Gram-Negative Bacterial Resistance: Evolving Patterns and Treatment Paradigms

Antimicrobial-Resistant Bacteria and Prescription of Antibiotics at a Tertiary Care Hospital in Riyadh, Saudi Arabia

Purpose The purpose of the study was to assess the bacterial resistance and annual antibiotic consumption at a tertiary care hospital in Riyadh, Saudi Arabia over a two-year period. Methods This retrospective cohort study was conducted at a tertiary care hospital in Riyadh, Saudi Arabia from January 1, 2016, to December 31, 2017. Results The results showed that there was no significant difference between 2016 and 2017 data regarding patient characteristics like bed occupancy rate, the average length of stay, and the number of admissions; the same was true for bacterial characteristics like the number of bacteria, percentage of isolates in the group, and multidrug resistance (MDR) percentage (p: >0.05). Between 2016 and 2017, there was a slight reduction in the sensitivity of Escherichia​​​ coli (E. coli) carbapenem-resistant Enterobacteriaceae (CRE) (97%, 86%) and Klebsiella pneumoniae (K. pneumoniae) CRE (80%, 76%) towards colistin. There was also a decrease in the sensitivity of Acinetobacter baumannii (A. baumannii) multidrug-resistant organism (MDRO) from 42% to 29% against tigecycline, but an increase in the sensitivity of K. pneumoniae CRE (33%, 50%) and E. coli CRE (76%, 82%). The percentage of MDR strains in gram-positive bacteria showed that more than half of Staphylococcus aureus (S. aureus) were methicillin-resistant (61%, 59%) in 2016 and 2017 respectively. There was a reduction in the percentage of MDR strains in some gram-negative bacteria like Pseudomonas aeruginosa (P. aeruginosa) MDRO (24%, 19%),E. coli extended-spectrum beta-lactamases (ESBL) (56%, 50%), E. coli CRE (4%, 1%), K. pneumoniae CRE (49%, 33%), A. baumannii CRE (90%, 76%), and Proteus mirabilis​​​​​​​ (P. mirabilis) ESBL (54%, 50%). Conclusion MDRO bacteria are very common in the hospital where the study was conducted. Immediate action is required to tackle this problem.

Development and Validation of a Model to Predict Growth of Potentially Antibiotic-Resistant Gram-Negative Bacilli in Critically Ill Children With Suspected Infection

Background

Risk-based guidelines aid empiric antibiotic selection for critically ill adults with suspected infection with Gram-negative bacilli with high potential for antibiotic resistance (termed high-risk GNRs). Neither evidence-based guidelines for empiric antibiotic selection nor validated risk factors predicting high-risk GNR growth exist for critically ill children. We developed and validated a model for predicting high-risk GNR growth in critically ill children with suspected infection.

Methods

This is a retrospective cohort study involving 2 pediatric cohorts admitted to a pediatric intensive care unit (ICU) with suspected infection. We developed a risk model predicting growth of high-risk GNRs using multivariable regression analysis in 1 cohort and validated it in a separate cohort.

Results

In our derivation cohort (556 infectious episodes involving 489 patients), we identified the following independent predictors of high-risk GNR growth: hospitalization >48 hours before suspected infection, hospitalization within the past 4 weeks, recent systemic antibiotics, chronic lung disease, residence in a chronic care facility, and prior high-risk GNR growth. The model sensitivity was 96%, the specificity was 48%, performance using the Brier score was good, and the area under the receiver operator characteristic curve (AUROC) was 0.722, indicating good model performance. In our validation cohort (525 episodes in 447 patients), model performance was similar (AUROC, 0.733), indicating stable model performance.

Conclusions

Our model predicting high-risk GNR growth in critically ill children demonstrates the high sensitivity needed for ICU antibiotic decisions, good overall predictive capability, and stable performance in 2 separate cohorts. This model could be used to develop risk-based empiric antibiotic guidelines for the pediatric ICU.

