Phage-Bacterial Interaction Alters Phenotypes Associated with Virulence in Acinetobacter baumannii.

Bacteriophages exert strong selection on their bacterial hosts to evolve resistance. At the same time, the fitness costs on bacteria following phage resistance may change their virulence, which may affect the therapeutic outcomes of phage therapy. In this study, we set out to assess the costs of phage resistance on the in vitro virulence of priority 1 nosocomial pathogenic bacterium, Acinetobacter baumannii. By subjecting phage-resistant variant Ev5-WHG of A. baumannii WHG40004 to several in vitro virulence profiles, we found that its resistance to phage is associated with reduced fitness in host microenvironments. Also, the mutant exhibited impaired adhesion and invasion to mammalian cells, as well as increased susceptibility to macrophage phagocytosis. Furthermore, the whole-genome sequencing of the mutant revealed that there exist multiple mutations which may play a role in phage resistance and altered virulence. Altogether, this study demonstrates that resistance to phage can significantly alter phenotypes associated with virulence in Acinetobacter baumannii.

Acinetobacter baumannii as an oro-dental pathogen: a red alert!!

OBJECTIVES: This review highlights the existence and association of Acinetobacter baumannii with the oro-dental diseases, transforming this systemic pathogen into an oral pathogen. The review also hypothesizes possible reasons for the categorization of this pathogen as code blue due to its stealthy entry into the oral cavity. METHODOLOGY: Study data were retrieved from various search engines reporting specifically on the association of A. baumannii in dental diseases and tray set-ups. Articles were also examined regarding obtained outcomes on A. baumannii biofilm formation, iron acquisitions, magnitude of antimicrobial resistance, and its role in the oral cancers. RESULTS: A. baumannii is associated with the oro-dental diseases and various virulence factors attribute for the establishment and progression of oro-mucosal infections. Its presence in the oral cavity is frequent in oral microbiomes, conditions of impaired host immunity, age related illnesses, and hospitalized individuals. Many sources also contribute for its prevalence in the dental health care environment and the presence of drug resistant traits is also observed. Its association with oral cancers and oral squamous cell carcinoma is also evident. CONCLUSIONS: The review calls for awareness on the emergence of A. baumannii in dental clinics and for the need for educational programs to monitor and control the sudden outbreaks of such virulent and resistant traits in the dental health care settings.

The tRNA methyltransferase TrmB is critical for Acinetobacter baumannii stress responses and pulmonary infection.

IMPORTANCE: As deficiencies in tRNA modifications have been linked to human diseases such as cancer and diabetes, much research has focused on the modifications' impacts on translational regulation in eukaryotes. However, the significance of tRNA modifications in bacterial physiology remains largely unexplored. In this paper, we demonstrate that the m7G tRNA methyltransferase TrmB is crucial for a top-priority pathogen, Acinetobacter baumannii, to respond to stressors encountered during infection, including oxidative stress, low pH, and iron deprivation. We show that loss of TrmB dramatically attenuates a murine pulmonary infection. Given the current efforts to use another tRNA methyltransferase, TrmD, as an antimicrobial therapeutic target, we propose that TrmB, and other tRNA methyltransferases, may also be viable options for drug development to combat multidrug-resistant A. baumannii.

Effect of Hcp Iron Ion Regulation on the Interaction Between Acinetobacter baumannii With Human Pulmonary Alveolar Epithelial Cells and Biofilm Formation.

