Clinical and economic impact of multidrug resistance in nosocomial Acinetobacter baumannii bacteremia

The Burden of Acinetobacter baumannii Among Pet Dogs and Cats with Respiratory Illness Outside the Healthcare Facilities: A Possible Public Health Concern

Background: Researchers paid more attention to nosocomial Acinetobacter baumannii in veterinary hospitals worldwide; however, the research scope toward community-acquired A. baumannii infections among animals is largely ignored. Therefore, the current study aimed to investigate the role of diseased dogs and cats suffering from respiratory illness in transmission of community-acquired A. baumannii infection and its public health threat. Materials and methods: Oral swabs were collected from 154 pet animals with respiratory signs, including 80 cats and 74 dogs (outpatient visits). The obtained swabs were cultured on CHROMagar™ MH Orientation media for isolation of A. baumannii, and identification of suspected isolates was conducted via Gram staining, conventional biochemical tests, and molecular detection of the blaOXA-51-like gene. Antimicrobial susceptibility testing of A. baumannii isolates was carried out using the disc diffusion method. Results: Overall, 10 (6.5%) out of 154 diseased pet animals were positive for A. baumannii, where 6 (8.1%) and 4 (5%) dogs and cats were positive, respectively. Multidrug-resistant (MDR) A. baumannii was found in 3.9% of the examined animals. The phylogenetic tree analysis revealed that the obtained sequences from dogs and cats were closely related to human and animal sequences. Conclusion: The occurrence of MDR A. baumannii among dogs and cats suffering from respiratory illness highlights the potential role of pet animals in the dissemination of MDR A. baumannii in the community.

Emergence of extensively-drug-resistant hypervirulent Acinetobacter baumannii isolated from patients with bacteraemia: bacterial phenotype and virulence analysis

OBJECTIVES

Individuals infected with extensively-drug-resistant (XDR) Acinetobacter baumannii are difficult to cure and have a high mortality rate. This study compared the genomic and phenotypic differences between XDR and non-multi-drug-resistant (MDR) A. baumannii, and further characterized hypervirulent XDR A. baumannii.

METHODS

In total, 1403 acinetobacter isolates were collected from patients with bacteraemia between 1997 and 2015. Antimicrobial susceptibility tests were performed to categorize isolates into non-MDR, MDR and XDR groups. The presence of selected virulence-associated genes was determined by polymerase chain reaction. Bacterial phenotypes, including iron acquisition, biofilm formation, capsule production, and virulence to larvae and mice, were determined.

RESULTS

Multi-locus sequence typing revealed a high prevalence of sequence type (ST) 2 (81.6%) and ST129 (18.4%) among 49 XDR isolates, and the STs of 18 non-MDR isolates were more diverse. Virulence-associated phenotypic assays showed that XDR isolates had higher iron acquisition ability, greater capsule production, and virulence to Galleria mellonella larvae. However, their ability to form biofilm was lower compared with that of non-MDR isolates. XDR isolates were more likely to have virulence genes (tonB, hemO, abaI and ptk), while non-MDR isolates were more likely to have pld and ompA genes. Twenty-one XDR isolates that had a <20% larvae survival rate after 7 days post-infection were defined as hypervirulent XDR isolates. Among them, isolates 1677 (ST129) and 929-1 (ST2) caused the death of all infected mice within 2 days.

CONCLUSION

Some subpopulations of highly-drug-resistant ST2 isolates exhibit high virulence. As such, it is of utmost importance to continue monitoring the spread of hypervirulent XDR A. baumannii isolates.

Risk factors for multidrug-resistant and extensively drug-resistant Acinetobacter baumannii infection of patients admitted in intensive care unit: a systematic review and meta-analysis

BACKGROUND

Multidrug-resistant (MDR) and extensively drug-resistant (XDR) Acinetobacter baumannii infections pose challenges for clinical treatment and cause high mortality, particularly in intensive care units (ICUs).

