Molecular Epidemiology and Clinical Impact of Acinetobacter calcoaceticus-baumannii Complex in a Belgian Burn Wound Center

Comparing antibiotic resistance and virulence profiles of Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas aeruginosa from environmental and clinical settings

Antibiotic resistance and virulence profiles of Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas aeruginosa, isolated from water sources collected in informal settlements, were compared to clinical counterparts. Cluster analysis using repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR) indicated that, for each respective species, low genetic relatedness was observed between most of the clinical and environmental isolates, with only one clinical P. aeruginosa (PAO1) and one clinical K. pneumoniae (P2) exhibiting high genetic similarity to the environmental strains. Based on the antibiograms, the clinical E. faecium Ef CD1 was extensively drug resistant (XDR); all K. pneumoniae isolates (n = 12) (except K. pneumoniae ATCC 13883) were multidrug resistant (MDR), while the P. aeruginosa (n = 16) isolates exhibited higher susceptibility profiles. The tetM gene (tetracycline resistance) was identified in 47.4 % (n = 6 environmental; n = 3 clinical) of the E. faecium isolates, while the blaKPC gene (carbapenem resistance) was detected in 52.6 % (n = 7 environmental; n = 3 clinical) and 15.4 % (n = 2 environmental) of the E. faecium and K. pneumoniae isolates, respectively. The E. faecium isolates were predominantly poor biofilm formers, the K. pneumoniae isolates were moderate biofilm formers, while the P. aeruginosa isolates were strong biofilm formers. All E. faecium and K. pneumoniae isolates were gamma (γ)-haemolytic, non-gelatinase producing (E. faecium only), and non-hypermucoviscous (K. pneumoniae only), while the P. aeruginosa isolates exhibited beta (β)-haemolysis and produced gelatinase. The fimH (type 1 fimbriae adhesion) and ugE (uridine diphosphate galacturonate 4-epimerase synthesis) virulence genes were detected in the K. pneumoniae isolates, while the P. aeruginosa isolates possessed the phzM (phenazine production) and algD (alginate biosynthesis) genes. Similarities in antibiotic resistance and virulence profiles of environmental and clinical E. faecium, K. pneumoniae, and P. aeruginosa, thus highlights the potential health risks posed by using environmental water sources for daily water needs in low-and-middle-income countries.

Distinct mode of action of a highly stable, engineered phage lysin killing Gram-negative bacteria

IMPORTANCE

Engineered lysins are considered as highly promising alternatives for antibiotics. Our previous screening study using VersaTile technology identified 1D10 as a possible lead compound with activity against Acinetobacter baumannii strains under elevated human serum concentrations. In this manuscript, we reveal an unexpected mode of action and exceptional thermoresistance for lysin 1D10. Our findings shed new light on the development of engineered lysins, providing valuable insights for future research in this field.

Molecular Epidemiology of Clinical Carbapenem-Resistant Acinetobacter baumannii-calcoaceticus complex Isolates in Tertiary Care Hospitals in Java and Sulawesi Islands, Indonesia

Carbapenem-resistant Acinetobacter baumannii (A. baumannii)-calcoaceticus complex (CRAb-cc) is an important pathogen causing nosocomial infections worldwide; however, molecular epidemiology of the A. baumannii-calcoaceticus complex in Indonesian hospitals is scarce. This study aimed to determine the clonal relatedness of CRAb-cc in two tertiary care hospitals in Malang and Manado in Indonesia. The CRAb-cc isolates from routine clinical cultures in two tertiary care hospitals in Malang and Manado were identified using the Vitek2^® system (bioMérieux, Lyon, France). Multi-locus variable-number tandem-repeat analysis (MLVA) typing, multi-locus sequence typing (MLST), clonal complex (CC), and phylogenetic tree analysis were conducted for a subset of isolates. Seventy-three CRAb-cc isolates were collected. The CRAb-cc isolates were frequently found among lower-respiratory-tract specimens. We detected the MLVA type (MT) 1, MT3, and MT4 CRAB-cc isolates belonging to the sequence type (ST) 642, and CC1 was the predominant clone in this study. In conclusion, we identified the clonal relatedness of A. baumannii-calcoaceticus complex isolates in two tertiary care hospitals in Malang and Manado in Indonesia. Further study is required to investigate the clinical importance and distribution of ST642 in Indonesian hospitals for developing prevention and control measures.

Genotypic and phenotypic comparison of clinical and environmental Acinetobacter baumannii strains

The genotypic and phenotypic characteristics and antibiotic resistance (antibiogram) profiles of clinical (n = 13) and environmental (n = 7) Acinetobacter baumannii isolates were compared. Based on the Repetitive Extragenic Palindromic Sequence-based PCR (REP-PCR) analysis, the clinical and environmental A. baumannii isolates shared low genetic relatedness (∼60%). Multilocus sequence typing (MLST, Oxford scheme) indicated that the clinical A. baumannii were assigned to three sequence types (ST231, ST945 and ST848), while the environmental A. baumannii (excluding AB 14) were categorised into the novel ST2520. The majority of the clinical (excluding AB 5, CAB 11, CAC 37) and environmental (excluding AB 14 and AB 16) A. baumannii strains were then capable of phase variation with both the translucent (71.4%; 15/21) and opaque (95.2%; 20/21) colony phenotypes detected. The clinical isolates however, exhibited significantly (p < 0.05) higher biofilm formation capabilities (OD₅₇₀: 2.094 ± 0.497). Moreover, the clinical isolates exhibited significantly (p < 0.05) higher resistance to first line antibiotics, with 92.3% (12/13) characterised as extensively drug resistant (XDR), whereas environmental A. baumannii exhibited increased antibiotic susceptibility with only 57.1% (4/7) characterised as multidrug resistant (MDR). The environmental isolate AB 14 was however, characterised as XDR. In addition, only five clinical A. baumannii isolates exhibited colistin resistance (38.5%; 5/13). The current study highlighted the differences in the genotypic, phenotypic, and antibiotic resistance profiles of clinical and environmental A. baumannii. Moreover, the environmental strains were assigned to the novel ST2520, which substantiates the existence of this opportunistic pathogen in extra-hospital reservoirs.

