Resistance profile of genetically distinct clinical Pseudomonas aeruginosa isolates from public hospitals in central Pakistan

Current trends in the epidemiology of multidrug-resistant and beta-lactamase-producing Pseudomonas aeruginosa in Asia and Africa: a systematic review and meta-analysis

Pseudomonas aeruginosa continues to be a significant contributor to high morbidity and mortality rates worldwide, particularly due to its role in severe infections such as hospital-acquired conditions, including ventilator-associated pneumonia and various sepsis syndromes. The global increase in antimicrobial-resistant (AMR) P. aeruginosa strains has made these infections more difficult to treat, by limiting the effective drug options available. This systematic review and meta-analysis aim to provide an updated summary of the prevalence of AMR P. aeruginosa over the past 5 years. A systematic search was performed across three major electronic databases-PubMed, ScienceDirect, and Web of Science-yielding 40 eligible studies published between 2018 and 2023. Using a random-effects model, our meta-analysis estimated that the overall prevalence of P. aeruginosa in Asia and Africa over the past 5 years was 22.9% (95% CI [14.4-31.4]). The prevalence rates for multidrug-resistant (MDR) and extensively drug-resistant (XDR) P. aeruginosa strains were found to be 46.0% (95% CI [37.1-55.0]) and 19.6% (95% CI [4.3-34.9]), respectively. Furthermore, the prevalence rates of extended-spectrum β-lactamase- and metallo-β-lactamase-producing P. aeruginosa were 33.4% (95% CI [23.6-43.2]) and 16.0% (95% CI [9.8-22.3]), respectively. Notably, resistance rates to β-lactams used for treating pseudomonal infections were alarmingly high, with rates between 84.4% and 100.0% for cephalosporins, and over 40% of P. aeruginosa isolates showed resistance to penicillins. Our analysis identified the lowest resistance rates for last-resort antimicrobials, with 0.3% (95% CI [0.0-1.3]) resistance to polymyxin B and 5.8% (95% CI [1.5-10.2]) to colistin/polymyxin E. The low resistance rates to polymyxins suggest that these antibiotics remain effective against MDR P. aeruginosa. However, the findings also highlight the critical public health threat posed by antimicrobial-resistant P. aeruginosa, particularly concerning β-lactam antibiotics. This underscores the need for effective and carefully planned intervention strategies, including the development of new antibiotics to address the growing challenge of resistance. Developing robust antibiotic treatment protocols is essential for better management and control of pseudomonal infections globally. Therefore, continued research and international collaboration is vital to tackle this escalating public health challenge. This study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO), under registration number CRD42023412839.

Antimicrobial Resistance Profiles of Pseudomonas aeruginosa in the Arabian Gulf Region Over a 12-Year Period (2010-2021)

OBJECTIVES

To evaluate literature from a 12-year period (2010-2021) on the antimicrobial resistance profile of Pseudomonas aeruginosa from the Arabian Gulf countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates).

METHODS

An electronic literature search was conducted for articles on antimicrobial resistance in P. aeruginosa and associated phenotypes, covering the period of 1st January 2010 to 1st December 2021.

RESULTS

Antimicrobial resistance in the Arabian Gulf was highest to meropenem (10.3-45.7%) and lowest to colistin (0.0-0.8%), among the agents tested. Annual data showed that ceftazidime resistance (Kuwait), piperacillin-tazobactam non-susceptibility (Qatar), and aztreonam, imipenem, and meropenem resistance (Saudi Arabia) increased by 12-17%. Multiple mechanisms of carbapenem resistance were identified and multiple clones were detected, including high-risk clones such as ST235. The most common carbapenemases detected were the VIM-type metallo-β-lactamases.

CONCLUSIONS

Among P. aeruginosa in the Arabian Gulf countries, resistance to meropenem was higher than to the other agents tested, and meropenem resistance increased in Saudi Arabia during the study period. Resistance to colistin, a classic antibiotic used to treat Pseudomonas spp. infections, remained low. The VIM-type β-lactamase genes were dominant. We recommend local and regional antimicrobial resistance surveillance programs to detect the emergence of resistance genes and to monitor antimicrobial resistance trends in P. aeruginosa.

