance rate of the isolated P. aeruginosa was 46.7% (59/124). A total of 54 (91.5%) out of the 59 CRPA isolates were identified as multidrug-resistant. The majority of the CRPA isolates (81.4%, 48/59) harbored carbapenemase genes, such as bla_IMP-6 or bla_NDM-1. In an epidemiological analysis using MLST, 88.1% of CRPA isolates were confirmed to be ST773 (50.8%, 30/59) or ST235 (37.3%, 22/59). The CRPA isolates harboring bla_IMP-6 and bla_NDM-1 belonged to ST235 (PFGE pulsotypes E1-E18, F) and ST773 (PFGE pulsotypes H1-H2, I1-I16) subtypes, respectively. The studied CRPA isolates simultaneously harbored 10 to 14 virulence factors of the 16 virulence factors examined. Nine virulence factor genes (toxA, exoT, plcH, plcN, phzM, phzS, lasB, aprA, and algD) were identified in all CRPA isolates.

Conclusion

Our study shows that P. aeruginosa ST235 harboring bla_IMP-6 and ST773 harboring bla_NDM-1—known internationally as high-risk clones with multiple virulence factors—are widely spread in the study area. These findings suggest that continuous monitoring is necessary to prevent the further spread of carbapenemase-producing CRPA.

Genetic diversity and molecular analysis of metallo beta lactamases among imipenem resistant clinical isolates of Pseudomonas aeruginosa from Peshawar, Pakistan

Objectives

Pseudomonas aeruginosa is an opportunistic pathogen with remarkable adaptation ability to thrive in diverse environmental conditions. This study aimed at phenotypic and molecular analysis of metallo beta lactamases (blaIMP, blaVIM, blaNDM-1 and blaSPM-1) and genetic diversity analysis among imipenem resistant clinical isolates of Pseudomonas aeruginosa.

Methods

This study was conducted from May 2017 to June 2018. The study included 187 Pseudomonas aeruginosa isolates collected from different clinical specimens from Peshawar, Pakistan. The isolates were analyzed for resistance to imipenem. Combined disc test (CDT) was then performed for phenotypic detection of metallo beta lactamases among imipenem resistant isolates of Pseudomonas aeruginosa. Molecular detection of metallo beta lactamases genes i.e. blaIMP, blaVIM, blaNDM-1 and blaSPM-1 was analyzed through polymerase chain reaction. Genetic diversity was determined through RAPD-PCR.

Results

MBL production was observed in 76% (n=19) isolates. The occurrence of MBL genes blaIMP, blaNDM-1 and blaVIM was 68% (n=17), 48% (n=12), and 4% (n=1) respectively. The blaSPM-1 gene was not detected. High genetic diversity was observed in current study. Out of 182 isolates 171 isolates showed different RAPD profiles (93.95% polymorphism); 160 were unique RAPD strains and based on similarity coefficient ≥ 80%, 22 isolates were clustered into 11 distinct clones.

Conclusion

A high prevalence of blaIMP and blaNDM-1 among imipenem resistant isolates of Pseudomonas aeruginosa is alarming that calls for proper control and prevention strategies. RAPD technique was found to be a good genotyping technique when limited resources are available.

Histone-Like Nucleoid Structuring Protein Modulates the Fitness of tet(X4)-Bearing IncX1 Plasmids in Gram-Negative Bacteria

The emergence of plasmid-mediated tigecycline resistance gene tet(X4) poses a challenging threat to public health. Based on the analysis of tet(X4)-positive plasmids in the NCBI database, we found that the IncX1-type plasmid is one of the most common vectors for spreading tet(X4) gene, but the mechanisms by which these plasmids adapt to host bacteria and maintain the persistence of antibiotic resistance genes (ARGs) remain unclear. Herein, we investigated the underlying mechanisms of how host bacteria modulate the fitness cost of IncX1 plasmids carrying tet(X4) gene. Interestingly, we found that the tet(X4)-bearing IncX1 plasmids encoding H-NS protein imposed low or no fitness cost in Escherichia coli and Klebsiella pneumoniae; instead, they partially promoted the virulence and biofilm formation in host bacteria. Regression analysis revealed that the expression of hns gene in plasmids was positively linked to the relative fitness of host bacteria. Furthermore, when pCE2::hns was introduced, the fitness of tet(X4)-positive IncX1 plasmid pRF55-1 without hns gene was significantly improved, indicating that hns mediates the improvement of fitness. Finally, we showed that the expression of hns gene is negatively correlated with the expression of tet(X4) gene, suggesting that the regulatory effect of H-NS on adaptability may be attributed to its inhibitory effect on the expression of ARGs. Together, our findings suggest the important role of plasmid-encoded H-NS protein in modulating the fitness of tet(X4)-bearing IncX1 plasmids, which shed new insight into the dissemination of tet(X4) gene in a biological environment.

Correlation between phenotypic virulence traits and antibiotic resistance in Pseudomonas aeruginosa clinical isolates