The Specific Capsule Depolymerase of Phage PMK34 Sensitizes Acinetobacter baumannii to Serum Killing

The rising antimicrobial resistance is particularly alarming for Acinetobacter baumannii, calling for the discovery and evaluation of alternatives to treat A. baumannii infections. Some bacteriophages produce a structural protein that depolymerizes capsular exopolysaccharide. Such purified depolymerases are considered as novel antivirulence compounds. We identified and characterized a depolymerase (DpoMK34) from Acinetobacter phage vB_AbaP_PMK34 active against the clinical isolate A. baumannii MK34. In silico analysis reveals a modular protein displaying a conserved N-terminal domain for anchoring to the phage tail, and variable central and C-terminal domains for enzymatic activity and specificity. AlphaFold-Multimer predicts a trimeric protein adopting an elongated structure due to a long α-helix, an enzymatic β-helix domain and a hypervariable 4 amino acid hotspot in the most ultimate loop of the C-terminal domain. In contrast to the tail fiber of phage T3, this hypervariable hotspot appears unrelated with the primary receptor. The functional characterization of DpoMK34 revealed a mesophilic enzyme active up to 50 °C across a wide pH range (4 to 11) and specific for the capsule of A. baumannii MK34. Enzymatic degradation of the A. baumannii MK34 capsule causes a significant drop in phage adsorption from 95% to 9% after 5 min. Although lacking intrinsic antibacterial activity, DpoMK34 renders A. baumannii MK34 fully susceptible to serum killing in a serum concentration dependent manner. Unlike phage PMK34, DpoMK34 does not easily select for resistant mutants either against PMK34 or itself. In sum, DpoMK34 is a potential antivirulence compound that can be included in a depolymerase cocktail to control difficult to treat A. baumannii infections.

Acinetobactin-Mediated Inhibition of Commensal Bacteria by Acinetobacter baumannii

Acinetobacter baumannii is an important hospital-associated pathogen that causes antibiotic resistant infections and reoccurring hospital outbreaks. A. baumannii’s ability to asymptomatically colonize patients is a risk factor for infection and exacerbates its spread. However, there is little information describing the mechanisms it employs to colonize patients. A. baumannii often colonizes the upper respiratory tract and skin. Antibiotic use is a risk factor for colonization and infection suggesting that A. baumannii likely competes with commensal bacteria to establish a niche. To begin to investigate this possibility, we cocultured A. baumannii and commensal bacteria of the upper respiratory tract and skin. In conditions that mimic iron starvation experienced in the host, we observed that A. baumannii inhibits Staphylococcus epidermidis, Staphylococcus hominis, Staphylococcus haemolyticus and Corynebacterium striatum. Then using an ordered transposon library screen we identified the A. baumannii siderophore acinetobactin as the causative agent of the inhibition phenotype. Using mass spectrometry, we show that acinetobactin is released from A. baumannii under our coculture conditions and that purified acinetobactin can inhibit C. striatum and S. hominis. Together our data suggest that acinetobactin may provide a competitive advantage for A. baumannii over some respiratory track and skin commensal bacteria and possibly support its ability to colonize patients.

IMPORTANCE The ability of Acinetobacter baumannii to asymptomatically colonize patients is a risk factor for infection and exacerbates its clinical spread. However, there is minimal information describing how A. baumannii asymptomatically colonizes patients. Here we provide evidence that A. baumannii can inhibit the growth of many skin and upper respiratory commensal bacteria through iron competition and identify acinetobactin as the molecule supporting its nutritional advantage. Outcompeting endogenous commensals through iron competition may support the ability of A. baumannii to colonize and spread among patients.

Effective Strategies to Deal With Infection in Burn Patient

Treatment of bacterial infection is difficult. Treatment protocol of burned patient is hard. Furthermore, treatment in burned patients is accompanied with problems such as complexity in diagnosis of infection's agent, multiple infections, being painful, and involving with different organelles. There are different infections of Gram-positive and Gram-negative bacteria in burned patients. From important bacteria can be noted to Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus that have high range of morbidity and mortality. Treatment of those bacterial infections is extremely important. Hence, many studies about methods of treatment of bacterial infections have published. Herein, we have suggested practical methods for example ant virulence therapies, nanotechnology, vaccine, and photodynamic therapy in treatment of bacterial infections. Those methods have been done in many researches and had good effect.

Screening for Antimicrobial-Resistant Gram-negative bacteria in hospitalised patients, and risk of progression from colonisation to infection: Systematic review

BACKGROUND

Transmission of antimicrobial-resistant Gram-negative bacteria (AMR-GNB) among hospitalised patients can lead to new cases of carriage, infection and outbreaks, hence the need for early carrier identification. We aim to explore two key elements that may guide control policies for colonisation/infection in hospital settings: screening practices on admission to hospital wards and risk of developing infection from colonisation.

METHODS

We searched on PubMed, Scopus and Cochrane databases for studies published from 2010 up to 2021 reporting on adult patients hospitalised in high-income countries.

RESULTS

The search retrieved 11853 articles. After screening, 100 studies were included. Combining target patient groups and setting type, we identified six screening approaches. The most reported approach was all admitted patients to high-risk (HR) wards (49.4%). The overall prevalence of AMR-GNB was 13.8% (95%CI 9.3-19.0) with significant differences across regions and time. Risk of progression to infection among colonised patients was 11.0% (95%CI 8.0-14.3) and varied according to setting and pathogens' group (p value<0.0001), with higher values reported for Klebsiella species (18.1%; 95%CI 8.9-29.3).

CONCLUSIONS

While providing a comprehensive overview of the screening approaches, our study underlines the considerable burden of AMR-GNB colonisation and risk of progression to infection in hospitals by pathogen, setting and time.