Influence of agricultural practice on mobile bla genes: IncI1-bearing CTX-M, SHV, CMY and TEM in Escherichia coli from intensive farming soils

Many calls have been made to address antibiotic resistance in an environmental perspective. With this study, we showed the widespread presence of high-level antibiotic resistant isolates on a collection of non-susceptible Gram-negative bacteria (n = 232) recovered from soils. Bacteria were selected using amoxicillin, cefotaxime and imipenem, from sites representing different agricultural practices (extensive, intensive and organic). Striking levels of non-susceptibility were noticed in intensive soils for norfloxacin (74%), streptomycin (50.7%) and tetracycline (46.6%); indeed, the exposure to intensive agricultural practices constituted a risk factor for non-susceptibility to many antibiotics, multidrug resistance and production of extended-spectrum β-lactamases (ESBL). Analyses of non-susceptibility highlighted that environmental and clinical bacteria from the same species might not share the same intrinsic resistance patterns, raising concerns for therapy choices in environment-borne infections. The multiple sequence-type IncI1-driven spread of penicillinases (blaTEM-1, blaTEM-135), ESBL (blaSHV-12 and blaCTX-M-1) and plasmid-mediated AmpC β-lactamases (blaCMY-2), produced by isolates that share their molecular features with isolates from humans and animals, suggests contamination of agricultural soils. This is also the first appearance of IncI1/ST28-harbouring blaCTX-M-1, which should be monitored to prevent their establishment as successfully dispersed plasmids. This research may help disclose paths of contamination by mobile antibiotic resistance determinants and the risks for their dissemination.

Significant publications on infectious diseases pharmacotherapy in 2013

PURPOSE

The most important articles on infectious diseases (ID) pharmacotherapy published in the peer-reviewed literature in 2013, as nominated and selected by panels of pharmacists and others with ID expertise, are summarized.

SUMMARY

Members of the Houston Infectious Diseases Network were asked to nominate articles published last year in prominent biomedical journals that had a major impact in the field of ID pharmacotherapy. A list of 27 nominated articles on ID-related topics in general and 26 articles specifically focused on human immunodeficiency virus (HIV) infection or acquired immunodeficiency syndrome (AIDS) was compiled. In a national online survey conducted in January 2014, members of the Society of Infectious Diseases Pharmacists (SIDP) were asked to select from the list those articles that they felt had made the greatest contributions to the field of ID pharmacotherapy. Of 168 SIDP members surveyed, 108 (64%) and 53 (32%) participated in the selection of ID- and HIV/AIDS-related articles, respectively. Summaries of the top-ranked articles in both categories are presented.

CONCLUSION

Major topics explored in the top-ranked ID articles of 2013 include the use of cefepime for gram-negative infections due to AmpC or extended-spectrum β-lactamase-producing Enterobacteriaceae, optimizing antibiotic therapy through the use of extended- or continuous-infusion regimens, the use of the oral integrase inhibitor dolutegravir to combat HIV disease, and new approaches to treatment of Clostridium difficile infection and enterococcal endocarditis.

Prevalence, plasmids and antibiotic resistance correlation of enteric bacteria in different drinking water resources in sohag, egypt

Background:

One of the major health causing problems is contamination of drinking water sources with human pathogenic bacteria. Enteric bacteria such as Shigella, Salmonella and Escherichia coli are most enteric bacteria causing serious health problems. Occurrence of such bacteria infection, which may resist antibiotics, increases the seriousness of problem.

Objectives:

The aim of this study was to examine the prevalence of some enteric bacteria (Shigella, Salmonella and E. coli) in addition to Pseudomonas. The antibiotic susceptibility of these bacteria was also tested, in addition to assessing plasmid(s) roles in supposed resistance. MRSA genes in non-staphylococci were clarified.

Materials and Methods:

Water samples were collected from different drinking sources (Nile, ground water) and treated tap water. Selective media were used to isolate enteric bacteria and Pseudomonas. These bacteria were identified, counted and examined for its susceptibility against 10 antibiotics. The plasmids were screened in these strains. MRSA genes were also examined using PCR.

