Biofilm formation is not an independent risk factor for mortality in patients with Acinetobacter baumannii bacteremia

In the past decades, due to the high prevalence of the antibiotic-resistant isolates of Acinetobacter baumannii, it has emerged as one of the most troublesome pathogens threatening the global healthcare system. Furthermore, this pathogen has the ability to form biofilms, which is another effective mechanism by which it survives in the presence of antibiotics. However, the clinical impact of biofilm-forming A. baumannii isolates on patients with bacteremia is largely unknown. This retrospective study was conducted at five medical centers in Taiwan over a 9-year period. A total of 252 and 459 patients with bacteremia caused by biofilm- and non-biofilm-forming isolates of A. baumannii, respectively, were enrolled. The clinical demographics, antimicrobial susceptibility, biofilm-forming ability, and patient clinical outcomes were analyzed. The biofilm-forming ability of the isolates was assessed using a microtiter plate assay. Multivariate analysis revealed the higher APACHE II score, shock status, lack of appropriate antimicrobial therapy, and carbapenem resistance of the infected strain were independent risk factors of 28-day mortality in the patients with A. baumannii bacteremia. However, there was no significant difference between the 28-day survival and non-survival groups, in terms of the biofilm forming ability. Compared to the patients infected with non-biofilm-forming isolates, those infected with biofilm-forming isolates had a lower in-hospital mortality rate. Patients with either congestive heart failure, underlying hematological malignancy, or chemotherapy recipients were more likely to become infected with the biofilm-forming isolates. Multivariate analysis showed congestive heart failure was an independent risk factor of infection with biofilm-forming isolates, while those with arterial lines tended to be infected with non-biofilm-forming isolates. There were no significant differences in the sources of infection between the biofilm-forming and non-biofilm-forming isolate groups. Carbapenem susceptibility was also similar between these groups. In conclusion, the patients infected with the biofilm-forming isolates of the A. baumannii exhibited different clinical features than those infected with non-biofilm-forming isolates. The biofilm-forming ability of A. baumannii may also influence the antibiotic susceptibility of its isolates. However, it was not an independent risk factor for a 28-day mortality in the patients with bacteremia.

Epidemiology of carbapenem resistant Acinetobacter baumannii in New Zealand

AIM

Carbapenem resistant Acinetobacter baumannii have limited treatment options and a propensity to cause hospital outbreaks. In recent years an increase in their detection has been observed in New Zealand. This study aimed to describe the molecular epidemiology of these isolates.

METHOD

This study utilised carbapenem resistant A. baumannii complex isolates identified across New Zealand between January 2010 to April 2018. Whole genome sequence analysis and associated demographic information was used to contextualise local isolates within the global epidemiology and establish the relationship between isolates.

RESULTS

Thirty-three carbapenem resistant A. baumannii complex isolates (31 A. baumannii sensu stricto) were identified. Twenty-four (73%) were from January 2015 onwards. Twenty-four (73%) had an identifiable epidemiological link to overseas hospitalisation. Twenty-three (74%) of 31 A. baumannii sensu stricto were sequence type (ST) 2 (Pasteur scheme). Phylogenetic analysis identified three ST2 clusters. The largest cluster, of 12 isolates, was from 2015 onwards; with nine (75%) associated with recent hospitalisation in Fiji or Samoa.

CONCLUSION

Increasing numbers of carbapenem resistant A. baumannii are being identified in New Zealand. Our data show that this is in large part associated with transnational spread of a single A. baumannii sensu stricto ST 2 strain between Fiji, Samoa and New Zealand.

Acinetobacter baumannii Sampled from Cattle and Pigs Represent Novel Clones

Acinetobacter baumannii is a very important human pathogen. Nonetheless, we know very little about nonhuman isolates of A. baumannii. Here, we determine the genomic identity of 15 Scottish cattle and pig isolates, as well as their antibiotic and virulence genetic determinants, and compare them with 148 genomes from the main human clinical international clones. Our results demonstrate that cattle and pig isolates represent novel clones well separated from the major international clones. Furthermore, these new clones showed fewer antibiotic resistance genes and may have fewer virulence genes than human clinical isolates. IMPORTANCE Over the last decades, huge amounts of information have been obtained for clinical isolates of A. baumannii and the clones they belong to. In contrast, very little is known about the genomic identity and the genomic basis for virulence and resistance of animal isolates. To fulfil this gap, we conducted a genomic epidemiology study of 15 Scottish cattle and pig isolates in the context of almost 150 genomes belonging to the main international clones of A. baumannii. Our findings show that these animal isolates represent novel clones clearly different from the major international clones. Furthermore, these new clones are distinct in nature considering both antibiotic resistance and virulence when compared with their human clinical counterparts.