Acinetobacter baumannii is a type of bacterial nosocomial infection with severe drug resistance. Hemolysin co-regulated protein (Hcp) is a marker of activated type VI secretion system (T6SS), a key secretory system that promotes Gram-negative bacteria colonization, adhesion, and invasion of host cells. Hcp is also regulated by iron ions (Fe). In this study, an ATCC17978 hcp deletion strain (ATCC17978Δhcp), an hcp complement strain (ATCC17978Δhcp+ ), and an A. baumannii-green fluorescent protein (GFP) strain were constructed and used to investigate the role of hcp in bacterial adhesion to cells (human pulmonary alveolar epithelial cells (HPAEpiC)) and biofilm formation. Our results indicate that the inhibitory concentrations of the three A. baumannii strains (ATCC17978 wild type, ATCC17978Δhcp, and ATCC17978Δhcp+) were drug-sensitive strains. A. baumannii hcp gene and iron ions might be involved in promoting the formation of a biofilm and host-bacteria interaction. Iron ions affected the ability of A. baumannii to adhere to cells, as there was no significant difference in the bacterial numbers when assessing the adhesion of the three strains to HPAEpiC in the presence of iron ion concentrations of 0 µM (F = 3.1800, p = 0.1144), 25 µM (F = 2.067, p = 0.2075), 100 µM (F = 30.52, p = 0.0007), and 400 µM (F = 17.57, p = 0.0031). The three strains showed significant differences in their ability to adhere to HPAEpiC. The numbers of bacteria adhesion to HPAEpiC were ATCC17978Δhcp>ATCC17978Δhcp+>ATCC17978 in descending order. Hcp gene was positively regulated by iron ions in the bacteria-cells' co-culture. It is speculated that the effect of iron ions on the interaction between A. baumannii and HPAEpiC might be related to the transport function of hcp and bacterial immune escape mechanisms.

Deciphering Multidrug-Resistant Acinetobacter baumannii from a Pediatric Cancer Hospital in Egypt.

Infection by multidrug-resistant (MDR) Acinetobacter baumannii is one of the major causes of hospital-acquired infections worldwide. The ability of A. baumannii to survive in adverse conditions as well as its extensive antimicrobial resistance make it one of the most difficult to treat pathogens associated with high mortality rates. The aim of this study was to investigate MDR A. baumannii that has spread among pediatric cancer patients in the Children's Cancer Hospital Egypt 57357. Whole-genome sequencing was used to characterize 31 MDR A. baumannii clinical isolates. Phenotypically, the isolates were MDR, with four isolates showing resistance to the last-resort antibiotic colistin. Multilocus sequence typing showed the presence of eight clonal groups, two of which were previously reported to cause outbreaks in Egypt, and one novel sequence type (ST), Oxf-ST2246. Identification of the circulating plasmids showed the presence of two plasmid lineages in the isolates, strongly governed by sequence type. A large number of antimicrobial genes with a range of resistance mechanisms were detected in the isolates, including ß-lactamases and antibiotic efflux pumps. Analysis of insertion sequences (ISs) revealed the presence of ISAba1 and ISAba125 in all the samples, which amplify ß-lactamase expression, causing extensive carbapenem resistance. Mutation analysis was used to decipher underlying mutations responsible for colistin resistance and revealed novel mutations in several outer membrane proteins, in addition to previously reported mutations in pmrB. Altogether, understanding the transmissibility of A. baumannii as well as its resistance and virulence mechanisms will help develop novel treatment options for better management of hospital-acquired infections. IMPORTANCE Acinetobacter baumannii represents a major health threat, in particular among immunocompromised cancer patients. The rise in carbapenem-resistant A. baumannii, and the development of resistance to the last-resort antimicrobial agent colistin, complicates the management of A. baumannii outbreaks and increases mortality rates. Here, we investigate 31 multidrug resistant A. baumannii isolates from pediatric cancer patients in Children's Cancer Hospital Egypt (CCHE) 57357 via whole-genome sequencing. Multilocus sequence typing (MLST) showed the presence of eight clonal groups including a novel sequence type. In silico detection of antimicrobial-resistant genes and virulence factors revealed a strong correlation between certain virulence genes and mortality as well as several point mutations in outer membrane proteins contributing to colistin resistance. Detection of CRISPR/Cas sequences in the majority of the samples was strongly correlated with the presence of prophage sequences and associated with failure of bacteriophage therapy. Altogether, understanding the genetic makeup of circulating A. baumannii is essential for better management of outbreaks.

Antiseptic 9-Meric Peptide with Potency against Carbapenem-Resistant Acinetobacter baumannii Infection.