Pseudomonas aeruginosa is a ubiquitous pathogen capable of infecting virtually all tissues and its one of the standout amongst the most hazardous microorganisms of high morbidity and mortality rates especially in debilitated patients with few successful antibiotic choices available. This pathogen regulating most virulence traits by that so-called quorum sensing (QS), a cell to cell communication system. the present study was intended to phenotypically evaluate the activity of specific virulence traits (including swarming and swimming motility, protease, pyocyanin, and biofilm production) in Pseudomonas aeruginosa clinical isolates and assess the statistical correlation between these traits and antibiotic resistance. One hundred and thirteen bacterial isolates were obtained from different clinical samples and identified as P. aeruginosa, among them, 73.4% have the ability to forming biofilm with different degrees; 59.2% were able to produce pyocyanin pigment while all isolates having the ability to make swarming and swimming motility and able to produce protease enzyme with different degrees. The isolates that produce the higher levels of the virulence traits were identified by both biochemical using Vitek2 automated system and genetically via 16s rRNA gene analysis. The statistical analysis results indicate that a positive significant correlation was found between biofilm formation and other studied virulence traits except for protease (r = 0.584: 0.324, P < 0.05) while a non-significant correlation was found between biofilm formation and protease activity (r = 0.105, P ˃ 0.05). Swimming and swarming motility have a positive significant correlation with other studied virulence traits (r = 0.613: 0.297, P < 0.05) except for protease. Pyocyanin pigment production have a positive significant correlation with other studied virulence traits (r = 0.33: 0.297, P < 0.05) except for protease. on the other hand, negative significant correlations were found between biofilm formation, swimming; and swarming motility, Pyocyanin pigment production, and the susceptibility of antibiotics (r = -0.512: -0.281, P < 0.05). Detection of such correlations in P. aeruginosa is useful for study the behavior of this pathogen and may be provide a new target for the treatment of MDR infections.

Ecthyma gangrenosum as a serious complication of Pseudomonas aeruginosa infection in departments of paediatric oncology

In most cases ecthyma gangrenosum is a consequence of Pseudomonas aeruginosa bloodstream infection in immunodeficient patients. This bacterium is characterized by multi-drug resistance and has a number of mechanisms that allow it to survive even in extreme conditions. The disease is characterized by an aggressive course involving the skin and mucous membranes, leading to ulceration with signs of necrosis within 12 to 24 h. Treatment includes targeted antibiotic therapy and surgical cleansing of the wound. If the perianal area is occupied, a colostomy may be performed. Prevention of bacterial infections involves taking special precautions when handling a patient with immunodeficiency.

Clinical outcome from hematopoietic cell transplant patients with bloodstream infection caused by carbapenem-resistant P. aeruginosa and the impact of antimicrobial combination in vitro

Bloodstream infection (BSI) caused by carbapenem-resistant P. aeruginosa (CRPA) has high mortality in hematopoietic stem cell transplant (HSCT) recipients. We performed MIC, checkerboard, time-kill assay, PFGE, PCR, and whole genome sequence and described the clinical outcome through Epi Info comparing the antimicrobial combination in vitro. Mortality was higher in BSI caused by CRPA carrying the lasB virulence gene. The isolates were 97% resistant to meropenem displaying synergistic effect to 57% in combination with colistin. Seventy-three percent of the isolates harbored bla_SPM-1 and Tn4371 and belonged to ST277. The synergistic effect in vitro with meropenem with colistin appeared to be a better therapeutic option.

Emergence of rmtD1 gene in clinical isolates of Pseudomonas aeruginosa carrying blaKPC and/or blaVIM-2 genes in Brazil

OBJECTIVES

The aim of the present study is to describe clinical aminoglycoside- or carbapenem-resistant Pseudomonas aeruginosa isolates collected between 2018 and 2019 in a hospital in Recife City, Northeastern Brazil. It was done based on phenotypic and molecular markers of antimicrobial resistance, as well as on the clonal diversity of the investigated isolates.

METHODS

Thirty-four carbapenem- and/or aminoglycoside-resistant P. aeruginosa isolates were collected in a hospital in Recife City-PE, Brazil. Their antimicrobial susceptibility profile was identified based on the automated BD Phoenix ™ system. In addition, broth microdilution was performed to determine the MICs of tobramycin and polymyxin B. Eventually, isolates were subjected to PCR and sequencing in order to detect the carbapenemase enzyme (bla_KPC, bla_NDM, bla_VIM, bla_SPM-1, and bla_IMP) and 16S rRNA methylase (armA, rmtB, rmtD, rmtF, and rmtG) genes; ERIC-PCR was conducted for clonal profile determination purposes.

RESULTS

Thirty-four of the 64 isolates evaluated in the present study were selected for complementary molecular phenotypic tests, based on sample inclusion criteria. The bla_KPC and bla_VIM-2 genes were identified in 32.4% (11/34) and 38.2% (13/34) of tested isolates, respectively. The rmtD1 gene was detected in 32.4% (11/34) of analyzed isolates. Eight isolates carried both the bla_KPC and rmtD1 genes, whereas bla_VIM-2 and rmtD1 genes co-occurrence was detected in three strains; one isolate had all bla_KPC, bla_VIM-2, and rmtD1 genes. ERIC-PCR molecular typing has evidenced cross-transmission of three pathogenic clones among patients in the hospital.

CONCLUSIONS

The present study is a pioneer in describing isolates harboring both bla_VIM-2 and rmtD1 genes. Moreover, it emphasizes the need of conducting local molecular epidemiology studies at different time intervals in order to monitor measures adopted to prevent nosocomial infections in different hospital units.

Resistance mechanisms and genetic relatedness among carbapenem-resistant Pseudomonas aeruginosa isolates from three major hospitals in Hanoi, Vietnam (2011-15)

Background

MDR bacteria including carbapenem-resistant Pseudomonas aeruginosa are recognized as an important cause of hospital-acquired infections worldwide. This investigation seeks to determine the molecular characterization and antibiotic resistance genes associated with carbapenem-resistant P. aeruginosa.

Methods

We conducted WGS and phylogenetic analysis of 72 carbapenem-resistant P. aeruginosa isolated from hospital-acquired infection patients from August 2011 to March 2015 in three major hospitals in Hanoi, Vietnam.

Results

We identified three variants of IMP gene, among which bla_IMP-15 was the most frequent (n = 34) in comparison to bla_IMP-26 (n = 2) and bla_IMP-51 (n = 12). We observed two isolates with imipenem MIC >128 mg/L that co-harboured bla_IMP-15 and bla_DIM-1 genes and seven isolates (imipenem MIC > 128 mg/L) with a bla_KPC-1 gene from the same hospital. MLST data shows that these 72 isolates belong to 18 STs and phylogenetic tree analysis has divided these isolates into nine groups.

