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Concept: Gram negative bacteria


Routine antimicrobial susceptibility testing (AST) can prevent deaths due to bacteria and reduce the spread of multi-drug-resistance, but cannot be regularly performed in resource-limited-settings due to technological challenges, high-costs, and lack of trained professionals. We demonstrate an automated and cost-effective cellphone-based 96-well microtiter-plate (MTP) reader, capable of performing AST without the need for trained diagnosticians. Our system includes a 3D-printed smartphone attachment that holds and illuminates the MTP using a light-emitting-diode array. An inexpensive optical fiber-array enables the capture of the transmitted light of each well through the smartphone camera. A custom-designed application sends the captured image to a server to automatically determine well-turbidity, with results returned to the smartphone in ~1 minute. We tested this mobile-reader using MTPs prepared with 17 antibiotics targeting Gram-negative bacteria on clinical isolates of Klebsiella pneumoniae, containing highly-resistant antimicrobial profiles. Using 78 patient isolate test-plates, we demonstrated that our mobile-reader meets the FDA-defined AST criteria, with a well-turbidity detection accuracy of 98.21%, minimum-inhibitory-concentration accuracy of 95.12%, and a drug-susceptibility interpretation accuracy of 99.23%, with no very major errors. This mobile-reader could eliminate the need for trained diagnosticians to perform AST, reduce the cost-barrier for routine testing, and assist in spatio-temporal tracking of bacterial resistance.

Concepts: Bacteria, Microbiology, Antibiotic resistance, Escherichia coli, Performance, Microorganism, Gram negative bacteria, Chloramphenicol


Classic drug development strategies have failed to meet the urgent clinical needs in treating infections with Gram-negative bacteria. Repurposing drugs can lead to timely availability of new antibiotics, accelerated by existing safety profiles. Glatiramer acetate (GA) is a widely used and safe formulation for treatment of multiple sclerosis. It contains a large diversity of essentially isomeric polypeptides with the cationic and amphiphilic character of many antimicrobial peptides (AMP). Here, we report that GA is antibacterial, targeting Gram-negative organisms with higher activity towards Pseudomonas aeruginosa than the naturally-occurring AMP LL-37 in human plasma. As judged from flow cytometric assays, bacterial killing by GA occurred within minutes. Laboratory strains of Escherichia coli and P. aeruginosa were killed by a process of condensing intracellular contents. Efficient killing by GA was also demonstrated in Acinetobacter baumannii clinical isolates and approximately 50% of clinical isolates of P. aeruginosa from chronic airway infection in CF patients. By contrast, the Gram-positive Staphylococcus aureus cells appeared to be protected from GA by an increased formation of nm-scale particulates. Our data identify GA as an attractive drug repurposing candidate to treat infections with Gram-negative bacteria.

Concepts: Immune system, Bacteria, Microbiology, Antibiotic resistance, Escherichia coli, Pseudomonas aeruginosa, Gram negative bacteria, Gram-negative bacteria


Colonization and infection by multidrug-resistant gram-negative bacilli (MDR GNB) in neonatal intensive care units (NICUs) are increasingly reported.We conducted a 5-year prospective cohort surveillance study in a tertiary NICU of the hospital “Paolo Giaccone,” Palermo, Italy. Our objectives were to describe incidence and trends of MDR GNB colonization and the characteristics of the most prevalent organisms and to identify the risk factors for colonization. Demographic, clinical, and microbiological data were prospectively collected. Active surveillance cultures (ASCs) were obtained weekly. Clusters of colonization by extended spectrum β-lactamase (ESBL) producing Escherichia coli and Klebsiella pneumoniae were analyzed by conventional and molecular epidemiological tools.During the study period, 1152 infants were enrolled in the study. Prevalences of colonization by MDR GNB, ESBL-producing GNB and multiple species/genera averaged, respectively, 28.8%, 11.7%, and 3.7%. Prevalence and incidence density of colonization by MDR GNB and ESBL-producing GNB showed an upward trend through the surveillance period. Rates of ESBL-producing E coli and K pneumoniae colonization showed wide fluctuations peaking over the last 2 years. The only independent variables associated with colonization by MDR GNB and ESBL-producing organisms and multiple colonization were, respectively, the days of NICU stay (odds ratio [OR] 1.041), the days of exposure to ampicillin-sulbactam (OR 1.040), and the days of formula feeding (OR 1.031). Most clusters of E coli and K pneumoniae colonization were associated with different lineages. Ten out of 12 clusters had an outborn infant as their index case.Our study confirms that MDR GNB are an increasing challenge to NICUs. The universal once-a-week approach allowed us to understand the epidemiology of MDR GNB, to timely detect new clones and institute contact precautions, and to assess risk factors. Collection of these data can be an important tool to optimize antimicrobials use and control the emergence and dissemination of resistances in NICU.