[Risk factors and resistance patterns of invasive Acinetobacter Baumannii infection in Children]

Objective: To understand the risk factors and antibiotics-resistant patterns of invasive Acinetobacter baumannii infection in Children. Methods: This retrospective study was conducted in 6 tertiary hospitals from January 2016 to December 2018. The basic information, clinical data and the results of antimicrobial susceptibility testing were collected from the 98 pediatric inpatients with Acinetobacter baumannii isolated from blood or cerebrospinal fluid and analyzed. According to the susceptibility of the infected strains to carbapenems, they were divided into carbapenem-sensitive Acinetobacter baumannii (CSAB) group and carbapenem-resistant Acinetobacter baumannii (CRAB) group. According to the possible sources of infection, they were divided into nosocomial infection group and community infection group. Chi-square test or Fisher exact test were used to analyze categorical variables and rank sum test were used to analyze continuous variables. The risk factors of invasive CRAB infection in children were analyzed by Logistic regression. Result: There were 56 males and 42 females in 98 cases. The onset age of patients was 8 (2, 24) months. There were 62 cases (63%) from rural area. A total of 87 cases (89%) were confirmed with bloodstream infection, and 12 cases (12%) confirmed with meningitis (1 case was accompanied with bloodstream infection). In these patients, 66 cases (67%) received invasive medical procedures or surgery, 54 cases (55%) received carbapenems-containing therapy. Twenty-four cases were infected with CRAB, and 74 cases with CSAB. The onset age of cases in CRAB group was lower than that in CSAB group (4 (1, 9) vs. 10 (4, 24) months, Z=-2.16, P=0.031). The proportions of hospitalization in intensive care unit, carbapenem antibiotics using, pneumonia and adverse prognosis in CRAB group were higher than those in CSAB group (6 cases (25%) vs. 4 cases (5%), 18 cases (75%) vs. 36 cases (49%), 17 cases (71%) vs. 17 cases (23%), 6 cases (25%) vs. 4 cases (5%), χ²=5.61, 5.09, 18.32, 5.61, all P<0.05). Seventy-seven cases were nosocomial infection and 21 cases were hospital-acquired infection. The proportion of children hospitalized in high-risk wards for nosocomial infections, length of hospitalization, number of antimicrobial therapy received and duration of antimicrobial therapy were higher in the hospital associated infection group than those in the community acquired infection group (all P<0.05). Logistic regression analysis showed that children from rural area (OR=8.42, 95%CI 1.45-48.88), prior mechanical ventilation (OR=12.62, 95%CI 1.31-121.76), and prior antibiotic therapy (OR=4.90, 95%CI 1.35-17.72) were independent risk factors for CRAB infection. The resistance percentage of CSAB isolates to many classes of antibiotics was <6% except to gentamicin, which was as high as 20% (13/65). All CRAB isolates of resistant to ampicillin-sulbactam (20/20), cefepime (23/23), piperacillin (17/17), meropenem (23/23) and imipenem (24/24) were 100%. The resistance percentage to other antibiotics were up to 42%-96%. Conclusions: Most of invasive Acinetobacter baumannii infection in children in China are hospital-acquired. The outcome of invasive CRAB infection was poorer than that of CSAB infection. The drug resistance rate of CRAB strains isolated is high. Living in rural area, prior invasive mechanical ventilation and prior antibiotic therapy were independent risk factors for invasive CRAB infection. The prevention and control of nosocomial infection and appropriate use of antibiotics to reduce Acinetobacter baumannii infection.

Emergence of carbapenem resistant Acinetobacter baumannii clonal complexes CC2 and CC10 among fecal carriages in an educational hospital

Carbapenem-resistant Acinetobacter baumannii strains are increasing worldwide. In this study, samples were collected from hospital environments, extra hospital environments, and fecal carriages. 76% (89/117) of bacterial isolates were detected as A. baumannii strains. The imipenem resistance in the hospital environment, fecal carriages, extra hospital environments, and clinical isolates was 37.7% (17/45), 100% (9/9), 0% (0/45), and 92.9% (92/99), respectively. The blaVIM and blaOXA-23 were detected in 6.6% (3/45) and 2.2% (1/45) of strains isolated from hospital environments. Interestingly, strains isolated from fecal carriages had blaVIM, blaOXA-23, and blaIMP genes which resembled carbapenem resistance genes in clinical strains. The structure of clonal relatedness among all non-clinical isolates was as follows: CC2, 37% (33/89); CC1, 22.4% (20/89); CC3, 12.3% (11/89); CC25, 7.8% (7/89); CC10, 4.4% (4/89) and CC15, 2.2% (2/89). Comparison of clonal relatedness among clinical and non-clinical isolates indicated that widespread clones including CC2, CC3, and CC10 were common clonal complexes between two categories.

The Changes in Epidemiology of Imipenem-Resistant Acinetobacter baumannii Bacteremia in a Pediatric Intensive Care Unit for 17 Years

BACKGROUND

Acinetobacter baumannii infections cause high morbidity and mortality in intensive care unit (ICU) patients. However, there are limited data on the changes of long-term epidemiology of imipenem resistance in A. baumannii bacteremia among pediatric ICU (PICU) patients.

METHODS

A retrospective review was performed on patients with A. baumannii bacteremia in PICU of a tertiary teaching hospital from 2000 to 2016. Antimicrobial susceptibility tests, multilocus sequence typing (MLST), and polymerase chain reaction for antimicrobial resistance genes were performed for available isolates.

