Acinetobacter spp. as nosocomial pathogens: Epidemiology and resistance features

Antimicrobial susceptibility pattern of Acinetobacter isolates from patients in Kenyatta National Hospital, Nairobi, Kenya

Introduction

Infection due to multidrug-resistant microorganisms is a growing threat in healthcare settings. Acinetobacter species specifically A. baumannii is increasingly becoming resistant to most antimicrobial agents recommended for treatment. This study aimed to determine the antimicrobial susceptibility pattern of Acinetobacter species isolated from patients in Kenyatta National Hospital.

Methods

We conducted a retrospective study based on VITEK 2 (BioMérieux) electronic records capturing identification and antimicrobial susceptibility of Acinetobacter isolates from patient samples analyzed between 2013 and 2015 at Kenyatta National Hospital microbiology laboratory. Generated data were analyzed using WHONET and SPSS.

Results

A total of 590 Acinetobacter isolates were analyzed. 85% of the isolates tested were multi-drug resistant (MDR). Among the 590 isolates, 273 (46%) were from tracheal aspirates and 285 (48%) from the critical care unit. A. baumannii was the most frequently isolated species with high susceptibility to amikacin (77%) and poor susceptibility to ciprofloxacin (69-76%), tobramycin (37%) and meropenem (27%). Both A. lwoffii and A. haemolyticus had high susceptibility to amikacin (80-100%) and meropenem (75-100%).

Conclusion

A. baumannii is resistant to commonly administered antibiotics. There is need for continuous antimicrobial resistance surveillance especially in health care facilities and strengthening of antibiotic stewardship programmes which will contribute to enhancement of infection control policies.

Whole-genome analysis of New Delhi Metallo-Beta-Lactamase-1-producing Acinetobacter haemolyticus from China

OBJECTIVE

Infections caused by multidrug-resistant Acinetobacter spp. have generated worldwide attention. With the increasing isolation of non-baumannii Acinetobacter, the nature of associated infection and resistance needs to be explored. This study aimed to analyse the characteristics of New Delhi Metallo-Beta-Lactamase-1 (NDM-1)-producing Acinetobacter haemolyticus (named sz1652) isolated from Shenzhen city, China.

METHODS

The antibiotic spectrum was analysed after antimicrobial susceptibility testing. Combined disk test (CDT) was used to detect the metallo-beta-lactamases (MBLs). Transferability of carbapenem resistance was tested by filter mating experiments and plasmid transformation assays. Whole-genome sequencing (WGS) was performed using HiSeq 2000 and PacBio RS system.

RESULTS

The Acinetobacter haemolyticus strain sz1652 was resistant to carbapenems and other tested agents except for amikacin, tigecycline and colistin. Production of MBLs was confirmed by CDT. Transfer of carbapenem resistance was unsuccessful. WGS analysis showed that the genome of sz1652 comprised a chromosome and two plasmids; 16 genomic islands (GIs) were predicted. Genes associated with resistance were found in this strain, including the beta-lactamase genes bla_NDM-1, bla_OXA-214 and bla_LRA-18, the fluoroquinolone resistant-related mutations [GyrA subunits (Ser81Ile) and ParC subunits (Ser84Tyr)], and efflux pump genes related to tetracycline and macrolide resistance. Analysis of the genetic environment showed that bla_NDM-1 was embedded in Tn125 transposon. The Tn125 structure was chromosomally located and shared > 99% sequence identity with the previously reported bla_NDM-1 carrying region.

CONCLUSION

The NDM-1-producing Acinetobacter haemolyticus coexisted with multiple drug-resistant determinants. The acquisition of the bla_NDM-1 gene was probably facilitated by Tn125 in this strain. Non-Acinetobacter baumannii species also contained GIs.