Carbapenem-resistant A. baumannii (CRAB) infection can cause acute host reactions that lead to high-fatality sepsis, making it important to develop new therapeutic options. Previously, we developed a short 9-meric peptide, Pro9-3D, with significant antibacterial and cytotoxic effects. In this study, we attempted to produce safer peptide antibiotics against CRAB by reversing the parent sequence to generate R-Pro9-3 and R-Pro9-3D. Among the tested peptides, R-Pro9-3D had the most rapid and effective antibacterial activity against Gram-negative bacteria, particularly clinical CRAB isolates. Analyses of antimicrobial mechanisms based on lipopolysaccharide (LPS)-neutralization, LPS binding, and membrane depolarization, as well as SEM ultrastructural investigations, revealed that R-Pro9-3D binds strongly to LPS and impairs the membrane integrity of CRAB by effectively permeabilizing its outer membrane. R-Pro9-3D was also less cytotoxic and had better proteolytic stability than Pro9-3D and killed biofilm forming CRAB. As an LPS-neutralizing peptide, R-Pro9-3D effectively reduced LPS-induced pro-inflammatory cytokine levels in RAW 264.7 cells. The antiseptic abilities of R-Pro9-3D were also investigated using a mouse model of CRAB-induced sepsis, which revealed that R-Pro9-3D reduced multiple organ damage and attenuated systemic infection by acting as an antibacterial and immunosuppressive agent. Thus, R-Pro9-3D displays potential as a novel antiseptic peptide for treating Gram-negative CRAB infections.

Role of Iron-Containing Alcohol Dehydrogenases in Acinetobacter baumannii ATCC 19606 Stress Resistance and Virulence.

Most bacteria possess alcohol dehydrogenase (ADH) genes (Adh genes) to mitigate alcohol toxicity, but these genes have functions beyond alcohol degradation. Previous research has shown that ADH can modulate quorum sensing in Acinetobacter baumannii, a rising opportunistic pathogen. However, the number and nature of Adh genes in A. baumannii have not yet been fully characterized. We identified seven alcohol dehydrogenases (NAD+-ADHs) from A. baumannii ATCC 19606, and examined the roles of three iron-containing ADHs, ADH3, ADH4, and ADH6. Marker-less mutation was used to generate Adh3, Adh4, and Adh6 single, double, and triple mutants. Disrupted Adh4 mutants failed to grow in ethanol-, 1-butanol-, or 1-propanol-containing mediums, and recombinant ADH4 exhibited strongest activity against ethanol. Stress resistance assays with inorganic and organic hydroperoxides showed that Adh3 and Adh6 were key to oxidative stress resistance. Virulence assays performed on the Galleria mellonella model organism revealed that Adh4 mutants had comparable virulence to wild-type, while Adh3 and Adh6 mutants had reduced virulence. The results suggest that ADH4 is primarily involved in alcohol metabolism, while ADH3 and ADH6 are key to stress resistance and virulence. Further investigation into the roles of other ADHs in A. baumannii is warranted.

Mechanical ventilation enhances Acinetobacter baumannii-induced lung injury through JNK pathways.

BACKGROUND: Patients in intensive care units (ICUs) often received broad-spectrum antibiotic treatment and Acinetobacter baumannii (A.b.) and Pseudomonas aeruginosa (P.a.) were the most common pathogens causing ventilator-associated pneumonia (VAP). This study aimed to examine the effects and mechanism of mechanical ventilation (MV) on A.b.-induced lung injury and the involvement of alveolar macrophages (AMs). METHODS: C57BL/6 wild-type (WT) and c-Jun N-terminal kinase knockout (JNK1-/-) mice received MV for 3 h at 2 days after nasal instillation of A.b., P.a. (1 × 106 colony-forming unit, CFU), or normal saline. RESULTS: Intranasal instillation of 106 CFU A.b. in C57BL/6 mice induced a significant increase in total cells and protein levels in the bronchoalveolar lavage fluid (BALF) and neutrophil infiltration in the lungs. MV after A.b. instillation increases neutrophil infiltration, interleukin (IL)-6 and vascular cell adhesion molecule (VCAM) mRNA expression in the lungs and total cells, IL-6 levels, and nitrite levels in the BALF. The killing activity of AMs against A.b. was lower than against P.a. The diminished killing activity was parallel with decreased tumor necrosis factor-α production by AMs compared with A.b. Inducible nitric oxide synthase inhibitor, S-methylisothiourea, decreased the total cell number in BALF on mice receiving A.b. instillation and ventilation. Moreover, MV decreased the A.b. and P.a. killing activity of AMs. MV after A.b. instillation induced less total cells in the BALF and nitrite production in the serum of JNK1-/- mice than those of WT mice. CONCLUSION: A.b. is potent in inducing neutrophil infiltration in the lungs and total protein in the BALF. MV enhances A.b.-induced lung injury through an increase in the expression of VCAM and IL-6 levels in the BALF and a decrease in the bacteria-killing activity of AMs. A lower inflammation level in JNK1-/- mice indicates that A.b.-induced VAP causes lung injury through JNK signaling pathway in the lungs.

