Multidrug resistant Acinetobacter baumannii: a descriptive study in a city hospital

In-hospital areas with distinct maintenance and staff/patient traffic have specific microbiome profiles, functions, and resistomes

Hospitals are subject to strict microbial control. Stringent cleaning and confinement measures in hospitals lead to a decrease in microbial diversity, but an increase in resistance genes. Given the rise of antimicrobial resistances and healthcare-associated infections, understanding the hospital microbiome and its resistome is crucial. This study compared the microbiome and resistome at different levels of confinement (CL) within a single hospital. Using amplicon sequencing, shotgun metagenomics, and genome/plasmid reconstruction, we demonstrate that microbial composition differs in a stable way between the CLs and that the most restrictive confinement level CL1 had the lowest microbial but the highest functional diversity. This CL also exhibited a greater abundance of functions related to virulence, disease, defense, and stress response. Comparison of antibiotic resistance also showed differences among CLs in terms of the selection process and specific mechanisms for antimicrobial/antibiotic resistance. The resistances found in the samples of CL1 were mostly mediated via antibiotic efflux pumps and were mainly located on chromosomes, whereas in the other, less restrictive CL antibiotic resistances were more present on plasmids. This could be of particular importance for patient-related areas (CL2), as the potential spread of antibiotic resistances could be a major concern in this area. Our results show that there are differences in the microbiome and resistome even within a single hospital, reflecting room utilization and confinement. Since restrictive confinement selects for resistant microorganisms, strategies are required to deepen our understanding of dynamic processes of microbiome and resistome within hospital environments.

IMPORTANCE

Effective measures to combat antibiotic resistances and healthcare-associated infections are urgently needed, including optimization of microbial control. However, previous studies have indicated that stringent control can lead to an increase in the resistance capacities of microbiomes on surfaces. This study adds to previous knowledge by focusing on the conditions in a single hospital, resolving the microbiomes and their resistomes in three different confinement levels (CL): operating room, patient-related areas, and non-patient-related areas. We were able to identify stable key taxa; profiled the capacities of taxa, functions, and antimicrobial resistances (AMR); and reconstruct genomes and plasmids in each CL. Our results show that the most restrictive CL indeed had the highest functional diversity, but that resistances were mostly encoded on chromosomes, indicating a lower possibility of resistance spread. However, clever strategies are still required to strike a balance between microbial control and selective pressures in environments where patients need protection.

A Novel Dimeric Short Peptide Derived from α-Defensin-Related Rattusin with Improved Antimicrobial and DNA-Binding Activities

Rattusin, an α-defensin-related antimicrobial peptide isolated from the small intestine of rats, has been previously characterized through NMR spectroscopy to elucidate its three-dimensional structure, revealing a C2 homodimeric scaffold stabilized by five disulfide bonds. This study aimed to identify the functional region of rattusin by designing and synthesizing various short analogs, subsequently leading to the development of novel peptide-based antibiotics. The analogs, designated as F1, F2, F3, and F4, were constructed based on the three-dimensional configuration of rattusin, among which F2 is the shortest peptide and exhibited superior antimicrobial efficacy compared to the wild-type peptide. The central cysteine residue of F2 prompted an investigation into its potential to form a dimer at neutral pH, which is critical for its antimicrobial function. This activity was abolished upon the substitution of the cysteine residue with serine, indicating the necessity of dimerization for antimicrobial action. Further, we synthesized β-hairpin-like analogs, both parallel and antiparallel, based on the dimeric structure of F2, which maintained comparable antimicrobial potency. In contrast to rattusin, which acts by disrupting bacterial membranes, the F2 dimer binds directly to DNA, as evidenced by fluorescence assays and DNA retardation experiments. Importantly, F2 exhibited negligible cytotoxicity up to 515 μg/mL, assessed via hemolysis and MTT assays, underscoring its potential as a lead compound for novel peptide-based antibiotic development.

Antibiotic resistance genes associated with size-segregated bioaerosols from wastewater treatment plants: A review

The antibiotic-resistant pollution in size-segregated bioaerosols from wastewater treatment plants (WWTPs) is of increasing concern due to its public health risks, but an elaborate review is still lacking. This work overviewed the profile, mobility, pathogenic hosts, source, and risks of antibiotic resistance genes (ARGs) in size-segregated bioaerosols from WWTPs. The dominant ARG type in size-segregated bioaerosols from WWTPs was multidrug resistance genes. Treatment units that equipped with mechanical facilities and aeration devices, such as grilles, grit chambers, biochemical reaction tanks, and sludge treatment units, were the primary sources of bioaerosol antibiotic resistome in WWTPs. Higher enrichment of antibiotic resistome in particulate matter with an aerodynamic diameter of <2.5 μm, was found along the upwind-downwind-WWTPs gradient. Only a small portion of ARGs in inhalable bioaerosols from WWTPs were flanked by mobile genetic elements. The pathogens with multiple drug resistance had been found in size-segregated bioaerosols from WWTPs. Different ARGs or antibiotic resistant bacteria have different aerosolization potential associated with bioaerosols from various treatment processes. The validation of pathogenic antibiotic resistance bacteria, deeper investigation of ARG mobility, emission mechanism of antibiotic resistome, and development of treatment technologies, should be systematically considered in future.

Phenotypic and Genotypic Investigation of Carbapenem-Resistant Acinetobacter baumannii in Maharaj Nakhon Si Thammarat Hospital, Thailand

(1) Background: Acinetobacter baumannii is well known as a causative agent of severe hospital-acquired infections, especially in intensive care units. The present study characterised the genetic traits of biofilm-forming carbapenem-resistant A. baumannii (CRAB) clinical isolates. Additionally, this study determined the prevalence of biofilm-producing A. baumannii isolates from a tertiary care hospital and investigated the association of biofilms with the distribution of biofilm-related and antibiotic resistance-associated genotypes. (2) Methods: The 995 non-duplicate A. baumannii isolates were identified, and their susceptibilities to different antibiotics were determined using the disk diffusion method. Using the modified microtiter plate assay, the CRAB isolates were investigated for their biofilm formation ability. Hemolysin and protease activities were determined. CRABs were subjected to polymerase chain reaction (PCR) assays targeting blaVIM, blaNDM, blaIMP, blaOXA-23-like, blaOXA-24-like, blaOXA-51-like, csuE and pgaB genes. Individual CRAB isolates were identified for their DNA fingerprint by repetitive element sequence-based (REP)-PCR. (3) Results: Among all A. baumannii isolates, 172 CRABs were identified. The major antibiotic resistance gene among the CRAB isolates was blaOXA-51-like (100%). Ninety-nine isolates (57.56%) were biofilm producers. The most prevalent biofilm gene was pgaB (79.65%), followed by csuE (76.74%). Evidence of virulence phenotypes revealed that all CRAB exhibited proteolytic activity; however, only four isolates (2.33%) were positive for the hemolytic-producing phenotype. REP-PCR showed that 172 CRAB isolates can be divided into 36-DNA fingerprint patterns. (4) Conclusions: The predominance of biofilm-producing CRAB isolates identified in this study is concerning. The characterisation of risk factors could aid in controlling the continual selection and spreading of the A. baumannii phenotype in hospitals, thereby improving patient care quality.

Alteration of the Gut Microbiota in Missed Abortion

There is a symbiotic relationship between gut microbiota and human beings. Imbalance of the gut microbiota will cause pathological damages to humans. Although many risk factors are associated with missed abortion (MA), the pathological mechanism of it is still unclear. Here, we analyzed gut flora of the patients with MA by S16 high-throughput sequencing. The possible pathogenic mechanisms of the MA were explored. Fecal samples from 14 healthy controls and 16 MA patients were collected to do 16S rRNA gene high-throughput sequencing analysis. The abundance of the Bacteroidetes, Proteobacteria, Actinobacteria, Escherichia, Streptococcus_ Salivarius, and Lactobacillus was significantly reduced in the MA group, while, the abundance of the Klebsiella was significantly increased in the MA patients. The Ruminococcaceae and [Eubacterium]_coprostanoligenes_group were found only in the specimens of the MA patients. The Fabrotax function prediction analysis showed that four photosynthesis function bacteria (cyanobateria, oxygenic_photoautotrophy, photoautotrophy, and phototrophy) only existed in the MA group. In the analysis of the BugBase microbiome function prediction, the Escherichia of the MA group is significantly reduced compared to that of the healthy controls in the items of that Contains_Mobile_Elements, Facultatively_Anaerobic, Forms_Biofilms, Potentially_Pathogenic.png, Gram_Nagative, and Stress_Tolerant_relabundance. These alterations may affect the stability of the host's immune, neural, metabolic and other systems by interfering with the balance of the gut microbiota or by the metabolites of those bacteria, causing the MA. This study explored the possible pathogenic factors of the gut microbiota of the MA. The results provide evidence to figure out the pathogenesis of the MA.