The association between climatic factors and waterborne infectious outbreaks with a focus on vulnerability in Pakistan: integrative review

Climate change affects the spread of waterborne infectious diseases, yet research on vulnerability to outbreaks remains limited. This integrative review examines how climate variables (temperature and precipitation) relate to human vulnerability factors in Pakistan. By 2060, mean temperatures are projected to rise from 21.68°C (2021) to 30°C, with relatively stable precipitation. The epidemiological investigation in Pakistan identified Diarrhea (119,000 cases/year), Malaria (2.6 million cases/year), and Hepatitis (A and E) as the most prevalent infections. This research highlighted vulnerability factors, including poverty (52% of the population), illiteracy (59% of the population), limited healthcare accessibility (55% of the population), malnutrition (38% of the population), dietary challenges (48% of the population), as well as exposure to water pollution (80% of the population) and air pollution (55% of the population). The findings suggest that the coordinated strategies are vital across health, environmental, meteorological, and social sectors, considering climatic variability patterns and population vulnerability determinants.

In vitro investigation of relationship between quorum-sensing system genes, biofilm forming ability, and drug resistance in clinical isolates of Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is an opportunistic pathogen in the health-care systems and one of the primary causative agents with high mortality in hospitalized patients, particularly immunocompromised. The limitation of effective antibiotic administration in multidrug-resistant and extensively drug-resistant P. aeruginosa isolates leads to the development of nosocomial infections and health problems. Quorum sensing system contributes to biofilm formation, expression of bacterial virulence factors, and development of drug resistance, causing prolonged patient infections. Therefore, due to the significance of the quorum sensing system in increasing the pathogenicity of P. aeruginosa, the primary objective of our study was to investigate the frequency of quorum sensing genes, as well as the biofilm formation and antibiotic resistance pattern among P. aeruginosa strains.

METHODS

A total of 120 P. aeruginosa isolates were collected from different clinical specimens. The disk diffusion method was applied to detect the antibiotic resistance pattern of P. aeruginosa strains. Also, the microtiter plate method was carried out to evaluate the biofilm-forming ability of isolates. Finally, the frequency of rhlI, rhlR, lasI, and lasR genes was examined by the polymerase chain reaction method.

RESULTS

In total, 88.3% P. aeruginosa isolates were found to be multidrug-resistant, of which 30.1% had extensively drug-resistant pattern. The highest and lowest resistance rates were found against ceftazidime (75.0%) and ciprofloxacin (46.6%), respectively. Also, 95.8% of isolates were able to produce biofilm, of which 42.5%, 33.3%, and 20.0% had strong, moderate, and weak biofilm patterns, respectively. The frequency of quorum sensing genes among all examined strains was as follows: rhlI (81.6%), rhlR (90.8%), lasI (89.1%), and lasR (78.3%). The most common type of quorum sensing genes among multidrug-resistant isolates were related to rhlR and lasI genes with 94.3%. Furthermore, rhlI, rhlR, and lasI genes were positive for all extensively drug-resistant isolates. However, the lasR gene had the lowest frequency among both multidrug-resistant (83.0%) and extensively drug-resistant (90.6%) isolates. Moreover, rhlR (94.7%) and lasR (81.7%) genes had the highest and lowest prevalence among biofilm-forming isolates, respectively.

CONCLUSION

Our findings disclosed the significantly high prevalence of drug resistance among P. aeruginosa isolates. Also, the quorum sensing system had a significant correlation with biofilm formation and drug resistance, indicating the essential role of this system in the emergence of nosocomial infections caused by P. aeruginosa.

Molecular Analysis of Carbapenem and Aminoglycoside Resistance Genes in Carbapenem-Resistant Pseudomonas aeruginosa Clinical Strains: A Challenge for Tertiary Care Hospitals

