Long-Term Surveillance of Antibiotic Prescriptions and the Prevalence of Antimicrobial Resistance in Non-Fermenting Gram-Negative Bacilli

Characterization of antibiotic and disinfectant susceptibility in biofilm-forming Acinetobacter baumannii: A focus on environmental isolates

The clinical role of Acinetobacter baumannii has been highlighted in numerous infectious syndromes with a high mortality rate, due to the high prevalence of multidrug-resistant (MDR) isolates. The treatment and eradication of this pathogen is hindered by biofilm-formation, providing protection from noxious environmental factors and antimicrobials. The aim of this study was to assess the antibiotic susceptibility, antiseptic susceptibility and biofilm-forming capacity using phenotypic methods in environmental A. baumannii isolates. One hundred and fourteen (n = 114) isolates were collected, originating from various environmental sources and geographical regions. Antimicrobial susceptibility testing was carried out using the disk diffusion method, while antiseptic susceptibility was performed using the agar dilution method. Determination of biofilm-forming capacity was carried out using a microtiter-plate based method. Resistance in environmental A. baumannii isolates were highest for ciprofloxacin (64.03%, n = 73), levofloxacin (62.18%, n = 71) and trimethoprim-sulfamethoxazole (61.40%, n = 70), while lowest for colistin (1.75%, n = 2). Efflux pump overexpression was seen in 48.25% of isolates (n = 55), 49.12% (n = 56) were classified as MDR. 6.14% (n = 7), 9.65% (n = 11), 24.65% (n = 28) and 59.65% (n = 68) of isolates were non-biofilm producers, weak, medium, and strong biofilm producers, respectively. No significant differences were observed between non-MDR vs. MDR isolates regarding their distribution of biofilm-producers (P = 0.655). The MIC ranges for the tested antiseptics were as follows: benzalkonium chloride 16-128 μg mL-1, chlorhexidine digluconate 4-128 μg mL-1, formaldehyde 64-256 μg mL-1 and triclosan 2-16 μg mL-1, respectively. The conscientious use of antiseptics, together with periodic surveillance, is essential to curb the spread of these bacteria, and to maintain current infection prevention capabilities.

Enhanced anti-biofilm activity of the minocycline-and-gallium-nitrate using niosome wrapping against Acinetobacter baumannii in C57/BL6 mouse pneumonia model

Acinetobacter baumannii is a worldwide health issue in terms of its high antibiotic resistance and ability to form biofilms. Nanoparticles (NPs) with high biocompatibility, high penetrating ability, and low medication dose can successfully treat the antibiotic-resistant infections. In this research, the anti-biofilm activity of niosomes containing minocycline and gallium nitrate (GaN) against A. baumannii biofilm was determined. In order to improve their anti-biofilm properties, minocycline and GaN were encapsulated in niosomes as biocompatible drug carriers. The niosomes' size, zeta potential, shape, stability, drug entrapment efficacy, drug release pattern and antibacterial activity were assessed. Several clinical samples were isolated from the lungs of patients hospitalized at Loghman hospital, Tehran, Iran. The biofilm formation of most lethal clinical isolates of A. baumannii was analyzed. The pneumonia model was generated by intranasally administering A. baumannii suspension to anesthetized mice whose immune systems was compromised twice by cyclophosphamide. Lung infection of the mouse with A. baumannii was confirmed using PCR. After treatment, the lungs were excised under sterile conditions and stained with hematoxylin and eosin (H&E) to determine histological symptoms, inflammation and intercellular secretions. The niosomes contained minocycline and GaN had an average size of 230 nm and a zeta potential of -40 mV, respectively. The percentage of drug entrapment and delayed drug release was both high in niosomal formulations. Niosomes containing minocycline and GaN dispersed 1, 3 and 5 day old biofilms. The mice given the combination of two compounds required less time to be treated than the animals given the single medication (minocycline). The minocycline& GaN-loaded niosomes could be considered as promising candidates to treat the infections caused by A. baumannii biofilm.