Clinical Impact and Risk Factors of Intensive Care Unit-Acquired Nosocomial Infection: A Propensity Score-Matching Study from 2018 to 2020 in a Teaching Hospital in China

Purpose

Nosocomial infection (NI) is associated with poor prognosis. The present study assessed the clinical and microbiological characteristics of NI patients in the intensive care unit (ICU) and investigated the clinical impact and risk factors for NI in ICU patients.

Patients and Methods

An observational study was conducted in an adult general ICU. The electronic medical records of all patients admitted to the ICU for >2 days from 2018-2020 were analyzed retrospectively. Multivariate regression models were used to analyze the risk factors for NI in ICU patients. Propensity score-matching (PSM) was used to control the confounding factors between the case and control groups, thus analyzing the clinical impact of NIs.

Results

The present study included 2425 patient admissions, of which 231 (9.53%) had NI. Acinetobacter baumannii (33.0%) was the most common bacteria. Long-term immunosuppressive therapy, disturbance of consciousness, blood transfusion, multiple organ dysfunction syndromes (MODS), treatment with three or more antibiotics, mechanical ventilation (MV), tracheotomy, the urinary catheter (UC), nasogastric catheter, and central venous catheter (CVC) were risk factors for NI in the ICU patients. After PSM, patients with NI had a prolonged length of stay (LOS) in the ICU and hospital, significant hospitalization expenses (all p<0.001), increased mortality (p=0.027), and predicted mortality (p=0.007). The differences in the ICU and hospital LOSs among three pathogens were statistically significant (p<0.001); the results of the Escherichia coli infection group were lower than the other two pathogenic groups.

Conclusion

NI was associated with poor outcomes. The risk factors for NI identified in this study provided further insight into preventing NI.

A systematic review and meta-analysis for risk factor profiles in patients with resistant Acinetobacter baumannii infection relative to control patients

BACKGROUND

Acinetobacter baumannii is a major cause of nosocomial infections and high mortality rates. Evaluation of risk factors for such resistant infections may aid surveillance and diagnostic initiatives, as well as, can be crucial in early and appropriate antibiotic therapy.

OBJECTIVE

To identify the risk factors in patients with resistant A. baumannii infection with respect to controls.

METHODS

Prospective or retrospective cohort and case-control studies reporting the risk factors for resistant A. baumannii infection were collected through two data sources, MEDLINE/PubMed and OVID/Embase. Studies published in the English language were included while animal studies were excluded. The Newcastle-Ottawa Scale was used to assess the quality of studies. The odds ratio of developing antibiotic resistance in patients with A. baumannii infection was pooled using a random-effect model.

RESULTS

The results are based on 38 studies with 60878 participants (6394 cases and 54484 controls). A total of 28, 14, 25, and 11 risk factors were identified for multi-drug resistant (MDRAB), extensive-drug resistant (XDRAB), carbapenem-resistant (CRAB) and imipenem resistant A. baumannii infection (IRAB), respectively. In the MDRAB infection group, exposure to carbapenem (OR 5.51; 95% CI: 3.88-7.81) and tracheostomy (OR 5.01; 95% CI: 2.12-11.84) were identified with maximal pool odd's ratio. While previous use of amikacin (OR 4.94; 95% CI: 1.89-12.90) and exposure to carbapenem (OR 4.91; 95% CI: 2.65-9.10) were the foremost factors associated with developing CRAB infection. Further analysis revealed, mechanical ventilation (OR 7.21; 95% CI: 3.79-13.71) and ICU stay (OR 5.88; 95% CI: 3.27-10.57) as the most significant factors for XDRAB infection.

CONCLUSION

The exposure of carbapenem, amikacin (previous) and mechanical ventilation were the most significant risk factors for multidrug, extensive-drug, and carbapenem resistance in patients with A. baumannii infection respectively. These findings may guide to control and prevent resistant infections by identifying the patients at higher risk of developing resistance.

Acinetobacter nosocomialis Causes as Severe Disease as Acinetobacter baumannii in Northeast Thailand: Underestimated Role of A. nosocomialis in Infection

Infections by Acinetobacter species are recognized as a serious global threat due to causing severe disease and their high levels of antibiotic resistance. Acinetobacter baumannii is the most prevalent pathogen in the genus, but infection by Acinetobacter nosocomialis has been reported widely. Diagnosis of patients with A. baumannii infection is often misdiagnosed with other Acinetobacter species, especially A. nosocomialis. This study investigated whether there were significant differences in clinical outcomes between patients infected with A. baumannii versus A. nosocomialis in Northeast Thailand, and to characterize serological responses to infection with these pathogens. The results show that A. baumannii had higher levels of multidrug resistance. Despite this, clinical outcomes for infection with A. baumannii or A. nosocomialis were similar with mortalities of 33% and 36%, respectively. Both pathogens caused community-acquired infections (A. baumannii 35% and A. nosocomialis 29% of cases). Plasma from uninfected healthy controls contained IgG antibody that recognized both organisms, and infected patients did not show a significantly enhanced antibody response from the first week versus 2 weeks later. Finally, the patterns of antigen recognition for plasma IgG were similar for patients infected with A. baumannii or A. nosocomialis infection, and distinct to the pattern for patients infected with non-Acinetobacter. In conclusion, our data revealed that infection with A. nosocomialis was associated with a similarly high level of mortality as infection with A. baumannii, the high rate of community-acquired infection and antibodies in uninfected individuals suggesting that there is significant community exposure to both pathogens. IMPORTANCE Bacterial infections by Acinetobacter species are global threats due to their severity and high levels of antibiotic resistance. A. baumannii is the most common pathogen in the genus; however, infection by A. nosocomialis has also been widely reported but is thought to be less severe. In this study, we have prospectively investigated 48 reported cases of A. baumannii infection in Northeast Thailand, and characterized the serological responses to infection. We found that 14 (29%) of these infections were actually caused by A. nosocomialis. Furthermore, the incidence of antibiotic resistance among A. nosocomialis strains, APACHE II scores, and mortality for patients infected with A. nosocomialis were much higher than published data. Both A. baumannii and A. nosocomialis had unexpectedly mortality rates of over 30%, and both pathogens caused a high rate of community-acquired infections. Importantly, background antibodies in uninfected individuals suggest significant community exposure to both pathogens in the environment.

Sequence-Specific Electrochemical Genosensor for Rapid Detection of blaOXA-51-like Gene in Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) are phenotypically indistinguishable from the Acinetobacter calcoaceticus−A. baumannii (ACB) complex members using routine laboratory methods. Early diagnosis plays an important role in controlling A. baumannii infections and this could be assisted by the development of a rapid, yet sensitive diagnostic test. In this study, we developed an enzyme-based electrochemical genosensor for asymmetric PCR (aPCR) amplicon detection of the blaOXA-51-like gene in A. baumannii. A. baumanniiblaOXA-51-like gene PCR primers were designed, having the reverse primer modified at the 5′ end with FAM. A blaOXA-51-like gene sequence-specific biotin labelled capture probe was designed and immobilized using a synthetic oligomer (FAM-labelled) deposited on the working electrode of a streptavidin-modified, screen-printed carbon electrode (SPCE). The zot gene was used as an internal control with biotin and FAM labelled as forward and reverse primers, respectively. The blaOXA-51-like gene was amplified using asymmetric PCR (aPCR) to generate single-stranded amplicons that were detected using the designed SPCE. The amperometric current response was detected with a peroxidase-conjugated, anti-fluorescein antibody. The assay was tested using reference and clinical A. baumannii strains and other nosocomial bacteria. The analytical sensitivity of the assay at the genomic level and bacterial cell level was 0.5 pg/mL (1.443 µA) and 103 CFU/mL, respectively. The assay was 100% specific and sensitive for A. baumannii. Based on accelerated stability performance, the developed genosensor was stable for 1.6 years when stored at 4 °C and up to 28 days at >25 °C. The developed electrochemical genosensor is specific and sensitive and could be useful for rapid, accurate diagnosis of A. baumannii infections even in temperate regions.