RESULTS

A. baumannii bacteremia occurred in 27 patients; imipenem-sensitive A. baumannii (ISAB, n = 10, 37%) and imipenem-resistant A. baumannii (IRAB, n = 17, 63%). There was a clear shift in the antibiogram of A. baumannii during the study period. From 2000 to 2003, all isolates were ISAB (n = 6). From 2005 to 2008, both IRAB (n = 5) and ISAB (n = 4) were isolated. However, from 2009, all isolates were IRAB (n = 12). Ten isolates were available for additional test and confirmed as IRAB. MLST analysis showed that among 10 isolates, sequence type 138 was predominant (n = 7). All 10 isolates were positive for OXA-23-like and OXA-51-like carbapenemase. Of 27 bacteremia patients, 11 were male (41%), the median age at bacteremia onset was 5.2 years (range, 0-18.6 years). In 33% (9/27) of patients, A. baumannii was isolated from tracheal aspirate prior to development of bacteremia (median, 8 days; range, 5-124 days). The overall case-fatality rate was 63% (17/27) within 28 days. There was no statistical difference in the case fatality rate between ISAB and IRAB groups (50% vs. 71%; P = 0.422).

CONCLUSION

IRAB bacteremia causes serious threat in patients in PICU. Proactive infection control measures and antimicrobial stewardship are crucial for managing IRAB infection in PICU.

Predictors of survival from Acinetobacter in Saudi Arabian intensive care units: A prospective, one-year, six-city, ten-center cohort study

BACKGROUND

Antibiotic-resistant Acinetobacter baumannii is a continuously-emerging worldwide health crisis, with mortality rates approaching 50% in intensive care unit (ICU) patients. The objective of this study was to evaluate regional, patient-related, and organism-related predictors of survival among critically-ill patients with confirmed Acinetobacter infection.

METHODS

This prospective cohort study was conducted within ten ICUs across six geographically- and climatologically-distinct cities across Saudi Arabia over 13 months.

RESULTS

Of 169 patients with confirmed Acinetobacter infection enrolled in the study, 80 (47.6%) died. Survivors were statistically younger, predominantly male, more likely to be admitted for trauma, less likely to have hypertension, diabetes, or have undergone hemodialysis, and more likely to have been treated with antibiotics prior to having a positive culture for Acinetobacter, but less likely to have received an aminoglycoside. Survivors also had lower baseline APACHE II and SOFA scores and were infected with stains of Acinetobacter that had less meropenem- or colistin-resistance. Multivariate analysis identified the following independent predictors of survival: younger age, lower ICU-day#1 APACHE-II and ICU-day#3 SOFA scores, being admitted for trauma, and having no history of hemodialysis.

CONCLUSIONS

Patient-related factors outweigh regional and hospital-related factors as predictors of survival among critically-ill patients with Acinetobacter infection.

Rate and Risk Factors for Carbapenem Resistant Acinetobacter baumannii Clinical Infections in Colonized Patients

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii (CRAB) is an important cause of nosocomial infections. Active surveillance for CRAB carriage to identify and isolate colonized patients is used to reduce transmission.

OBJECTIVES

To assess the rate and risks of clinical infection among CRAB-carrier and non-carrier patients.

METHODS

Hospitalized patients from whom CRAB screening-cultures were obtained between January and June 2018 were identified retrospectively. All CRAB-carriers were compared to a convenient sample of non-carriers and were followed to detect development of CRAB clinical infection during admission.

RESULTS

We compared 115 CRAB carriers to 166 non-carriers. The median age in the study group was 76 years (IQR 71-87) vs. 65 years (55-79) in the non-carriers group (P < 0.001). Residence in a nursing facility, debilitated state, and admission to medical wards vs. intensive care units were more frequent among CRAB-carriers (P < 0.001). Mechanically ventilated patients included 51 CRAB carriers (44%) and 102 non-carriers (61%). Clinical infection developed in 49 patients (17%), primarily CRAB pneumonia. Of the CRAB-carriers and non-carriers, 26/115 (23%) and 23/166 (14%), respectively, developed a clinical infection (P = 0.05). One-third of the ventilated patients were infected. Debilitated state and antibiotic treatment during hospitalization were linked to higher infection rates (P = 0.01). Adjusted analysis showed that mechanical ventilation and CRAB colonization were strongly associated with clinical infection (P < 0.05).

CONCLUSIONS

The rate of CRAB infection among carriers was high. Mechanical ventilation and CRAB colonization were associated with CRAB clinical infection, primarily pneumonia.

Whole-genome sequencing for the characterization of resistance mechanisms and epidemiology of colistin-resistant Acinetobacter baumannii

Background

Multidrug-resistant Acinetobacter baumannii is an important causal pathogen of healthcare-associated infections, and colistin-resistant strains have recently emerged owing to the increased use of colistin. Using next-generation sequencing (NGS), a single whole-genome sequencing (WGS) protocol can identify and type pathogens, analyze genetic relationships among different pathogens, predict pathogenic transmissions, and detect antibiotic resistance genes. However, only a few studies have applied NGS in studying the resistance mechanism and epidemiology of colistin-resistant A. baumannii. This study aimed to elucidate the resistance mechanism of colistin-resistant A. baumannii and analyze its molecular epidemiology through WGS.

Materials and methods

The subjects in this study were patients who visited a university hospital between 2014 and 2018. Thirty colistin-resistant strains with high minimum inhibitory concentrations were selected from various patient samples, and WGS was performed. Comparative genomic analysis was performed for the 27 colistin-resistant A. baumannii strains using a colistin-susceptible strain as the reference genome.