Conclusions

Our results provide evidence that not only bla_IMP-26 but other IMP variants such as bla_IMP-15 and bla_IMP-51 genes and several STs (ST235, ST244, ST277, ST310, ST773 and ST3151) have been disseminating in healthcare settings in Vietnam. In addition, we report the emergence of two isolates belonging to ST1240 and ST3340 that harboured two important carbapenemase genes (bla_IMP-15 and bla_DIM-1) and seven isolates belonging to ST3151 of P. aeruginosa that carried the bla_KPC-1 gene in Vietnam, which could potentially cause serious restricted availability of treatment options in healthcare settings.

Pathogenesis of Gram-Negative Bacteremia

Gram-negative bacteremia is a devastating public health threat, with high mortality in vulnerable populations and significant costs to the global economy. Concerningly, rates of both Gram-negative bacteremia and antimicrobial resistance in the causative species are increasing. Gram-negative bacteremia develops in three phases. First, bacteria invade or colonize initial sites of infection. Second, bacteria overcome host barriers, such as immune responses, and disseminate from initial body sites to the bloodstream. Third, bacteria adapt to survive in the blood and blood-filtering organs. To develop new therapies, it is critical to define species-specific and multispecies fitness factors required for bacteremia in model systems that are relevant to human infection. A small subset of species is responsible for the majority of Gram-negative bacteremia cases, including Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii The few bacteremia fitness factors identified in these prominent Gram-negative species demonstrate shared and unique pathogenic mechanisms at each phase of bacteremia progression. Capsule production, adhesins, and metabolic flexibility are common mediators, whereas only some species utilize toxins. This review provides an overview of Gram-negative bacteremia, compares animal models for bacteremia, and discusses prevalent Gram-negative bacteremia species.

Antibiogram profile and virulence signatures of Pseudomonas aeruginosa isolates recovered from selected agrestic hospital effluents

Hospital wastewater (HWW) harbours diverse microbial species and a miscellany of genome that would facilitate the emergence of novel pathogen upon genome integration that manifests novel traits in infectious pathogens. The study aimed to determine the antibiogram, and virulence signatures of Pseudomonas aeruginosa (P. aeruginosa) recovered from selected agrestic hospital effluents in Eastern Cape, South Africa. Thirty-six (36) wastewater samples were collected from selected hospital drains between February 2018 and April 2018, processed and analyzed by culture-dependent methods for the isolation of P. aeruginosa. The identity confirmation of isolates was achieved by amplification of oprl and oprL genes. Antibiogram was done using standard disk diffusion technique of Kirby-Bauer as approved by CLSI 2018 guidelines. Virulence signatures (lasA, lasB, toxA, popB) among isolates were analysed using polymerase chain reaction. A total of 54 P. aeruginosa isolates were confirmed by amplification of oprl and oprL genes in the hospital wastewater effluent samples. The isolates showed a 100% susceptibility to gentamicin, amikacin and imipenem antimicrobial agents. Ceftazidime recorded the most resistance (63%) against the isolates studied. Other antibiotics had a resistance range of 7% and 35%. The MAR index among the isolates revealed a range of 0.23 and 0.38. ToxA virulence gene was detected in all isolates while popB, lasB, lasA were detected in 82%, 75% and 54% of the isolates. This study reveals P. aeruginosa isolates with virulence traits and some strains showing multiple antibiotic resistance. The multiple antibiotic resistance index (MARI) of ≥ 0.2 indicates that the some isolates may have emerged from high-risk sources, thus projecting a risk to public health. However, with the high sensitivity pattern observed among the studied isolates, most of the antibiotics used in the susceptibility tests are not at peril. Hence, the use of these antibiotics is encouraged for treatment of infection attributed to P. aeruginosa. It is also pertinent to initiate strict control and rigid antibiotics therapeutic policy with surveillance programmes for multidrug-resistant pathogens to forestall the development and transmission of resistance traits in the pathogens.

Resistance Profiles and Biological Characteristics of Rifampicin-Resistant Staphylococcus aureus Small-Colony Variants

Background

Staphylococcus aureus (S. aureus) is a major contributor to nosocomial and community-acquired infections. S. aureus small colony variants (SCVs) which changed in relevant phenotype have made more limited and difficult for therapeutic options against S. aureus infections increasingly. Rifampicin is considered as the "last-resort" antibiotic against S. aureus. Our study investigated resistance profiles and biological characteristics of rifampicin-resistant S. aureus SCVs.

Methods

We collected S. aureus SCVs that were selected from 41 rifampicin-resistant clinical isolates. Then, biological characteristics, resistance spectrum, and rifampicin resistance mechanisms of tested S. aureus SCVs and corresponding parental strains were investigated by classic microbiological methods, agar dilution method, polymerase chain reaction (PCR). Moreover, the fitness cost of S. aureus SCVs, including growth, biofilm formation ability, and virulence profile, was also determined by bacterial growth curve assay, biofilm formation assay, and Galleria mellonella infection model.

Results

There were three S. aureus SCVs (JP310 SCVs, JP1450 SCVs, JP1486 SCVs) that were selected from 41 rifampicin-resistant S. aureus. S. aureus SCVs colonies were tiny, with decreased pigmentation, and the hemolysis circle was not obvious compared with corresponding parental strains. And SCVs could not be restored to normal-colony phenotype after hemin, menaquinone, or thymidine supplementation. Different rpoB mutations occurred in JP1486 SCVs. Antimicrobial susceptibility testing revealed MICs of SCVs were higher than corresponding parental strains. Besides, the growth ability and virulence of SCVs were lower, and biofilm formation ability of which increased compared with parental strains.