Submicron aerosols share potential pathogens and antibiotic resistomes with wastewater or sludge

Generation of size-segregated aerosols is an important eco-environmental problem in wastewater treatment plants (WWTPs), but the characteristics of potential pathogens and antibiotic resistomes in submicron aerosols (PM_1.0) were almost unknown. Here, 16S rRNA gene amplification and shotgun metagenome sequencing were respectively used to study the profiles of potential pathogens and antibiotic resistance genes (ARGs) in PM_1.0 from a full-scale WWTP. Acinetobacter and sul1 were respectively the predominant potential pathogens and ARG subtypes in PM_1.0 from aeration process. A total of 9 potential pathogens and 147 ARG subtypes, were shared among WWTP-PM_1.0, wastewater/sludge, and ambient air. Significant differences of potential pathogens or ARGs were found between WWTP-PM_1.0 and wastewater/sludge, however, wastewater/sludge had more crucial source contribution than the ambient air. Moreover, 13 potential pathogens and 40 ARG subtypes were easily aerosolized in PM_1.0 from at least one of the treatment units. ARGs were mainly harbored by Proteobacteria, and multidrug resistance genes were the most ARG type carried by potential pathogens. Taken together, this study indicates the prevalence of potential pathogens, ARGs, and ARG-carrying potential pathogens in WWTP-PM_1.0, which highlights the potential risk of PM_1.0 in spreading potential pathogens and antibiotic resistomes into the air environments.

Inhibition of the Quorum Sensing System, Elastase Production and Biofilm Formation in Pseudomonas aeruginosa by Psammaplin A and Bisaprasin

Natural products derived from marine sponges have exhibited bioactivity and, in some cases, serve as potent quorum sensing inhibitory agents that prevent biofilm formation and attenuate virulence factor expression by pathogenic microorganisms. In this study, the inhibitory activity of the psammaplin-type compounds, psammaplin A (1) and bisaprasin (2), isolated from the marine sponge, Aplysinellarhax, are evaluated in quorum sensing inhibitory assays based on the Pseudomonas aeruginosa PAO1 lasB-gfp(ASV) and rhlA-gfp(ASV) biosensor strains. The results indicate that psammaplin A (1) showed moderate inhibition on lasB-gfp expression, but significantly inhibited the QS-gene promoter, rhlA-gfp, with IC50 values at 14.02 μM and 4.99 μM, respectively. In contrast, bisaprasin (2) displayed significant florescence inhibition in both biosensors, PAO1 lasB-gfp and rhlA-gfp, with IC50 values at 3.53 μM and 2.41 μM, respectively. Preliminary analysis suggested the importance of the bromotyrosine and oxime functionalities for QSI activity in these molecules. In addition, psammaplin A and bisaprasin downregulated elastase expression as determined by the standard enzymatic elastase assay, although greater reduction in elastase production was observed with 1 at 50 μM and 100 μM. Furthermore, the study revealed that bisaprasin (2) reduced biofilm formation in P. aeruginosa.

Bacterial distribution on the ocular surface of patients with primary Sjögren's syndrome

Many studies have shown that gut microbial dysbiosis is a major factor in the etiology of autoimmune diseases but none have suggested that the ocular surface (OS) microbiome is associated with Sjögren’s syndrome (SS). In this prospective study, we analyzed bacterial distribution on the OS in patients with primary SS. Among the 120 subjects included in this study, 48 patients (group A) had primary SS, whereas 72 subjects (group B) had dry eye symptoms that were unrelated to SS. We evaluated clinical dry eye parameters such as the OS disease index, ocular staining score (OSS), Schirmer’s I test, and tear break-up time (TBUT). Conjunctival swabs were used to analyze the microbial communities from the two groups. Bacterial 16S rRNA genes were sequenced using the Illumina MiSeq platform, and the data were analyzed using the QIIME 1.9.1 program. The Shannon index was significantly lower in group A than in group B microbiota (p < 0.05). An analysis of similarity using the Bray–Curtis distance method found no difference in beta-diversity between the two groups (p > 0.05). In group A, Actinobacteria at the phylum level and Corynebacteria at the genus level exhibited low abundance than group B, but the differences were not statistically significant (p > 0.05). SS apparently decreases the diversity of the OS microbial community. These observations may be related to the pathophysiology of SS and should be investigated in future studies.

Distribution of antibiotic resistance genes from human and animal origins to their receiving environments: A regional scale survey of urban settings

Antibiotic resistance is a growing problem for ecosystem health and public healthcare. Hence, the transmission of antibiotic resistance from human and animal origins to natural environments requires careful investigation. In this study, nine antibiotic resistance genes (ARGs), three mobile genetic elements (MGEs), and their relations with antibiotics, heavy metals, and microbiota were investigated in 16 sample sites (Xinxiang, China). Fluoroquinolones (0.13-14.22 μg/L) were most abundant in hospital effluent and oxytetracycline (251.86-5817.47 μg/kg) in animal manure. Animal manure showed the highest levels of zinc (80.79-2597.14 mg/kg) and copper (32.47-85.22 mg/kg), possibly affecting the prevalence of intI1 and aac(6')-Ib genes. Aminoglycoside and sulfonamide resistance genes (aac(6')-Ib, aadA, and sul1) were the main ARGs in this area. In addition, the detected ARGs and MGEs were higher in animal manure than in hospital effluent, except for the sul1 gene. On the other hand, the incomplete removal of antibiotics (29.76-100%), heavy metals (31.25-100%), and ARGs (1-3 orders of magnitude) in MWWTPs resulted in the accumulation of these contaminants in the receiving river. Network analysis suggested that the potential hosts (Jeotgalibaca, Atopostipes, Corynebacterium_1, etc.) of ARGs were more predominant in animal manure rather than hospital effluent, indicating a higher ARG transfer potential in animal manure compared with hospital sources. These results provide useful insights into the different migration and dissemination routes of antibiotics, heavy metals, ARGs, and microbiota from anthropogenic and animal origins to their receiving environments via MWWTP discharge and manure fertilization.

Phylogenetic analysis of carbapenem-resistant Acinetobacter baumannii isolated from different sources using Multilocus Sequence Typing Scheme

The emergence and worldwide distribution of carbapenem-resistant Acinetobacter baumannii strains has become a major public health threat. The objective of this study was to investigate the clonal relatedness of A. baumannii isolates collected from clinical and extra-hospital environments in Mthatha, South Africa. Forty carbapenem-resistant isolates comprising of clinical (20) and extra-hospital (20) were identified and tested for antimicrobial susceptibility. Detection of carbapenemase encoding genes was performed by Real-time PCR. The clonal relationship of clinical isolates relative to extra-hospital isolates was determined via multilocus sequence typing (MLST). All isolates (clinical and extra-hospital) were resistant to most common antibiotics including carbapenems (imipenem; MIC ≥32 μg/mL and meropenem; MIC ≥32 μg/mL) with the only exception being amikacin (with 3 isolates susceptible), tigecycline (14 isolates susceptible) and colistin (all isolates susceptible). The bla OXA-23-like and the intrinsic bla OXA-51 -like genes were detected in all the isolates tested. The bla OXA-58-like and bla IMP-type genes were detected in 2 clinical isolates whilst the bla OXA-24-like, bla VIM-type, bla NDM-1, bla SIM, and bla AmpC were not detected. The bla OXA-24-like, bla OXA-58-like, bla IMP-type, bla VIM-type, bla NDM-1, bla SIM, and bla AmpC were negative in the extra-hospital isolates. Co-occurrence of bla OXA-23 -like, bla OXA-58-like and bla IMP-type was observed in 2 clinical isolates. The MLST performed on 33 isolates identified 5 existing sequence types (ST) (ST1, ST2, ST25, ST85 and ST215) in clinical isolates and 2 existing STs (ST1 and ST2) in extra-hospital isolates. The most dominant ST was ST2 accounting for 68.8% of the clinical isolates and 82.4% of the extra-hospital isolates. The study demonstrated high prevalence and potential clonal spread of globally-disseminated clonal complex 2 carrying bla OXA-23-like within our local settings. However, ST25 might be an emerging lineage carrying the bla OXA-23-like . Continuous monitoring is important in limiting the spread of these strains in other healthcare settings and the community.

Lipophilic quinolone derivatives: Synthesis and in vitro antibacterial evaluation

This paper reports on the design of a series of 10 novel lipophilic piperazinyl derivatives of the 1-cyclopropyl-6-fluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid, their synthesis, their characterisation by ¹H, ¹³C and ¹⁹F NMR, IR spectroscopy and HRMS, as well as their biological activity against bacteria of medical interest. Among these derivatives, 2 were as potent as the parent quinolone against Neisseriagonorrhoeae whereas all the compounds displayed lower activity than the parent quinolone against other bacteria of medical interest. Our results showing that the increased lipophilicity was deleterious for antibacterial activity may help to design new quinolone derivatives in the future, especially lipophilic quinolones which have been poorly investigated previously.