Results

The WGS analysis found no mutation for lpxA, lpxC, lpx D, pmrA, pmrB, and mcr1, the genes known to be associated with colistin resistance. Fifty-seven coding sequences (CDS) showed differences; they included 13 CDS with known names and functions that contained 21 genes. From the whole-genome multi-locus sequence typing (wgMLST) and single nucleotide polymorphism (SNP) analyses, two major clusters were found for the colistin-resistant A. baumannii strains. However, no differences were observed by the time of detection for each cluster, the samples, the pattern of antibiotic resistance, or the patient characteristics. In the conventional MLST following the Oxford scheme, the typing result showed ST1809, ST451, ST191, ST1837, and ST369 in the global clone 2 (GC2), without any relation with the results of wgMLST and SNP analyses.

Conclusion

Based on the findings of the resistance gene analysis through WGS and comparative genomic analysis, the potential genes associated with colistin-resistance or CDS were examined. Furthermore, the analysis of molecular epidemiology through WGS regarding colistin-resistant A. baumannii may prove helpful in preventing infection by multidrug-resistant bacteria and controlling healthcare-associated infections.

Isolation of extensively drug resistant Acinetobacter baumannii from environmental surfaces inside intensive care units

BACKGROUND

Acinetobacter baumannii is a nosocomial pathogen that has emerged as a major threat in the health-care settings, particularly intensive care units (ICUs). The aim of this study was to investigate the prevalence of A. baumannii in the environment of intensive care and emergency units in 4 hospitals in Jordan.

METHODS

A total of 311 surface and 26 air samples were collected from 6 different ICUs and 2 emergency units. Examined high-touch surfaces included bed rails, sinks, food tables, trolley handles, ventilator inlets, blankets, sheets, door handles, light switches, bedside tables and drawers, curtains, normal saline stands and neonatal incubators. A. baumannii isolates were identified by CHROMagar and confirmed using 2 different PCR assays. All obtained isolates were characterized for their antibiotic resistance phenotypes, biofilm formation capacities and were typed by multi-locus sequence typing.

RESULTS

Of the 337 samples, 24 A. baumannii isolates were recovered, mostly from surfaces in the internal medicine ICUs. Among the 24 isolates, 10 isolates were classified as extensively-resistant (XDR), harbored the bla_OXA-23 like gene and able to form biofilms with varying capacities. ST2 was the most frequent sequence type, with all ST2 isolates classified as XDRs.

CONCLUSIONS

Our results showed that high-touch surfaces of adult and pediatric ICUs were contaminated with XDR A. baumannii isolates. Therefore, the cleaning practices of the surfaces and equipment surrounding ICU patients should be optimized, and health-care workers should continuously wash their hands and change their gloves constantly to control the spread of this pathogen.

Genomic insights of Acinetobacter baumannii ST374 reveal wide and increasing resistome and virulome

WGS-based surveillance has significantly improved the ability to track global spread and emergence of multidrug-resistant clones of clinically relevant pathogens. In this study, we performed the genomic characterization and comparative analysis of an Acinetobacter baumannii (strain Ac56) belonging to the sequence type ST374, which was isolated for the first time in Brazil, in 1996. Genomic analysis of Ac56 predicted a total of 5373 genes, with 3012 being identical across nine genomes of A. baumannii isolates of ST374 from European, Asian, North and South American countries. GoeBURST analysis grouped ST374 lineages into clonal complex CC3 (international clone IC-III). Resistome analysis of ST374 clone predicted genes associated with resistance to heavy metals and clinically relevant beta-lactams and aminoglycosides antibiotics. In this regard, in two closely related A. baumannii strains, the intrinsic bla_ADC gene was linked to the insertion sequence ISAba1; including the Ac56 strain, where it has been possibly associated with intermediate susceptibility to meropenem. Other four carbapenem-resistant A. baumannii strains carried the ISAba1/bla_OXA-23 gene array, which was associated with the transposon Tn2008 or with Tn2006 in an AbaR4-type resistance island. While most virulence genes were shared for A. baumannii strains of ST374, three isolates from Thailand harbored KL49 capsular loci, previously identified in the hypervirulent A. baumannii LAC-4 strain. Analysis of thirty-four predicted plasmids showed eight major groups, of which GR-6 (LN-1) and GR-2 (LN-2) were prevalent. All strains, including the earliest isolate Ac56 harbored at least one complete prophage, whereas none CRISPR-associated (cas) gene was detected. In summary, genomic data of A. baumannii ST374 reveal a potential of this lineage to become a successful clone.

Antibiotic Resistance Pattern Of Acinetobacter Baumannii Isolated From Bacteremia Patients In Pakistan

BACKGROUND

Acinetobacter baumannii causes a number of life-threatening infections in Hospitalized patients attributed to its ability to develop resistance against multiple antibiotics. The current scrutinisation is aimed to observe the prevalence and antibiotic resistance profile of A. baumannii strains isolated from blood of tertiary care Hospitalized patients in Lahore, Pakistan.

METHODS

This research is a retrospective study conducted over a period of one year where 1864 blood samples were collected from both male and female patients with septicaemia. Total 156 A. baumannii species were identified by conventional method and their antimicrobial resistance pattern against 22 antimicrobials (representing all known classes of antibiotics) was evaluated by Kirby Bauer disc diffusion method. MICs of colistin, polymyxin B and vancomycin against A. baumannii were calculated by E test and broth dilution method.