AIM

To systematically summarize and analyse the risk factors for MDR/XDR A. baumannii-infected patients admitted to ICUs.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were searched for eligible original studies published in English before October 2023. Meta-analysis was conducted where appropriate, with mean differences (MDs) and odds ratios (ORs) calculated for continuous and nominal scaled data. The quality of included studies was assessed using the Newcastle-Ottawa Scale (NOS).

FINDINGS

Ten studies reporting 1199 ICU patients (604 from general ICUs, 435 from neonatal ICUs, and 160 from paediatric ICUs) from eight countries were included in our analysis. Risk factors associated with MDR A. baumannii infection among patients admitted to general ICUs included high Acute Physiology And Clinical Health II (APACHE Ⅱ) score (mean difference (MD): 7.52; 95% confidence interval (CI): 3.24-11.80; P = 0.0006), invasive procedures (odds ratio (OR): 3.47; 95% CI: 1.70-7.10; P = 0.0006), longer ICU stay (MD: 3.40; 95% CI: 2.94-3.86; P < 0.00001), and use of antibiotics (OR: 2.69; 95% CI: 1.22-5.94; P = 0.01). In the sub-group analysis, longer neonatal ICU stay (MD: 16.88; 95% CI: 9.79-23.97; P < 0.00001) was associated with XDR A. baumannii infection.

CONCLUSION

Close attention should be paid to patients with longer ICU stays, undergoing invasive procedures, using antibiotics, and with high APACHE Ⅱ scores to reduce the risk of MDR and XDR A. baumannii infections.

Risk factors for bacteremia and mortality due to multidrug-resistant Acinetobacter baumannii: a retrospective study

This research aimed to determine the relationships between the risk factors for nosocomial multidrug-resistant Acinetobacter baumannii (MDRAB) bacteremia and associated mortality. We analyzed 144 patients treated for A. baumannii bacteremia, including 120 patients with MDRAB bacteremia, from March 2015 to March 2020, in this retrospective study. The overall bacteremia-related mortality rate was 48.6%. The mortality rates were 25.0% and 53.3% for non-MDRAB and MDRAB bacteremia, respectively. Risk factors for the development of MDRAB bacteremia were prior use of cephalosporins [odds ratio (OR): 8.62; P < .001], carbapenems (OR: 15.04; P < .001), or quinolones (OR: 5.02; P = .040); indwelling urinary catheters (OR: 21.38; P < .001); and respiratory tract as the source of bacteremia (OR: 75.33; P < .001). Patients with elective surgeries were inclined to develop non-MDRAB bacteremia (OR: 0.45; P = .029). High scores in the Acute Physiology and Chronic Health Evaluation II (OR: 1.321; P < .001) and Sequential Organ Failure Assessment (OR: 1.326; P < .001) were risk factors for mortality from MDRAB infection. In summary, higher mortality rates occur in patients with MDRAB bacteremia, and risk factors include prior use of cephalosporins, carbapenems, or quinolones. Urinary catheters and the respiratory tract as sources of the infection increase the risk of MDRAB bacteremia.

Risk factors for progression to bacteremia among patients with nosocomial carbapenem-resistant Acinetobacter baumannii pneumonia in the Intensive Care Unit

