A convergent evolutionary pathway attenuating cellulose production drives enhanced virulence of some bacteria.

Bacteria adapt to selective pressure in their immediate environment in multiple ways. One mechanism involves the acquisition of independent mutations that disable or modify a key pathway, providing a signature of adaptation via convergent evolution. Extra-intestinal pathogenic Escherichia coli (ExPEC) belonging to sequence type 95 (ST95) represent a global clone frequently associated with severe human infections including acute pyelonephritis, sepsis, and neonatal meningitis. Here, we analysed a publicly available dataset of 613 ST95 genomes and identified a series of loss-of-function mutations that disrupt cellulose production or its modification in 55.3% of strains. We show the inability to produce cellulose significantly enhances ST95 invasive infection in a rat model of neonatal meningitis, leading to the disruption of intestinal barrier integrity in newborn pups and enhanced dissemination to the liver, spleen and brain. Consistent with these observations, disruption of cellulose production in ST95 augmented innate immune signalling and tissue neutrophil infiltration in a mouse model of urinary tract infection. Mutations that disrupt cellulose production were also identified in other virulent ExPEC STs, Shigella and Salmonella, suggesting a correlative association with many Enterobacteriaceae that cause severe human infection. Together, our findings provide an explanation for the emergence of hypervirulent Enterobacteriaceae clones.

Treatment Failure Due to Adaptive Resistance Mechanisms in a Severe and Complicated Bloodstream Infection Due to Elizabethkingia meningoseptica.

Elizabethkingia meningoseptica is an uncommonly encountered multidrug-resistant gram-negative bacterium that causes infections primarily among vulnerable hosts. A true opportunistic pathogen, its ability to cause severe sepsis and complicated infection in selected patients has been noted. Very limited preclinical and clinical data exist with regard to suitable therapeutic options. In this study, we present the case of prolonged bloodstream and central nervous system infection due to E. meningoseptica treated with dose-optimized combination antibiotic therapy, with evidence of microbiological (including development of adaptive resistance mechanisms) and clinical failure.

Rapid fluoroquinolone resistance detection in Pseudomonas aeruginosa using mismatch amplification mutation assay-based real-time PCR.

Background. Antimicrobial resistance (AMR) is an ever-increasing global health concern. One crucial facet in tackling the AMR epidemic is earlier and more accurate AMR diagnosis, particularly in the dangerous and highly multi-drug-resistant ESKAPE pathogen, Pseudomonas aeruginosa.Objectives. We aimed to develop two SYBR Green-based mismatch amplification mutation assays (SYBR-MAMAs) targeting GyrA T83I (gyrA248) and GyrA D87N, D87Y and D87H (gyrA259). Together, these variants cause the majority of fluoroquinolone (FQ) AMR in P. aeruginosa.Methods. Following assay validation, the gyrA248 and gyrA259 SYBR-MAMAs were tested on 84 Australian clinical P. aeruginosa isolates, 46 of which demonstrated intermediate/full ciprofloxacin resistance according to antimicrobial susceptibility testing.Results. Our two SYBR-MAMAs correctly predicted an AMR phenotype in the majority (83%) of isolates with intermediate/full FQ resistance. All FQ-sensitive strains were predicted to have a sensitive phenotype. Whole-genome sequencing confirmed 100 % concordance with SYBR-MAMA genotypes.Conclusions. Our GyrA SYBR-MAMAs provide a rapid and cost-effective method for same-day identification of FQ AMR in P. aeruginosa. An additional SYBR-MAMA targeting the GyrB S466Y/S466F variants would increase FQ AMR prediction to 91 %. Clinical implementation of our assays will permit more timely treatment alterations in cases where decreased FQ susceptibility is identified, leading to improved patient outcomes and antimicrobial stewardship.

The Effectiveness of Ultraviolet-C (UV-C) Irradiation on the Viability of Airborne Pseudomonas aeruginosa.