Conclusion

S. aureus SCVs share the rifampicin resistance mechanisms with parental strains, although there were some differences in the position of rpoB mutations. Moreover, we found that the biological characteristics of SCVs were significantly different from corresponding parental strains. In contrast, decreased susceptibility to other antibiotics of SCVs was observed during phenotype switch. Furthermore, SCVs incur the fitness cost.

Epidemiology of and risk factors for mortality due to carbapenemase-producing organisms (CPO) in healthcare facilities

BACKGROUND

Carbapenemase-producing organisms (CPO) have been largely responsible for the extensive spread of carbapenem resistance, and their prevalence is increasing in many parts of the world.

AIM

To evaluate clinical and molecular epidemiology and mortality associated with CPO among patients.

METHODS

All CPO from clinical and long-term healthcare surveillance cultures across Scotland in 2003-2017 were reviewed retrospectively. Polymerase chain reaction was used to detect genes coding for carbapenemases. A generalized linear mixed model was used to identify risk factors for mortality.

FINDINGS

In total, 290 individuals with CPO were identified. The overall incidence increased over time (P<0.001) from 0.02 to 1.38 per 100,000 population between 2003 and 2017. A total of 243 distinct CPO isolates were obtained from 269 isolations in 214 individuals with available metadata. The majority of the isolates were Enterobacterales (206/243, 84.8%), and Klebsiella pneumoniae (65/206, 31.6%) and Enterobacter cloacae (52/206, 25.2%) were the most common species. VIM (75/243, 30.9%) and NDM (56/243, 23.0%) were the most common carbapenemases. The crude 30-day mortality rate was 11.8% (25/211), while the case fatality rate was 5.7% (12/211). Age >60 years [adjusted odds ratio (aOR) 3.36, 95% confidence interval (CI) 1.06-10.63; P=0.033], presence of non-fermenters (aOR 4.88, 95% CI 1.64-14.47; P=0.005), and systemic infection or organ failure (aOR 4.21, 95% CI 1.38-12.81; P=0.032) were independently associated with 30-day mortality.

CONCLUSION

The incidence of CPO in Scotland is low but increasing. Awareness is required that inpatients aged >60 years, patients with systemic infection or organ failure, and patients presenting with non-fermenters are at higher risk of death from CPO.

Prevalence of the Genes Associated with Biofilm and Toxins Synthesis amongst the Pseudomonas aeruginosa Clinical Strains

Pseudomonas aeruginosa is one of the most commonly isolated bacteria from clinical specimens, with an increasing isolation frequency in nosocomial outbreaks. The hypothesis tested was whether carbapenem-resistant P. aeruginosa strains display an altered carriage of the virulence factor genes, depending on the type of carbapenem resistance. The aim of the study was to investigate, by PCR, the frequency of 10 chosen virulence factors genes (phzM, phzS, exoT, exoY, exoU, toxA, exoS, algD, pilA and pilB) and the genotype distribution in 107 non-duplicated carbapenem-resistant P. aeruginosa isolates. P. aeruginosa genes involved in phenazine dyes and exoenzyme T synthesis were noted with the highest frequency (100%). Fimbriae-encoding genes were detected with the lowest incidence: 15.9% and 4.7% for pilin A and B, respectively. The differences observed between the exoS gene prevalence amongst the carbapenemase-positive and the carbapenemase-negative strains and the pilA gene prevalence amongst the strains of different origins were statistically significant. Virulence genes’ prevalence and the genotype distribution vary amongst P. aeruginosa strains resistant to carbapenems, especially in terms of their carbapenemase synthesis ability and the strain origin.

Decreased Biofilm Formation Ability of a Multidrug-Resistant Pseudomonas aeruginosa Strain After Exposure to a Simulated Microgravity Environment

Background: The refractory infection induced by multidrug-resistant (MDR) Pseudomonas aeruginosa has become one of the most urgent problems in hospitals. The biofilms formed by P. aeruginosa increase its resistance to antibiotics. A simulated microgravity (SMG) environment provides a platform to understand the factors affecting biofilm formation in bacteria. Objectives: This study aimed to investigate the SMG effects on MDR P. aeruginosa biofilm formation and explore the relevant mechanisms. Methods: In this study, a clinostat was used to simulate a microgravity (MG) environment. The motility and biofilm formation ability of MDR P. aeruginosa were observed using the swimming test and the crystal violet staining method, respectively. The underlying mechanism of phenotypic changes was further investigated by comparative transcriptomic analysis. Results: Multidrug-resistant P. aeruginosa grown under the SMG condition exhibited decreased swimming motility and biofilm formation ability compared to those under the normal gravity (NG) condition. Further analysis revealed that the decreased swimming motility and biofilm formation ability could be attributed to the downregulated expression of genes responsible for flagellar synthesis (flhB, fliQ, and fliR) and type IV pili biogenesis (pilDEXY1Y2VW). Conclusions: This is the first study to perform experiments on MDR P. aeruginosa under the SMG condition. It will be beneficial to understand the mechanism of MDR P. aeruginosa biofilm formation and develop new treatment strategies for infectious diseases induced by MDR P. aeruginosa in the future.