Antibiotic-resistant Acinetobacter baumannii (A. baumannii) is a common cause of hospital-acquired infections. This study aimed to identify independent factors associated with progression from nosocomial pneumonia to bacteremia in patients infected with carbapenem-resistant A. baumannii (CR-AB). From 2019 to 2021, we conducted a retrospective anaylsis of the medical records of 159 nosocomial CR-AB pneumonia patients in our Intensive Care Unit (ICU). We employed both univariate and multivariable logistic regression models to identify factors associated with the progression of nosocomial CR-AB pneumonia to bacteremia. Among the 159 patients with nosocomial CR-AB pneumonia, 40 experienced progression to bacteremia and 38 died within 28 days following diagnosis. Patients who developed bacteremia had a significantly higher 28-day mortality rate compared to those without bloodstream infection (47.50% vs. 15.97%). Multivariable logistic regression revealed that higher levels of C-Reactive protein (CRP) (OR = 1.01) and the use of continuous veno-venous hemofiltration (CVVH) treatment (OR = 2.93) were independently associated with an elevated risk of developing bacteremia. Among patients who developed bloodstream infection, those who died within 28 days exhibited significantly higher level of interleukin-6 (IL-6), a greater frequency of antifungal drugs usage, and a longer duration of machanical ventilation compared to survivors. Furthermore, the use of antifungal drugs was the only factor that associated with 28-day mortality (OR = 4.70). In ICU patients with central venous catheters who have CR-AB pneumonia and are on mechanical ventilation, higher CRP levels and CVVH treatment are risk factors for developing bacteremia. Among patients with bacteremia, the use of antifungal drugs is associated with 28-day mortality.

Excess mortality and long-term disability from healthcare-associated carbapenem-resistant Acinetobacter baumannii infections: A nationwide population-based matched cohort study

BACKGROUND

Carbapenem resistance is perceived as a clinical challenge in the management of debilitated and immunocompromised patients who eventually will die from underlying diseases. We aimed to examine whether carbapenem resistance per se, rather than the underlying diseases, negatively affect outcomes, by comparing the excess mortality and morbidity from healthcare-associated infections (HAIs) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-susceptible A. baumannii (CSAB).

METHODS

This was a nationwide retrospective matched cohort study of hospitalized patients in 96 hospitals which participated in Taiwan Nosocomial Infection Surveillance (TNIS). A total of 2,213 patients with A. baumannii HAIs were individually matched to 4,426 patients without HAIs. Main outcomes were excess risks for one-year all-cause mortality and one-year new-onset chronic ventilator dependence or dialysis-dependent end-stage renal disease.

RESULTS

Excess one-year mortality was 27.2% in CRAB patients, compared with their matched uninfected inpatients, as well as 15.4% in CSAB patients (also compared with their matched uninfected inpatients), resulting in an attributable mortality of 11.8% (P <0.001) associated with carbapenem resistance. The excess risk associated with carbapenem resistance for new-onset chronic ventilator dependence was 5.2% (P <0.001). Carbapenem resistance was also associated with an extra cost of $2,511 per case of A. baumannii HAIs (P <0.001).

CONCLUSION

Carbapenem resistance is associated with a significant disease burden in terms of excess mortality, long-term ventilator dependence, and medical cost. Further studies on effects of antimicrobial stewardship programs in decreasing this burden are warranted.

The Isolation of Anaerobic and Facultative Anaerobic Sulfate-Reducing Bacteria (SRB) and a Comparison of Related Enzymes in Their Sulfate Reduction Pathways

Sulfate-reducing bacteria (SRB) are an important group of microorganisms that cause microbial corrosion. In this study, culturable SRB were isolated and identified from the inner rust layer of three kinds of steel and from sediments, and a comparison of amino acid sequences encoding related enzymes in the sulfate reduction pathway between anaerobic and facultative anaerobic SRB strains was carried out. The main results are as follows. (1) Seventy-seven strains were isolated, belonging to five genera and seven species, with the majority being Desulfovibrio marinisediminis. For the first time, Holodesulfovibrio spirochaetisodalis and Acinetobacter bereziniae were separated from the inner rust layer of metal, and sulfate reduction by A. bereziniae, Virgibacillus dokdonensis, and Virgibacillus chiguensis, etc., was also demonstrated for the first time. (2) Three strains of strictly anaerobic bacteria and four strains of facultative anaerobic bacteria were screened from seven bacterial strains. (3) Most of the anaerobic SRB only contained enzymes for the dissimilatory sulfate reduction pathway, while those of facultative anaerobic bacteria capable of producing hydrogen sulfide included two possible ways: containing the related enzymes from the dissimilatory pathway only, or containing enzymes from both dissimilatory and assimilation pathways. This study newly discovered that some bacterial genera exhibit sulfate reduction ability and found that there are differences in the distribution of enzymes related to the sulfate reduction pathway between anaerobic and facultative anaerobic SRB type trains, providing a basis for the development and utilization of sulfate-reducing bacterial resources and furthering our understanding of the metabolic mechanisms of SRB.