Carbapenem-resistant Pseudomonas aeruginosa (P. aeruginosa) strains have become a global threat due to their remarkable capability to survive and disseminate successfully by the acquisition of resistance genes. As a result, the treatment strategies have been severely compromised. Due to the insufficient available data regarding P. aeruginosa resistance from Pakistan, we aimed to investigate the resistance mechanisms of 249 P. aeruginosa strains by antimicrobial susceptibility testing, polymerase chain reaction for the detection of carbapenemases, aminoglycoside resistance genes, extended-spectrum beta-lactamases (ESBLs), sequence typing and plasmid typing. Furthermore, we tested silver nanoparticles (AgNPs) to evaluate their in vitro sensitivity against antimicrobial-resistant P. aeruginosa strains. We observed higher resistance against antimicrobials in the general surgery ward, general medicine ward and wound samples. Phenotypic carbapenemase-producer strains comprised 80.7% (201/249) with 89.0% (179/201) demonstrating genes encoding carbapenemases: blaNDM-1 (32.96%), blaOXA48 (37.43%), blaIMP (7.26%), blaVIM (5.03%), blaKPC-2 (1.12%), blaNDM-1/blaOXA48 (13.97%), blaOXA-48/blaVIM (1.68%) and blaVIM/blaIMP (0.56%). Aminoglycoside-modifying enzyme genes and 16S rRNA methylase variants were detected in 43.8% (109/249) strains: aac(6')-lb (12.8%), aac(3)-lla (12.0%), rmtB (21.1%), rmtC (11.0%), armA (12.8%), rmtD (4.6%), rmtF (6.4%), rmtB/aac(3)-lla (8.2%), rmtB/aac(6')-lla (7.3%) and rmtB/armA (3.6%). In total, 43.0% (77/179) of the strains coharbored carbapenemases and aminoglycoside resistance genes with 83.1% resistant to at least 1 agent in 3 or more classes and 16.9% resistant to every class of antimicrobials tested. Thirteen sequence types (STs) were identified: ST235, ST277, ST234, ST170, ST381, ST175, ST1455, ST1963, ST313, ST207, ST664, ST357 and ST348. Plasmid replicon types IncFI, IncFII, IncA/C, IncL/M, IncN, IncX, IncR and IncFIIK and MOB types F11, F12, H121, P131 and P3 were detected. Meropenem/AgNPs and Amikacin/AgNPs showed enhanced antibacterial activity. We reported the coexistence of carbapenemases and aminoglycoside resistance genes among carbapenem-resistant P. aeruginosa with diverse clonal lineages from Pakistan. Furthermore, we highlighted AgNP's potential role in handling future antimicrobial resistance concerns.

Prodigiosin as an Antibiofilm Agent against the Bacterial Biofilm-Associated Infection of Pseudomonas aeruginosa

Pseudomonas aeruginosa is known to generate bacterial biofilms that increase antibiotic resistance. With the increase of multi-drug resistance in recent years, the formulation of a new therapeutic strategy has seemed urgent. Preliminary findings show that Prodigiosin (PG), derived from chromium-resistant Serratia marcescens, exhibited efficient anti-biofilm activity against Staphylococcus aureus. However, its anti-biofilm activity against P. aeruginosa remains largely unexplored. The anti-biofilm activity of PG against three clinical single drug-resistant P. aeruginosa was evaluated using crystal violet staining, and the viability of biofilms and planktonic cells were also assessed. A model of chronic lung infection was constructed to test the in vivo antibiofilm activity of PG. The results showed that PG inhibited biofilm formation and effectively inhibited the production of pyocyanin and extracellular polysaccharides in vitro, as well as moderated the expression of interleukins (IL-1β, IL-6, IL-10) and tumor necrosis factor (TNF-α) in vivo, which might be attributed to the downregulation of biofilm-related genes such as algA, pelA, and pslM. These findings suggest that PG could be a potential treatment for drug-resistant P aeruginosa and chronic biofilm infections.

In vitro evaluation of biofilm phenotypic and genotypic characteristics among clinical isolates of Pseudomonas aeruginosa in Hamadan, West of Iran

Due to high antimicrobial resistance and biofilm-forming ability, Pseudomonas aeruginosa is one of the seriously life-threatening agents causing chronic and nosocomial infections. This study was performed to determine the antibiotic resistance pattern, biofilm formation, and frequency of biofilm-related genes in P. aeruginosa strains. In total, 123 P. aeruginosa isolates were collected from different clinical sources. Antimicrobial susceptibility testing (AST) was performed to detect multidrug-resistant P. aeruginosa (MDRPA) isolates. To evaluate the biofilm-forming isolates, the microtiter plate (MTP) method was carried out. Also, the prevalence of biofilm genotype patterns, including pslA, pslD, pelA, pelF, and algD genes, was detected by polymerases chain reaction (PCR). According to our findings, the highest resistance and susceptibility rates were found in ceftazidime with 74.7% (n = 92) and ciprofloxacin with 42.2% (n = 52), respectively. In our study, the highest level of antibiotic resistance belonged to wound isolates which meropenem had the most antibacterial activity against them. In total, 86.1% (n = 106) P. aeruginosa isolates were determined as MDRPA, of which 61.3% (n = 65) were able to form strong biofilm. The highest and lowest frequency of biofilm-related genes among biofilm producer isolates belonged to pelF with 82.1% (n = 101) and algD with 55.2% (n = 68), respectively. The findings of the conducted study indicate a significant relationship between MDRPA and biofilm genotypic/phenotypic patterns, suggesting the necessity of a careful surveillance program in hospital settings.