Relationship between Biofilm-Formation, Phenotypic Virulence Factors and Antibiotic Resistance in Environmental Pseudomonas aeruginosa

The formation of a protective biofilm by Pseudomonas aeruginosa (PA) is one of the hallmarks of their survival both in vivo and in harsh environmental conditions, thus, biofilm-eradication has relevance from therapeutic perspectives and for infection control. The aim of our study was to investigate the possible relationship between antibiotic resistance, biofilm-forming capacity and virulence factors in n = 166 PA isolates of environmental origin. Antimicrobial susceptibility testing and the phenotypic detection of resistance determinants were carried out using standard protocols. The biofilm-forming capacity of PA was tested using a standardized crystal violet microtiter plate-based method. Motility (swimming, swarming, and twitching) and siderophore production of the isolates were also assessed. Resistance rates were highest for ciprofloxacin (46.98%), levofloxacin (45.18%), ceftazidime (31.92%) and cefepime (30.12%); 19.28% of isolates met the criteria to be classified as multidrug-resistant (MDR). Efflux pump overexpression, AmpC overexpression, and modified Hodge-test positivity were noted in 28.31%, 18.07% and 3.61%, respectively. 22.89% of isolates were weak/non-biofilm producers, while 27.71% and 49.40% were moderate and strong biofilm producers, respectively. Based on MDR status of the isolates, no significant differences in biofilm-production were shown among environmental PA (non-MDR OD570 [mean ± SD]: 0.416 ± 0.167 vs. MDR OD570: 0.399 ± 0.192; p > 0.05). No significant association was observed between either motility types in the context of drug resistance or biofilm-forming capacity (p > 0.05). 83.13% of isolates tested were positive for siderophore production. The importance of PA as a pathogen in chronic and healthcare-associated infections has been described extensively, while there is increasing awareness of PA as an environmental agent in agriculture and aquaculture. Additional studies in this field would be an important undertaking to understand the interrelated nature of biofilm production and antimicrobial resistance, as these insights may become relevant bases for developing novel therapeutics and eradication strategies against PA.

Relationship between the Biofilm-Forming Capacity and Antimicrobial Resistance in Clinical Acinetobacter baumannii Isolates: Results from a Laboratory-Based In Vitro Study

The relationship between the multidrug-resistant (MDR) phenotype and biofilm-forming capacity has been a topic of extensive interest among biomedical scientists, as these two factors may have significant influence on the outcomes of infections. The aim of the present study was to establish a possible relationship between biofilm-forming capacity and the antibiotic-resistant phenotype in clinical Acinetobacter baumannii (A. baumannii) isolates. A total of n = 309 isolates were included in this study. Antimicrobial susceptibility testing and the phenotypic detection of resistance determinants were carried out. The capacity of isolates to produce biofilms was assessed using a crystal violet microtiter-plate-based method. Resistance rates were highest for ciprofloxacin (71.19%; n = 220), levofloxacin (n = 68.61%; n = 212), and trimethoprim-sulfamethoxazole (n = 66.02%; n = 209); 42.72% (n = 132) of isolates were classified as MDR; 22.65% (n = 70) of tested isolates were positive in the modified Hodge-test; the overexpression of efflux pumps had significant effects on the susceptibilities of meropenem, gentamicin, and ciprofloxacin in 14.24% (n = 44), 6.05% (n = 19), and 27.51% (n = 85), respectively; 9.39% (n = 29), 12.29% (n = 38), 22.97% (n = 71), and 55.35% (n = 170) of isolates were non-biofilm-producing and weak, moderate, and strong biofilm producers, respectively. A numerical, but statistically not significant, difference was identified between the MDR and non-MDR isolates regarding their biofilm-forming capacity (MDR: 0.495 ± 0.309 vs. non-MDR: 0.545 ± 0.283; p = 0.072), and no association was seen between resistance to individual antibiotics and biofilm formation. Based on numerical trends, MER-resistant isolates were the strongest biofilm producers (p = 0.067). Our study emphasizes the need for additional experiments to assess the role biofilms have in the pathogenesis of A. baumannii infections.