Acinetobacter baumannii can use multiple siderophores for iron acquisition, but only acinetobactin is required for virulence.

Acinetobacter baumannii is an emerging pathogen that poses a global health threat due to a lack of therapeutic options for treating drug-resistant strains. In addition to acquiring resistance to last-resort antibiotics, the success of A. baumannii is partially due to its ability to effectively compete with the host for essential metals. Iron is fundamental in shaping host-pathogen interactions, where the host restricts availability of this nutrient in an effort to curtail bacterial proliferation. To circumvent restriction, pathogens possess numerous mechanisms to obtain iron, including through the use of iron-scavenging siderophores. A. baumannii elaborates up to ten distinct siderophores, encoded from three different loci: acinetobactin and pre-acinetobactin (collectively, acinetobactin), baumannoferrins A and B, and fimsbactins A-F. The expression of multiple siderophores is common amongst bacterial pathogens and often linked to virulence, yet the collective contribution of these siderophores to A. baumannii survival and pathogenesis has not been investigated. Here we begin dissecting functional redundancy in the siderophore-based iron acquisition pathways of A. baumannii. Excess iron inhibits overall siderophore production by the bacterium, and the siderophore-associated loci are uniformly upregulated during iron restriction in vitro and in vivo. Further, disrupting all of the siderophore biosynthetic pathways is necessary to drastically reduce total siderophore production by A. baumannii, together suggesting a high degree of functional redundancy between the metabolites. By contrast, inactivation of acinetobactin biosynthesis alone impairs growth on human serum, transferrin, and lactoferrin, and severely attenuates survival of A. baumannii in a murine bacteremia model. These results suggest that whilst A. baumannii synthesizes multiple iron chelators, acinetobactin is critical to supporting growth of the pathogen on host iron sources. Given the acinetobactin locus is highly conserved and required for virulence of A. baumannii, designing therapeutics targeting the biosynthesis and/or transport of this siderophore may represent an effective means of combating this pathogen.

High mortality in an outbreak of multidrug resistant Acinetobacter baumannii infection introduced to an oncological hospital by a patient transferred from a general hospital.

OBJECTIVE: To describe the clinical features, outcomes, and molecular epidemiology of an outbreak of multidrug resistant (MDR) A. baumannii. METHODS: We performed a retrospective analysis of all MDR A. baumannii isolates recovered during an outbreak from 2011 to 2015 in a tertiary care cancer hospital. Cases were classified as colonized or infected. We determined sequence types following the Bartual scheme and plasmid profiles. RESULTS: There were 106 strains of A. baumannii isolated during the study period. Sixty-six (62.3%) were considered as infection and 40 (37.7%) as colonization. The index case, identified by molecular epidemiology, was a patient with a drain transferred from a hospital outside Mexico City. Ninety-eight additional cases had the same MultiLocus Sequence Typing (MLST) 758, of which 94 also had the same plasmid profile, two had an extra plasmid, and two had a different plasmid. The remaining seven isolates belonged to different MLSTs. Fifty-three patients (50%) died within 30 days of A. baumanniii isolation: 28 (20%) in colonized and 45 (68.2%) in those classified as infection (p<0.001). In multivariate regression analysis, clinical infection and patients with hematologic neoplasm, predicted 30-day mortality. The molecular epidemiology of this outbreak showed the threat posed by the introduction of MDR strains from other institutions in a hospital of immunosuppressed patients and highlights the importance of adhering to preventive measures, including contact isolation, when admitting patients with draining wounds who have been hospitalized in other institutions.