Native soil microorganisms hinder the soil enrichment with antibiotic resistance genes following manure applications

Bacterial genes responsible for resistance to antibiotic agents (ARG) are spread from livestock to soil through application of manure, threatening environmental and human health. We investigated the mechanisms of ARG dissemination and persistence to disentangle i) the influence of nutrients and microorganisms on the soil tetracycline (TET) resistome, and ii) the role of indigenous soil microbiota in preventing ARG spread. We analysed short-term (7 days) and persistent (84 days) effects of manure on the resistome of three antibiotic-free pasture soils. Four microcosm treatments were evaluated: control, mineral nutrient fertilization, and deposition of a layer of fresh manure onto soil or γ-irradiated soil. We quantified five TET-resistance genes, isolated 135 TET-resistant bacteria and sequenced both culturable TET-resistant and whole bacterial communities. Manure amendments, but not nutrient addition, increased the abundance of TET-r genes such as tet(Y). Such changes persisted with time, in contrast with the TET-resistant bacterial composition, which partially recovered after manure amendments. Manured γ-irradiated soils showed significantly lower nutrient content and higher TET-r gene abundance than non-irradiated soils, suggesting that native soil bacteria are essential for the fertilization effect of manure on soil as well as control the dissemination of potentially risky TET-r genes.

Antimicrobial and Antibiofilm Effects of Peptides from Venom of Social Wasp and Scorpion on Multidrug-Resistant Acinetobacter baumannii

Intravascular stent infection is a rare complication with a high morbidity and high mortality; bacteria from the hospital environment form biofilms and are often multidrug-resistant (MDR). Antimicrobial peptides (AMPs) have been considered as alternatives to bacterial infection treatment. We analyzed the formation of the bacterial biofilm on the vascular stents and also tested the inhibition of this biofilm by AMPs to be used as treatment or coating. Antimicrobial activity and antibiofilm were tested with wasp (Agelaia-MPI, Polybia-MPII, Polydim-I) and scorpion (Con10 and NDBP5.8) AMPs against Acinetobacter baumannii clinical strains. A. baumannii formed a biofilm on the vascular stent. Agelaia-MPI and Polybia-MPII inhibited biofilm formation with bacterial cell wall degradation. Coating biofilms with polyethylene glycol (PEG 400) and Agelaia-MPI reduced 90% of A. baumannii adhesion on stents. The wasp AMPs Agelaia-MPI and Polybia-MPII had better action against MDR A. baumannii adherence and biofilm formation on vascular stents, preventing its formation and treating mature biofilm when compared to the other tested peptides.

The Presence of Acinetobacter baumannii DNA on the Skin of Homeless People and Its Relationship With Body Lice Infestation. Preliminary Results

The presence of Acinetobacter baumannii was demonstrated in body lice, however, little is known about the mechanism of natural lice infection. In 2013 and 2014, cross-sectional one-day studies were therefore performed within two Marseille homeless shelters to assess the presence of A. baumannii DNA on human skin, blood and in body lice collected from the same homeless individuals. All 332 participants completed questionnaires, were examined for dermatologic signs, and provided four skin samples (hair, neck, armpits, and pelvic belt), blood samples and body lice (if any). We developed a new real-time PCR tool targeting the ompA/motB gene for the detection of A. baumannii for all collected samples. Blood culture was also performed. Body lice were found in 24/325 (7.4%) of subjects. We showed a prevalence of A. baumannii DNA skin-carriage in 33/305 (10.8%) of subjects. No difference was found in A. baumannii DNA prevalence according to body sites. A strong association between body lice infestation (OR = 3.07, p = 0.029) and A. baumannii DNA skin-carriage was noted. In lice, A. baumannii DNA was detected in 59/219 arthropods (26.9%). All blood cultures and real-time PCR on blood samples were negative for A. baumannii. Lice probably get infected with A. baumannii while biting through the colonized skin and likely transmit the bacteria in their feces. We found no evidence that lice facilitate the invasion of A. baumannii into the blood stream. Further investigations are needed to compare phenotypic and genotypic features of A. baumannii isolates from human skin and lice from the same individuals.