Multi-drug resistant ESKAPE pathogens and the uses of plants as their antimicrobial agents

Infections by ESKAPE (Enterococcus sp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens cause major concern due to their multi-drug resistance (MDR). The ESKAPE pathogens are frequently linked to greater mortality, diseases, and economic burden in healthcare worldwide. Therefore, the use of plants as a natural source of antimicrobial agents provide a solution as they are easily available and safe to use. These natural drugs can also be enhanced by incorporating silver nanoparticles and combining them with existing antibiotics. By focussing the attention on the ESKAPE organisms, the MDR issue can be addressed much better.

Estimation, Evaluation and Characterization of Carbapenem Resistance Burden from a Tertiary Care Hospital, Pakistan

Carbapenem resistance has become major concern in healthcare settings globally; therefore, its monitoring is crucial for intervention efforts to halt resistance spread. During May 2019–April 2022, 2170 clinical strains were characterized for antimicrobial susceptibility, resistance genes, replicon and sequence types. Overall, 42.1% isolates were carbapenem-resistant, and significantly associated with Klebsiella pneumoniae (K. pneumoniae) (p = 0.008) and Proteus species (p = 0.043). Carbapenemases were detected in 82.2% of isolates, with blaNDM-1 (41.1%) associated with the ICU (p < 0.001), cardiology (p = 0.042), pediatric medicine (p = 0.013) and wound samples (p = 0.041); blaOXA-48 (32.6%) was associated with the ICU (p < 0.001), cardiology (p = 0.008), pediatric medicine (p < 0.001), general surgery (p = 0.001), general medicine (p = 0.005) and nephrology (p = 0.020); blaKPC-2 (5.5%) was associated with general surgery (p = 0.029); blaNDM-1/blaOXA-48 (11.4%) was associated with general surgery (p < 0.001), and wound (p = 0.002), urine (p = 0.003) and blood (p = 0.012) samples; blaOXA-48/blaVIM (3.1%) was associated with nephrology (p < 0.001) and urine samples (p < 0.001). Other detected carbapenemases were blaVIM (3.0%), blaIMP (2.7%), blaOXA-48/blaIMP (0.1%) and blaVIM/blaIMP (0.3%). Sequence type (ST)147 (39.7%) represented the most common sequence type identified among K. pneumoniae, along with ST11 (23.0%), ST14 (15.4%), ST258 (10.9%) and ST340 (9.6%) while ST405 comprised 34.5% of Escherichia coli (E. coli) isolates followed by ST131 (21.2%), ST101 (19.7%), ST10 (16.0%) and ST69 (7.4%). Plasmid replicon types IncFII, IncA/C, IncN, IncL/M, IncFIIA and IncFIIK were observed. This is first report describing the carbapenem-resistance burden and emergence of blaKPC-2-ST147, blaNDM-1-ST340 and blaNDM-1-ST14 in K. pneumoniae isolates and blaNDM-1-ST69 and blaNDM-1/blaOXA-48-ST69 in E. coli isolates coharboring extended-spectrum beta-lactamases (ESBLs) from Pakistan.

Evaluation of toxin-antitoxin genes, antibiotic resistance, and virulence genes in Pseudomonas aeruginosa isolates

OBJECTIVE

Toxin-antitoxin genes RelBE and HigBA are known to be involved in the formation of biofilm, which is an important virulence factor for Pseudomonas aeruginosa. The purpose of this study was to determine the presence of toxin-antitoxin genes and exoenzyme S and exotoxin A virulence genes in P. aeruginosa isolates and whether there is a relationship between toxin-antitoxin genes and virulence genes as well as antibiotic resistance.

METHODS

Identification of the isolates and antibiotic susceptibilities was determined by a VITEK 2 (bioMérieux, France) automated system. The presence of toxin-antitoxin genes, virulence genes, and transcription levels were detected by real-time polymerase chain reaction.

RESULTS

RelBE and HigBA genes were detected in 94.3% (82/87) of P. aeruginosa isolates, and exoenzyme S and exotoxin A genes were detected in all of the isolates (n=87). All of the isolates that harbor the toxin-antitoxin and virulence genes were transcribed. There was a significant increase in the RelBE gene transcription level in imipenem- and meropenem-sensitive isolates and in the HigBA gene transcription level in amikacin-sensitive isolates (p<0.05). There was a significant correlation between RelBE and exoenzyme S (p=0.001).