In Vitro Evaluation of Antimicrobial Peptide Tridecaptin M in Combination with Other Antibiotics against Multidrug Resistant Acinetobacter baumannii.

The rapid emergence of antimicrobial resistance in Acinetobacter baumannii coupled with the dried pipeline of novel treatments has driven the search for new therapeutic modalities. Gram-negative bacteria have an extra outer membrane that serves as a permeability barrier for various hydrophobic and/or large compounds. One of the popular approaches to tackle this penetration barrier is use of potentiators or adjuvants in combination with traditional antibiotics. This study reports the in vitro potential of an antimicrobial peptide tridecaptin M in combination with other antibiotics against different strains of A. baumannii. Tridecaptin M sensitized the bacteria to rifampicin, vancomycin, and ceftazidime. Further, we observed that a tridecaptin M and rifampicin combination killed the bacteria completely in 4 h in an ex vivo blood infection model and was superior to rifampicin monotherapy. The study also found that concomitant administration of both compounds is not necessary to achieve the antimicrobial effect. Bacteria pre-treated with tridecaptin M (for 2-4 h) followed by exposure to rifampicin showed similar killing as obtained for combined treatment. Additionally, this combination hampered the survival of persister development in comparison to rifampicin alone. These findings encourage the future investigation of this combination to treat severe infections caused by extremely drug-resistant A. baumannii.

Role of PstS in the Pathogenesis of Acinetobacter baumannii Under Microaerobiosis and Normoxia.

Acinetobacter baumannii is a successful pathogen responsible for infections with high mortality rate. During the course of infection it can be found in microaerobic environments, which influences virulence factor expression. From a previous transcriptomic analysis of A. baumannii ATCC 17978 under microaerobiosis, we know the gene pstS is overexpressed under microaerobiosis. Here, we studied its role in A. baumannii virulence. pstS loss significantly decreased bacterial adherence and invasion into A549 cells and increased A549 cell viability. pstS loss also reduced motility and biofilm-forming ability of A. baumannii. In a peritoneal sepsis murine model, the minimum lethal dose required by A. baumannii ATCC 17978 ΔpstS was lower compared to the wild type (4.3 vs 3.2 log colony forming units/mL, respectively), and the bacterial burden in tissues and fluids was lower. Thus, the loss of the phosphate sensor PstS produced a decrease in A. baumannii pathogenesis, supporting its role as a virulence factor.

The Acinetobacter trimeric autotransporter adhesin Ata controls key virulence traits of Acinetobacter baumannii.

Acinetobacter baumannii is a Gram-negative pathogen that causes a multitude of nosocomial infections. The Acinetobacter trimeric autotransporter adhesin (Ata) belongs to the superfamily of trimeric autotransporter adhesins which are important virulence factors in many Gram-negative species. Phylogenetic profiling revealed that ata is present in 78% of all sequenced A. baumannii isolates but only in 2% of the closely related species A. calcoaceticus and A. pittii. Employing a markerless ata deletion mutant of A. baumannii ATCC 19606 we show that adhesion to and invasion into human endothelial and epithelial cells depend on Ata. Infection of primary human umbilical cord vein endothelial cells (HUVECs) with A. baumannii led to the secretion of interleukin (IL)-6 and IL-8 in a time- and Ata-dependent manner. Furthermore, infection of HUVECs by WT A. baumannii was associated with higher rates of apoptosis via activation of caspases-3 and caspase-7, but not necrosis, in comparison to ∆ata. Ata deletion mutants were furthermore attenuated in their ability to kill larvae of Galleria mellonella and to survive in larvae when injected at sublethal doses. This indicates that Ata is an important multifunctional virulence factor in A. baumannii that mediates adhesion and invasion, induces apoptosis and contributes to pathogenicity in vivo.

Multidrug-resistant Acinetobacter baumannii resists reactive oxygen species and survives in macrophages.