Results:

Thirty-two bacterial strains were isolated from Nile and ground water and identified as S. flexneri, S. sonnei, S. serovar Newport, Pseudomonas aeruginosa and E. coli strains according to standard methods. According to antibiotic susceptibility test, 81% of strains were resistant to Cefepime, whereas 93.75% were sensitive to Ciprofloxacin. Correlation analysis between plasmids profiles and antibiotics sensitivities showed that 50% of the total strains had plasmids. These strains showed resistance to 50% of the used antibiotics (as average value); whereas, the plasmids free strains (50%) were resistant to 48.7% of the antibiotics. No distinct correlation between plasmids and antibiotic resistance in some strains could be concluded in this study. No MRSA gene was detected among these non-staphylococci strains. No bacteria were isolated from treated tap water.

Conclusions:

Thirty-three bacterial strains; 10 strains of E. coli, 10 strains of S. flexneri, 3 strains S. sonnei, 2 strains of S. serovar Newport, and 7 strains of P. aeruginosa, were isolated and identified from Nile water and ground water in Sohag governorate. The prevalence of enteric bacteria in water sources in studying area was considerable. No clear or distinct correlation could be concluded between plasmids and antibiotic resistance. No MRSA gene was detected in these non-staphylococci strains, and no pathogenic bacteria were isolated from treated tap water. The hygiene procedures in the studying area seem to be adequate, despite the failure to maintain water sources form sewage pollution.

Inhibitors of fatty acid synthesis in prokaryotes and eukaryotes as anti-infective, anticancer and anti-obesity drugs

There is a large range of diseases, such diabetes and cancer, which are connected to abnormal fatty acid metabolism in human cells. Therefore, inhibitors of human fatty acid synthase have great potential to manage or treat these diseases. In prokaryotes, fatty acid synthesis is important for signaling, as well as providing starting materials for the synthesis of phospholipids, which are required for the formation of the cell membrane. Recently, there has been renewed interest in the development of new molecules that target bacterial fatty acid synthases for the treatment of bacterial diseases. In this review, we look at the differences and similarities between fatty acid synthesis in humans and bacteria and highlight various small molecules that have been shown to inhibit either the mammalian or bacterial fatty acid synthase or both.

In vitro synergism of beta-lactams with ciprofloxacin and moxifloxacin against genetically distinct multidrug-resistant isolates of Pseudomonas aeruginosa

In vitro combinations of beta-lactams with fluoroquinolones against multidrug-resistant (MDR) Pseudomonas aeruginosa were tested. From a total of 200 isolates, 24 genetically distinct isolates defined by pulsed-field gel electrophoresis (PFGE) were selected. The isolates were exposed over time to imipenem, meropenem and ceftazidime as well as to their combinations with ciprofloxacin and moxifloxacin. All isolates were resistant to all agents tested at concentrations equal to their average serum level. Synergy of any of the tested combinations was found in 10 isolates (41.7%). This was shown after 4h and 6h of exposure accompanied by re-growth after 24h. Not all the tested combinations were active against the same isolates. The combinations of imipenem+ciprofloxacin, ceftazidime+ciprofloxacin and imipenem+moxifloxacin were the most active. When time-kill assays were repeated for the latter isolates at antimicrobial concentrations equal to their maximum serum levels, synergy was prolonged to 24h. The present findings should be interpreted with caution for the management of infections by MDR P. aeruginosa. They underscore the potential interest of reporting synergism between beta-lactams and fluoroquinolones in the nosocomial setting when a MDR isolate emerges.

Direct E-test (AB Biodisk) of respiratory samples improves antimicrobial use in ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia is the most frequently observed nosocomial infection in intensive care units, and it is associated with high morbidity and mortality. Early microbiological diagnosis and the initial administration of appropriate antimicrobial therapy are associated with decreased mortality and potentially reduced costs. Our study evaluates the clinical and financial impact of performing rapid antimicrobial susceptibility tests directly on samples obtained from the lower respiratory tract.