Engineering a lysin with intrinsic antibacterial activity (LysMK34) with cecropin A enhances its antibacterial properties against Acinetobacter baumannii

Bacteriophage-encoded lysins are increasingly reported as alternatives to combat Acinetobacter baumannii infections for which limited therapeutic options are available. Some lysins such as LysMK34 have a C-terminal amphipathic helix allowing them to penetrate the otherwise impermeable outer membrane barrier. Another approach to kill Gram-negative pathogens with lysins relies on fusion of a peptide with outer membrane permeabilizing properties to the lysin. In this work, we aimed to leverage the intrinsic antibacterial activity of LysMK34 by fusing the peptide cecropin A to its N-terminus via a linker of three Ala-Gly repeats, resulting in eLysMK34. The engineered lysin has an improved antibacterial activity compared to the parental lysin LysMK34 in terms of minimum inhibitory concentration (0.45 - 1.2 μM), killing rate and killing extent. eLysMK34 has an at least two-fold increased activity against stationary-phase cells and the bactericidal effect becomes less dependent on the intracellular osmotic pressure. Particularly colistin-resistant strains become highly susceptible to eLysMK34 and enhanced antibacterial activity is observed in complement-deactivated human serum. These observations demonstrate that fusion of a lysin with intrinsic antibacterial activity with a selected outer membrane permeabilizing peptide is a useful strategy to further improve the in vitro antibacterial properties of such lysins. Importance Phage lysins are a new class of enzyme-based antibiotics that increasingly gain interest. Lysins kill cells through rapid degradation of the peptidoglycan layer, resulting in sudden osmotic lysis. Whereas Gram-positive bacteria are readily susceptible to the action of lysins, Gram-negative bacteria are naturally resistant as the outer membrane protects their peptidoglycan layer. This work reveals that fusing an outer membrane permeabilizing peptide to a lysin with intrinsic antibacterial activity results in a superior lysin that shows improved robustness in its antibacterial activity, including against the most worrisome colistin-resistant strains A. baumannii.

The role of phage therapy in burn wound infection management: advantages and pitfalls

Burn wound infections are often the source of bacteria responsible for systemic infections, including bloodstream infections and pneumonia that ultimately can result in multisystem organ failure and death. Any rapid change in the burn wound appearance or the clinical condition of the burn patient may herald burn wound infection or sepsis. The revival of phage therapy, either in single mode or in combination with conventional antibiotics may represent a valuable alternative, to treat specific bacterial infections such as burn wound infections, including those caused by multidrug resistant organisms. This systematic review addresses the: a) general characteristics of bacteriophages; b) activity of bacteriophages versus conventional antibiotics; c) activity of bacteriophages against biofilms; d) bacteriophage administration; and e) use of bacteriophages in burn wound infections. Although several scientific organizations/societies recognized that phage therapy could be of key value in modern wound care, specific aspects are critical for a burn surgeon and might represent pitfalls discouraging phage therapy adoption in burn wound management; in particular, the unavailability of consensual therapeutic guidelines/regulatory policies and the lack of laboratorial support that might be predictive of its efficacy. The availability of a product/formulation convenient to use, with adequate stability and shelf half-life is also a key condition.

Treatment of patients with serious infections due to carbapenem-resistant Acinetobacter baumannii: How viable are the current options?

This review critically appraises the published microbiologic and clinical data on the treatment of patients with carbapenem-resistant Acinetobacter baumannii infections. Despite being recognized as an urgent threat pathogen by the CDC and WHO, optimal treatment of patients with serious CRAB infections remains ill-defined. Few commercially available agents exhibit reliable in vitro activity against CRAB. Historically, polymyxins have been the most active agents in vitro, though interpretations of susceptibility data are difficult given issues surrounding MIC testing methodologies and lack of correlation between MICs and clinical outcomes. Most available preclinical and clinical data involve use of polymyxins, tetracyclines, and sulbactam, alone and in combination. As the number of viable treatment options is limited, combination therapy with a polymyxin is often used for patients with CRAB infections, despite the significant risk of nephrotoxicity. However, no treatment regimen has been found to reduce mortality, which exceeds 40% across most studies, or substantially improve clinical response. While some newer agents, such as eravacycline and cefiderocol, have demonstrated in vitro activity, clinical efficacy has not been fully established. New agents with clinically relevant activity against CRAB isolates and favorable toxicity profiles are sorely needed.

Efficacy of Infection Control Measures in Managing Outbreaks of Multidrug-Resistant Organisms in Burn Units

BACKGROUND

Multidrug-resistant organisms (MDROs) pose a significant threat to severe burn victims and represents a clear epidemic hazard in burn units. Several infection control measures have been implemented to control and manage the outbreaks of MDRO. The efficiency of those measures, however, remains controversial and an area of debate. A systematic review was conducted to evaluate the efficacy of infection control measures and the necessity of closing burn units in dealing with MDRO outbreaks.

METHODS

Peer-reviewed articles were identified using PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases, focusing on infection control measures to manage MDRO outbreaks in burn units.

RESULTS

Twenty-one studies that reported MDRO outbreaks in burn units met the inclusion criteria. The outbreaks were successfully controlled with interventions in 17 units (81%), partially controlled in 1 unit (4.7%), and uncontrolled in 3 units (14.3%). Infection control measures were implemented by screening patient (19 units), screening health care worker (17 units), obtaining environmental cultures (16 units), providing ongoing staff education (13 units), cohort or isolation (17 units), preemptive barrier precautions (10 units), improving hand hygiene (15 units), and enhanced cleaning and environmental disinfection (17 units). Closure of burn units occurred in 8 units, with outbreaks controlled in 6 of the units (75%). The reasons for unit closure include decontamination (4 units; 50%), outbreak investigation (1 unit; 12.5%), and uncontrolled outbreaks (3 units; 37.5%). The incidence of infection was significantly decreased in 4 units after the closure but rose again after reopening in 1 of the units. In 3 units, the spread was halted by other control measures, including change of hydrotherapy facilities, identification of staff transmission, and unit structure remodeling.