CONCLUSION

The findings suggest that antibiotic resistance may be linked to toxin-antitoxin genes. Furthermore, the relationship between RelBE and exoenzyme S indicates that toxin-antitoxin genes in P. aeruginosa isolates are not only related to antibiotic resistance but also play an influential role in bacterial virulence. Larger collections of comprehensive studies on this subject are required. These studies should contribute significantly to the solution of the antibiotic resistance problem.

Risk Factors of Clonally Related, Multi, and Extensively Drug-Resistant Acinetobacter baumannii in Severely Ill COVID-19 Patients

Background

The secondary infection of multi and extensively drug-resistant "Acinetobacter baumannii" in severely ill COVID-19 individuals is usually associated with extended hospitalisation and a high mortality rate. The current study aimed to assess the exact incidence rate of A. baumannii coinfection in severely ill COVID-19 patients admitted to intensive care unit (ICUs), to identify the possible mechanism of A. baumannii transfer to COVID-19 patients and to find out their resistance rate against different antibiotics.

Methods

Fifty severely ill "COVID-19" individuals on respiratory support were selected with samples being collected from the pharynx. In addition, another 60 samples were collected from the surrounding environment. Bacterial isolates were diagnosed by microbiological cultures and confirmed by "Vitek 2 system" and real-time PCR. The "Vitek 2 Compact system" was used to evaluate these isolates for antimicrobial susceptibility. The recovered isolates' DNA fingerprints and genetic similarities were performed using ERIC-PCR.

Results

Twenty-six samples were tested positive for A. baumannii (20 out of 50 samples taken from patients, 40%; 6 out of 60 swabs from a nosocomial setting, 10%). All A. baumannii strains isolated from the nosocomial sites were clonally related (have the same genetic lineage) to some strains isolated from patients. However, the majority of the patients' strains were categorised as belonging to the same genetic lineage. Furthermore, "the multi and extensively drug" resistance patterns were seen in all isolates. In addition, total isolates showed resistance to the most commonly tested antibiotics, while none of them was found to be resistant to tigecycline.

Conclusion

Secondary "A. baumannii" infection in severely ill "COVID-19" patients is a serious matter, especially when it has one spot of transmission in the ICU as well as when it is extensively drug-resistant, necessitating an immediate and tactical response to secure the issue.

Molecular Characterization of Gene-Mediated Resistance and Susceptibility of ESKAPE Clinical Isolates to Cistus monspeliensis L. and Cistus salviifolius L. Extracts

Background

Multidrug resistance (MDR) and extensively drug-resistant (XDR) are now the biggest threats to human beings. Alternative antimicrobial regimens to conventional antibiotic paradigms are extensively searched. Although Cistus extracts have long been used for infections in traditional folk medicines around the world, their efficacy against resistant bacteria still needs to be elucidated. We aim to investigate the antibiotic susceptibility profiles of clinical strains Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter cloacae (acronym “ESKAPE”), and their resistance mechanisms by PCR, as well as their sensitivity to C. monspeliensis (CM) and C. salviifolius (CS) methanol extracts and their fractions.

Methods

Antibiotic susceptibility profile and resistance mechanism were done by antibiogram and PCR. Fractions of CM and CS were obtained using maceration and Soxhlet; their antibacterial activities were evaluated by determining inhibition zone diameter (IZD), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC).

Results

Results revealed that all strains were XDR except S. aureus, which was MDR. The PCR indicates the presence of gene-mediated resistance (bla_CTX-M, bla_SHV, bla_OXA-48, bla_NDM, bla_OXA-51, bla_OXA-58, bla_IMP, bla_VIM, and bla_mecA). Also, maceration was slightly better for bioactivity preservation. Overall, the extracts of CM (IZD = 20 mm, MIC = 0.01 mg/mL) were more active than those of CS. All extracts inhibited MRSA (methicillin-resistant Staphylococcus aureus) and ERV (Enterococcus faecium Vancomycin-Resistant) with interesting MICs. The ethyl acetate fraction manifested great efficacy against all strains. Monoterpene hydrocarbons and sesquiterpenes oxygenated were the chemical classes of compounds dominating the analyzed fractions. Viridiflorol was the major compound in ethyl acetate fractions of 59.84% and 70.77% for CM and CS, respectively.

Conclusions

The superior activity of extracts to conventional antibiotics was seen for the first time in the pathogens group, and their bactericidal effect could be a promising alternative for developing clinical antibacterial agents against MDR and XDR ESKAPE bacteria.