RESULTS

More males (n=97, 62%) were found infected than females (n=59, 38%). The spreading rate of A. baumannii was highest (n=101, 65%) in patients of age ≤20 years, and lowest (n=12, 7%) in the patients with the age of 41-60 years. Most of the strains of A. baumannii (n=118, 75.6%) were found to be MDR (multi drug resistant), 37 (23.7%) strains were XDR (Extensively drug-resistant) and only 1 (0.05%) strain was PDR (pandrug resistant). All the strains were sensitive to minocycline and tigecycline whereas highest non-susceptibility (n=144, 92%) was seen against Ampicillin-Sulbactam. Most of the strains demonstrated resistance against carbapenem and cephalosporin beckoning that A. baumannii can no longer be considered for salvage therapy by carbapenem. MICs of colistin, polymyxin B and vancomycin against A. baumannii divulged polymixin B as the most effective drug.

CONCLUSIONS

Use of wide range of drugs has made A. baumannii multidrug resistant. Colistin, polymyxin B and vancomycin are the preferable drugs for the treatment of A. baumannii infections.

Reduction in the acquisition rate of carbapenem-resistant Acinetobacter baumannii (CRAB) after room privatization in an intensive care unit

BACKGROUND

Acinetobacter baumannii is one of the major pathogens responsible for healthcare-associated infections, especially in intensive care units (ICUs).

AIM

To evaluate the effect of room privatization in an ICU on the acquisition of carbapenem-resistant A. baumannii (CRAB).

METHODS

Between March and August 2017, a medical ICU was renovated from a multibed bay room to single rooms. Acquisition of CRAB was compared between patients admitted to the ICU over 18 months pre-renovation (September 2015 to February 2017) and post-renovation (September 2017 to February 2019). A Cox proportional hazard model was used with adjustment for demographics and comorbidities.

FINDINGS

Of the 901 patients, who contributed 8,276 patient-days, 95 (10.5%) acquired CRAB during their ICU stay. The CRAB acquisition rate was significantly higher during the pre-renovation period (1.87 per 100 patient-days) than during the post-renovation period (0.39 per 100 patient-days) (P < 0.001). In the multivariable Cox regression model, CRAB acquisition was significantly associated with the presence of a feeding tube (adjusted hazard ratio [aHR], 6.08; 95% confidence interval [CI], 2.46-15.06; P < 0.001), continuous renal replacement therapy (aHR, 1.66; 95% CI, 1.09-2.53; P = 0.019) and admission after renovation of the ICU to single rooms (aHR, 0.23; 95% CI, 0.12-0.41; P < 0.001).

CONCLUSIONS

Renovation of ICUs to single rooms is an efficient strategy to prevent transmission of multidrug-resistant organisms and hospital-acquired infections.

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii isolated from three major hospitals in Jordan

BACKGROUND

In the last decade, incidences of carbapenem-resistant Acinetobacter baumannii have been increasingly reported worldwide. Consequently, A. baumannii was included in the World Health Organization's new list of critical pathogens, for which new drugs are desperately needed. The objective of this research was to study the molecular epidemiology and antimicrobial susceptibility of clinical carbapenem-resistant A. baumannii isolated from Jordanian hospitals.

METHODS

A total of 78 A. baumannii and 8 Acinetobacter spp. isolates were collected from three major hospitals in Jordan during 2018. Disc diffusion and microdilution methods were used to test their susceptibility against 19 antimicrobial agents. Multilocus sequence typing (MLST) was performed using the Pasteur scheme, followed by eBURST analysis for all isolates. PCR was used to detect β-lactam resistance genes, bla_OXA-23-like , bla_OXA-51-like , and bla_NDM-1 .

RESULTS

Of the 86 tested isolates, 78 (90.6%) exhibited resistance to carbapenems, whereas no resistance was recorded to tigecycline or polymyxins. Based on the resistance profiles, 10.4% and 84.8% of isolates were classified into multidrug resistant (MDR) or extensively drug resistant (XDR), respectively. The most prevalent carbapenems resistance genes amongst isolates were bla_OXA-51-Like (89.5%), followed by bla_OXA-23-Like (88.3%) and bla_NDM-1 (10.4%). MLST revealed the presence of 19 sequence types (STs), belonging to eight different international complexes. The most commonly detected clonal complex (CC) was CC2, representing 64% of all typed isolates.

CONCLUSIONS

This is the first study to report the clonal diversity of A. baumannii isolates in Jordan. A high incidence of carbapenem resistance was detected in the isolates investigated. In addition, our findings provided evidence for the widespread of bla_OXA-23-like harbouring carbapenem-resistant A. baumannii and belonging to CC2. The number of XDR isolates identified in this study is alarming. Thus, periodic surveillance and molecular epidemiological studies of resistance factors are important to improve treatment outcomes and prevent the spread of A. baumannii infections.

Association between antibiotic pressure and the risk of colonization/infection by multidrug-resistant Acinetobacter baumannii complex: a time series analysis

Introduction. To analyze the association between antibiotic pressure and the risk of colonization/infection by Acinetobacter baumannii complex (AB), evaluating both the individual and general prescriptions of antibiotics. Methods. This is an analytical, observational, case-control study on patients admitted to an Intensive Care Unit (ICU) during an AB outbreak (14 months). A five-year time series was constructed with the monthly incidence of cases of infection/colonization with strains of AB resistant to each antibiotic administered and with the monthly consumption of these antibiotics in the ICU. Results. We identified 40 patients either infected (23) or colonized (17) by AB and 73 controls. We found an epidemic multidrug-resistant clone of AB in 75% of cases. Risk factors associated with the development of AB infection/colonization were: greater use of medical instruments, the presence of a tracheostomy, cutaneous ulcers, surgical lesions and prior antibiotic therapies. The regression analysis of individual use of antibiotics showed that prior treatment with ceftazidime, ceftriaxone, amoxicillin/clavulanate, imipenem, levofloxacin, linezolid, and vancomycin was a risk factor for acquiring AB. ARIMA models showed that the relationship were greatest and statistically significant when the treatment occurred between 6 months (ceftazidime) and 9 months (imipenem and levofloxacin) prior. Conclusions. The dynamic and aggregate relationship between the incidence of infection/colonization by multidrug-resistant strains of AB and prior antibiotic treatment was statistically significant for intervals of 6 to 9 months.