Burns and biofilms: priority pathogens and in vivo models

Burn wounds can create significant damage to human skin, compromising one of the key barriers to infection. The leading cause of death among burn wound patients is infection. Even in the patients that survive, infections can be notoriously difficult to treat and can cause lasting damage, with delayed healing and prolonged hospital stays. Biofilm formation in the burn wound site is a major contributing factor to the failure of burn treatment regimens and mortality as a result of burn wound infection. Bacteria forming a biofilm or a bacterial community encased in a polysaccharide matrix are more resistant to disinfection, the rigors of the host immune system, and critically, more tolerant to antibiotics. Burn wound-associated biofilms are also thought to act as a launchpad for bacteria to establish deeper, systemic infection and ultimately bacteremia and sepsis. In this review, we discuss some of the leading burn wound pathogens and outline how they regulate biofilm formation in the burn wound microenvironment. We also discuss the new and emerging models that are available to study burn wound biofilm formation in vivo.

Taxonomic and Functional Distribution of Bacterial Communities in Domestic and Hospital Wastewater System: Implications for Public and Environmental Health

The discharge of untreated hospital and domestic wastewater into receiving water bodies is still a prevalent practice in developing countries. Unfortunately, because of an ever-increasing population of people who are perennially under medication, these wastewaters contain residues of antibiotics and other antimicrobials as well as microbial shedding, the direct and indirect effects of which include the dissemination of antibiotic resistance genes and an increase in the evolution of antibiotic-resistant bacteria that pose a threat to public and environmental health. This study assessed the taxonomic and functional profiles of bacterial communities, as well as the antibiotic concentrations in untreated domestic wastewater (DWW) and hospital wastewater (HWW), using high-throughput sequencing analysis and solid-phase extraction coupled to Ultra-high-performance liquid chromatography Mass Spectrometry (UHPLC–MS/MS) analysis, respectively. The physicochemical qualities of both wastewater systems were also determined. The mean concentration of antibiotics and the concentrations of Cl⁻, F⁻ and PO₄³ were higher in HWW samples than in DWW samples. The phylum Firmicutes was dominant in DWW with a sequence coverage of 59.61% while Proteobacteria was dominant in HWW samples with a sequence coverage of 86.32%. At genus level, the genus Exiguobacterium (20.65%) and Roseomonas (67.41%) were predominant in DWW and HWW samples, respectively. Several pathogenic or opportunistic bacterial genera were detected in HWW (Enterococcus, Pseudomonas and Vibrio) and DWW (Clostridium, Klebsiella, Corynebacterium, Bordetella, Staphylocccus and Rhodococcus) samples. Functional prediction analysis indicated the presence of beta-lactam resistance, cationic antimicrobial peptide (CAMP) resistance and vancomycin resistance genes in HWW samples. The presence of these antibiotic resistance genes and cassettes were positively correlated with the presence of pathogens. These findings show the risk posed to public and environmental health by the discharge of untreated domestic and hospital wastewaters into environmental water bodies.

Characteristics of size-segregated aerosols emitted from an aerobic moving bed biofilm reactor at a full-scale wastewater treatment plant

Aerosol emissions from wastewater treatment plants (WWTPs) have been associated with health reverberation but studies about characteristics of size-segregated aerosol particulate matter (PM) are scarce. In this study, the measurement of particulate number size distribution in the range of < 10 µm, and the collection of PM_10-2.5, PM_2.5-1.0 and PM_1.0, were conducted from an aerobic moving bed biofilm reactor (MBBR) at a full-scale WWTP. MBBR aerosols showed a unimodal number size distribution, with the majority of particles (>94%) in the ultrafine size range (<100 nm). For toxic metal(loid)s or potential pathogens, significant differences were found within MBBR aerosols (PM_10-2.5, PM_2.5-1.0, and PM_1.0), and also between MBBR aerosols and wastewater. Both wastewater and ambient air had important source contributions for MBBR aerosols. The compositions of toxic metal(loid)s in PM_1.0, and the populations of potential bacterial or fungal pathogens in PM_10-2.5 and PM_2.5-1.0, were dominated by that from wastewater. Compared to PM_10-2.5 and PM_2.5-1.0, PM_1.0 had the highest aerosolization potential for the toxic metal(loid)s of As, Cd, Co, Cr, Li, Mn, Ni, U, and Zn, and the genera of Acinetobacter, Pseudomonas and Fusarium. Due to the size-segregated specialty, targeted measures should be employed to reduce the health risks. CAPSULE: The compositions of toxic metal(loid)s in PM_1.0, and the populations of potential pathogens in PM_10-2.5 and PM_2.5-1.0, were dominated by that from wastewater.

Prevalence of multidrug-resistant Acinetobacter baumannii in a critical care setting: A tertiary teaching hospital experience

Background:

The management of Acinetobacter baumannii infection is considered a challenge especially in an intensive care setting. The resistance rate makes it difficult to manage and is believed to lead to higher mortality. We aim to investigate the prevalence of Acinetobacter baumannii and explore how different antibiotic regimens could impact patient outcomes as there are no available published data to reflect our population in our region.

Methods:

We conducted a retrospective review of all infected adult patients admitted to the intensive care unit at King Fahad University Hospital with a confirmed laboratory diagnosis of Acinetobacter baumannii from 1 January 2013 until 31 December 2017. Positive cultures were obtained from the microbiology department and those meeting the inclusive criteria were selected. Variables were analyzed using descriptive analysis and cross-tabulation. Results were further reviewed and audited by blinded co-authors.

Results:

A comprehensive review of data identified 198 patients with Acinetobacter baumannii. The prevalence of Acinetobacter baumannii is 3.37%, and the overall mortality rate is 40.81%. Our sample consisted mainly of male patients, that is, 68.7%, with a mean age of 49 years, and the mean age of female patients was 56 years. The mean age of survivors was less than that of non-survivors, that is, 44.95 years of age. We observed that prior antibiotic use was higher in non-survivors compared to survivors. From the review of treatment provided for patients infected with Acinetobacter baumannii, 65 were treated with colistin alone, 18 were treated with carbapenems, and 22 were treated with a combination of both carbapenems and colistin. The mean length of stay of Acinetobacter baumannii–infected patients was 20.25 days. We found that the survival rates among patients who received carbapenems were higher compared to those who received colistin.

Age-associated variation in the gut microbiota of chinstrap penguins (Pygoscelis antarctica) reveals differences in food metabolism

Age is known to affect the gut microbiota in various animals; however, this relationship is poorly understood in seabirds. We investigated the temporal succession of gut microbiota in captive chinstrap penguins of different ages using high-throughput sequencing. The gut microbiota exhibited a significant age succession pattern, reaching maturity in adults and then declining with increasing age. Only 15 amplicon sequence variants were shared among the gut microbiota in chinstrap penguins at all studied ages, and these contributed to most of the age-related variations in total gut microbiota. Co-occurrence networks found that these key bacteria belonged to the genera Acinetobacter, Clostridium sensu stricto, and Fusobacterium, and more species interactions were found within the same taxonomy. Functional prediction indicated that most of the metabolic functions were more abundant in the gut microbiota in adult chinstrap penguins, except for carbohydrate metabolism, which was significantly more abundant in older individuals.

Occurrence of Potentially Pathogenic Bacteria in Epilithic Biofilm Forming Bacteria isolated from Porter Brook River-stones, Sheffield, UK

Biofilms in aquatic ecosystems develop on wet benthic surfaces and are primarily comprised of various allochthonous microorganisms, including bacteria embedded within a self-produced matrix of extracellular polymeric substances (EPS). In such environment, where there is a continuous flow of water, attachment of microbes to surfaces prevents cells being washed out of a suitable habitat with the added benefits of the water flow and the surface itself providing nutrients for growth of attached cells. When watercourses are contaminated with pathogenic bacteria, these can become incorporated into biofilms. This study aimed to isolate and identify the bacterial species within biofilms retrieved from river-stones found in the Porter Brook, Sheffield based on morphological, biochemical characteristics and molecular characteristics, such as 16S rDNA sequence phylogeny analysis. Twenty-two bacterial species were identified. Among these were 10 gram-negative pathogenic bacteria, establishing that potential human pathogens were present within the biofilms. Klebsiella pneumoniae MBB9 isolate showed the greatest ability to form a biofilm using a microtiter plate-based crystal violet assay. Biofilm by K. pneumoniae MBB9 formed rapidly (within 6 h) under static conditions at 37 °C and then increased up to 24 h of incubation before decreasing with further incubation (48 h), whereas the applied shear forces (horizontal orbital shaker; diameter of 25 mm at 150 rpm) had no effect on K. pneumoniae MBB9 biofilm formation.