Molecular characterization and antibiogram of the carbapenemase gene variants in clinical strains of Pseudomonas aeruginosa

BACKGROUND

Carbapenemase-producing Pseudomonas aeruginosa (CPPA) is a substantial clinical concern because it jeopardizes therapeutic choices. This study characterizes the gene variants of CPPA and report its antibiogram.

METHODS

CPPA was isolated prospectively from diverse clinical sources in a tertiary care setting using a routine microbiological approach. Carbapenem-resistant P. aeruginosa strains were phenotypically identified using the modified carbapenem inactivation (mCIM) method. Minimum inhibitory concentration (MIC) breakpoints of several antibacterial drug groups were determined using broth microdilution methods and the MicroScan WalkAway plus system. Carbapenemase gene variants bla_NDM, bla_VIM, bla_OXA,bla_GES, and bla_IMP were amplified using polymerase chain reaction (PCR), and the purified gene products were sequenced.

RESULTS

Seventy-one P. aeruginosa-infected cases were found, with 47 (66.2%) carrying CPPA; 46.8% of the latter were significantly associated with intensive care units (p = 0.03). CPPA was frequently detected in wound swabs (13; 27.7%), sputum (11; 23.4%), and blood (9; 19.1%). All strains were multidrug-resistant (MDR), and several were extensively drug-resistant. MIC₅₀ and MIC₉₀ breakpoints of all antibiotics, except colistin, were within the resistance range. MIC₉₀ breakpoints of aztreonam, amikacin, cefepime, and piperacillin-tazobactam were > 512 µg/mL. The multiple antibiotic resistance index (MARI) was remarkably high, with a range of 0.38-0.92. The most commonly detected carbapenemase genes were bla_VIM (74%), bla_NDM-1 (19%), bla_OXA-23 (14.9%), and bla_GES (10.6%), while 12 of 47 strains co-harbored different combinations of carbapenemase gene variants.

CONCLUSION

A large proportion of CPPA strains carried the bla_VIM gene variant, indicating intimidating health problems and emphasizing the need for extensive surveillance and antibiotic stewardship.

Genomic Surveillance of Clinical Pseudomonas aeruginosa Isolates Reveals an Additive Effect of Carbapenemase Production on Carbapenem Resistance

Carbapenem resistance in Pseudomonas aeruginosa is increasing globally, and surveillance to define the mechanisms of such resistance in low- and middle-income countries is limited. This study establishes the genotypic mechanisms of β-lactam resistance by whole-genome sequencing (WGS) in 142 P. aeruginosa clinical isolates recovered from three hospitals in Islamabad and Rawalpindi, Pakistan between 2016 and 2017. Isolates were subjected to antimicrobial susceptibility testing (AST) by Kirby-Bauer disk diffusion, and their genomes were assembled from Illumina sequencing data. β-lactam resistance was high, with 46% of isolates resistant to piperacillin-tazobactam, 42% to cefepime, 48% to ceftolozane-tazobactam, and 65% to at least one carbapenem. Twenty-two percent of isolates were resistant to all β-lactams tested. WGS revealed that carbapenem resistance was associated with the acquisition of metallo-β-lactamases (MBLs) or extended-spectrum β-lactamases (ESBLs) in the blaGES, blaVIM, and blaNDM families, and mutations in the porin gene oprD. These resistance determinants were found in globally distributed lineages, including ST235 and ST664, as well as multiple novel STs which have been described in a separate investigation. Analysis of AST results revealed that acquisition of MBLs/ESBLs on top of porin mutations had an additive effect on imipenem resistance, suggesting that there is a selective benefit for clinical isolates to encode multiple resistance determinants to the same drugs. The strong association of these resistance determinants with phylogenetic background displays the utility of WGS for monitoring carbapenem resistance in P. aeruginosa, while the presence of these determinants throughout the phylogenetic tree shows that knowledge of the local epidemiology is crucial for guiding potential treatment of multidrug-resistant P. aeruginosa infections. IMPORTANCE Pseudomonas aeruginosa is associated with serious infections, and treatment can be challenging. Because of this, carbapenems and β-lactam/β-lactamase inhibitor combinations have become critical tools in treating multidrug-resistant (MDR) P. aeruginosa infections, but increasing resistance threatens their efficacy. Here, we used WGS to study the genotypic and phylogenomic patterns of 142 P. aeruginosa isolates from the Potohar region of Pakistan. We sequenced both MDR and antimicrobial susceptible isolates and found that while genotypic and phenotypic patterns of antibiotic resistance correlated with phylogenomic background, populations of MDR P. aeruginosa were found in all major phylogroups. We also found that isolates possessing multiple resistance mechanisms had significantly higher levels of imipenem resistance compared to the isolates with a single resistance mechanism. This study demonstrates the utility of WGS for monitoring patterns of antibiotic resistance in P. aeruginosa and potentially guiding treatment choices based on the local spread of β-lactamase genes.