CONCLUSIONS

Proper infection control measures play an important role in managing MDRO outbreaks in burn units. Temporary closure of burn units may be necessary to control the spread of nosocomial, and this option should be considered when other measures are ineffective.

Surgical Site Infection Following Caesarean Section by Acinetobacter Species: A Report from a Hyperendemic Setting in the Brazilian Amazon Region

Surgical site infection (SSI) following caesarean section is associated with increased morbidity, mortality, and significant health care costs. This study evaluated the epidemiological, clinical, and microbiological features of Acinetobacter spp. in women with SSIs who have undergone caesarean section at a referral hospital in the Brazilian Amazon region. This study included 69 women with post-caesarean SSI by Acinetobacter spp. admitted to the hospital between January 2012 and May 2015. The 69 Acinetobacter isolates were subjected to molecular species identification, antimicrobial susceptibility testing, detection of carbapenemase-encoding genes, and genotyping. The main complications of post-caesarean SSI by Acinetobacter were inadequate and prolonged antibiotic therapy, sepsis, prolonged hospitalization, and re-suture procedures. A. baumannii, A. nosocomialis and A. colistiniresistens species were identified among the isolates. Carbapenem resistance was associated with OXA-23-producing A. baumannii isolates and IMP-1-producing A. nosocomialis isolate. Patients with multidrug-resistant A. baumannii infection showed worse clinical courses. Dissemination of persistent epidemic clones was observed, and the main clonal complexes (CC) for A. baumannii were CC231 and CC236 (Oxford scheme) and CC1 and CC15 (Pasteur scheme). This is the first report of a long-term Acinetobacter spp. outbreak in women who underwent caesarean section at a Brazilian hospital. This study demonstrates the impact of multidrug resistance on the clinical course of post-caesarean infections.

CRISPR-based subtyping to track the evolutionary history of a global clone of Acinetobacter baumannii

Acinetobacter baumannii global clone 1 (GC1) is the second most common clone in the global population of A. baumannii isolates and a key cause of hospital-acquired infections. In this study, comparative analysis of the clustered regularly interspaced short palindromic repeats (CRISPR)-based sequence types (CST) was performed to determine the genetic relatedness and track patterns of descent among 187 GC1 isolates, as a complement to the evolutionary inferences from their multilocus sequence types and genome-wide single nucleotide polymorphism (SNP)-based phylogeny. The CST2 cluster, CST2 and all the CSTs descending from CST2, corresponded to GC1 lineage 1. This cluster included 143 of the 187 isolates showing a prevalent geographical distribution worldwide. A well-demarcated group of 13 CSTs, accounting for 33 of the 187 isolates, corresponded to GC1 lineage 2. All the CSTs of this group were characterized by the absence of spacer Ab-18. Many of the GC1 lineage 2 isolates had an epidemiological link to the Middle East and/or were obtained in military healthcare facilities. GC1 lineage 3 was a novel lineage that has so far been limited to Afghanistan, Pakistan and India. Diversification of A. baumannii GC1 into lineages and clades has probably been related to a dynamic expansion after passing a migration bottleneck to enter the hospital environment. We conclude that CRISPR-based subtyping is a convenient method to trace the evolutionary history of particular bacterial clones, such as A. baumannii GC1.

Lysin LysMK34 of Acinetobacter baumannii Bacteriophage PMK34 Has a Turgor Pressure-Dependent Intrinsic Antibacterial Activity and Reverts Colistin Resistance

The prevalence of extensively and pandrug-resistant strains of Acinetobacter baumannii leaves little or no therapeutic options for treatment for this bacterial pathogen. Bacteriophages and their lysins represent attractive alternative antibacterial strategies in this regard. We used the extensively drug-resistant A. baumannii strain MK34 to isolate the bacteriophage PMK34 (vB_AbaP_PMK34). This phage shows fast adsorption and lacks virulence genes; nonetheless, its narrow host spectrum based on capsule recognition limits broad application. PMK34 is a Fri1virus member of the Autographiviridae and has a 41.8-kb genome (50 open reading frames), encoding an endolysin (LysMK34) with potent muralytic activity (1,499.9 ± 131 U/μM), a typical mesophilic thermal stability up to 55°C, and a broad pH activity range (4 to 10). LysMK34 has an intrinsic antibacterial activity up to 4.8 and 2.4 log units for A. baumannii and Pseudomonas aeruginosa strains, respectively, but only when a high turgor pressure is present. The addition of 0.5 mM EDTA or application of an osmotic shock after treatment can compensate for the lack of a high turgor pressure. The combination of LysMK34 and colistin results in up to 32-fold reduction of the MIC of colistin, and colistin-resistant strains are resensitized in both Mueller-Hinton broth and 50% human serum. As such, LysMK34 may be used to safeguard the applicability of colistin as a last-resort antibiotic.IMPORTANCE A. baumannii is one of the most challenging pathogens for which development of new and effective antimicrobials is urgently needed. Colistin is a last-resort antibiotic, and even colistin-resistant A. baumannii strains exist. Here, we present a lysin that sensitizes A. baumannii for colistin and can revert colistin resistance to colistin susceptibility. The lysin also shows a strong, turgor pressure-dependent intrinsic antibacterial activity, providing new insights in the mode of action of lysins with intrinsic activity against Gram-negative bacteria.