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.

Clinical and economic burden of bacteremia due to multidrug-resistant organisms in Korea: a prospective case control study

OBJECTIVES

The socioeconomic and clinical burden of multidrug-resistant organisms (MDRO), including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), multidrug-resistant Acinetobacter baumannii (MRAB), multidrug-resistant Pseudomonas aeruginosa (MRPA), and carbapenem-resistant Enterobacteriaceae (CRE) have not yet been adequately addressed.

METHODS

We prospectively searched for MDRO bacteremia cases with matched controls from 10 hospitals across Korea during a 6-month period in 2017. Patients were classified into the MDRO, susceptible organism, and no-infection groups. The corresponding susceptible or no-infection controls had been selected according to predefined criteria. We collected clinical information and estimated the total additional medical cost due to MDRO infections using the multistate model.

RESULTS

During the 6-month period, a total of 486 MDRO bacteremia cases (260, 87, 18, 20, and 101 cases of MRSA, MRAB, MRPA, CRE, and VRE, respectively) were identified. The 90-d mortality rates were 30.4%, 63.2%, 16.7%, 55.0%, and 47.5%, respectively. The additional costs caused by bacteremia were $15 768, $35 682, $39 908, $72 051, and $33 662 per MDRO type, respectively. Based on these 6-month data, the estimated annual number of bacteremia cases due to these five MDRO in Korea were 7979 (4070, 1396, 218, 461, and 1834 cases, respectively). Overall, this caused an estimated 3280 (1237, 882, 36, 254, and 871, respectively) deaths and cost $294 505 002 ($84 707 359, $74 387 364, $10 344 370, $45 850 215, and $79 215 694, respectively) (range $170,627,020-$416,094,679) in socioeconomic loss.

CONCLUSIONS

A tremendous clinical and economic burden is caused by MDRO bacteremia compared with antibiotic-susceptible and no-infection groups. Substantial investment and efforts by related government agencies and medical staffs are needed.

Efficacy of Eravacycline Versus Best Previously Available Therapy for Adults With Pneumonia Due to Difficult-to-Treat Resistant (DTR) Acinetobacter baumannii

BACKGROUND

Multidrug-resistant Acinetobacter baumannii remains challenging to treat. Although eravacycline has in vitro activity against this pathogen, there are no studies evaluating outcomes.

OBJECTIVE

To assess the efficacy of eravacycline compared with best previously available therapy in adults with difficult-to-treat resistant (DTR) A. baumannii pneumonia.

METHODS

This was a retrospective study of adults hospitalized for pneumonia with DTR A. baumannii. Patients receiving eravacycline were compared with those receiving best previously available therapy. The primary outcome was 30-day in-hospital mortality. Secondary outcomes included clinical cure at Day 14, hospital and intensive care unit (ICU) length of stay, microbiologic cure, and readmission within 90 days with a positive A. baumannii respiratory culture.

RESULTS

Ninety-three patients were included, with 27 receiving eravacycline. Eravacycline was associated with higher 30-day mortality (33% vs 15%; P = 0.048), lower microbiologic cure (17% vs 59%; P = 0.004), and longer durations of mechanical ventilation (10.5 vs 6.5 days; P = 0.016). At baseline, eravacycline patients had more A. baumannii bacteremia and coinfection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Among bacteremic patients, all 4 receiving eravacycline died by Day 30 and both patients receiving best previously available therapy survived. Upon exclusion of patients with bacteremia and SARS-CoV-2, there were no differences between the groups across any outcomes.