Concepts: Epidemiology, Medical statistics, Intensive care medicine, Escherichia coli, Enterobacteriaceae, Prevalence, Gram negative bacteria, Gram-negative bacteria


The mobile colistin resistance gene mcr-1 has attracted global attention, as it heralds the breach of polymyxins, one of the last-resort antibiotics for the treatment of severe clinical infections caused by multidrug-resistant Gram-negative bacteria. To date, six slightly different variants of mcr-1, and a second mobile colistin resistance gene, mcr-2, have been reported or annotated in the GenBank database. Here, we characterized a third mobile colistin resistance gene, mcr-3 The gene coexisted with 18 additional resistance determinants in the 261-kb IncHI2-type plasmid pWJ1 from porcine Escherichia colimcr-3 showed 45.0% and 47.0% nucleotide sequence identity to mcr-1 and mcr-2, respectively, while the deduced amino acid sequence of MCR-3 showed 99.8 to 100% and 75.6 to 94.8% identity to phosphoethanolamine transferases found in other Enterobacteriaceae species and in 10 Aeromonas species, respectively. pWJ1 was mobilized to an E. coli recipient by conjugation and contained a plasmid backbone similar to those of other mcr-1-carrying plasmids, such as pHNSHP45-2 from the original mcr-1-harboring E. coli strain. Moreover, a truncated transposon element, TnAs2, which was characterized only in Aeromonas salmonicida, was located upstream of mcr-3 in pWJ1. This ΔTnAs2-mcr-3 element was also identified in a shotgun genome sequence of a porcine E. coli isolate from Malaysia, a human Klebsiella pneumoniae isolate from Thailand, and a human Salmonella enterica serovar Typhimurium isolate from the United States. These results suggest the likelihood of a wide dissemination of the novel mobile colistin resistance gene mcr-3 among Enterobacteriaceae and aeromonads; the latter may act as a potential reservoir for mcr-3IMPORTANCE The emergence of the plasmid-mediated colistin resistance gene mcr-1 has attracted substantial attention worldwide. Here, we examined a colistin-resistant Escherichia coli isolate that was negative for both mcr-1 and mcr-2 and discovered a novel mobile colistin resistance gene, mcr-3 The amino acid sequence of MCR-3 aligned closely with phosphoethanolamine transferases from Enterobacteriaceae and Aeromonas species originating from both clinical infections and environmental samples collected in 12 countries on four continents. Due to the ubiquitous profile of aeromonads in the environment and the potential transfer of mcr-3 between Enterobacteriaceae and Aeromonas species, the wide spread of mcr-3 may be largely underestimated. As colistin has been and still is widely used in veterinary medicine and used at increasing frequencies in human medicine, the continuous monitoring of mobile colistin resistance determinants in colistin-resistant Gram-negative bacteria is imperative for understanding and tackling the dissemination of mcr genes in both the agricultural and health care sectors.

Concepts: DNA, Gene, Bacteria, Microbiology, Escherichia coli, Plasmid, Proteobacteria, Gram negative bacteria


A retrospective study was conducted at a Taiwanese medical center to characterize bloodstream infections caused by IMP-8 metallo-β-lactamase (MBL)-producing Enterobacteriaceae isolates and to assess the need for laboratory detection of IMP producers. We analyzed 37 patients infected with IMP-8 producers (two Escherichia coli, nine Klebsiella pneumoniae, 25 Enterobacter cloacae, and one Citrobacter freundii) and 107 patients infected with non-IMP-8 producers (eight E. coli, 26 K. pneumoniae, 70 E. cloacae, and three C. freundii) that were interpreted as carbapenem-nonsusceptible based on the updated Clinical and Laboratory Standards Institute (CLSI) 2010 guidelines. Only 18 (48.6 %) of the IMP-8 producers were regarded as potential carbapenemase producers based on the CLSI 2012 guidelines. The production of extended-spectrum β-lactamases (ESBLs) was more common in the MBL group (73.0 %) than in the non-MBL group (41.1 %). There were no significant differences in carbapenem susceptibilities, clinical characteristics, carbapenem use for empirical and definitive treatment, and mortality rates between the two groups. Eighteen IMP-8 producers could be deemed as resistant to all carbapenems [minimum inhibitory concentration (MIC) of any carbapenem ≥2 μg/mL]; patients with these isolates had a lower, but non-significant, 28-day mortality rate (27.8 %) than patients infected with non-MBL producers having similar carbapenem MICs (39.0 %) (p = 0.41). A multivariate analysis revealed severity of acute illness as the single independent variable associated with both 7-day and 28-day mortality rates (p < 0.01) for infections caused by Enterobacteriaceae with decreased carbapenem susceptibilities. Our findings suggest that the clinical detection of IMP-producing Enterobacteriaceae is not required even when the "old" CLSI criteria are used.