Antibiogram, Prevalence of OXA Carbapenemase Encoding Genes, and RAPD-Genotyping of Multidrug-Resistant Acinetobacter baumannii Incriminated in Hidden Community-Acquired Infections

Acinetobacter spp. has gained fame from their ability to resist difficult conditions and their constant development of antimicrobial resistance. This study aimed to investigate the prevalence, susceptibility testing, OXA carbapenemase-encoding genes, and RAPD-genotyping of multidrug resistant Acinetobacter baumannii incriminated in hidden community-acquired infections in Egypt. The antimicrobial susceptibility testing was assessed phenotypically using Kirby–Bauer disk diffusion method. Also, Modified-Hodge test (MHT) was carried out to detect the carbapenemases production. Multiplex-PCR was used to detect the carbapenemase-encoding genes. Furthermore, the genetic relationship among the isolated strains was investigated using RAPD fingerprinting. The bacteriological examination revealed that, out of 200 Gram-negative non-fermentative isolates, 44 (22%) were identified phenotypically and biochemically as Acinetobacter spp. and 23 (11.5%) were molecularly confirmed as A.baumannii. The retrieved A.baumannii strains were isolated from urine (69%), sputum (22%), and cerebrospinal fluid (csf) (9%). The isolated A. baumannii strains exhibited multidrug resistance and the production rates of carbapenemases were 56.5, 60.9, and 78.3% with meropenem, imipenem, and ertapenem disks, respectively. The bla_OXA-24-like genes were the most predominant among the tested strains (65.2%), followed by bla_OXA-23 (30.4%) and bla_OXA-58 (17.4%), in addition, the examined strains are harbored IMP, VIM, and NDM genes with prevalence of 60.9, 43.5, and 13%, respectively, while KPC and GES genes were not detected. RAPD-PCR revealed that the examined strains are clustered into 11 different genotypes at ≥90% similarity. Briefly, to the best of our knowledge, this study is the first report concerning community-associated A. baumannii infections in Egypt. The high prevalence of hidden multidrug-resistant (MDR) and extensively drug-resistant (XDR) A.baumannii strains associated with non-hospitalized patients raises an alarm for healthcare authorities to set strict standards to control the spread of such pathogens with high rates of morbidity and mortality.

A VersaTile-driven platform for rapid hit-to-lead development of engineered lysins

Health care authorities are calling for new antibacterial therapies to cope with the global emergence of antibiotic-resistant bacteria. Bacteriophage-encoded lysins are a unique class of antibacterials with promising (pre)clinical progress. Custom engineering of lysins allows for the creation of variants against potentially any bacterial pathogen. We here present a high-throughput hit-to-lead development platform for engineered lysins. The platform is driven by VersaTile, a new DNA assembly method for the rapid construction of combinatorial libraries of engineered lysins. We constructed approximately 10,000 lysin variants. Using an iterative screening procedure, we identified a lead variant with high antibacterial activity against Acinetobacter baumannii in human serum and an ex vivo pig burn wound model. This generic platform could offer new opportunities to populate the preclinical pipeline with engineered lysins for diverse (therapeutic) applications.

Isolation, identification and characterisation of an emerging fish pathogen, Acinetobacter pittii, from diseased loach (Misgurnus anguillicaudatus) in China

Although members of the genus Acinetobacter have emerged as important nosocomial pathogens causing severe human infections, there are few reports about their occurrence as fish pathogens. In this study, five bacterial strains were isolated from diseased loach (Misgurnus anguillicaudatus) cultured in a farm in China. The diseased loach displayed shedding of skin mucus and many petechial haemorrhages all over the body. Based on sequence analyses of 16S rRNA and rpoB genes, the isolates were identified as Acinetobacter pittii. An experimental infection assay confirmed their pathogenicity to loach. The results of artificial infection in zebrafish (Barchydanio rerio) and nematode (Caenorhabditis elegans) suggested that, as well as loach, these A. pittii isolates are pathogenic and highly virulent to these organisms. Multilocus sequence typing analysis revealed that all the isolates belong to sequence type (ST) 839, which may be the dominant clone causing fish disease and exhibits a close phylogenetic relationship with ST396 from human clinical samples in Korea or Taiwan China. This is the first report demonstrating that A. pittii is an emerging causal agent of mass mortality in loach and poses significant risks to fish culturing besides causing human clinical infection worldwide.

Triclosan Alters Microbial Communities in Freshwater Microcosms

The effect of triclosan on microbial communities that are found in soil and sediments is well documented. However, little is known regarding the possible effects of triclosan on microbial communities that are present in the column of freshwater streams as the antimicrobial is released from sediments or from water sewage outflow. We show that a concentration of triclosan as low as 1 ng/L decreases richness and evenness in freshwater microbial communities growing in the water column while using controlled experimental microcosms. Crucially, the decrease in evenness that was observed in the microbial communities was due to the selection of bacteria commonly associated with human activity, such as Acinetobacter, Pseudomonas, and Rhodobacter, as opposed to an increase in Cyanobacteria, as previously suggested. Finally, our results demonstrate that higher concentrations of triclosan comparable to heavily polluted environments can also impact the overall phylogenetic structure and community composition of microbial communities. Understanding the impact of triclosan on these microbial populations is crucial from a public health perspective as human populations are more often exposed to microbial communities that are present in the water column via recreative use.

Clinical characteristics and outcomes of community and hospital-acquired Acinetobacter baumannii bacteremia

PURPOSE

We aimed to characterize clinical manifestations of the patients with bacteremia due to community-acquired Acinetobacter baumannii and evaluate the outcomes of these patients.

METHODS

We conducted a retrospective study to include adult patients with A. baumannii bacteremia and then classified them into two groups: community-acquired A. baumannii bacteremia and hospital-acquired A. baumannii bacteremia. Characteristics and outcomes between 2 groups were compared. The Galleria mellonella infection survival model was used to determine the virulence of A. baumannii in these 2 groups.

RESULTS

There were 63 patients with A. baumannii bacteremia: 21 patients with community-acquired (CA) bacteremia and 42 patients with hospital-acquired (HA) bacteremia. Three patients with CA bacteremia were excluded due to healthcare-associated risks of infection. The remaining 18 patients with CA bacteremia had carbapenem-susceptible A. baumannii (CA-CSAB). Among the 42 patients with HA bacteremia, 11 patients had carbapenem-susceptible A. baumannii (HA-CSAB) and 31 patients had carbapenem-resistant A. baumannii (HA-CRAB). The 30-day mortality rates of those with CA-CSAB did not differ from those with HA-CSAB bacteremia but were significantly lower than those with HA-CRAB (p = 0.003). The factors influencing 30-day mortality were infection with CRAB (p = 0.004), appropriate empirical antimicrobial therapy (p = 0.002), and higher Acute Physiology and Chronic Health Evaluation II score (p < 0.001). The G. mellonella assay showed no differences in survival rates among CA-CSAB, HA-CSAB, and HA-CRAB.