Comparative effects of granulocyte-colony stimulating factor and colistin-alone or in combination on burn wound healing in Acinetobacter baumannii infected mice

BACKGROUND AND OBJECTIVES

Burn wounds are one of the most important health problems all over the world because infection after burn can delay wound healing. Treating burn wounds with granulocyte-colony stimulating factor (G-CSF) is known to improve healing of injured tissue. In addition, colistin is prescribed as an effective treatment. The aim of this study was to evaluate the effect of G-CSF and colistin alone or in combination with G-CSF on wound healing of Acinetobacter baumannii (A. baumannii) infected burns.

MATERIALS AND METHODS

This study was performed between January 2016 and April 2018. Burn wounds were experimentally induced in 36 mice. The wounds were inoculated with A. baumannii. In a 7-day period, burn wounds in each group were daily treated with subcutaneous injections (0.1 ml) of saline, G-CSF, colistin, and G-CSF plus colistin. After killing the animals, the size of the wound, number of leukocytes in the skin and microbial growth were evaluated. A value of p ≤ 0.05 was considered statistically significant.

RESULTS

Wound healing in the G-CSF plus colistin group was significantly higher than the control group and the G-CSF group (P = 0.023 and P = 0.033, respectively). In G-CSF+colistin group, the number of leukocytes was higher than the control group considerably (P = 0.007). On the 7^th day of treatment, number of positive bacterial cultures in the colistin and the G-CSF plus colistin groups was lower than other groups with a significant difference.

CONCLUSION

Concurrent consumption of G-CSF and antibiotics can control burn infection and enhance the immune system towards wound healing.

Molecular mechanisms of antimicrobial resistance in Acinetobacter baumannii, with a special focus on its epidemiology in Lebanon

Acinetobacter baumannii is an opportunistic bacterium involved in several types of infection with high mortality and morbidity, especially in intensive care units. Treatment of these infections remains a challenge due to the worldwide emergence of broad-spectrum resistance to many antibiotics. Following the implementation of molecular techniques to study A. baumannii outbreaks, it has been shown that they are mainly caused by specific clones such as international clones I, II and III. The present work aims to review the available data on the mechanisms underlying antimicrobial resistance in A. baumannii, with a special focus on the molecular epidemiology of this species in Lebanon.

Extended spectrum beta-lactamase mediated resistance in carriage and clinical gram-negative ESKAPE bacteria: a comparative study between a district and tertiary hospital in South Africa

Background

Gram-negative ESKAPE bacteria are increasingly implicated in several difficult-to-treat infections in developed and developing countries. They are listed by the World Health Organization as resistant bacteria of critical priority in research.

Objectives

To determine the risk factors, prevalence, phenotypic profiles, genetic diversity and clonal relatedness of extended-spectrum β-lactamase (ESBL)-producing multi-drug resistant (MDR) Gram-negative ESKAPE bacteria in the faecal carriage and clinical samples from patients in an urban, tertiary and a rural, district hospital in uMgungundlovu District, KwaZulu-Natal, South Africa.

Methods

This study took place in a district and tertiary hospital during a two-months period from May to June 2017 in uMgungundlovu district, South Africa. Rectal swabs collected from hospitalized patients, at admission, after 48 h and at discharge (whenever possible) formed the carriage sample while clinical isolates routinely processed in the microbiological laboratory during the sampling period were also collected and formed the clinical sample. Gram-negative ESKAPE bacteria were screened for ESBL production on selective MacConkey agar and confirmed using ROSCO kits. Minimum inhibitory concentrations were determined, and real-time and multiplex polymerase chain reaction were used to ascertain the presence of bla _CTX-M group-1-2-9, bla _CTX-M group 8/25, bla _SHV, bla _TEM, bla _OXA-1-like, bla _KPC, bla _VIM, bla _IMP, bla _GES and AmpC genes. Genomic fingerprinting was also performed using ERIC-PCR. Risk factors for ESBL-mediating MDR Gram-negative ESKAPE colonization were ascertained by univariate and multivariate logistic regression analyses.