It's Not Easy Being Green: A Narrative Review on the Microbiology, Virulence and Therapeutic Prospects of Multidrug-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most frequent cause of infection among non-fermenting Gram-negative bacteria, predominantly affecting immunocompromised patients, but its pathogenic role should not be disregarded in immunocompetent patients. These pathogens present a concerning therapeutic challenge to clinicians, both in community and in hospital settings, due to their increasing prevalence of resistance, and this may lead to prolonged therapy, sequelae, and excess mortality in the affected patient population. The resistance mechanisms of P. aeruginosa may be classified into intrinsic and acquired resistance mechanisms. These mechanisms lead to occurrence of resistant strains against important antibiotics-relevant in the treatment of P. aeruginosa infections-such as β-lactams, quinolones, aminoglycosides, and colistin. The occurrence of a specific resistotype of P. aeruginosa, namely the emergence of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) strains, has received substantial attention from clinical microbiologists and infection control specialists; nevertheless, the available literature on this topic is still scarce. The aim of this present review paper is to provide a concise summary on the adaptability, virulence, and antibiotic resistance of P. aeruginosa to a readership of basic scientists and clinicians.

Phenotypic and genotypic analysis of biofilm production by Pseudomonas aeruginosa isolates from infection and colonization samples

INTRODUCTION

Pseudomonas aeruginosa is an opportunistic pathogen associated with healthcare-related infections, affecting mainly patients with underlying diseases and immunosuppression. This microorganism has several virulence mechanisms that favour its pathogenesis, including the production of biofilm. This study aimed to analyze the phenotypic production of biofilms, the occurrence of quorum sensing (QS) genes, and the clonal profile of clinical isolates of P. aeruginosa from colonized/infected patients in a tertiary hospital in Recife-PE.

METHODS

We obtained 21 isolates that were classified as infection isolates (II), and 10 colonization isolates (CI). The phenotypic analysis for biofilm production was performed quantitatively. The QS genes were detected by specific PCRs, and the clonal profile was assessed using ERIC-PCR.

RESULTS

Of the 31 isolates, 58.1 % (18/31) were biofilm producers, of which 70 % (7/10) were CI and classified as weakly adherent; 52.4 % (11/21) of the II produced biofilms, and were classified as weak (38.1 %, (8/21)), moderate (9.5 %, (2/21)), and strongly adherent (4.8 %, (1/21)). All isolates harbored the QS genes analyzed. In the clonal analysis, 26 distinct genetic profiles were identified, highlighting the presence of a clone in four samples, i.e., one infection isolate, and 3 colonization isolates.

CONCLUSIONS

The detection of biofilm formation is important in P. aeruginosa in addition to the identification of colonization and infection isolates, especially from complex environments such as ICUs. Further, we define a strategy for monitoring and analyzing P. aeruginosa strains that can potentially cause infections in hospitalized patients.

Update on the epidemiology of carbapenemases in Latin America and the Caribbean

INTRODUCTION

Carbapenemases are β-lactamases able to hydrolyze a wide range of β-lactam antibiotics, including carbapenems. Carbapenemase production in Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter spp., with and without the co-expression of other β-lactamases is a serious public health threat. Carbapenemases belong to three main classes according to the Ambler classification: class A, class B, and class D.

AREAS COVERED

Carbapenemase-bearing pathogens are endemic in Latin America. In this review, we update the status of carbapenemases in Latin America and the Caribbean.

EXPERT OPINION

Understanding the current epidemiology of carbapenemases in Latin America and the Caribbean is of critical importance to improve infection control policies limiting the dissemination of multi-drug-resistant pathogens and in implementing appropriate antimicrobial therapy.

Detection of Carbapenem-Resistant Genes in Escherichia coli Isolated from Drinking Water in Khartoum, Sudan

Waterborne Escherichia coli are a major reservoir of antimicrobial resistance (AMR). Carbapenem-resistance, especially when mediated by transferable carbapenemase-encoding genes, is spreading worldwide and causing dramatically limiting treatment options. In our country, studies for the detection of carbapenem resistance in drinking water do not exist; therefore, this work was carried out to determine the prevalence of carbapenem-resistant genes “bla_KPC, bla_IMP, bla_NDM, bla_SPM, bla_VIM, and bla_OXA-48” among Escherichia coli isolated from drinking water in Khartoum, Sudan. A total of forty-five E. coli bacteria were isolated from different sources of drinking water. Antimicrobial susceptibility testing was performed using imipenem (10 mg/disc), gentamicin (10 mg/disc), ceftriaxone (30 mg/disc), ciprofloxacin (5 mg/disc), chloramphenicol (30 mg/disc), and tetracycline (30 mg/disc). “Sensitive” or “resistant” patterns of E. coli were judged using antibiotic minimum inhibitory concentration (MIC). Bacterial genomic DNA was extracted by the boiling method, and then multiplex polymerase chain reaction was performed to detect the carbapenemase genes (bla_KPC, bla_IMP, bla_NDM, bla_SPM, bla_VIM, and bla_OXA-48). Multiplex PCR assays confirmed the presence of carbapenemase genes in 28% of all water isolates. OXA-48 gene was the most predominant gene, detected in 15.5% of the isolates. The bla_KPC and bla_SPM genes were also detected in 4.4% and 8.8% of the isolates, respectively. However, the isolates were negative for bla_NDM, bla_VIM, and bla_IMP genes. The isolates showed a high rate of tetracycline resistance (97.7%), followed by gentamicin (57.7%), ciprofloxacin (46.6%), ceftriaxone (35.5%), and chloramphenicol (31.1%). In conclusion, this study confirmed for the first time the presence of E. coli carried carbapenem-resistant genes in the drinking water of Khartoum state, Sudan. These isolates commonly carried OXA-48 (7/45), followed by SPM (4/45) and KPC (2/45).