CONCLUSIONS

Patients with bacteremia due to CA-CSAB and HA-CSAB had similar outcomes. Similar virulences of CA-CSAB and HA-CSAB were confirmed with the G. mellonella infection model.

Bio-detoxification Bacteria Isolated from Dye-Polluted Soils Promote Lactic Acid Production from Ammonia Pretreated Corn Stover

Agro-stovers are the most abundant substrates for producing lactic acid, which has great potential application in the production of biodegradable and biocompatible polylactic acid polymers. However, chemical pretreatments on agro-stovers generate inhibitors that repress the subsequent lactic acid fermentation. In this study, three bacterial strains (Enterococcus faecalis B101, Acinetobacter calcoaceticus C1, and Pseudomonas aeruginosa CS) isolated from dye-polluted soils could utilize phenolic inhibitor mimics (vanillin, 4- hydroxybenzaldehyde, or syringaldehyde) from alkaline pretreated corn stovers as a sole carbon source. Lactic acid titer increased from 27.42 g/L (Bacillus coagulans LA204 alone) to 44.76 g/L (CS and LA204) using 50 g/L glucose with 1 g/L 4-hydroxybenzaldehyde added. Lactic acid production from 50 g/L ammonia pretreated corn stover was increased nearly twofold by inoculating phenolic degradation bacteria and lactic acid bacteria (C1& Lactobacillus pentosus FL0421). In the control (FL0421 alone), only 16.98 g/L of lactic acid was produced. The isolated and identified strains degraded the phenolic compounds and increased the lactic acid production from glucose and ammonia pretreated corn stover. These characteristics of the strains support industrial application with efficient in situ detoxification of phenolic compounds during lactic acid production from agro-stovers using simultaneous saccharification and fermentation (SSF).

Crude Oil Degrading Fingerprint and the Overexpression of Oxidase and Invasive Genes for n-hexadecane and Crude Oil Degradation in the Acinetobacter pittii H9-3 Strain

A crude oil-degrading bacterium named strain H9-3 was isolated from crude oil contaminated soil in the Northeastern area of China. Based on its morphological characteristics and 16S rDNA sequence analysis, strain H9-3 is affiliated to Acinetobacter pittii in the group of Gammaproteobacteria. The strain was efficient in removing 36.8% of the initial 10 g·L−1 of crude oil within 21 days. GC-MS was performed and a preference was shown for n-C10, n-C11, i-C14, i-C17, i-C34, n-C12, n-C13, n-C14, n-C27, n-C32 and i-C13, over n-C16, n-C18–C22, n-C24–n-C31, and n-C36. This can be regarded as the specific fingerprint for crude oil degradation by strain H9-3 of Acinetobacter pittii. In addition to crude oil, it was shown that soybean oil and phenols can be utilized as carbon sources by strain H9-3. It was also shown that aniline and α-naphthol cannot be utilized for growth, but they can be tolerated by strain H9-3. Methylbenzene was neither utilized nor tolerated by strain H9-3. Although n-hexadecane was not preferentially consumed by strain H9-3, during culture with crude oil, it could be utilized for growth when it is the sole carbon source. The degradation of some branched alkanes (i-C14, i-C17 and i-C34) and the preferential degradation of crude oil over phenols could be used as a reference for distinguishing A. pittii from A. calcoaceticus. The difference in gene expression was very significant and was induced by diverse carbon sources, as shown in the qRT-PCR results. The oxidation and adhesion events occurred at high frequency during alkane degration by Acinetobacter pittii strain H9-3 cells.

How to: molecular investigation of a hospital outbreak

BACKGROUND

Studying hospital outbreaks by using molecular tools, i.e. synthesizing the molecular epidemiology data to its appropriate clinical-epidemiologic context, is crucial in order to identify infection source, infer transmission dynamics, appropriately allocate prevention resources and implement control measures. Whole-genome sequencing (WGS) of pathogens has become the reference standard, as it is becoming more accessible and affordable. Consequently, sequencing of the full pathogen genome via WGS and major progress in fit-for-purpose genomic data analysis tools and interpretation is revolutionizing the field of outbreak investigations in hospitals. Metagenomics is an additional evolving field that might become commonly used in the future for outbreak investigations. Nevertheless, practitioners are frequently limited in terms of WGS or metagenomics, especially for local outbreak analyses, as a result of costs or logistical considerations, reduced or lack of locally available resources and/or expertise. As a result, traditional approaches, including pulsed-field gel electrophoresis, repetitive-element palindromic PCR and multilocus sequence typing, along with other typing methods, are still widely used.

AIMS

To provide practitioners with evidenced-based action plans for usage of the various typing techniques in order to investigate the molecular epidemiology of nosocomial outbreaks, of clinically significant pathogens in acute-care hospitals.

SOURCES

PubMed search with relevant keywords along with personal collection of relevant publications.

CONTENT

Representative case scenarios and critical review of the relevant scientific literature.

IMPLICATIONS

The review provides practical action plans to manage molecular epidemiologic investigations of outbreaks caused by clinically significant nosocomial pathogens, while prioritizing the use and timely integration of the various methodologies.