No Correlation between Biofilm Formation, Virulence Factors, and Antibiotic Resistance in Pseudomonas aeruginosa: Results from a Laboratory-Based In Vitro Study

Pseudomonas aeruginosa (P. aeruginosa) possesses a plethora of virulence determinants, including the production of biofilm, pigments, exotoxins, proteases, flagella, and secretion systems. The aim of our present study was to establish the relationship between biofilm-forming capacity, the expression of some important virulence factors, and the multidrug-resistant (MDR) phenotype in P. aeruginosa. A total of three hundred and two (n = 302) isolates were included in this study. Antimicrobial susceptibility testing and phenotypic detection of resistance determinants were carried out; based on these results, isolates were grouped into distinct resistotypes and multiple antibiotic resistance (MAR) indices were calculated. The capacity of isolates to produce biofilm was assessed using a crystal violet microtiter-plate based method. Motility (swimming, swarming, and twitching) and pigment-production (pyoverdine and pyocyanin) were also measured. Pearson correlation coefficients (r) were calculated to determine for antimicrobial resistance, biofilm-formation, and expression of other virulence factors. Resistance rates were the highest for ceftazidime (56.95%; n = 172), levofloxacin (54.97%; n = 166), and ciprofloxacin (54.64%; n = 159), while lowest for colistin (1.66%; n = 5); 44.04% (n = 133) of isolates were classified as MDR. 19.87% (n = 60), 20.86% (n = 63) and 59.27% (n = 179) were classified as weak, moderate, and strong biofilm producers, respectively. With the exception of pyocyanin production (0.371 ± 0.193 vs. non-MDR: 0.319 ± 0.191; p = 0.018), MDR and non-MDR isolates did not show significant differences in expression of virulence factors. Additionally, no relevant correlations were seen between the rate of biofilm formation, pigment production, or motility. Data on interplay between the presence and mechanisms of drug resistance with those of biofilm formation and virulence is crucial to address chronic bacterial infections and to provide strategies for their management.

Survey of the Knowledge and Use of Antibiotics among Medical and Veterinary Health Professionals and Students in Portugal

Antimicrobial resistance (AMR) is an urgent and complex problem worldwide, exacerbated by the frequently inappropriate use of antibiotics. The purpose of this study was to survey the levels of knowledge and awareness about antibiotic use and stewardship, among human and veterinary health professionals or students in Portugal, and the associations between antibiotic knowledge factors and socio-professional groups. In cross-sectional survey design, a total of 449 online structured questionnaires were completed in 2018-2019. The statistical analysis was performed dividing the respondents into four groups, A (undergraduate students), B (PhD students and researchers), C (lecturers), and D (technicians and other occupation). Among all respondents, 17% (n = 75) revealed some gap in knowledge about antibiotic resistance and the antibiotics that should be administered for different infection types (bacterial, viral, or fungal). Of the 159 pet owners among the respondents, only half had administered antibiotics to their animal and 64% (n = 102) knew that veterinary prescription is mandatory when administering antibiotics to animals. All groups statistically agreed that the AMR is a major public health problem and the antibiotics should be administrated for bacterial infections and used until the whole pack has been finished (p = 0.00). As expected, only groups B and C demonstrated a higher level of knowledge to recognize the antibiotic name and their active ingredient than undergraduate students (p = 0.00). About the antibiotic use on pets, only group B was statistically significant to no used antibiotics on their pets (p = 0.00). However, groups A, C, and D were statistically significant for the knowledge about the mandatory veterinarian prescription and groups C and D were significantly statistics for fully aware of the transmission of bacteria between animals and humans. In conclusion, in matters related to AMR, the behavior, education, and training of the general public and health professionals, including those who prescribe antibiotics for humans and animals, need to be improved.