Pseudomonas aeruginosa (Pa) is the predominant bacterial pathogen in people with cystic fibrosis (CF) and can be transmitted by airborne droplet nuclei. Little is known about the ability of ultraviolet band C (UV-C) irradiation to inactivate Pa at doses and conditions relevant to implementation in indoor clinical settings. We assessed the effectiveness of UV-C (265 nm) at up to seven doses on the decay of nebulized Pa aerosols (clonal Pa strain) under a range of experimental conditions. Experiments were done in a 400 L rotating sampling drum. A six-stage Andersen cascade impactor was used to collect aerosols inside the drum and the particle size distribution was characterized by an optical particle counter. UV-C effectiveness was characterized relative to control tests (no UV-C) of the natural decay of Pa. We performed 112 tests in total across all experimental conditions. The addition of UV-C significantly increased the inactivation of Pa compared with natural decay alone at all but one of the UV-C doses assessed. UV-C doses from 246-1968 µW s/cm2 had an estimated effectiveness of approximately 50-90% for airborne Pa. The effectiveness of doses ≥984 µW s/cm2 were not significantly different from each other (p-values: 0.365 to ~1), consistent with a flattening of effectiveness at higher doses. Modelling showed that delivering the highest dose associated with significant improvement in effectiveness (984 µW s/cm2) to the upper air of three clinical rooms would lead to lower room doses from 37-49% of the 8 h occupational limit. Our results suggest that UV-C can expedite the inactivation of nebulized airborne Pa under controlled conditions, at levels that can be delivered safely in occupied settings. These findings need corroboration, but UV-C may have potential applications in locations where people with CF congregate, coupled with other indoor and administrative infection control measures.

Achromobacter Species: An Emerging Cause of Community-Onset Bloodstream Infections.

BACKGROUND: Case reports and small series indicate that Achromobacter species bloodstream infection (BSI) is most commonly a complication of hospitalization among patients with chronic lung disease. The aim of the present study was to determine the incidence, risk factors, and outcomes of Achromobacter sp. BSI in an Australian population. METHODS: Retrospective, laboratory-based surveillance was conducted in Queensland, Australia (population ≈ 5 million) during 2000-2019. Clinical and outcome data were obtained by linkage to state hospital admissions and vital statistics databases. BSI diagnosed within the community or within the first two calendar days of stay in hospital were classified as community-onset. Community-onset BSIs were grouped into community-associated and healthcare-associated. RESULTS: During more than 86 million person-years of surveillance, 210 incidents of Achromobacter sp. BSI occurred among 195 individuals for an overall age-and sex-standardized annual incidence of 2.6 per million residents. Older individuals and males were at highest risk (2.9 vs. 2.0 per million, IRR for males 1.5; 95% CI, 1.1-1.9; p = 0.008). Most (153; 73%) cases were of community-onset of which 100 (48%) and 53 (25%) were healthcare- and community-associated, respectively. An increasing proportion of community-onset cases were observed during twenty years of surveillance. Underlying medical illnesses were common with median (interquartile range) Charlson Comorbidity Index (CCI) scores of 3 (1-5). CCI scores of 0, 1, 2, and 3+ were observed in 37 (18%), 27 (13%), 40 (19%), and 105 (50%) of cases, respectively. All but one of the cases were admitted to hospital for a median (interquartile range) length of stay of 12 (5-34) days. All-cause case-fatality rates in hospital by day 30 and by day 90 were 30 (14%), 28 (13%), and 42 (20%), respectively. The 90-day case-fatality rate increased with increasing comorbidity and was 3% (1/37), 11% (3/27), 25% (10/40), and 27% (28/105) among those with Charlson Comorbidity Indices of 0, 1, 2, and 3+, respectively (p = 0.004). CONCLUSIONS: Although comorbidity is an important determinant of risk, most Achromobacter sp. BSI are of community-onset and one-fifth of cases occur in patients without significant underlying chronic co-morbidities. This study highlights the value of population-based methodologies to define the epidemiology of an infectious disease.

Emergence and impact of oprD mutations in Pseudomonas aeruginosa strains in cystic fibrosis.

BACKGROUND: Antimicrobial resistance in cystic fibrosis (CF) Pseudomonas aeruginosa airway infection is complex and often attributed to chromosomal mutations. How these mutations emerge in specific strains or whether particular gene mutations are clinically informative is unclear. This study focused on oprD, which encodes an outer membrane porin associated with carbapenem resistance when it is downregulated or inactivated. AIM: Determine how mutations in oprD emerge in two prevalent Australian shared CF strains of P. aeruginosa and their clinical relevance. METHODS: The two most common shared CF strains in Queensland were investigated using whole genome sequencing and their oprD sequences and antimicrobial resistance phenotypes were established. P. aeruginosa mutants with the most common oprD variants were constructed and characterised. Clinical variables were compared between people with or without evidence of infection with strains harbouring these variants. RESULTS: Frequently found nonsense mutations arising from a 1-base pair substitution in oprD evolved independently in three sub-lineages, and are likely major contributors to the reduced carbapenem susceptibility observed in the clinical isolates. Lower baseline FEV1 %predicted was identified as a risk factor for infection with a sub-lineage (odds ratio=0.97; 95% confidence interval 0.96-0.99; p<0.001). However, acquiring these sub-lineage strains did not confer an accelerated decline in FEV1 nor increase the risk of death/lung transplantation. CONCLUSIONS: Sub-lineages harbouring specific mutations in oprD have emerged and persisted in the shared strain populations. Infection with the sub-lineages was more likely in people with lower lung function, but this was not predictive of a worse clinical trajectory.