Prevalence and antimicrobial susceptibilities of Acinetobacter baumannii and non-baumannii Acinetobacters from Terengganu, Malaysia and their carriage of carbapenemase genes

A total of 153 non-repeat Acinetobacter spp. clinical isolates obtained in 2015 from Hospital Sultanah Nur Zahirah (HSNZ) in Terengganu, Malaysia, were characterized. Identification of the isolates at species level was performed by ribosomal DNA restriction analysis (ARDRA) followed by sequencing of the rpoB gene. The majority of the isolates (n=128; 83.7 %) were A. baumannii while the rest were identified as A. nosocomialis (n=16), A. calcoaceticus (n=5), A. soli (n=2), A. berezeniae (n=1) and A. variabilis (n=1). Multidrug resistance (MDR) was most prevalent in A. baumannnii (66.4 %) whereas only one non-baumannii isolate (A. nosocomialis) was MDR. The blaOXA-23 gene was the predominant acquired carbapenemase gene (56.2 %) and was significantly associated (P<0.001) with carbapenem resistance. However, no significant association was found for carbapenem resistance and isolates that contained the ISAba1-blaOXA-51 configuration.

Extensive colonization with carbapenemase-producing microorganisms in Romanian burn patients: infectious consequences from the Colectiv fire disaster

Health care of severe burn patients is highly specialized and may require international patient transfer. Burn patients have an increased risk of developing infections. Patients that have been hospitalized in countries where carbapenemase-producing microorganisms (CPMO) are endemic may develop infections that are difficult to treat. In addition, there is a risk on outbreaks with CPMOs in burn centers. This study underlines that burn patients may extensively be colonized with CPMOs, and it provides best practice recommendations regarding clinical microbiology and infection control. We evaluated CPMO-carriage and wound colonization in a burn patient initially treated in Romania, and transported to the Netherlands. The sequence types and acquired beta-lactamase genes of highly-resistant microorganisms were derived from next generation sequencing data. Next, we searched literature for reports on CPMOs in burn patients. Five different carbapenemase-producing isolates were cultured: two unrelated OXA-48-producing Klebsiella pneumoniae isolates, OXA-23-producing Acinetobacter baumanii, OXA-48-producing Enterobacter cloacae, and NDM-1-producing Providencia stuartii. Also, multi-drug resistant Pseudomonas aeruginosa isolates were detected. Among the sampling sites, there was high variety in CPMOs. We found 46 reports on CPMOs in burn patients. We listed the epidemiology of CPMOs by country of initial treatment, and summarized recommendations for care of these patients based on these reports and our study.

Predicting and managing sepsis in burn patients: current perspectives

Modern burn care has led to unprecedented survival rates in burn patients whose injuries were fatal a few decades ago. Along with improved survival, new challenges have emerged in the management of burn patients. Infections top the list of the most common complication after burns, and sepsis is the leading cause of death in both adult and pediatric burn patients. The diagnosis and management of sepsis in burns is complex as a tremendous hypermetabolic response secondary to burn injury can be superimposed on systemic infection, leading to organ dysfunction. The management of a septic burn patient represents a challenging scenario that is commonly encountered by providers caring for burn patients despite preventive efforts. Here, we discuss the current perspectives in the diagnosis and treatment of sepsis and septic shock in burn patients.

Stability of bacteriophages in burn wound care products

Bacteriophages could be used along with burn wound care products to enhance antimicrobial pressure during treatment. However, some of the components of the topical antimicrobials that are traditionally used for the prevention and treatment of burn wound infection might affect the activity of phages. Therefore, it is imperative to determine the counteraction of therapeutic phage preparations by burn wound care products before application in patients. Five phages, representatives of two morphological families (Myoviridae and Podoviridae) and active against 3 common bacterial burn wound pathogens (Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus aureus) were tested against 13 different products commonly used in the treatment of burn wounds. The inactivation of the phages was quite variable for different phages and different products. Majority of the anti-infective products affected phage activity negatively either immediately or in the course of time, although impact was not always significant. Products with high acidity had the most adverse effect on phages. Our findings demonstrate that during combined treatment the choice of phages and wound care products must be carefully defined in advance.

First report of cavitary pneumonia due to community-acquired Acinetobacter pittii, study of virulence and overview of pathogenesis and treatment

Background

Acinetobacter pittii is a nosocomial pathogen rarely involved in community-acquired infections. We report for the first time that A. pittii can be responsible for cavitary community-acquired pneumonia and study its virulence, and discuss its pathogenesis and treatment options.

Case presentation

A 45-year-old woman with a history of smoking and systemic lupus was admitted to Nimes University Hospital (France) with coughing and sputum lasting for three weeks. Thoracic CT scanner showed cavitary pneumonia. Broncho-alveolar lavage cultures found community-acquired Acinetobacter calcoaceticus-baumannii complex. The clinical outcome was favourable after twenty-one days of antimicrobial treatment by piperacillin/tazobactam and amikacin then cefepime. Multilocus sequence typing (MLST) analyses identified an A. pittii ST249. Despite the atypical clinical presentation with an unexpected partial destruction of lung parenchyma, we found very low virulence potential of the A. pittii strain with nematode killing assays and biofilm formation test. The median time required to kill 50% of the nematodes was 7 ± 0.3 days for A. pittii ST249, 7 ± 0.2 days for A. baumanii NAB ST2 and 8 ± 0.2 days for E. coli OP50, (p > 0,05). A. pittii ST249 showed significantly slower biofilm formation than A. baumanii NAB ST2: BFI = 8.83 ± 0.59 vs 3.93 ± 0.27 at 2 h (p < 0.0001), BFI = 6.3 ± 0.17 vs 1.87 ± 0.12 at 3 h (p < 0.0001) and BFI = 3.67 ± 0.41 vs 1.7 ± 0.06 after 4 h of incubation (p < 0.01).

Conclusions

Community-acquired A. pittii should be considered as possible cause of sub-acute cavitary pneumonia particularly in a smoking and/or immunocompromised patient despite its low virulence potential.

In vitro antibacterial activity of poly (amidoamine)-G7 dendrimer

BACKGROUND

Nano-scale dendrimers are synthetic macromolecules that frequently used in medical and health field. Traditional anibiotics are induce bacterial resistence so there is an urgent need for novel antibacterial drug invention. In the present study seventh generation poly (amidoamine) (PAMAM-G7) dendrimer was synthesized and its antibacterial activities were evaluated against representative Gram- negative and Gram-positive bacteria.