METHODS

A prospective, randomized study was performed over a 2-year period. Patients who had a lower respiratory tract infection that was acquired during mechanical ventilation and for whom samples obtained from the respiratory tract were sent for culture were randomized to 1 of 2 groups. Samples were cultured for the control group, and results were reported using standard procedures. Samples were also cultured for the test subject group using standard procedures, but in addition, a rapid antibiogram was immediately performed by placing E-test antibiotic strips (AB Biodisk) directly on respiratory tract samples. Patients in the E-test group received a preliminary laboratory report when it became available. The 2 patient groups were compared according to the following variables: type and severity of underlying conditions, total days of antimicrobial use, number of defined daily doses, cost of acquisition of the antimicrobial agent per episode, days of fever, days receiving mechanical ventilation, days in the intensive care unit, incidence of Clostridium difficile-associated diarrhea, and mortality.

RESULTS

Reporting a rapid E-test was associated with fewer days of fever, fewer days of antibiotic administration until resolution of the episode of ventilator-associated pneumonia, decreased antibiotic consumption, less C. difficile-associated diarrhea, lower costs of antimicrobial agents, and fewer days receiving mechanical ventilation.

CONCLUSIONS

A rapid E-test of respiratory tract samples improves antimicrobial use in cases of ventilator-associated pneumonia.

Significance of human β-defensins in the epithelial lining fluid of patients with chronic lower respiratory tract infections

Human beta-defensins (hBDs) are the most abundant antimicrobial peptides in epithelial cells, and function in the host immune system. Respiratory epithelial cells express hBDs to inhibit bacterial proliferation during respiratory tract infections. The aim of this study was to investigate the release of hBDs into the respiratory tract and their benefit as a host defence system in chronic Pseudomonas aeruginosa infections. The levels of four hBD peptides (hBD-1-hBD-4) were measured in the bronchial epithelial lining fluid (ELF) of nine patients with chronic lower respiratory tract infection caused by P. aeruginosa. Eight patients with idiopathic pulmonary fibrosis and eight volunteers free of pulmonary disease were recruited as controls. ELF was obtained by bronchoscopic microsampling and hBD levels were measured by radioimmunoassays. The antimicrobial effects of hBDs were studied individually and in combination using an in-vitro colony count assay for P. aeruginosa. Concentrations of hBD-1 and hBD-3 tended to be higher in patients with chronic lower respiratory tract infection than in the controls. hBD-2 and hBD-4 were detected in ELF from five and four of nine patients, respectively, but the hBD levels in controls were all below the limits of detection. All patients with infection caused by mucoid P. aeruginosa had detectable hBD-2 and hBD-4 levels in ELF. In-vitro colony count assays showed a potential synergism between hBD-2 and hBD-4 in inhibiting bacterial proliferation. The findings indicate that hBDs, especially hBD-2 and hBD-4, are pathophysiologically important in infections caused by mucoid strains of P. aeruginosa.

Proteomic Analysis of the Sarcosine-Insoluble Outer Membrane Fraction ofPseudomonasaeruginosaResponding to Ampicilin, Kanamycin, and Tetracycline Resistance

Nosocomial wound infections by antibiotic-resistant Pseudomonas aeruginosa strains have increasing importance in hospitals. Outer membrane proteins of the bacterium have strong influence on its resistance to antibiotics. In the current study, a parallel proteomic approach was applied to analysis of sarcosine-insoluble outer membrane fraction of P. aeruginosa responding to ampicilin, kanamycin and tetracycline resistances. Eleven differential proteins with 15 spots were determined and then identified by MALDI-TOF/MS, in which four with increased OprF, MexA, OmpH, and decreased hypothetical protein (NCBI No. 15599856), six with increased OprF, OmpH, hypothetical protein (NCBI No. 15599183) and decreased OprG, MexA, conserved hypothetical protein (NCBI No. 15600371), and eight with increased OprF, MexA, OprL, probable Omp (NCBI No. 15599856), probable secretion protein (NCBI No. 15600167), OprD and decreased OprG, conserved hypothetical protein (NCBI No. 15600371) responded to ampicilin, kanamycin, and tetracycline resistances, respectively. With the exception of OprF, the other differential proteins did not show the same behaviors against the three antibiotic resistances. Compared with our previous report on E. coli Omps responding to ampicilin and tetracycline resistances, which was only a protein difference in quality between the two antibiotics, P. aeruginosa showed significant diversity against the three antibiotics. Our findings might provide valuable data for an understanding of antibiotic-resistant difference between different species of bacteria. Meanwhile, these proteins shared by different bacteria or a bacterium against different antibiotics may provide universal targets for the development of new drugs that control antibiotic-resistant bacteria.