CONCLUSIONS

Eravacycline-based combination therapy had similar outcomes to best previously available combination therapy for adults with DTR A. baumannii pneumonia. However, eravacycline should be used with caution in the setting of bacteremia as outcomes were poor in this population.

Risk Factors for and Clinical Outcomes of Polymicrobial Acinetobacter baumannii Bloodstream Infections

Background

Although the clinical features of Acinetobacter baumannii bloodstream infection are well described, the specific clinical characteristics of polymicrobial Acinetobacter baumannii bloodstream infection have been rarely reported. The objective of this study was to examine the risk factors for and clinical outcomes of polymicrobial Acinetobacter baumannii bloodstream infection.

Methods

A retrospective observational study was performed from January 2013 to December 2018 in a tertiary hospital. All patients with Acinetobacter baumannii bloodstream infection were enrolled, and the data were collected from the electronic medical records.

Results

A total of 594 patients were included, 21% (126/594) of whom had polymicrobial infection. The most common copathogen was Klebsiella pneumoniae (20.81%), followed by Pseudomonas aeruginosa (16.78%) and Enterococcus faecium (12.08%). Compared with monomicrobial Acinetobacter baumannii bloodstream infection, polymicrobial Acinetobacter baumannii bloodstream infection mostly originated from the skin and soft tissue (28.6% vs. 10.5%, p < 0.001). Multivariate analysis revealed that burn injury was independently associated with polymicrobial Acinetobacter baumannii bloodstream infection (adjusted odds ratio, 3.569; 95% confidence interval, 1.954-6.516). Patients with polymicrobial Acinetobacter baumannii bloodstream infection were more likely to have a longer hospital length of stay [40 (21, 68) vs. 27 (16, 45), p < 0.001] and more hospitalization days after bloodstream infection than those with monomicrobial Acinetobacter baumannii bloodstream infection [22 (8, 50) vs. 13 (4, 28), p < 0.001]. However, no significant difference in mortality was observed between the two groups.

Conclusions

Approximately one-fifth of Acinetobacter baumannii bloodstream infections were polymicrobial in this cohort. The main sources were skin and soft tissue infections, and burn injury was the only independent risk factor. Although mortality did not differ between the groups, considering the limitations of the study, further studies are required to assess the impact of polymicrobial (vs. monomicrobial) Acinetobacter baumannii bloodstream infection on outcomes.

Inhibition of the clinical isolates of Acinetobacter baumannii by Pseudomonas aeruginosa: In vitro assessment of a case-based study

BACKGROUND

The global rise in nosocomial infections associated with gram-negative bacteria and the spread of multi-drug resistant Acinetobacter baumannii (MDR-AB) pose public health concerns. This study investigates the inhibitory effects and possible inhibitory mechanism of Pseudomonas aeruginosa (PA) on selected clinical strains of A. baumannii (AB) isolated from Taiwanese patients.

METHODS

Four and eight clinical strains of AB and PA, respectively, were randomly selected from the bacterial collection of Feng-Yuan Hospital, Taiwan. Antimicrobial-susceptibility was performed on the AB strains. Inhibition potential of the PA strains against AB was assessed by measuring the inhibition zones. In vitro analysis using phenazine-1-carboxamide (PCN) was conducted to assess the possible inhibitory mechanism of PA, which was later confirmed in the clinical isolates by liquid chromatography-mass spectrometry.

RESULTS

All the clinical AB strains showed resistance to the eleven antibiotics and were classified as MDR-AB. The nine PA strains exert either a high (PA3596, PA3681, PA3772, and ATCC27853) or a low (PA3613, PA3625, PA3712, PA3715, and PA3744) degree of inhibition against AB strains. 0.25 mg/ml PCN had a clearer inhibition zone than 0.05 mg/ml PCN, suggesting a dose-dependent inhibition of PCN on the AB strains. The four PA strains that demonstrated a high degree of inhibition had a relatively high amount of PCN.