Metallo-Beta-Lactamase-Producing Acinetobacter spp. from Clinical Isolates at a Tertiary Care Hospital in Ghana

Metallo-beta-lactamase-producing Acinetobacter spp. is a major challenge for therapeutic treatment of nosocomial infections. This study is aimed at determining the prevalence of MBL-producing Acinetobacter spp. among 87 clinical isolates of Acinetobacter spp. from the Korle-Bu Teaching Hospital, Accra, between August 2014 and July 2015. Acinetobacter spp. was identified by standard bacteriological method, and resistance to different antibiotics was assessed with the Kirby–Bauer disc diffusion method. Meropenem-resistant Acinetobacter isolates were screened for enzyme activity using the modified Hodge test (MHT) and combined disc test (CDT). Additionally, multiplex PCR was used to determine MBL genes presence (blaVIM_,blaIMP, and blaNDM). All Acinetobacter isolates showed high resistance to cefotaxime (90.8%), ceftazidime (75.9%), cotrimoxazole (70.1%), ciprofloxacin (64.4%), gentamicin (72.4%), levofloxacin (67.8%), and meropenem (59.8%). A total of 54 (62.1%) of Acinetobacter isolates were multidrug-resistant. Out of 52 (59.8%) meropenem-resistant Acinetobacter, 3 (5.8%) were carbapenemase producers by MHT, whilst, 23 (44.2%) were CDT positive. There was no significant difference between the resistance pattern of amikacin, ceftazidime, cotrimoxazole, ciprofloxacin, and meropenem amongst CDT-positive and CDT-negative isolates (p > 0.05). A total of 7/87 (8.1%) CDT-positive Acinetobacter isolates harboured blaNDM; of these, 4 (57.1%) were from wound swabs, urine (n = 2) (28.6%), and ear swab (n = 1) (14.3%). The study revealed that less than 9% of Acinetobacter spp. contained blaNDM encoding genes. Strict antibiotics usage plan and infection control measures are required to prevent the spread of these resistance genes.

Multidrug-Resistant Acinetobacter baumannii - The Modern Menace: A Retrospective Study in a Tertiary Hospital in Mangalore

Background

Multidrug resistance in Acinetobacter baumannii is constantly on the rise. There has also been an increase in the morbidity and mortality of patients with infection by the same pathogen.

Aim

This study aimed to assess the patterns of antibiotic resistance exhibited by various clinical isolates of Acinetobacter baumannii, examine the risk factors associated, and investigate the prevalence of co-infecting pathogens and the clinical outcomes of the patients.

Study Design

Retrospective cross-sectional study.

Patients and Methods

Reports of 100 isolates of Acinetobacter baumannii obtained from patients admitted in two tertiary hospitals were used for the study. Identification and determination of antibiotic resistance patterns were done using Vitek2. The presence of probable risk factors was noted. The pattern of clinical outcomes of the patients and the prevalence of co-infecting pathogens were analyzed. Data analysis was done using descriptive statistics.

Results

More than 50% of isolates showed resistance independently to imipenem and meropenem. Higher rates of susceptibility were observed with tigecycline (55%). Isolates obtained from patients in the intensive care unit (ICU) showed resistance to a more number of antibiotics than those in the wards and operation theatre. Seventeen percent of the isolates were associated with a co-infecting pathogen such as Pseudomonas, Enterococcus, Klebsiella, 87% of the patients were discharged, 12% expired, and 1% were shifted. A positive correlation was found between the duration of hospital stay and number of antibiotics to which the isolate was resistant.

Conclusion

Multidrug resistance in Acinetobacter baumannii continues to be a menace. In this study, a large number of isolates exhibited resistance to carbapenems such as imipenem, meropenem, and ertapenem, thereby signifying the need for further research and the use of other antibiotics such as tigecycline, to which higher susceptibility was observed.

Identification of enterobacteria in viscera of pigs afflicted with porcine reproductive and respiratory syndrome and other viral co-infections

In order to investigate enterobacteria presence involved in the secondary infections in Porcine Reproductive and Respiratory Syndrome (PRRS) pigs with different viral co-infections, we identified enterobacteria for guiding clinical treatment. Twenty-one diseased pigs were diagnosed with the PRRS virus (PRRSV) and other 7 virus primers by PCR/RT-PCR in the lung and spleen samples. Enterobacteria were isolated using MacConkey agar from 5 visceral samples of PRRS pigs, and identified by 16S rDNA sequencing. PRRSV was positive in 100% of the lung samples and 81.0% of the spleen samples. Seven diseased pigs were diagnosed with only PRRSV infection (33.3%), 7 pigs with PRRSV and 1 or 2 other viruses (33.3%) and 7 pigs with PRRSV and more than 2 types of other viruses (33.3%). PRRSV was more inclined to co-infect pigs with porcine group A rotavirus (PARV) with the co-infection rate of 52.4% (11/21). Approximately 13 types of bacteria were successfully isolated from lung, spleen, liver, kidney and lymph node samples of different PRRS pigs. Enterobacteria were isolated in 100% of lung, liver and lymph samples from pigs infected with PRRSV alone. However, the isolation rates were significantly decreased in the more than 3 viruses co-infection group. Escherichia coli was the most prevalent bacterium, followed by Morganella, Proteus, Shigella, Salmonella, Klebsiella and Aeromonas. Most of the isolated enterobacteria were opportunistic pathogens. Therefore, timely combination with antimicrobial agents is necessary for effective treatment of PRRS-infected pigs.

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PRRSV was more inclined to co-infect with PARV.

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Pigs co-infected with more virus, less enterobacteria were isolated from their viscera.

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Enterobacteria isolated from viscera of PRRS pigs were opportunistic pathogens.

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coli, Morganella and Proteus were the most prevalent enterobacteria.

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Secondary infection of enterobacteria should be considered in PRRS treatment.

Transcriptional Regulation of the Outer Membrane Protein A in Acinetobacter baumannii

Acinetobacter baumannii is known for its virulence in severely ill, hospitalized patients and for exhibiting multidrug resistance. A. baumannii infection treatment poses a serious problem in clinical environments. The outer membrane protein A (OmpA) of the Acinetobacter genus is involved in bacterial virulence. Regulatory factors of OmpA in the post-transcriptional stage have been previously identified. However, the regulatory factors that act before the transcriptional stage remain unclear. We investigated the A1S_0316 gene that encodes a putative transcription factor for OmpA expression in A. baumannii. A1S_0316 was purified and examined using size-exclusion chromatography, which revealed that it forms an oligomer. The binding affinity of A1S_0316 to the OmpA promoter region was also examined. We compared the binding affinity to the OmpA promotor region between A1S_0316 and the AbH-NS protein. A1S_0316 showed higher binding affinity to the OmpA promotor region than did H-NS. We examined the regulatory effect of these proteins on OmpA expression in A. baumannii using real-time qPCR and various in vitro tools. Our results indicated that A1S_0316 acts as an anti-repressor on the promotor region of the OmpA gene by inhibiting the binding of the AbH-NS protein. This study was the first demonstration of the transcriptional regulation of OmpA expression.

Multi-drug resistance of blood stream, urinary tract and surgical site nosocomial infections of Acinetobacter baumannii and Pseudomonas aeruginosa among patients hospitalized at Felegehiwot referral hospital, Northwest Ethiopia: a cross-sectional study

BACKGROUND

Multi-drug resistant (MDR) Acinetobacter baumannii and Pseudomonas aeruginosa are major causes of nosocomial infections globally. They are the current World Health Organization critical priority pathogens for resistance, Antimicrobial resistance (AMR) surveillance and discovery of new antibiotics. However, there is paucity of data on nosocomial infections (NIs) caused by such superbugs in Ethiopia. Therefore, this study determined the magnitude and profile of nosocomial MDR A. baumannii and P. aeruginosa infections among patients hospitalized at Felegehiwot referral hospital, Northwest Ethiopia.

METHODS

A cross-sectional study was conducted at Felegehiwot referral hospital from April 1 to July 31, 2018. A total of 238 patients with blood stream, urinary tract and surgical site NIs were enrolled conveniently. Either blood, urine and wound swab specimens were collected and processed using standard bacteriological procedures. A. baumannii and P. aeruginosa isolates were identified using standard bacteriological techniques and confirmed by automated Vitek2 Compact. Antimicrobial susceptibility testing on isolates was performed using the disk diffusion technique. The results were interpreted as per the standard zone sizes of Clinical and Laboratory Standards Institute.Chi-square test was done to determine associations among variables. P value < 0.05 was considered statistical significant.