Isolation of human beta-defensin-4 in lung tissue and its increase in lower respiratory tract infection

BACKGROUND

Human beta-defensin-4 (hBD-4), a new member of the beta-defensin family, was discovered by an analysis of the genomic sequence. The objective of this study was to clarify hBD-4 expression in human lung tissue, along with the inducible expression in response to infectious stimuli, localization, and antimicrobial activities of hBD-4 peptides. We also investigated the participation of hBD-4 in chronic lower respiratory tract infections (LRTI) by measuring the concentrations of hBD-4 peptides in human bronchial epithelial lining fluid (ELF).

METHODS

The antimicrobial activity of synthetic hBD-4 peptides against E. coli and P. aeruginosa was measured by radial diffusion and colony count assays. We identified hBD-4 in homogenated human lung tissue by reverse-phase high-performance liquid chromatography coupled with a radioimmunoassay (RIA). Localization of hBD-4 was studied through immunohistochemical analysis (IHC). We investigated the effects of lipopolysaccharide (LPS) on hBD-4 expression and its release from small airway epithelial cells (SAEC). We collected ELF from patients with chronic LRTI using bronchoscopic microsampling to measure hBD-4 concentrations by RIA.

RESULTS

hBD-4 exhibited salt-sensitive antimicrobial activity against P. aeruginosa. We detected the presence of hBD-4 peptides in human lung tissue. IHC demonstrated the localization of hBD-4-producing cells in bronchial and bronchiolar epithelium. The levels of hBD-4 peptides released from LPS-treated SAECs were higher than those of untreated control cells. ELF hBD-4 was detectable in 4 of 6 patients with chronic LRTI, while the amounts in controls were all below the detectable level.

CONCLUSION

This study suggested that hBD-4 plays a significant role in the innate immunity of the lower respiratory tract.

Efflux-mediated antimicrobial resistance

Antibiotic resistance continues to plague antimicrobial chemotherapy of infectious disease. And while true biocide resistance is as yet unrealized, in vitro and in vivo episodes of reduced biocide susceptibility are common and the history of antibiotic resistance should not be ignored in the development and use of biocidal agents. Efflux mechanisms of resistance, both drug specific and multidrug, are important determinants of intrinsic and/or acquired resistance to these antimicrobials, with some accommodating both antibiotics and biocides. This latter raises the spectre (as yet generally unrealized) of biocide selection of multiple antibiotic-resistant organisms. Multidrug efflux mechanisms are broadly conserved in bacteria, are almost invariably chromosome-encoded and their expression in many instances results from mutations in regulatory genes. In contrast, drug-specific efflux mechanisms are generally encoded by plasmids and/or other mobile genetic elements (transposons, integrons) that carry additional resistance genes, and so their ready acquisition is compounded by their association with multidrug resistance. While there is some support for the latter efflux systems arising from efflux determinants of self-protection in antibiotic-producing Streptomyces spp. and, thus, intended as drug exporters, increasingly, chromosomal multidrug efflux determinants, at least in Gram-negative bacteria, appear not to be intended as drug exporters but as exporters with, perhaps, a variety of other roles in bacterial cells. Still, given the clinical significance of multidrug (and drug-specific) exporters, efflux must be considered in formulating strategies/approaches to treating drug-resistant infections, both in the development of new agents, for example, less impacted by efflux and in targeting efflux directly with efflux inhibitors.