Frequency And Clinical Spectrum Of Multidrug Resistant Acinetobacter Baumannii As A Significant Nosocomial Pathogen In Intensive Care Unit Patients

BACKGROUND

Acinetobacter baumannii has emerged as one of the leading causes of multidrug resistant nosocomial infections worldwide. It is able to survive in hospital environment and build up diverse resistance mechanisms making it difficult to treat with current antibiotics. Objective: It was to determine the frequency and patterns of Acinetobacter baumannii in intensive care units (ICU) settings.

METHODS

A cross sectional study was carried out in the Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi, from 1st July 2017 to 30th June 2019. A total of 603 non-duplicate clinical specimens were received from intensive care units. Specimens yielding growth of multidrug resistant Acinetobacter baumannii, were evaluated as per standard protocol. The antimicrobial sensitivity testing was performed as per Clinical and Laboratory Standard Institute guidelines (2017-2018).

RESULTS

Among Acinetobacter baumannii (310 isolates), 5% were multidrug resistant, 93% extensively drug resistant and 1% pan drug resistant. Percentage of carbapenem resistant strains was 92%. In drugs like tigecycline and polymyxin, resistance was noted as 73% and 1% respectively. High yield of this superbug was mainly obtained from respiratory specimens (43.5%), whereas 24% were detected from wound infections and 29% from other samples. .

CONCLUSION

This study showed a rapidly increasing resistance in Acinetobacter baumannii. Therefore, polymyxin remains the only option in our intensive care units, but its usage as empirical therapy in our setting has led to the emergence of resistance to this drug. Implementing infection control practices, antimicrobial stewardship and restricted use of polymyxin can play a significant role in reducing health care burden.

Genomic surveillance of Acinetobacter baumannii in the Philippines, 2013-2014

OBJECTIVE

Acinetobacter baumannii is an opportunistic nosocomial pathogen that has increasingly become resistant to carbapenems worldwide. In the Philippines, rates of carbapenem resistance and multidrug resistance are above 50%. We undertook a genomic study of carbapenem-resistant A. baumannii in the Philippines to characterize the population diversity and antimicrobial resistance mechanisms.

METHODS

We sequenced the whole genomes of 117 A. baumannii isolates recovered by 16 hospitals in the Philippines between 2013 and 2014. From the genome sequences, we determined the multilocus sequence type, presence of acquired determinants of antimicrobial resistance and relatedness between isolates. We also compared the phenotypic and genotypic resistance results.

RESULTS

Carbapenem resistance was mainly explained by acquisition of the class-D β-lactamase gene blaOXA-23. The concordance between phenotypic and genotypic resistance to imipenem was 98.15%, and it was 94.97% overall for the seven antibiotics analysed. Twenty-two different sequence types were identified, including 7 novel types. The population was dominated by the high-risk international clone 2 (i.e. clonal complex 92), in particular by ST195 and ST208 and their single locus variants. Using whole-genome sequencing, we identified local clusters representing potentially undetected nosocomial outbreaks, as well as multihospital clusters that indicated interhospital dissemination. Comparison with global genomes suggested that the establishment of carbapenem-resistant international clone 2 in the Philippines is likely the result of clonal expansion and geographical dissemination, and at least partly explained by inadequate hospital infection control and prevention.

DISCUSSION

This is the first extensive genomic study of carbapenem-resistant A. baumannii in the Philippines, and it underscores the importance of hospital infection control and prevention measures to contain high-risk clones.

Co-infection of ST2IP carbapenem-resistant Acinetobacter baumannii with SARS-CoV-2 in the patients admitted to a Tehran tertiary referral hospital

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii (CRAB) is among the most concerning cause of healthcare-associated infections (HAI) due to its high level of antibiotic resistance and high mortality. In the era of the COVID-19 pandemic, the key priority of infection control committees is to contain the dissemination of antibiotic resistant Gram-negative bacteria. Here, we aimed to timely recognize the emergence of CRAB in COVID-19 cases admitted to the wards of a tertiary referral hospital and to identify the genetic relatedness of the isolates.

METHODS

From 30 March to 30 May 2020, a total of 242 clinical samples from COVID-19 cases were screened for CRAB isolates using standard microbiologic and antibiotic susceptibility tests. The PCRs targeting oxa23, oxa24, oxa58, blaTEM and blaNDM-1 genes were performed. Two multiplex PCRs for identifying the global clones (GC) of A. baumannii were also performed. The sequence type of CRABs was determined using Institut Pasteur (IP) multilocus sequence typing (MLST) scheme.