Case report: a fatal case of Aspergillus felis infection in an immunocompetent host.

We report a fatal case of Aspergillus felis invasive rhinosinusitis with secondary cerebral abscesses in an immunocompetent host despite aggressive surgical debridement and combination antifungals. Whilst this organism is known to cause fatalities in cats, only a few cases in humans have been documented, all of which had significant immunosuppression. This is the first human death due to A. felis described in an immunocompetent host.

Repurposing a neurodegenerative disease drug to treat Gram-negative antibiotic-resistant bacterial sepsis.

The emergence of polymyxin resistance in carbapenem-resistant and extended-spectrum ß-lactamase (ESBL)-producing bacteria is a critical threat to human health, and alternative treatment strategies are urgently required. We investigated the ability of the hydroxyquinoline analog ionophore PBT2 to restore antibiotic sensitivity in polymyxin-resistant, ESBL-producing, carbapenem-resistant Gram-negative human pathogens. PBT2 resensitized Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa to last-resort polymyxin class antibiotics, including the less toxic next-generation polymyxin derivative FADDI-287, in vitro. We were unable to select for mutants resistant to PBT2 + FADDI-287 in polymyxin-resistant E. coli containing a plasmid-borne mcr-1 gene or K. pneumoniae carrying a chromosomal mgrB mutation. Using a highly invasive K. pneumoniae strain engineered for polymyxin resistance through mgrB mutation, we successfully demonstrated the efficacy of PBT2 + polymyxin (colistin or FADDI-287) for the treatment of Gram-negative sepsis in immunocompetent mice. In comparison to polymyxin alone, the combination of PBT2 + polymyxin improved survival and reduced bacterial dissemination to the lungs and spleen of infected mice. These data present a treatment modality to break antibiotic resistance in high-priority polymyxin-resistant Gram-negative pathogens.

Temperate Bacteriophages (Prophages) in Pseudomonas aeruginosa Isolates Belonging to the International Cystic Fibrosis Clone (CC274).

Bacteriophages are important in bacterial ecology and evolution. Pseudomonas aeruginosa is the most prevalent bacterial pathogen in chronic bronchopulmonary infection in cystic fibrosis (CF). In this study, we used bioinformatics, microbiological and microscopy techniques to analyze the bacteriophages present in 24 P. aeruginosa isolates belonging to the international CF clone (ST274-CC274). Interestingly, we detected the presence of five members of the Inoviridae family of prophages (Pf1, Pf4, Pf5, Pf6, Pf7), which have previously been observed in P. aeruginosa. In addition, we identified a new filamentous prophage, designated Pf8, in the P. aeruginosa AUS411.500 isolate belonging to the international CF clone. We detected only one prophage, never previously described, from the family Siphoviridiae (with 66 proteins and displaying homology with PHAGE_Pseudo_phi297_NC_016762). This prophage was isolated from the P. aeruginosa AUS531 isolate carrying a new gene which is implicated in the phage infection ability, named Bacteriophage Control Infection (bci). We characterized the role of the Bci protein in bacteriophage infection and in regulating the host Quorum Sensing (QS) system, motility and biofilm and pyocyanin production in the P. aeruginosa isogenic mutant AUS531Δbci isolate. The findings may be relevant for the identification of targets in the development of new strategies to control P. aeruginosa infections, particularly in CF patients.

Achromobacter Infections and Treatment Options.