Molecular epidemiology of Pseudomonas aeruginosa isolated from lower respiratory tract of ICU patients

Lower respiratory tract infections (LRTIs) caused by Pseudomonas aeruginosa are the most common infection among hospitalized patients, associated with increased levels of morbidity, mortality and attributable health care costs. Increased resistant Pseudomonas worldwide has been quite meaningful to patients, especially in intensive care unit (ICUs). Different species of Pseudomonas exhibit different genetic profile and varied drug resistance. The present study determines the molecular epidemiology through DNA fingerprinting method and drug resistance of P. aeruginosa isolated from patients with LTRIs admitted in ICU. A total of 79 P. aeruginosa isolated from patients with LRTIs admitted in ICU were characterized by Restriction Fragment Length Polymorphism (RFLP), Random Amplified Polymorphic DNA (RAPD) and Repetitive Extrapalindromic PCR (REP-PCR). Antibiotic resistance was determined by minimum inhibitory concentration (MIC) assay while MDR genes, viz, blaTEM, blaOXA, blaVIM, blaCTX-M-15 were detected by polymerase chain reaction (PCR). Of the 137 Pseudomonas sp isolated from ICU patients, 57.7% of the isolates were reported to be P. aeruginosa. The overall prevalence of P. aeruginosa among the all included patients was 34.5%. The RAPD analysis yielded 45 different patterns with 72 clusters with 57% to 100% similarity level. The RFLP analysis yielded 8 different patterns with 14 clusters with 76% to 100% similarity level. The REP PCR analysis yielded 37 different patterns with 65 clusters with 56% to 100% similarity level. There was no correlation among the different DNA patterns observed between the three different methods. Predominant of the isolates (46.8%) were resistant to amikacin. Of the 79 isolates, 60.8% were positive for blaTEM gene and 39.2% were positive for blaOXA gene. P. aeruginosa was predominantly isolated from patients with LRTIs admitted in ICU. The difference in the similarity level observed between the three DNA fingerprinting methods indicates that there is high inter-strain variability. The high genetic variability and resistance patterns indicates that we should continuously monitor the trend in the prevalence and antibiotic resistance of P. aeruginosa especially in patients with LRTIs admitted in ICU.

Coordination of las regulated virulence factors with Multidrug-Resistant and extensively drug-resistant in superbug strains of P. aeruginosa

Successful pathogenicity often resulted from a complicated association between virulence and antibiotic resistance in Pseudomonas aeruginosa infections. Therefore, the current study aimed to investigate the relationship between the las system and antibiotic resistance. Seventy-three (73) P. aeruginosa isolates were collected from burn wounds (26.02%), blood cultures (30.13%), catheters (12.32%), and urine culture (31.50%). Among the 73 collected isolates, 22 isolates were considered as multi-drug resistant (MDR) and 11 isolates as extensively-drug resistant (XDR). Furthermore, phenazines and LasA protease were detected among 21.91% and 32.87% of isolates, respectively. Quantitative real-time PCR assessment of KPC, MBL, and lasI/R indicated that resistance and virulence factors are more expressed in XDR strains than MDR strains. Also, the expression level of KPC and MBL reduced in non-biofilm forming strains. However, increased expression levels of lasI, lasR, and the KPC genes were observed in LasA and LasB protease producing strains. Interestingly, 16 known sequence types (including ST108, ST260, ST217) and three novel STs (ST2452, ST2427, and ST2542) were characterized among the collected isolates, which are related to the virulence and resistance. In MDR-XDR strains, a strong correlation between lasI/R and the variants of antibiotic resistance genes was found. In conclusion, the pathogenicity of P. aeruginosa may increase the prevalence of antibiotic-resistant strains.

Mechanisms of Heteroresistance and Resistance to Imipenem in Pseudomonas aeruginosa

Background

Heteroresistance is a phenomenon that occurs in all bacteria and can cause treatment failure. Yet, the exact mechanisms responsible for heteroresistance still remain unknown. The following study investigated the mechanisms of imipenem-heteroresistance and -resistance in Pseudomonas aeruginosa clinical isolates from Wenzhou, China.

Methods

Imipenem resistance was detected by the agar dilution method; heteroresistance was determined by population analysis profiles. Biofilm formation assay and modified carbapenem inactivation methods were also performed. Polymerase chain reaction (PCR) was conducted to detect oprD, and quantitative real-time PCR was used to determine expression levels of oprD, ampC and four efflux pump coding genes (mexB, mexD, mexE and mexY).

Results

Six imipenem-heteroresistant and -resistant P. aeruginosa isolates were selected respectively. Deficient oprD was detected in all resistant isolates and two heteroresistant isolates. No strains produced carbapenemases. Expression levels of oprD were down-regulated in heteroresistant isolates. Transcription levels of the mexE and mexY were significantly increased in all heterogeneous subpopulations compared with their respective native ones. Compared with the susceptible group, increased mean relative expression levels of mexE and mexY or the decreased mean relative expression levels of oprD were observed in the resistant group (P < 0.05), whereas transcription levels of the mexB and mexD remained unchanged.

Conclusion

Down-regulation of oprD contributed to the resistance and heteroresistance of imipenem in our P. aeruginosa clinical isolates. In addition, the marginal up-regulation of efflux systems may indirectly affect imipenem resistance. Contrarily, defective oprD was less common in our experimental heteroresistant strains than resistant strains.

Pseudomonas infections among hospitalized adults in Latin America: a systematic review and meta-analysis

Background

Treatment of resistant Pseudomonas aeruginosa infection continues to be a challenge in Latin American countries (LATAM). We synthesize the literature on the use of appropriate initial antibiotic therapy (AIAT) and inappropriate initial antibiotic therapy (IIAT) in P. aeruginosa infections, and the literature on risk factors for acquisition of resistant P. aeruginosa among hospitalized adult patients in LATAM.

Methods

MEDLINE, EMBASE, Cochrane, and LILAC were searched between 2000 and August 2019. Abstracts and full-text articles were screened in duplicate. Random effects meta-analysis was conducted when studies were sufficiently similar.