RESULTS

Eighteen CRAB isolates were recovered from COVID-19 patients with the mean age of 63.94 ± 13.8 years. All but 4 COVID-19 patients co-infected with CRAB were suffering from an underlying disease. Death was recorded as the outcome in ICUs for 9 (50%) COVID-19 patients co-infected with CRAB. The CRAB isolates belong to GC2 and ST2IP and carried the oxa23 carbapenem resistance gene.

CONCLUSION

This study demonstrated the co-infection of CRAB isolates and SARS-CoV-2 in the patients admitted to different ICUs at a referral hospital in Tehran. The CRAB isolates were found to belong to ST2IP, share the oxa23 gene and to have caused several outbreaks in the wards admitting COVID-19 patients.

A comprehensive approach to ending an outbreak of rare blaOXA-72 gene-positive carbapenem-resistant Acinetobacter baumannii at a Community Hospital, Kansas City, MO, 2018

We identified a cluster of extensively drug-resistant, carbapenemase gene-positive, carbapenem-resistant Acinetobacter baumannii (CP-CRAB) at a teaching hospital in Kansas City. Extensively drug-resistant CRAB was identified from eight patients and 3% of environmental cultures. We used patient cohorting and targeted environmental disinfection to stop transmission. After implementation of these measures, no additional cases were identified.

Molecular characterization of carbapenem-resistant Acinetobacter baumannii clinical isolates from Egyptian patients

Acinetobacter baumannii (A. baumannii) represents a global threat owing to its ability to resist most of the currently available antimicrobial agents. Moreover, emergence of carbapenem resistant A. baumannii (CR-AB) isolates limits the available treatment options. Enzymatic degradation by variety of ß-lactamases, have been identified as the most common mechanism of carbapenem resistance in A. baumannii. The alarming increase in the prevalence of CR-AB necessitates continuous screening and molecular characterization to appreciate the problem. The present study was performed to assess the prevalence and characterize carbapenemases among 206 CR-AB isolated from various clinical specimens collected from different intensive care units at Kasr Al-Aini Hospital. All isolates were confirmed to be A. baumannii by detection of the blaOXA-51-like gene. Molecular screening of 13 common Ambler class bla carbapenemases genes in addition to insertion sequence (IS-1) upstream OXA-23 were performed by using four sets of multiplex PCR, followed by identification using gene sequencing technology. Among the investigated genes, the prevalence of blaOXA-23, and blaOXA-58 were 77.7%, and 1.9%, respectively. The ISAba1 was detected in 10% of the blaOXA-23 positive isolates. The prevalence of metallo-β-lactamases (MBLs) studied; blaNDM-1, blaSPM, blaVIM, blaSIM-1 were 11.7%, 6.3%, 0.5%, and 0.5% respectively. One of class A; bla KPC was detected in 10.7% of the investigated isolates. blaOXA-24/40, blaIMP, blaGES, blaVEB and blaGIM were not detected in any of the studied isolates. Moreover, 18.4% of the isolates have shown to harbor two or more of the screened bla genes. We concluded that the most prevalent type of ß-lactamases genes among CR-AB isolates collected from Egyptian patients were blaOXA-23 followed by blaNDM-1 and blaKPC.

Molecular Study of Nodulation Division Genes and Integron Genes in Acinetobacter baumannii

BACKGROUND

Acinetobacter is an opportunistic bacterial pathogen, primarily associated with hospital-acquired infections. Antibiotic resistance in Acinetobacter is mainly mediated by efflux systems. This study aimed to identify the prevalence of adeA, adeI, adeJ, and adeY genes in Acinetobacter baumannii (A. baumannii) by PCR, assess the presence of integron genes by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and relate the presence of these genes to antimicrobial resistance of the clinically isolated A. baumannii.

METHODS

The study included identification of Acinetobacter spp. and antimicrobial antibiotic susceptibility. PCR was performed for adeA, adeI, adeJ, and adeY genes. Detection of Integron (Intl) system was performed by PCR followed by restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The frequency of Ade genes among isolates were 66%, 62%, 60%, and 2% for AdeJ, AdeI, AdeA, and AdeY genes, respectively. The intI gene was detected in 10% of the isolates. There was a statistically significant difference in resistance to amikacin, gentamicin, and tetracycline between A. baumanii positive. The most frequent association was between AdeJ, AdeA, and AdeI (31%).

CONCLUSIONS

Our study highlighted the high prevalence of AdeJ, AdeI, and AdeA in A. baumannii. Integron gene was detected with considerable frequency. There was a statistically significant association of these genes with resistance to aminoglycosides and tetracycline.

AB569, a non-toxic combination of acidified nitrite and EDTA, is effective at killing the notorious Iraq/Afghanistan combat wound pathogens, multi-drug resistant Acinetobacter baumannii and Acinetobacter spp

Multi-drug resistant (MDR) Acinetobacter baumannii (Ab) and Acinetobacter spp. present monumental global health challenges. These organisms represent model Gram-negative pathogens with known antibiotic resistance and biofilm-forming properties. Herein, a novel, nontoxic biocide, AB569, consisting of acidified nitrite (A-NO₂^-) and ethylenediaminetetraacetic acid (EDTA), demonstrated bactericidal activity against all Ab and Acinetobacter spp. strains, respectively. Average fractional inhibitory concentrations (FICs) of 0.25 mM EDTA plus 4 mM A-NO₂^- were observed across several clinical reference and multiple combat wound isolates from the Iraq/Afghanistan wars. Importantly, toxicity testing on human dermal fibroblasts (HDFa) revealed an upper toxicity limit of 3 mM EDTA plus 64 mM A-NO₂^-, and thus are in the therapeutic range for effective Ab and Acinetobacter spp. treatment. Following treatment of Ab strain ATCC 19606 with AB569, quantitative PCR analysis of selected genes products to be responsive to AB569 revealed up-regulation of iron regulated genes involved in siderophore production, siderophore biosynthesis non-ribosomal peptide synthetase module (SBNRPSM), and siderophore biosynthesis protein monooxygenase (SBPM) when compared to untreated organisms. Taken together, treating Ab infections with AB569 at inhibitory concentrations reveals the potential clinical application of preventing Ab from gaining an early growth advantage during infection followed by extensive bactericidal activity upon subsequent exposures.