We investigated the intracellular survival of multidrug-resistant Acinetobacter baumannii (MDRAB) clinical isolates in macrophages, after phagocytosis, to determine their virulence characteristics. After ATCC 19606 and 5 clinical isolates of MDRAB were phagocytosed by mouse and human macrophages, the bacterial count of MDRAB strains, R4 and R5, increased in the mouse macrophages, 24 hours after phagocytosis. Bacterial count of the strains, R1 and R2, was almost equal 4 and 24 hours after phagocytosis. Intracellular reactive oxygen species was detected in the macrophages after phagocytosis of these bacteria. Further, the strains R1, R2, R4, and R5 showed higher catalase activity than ATCC 19606. Additionally, strains R1, R4, and R5 grew more efficiently than ATCC 19606 in the presence of H2O2, whereas growth of strains R2 and R3 was marginally more than that of ATCC 19606 in the presence of H2O2. The MDRAB clinical isolates altered the expression of TNF-α, IL-1ß, IL-6, and MIP-2 mRNA induced in J774A.1 cells, 24 hours after phagocytosis. These results provide insights into the renewed virulence characteristics of MDRAB clinical isolates. Finally, tigecycline killed MDRAB phagocytosed by the macrophages more effectively than colistin, although colistin and tigecycline are both considered effective antibiotics for the treatment of MDRAB.

Efficacy of Humanized Cefiderocol Exposure Is Unaltered by Host Iron Overload in the Thigh Infection Model.

Cefiderocol is a siderophore-cephalosporin conjugate with greater in vitro potency under iron-depleted conditions. During infection, iron is scarce in host tissue; however, it is not known whether iron overload in the host, such as in cases of hereditary hemochromatosis, alters the efficacy of cefiderocol. We compared cefiderocol efficacy between iron-overloaded and standard murine thigh infection models. Female CD-1 mice rendered neutropenic received 2 weeks of iron dextran at 100 mg/kg of body weight/day intraperitoneally (iron-overloaded model) or no injections (standard model). Mice were inoculated (107 CFU/ml) with Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa with previously determined cefiderocol MICs from 0.25 to 64 mg/liter. Human-simulated regimens of cefiderocol or meropenem (2 g every 8 h [q8h], 3-h infusion) were administered for 24 h (31 strains) or 72 h (15 strains; cefiderocol only). Procedures were simultaneously performed in standard and iron-overloaded models. Mean bacterial burdens (log10 CFU/thigh) at baseline were 5.75 ± 0.47 versus 5.81 ± 0.51 in standard versus iron-overloaded models, respectively. At 24 h, mean burdens in standard versus iron-overloaded models decreased by -0.8 ± 1.9 versus -1.2 ± 2.0 (P = 0.25) in meropenem-treated mice and by -1.5 ± 1.4 versus -1.6 ± 1.5 (P = 0.54) in cefiderocol-treated mice. At 72 h, mean burdens in cefiderocol-treated mice decreased by -2.5 ± 1.5 versus -2.5 ± 1.4. No overall differences in efficacy between the models were observed for meropenem or cefiderocol. Human-simulated exposure of cefiderocol is equally efficacious in iron-overloaded and normal hosts. The potential clinical use of cefiderocol to treat Gram-negative infections in patients with iron overload is supported.

Pharmacokinetics, Safety, and Tolerability of Intravenous Durlobactam and Sulbactam in Subjects with Renal Impairment and Healthy Matched Control Subjects.

Sulbactam-durlobactam is being developed for the treatment of infections caused by Acinetobacter baumannii, including those caused by multidrug- and carbapenem-resistant isolates. This was a phase 1 study to evaluate the effects of various degrees of renal impairment, including subjects with end-stage renal disease (ESRD) on hemodialysis (HD), on the pharmacokinetics and safety profile of durlobactam (also known as ETX2514) and sulbactam after single intravenous (i.v.) dose administration. For healthy subjects and those with mild or moderate renal impairment (RI), single 1,000-mg doses each of durlobactam and sulbactam via a 3-h i.v. infusion were administered, and for severe renal impairment, 500-mg doses were administered. For subjects with ESRD and HD, 500-mg i.v. doses each of durlobactam and sulbactam were administered post-HD and pre-HD, with a 1-week washout between doses. Among 34 subjects, decreasing renal function increased systemic exposure (peak plasma concentration [Cmax] and area under the concentration-time curve [AUC]) to durlobactam and sulbactam in a generally linear manner. In healthy subjects and in those with mild or moderate renal impairment, the majority of durlobactam and sulbactam was excreted in the urine, while approximately 40% or less was excreted in urine in subjects with severe renal impairment or ESRD. In subjects with ESRD, hemodialysis was effective at removing both durlobactam and sulbactam from plasma. Renal impairment had no effect of the safety/tolerability profile of durlobactam and sulbactam. In summary, RI and ESRD had a predictable effect on the pharmacokinetic (PK) profile of durlobactam and sulbactam with no adverse effects on the safety/tolerability profile. Durlobactam and sulbactam are cleared to a similar extent by renal elimination and are impacted similarly by renal impairment. The results from this study have been used with population PK modeling and nonclinically derived PK/PD (pharmacodynamic) exposure targets to establish dosage recommendations for durlobactam and sulbactam in patients with various degrees of RI. The dosing regimen of durlobactam-sulbactam will require adjustment in patients with severe renal insufficiency and in those with ESRD.