CONCLUSION

Selected strains of PA exert inhibitory actions on MDR-AB with PCN being a possible inhibitory agent. This finding raises the possibility of developing effective therapeutic antibiotics and disinfectant from specific components of PA for the treatment and control of Acinetobacter-associated infections in hospital settings.

Surgical Site Infections and Antimicrobial Resistance After Cesarean Section Delivery in Rural Rwanda

Background:

As the volume of surgical cases in low- and middle-income countries (LMICs) increases, surgical-site infections (SSIs) are becoming more prevalent with anecdotal evidence of antimicrobial resistance (AMR), despite a paucity of data on resistance patterns.

Objectives:

As a primary objective, this prospective study aimed to describe the epidemiology of SSIs and the associated AMR among women who delivered by cesarean at a rural Rwandan hospital. As secondary objectives, this study also assessed patient demographics, pre- and post-operative antibiotic use, and SSI treatment.

Methods:

Women who underwent cesarean deliveries at Kirehe District Hospital between September 23rd, 2019, and March 16th, 2020, were enrolled prospectively. On postoperative day (POD) 11 (+/– 3 days), their wounds were examined. When an SSI was diagnosed, a wound swab was collected and sent to the Rwandan National Reference Laboratory for culturing and antibiotic susceptibility testing.

Findings:

Nine hundred thirty women were enrolled, of whom 795 (85.5%) returned for the POD 11 clinic visit. 45 (5.7%) of the 795 were diagnosed with SSI and swabs were collected from 44 of these 45 women. From these 44 swabs, 57 potential pathogens were isolated. The most prevalent bacteria were coagulase-negative staphylococci (n = 12/57, 20.3% of all isolates), and Acinetobacter baumannii complex (n = 9/57, 15.2%). 68.4% (n = 39) of isolates were gram negative; 86.7% if excluding coagulase-negative staphylococci. No gram-negative pathogens isolated were susceptible to ampicillin, and the vast majority demonstrated intermediate susceptibility or resistance to ceftriaxone (92.1%) and cefepime (84.6%).

Conclusions:

Bacterial isolates from SSI swab cultures in rural Rwanda predominantly consisted of gram-negative pathogens and were largely resistant to commonly used antibiotics. This raises concerns about the effectiveness of antibiotics currently used for surgical prophylaxis and treatment and may guide the appropriate selection of treatment of SSIs in rural Rwanda and comparable settings.

Ten-Year Changes in Bloodstream Infection With Acinetobacter Baumannii Complex in Intensive Care Units in Eastern China: A Retrospective Cohort Study

Background: There is little evidence on the changing prevalence, microbiological profile, and outcome of nosocomial Acinetobacter baumannii complex (ABC)-caused bloodstream infection (ABCBSI) specified in intensive care units (ICUs) in long-term studies, especially in China. Objective: We aimed to investigate changes in incidence, antibiotic resistance, therapy, and prognosis of ABCBSI in ICUs in eastern China during 2009-2018. Methods: A multicenter retrospective cohort study was conducted, and microbiological and clinical data for patients with ABCBSI acquired in nine adult ICUs in eastern China from 2009 to 2018. Results: A total of 202 cases were enrolled. For the years 2009-2010, 2011-2012, 2013-2014, 2015-2016, and 2017-2018, the incidence of ABCBSI increased significantly, as did the percentage of pan-drug-resistant isolates and resistant rates to most of antimicrobial agents; the percentage of drug-sensitive isolates decreased (all P < 0.05). The frequency of treatment with carbapenems and tigecycline increased, and that of cephalosporins decreased. Compared with those in the first years (2009-2012), ABCBSI patients in the lattermost years (2017-2018) were less often treated with appropriate empirical therapy, more often underwent pneumonia-related ABCBSI and mechanical ventilation support, and had higher 28-day mortality rates. Multivariate Cox regression indicated that increase in the degree of ABC antibiotics resistance, pneumonia-related ABCBSI, and septic shock were risk factors of 28-day mortality and associated with significant lower survival days. Conclusions: The past decade has witnessed a marked increase in the incidence of ABCBSI and in antibiotic resistance, with increasing pneumonia-related infections and worrisome mortality in ICUs in China. Controlling increasing resistance and preventing nosocomial pneumonia may play important roles in combatting these infections.