Achromobacter is a genus of nonfermenting Gram-negative bacteria under order Burkholderiales Although primarily isolated from respiratory tract of people with cystic fibrosis, Achromobacter spp. can cause a broad range of infections in hosts with other underlying conditions. Their rare occurrence and ever-changing taxonomy hinder defining their clinical features, risk factors for acquisition and adverse outcomes, and optimal treatment. Achromobacter spp. are intrinsically resistant to several antibiotics (e.g., most cephalosporins, aztreonam, and aminoglycosides), and are increasingly acquiring resistance to carbapenems. Carbapenem resistance is mainly caused by multidrug efflux pumps and metallo-ß-lactamases, which are not expected to be overcome by new ß-lactamase inhibitors. Among the other new antibiotics, cefiderocol, and eravacycline were used as salvage therapy for a limited number of patients with Achromobacter infections. In this article, we aim to give an overview of the antimicrobial resistance in Achromobacter species, highlighting the possible place of new antibiotics in their treatment.

Duplex real-time PCR assay for the simultaneous detection of Achromobacter xylosoxidans and Achromobacter spp.

Several members of the Gram-negative environmental bacterial genus Achromobacter are associated with serious infections, with Achromobacter xylosoxidans being the most common. Despite their pathogenic potential, little is understood about these intrinsically drug-resistant bacteria and their role in disease, leading to suboptimal diagnosis and management. Here, we performed comparative genomics for 158 Achromobacter spp. genomes to robustly identify species boundaries, reassign several incorrectly speciated taxa and identify genetic sequences specific for the genus Achromobacter and for A. xylosoxidans. Next, we developed a Black Hole Quencher probe-based duplex real-time PCR assay, Ac-Ax, for the rapid and simultaneous detection of Achromobacter spp. and A. xylosoxidans from both purified colonies and polymicrobial clinical specimens. Ac-Ax was tested on 119 isolates identified as Achromobacter spp. using phenotypic or genotypic methods. In comparison to these routine diagnostic methods, the duplex assay showed superior identification of Achromobacter spp. and A. xylosoxidans, with five Achromobacter isolates failing to amplify with Ac-Ax confirmed to be different genera according to 16S rRNA gene sequencing. Ac-Ax quantified both Achromobacter spp. and A. xylosoxidans down to ~110 genome equivalents and detected down to ~12 and ~1 genome equivalent(s), respectively. Extensive in silico analysis, and laboratory testing of 34 non-Achromobacter isolates and 38 adult cystic fibrosis sputa, confirmed duplex assay specificity and sensitivity. We demonstrate that the Ac-Ax duplex assay provides a robust, sensitive and cost-effective method for the simultaneous detection of all Achromobacter spp. and A. xylosoxidans and will facilitate the rapid and accurate diagnosis of this important group of pathogens.

Antimicrobial Resistance in ESKAPE Pathogens.

Antimicrobial-resistant ESKAPE ( Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens represent a global threat to human health. The acquisition of antimicrobial resistance genes by ESKAPE pathogens has reduced the treatment options for serious infections, increased the burden of disease, and increased death rates due to treatment failure and requires a coordinated global response for antimicrobial resistance surveillance. This looming health threat has restimulated interest in the development of new antimicrobial therapies, has demanded the need for better patient care, and has facilitated heightened governance over stewardship practices.

Pathogen to commensal? Longitudinal within-host population dynamics, evolution, and adaptation during a chronic >16-year Burkholderia pseudomallei infection.

Although acute melioidosis is the most common outcome of Burkholderia pseudomallei infection, we have documented a case, P314, where disease severity lessened with time, and the pathogen evolved towards a commensal relationship with the host. In the current study, we used whole-genome sequencing to monitor this long-term symbiotic relationship to better understand B. pseudomallei persistence in P314's sputum despite intensive initial therapeutic regimens. We collected and sequenced 118 B. pseudomallei isolates from P314's airways over a >16-year period, and also sampled the patient's home environment, recovering six closely related B. pseudomallei isolates from the household water system. Using comparative genomics, we identified 126 SNPs in the core genome of the 124 isolates or 162 SNPs/indels when the accessory genome was included. The core SNPs were used to construct a phylogenetic tree, which demonstrated a close relationship between environmental and clinical isolates and detailed within-host evolutionary patterns. The phylogeny had little homoplasy, consistent with a strictly clonal mode of genetic inheritance. Repeated sampling revealed evidence of genetic diversification, but frequent extinctions left only one successful lineage through the first four years and two lineages after that. Overall, the evolution of this population is nonadaptive and best explained by genetic drift. However, some genetic and phenotypic changes are consistent with in situ adaptation. Using a mouse model, P314 isolates caused greatly reduced morbidity and mortality compared to the environmental isolates. Additionally, potentially adaptive phenotypes emerged and included differences in the O-antigen, capsular polysaccharide, motility, and colony morphology. The >13-year co-existence of two long-lived lineages presents interesting hypotheses that can be tested in future studies to provide additional insights into selective pressures, niche differentiation, and microbial adaptation. This unusual melioidosis case presents a rare example of the evolutionary progression towards commensalism by a highly virulent pathogen within a single human host.