Results

The screening of 165 citations identified through literature search yielded 98 full-text articles that were retrieved and assessed for eligibility, and 19 articles conducted in Brazil (14 articles), Colombia (4 articles), and Cuba (1 article) met the inclusion criteria. Of 19 eligible articles, six articles (840 subjects) examined AIAT compared to IIAT in P. aeruginosa infections; 17 articles (3203 total subjects) examined risk factors for acquisition of resistant P. aeruginosa; and four articles evaluated both. Four of 19 articles were rated low risk of bias and the remaining were deemed unclear or high risk of bias. In meta-analysis, AIAT was associated with lower mortality for P. aeruginosa infections (unadjusted summary OR 0.48, 95% CI 0.28–0.81; I² = 59%), compared to IIAT and the association with mortality persisted in subgroup meta-analysis by low risk of bias (3 articles; unadjusted summary OR 0.46, 95% CI 0.28–0.81; I² = 0%). No meta-analysis was performed for studies evaluating risk factors for acquisition of resistant P. aeruginosa as they were not sufficiently similar. Significant risk factors for acquisition of resistant P. aeruginosa included: prior use of antibiotics (11 articles), stay in the intensive care unit (ICU) (3 articles), and comorbidity score (3 articles). Outcomes were graded to be of low strength of evidence owing to unclear or high risk of bias and imprecise estimates.

Conclusion

Our study highlights the association of AIAT with lower mortality and prior use of antibiotics significantly predicts acquiring resistant P. aeruginosa infections. This review reinforces the need for rigorous and structured antimicrobial stewardship programs in the LATAM region.

Virulence Factors Of Carbapenem-Resistant Pseudomonas aeruginosa In Hospital-Acquired Infections In Mansoura, Egypt

Purpose

The problem of carbapenem-resistant Pseudomonas aeruginosa in health-care settings is growing worse. This study was conducted to investigate the rate of carbapenemase genes, antibiotic resistance, and virulence factors in carbapenem-resistant P. aeruginosa associated with hospital-acquired infections.

Patients and methods

Isolates of P. aeruginosa were collected from patients with hospital-acquired infections at Mansoura University Hospital in Mansoura. Carbapenem susceptibility was done by broth dilution. The presence of carbapenemase genes and quorum-sensing genes was assessed by PCR. Production of protease, pyocyanin, twitching motility, hemolytic activity and biofilm formation was evaluated.

Results

Out of 80 P. aeruginosa isolates, 34 (42.5%) were resistant to carbapenem. Among carbapenem-resistant P. aeruginosa isolates, 21 (61.8%) were carbapenemase producers. The most prevalent gene detected was blaVIM. The frequency of protease, pyocyanin, twitching motility, hemolytic activity and biofilm formation was 76.2%, 58.8%, 83.8%, 93.8% and 77.5%, respectively. Biofilm formation was significantly associated with carbapenem-resistant P. aeruginosa. On the other hand, pyocyanin production was significantly lower in carbapenem-resistant isolates. No correlation existed between carbapenem resistance and any other studied virulence factors or quorum-sensing genes.

Conclusion

Association of carbapenem-resistant P. aeruginosa with other antibiotic resistance or the presence of virulence factors in hospital-acquired infection may represent a warning that enhances the need for a stringent surveillance program.

Antimicrobial and Antibiofilm Activities of Helical Antimicrobial Peptide Sequences Incorporating Metal-Binding Motifs

Antimicrobial peptides (AMPs) represent alternative strategies to combat the global health problem of antibiotic resistance. However, naturally occurring AMPs are generally not sufficiently active for use as antibiotics. Optimized synthetic versions incorporating additional design principles are needed. Here, we engineered amino-terminal Cu(II) and Ni(II) (ATCUN) binding motifs, which can enhance biological function, into the native sequence of two AMPs, CM15 and citropin1.1. The incorporation of metal-binding motifs modulated the antimicrobial activity of synthetic peptides against a panel of carbapenem-resistant enterococci (CRE) bacteria, including carbapenem-resistant Klebsiella pneumoniae (KpC+) and Escherichia coli (KpC+). Activity modulation depended on the type of ATCUN variant utilized. Membrane permeability assays revealed that the in silico selected lead template, CM15, and its ATCUN analogs increased bacterial cell death. Mass spectrometry, circular dichroism, and molecular dynamics simulations indicated that coordinating ATCUN derivatives with Cu(II) ions did not increase the helical tendencies of the AMPs. CM15 ATCUN variants, when combined with Meropenem, streptomycin, or chloramphenicol, showed synergistic effects against E. coli (KpC+ 1812446) biofilms. Motif addition also reduced the hemolytic activity of the wild-type AMP and improved the survival rate of mice in a systemic infection model. The dependence of these bioactivities on the particular amino acids of the ATCUN motif highlights the possible use of size, charge, and hydrophobicity to fine-tune AMP biological function. Our data indicate that incorporating metal-binding motifs into peptide sequences leads to synthetic variants with modified biological properties. These principles may be applied to augment the activities of other peptide sequences.

Metallo-Beta-Lactamase Producing Pseudomonas aeruginosa in a Healthcare Setting in Alexandria, Egypt

Pseudomonas aeruginosa has emerged as a major healthcare associated pathogen that creates a serious public health disaster in both developing and developed countries. In this work we aimed at studying the occurrence of metallo-beta-lactamase (MBL) producing P. aeruginosa in a healthcare setting in Alexandria, Egypt. This cross sectional study included 1583 clinical samples that were collected from patients admitted to Alexandria University Students' Hospital. P. aeruginosa isolates were identified using standard microbiological methods and were tested for their antimicrobial susceptibility patterns using single disc diffusion method according to the Clinical and Laboratory Standards Institute recommendations. Thirty P. aeruginosa isolates were randomly selected and tested for their MBL production by both phenotypic and genotypic methods. Diagnostic Epsilometer test was done to detect metallo-beta-lactamase enzyme producers and polymerase chain reaction test was done to detect imipenemase (IMP), Verona integron-encoded (VIM) and Sao Paulo metallo-beta-lactamase (IMP) encoding genes. Of the 1583 clinical samples, 175 (11.3%) P. aeruginosa isolates were identified. All the 30 (100%) selected P. aeruginosa isolates that were tested for MBL production by Epsilometer test were found to be positive; where 19 (63.3%) revealed blaSPM gene and 11 (36.7%) had blaIMP gene. blaVIM gene was not detected in any of the tested isolates. Isolates of MBL producing P. aeruginosa were highly susceptible to polymyxin B 26 (86.7%) and highly resistant to amikacin 26 (86.7%). MBL producers were detected phenotypically by Epsilometer test in both carbapenem susceptible and resistant P. aeruginosa isolates. blaSPM was the most commonly detected MBL gene in P. aeruginosa isolates.