Class 1, 2 and 3 integrons in clinical Pseudomonas aeruginosa isolated from Tanta University Hospitals, Egypt

Pseudomonas aeruginosa has become a significant health threat, as it has developed resistance to multiple antimicrobial drugs. In this study, we aimed to identify class 1, 2 and 3 integrons in clinical P. aeruginosa isolates for the first time in Egypt, and detect their relationship with antibiotic resistance. A total of 192 clinical P. aeruginosa isolates were gathered from Tanta University Hospitals. One hundred and thirteen isolates (58.9%) were multidrug- resistant, and 38 isolates (19.8%) were resistant to all drugs tested. Class 1 integrons were detected in 87 isolates (45.3%), while class 2 and 3 integrons were not detected. This is the first report of a profile of integrons in P. aeruginosa from Egypt. The detection of only class 1 integrons in our isolates suggests that other genetic elements may be responsible for the distribution of antibiotic resistance in our setting. Aztreonam and colistin were the drugs of choice for the treatment of infections with P. aeruginosa.

Does Conjugation of Silver Nanoparticles with Thiosemicarbazide Increase Their Antibacterial Properties?

The opportunistic pathogen, Pseudomonas aeruginosa, uses different mechanisms as well as biofilm production to acquire antibiotic resistance. The polysaccharide synthesis locus (psl) genes play an important role in P. aeruginosa biofilm formation. Therefore, targeting the expression of psl genes can be a suitable strategy to prevent the formation of biofilms by antibiotic-resistant strains. Today, advances in nanotechnology provide a novel potential strategy to combat antibiotic-resistant bacteria. In this study, the silver nanoparticles (Ag NPs) synthesized using a chemical co-precipitation method and, after conjugation with thiosemicarbazide, their effect on the biofilm-forming ability are studied in P. aeruginosa isolates. Chemical properties of synthesized nanoparticles were determined by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, ultraviolet-visible spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy. The results confirmed the spherical/cubic morphology, solution stability, and good dispersion of Ag@Glu-TSC NPs with an average size of 40-60 nm. In addition, minimum inhibitory concentration values of functionalized Ag NPs were at least twofold lower than the Ag NPs (alone). The quantitative PCR data analysis showed a decrease in the expression of the pslA gene in the presence of Ag@Glu-TSC NPs, up to 60%, which was associated with a reduction of biofilm formation compared to control. In conclusion, the Ag@Glu-TSC NPs can be considered a new inhibitor of biofilm production in antibiotic-resistant bacteria.

Incidence and Molecular Characterization of Carbapenemase Genes in Association with Multidrug-Resistant Clinical Isolates of Pseudomonas aeruginosa from Tertiary Healthcare Facilities in Southwest Nigeria

Pseudomonas aeruginosa, resistant to multiple antibacterial agents including carbapenems, is of great global public health concern. There is limited data available regarding incidence of Metallo-Beta Lactamase producing P. aeruginosa, their molecular basis of resistance in particular carbapenem resistance and any genetic relatedness among circulating clinical isolates in Southwest Nigeria. Four hundred and thirty P. aeruginosa isolates were collected from seven tertiary care hospitals (predominantly from wound, ear, and urinary tract infections) and verified by PCR targeting oprI and oprL. Antibiotic susceptibility using 16 selected antibiotics and MBL screening was performed. The integrons (class 1, 2 and 3) and carbapenemase genes- bla_GES, bla_NMC-A, bla_BIC-1, bla_SME, bla_IMP, bla_VIM, bla_SPM, bla_NDM, bla_AIM, bla_DIM, bla_SIM, bla_GIM, bla_OXA-48, bla_OXA-58 were detected by PCR and were sequenced. Quantitative real-time polymerase chain reaction was used to quantify expression levels of eight efflux pump genes, ampC cephalosporinase and outer membrane porin, oprD. The isolates were genotyped using Enterobacterial Repetitive Intergenic Consensus sequence Polymerase Chain Reaction (ERIC-PCR). Four hundred and thirty P. aeruginosa isolates were subjected to antibiotic susceptibility testing, revealing that 109 (25.4%) isolates were multidrug-resistant, 47 (10.9%) were extensively drug-resistant and 25 (5.8%) were pandrug-resistant. MBL was seen in 17.0% (73/430) isolates. MBL-encoding genes; bla_VIM-5 and bla_NDM-1 were detected in 86.3% (63/73) isolates, with bla_VIM-5 and bla_NDM-1 in 35.6% (26/73) and 38.4% (28/73), respectively, whereas co-occurrence of bla_VIM-5 and bla_NDM-1 was found in 12.3% (9/73). Forty-one (56.2%) carbapenem-resistant P. aeruginosa strains carried class 1 integrons, while co-occurrence of class 1 and 2 integrons was seen in 12.3%. qPCR results indicated that MexXY-OprM was highly expressed pump in 58.9%, ampC upregulated in 26.0%, while oprD porin was downregulated in 65.8% isolates. ERIC-PCR results suggest that carbapenem-resistant strains exhibit genetic heterogeneity. The high incidence of MBL-encoding genes and integrons in diversified clinical P. aeruginosa from southwestern Nigeria is of great concern. The co-occurrence of bla_VIM-5 and bla_NDM-1 as well as resistance in general manifesting a gradient based on genotypic variation suggests that there is a strong need for efficient surveillance programs and antibiotic stewardship.