RESULTS

The median age of participants was 29 years. Overall,20(8.4%) of patients had nosocomial MDR A. baumannii and P. aeruginosa infections. The proportion of nosocomial MDR blood stream, urinary tract and surgical site infections were 13(8.9%), 5(8.3%) and 2 (6.3%), respectively. Patients with NI had lower mean age (24.9 years) (P = 0.035). All isolates of NIs were from patients with intravenous catheterization. The frequency of NI was 9(3.8%) for MDR A. baumannii and 11(4.6%) for MDR P.aeruginosa. A. baumannii and P. aeruginosa isolates were 100% MDR. All isolates of A. baumannii and P. aeruginosa were 100% resistant to ampicillin and piperacillin.A. baumannii isolates were 33.3 and 44.5% resistance against meropenem and ciprofloxacin, respectively while P.aeruginosa isolates revealed 36.4 and 45.5% resistance against ciprofloxacin and meropenem, respectively.

CONCLUSIONS

Health care associated infections of MDR A.baumannii and P. aeruginosa are critical problems in the study area. Therefore, urgent focused interventions required to contain the spreading of MDR NIs. Treatment of NIs for patients on health care should be guided by antimicrobial susceptibility testing.

A robust method for nucleic acid extraction from fabrics to study bacterial diversity

The importance of studying microbial load on fabrics has been recently realized with reports on fabrics being a source of spread of infection in medical and hospitality sectors. However, methodological limitations have restricted the analysis of microbial diversity on fabrics. Hence, the study aimed to develop a robust method for extraction of DNA from different types of fabrics. Bacterial community profiles could be successfully generated with DNA extracted from real life samples, together with identification of different bacterial genera on fabrics. The study opens up venues to study effect of environmental factors on microbial load on fabrics. Also, such a technique will aid correlation between microbial load and types of fabric so as to come up with recommendation for fabrics bearing minimal microbial load for medical and hospitality sectors.

Thioredoxin-A is a virulence factor and mediator of the type IV pilus system in Acinetobacter baumannii

The Gram-negative pathogen, Acinetobacter baumannii has emerged as a global nosocomial health threat affecting the majority of hospitals in the U.S. and abroad. The redox protein thioredoxin has been shown to play several roles in modulation of cellular functions affecting various virulence factors in Gram-negative pathogens. This study aims to explore the role of thioredoxin-A protein (TrxA) in A. baumannii virulence. We determined that deletion of the TrxA gene did not significantly affect resistance to environmental stressors such as temperature, salt, and pH. However, TrxA was critical for survival in the presence of elevated levels of hydrogen peroxide. Lack of TrxA was associated with decreased expression of type IV pili related genes and an inability to undergo normal twitching motility. Interestingly, the TrxA-null mutant was able to form biofilms better than the wildtype (WT) and was observed to be significantly less virulent than the WT in a pulmonary infection model. These results are supportive of thioredoxin playing a key role in A. baumannii virulence.

Laboratory contamination over time during low-biomass sample analysis

Bacteria are not only ubiquitous on earth but can also be incredibly diverse within clean laboratories and reagents. The presence of both living and dead bacteria in laboratory environments and reagents is especially problematic when examining samples with low endogenous content (e.g., skin swabs, tissue biopsies, ice, water, degraded forensic samples or ancient material), where contaminants can outnumber endogenous microorganisms within samples. The contribution of contaminants within high‐throughput studies remains poorly understood because of the relatively low number of contaminant surveys. Here, we examined 144 negative control samples (extraction blank and no‐template amplification controls) collected in both typical molecular laboratories and an ultraclean ancient DNA laboratory over 5 years to characterize long‐term contaminant diversity. We additionally compared the contaminant content within a home‐made silica‐based extraction method, commonly used to analyse low endogenous content samples, with a widely used commercial DNA extraction kit. The contaminant taxonomic profile of the ultraclean ancient DNA laboratory was unique compared to modern molecular biology laboratories, and changed over time according to researcher, month and season. The commercial kit also contained higher microbial diversity and several human‐associated taxa in comparison to the home‐made silica extraction protocol. We recommend a minimum of two strategies to reduce the impacts of laboratory contaminants within low‐biomass metagenomic studies: (a) extraction blank controls should be included and sequenced with every batch of extractions and (b) the contributions of laboratory contamination should be assessed and reported in each high‐throughput metagenomic study.

Procalcitonin-guided antibiotic discontinuation in ventilator-associated pneumonia: a prospective observational study

Background: Procalcitonin (PCT), an important biomarker, can be used for the guidance of antibiotic therapy in respiratory infection. However, it has been a problem that some patients might need antibiotic therapy restart because of infection recurrence after antibiotic discontinuation. To date, there are very few literature on the study of risk factors accounting for infection recurrence. Purpose of this clinical study: 1) To study on antibiotic discontinuation in ventilator-associated pneumonia (VAP) under the guidance of PCT; 2) To evaluate the possible risk factors leading to infection recurrence and antibiotic reuse.

Methods: Antibiotic discontinuation was performed when patients met the following criteria: (i) serum PCT<0.5 μg/L, (ii) temperature<38.5℃ and (iii) leukocyte count<15×10⁹/L. Next, the patients were divided into infection recurrence group (infection recurring within 7 days after antibiotic discontinuation) or infection controlled group (no infection recurring after antibiotic discontinuation). Possible risk factors accounting for infection recurrence were evaluated using logistic regression analysis.

Results: Of the eligible 51 patients with VAP, 20 patients suffered infection recurrence. Clinical pulmonary infection score (CPIS) and characteristics of tracheal secretions were the independent risk factors (P=0.045 and P=0.041, respectively), accounting for infection recurrence. Simplified CPIS≥5 served a certain predictive value for infection recurrence in VAP when physicians considered antibiotic discontinuation (The area under the receiver operating characteristic curve 0.781, specificity 90.3%, sensitivity 55.0%, positive predictive value 78.6% and negative predictive value 75.7%). At the time of antibiotic discontinuation, differences between the two groups were not statistically significant in the proportion of patients with a tracheotomy and in the culture results of endotracheal aspirates (including semi-quantitative results and whether pathogens were multidrug-resistant [MDR] strains).

Conclusion: Simplified CPIS and characteristics of tracheal secretions can be used to predict infection recurrence following PCT-guided antibiotic discontinuation in VAP. These findings are important because physicians may not need to put too much care on semi-quantitative culture results of endotracheal aspirates and whether pathogens are MDRstrains.

Trial registration: The registration number of this clinical trial is: ChiCTR-OPC-17011228 (Trial registry name: Chinese Clinical Trial Registry; URL: http://www.chictr.org.cn).

Meropenem and Amikacin for Management of Post-Neurosurgical Infections from Acinetobacter baumannii

Background: Intra-cranial infection with Acinetobacter baumannii is a tough problem because of the presence of multi-resistance and poor drug penetration through the blood-brain barrier. Such intra-cranial infections can lead to serious complications and death. We retrospectively analyzed the culture results and clinical characteristics of patients with intra-cranial infections in our hospital and suggested intravenous (IV) meropenem and intra-thecal (IT) amikacin therapy may be effective in the management of A. baumannii infection. Case presentation: We reported four cases of post-neuro-surgical A. baumannii intra-cranial infection whose clinical futures were high fever and consciousness disturbance. Our patients were treated successfully with IV meropenem and IT amikacin. Conclusion: We presented our cases of pandrug-resistant A. baumannii intra-cranial infection that was managed successfully with a systemic provision of IV meropenem and IT amikacin. Therefore, these cases exemplify that systemic administration of IV meropenem and IT amikacin can be a good therapeutic option against A. baumannii intra-cranial infection when colistin is not available.

Cobalamin (Vitamin B12) Induced a Shift in Microbial Composition and Metabolic Activity in an in vitro Colon Simulation

Cobalamin deficiency is believed to be related to disturbances in cell division, neuropathy, nervous system disease and pernicious anemia. Elderly people are usually advised to supplement their diets with cobalamin. As cobalamin has several forms, the effects of different forms of cobalamin on gut microbiota were investigated in this study. After 7 days of supplementation, methylcobalamin had reduced the diversity of gut microbiota compared to that in the control and cyanocobalamin groups. After supplementation with methylcobalamin, the percentage of Acinetobacter spp. had increased to 45.54%, while the percentages of Bacteroides spp., Enterobacteriaceae spp. and Ruminococcaceae spp. had declined to 11.15, 9.34, and 2.69%, respectively. However, cyanocobalamin had different influences on these bacteria. Both cobalamins increased the amount of short-chain fatty acids, particularly butyrate and propionic acid. The cyanocobalamin group showed increased activity of cellulase compared with that in the other two groups. According to CCA and PICRUSt analysis, methylcobalamin had a positive correlation with Pseudomonas bacteria, propionic acid, and butyrate. Methylcobalamin promoted lipid, terpenoid, and polyketide metabolism by gut bacteria, promoted the degradation of exogenous substances, and inhibited the synthesis of transcription factors and secondary metabolites. Our results indicate that the various forms of cobalamin in the food industry should be monitored and regulated, because the two types of cobalamin had different effects on the gut microbiome and on microbial metabolism, although they have equal bio-activity in humans. Given the effects of methylcobalamin on gut microbiota and microbial metabolism, methylcobalamin supplementation should be suggested as the first option.