Complex Multilevel Control of Hemolysin Production by Uropathogenic Escherichia coli.

Uropathogenic Escherichia coli (UPEC) is the major cause of urinary tract infections. Nearly half of all UPEC strains secrete hemolysin, a cytotoxic pore-forming toxin. Here, we show that the prevalence of the hemolysin toxin gene (hlyA) is highly variable among the most common 83 E. coli sequence types (STs) represented on the EnteroBase genome database. To explore this diversity in the context of a defined monophyletic lineage, we contextualized sequence variation of the hlyCABD operon within the genealogy of the globally disseminated multidrug-resistant ST131 clone. We show that sequence changes in hlyCABD and its newly defined 1.616-kb-long leader sequence correspond to phylogenetic designation, and that ST131 strains with the strongest hemolytic activity belong to the most extensive multidrug-resistant sublineage (clade C2). To define the set of genes involved in hemolysin production, the clade C2 strain S65EC was completely sequenced and subjected to a genome-wide screen by combining saturated transposon mutagenesis and transposon-directed insertion site sequencing with the capacity to lyse red blood cells. Using this approach, and subsequent targeted mutagenesis and complementation, 13 genes were confirmed to be specifically required for production of active hemolysin. New hemolysin-controlling elements included discrete sets of genes involved in lipopolysaccharide (LPS) inner core biosynthesis (waaC, waaF, waaG, and rfaE) and cytoplasmic chaperone activity (dnaK and dnaJ), and we show these are required for hemolysin secretion. Overall, this work provides a unique description of hemolysin sequence diversity in a single clonal lineage and describes a complex multilevel system of regulatory control for this important toxin.IMPORTANCE Uropathogenic E. coli (UPEC) is the major cause of urinary tract infections and a frequent cause of sepsis. Nearly half of all UPEC strains produce the potent cytotoxin hemolysin, and its expression is associated with enhanced virulence. In this study, we explored hemolysin variation within the globally dominant UPEC ST131 clone, finding that strains from the ST131 sublineage with the greatest multidrug resistance also possess the strongest hemolytic activity. We also employed an innovative forward genetic screen to define the set of genes required for hemolysin production. Using this approach, and subsequent targeted mutagenesis and complementation, we identified new hemolysin-controlling elements involved in LPS inner core biosynthesis and cytoplasmic chaperone activity, and we show that mechanistically they are required for hemolysin secretion. These original discoveries substantially enhance our understanding of hemolysin regulation, secretion and function.

Quantitative real-time PCR assay for the rapid identification of the intrinsically multidrug-resistant bacterial pathogen Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia is emerging as an important cause of disease in nosocomial and community-acquired settings, including bloodstream, wound and catheter-associated infections. Cystic fibrosis (CF) airways also provide optimal growth conditions for various opportunistic pathogens with high antibiotic tolerance, including S. maltophilia. Currently, there is no rapid, cost-effective and accurate molecular method for detecting this potentially life-threatening pathogen, particularly in polymicrobial specimens, suggesting that its true prevalence is underestimated. Here, we used large-scale comparative genomics to identify a specific genetic target for S. maltophilia, with subsequent development and validation of a real-time PCR assay for its detection. Analysis of 167 Stenotrophomonas spp. genomes identified a conserved 4 kb region in S. maltophilia, which was targeted for Black Hole Quencher assay design. Our assay yielded the positive detection of 89 of 89 (100%) clinical S. maltophilia strains, and no amplification of 23 non-S. maltophilia clinical isolates. S. maltophilia was detected in 10 of 16 CF sputa, demonstrating the assay's utility for direct detection in respiratory specimens. The assay demonstrated good sensitivity, with limits of detection and quantitation on pure culture of ~10 and ~100 genome equivalents, respectively. Our assay provides a highly specific, sensitive and cost-effective method for the accurate identification of S. maltophilia, and will improve the diagnosis and treatment of this under-recognized pathogen by enabling its accurate and rapid detection from polymicrobial clinical and environmental samples.