Concepts: Escherichia coli, Phage therapy, Enterobacteriaceae, Escherichia, Gram negative bacteria, Enterobacteria, Klebsiella pneumoniae, Klebsiella


Ceftolozane is a new cephalosporin with potent activity against Pseudomonas aeruginosa and Enterobacteriaceae. The neutropenic murine thigh-infection was used to determine which pharmacokinetic/pharmacodynamic index and magnitude drives efficacy of ceftolozane with gram-negative bacilli, compare the rate of in-vivo killing of ceftolozane with ceftazidime against P. aeruginosa, and determine the impact of different ratios of ceftolozane plus tazobactam on Enterobacteriaceae containing extended-spectrum-β-lactamases (ESBLs). Neutropenic mice had 10(6.2-7.1) cfu/thigh when treated with ceftolozane for 24 h with [1] varying doses (3.12 to 1600 mg/kg) and dosage intervals (3, 6, 12 and 24 h) against 2 Enterobacteriaceae, [2] 0.39-800 mg/kg every 6 h for 4 Enterobacteriaceae and 4 P. aeruginosa, and [3] 400 or 800 mg/kg with 2:1. 4:1, and 8:1 ratios of tazobactam against 5 Enterobacteriaceae with ESBLs. Pharmacokinetics of ceftolozane at 25, 100, and 400 mg/kg was linear with peak/dose values of 1.0-1.4 and half-lives of 12-14 min. T>MIC was the primary index driving efficacy. For stasis (1 log kill), T>MIC was 26.3% ± 2.1 (31.6% ± 1.6) for wild-type Enterobacteriaceae, 31.1% ± 4.9 (34.8% ±4.4) for Enterobacteriaceae with ESBLs, and 24.0% ± 3.3 (31.5% ± 3.9) for P. aeruginosa. At 200 mg/kg every 3 h, the rate of in-vivo killing of P. aeruginosa was faster with ceftolozane than with ceftazidime (-0.34 to -0.41 versus -0.21 to -0.24 log(10) cfu/thigh/h). The 2:1 ratio of ceftolozane with tazobactam was the most potent combination studied. T>MIC required for ceftolozane is less than with other cephalosporins and may be due to more rapid killing.

Concepts: Escherichia coli, Pseudomonas aeruginosa, Pseudomonas, Gram negative bacteria, Beta-lactamase, Pseudomonadales, Cephalosporin, Ceftazidime


The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on its physical surface structure. As such, they provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. Their effectiveness against a wide spectrum of bacteria, however, is yet to be established. Here, the bactericidal properties of the wings were tested against several bacterial species, possessing a range of combinations of morphology and cell wall type. The tested species were primarily pathogens, and included Bacillus subtilis, Branhamella catarrhalis, Escherichia coli, Planococcus maritimus, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Staphylococcus aureus. The wings were found to consistently kill Gram-negative cells (i.e., B. catarrhalis, E. coli, P. aeruginosa, and P. fluorescens), while Gram-positive cells (B. subtilis, P. maritimus, and S. aureus) remained resistant. The morphology of the cells did not appear to play any role in determining cell susceptibility. The bactericidal activity of the wing was also found to be quite efficient; 6.1 ± 1.5 × 10(6) P. aeruginosa cells in suspension were inactivated per square centimeter of wing surface after 30-min incubation. These findings demonstrate the potential for the development of selective bactericidal surfaces incorporating cicada wing nanopatterns into the design.

Concepts: Bacteria, Antibiotic resistance, Escherichia coli, Pseudomonas aeruginosa, Cell wall, Bacillus, Gram negative bacteria, Firmicutes