Acinetobacter baumannii Gastrointestinal Colonization Is Facilitated by Secretory IgA Which Is Reductively Dissociated by Bacterial Thioredoxin A

Multidrug-resistant Acinetobacter baumannii is among the most common causes of infectious complications associated with combat-related trauma in military personnel serving overseas. However, little is currently known about its pathogenesis. While the gastrointestinal (GI) tract has been found to be a major reservoir for A. baumannii, as well as to potentially contribute to development of multidrug resistance, no studies have addressed the mechanisms involved in gut colonization. In this study, we address this critical gap in knowledge by first assessing the interaction between secretory IgA (SIgA), the principal humoral immune defense on mucosal surfaces, and the A. baumannii clinical isolate Ci79. Surprisingly, SIgA appeared to enhance A. baumannii GI tract colonization, in a process mediated by bacterial thioredoxin A (TrxA), as evidenced by reduction of bacterial attachment in the presence of TrxA inhibitors. Additionally, a trxA targeted deletion mutant (ΔtrxA) showed reduced bacterial burdens within the GI tract 24 h after oral challenge by in vivo live imaging, along with loss of thiol-reductase activity. Surprisingly, not only was GI tract colonization greatly reduced but the associated 50% lethal dose (LD₅₀) of the ΔtrxA mutant was increased nearly 100-fold in an intraperitoneal sepsis model. These data suggest that TrxA not only mediates A. baumannii GI tract colonization but also may contribute to pathogenesis in A. baumannii sepsis following escape from the GI tract under conditions when the intestinal barrier is compromised, as occurs with cases of severe shock and trauma.

Acinetobacter baumannii is an emerging bacterial pathogen recently classified as a serious threat to U.S. and global health by both the Centers for Disease Control and Prevention and the World Health Organization. It also is one of the leading causes of combat-related infections associated with injured military personnel serving overseas. Little is known regarding mechanisms of gastrointestinal tract colonization despite this site being shown to serve as a reservoir for multidrug-resistant (MDR) A. baumannii isolates. Here, we establish that secretory IgA, the major immunoglobulin of mucosal surfaces, promotes A. baumannii GI tract colonization via bacterial thioredoxin A as evidenced through significant reduction in colonization in IgA-deficient animals. Additionally, bacterial colonization and mortality were significantly reduced in animals challenged with a thioredoxin A-deficient A. baumannii mutant. Combined, these data suggest that thioredoxin A is a novel virulence factor, for which antithioredoxin therapies could be developed, for this important multidrug-resistant pathogen.

Occurrence and diversity of antibiotic resistance in untreated hospital wastewater

Antibiotics, antibiotic-resistant bacteria (ARB), antibiotic-resistance genes (ARGs), and mobile genetic elements (MGEs) have been reported in many environments. However, the investigation of their occurrence and diversity in untreated hospital wastewater is still insufficient. High concentrations of antibiotic residues were found in hospital wastewater using solid-phase extraction and UPLC-MS/MS analysis. The concentrations of six of 14 antibiotics reached μg/L levels in the hospital wastewater, which is higher than reported in other aquatic environments. Results of high-throughput sequencing analysis indicated that sequences affiliated to genera Escherichia and Acinetobacter were the predominant in the cultivable multiple-antibiotic-resistant bacteria (CMARB) recovered from the wastewater of three hospitals in China, with compositions of 34%-74%. Notably, several genera containing clinically pathogenic or opportunistic CMARB (e.g., Escherichia, Acinetobacter, Aeromonas, Myroides, Enterococcus, Proteus, Pseudomonas, and Streptococcus) were detected at high relative abundances in the wastewaters of the three hospitals. High-capacity quantitative PCR showed that 131-139 unique ARGs of the 178 targeted genes were detected in the hospital wastewaters. The high prevalence of five MGEs and 12 ARGs was confirmed with qPCR, and some positive correlations between ARGs and MGEs were identified, such as between intI1 and qnrD, intI2 and sul3, intI3 and tetX, Tn916/Tn1545 and sul2, and ISCR1 and sul3. These results suggest that highly abundant antibiotic-resistant pathogens and highly mobile ARGs already exist in the human body, and that their release from hospitals without effective treatment poses high risks to environments and human health.

Molecular Characterization and Antibiotic Susceptibility Pattern of Acinetobacter Baumannii Isolated in Intensive Care Unit Patients in Al-Hassa, Kingdom of Saudi Arabia

Background:

Acinetobacter baumannii, is an emerging nosocomial multidrug resistance pathogen with the rapid spread of clones being reported in health-care settings and hospitals worldwide. Carbapenem resistance in this bacterium has been attributed to D OXA β-lactamases with OXA-51-like β-lactamase, being present in all A. baumannii isolate. The present study looks into the antibiotics susceptibility and molecular characterization of clinical A. baumannii isolates from Intensive Care Unit (ICU) samples in Al-Hofuf, South-eastern region of Saudi Arabia.

Materials and Methods:

Eleven strains of ICU A. baumanni i isolates were used for the investigation. Bacteria isolation was by basic microbiological techniques. Organisms identification and antibiogram susceptibility testing was by the BioMerieux VITEK 2 compact automated system (BioMerieux, Marcy I'Etoile France), according to the manufacturers guidelines. Confirmation of A. baumannii was by the presence of the OX-51 gene, also, carbapenemase encoding resistant genesbla_OXA-23, bla_OXA-40, and bla_OXA-51, were analyzed using multiplex PCR. The Student's t test was used to analyze the obtained data for between group comparisons with statistically significance level set at P < 0.05.

Results:

Eight of the isolates were confirmed to be A. baumannii. Five of which were resistant to the carbapenems against which they had been tested. One isolate was resistant to tigecycline, whereas three tested intermediate to the drug. OXA-23 was detected in isolates 1, 4, 5, 6, and 7.

Conclusion:

It can, therefore, be concluded that the probable predominate carbapenems resistant genes in ICU isolates from the present investigation, are those associated with OXA-23.

Genetic characterization and in vitro activity of antimicrobial combinations of multidrug-resistant Acinetobacter baumannii from a general hospital in China

The present study aimed to develop a rational therapy based on the genetic epidemiology, molecular mechanism evaluation and in vitro antibiotic combinations activity in multidrug-resistant Acinetobacter baumannii (MDRAB). MDRAB was screened by the Kirby-Bauer method. The random amplified polymorphic DNA technique was used to establish genetic fingerprinting, and a series of resistance genes were detected by polymerase chain reaction. Antimicrobial agents including amikacin (AK), cefoperazone/sulbactam (SCF I/II), meropenem (MEM), minocycline (MINO) and ciprofloxacin (CIP) were used to determine the minimum inhibitory concentrations (MICs) and interactions between antibiotics by the broth microdilution method and chequerboard assays. In total, 34 MDRAB strains were isolated and classified into 8 phenotypes A-H, according to their general drug susceptibilities. A total of 4 major genotypes (I–IV) were clustered at 60% a genotypic similarity threshold. High positive rates of β-lactamase TEM-1, topoisomerase IV, oxacillinase (OXA)-23, AdeB family multidrug efflux RND transporter adeB, β-lactamase AmpC, class 1 integrons (Int-1), 16S rRNA methylase rmtA, phosphotransferase aph(3), 16S rRNA methyltransferase armA were presented to exceed 90%, acetylyltransferase aac(3)-I, aac(6′-I, ant(3″)-I, 16S rRNA methylase rmtB, oxacillinase OXA-24 and metallo-β-lactamase IMP-5 genes demonstrated positive rates of 29.4–85.29%, while adeRS two-component system was not observed in any strain. MEM+SCF I or SCF II primarily exhibited synergistic effects. AK+SCF I, AK+SCF II, MINO+SCF I, MINO+SCF II, MINO+CIP and MINO+MEM primarily presented additive effects. AK+CIP demonstrated 70.59% antagonism. The antibacterial activity of SCF I was superior compared with that of SCF II. The results indicated the polyclonal genetic epidemiological trend of MDRAB in the Second Xiangya Hospital, and verified the complexity of genetic resistance. In addition, combinations suggested to be efficacious were MEM+SCF I and MEM+SCF II, which were more effective compared with other combinations for the management of MDRAB infection.