Reconciling Antimicrobial Susceptibility Testing and Clinical Response in Antimicrobial Treatment of Chronic Cystic Fibrosis Lung Infections.

Median cystic fibrosis (CF) survival has increased dramatically over time due to several factors, including greater availability and use of antimicrobial therapies. During the progression of CF lung disease, however, the emergence of multidrug antimicrobial resistance can limit treatment effectiveness, threatening patient longevity. Current planktonic-based antimicrobial susceptibility testing lacks the ability to predict clinical response to antimicrobial treatment of chronic CF lung infections. There are numerous reasons for these limitations including bacterial phenotypic and genotypic diversity, polymicrobial interactions, and impaired antibiotic efficacy within the CF lung environment. The parallels to other chronic diseases such as non-CF bronchiectasis are discussed as well as research priorities for moving forward.

Transmission of bacteria in bronchiectasis and chronic obstructive pulmonary disease: Low burden of cough aerosols.

BACKGROUND AND OBJECTIVE: Aerosol transmission of Pseudomonas aeruginosa has been suggested as a possible mode of respiratory infection spread in patients with cystic fibrosis (CF); however, whether this occurs in other suppurative lung diseases is unknown. Therefore, we aimed to determine if (i) patients with bronchiectasis (unrelated to CF) or chronic obstructive pulmonary disease (COPD) can aerosolize P. aeruginosa during coughing and (ii) if genetically indistinguishable (shared) P. aeruginosa strains are present in these disease cohorts. METHODS: People with bronchiectasis or COPD and P. aeruginosa respiratory infection were recruited for two studies. Aerosol study: Participants (n = 20) underwent cough testing using validated cough rigs to determine the survival of P. aeruginosa aerosols in the air over distance and duration. Genotyping study: P. aeruginosa sputum isolates (n = 95) were genotyped using the iPLEX20SNP platform, with a subset subjected to the enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) assay to ascertain their genetic relatedness. RESULTS: Aerosol study: Overall, 7 of 20 (35%) participants released P. aeruginosa cough aerosols during at least one of the cough aerosol tests. These cough aerosols remained viable for 4 m from the source and for 15 min after coughing. The mean total aerosol count of P. aeruginosa at 2 m was two colony-forming units. Typing study: No shared P. aeruginosa strains were identified. CONCLUSION: Low viable count of P. aeruginosa cough aerosols and a lack of shared P. aeruginosa strains observed suggest that aerosol transmission of P. aeruginosa is an unlikely mode of respiratory infection spread in patients with bronchiectasis and COPD.

2-Hydroxylation of Acinetobacter baumannii Lipid A Contributes to Virulence.

Acinetobacter baumannii causes a wide range of nosocomial infections. This pathogen is considered a threat to human health due to the increasingly frequent isolation of multidrug-resistant strains. There is a major gap in knowledge on the infection biology of A. baumannii, and only a few virulence factors have been characterized, including lipopolysaccharide. The lipid A expressed by A. baumannii is hepta-acylated and contains 2-hydroxylaurate. The late acyltransferases controlling the acylation of lipid A have been already characterized. Here, we report the characterization of A. baumannii LpxO, which encodes the enzyme responsible for the 2-hydroxylation of lipid A. By genetic methods and mass spectrometry, we demonstrate that LpxO catalyzes the 2-hydroxylation of the laurate transferred by A. baumannii LpxL. LpxO-dependent lipid A 2-hydroxylation protects A. baumannii from polymyxin B, colistin, and human ß-defensin 3. LpxO contributes to the survival of A. baumannii in human whole blood and is required for pathogen survival in the waxmoth Galleria mellonella LpxO also protects Acinetobacter from G. mellonella antimicrobial peptides and limits their expression. Further demonstrating the importance of LpxO-dependent modification in immune evasion, 2-hydroxylation of lipid A limits the activation of the mitogen-activated protein kinase Jun N-terminal protein kinase to attenuate inflammatory responses. In addition, LpxO-controlled lipid A modification mediates the production of the anti-inflammatory cytokine interleukin-10 (IL-10) via the activation of the transcriptional factor CREB. IL-10 in turn limits the production of inflammatory cytokines following A. baumannii infection. Altogether, our studies suggest that LpxO is a candidate for the development of anti-A. baumannii drugs.

Correction: Within-host whole genome analysis of an antibiotic resistant Pseudomonas aeruginosa strain sub-type in cystic fibrosis.

[This corrects the article DOI: 10.1371/journal.pone.0172179.].