Antibiotic-Resistant Acinetobacter baumannii Is Susceptible to the Novel Iron-Sequestering Anti-infective DIBI In Vitro and in Experimental Pneumonia in Mice.

Acinetobacter baumannii is a major cause of nosocomial infections especially hospital-acquired pneumonia. This bacterium readily acquires antibiotic resistance traits and therefore, new treatment alternatives are urgently needed. The virulence of A. baumannii linked to iron acquisition suggests a potential for new anti-infectives that target its iron acquisition. DIBI, a 3-hydroxypyridin-4-one chelator, is a purpose-designed, iron-sequestering antimicrobial that has shown promise for treating microbial infection. DIBI was investigated for its in vitro and in vivo activities against clinical A. baumannii isolates. DIBI was inhibitory for all isolates tested with very low MICs (2 µg/ml, equivalent to 0.2 µM), i.e., at or below the typical antibiotic MICs reported for antibiotic-sensitive strains. DIBI inhibition is Fe specific, and it caused an iron-restricted bacterial physiology that led to enhanced antibiotic killing by several discrete antibiotics. DIBI also strongly suppressed recovery growth of the surviving population following antibiotic exposure. A low intranasal dose (11 µmol/kg) of DIBI after intranasal challenge with hypervirulent ciprofloxacin (CIP)-resistant A. baumannii LAC-4 significantly reduced bacterial burdens in mice, and DIBI also suppressed the spread of the infection to the spleen. Treatment of infected mice with CIP alone (20 mg/kg, equivalent to 60 µmol/kg) was ineffective given LAC-4's CIP resistance, but if combined with DIBI, the treatment efficacy improved significantly. Our evidence suggests that DIBI restricts host iron availability to A. baumannii growing in the respiratory tract, bolstering the host innate iron restriction mechanisms. DIBI has potential as a sole anti-infective or in combination with conventional antibiotics for the treatment of A. baumannii pneumonia.

Acinetobacter baumannii can be transferred from contaminated nitrile examination gloves to polypropylene plastic surfaces.

BACKGROUND: Several observational studies suggest that gloves of health care workers are major routes of multidrug-resistant Acinetobacter baumannii transmission. However, limited experimental data are available assessing Acinetobacter transmission from gloves to environmental surfaces. This study determined whether A baumannii was easily transferred from nitrile gloves to polypropylene plastic compared with other gram-negative bacteria that cause health care-associated infections in laboratory-controlled experiments. METHODS: Gloved fingerpad-to-fomite transfer efficiency was determined for drug-resistant and -sensitive strains of A baumannii, Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa. RESULTS: Only A baumannii transferred from gloves to fomites 3 minutes after the bacterial transfer event. Transfer efficiency of A baumannii was 0.1%-33% at that time point. DISCUSSION: Bacterial transfer from contaminated gloves to the hospital environment may be related to the type of contaminating bacteria, inoculated bacterial level, fomites, and glove materials. Therefore, it is important to need a comprehensive assessment of the transfer efficiency. CONCLUSIONS: A baumannii can transfer easily from nitrile gloves to fomite compared with other gram-negative bacteria that cause health care-associated infections. These findings support data from previous observational studies that gloves of health care workers can be major routes of A baumannii transmission in clinical settings.

Plasmid profiles among some ESKAPE pathogens in a tertiary care centre in south India.