Microbiological profiles and antimicrobial resistance patterns of pediatric bloodstream pathogens in China, 2016-2018

OBJECTIVES

This study aimed to investigate the microbiological profiles and antimicrobial resistance patterns of bloodstream pathogens in Chinese children.

METHODS

This retrospective study was conducted at 13 tertiary hospitals in China during 2016-2018. The first bloodstream isolates of the same species from one pediatric patient < 18 years were included to this study for analysis. Antimicrobial susceptibility testing was determined based on minimum inhibitory concentrations or Kirby-Bauer disk diffusion methods according to the 2018 Clinical and Laboratory Standards Institute guidelines.

RESULTS

Overall, 9345 nonduplicate bloodstream isolates were collected. Top 10 pathogens included Coagulase-negative staphylococcus (CoNS) (44.4%), Escherichia coli (10.2%), Klebsiella pneumoniae (5.9%), Staphylococcus aureus (5.0%), Streptococcus pneumoniae (4.9%), Pseudomonas aeruginosa(2.8%), Enterococcus faecium (2.7%), Stenotrophomonas maltophilia (2.4%), Salmonella spp. (2.3%), and Streptococcus agalactiae (2.0%). The commonest pathogens apart from CoNS in age group 0-28 days, 29 days-2 months, 3-11 months, 1-5 years, and ≥ 5 years were Escherichia coli (17.2%), Escherichia coli (14.0%), Escherichia coli (7.9%), Streptococcus pneumoniae (10.7%) ,and Staphylococcus aureus (13.6%), respectively. The overall prevalence of extended-spectrum β-lactamases-producing Enterobacteriaceae, carbapenem-resistant Klebsiella pneumoniae, carbapenem-resistant Acinetobacter baumannii, and carbapenem-resistant Pseudomonas aeruginosa were 41.4, 28.4, 31.7, and 5.6%, respectively. The overall prevalence of methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae and vancomycin-resistant Enterococcus was 38.1, 28.3, and 0.7%, respectively.

CONCLUSIONS

The major bacterial pathogens have differences in different age groups, ward types, and regions in Chinese children, and the commonest causing microorganism was the Escherichia coli, especially in neonates and infants. High prevalence of important resistant phenotypes is of a serious concern.

Carbapenem-Resistant but Cephalosporin-Susceptible Pseudomonas aeruginosa in Urinary Tract Infections: Opportunity for Colistin Sparing

This paper briefly reports the occurrence and epidemiology of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) Pseudomonas aeruginosa isolates from urinary tract infections (UTIs) in a tertiary-care hospital in the Southern Region of Hungary, and the phenotypic characterization of the possible resistance mechanisms in these isolates. Isolates and data were collected regarding P. aeruginosa UTIs corresponding to the period between 2008 and 2017. Susceptibility testing was performed using the Kirby-Bauer disk diffusion method; minimum inhibitory concentrations (MICs) of the isolates were determined using E-tests. The phenotypic detection of ampicillin C-type (AmpC) β-lactamases, efflux pump overexpression and carbapenemase production was also performed. P. aeruginosa represented n = 575 (2.72% ± 0.64%) from outpatient, and n = 1045 (5.43% ± 0.81%) from inpatient urinary samples, respectively. Based on the disk diffusion test, n = 359 (22.16%) were carbapenem-resistant; in addition to carbapenems, n = (64.34%) were also resistant to ciprofloxacin; n = (60.17%) to gentamicin/tobramycin; n = (58.51%) to levofloxacin; and n = (27.57%) to amikacin. From among the carbapenem-resistant isolates, n = 56 (15.59%) isolates were multidrug-resistant, while n = 16 (4.46%) were extensively drug-resistant. From among the Car-R/Ceph-S isolates (n = 57), overexpression of AmpC was observed in n = 7 cases (12.28%); carbapenemase production in n = 4 (7.02%); while overexpression of efflux pumps was present in n = 31 (54.39%) isolates. To spare last-resort agents, e.g., colistin, the use of broad-spectrum cephalosporins or safe, alternative agents should be considered in these infections.