Detection of synergistic antimicrobial resistance mechanisms in clinical isolates of Pseudomonas aeruginosa from post-operative wound infections

Infections caused by carbapenem-resistant Pseudomonas aeruginosa are life-threatening due to its synergistic resistance mechanisms resulting in the ineffectiveness of the used antimicrobials. This study aimed to characterize P. aeruginosa isolates for antimicrobial susceptibility, biofilm formation virulence genes, and molecular mechanisms responsible for resistance against various antimicrobials. Out of 700 samples, 91 isolates were confirmed as P. aeruginosa which were further classified into 19 non-multidrug-resistant (non-MDR), 7 multidrug-resistant (MDR), 19 extensively drug-resistant (XDR), and 8 pan drug-resistant (PDR) pulsotypes based on standard Kirby Bauer disc diffusion test and pulse field gel electrophoresis. In M9 minimal media, strong biofilms were formed by the XDR and PDR pulsotypes as compared to the non-MDR pulsotypes. The virulence genes, responsible for the worsening of wounds including LasB, plcH, toxA, and exoU, were detected among all MDR, XDR, and PDR pulsotypes. Carbapenemase activity was phenotypically detected in 45% pulsotypes and the responsible genes were found as bla_GES (100%), bla_VIM (58%), bla_IMP (4%), and bla_NDM (4%). Real-time polymerase chain reaction showed the concomitant use of multiple mechanisms such as oprD under-expression, enhanced efflux pump activity, and ampC overexpression in the resistant isolates. Polymyxin is found as the only class left with more than 80% susceptibility among the isolates which is an alarming situation suggesting appropriate measures to be taken including alternative therapies. KEY POINTS: • Multidrug-resistant P. aeruginosa isolates formed stronger biofilms in minimal media. • Only polymyxin antimicrobial was found effective against MDR P. aeruginosa isolates. • Under-expression of oprD and overexpression of ampC were found in resistant isolates.

Prevalence of multi-drug resistant (MDR) and extensively drug-resistant (XDR) phenotypes of Pseudomonas aeruginosa and Acinetobacter baumannii isolated in clinical samples from Northeast of Iran

OBJECTIVE

Multi and extensively drug-resistant (MDR and XDR), Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii) are two main causative agents of nosocomial infections leading to increased morbidity and mortality. We aim to study the prevalence of MDR and XDR-A. baumannii and P. aeruginosa phenotypes in clinical specimens. We conducted this for 1 year (2017-2018) and isolated bacteria from the clinical samples. Then, XDR and MDR strains were determined by susceptibility testing (disc diffusion).

RESULTS

Out of 3248 clinical samples, A. baumannii and P. aeruginosa strains were detected in 309(9.51%) of them. Susceptibility testing indicated that (16.50%) and (15.53%) of the P. aeruginosa and (74.75%) and (73.13%) of the A. baumannii isolates were screened as the MDR and XDR strains. The frequency of MDR isolates was higher in wound samples 222 (71.8%). This rate in behavioral intensive care unit (BICU) and restoration ward, were 187 (60.5%) and 63 (20.4%). The frequency of XDR isolates in BICU 187 (59.54%), restoration 58(18.77%), and burns 30 (9.70%) were assessed as well. Considering high isolation rates of MDR and XDR of mentioned strains, it is necessary to apply prevention criteria for eradication of the mentioned bacteria from hospital wards.