Diversity of Oxacillinases and Sequence Types in Carbapenem-Resistant Acinetobacter baumannii from Austria

Carbapenem-resistant Acinetobacter baumannii is a significant health problem worldwide. A multicenter study on A. baumannii was performed to investigate the molecular epidemiology and genetic background of carbapenem resistance of A. baumannii isolates collected from 2014–2017 in Austria. In total, 117 non-repetitive Acinetobacter spp. assigned to A. baumannii (n = 114) and A. pittii (n = 3) were collected from four centers in Austria. The isolates were uniformly resistant to piperacillin/tazobactam, ceftazidime, and carbapenems, and resistance to imipenem and meropenem was 97.4% and 98.2%, respectively. The most prominent OXA-types were OXA-58-like (46.5%) and OXA-23-like (41.2%), followed by OXA-24-like (10.5%), with notable regional differences. Carbapenem-hydrolyzing class D carbapenemases (CHDLs) were the only carbapenemases found in A.baumannii isolates in Austria since no metallo-β-lactamases (MBLs) nor KPC or GES carbapenemases were detected in any of the isolates. One-third of the isolates harbored multiple CHDLs. The population structure of A. baumannii isolates from Austria was found to be very diverse, while a total of twenty-three different sequence types (STs) were identified. The most frequent was ST195 found in 15.8%, followed by ST218 and ST231 equally found in 11.4% of isolates. Two new ST types, ST2025 and ST2026, were detected. In one A. pittii isolate, bla_OXA-143-like was detected for the first time in Austria.

[Carbapenamase OXA-23 like-producing Acinetobacter baumanii epidemic outbreak in a hospitalization unit.]

OBJECTIVE

Despite its great ubiquity and morbidity and mortality, the scientific evidence on the hospital control of multiresistant Acinetobacter baumanii (ABMR) outside the Intensive Care Units in Spain is scarce. The objective was to describe an epidemic outbreak by MRAB and analyze the effectiveness of the actions carried out.

METHODS

Prospective observational study of admitted-rotated patients in a multipathological control at the University Hospital of Guadalajara, Spain, during the outbreak (September 20-November 3, 2017); using Mambrino Electronic Health Record. A genetic study of the resistance mechanism and molecular characterization of the strains were carried out. Frequency measurements were estimated, with subsequent comparative analysis of cases vs controls.

RESULTS

The median age of the study population (N=138) was 83.2 years (Interquartile Range [IR]=69.7-90.1). There were 3 cases of ABMR infection among them. Thirteen percent required issolation, 17% because of MRAB. The MRAB incidence was 2.2 cases/100 admitted-rotated (mortality rate=33%). The excess stay for cases was 17±4.3 (95%CI=8.5-25.6), with an incidence density of 3 cases/10³ days. The responsible strain was carbapenemase OXA-23. We found a single case in the colonization study of contacts. No MRAB was isolated from environmental samples.

CONCLUSIONS

Along with epidemiological research, coordination and compliance with precautions; prompt identification and management of an outbreak are crucial to minimize the colonization pressure and to stop dissemination.

Investigation of Acinetobacter baumannii Activity in Vascular Surgery Units through Epidemiological Management Based on the Analysis of Antimicrobial Resistance, Biofilm Formation and Genotyping

Background/Objectives: The genus Acinetobacter demonstrates resistance to antibiotics and has been shown to spread in the hospital environment causing epidemic outbreaks among hospitalized patients. The objectives of the present study was to investigate the antibiotic resistance, biofilm formation, and clonality among Acinetobacter baumannii strains. Materials and Methods: The study involved 6 (I Outbreak) and 3 (II Outbreak) A. baumannii strains isolated from patients hospitalized in vascular surgery unit. Results: All tested A. baumannii strains were extensively drug resistant (XDR) and all the isolates were carbapenem-resistant and among them, all carried the bla_OXA-51 gene, the bla_OXA-24 gene, as well as the bla_OXA-23 gene. All of the investigated strains had the ability to form a biofilm, but all of them produced less biofilm than the reference strain. Multi-locus sequence typing (MLST) showed that all strains belonged to the ST2 clone. Pulsed-field gel electrophoresis (PFGE) divided the tested outbreak strains into two clones (A and B). Conclusion: This study shows a nosocomial spread of XDR A. baumannii ST2 having the bla_OXA-51 gene, the bla_OXA-24 gene, as well as the bla_OXA-23 gene, low biofilm formers, that was prevalent in the vascular surgery unit. To identify the current situation of vascular surgery departments targeted epidemiological investigation was needed. Effective implementation of infection control prevented the spread of the epidemic outbreaks.