Background & objectives: Plasmid has led to increase in resistant bacterial pathogens through the exchange of antimicrobial resistance (AMR) genetic determinants through horizontal gene transfer. Baseline data on the occurrence of plasmids carrying AMR genes are lacking in India. This study was aimed to identify the plasmids associated with AMR genetic determinants in ESKAPE pathogens. Methods: A total of 112 ESKAPE isolates including Escherichia coli (n=37), Klebsiella pneumoniae (n=48, including 7 pan-drug susceptible isolates), Acinetobacter baumannii (n=8), Pseudomonas aeruginosa (n=1) and Staphylococcus aureus (n=18) were analyzed in the study. Isolates were screened for antimicrobial susceptibility and whole genome sequencing of isolates was performed using Ion Torrent (PGM) sequencer. Downstream data analysis was done using PATRIC, ResFinder, PlasmidFinder and MLSTFinder databases. All 88 whole genome sequences (WGS) were deposited at GenBank. Results: Most of the study isolates showed resistant phenotypes. As analyzed from WGS, the isolates included both known and unknown sequence types. The plasmid analysis revealed the presence of single or multiple plasmids in the isolates. Plasmid types such as IncHI1B(pNDM-MAR), IncFII(pRSB107), IncFIB(Mar), IncFIB(pQil), IncFIA, IncFII(K), IncR, ColKP3 and ColpVC were present in K. pneumoniae. In E. coli, IncFIA, IncFII, IncFIB, Col(BS512), IncL1, IncX3 and IncH were present along with other types. S. aureus harboured seven different plasmid groups pMW2 (rep 5), pSAS1 (rep 7), pDLK1 (rep 10), pUB110 (rep US12), Saa6159 (rep 16), pKH12 (rep 21) and pSA1308 (rep 21). The overall incidence of IncF type plasmids was 56.5 per cent followed by Col type plasmids 18.3 per cent and IncX 5.3 per cent. Other plasmid types identified were <5 per cent. Interpretation & conclusions: Results from the study may serve as a baseline data for the occurrence of AMR genes and plasmids in India. Information on the association between phenotypic and genotypic expression of AMR was deciphered from the data. Further studies on the mechanism of antibiotic resistance dissemination are essential for enhancing clinical lifetime of antibiotics.

Risk Factors for Mortality in Children with Acinetobacter baumannii Bacteremia in South Korea: The Role of Carbapenem Resistance.

Aims: Acinetobacter baumannii has become an important nosocomial pathogen that causes invasive infections. We conducted a retrospective study to evaluate the risk factors for mortality due to A. baumannii bacteremia in children. Materials and Methods: We reviewed data from Seoul National University Children's Hospital from 2002 to 2013 for children with A. baumannii bacteremia, including age, gender, underlying disease, associated site of infection, duration of hospitalization, presence of neutropenia, and antibiotic susceptibility data. The outcome measures were the 7- and 30-day mortality rates. Results: Among 74 A. baumannii bacteremia cases, 35.1% were carbapenem nonsusceptible. Common comorbidities were malignancy or hematologic diseases (28.4%), followed by gastrointestinal/hepatobiliary diseases (21.6%). A total of 47.3% of patients had isolated bacteremia, and in 33.8% of patients, pneumonia accompanied bacteremia. The mortality rates were 18.9% at 7 days and 35.1% at 30 days. The significant associated factors for 30-day mortality were carbapenem nonsusceptibility (adjusted hazard ratio [aHR]: 1.28, 95% confidence interval [CI]: 1.10-11.82, p = 0.034), neutropenia (aHR: 1.68, 95% CI: 1.60-18.03, p = 0.007), and prior intensive care unit (ICU) admission (aHR: 1.15, 95% CI: 1.03-9.73, p = 0.045). The mortality rate among neutropenic patients with inappropriate empirical antibiotics was higher than that among patients with appropriate empirical antibiotics (90.1% vs. 33.3%, p = 0.031). Conclusions: We identified carbapenem nonsusceptibility, neutropenia, and prolonged ICU stay as independent risk factors for mortality due to A. baumannii bacteremia in children. An early administration of appropriate antibiotics should be enacted, especially in patients with neutropenia.