A methanolic extract of Punica granatum (pomegranate) fruit pericarp (PGME) was tested in combination with ciprofloxacin against extended-spectrum β-lactamase (ESBL) producing Escherichia coli, Klebsiella pneumoniae, and metallo-β-lactamase (MBL) producing Pseudomonas aeruginosa, which were screened for their resistance profile against fluoroquinolone antibiotics. The minimum inhibitory concentrations (MIC) of ciprofloxacin and PGME, alone, were determined, and synergy of ciprofloxacin-PGME combinations evaluated by checkerboard assay and fractional inhibitory concentration (FIC). Nineteen out of forty-nine strains exhibited synergy with ciprofloxacin (FIC of 0.125-0.5 for ciprofloxacin) further verified by agar-well assay. This could be due to the bacterial efflux pump inhibitor (EPI) activity of the polyphenolic constituents of PGME. However, the isolates exhibiting a high level of ciprofloxacin resistance did not respond to ciprofloxacin-PGME combinations, which could be due to target site modification not influenced further by EPI activity of PGME. Again, some strains were sensitive or weakly resistant to ciprofloxacin, which exhibited ‘indifference’ to the combination, probably due to a lack of over-expressed efflux mechanism. Thus, a synergy of a ciprofloxacin-PGME combination was demonstrated for the first time against ESBL- and MBL-producing Gram-negative bacilli, and the efficacy of an existing drug improved with the help of an inexpensive alternative therapy.

Concepts: Bacteria, Antibiotic resistance, Escherichia coli, Enterobacteriaceae, Antibiotic, Fruit, Gram negative bacteria, Pomegranate


Type IV pili are surface organelles essential for pathogenicity of many Gram-negative bacteria. In Neisseria gonorrhoeae, the major subunit of type IV pili, PilE, is a target of its general O-linked glycosylation system. This system modifies a diverse set of periplasmic and extracellular gonococcal proteins with a variable set of glycans. Here we show that expression of a particular hexa-histidine-tagged PilE was associated with growth arrest. By studying intra- and extragenic suppressors, we found that this phenotype was dependent on pilus assembly and retraction. Based on these results, we developed a sensitive tool to identify factors with subtle effects on pilus dynamics. Using this approach, we found that glycan chain length has differential effects on the growth arrest that appears to be mediated at the level of pilin subunit-subunit interactions and bidirectional remodelling of pilin between its membrane-associated and assembled states. Gonococcal pilin glycosylation thus plays both an intracellular role in pilus dynamics and potential extracellular roles mediated through type IV pili. In addition to demonstrating the effect of glycosylation on pilus dynamics, the study provides a new way of identifying factors with less dramatic effects on processes involved in type IV pilus biogenesis.

Concepts: Cell, Bacteria, Microbiology, Escherichia coli, Gram negative bacteria, Pilus, Neisseria gonorrhoeae, Neisseria


Cefiderocol (formerly S-649266) is an investigational siderophore cephalosporin. Iron-depleted cation-adjusted Mueller-Hinton broth (ID-CAMHB) was prepared according to the Clinical and Laboratory Standards Institute (CLSI) protocol and used to perform broth microdilution testing of cefiderocol against a 2014-2015 collection of clinical isolates of gram-negative bacilli from North America (n=4,239) and Europe (n=4,966). The concentration of cefiderocol inhibiting 90% of isolates tested (MIC90) was: 0.5 (North America; n=3,007) and 1 μg/ml (Europe; n=3,080) for all isolates of Enterobacteriaceae; 1 (North America; n=30) and 4 μg/ml (Europe; n=139) for meropenem-non-susceptible (MIC ≥2 μg/ml) isolates of Enterobacteriaceae; 0.5 μg/ml for both North American (n=765) and European (n=765) isolates of Pseudomonas aeruginosa; 0.5 (North America; n=151) and 1 μg/ml (Europe; n=202) for meropenem-non-susceptible (MIC ≥4 μg/ml) isolates of P. aeruginosa; 1 μg/ml for both North American (n=309) and European (n=839) isolates of all Acinetobacter baumannii as well as for both North American (n=173) and European (n=595) isolates of meropenem-non-susceptible A. baumannii; and 0.5 (North America; n=152) and 0.25 μg/ml (Europe; n=276) for isolates of Stenotrophomonas maltophilia MICs to cefiderocol were ≤4 μg/ml for 99.9% (6,078/6,087) of all Enterobacteriaceae, 97.0% (164/169) of meropenem-non-susceptible Enterobacteriaceae, 99.9% (1,529/1,530) of all P. aeruginosa, 100% (353/353) of meropenem-non-susceptible P. aeruginosa, 97.6% (1,120/1,148) of all A. baumannii, 96.9% (744/768) of meropenem-non-susceptible A. baumannii, 100% of isolates of S. maltophilia (428/428) and 93.8% of Burkholderia cepecia (11/12). We conclude that cefiderocol demonstrated potent in vitro activity against a recent collection of clinical isolates of commonly encountered gram-negative bacilli, including carbapenem non-susceptible isolates.

Concepts: United States, Pseudomonas aeruginosa, Pseudomonas, Gram negative bacteria, Pseudomonadales, North America, Gram-negative bacteria, Acinetobacter baumannii