Virulence factors and integrons are associated with MDR and XDR phenotypes in nosocomial strains of Pseudomonas aeruginosa in a Venezuelan university hospital

Multidrug resistance (MDR), virulence and transferable elements potentiate Pseudomonas aeruginosa's role as an opportunistic pathogen creating a high risk for public health. In this study, we evaluated the possible association of multidrug resistance, virulence factors and integrons with intrahospital P. aeruginosa strains isolated from patients at Cumana hospital, Venezuela. Relevant clinical-epidemiological data were collected to study 176 strains (2009-2016) isolated from different hospital units. Bacterial resistance was classified as susceptible, low-level resistant (LDR), multidrug resistant (MDR) and extensively drug-resistant (XDR). Most strains produced pyoverdine, DNase, gelatinase and hemolysin. Around 73% of the strains showed some type of movement. MDR and XDR strains increased from 2009 (24.2% and 4.8%, respectively) to 2016 (53.1% and 18.8%); while LDR decreased from 64.5% to 6.3%. The exoU and exoS genes were found in a significant number of strains (38.1 and 7.4%, respectively). Class I integrons were detected in 35.8% of the strains and the frequency was associated with resistance (42.9, 22.4, 41.4 and 61.9%, for susceptible, LDR, MDR and XDR, respectively). The MDR/XDR strains were positively associated with hemolysins and exoU, but negatively associated with bacterial twitching. MDR/XDR phenotypes were also associated with the Intensive Care Unit (ICU), septicemia, bronchial infection and diabetic foot ulcers, as well as long hospital stay (≥10 days) and previous antimicrobial treatment. High frequency of MDR/XDR strains and their association with class I integrons and virulence factors can increase the infection potential, as well as morbidity and mortality of patients attending this hospital and could spread infection to the community, creating a health risk for the region.

Genome plasticity favours double chromosomal Tn4401b-blaKPC-2 transposon insertion in the Pseudomonas aeruginosa ST235 clone

BACKGROUND

Pseudomonas aeruginosa Sequence Type 235 is a clone that possesses an extraordinary ability to acquire mobile genetic elements and has been associated with the spread of resistance genes, including genes that encode for carbapenemases. Here, we aim to characterize the genetic platforms involved in resistance dissemination in blaKPC-2-positive P. aeruginosa ST235 in Colombia.

RESULTS

In a prospective surveillance study of infections in adult patients attended in five ICUs in five distant cities in Colombia, 58 isolates of P. aeruginosa were recovered, of which, 27 (46.6%) were resistant to carbapenems. The molecular analysis showed that 6 (22.2%) and 4 (14.8%) isolates harboured the blaVIM and blaKPC-2 genes, respectively. The four blaKPC-2-positive isolates showed a similar PFGE pulsotype and belonged to ST235. Complete genome sequencing of a representative ST235 isolate shows a unique chromosomal contig of 7097.241 bp with eight different resistance genes identified and five transposons: a Tn6162-like with ant(2″)-Ia, two Tn402-like with ant(3″)-Ia and blaOXA-2 and two Tn4401b with blaKPC-2. All transposons were inserted into the genomic islands. Interestingly, the two Tn4401b copies harbouring blaKPC-2 were adjacently inserted into a new genomic island (PAGI-17) with traces of a replicative transposition process. This double insertion was probably driven by several structural changes within the chromosomal region containing PAGI-17 in the ST235 background.

CONCLUSION

This is the first report of a double Tn4401b chromosomal insertion in P. aeruginosa, just within a new genomic island (PAGI-17). This finding indicates once again the great genomic plasticity of this microorganism.

Molecular analysis of Pseudomonas aeruginosa isolated from clinical, environmental and cockroach sources by ERIC-PCR

OBJECTIVE

The objective of this study was to investigate the antibiotic susceptibility, virulence factors and clonal relationship among Pseudomonas aeruginosa isolated from environmental sources, hospitalized patients and the surfaces of cockroaches in the ICUs of four hospitals in Hamadan, west of Iran. A total of 237, 286 and 156 bacterial isolates were collected from clinical, environmental and cockroach sources respectively from May to September, 2017. The antimicrobial susceptibility was determined using disk diffusion method. The virulence factors, exotoxins A, S and U were detected by PCR. The genetic linkage of P. aeruginosa isolates were analyzed by Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR.

RESULTS

According to our findings, 58 (24.4%), 46 (16%) and 5 (3.25) P. aeruginosa were isolated from clinical, environmental and cockroach samples respectively. The MDR phenotypes were detected in 18 (45%) and 15 (37.5%) of clinical and environmental strains. The environmental isolates harbored more exoA and exoS than did clinical isolates. Genetic diversity was established among P. aeruginosa isolates as 14 different ERIC fingerprints were detected. The clonal relationships was detected among clinical, environmental and cockroach isolates. Our results highlighted the importance of identifying and controlling the potential sources of P. aeruginosa infections in hospitals.