Results

Overall prevalence of carriage of ESBL-mediating MDR Gram-negative ESKAPE was 37.21% (16/43), 42.31% (11/26) and 57.14% (4/7) at admission, after 48 h and at discharge respectively. The prevalence of ESBL-mediating MDR Gram-negative ESKAPE bacteria in faecal carriage (46%) was higher than clinical samples (28%). Colonization was mainly associated with the referral from district to tertiary hospital with high statistical significance (OR: 14.40, 95% CI 0.98-210.84). bla _{CTX-M-group-9}, bla _{CTX-M-group-1} and bla _SHV were the main resistance genes identified. Several patients carried more than two different isolates. A Klebsiella pneumoniae (K1) clone was circulating within wards and between hospitals.

Conclusion

The study highlights the high prevalence of ESBL-mediating MDR Gram-negative ESKAPE bacteria in carriage and clinical samples among hospitalized patients in uMgungundlovu, South Africa. The wide dissemination of these resistant ESKAPE bacteria in hospitals necessitates improvements in routine screening and reinforcement of infection, prevention and control measures.

Insight into Acinetobacter baumannii: pathogenesis, global resistance, mechanisms of resistance, treatment options, and alternative modalities

Acinetobacter baumannii, once considered a low-category pathogen, has emerged as an obstinate infectious agent. The scientific community is paying more attention to this pathogen due to its stubbornness to last resort antimicrobials, including carbapenems, colistin, and tigecycline, its high prevalence of infections in the hospital setting, and significantly increased rate of community-acquired infections by this organism over the past decade. It has given the fear of pre-antibiotic era to the world. To further enhance our understanding about this pathogen, in this review, we discuss its taxonomy, pathogenesis, current treatment options, global resistance rates, mechanisms of its resistance against various groups of antimicrobials, and future therapeutics.

Evaluation of Polymyxin B Susceptibility Profile and Detection of Drug Resistance Genes among Acinetobacter Baumannii Clinical Isolates in Tehran, Iran during 2015-2016

Acinetobacter baumannii is an important opportunistic pathogen, responsible for approximately 10% of all gram-negative nosocomial infection. The aim of this study was to determine aminoglycoside and quinolone resistance genes and their antimicrobial susceptibility profile in the clinically A. baumannii. In this cross-sectional study, a total of 100 nonduplicative A. baumannii isolates were collected from different clinical samples. Antimicrobial susceptibility test was performed by disk diffusion method. QnrA, anrB, qnrS, aac(3)-IIa, and aac(6')-Ib genes were identified using PCR method. The results of antibiotic susceptibility test showed that polymyxin B was the most effective antimicrobial against A. baumannii. 97%, 95% and 82% of isolates were resistant to cefepime, ceftriaxone, and amikacin, respectively. The molecular distribution of aac(3)-IIa, aac(6')-Ib, and qnrA genes were 45%, 50%, and 50% of isolates, respectively. However, qnrB and qnrS genes could not be detected in any strain. This study showed that polymyxin B was the best drug against A. baumannii clinical isolates. This data is also valid for polymyxin E (colistin), which is mostly used in clinics. There is a high level of resistance genes among clinical A. baumannii isolates. This high prevalence rate highlights the necessity for the development of rapid diagnostic assays and continuous monitoring of antibiotic resistance.