METHODS

PAMAM-G7 was synthesized with divergent growth method. The structural and surface of PAMAM-G7 were investigated by transmission electron microscopy, scanning electron microscope and fourier transform infrared. Pseudomonas. aeruginosa (n = 15), E. coli (n = 15), Acinetobacter baumanni (n = 15), Shigella dysenteriae (n = 15), Klebsiella pneumoniae (n = 10), Proteus mirabilis (n = 15), Staphylococcus aureus (n = 15) and Bacillus subtilis (n = 10) have been used for antibacterial activity assay. Additionally, representative standard strains for each bacterium were included. Minimum Inhibitory Concentration (MIC) was determined using microdilution method. Subsequently, Minimum Bactericidal Concentration (MBC) was determined by sub-culturing each of the no growth wells onto Mueller Hinton agar medium. The cytotoxicity of PAMAM-G7 dendrimer were evaluated in HCT116 and NIH 3 T3 cells by MTT assay.

RESULTS

The average size of each particle was approximately 20 nm. PAMAM-G7 was potentially to inhibit both Gram positive and gram negative growth. The MIC50 and MIC90 values were determined to be 2-4 μg/ml and 4-8 μg/ml, respectively. The MBC50 and MBC90 values were found to be 64-256 μg/ml and 128-256 μg/ml, respectively. The cytotoxity effect of dendrimer on HCT116 and NIH 3 T3 cells is dependent upon exposure time to and concentration of dendrimers. The most reduction (44.63 and 43%) in cell viability for HCT116 and NIH 3 T3 cells was observed at the highest concentration, 0.85 μM after 72 h treatmentm, respectively.

CONCLUSIONS

This study we conclude that PAMAM-G7 dendrimer could be a potential candidate as a novel antibacterial agent.

Carbapenem-resistant Acinetobacter pittii strain harboring blaOXA-72 from Brazil

In this study, we report the isolation of OXA-72-producing Acinetobacter pittii in Brazil. A carbapenem-resistant A. pittii strain was recovered from a hospitalized female patient from Espírito Santo, Southeastern Brazil. PCR screening and DNA sequencing allowed us to identify the presence of bla_OXA-72. We observed bla_OXA-72 in a ~11kb plasmid and flanked by XerC/XerD-binding sites.

Antibacterial activity of epigallocatechin-3-gallate (EGCG) and its synergism with β-lactam antibiotics sensitizing carbapenem-associated multidrug resistant clinical isolates of Acinetobacter baumannii

BACKGROUND

Infections caused by Acinetobacter baumannii were responsive to conventional antibiotic therapy. However, recently, carbapenem-associated multidrug resistant isolates have been reported worldwide and present a major therapeutic challenge. Epigallocatechin-3-Gallate (EGCG) extracted from green tea exhibits antibacterial activity.

PURPOSE

We evaluated the antibacterial activity of EGCG and possible synergism with antibiotics in carbapenem-associated multidrug resistant A. baumannii. A potential mechanism for synergism was also explored.

MATERIALS AND METHODS

Seventy clinical isolates of A. baumannii collected from geographically different areas were analyzed by minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EGCG. Checkerboard and time-killing assays were performed to exam the synergism between EGCG and antibiotics. The effects of EGCG on a multidrug efflux pump inhibitor (1-[1-naphthylmethyl] piperazine; NMP) and β-lactamase production were also examined in A. baumannii.

RESULTS

Sixty-three of 70 clinical isolates of A. baumannii carried carbapenemase-encoding genes with carbapenem-associated multidrug resistance. Levels of MIC and MBC of EGCG ranged from 64 to 512µg/ml and from 128 to ≥1024µg/ml, respectively among the clinical isolates. MIC₉₀ and MBC₈₆ levels were 256µg/ml and 512µg/ml of EGCG, respectively. Subinhibitory concentration of EGCG in combination with all antibiotics tested, including carbapenem, sensitized (MICs fall≤1.0µg/ml) all carbapenem-associated multidrug resistant isolates. Checkerboard and time-killing assays showed synergism between EGCG and meropenem (or carbenicillin) counted as fractional inhibitory concentration of < 0.5 and cell numbers' decrease per ml of >2log10 within 12h, respectively. EGCG significantly increased the effect of NMP but was unrelated to β-lactamase production in A. baumannii, suggesting EGCG may be associated with inhibition of efflux pumps.

CONCLUSION

Overall we suggest that EGCG-antibiotic combinations might provide an alternative approach to treat infections with A. baumannii regardless of antibiotic resistance.

Control of Multidrug-Resistant Gene Flow in the Environment Through Bacteriophage Intervention

The spread of multidrug-resistant (MDR) bacteria is an emerging threat to the environment and public wellness. Inappropriate use and indiscriminate release of antibiotics in the environment through un-metabolized form create a scenario for the emergence of virulent pathogens and MDR bugs in the surroundings. Mechanisms underlying the spread of resistance include horizontal and vertical gene transfers causing the transmittance of MDR genes packed in different host, which pass across different food webs. Several controlling agents have been used for combating pathogens; however, the use of lytic bacteriophages proves to be one of the most eco-friendly due to their specificity, killing only target bacteria without damaging the indigenous beneficial flora of the habitat. Phages are part of the natural microflora present in different environmental niches and are remarkably stable in the environment. Diverse range of phage products, such as phage enzymes, phage peptides having antimicrobial properties, and phage cocktails also have been used to eradicate pathogens along with whole phages. Recently, the ability of phages to control pathogens has extended from the different areas of medicine, agriculture, aquaculture, food industry, and into the environment. To avoid the arrival of pre-antibiotic epoch, phage intervention proves to be a potential option to eradicate harmful pathogens generated by the MDR gene flow which are uneasy to cure by conventional treatments.