Molecular characterization of Acinetobacter baumannii isolated from Iraqi hospital environment

Healthcare-associated items are a common source of acquired infections, and hospital-acquired infections cause significant mortality and morbidity worldwide. Acinetobacter baumannii is the most prevalent infection-causing organism in the hospital environment. Hospital articles and objects are the main sources of infection with the ability to transmit some of the pathogenic microorganisms such as A. baumannii, which is considered a serious problem in therapeutic treatments. In the current study, we isolated A. baumannii from hospital sources and evaluated its antibiotic resistance, virulence factors and resistance gene determinants. The isolates were identified phenotypically as well as genotypically using PCR. In addition, their capability for biofilm formation and ten other virulence factors were measured. Of 112 samples, 21 showed growth of the target organism. Apart from A. baumannii, isolates of Candida albicans, Staphylococcus sp., Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae were also grown. Antibiotic susceptibility test results considered all the A. baumannii to be multidrug-resistant isolates with the highest resistance being 100% to gentamycin, ciprofloxacin; the most effective antibiotics with 100% susceptibility was colistin and tigecycline. All A. baumannii isolates had MIC for ceftriaxone >32 mg/L. All A. baumannii isolates from the hospital environment showed multidrug resistance and had many virulence factors. They have long-term resistance to dry conditions and cause a serious public health issue.

Chemical Interrogation of LuxR-type Quorum Sensing Receptors Reveals New Insights into Receptor Selectivity and the Potential for Interspecies Bacterial Signaling

Cell-cell signaling between bacteria, including quorum-sensing (QS) communication systems, may play a role in the establishment and maintenance of polymicrobial communities. To better understand and model these interactions, we must uncover the degree to which neighboring species recognize each another's signals. In the current study, we tested the likelihood of whether the QS systems of two opportunistic pathogens (Acinetobacter baumannii and Pseudomonas aeruginosa) that frequently arise in polymicrobial infections would be affected by the QS signals of neighboring species. Through the synthesis and screening of a library of native and non-native N-acyl l-homoserine lactones (AHLs), we found that the AbaR LuxR-type receptor protein of A. baumannii is highly selective for its native AHL signal. However, a homologous LuxR-type receptor in P. aeruginosa, LasR, is far more promiscuously activated by AHLs relative to AbaR, suggesting that LasR-regulated QS could be more susceptible to activation by neighboring species. To explain the observed difference in signal selectivity between AbaR and LasR, we developed a model based on (i) the activity profiles of these proteins and (ii) previously reported structural data and activity profiles for related LuxR-type receptors. This model may facilitate the study of signal selectivities for hundreds of LuxR-type QS receptors from bacteria, many of which grow in polymicrobial communities and may sense each other's signals. In addition, we discovered a set of AHLs that could be used to selectively activate LasR and selectively inhibit AbaR in polymicrobial experiments.

Pneumonia caused by extensive drug-resistant Acinetobacter baumannii among hospitalized patients: genetic relationships, risk factors and mortality

BACKGROUND

The clonal spread of multiple drug-resistant Acinetobacter baumannii is an emerging problem in China. We analysed the molecular epidemiology of Acinetobacter baumanni isolates at three teaching hospitals and investigated the risk factors, clinical features, and outcomes of hospital-acquired pneumonia caused by extensive drug-resistant Acinetobacter baumannii (XDRAB) infection in Guangzhou, China.

METHODS

Fifty-two A. baumannii isolates were collected. Multilocus sequence typing (MLST) was used to assess the genetic relationships among the isolates. The bla _OXA-51-like gene was amplified using polymerase chain reaction (PCR) and sequencing. The resistance phenotypes were determined using the disc diffusion method. A retrospective case-control study was performed to determine factors associated with XDRAB pneumonia.

RESULTS

Most of the 52 A. baumannii isolates (N = 37, 71.2%) were collected from intensive care units (ICUs). The respiratory system was the most common bodily site from which A. baumannii was recovered (N = 45, 86.5%). Disc diffusion classified the isolates into 17 multidrug-resistant (MDR) and 35 extensively drug-resistant (XDR) strains. MLST grouped the A. baumannii isolates into 5 existing sequence types (STs) and 7 new STs. ST195 and ST208 accounted for 69.2% (36/52) of the isolates. The clonal relationship analysis showed that ST195 and ST208 belonged to clonal complex (CC) 92. According to the sequence-based typing (SBT) of the bla _OXA-51-like gene, 51 A. baumannii isolates carried OXA-66 and the rest carried OXA-199. There were no significant differences with respect to the resistance phenotype between the CC92 and non-CC92 strains (P = 0.767). The multivariate analysis showed that the APACHE II score, chronic obstructive pulmonary disease (COPD) and cardiac disease were independent risk factors for XDRAB pneumonia (P < 0.05). The mortality rate of XDRAB pneumonia was high (up to 42.8%), but pneumonia caused by XDRAB was not associated with in-hospital mortality (P = 0.582).

CONCLUSIONS

ST195 may be the most common ST in Guangzhou, China, and may serve as a severe epidemic marker. SBT of bla _OXA-51-like gene variants may not result in sufficient dissimilarities to type isolates in a small-scale, geographically restricted study of a single region. XDRAB pneumonia was strongly related to systemic illnesses and the APACHE II score but was not associated with in-hospital mortality.

Disruption of tetR type regulator adeN by mobile genetic element confers elevated virulence in Acinetobacter baumannii

Acinetobacter baumannii is an important human pathogen and considered as a major threat due to its extreme drug resistance. In this study, the genome of a hyper-virulent MDR strain PKAB07 of A. baumannii isolated from an Indian patient was sequenced and analyzed to understand its mechanisms of virulence, resistance and evolution. Comparative genome analysis of PKAB07 revealed virulence and resistance related genes scattered throughout the genome, instead of being organized as an island, indicating the highly mosaic nature of the genome. Many intermittent horizontal gene transfer events, insertion sequence (IS) element insertions identified were augmenting resistance machinery and elevating the SNP densities in A. baumannii eventually aiding in their swift evolution. ISAba1, the most widely distributed insertion sequence in A. baumannii was found in multiple sites in PKAB07. Out of many ISAba1 insertions, we identified novel insertions in 9 different genes wherein insertional inactivation of adeN (tetR type regulator) was significant. To assess the significance of this disruption in A. baumannii, adeN mutant and complement strains were constructed in A. baumannii ATCC 17978 strain and studied. Biofilm levels were abrogated in the adeN knockout when compared with the wild type and complemented strain of adeN knockout. Virulence of the adeN knockout mutant strain was observed to be high, which was validated by in vitro experiments and Galleria mellonella infection model. The overexpression of adeJ, a major component of AdeIJK efflux pump observed in adeN knockout strain could be the possible reason for the elevated virulence in adeN mutant and PKB07 strain. Knocking out of adeN in ATCC strain led to increased resistance and virulence at par with the PKAB07. Disruption of tetR type regulator adeN by ISAba1 consequently has led to elevated virulence in this pathogen.

Co-Colonization with Neisseria species Is a Risk Factor for Prolonged Colonization with Multidrug-Resistant Acinetobacter baumannii in the Respiratory Tract

Multidrug-resistant Acinetobacter baumannii (MDRAB) colonization increases the risk of bacterial spread in the hospital setting. The impact of clinical factors, including antibiotic use, on prolongation of MDRAB colonization has not been investigated. Patients with respiratory tract MDRAB detected using culture were enrolled in this study. Long-term colonizers and short-term colonizers were defined as patients whose colonization periods were >30 days or ≤30 days, respectively. Clinical data were abstracted from medical records. MDRAB was isolated in 34 patients. There were 13 long-term colonizers and 9 short-term colonizers. Twelve patients were lost to follow-up and excluded from the study. There were no significant differences in average leukocyte counts, numbers of antibiotic classes administered, duration of antibiotic use in the 30 days following colonization, or rates of central catheterization or mechanical ventilation between the 2 groups. Long-term colonizers carried Neisseria species (spp.) more frequently in the 30 days following colonization than short-term colonizers (7/13 vs 1/9, p = 0.01); however, this was not the case prior to colonization with MDRAB (5/13 vs 1/9, p = 0.33). The 90-day MDRAB colonization rates for Neisseria-negative patients and Neisseria-positive patients were 10.0% and 83.3%, respectively (P < 0.01). Prolonged MDRAB colonization in the respiratory tract was associated with Neisseria spp. co-colonization.