Cloning of ompA gene from Acinetobacter baumannii into the eukaryotic expression vector pBudCE4.1 as DNA vaccine

Antibiotic resistant features of Acinetobacter baumannii is partly due to the decreased outer membrane proteins (OMPs) permeability. The OmpA is one of the most conserved proteins among A. baumannii with a considerable antigenic potential to stimulate the multidimensional immune system responses. The present study was aimed to clone the ompA gene into the eukaryotic expression vector with potential as DNA vaccine. The ompA gene of A. baumannii was amplified using polymerase chain reaction (PCR). The target DNA was cloned and sub-cloned into the pTZ57R/T and pBudCE4.1 vectors, respectively. The recombinant vectors containing ompA were then validated using colony PCR, vector sequencing and double-digestion strategies. The pBudCE4.1-ompA recombinant plasmid was transfected into the human dermal fibroblast cells (HDF) and presence of ompA transcript and protein was evaluated using reverse transcribed-PCR (RT-PCR) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Our finding from colony PCR, sequencing and enzyme double digestion result confirmed that target gene has been successfully inserted into the pTZ57RT and pBudCE4.1. The presence of an expected band (1112 bp) in RT-PCR as wells as a ~ 38 kDa band during SDS-PAGE showed that the recombinant pBudCE4.1-ompA construct was efficiently transfected into the HDF cells and expressed. Altogether, our observation demonstrated that the recombinant pBudCE4.1-ompA construct was successfully produced although further experiments are needed.

Efficacy of titanium dioxide nanoparticle spray to disinfect mobile phones used by endodontist: A bacteriological study

Aim:

The objectives of this study were to determine the bacterial contamination of the mobile phones that were used by the endodontist in comparison with the general dentist and also to determine the usefulness of titanium dioxide nanospray (TiO₂ NS) in mobile phone decontamination.

Materials and Methods:

Samples from the 60 mobile phones were taken using moist sterile swabs before, 10 min, and 1 week after the use of TiO₂ NS. Before collection of the swabs, the participants' informed consent was obtained. Samples obtained were cultured on blood agar to identify bacterial isolates.

Results:

All 60 mobile phone cultures were found to be culture positive. There was a significant reduction in the mean number of colony-forming units after decontamination with TiO₂ NS (P < 0.001).

Conclusions:

The results from this study showed that the mobile phones may act as an important source of nosocomial pathogens and TiO₂ NS would be an effective decontaminant. Therefore, it is important for dental professionals to practice routine mobile phone disinfection protocol to reduce the chances of occurrence of nosocomial infections.

A new subclass of intrinsic aminoglycoside nucleotidyltransferases, ANT(3")-II, is horizontally transferred among Acinetobacter spp. by homologous recombination

The emergence and spread of antibiotic resistance among Acinetobacter spp. have been investigated extensively. Most studies focused on the multiple antibiotic resistance genes located on plasmids or genomic resistance islands. On the other hand, the mechanisms controlling intrinsic resistance are still not well understood. In this study, we identified the novel subclass of aminoglycoside nucleotidyltransferase ANT(3")-II in Acinetobacter spp., which comprised numerous variants distributed among three main clades. All members of this subclass can inactivate streptomycin and spectinomycin. The three ant(3")-II genes, encoding for the three ANT(3")-II clades, are widely distributed in the genus Acinetobacter and always located in the same conserved genomic region. According to their prevalence, these genes are intrinsic in Acinetobacter baumannii, Acinetobacter pittii, and Acinetobacter gyllenbergii. We also demonstrated that the ant(3")-II genes are located in a homologous recombination hotspot and were recurrently transferred among Acinetobacter species. In conclusion, our findings demonstrated a novel mechanism of natural resistance in Acinetobacter spp., identified a novel subclass of aminoglycoside nucleotidyltransferase and provided new insight into the evolutionary history of intrinsic resistance genes.

The level of interest in intrinsic resistance genes has increased recently, and one of reasons is that their mobilization could lead to emergence of resistant pathogens. Insertion sequences (ISs) or plasmids can capture intrinsic resistance genes and disseminate them in bacterial populations. In this study, we identified a novel subclass of aminoglycoside nucleotidyltransferases which are intrinsic in A. baumannii and other Acinetobacter species. The genes encoding the aminoglycoside nucleotidyltransferase were frequently horizontally transferred between different Acinetobacter species by homologous recombination. This work reports a novel mechanism of natural resistance in Acinetobacter and an overlooked pathway for the dissemination of resistance among species in this genus.