Systematic review and meta-analysis of the proportion and associated mortality of polymicrobial (vs monomicrobial) pulmonary and bloodstream infections by Acinetobacter baumannii complex

BACKGROUND

Differentiating Acinetobacter baumannii complex (ABC) infection from colonization remains difficult and further complicated in polymicrobial infections.

PURPOSE

To assess the frequency of polymicrobial ABC infections and associated mortality. We hypothesized a lower mortality in polymicrobial infections if ABC isolation reflects colonization in some polymicrobial infections.

METHODS

A systematic review was conducted in PubMed, Scopus and CENTRAL for studies reporting ABC pulmonary and bloodstream infections. The proportion of infections that were polymicrobial and the magnitude of the association between polymicrobial (vs monomicrobial) infection and mortality were estimated with meta-analyses.

RESULTS

Based on 80 studies (9759 infections) from 23 countries, the pooled proportion of polymicrobial infection was 27% (95% CI 22-31%) and was similarly high for bloodstream and pulmonary infections. Polymicrobial infection was variably and insufficiently defined in most (95%) studies. Considerable heterogeneity (I² = 95%) was observed that persisted in subgroup analyses and meta-regressions. Based on 17 studies (2675 infections), polymicrobial infection was associated with lower 28-day mortality (OR = 0.75, 95% CI 0.58-0.98, I² = 36%). However, polymicrobial infection was not associated with in-hospital mortality (OR = 0.97, 95% CI 0.69-1.35, I² = 0%) based on 14 studies (953 infections). The quality of evidence (GRADE) for the association of polymicrobial (vs monomicrobial) infection with mortality was low and at high risk of bias.

CONCLUSION

Polymicrobial ABC infections are common and may be associated with lower 28-day mortality. Considering the heterogeneity of polymicrobial infections and limitations of the available literature, more research is required to clarify the clinical impact of polymicrobial (vs monomicrobial) ABC infection.

Metformin as a Potential Adjuvant Antimicrobial Agent Against Multidrug Resistant Bacteria

Introduction

The continuous increase in the incidence of bacterial resistance to existing antibiotics represents a worldwide health burden. A surrogate strategy to combat such crisis is to find compounds that restore the antimicrobial activity of the already existing antibiotics against multidrug resistant bacteria. Metformin is a commonly used antidiabetic medication. It has proven benefits in other diseases including cancer, aging-related and infectious diseases. In this study, the potential effect of metformin as an adjuvant therapy to antibiotics was investigated.

Methods

Two multidrug resistant bacterial strains were used; methicillin-resistant Staphylococcus aureus (MRSA; ATCC 33,591) and multidrug resistant Pseudomonas aeruginosa (ATCC BAA-2114). To assess its efficacy, metformin was combined with several antibiotics: levofloxacin, chloramphenicol, rifampicin, ampicillin, and doxycycline. The antibacterial effect of metformin was tested using the micro broth dilution method. The minimum inhibitory concentration (MIC) was also measured. Cytotoxicity studies were also performed on mammalian cells to assess its safety.

Results

Metformin exhibited an antibacterial effect when combined with the antibiotics on the two tested strains. It also showed low toxicity on the mammalian cells. Moreover, synergetic studies showed that metformin enhanced the effect of the combined antibiotics, as these combinations provide either a synergistic or additive effect with significant reduction in the MIC.

Conclusion

Metformin exerts an adjuvant antibacterial effect; thus, it could be a possible candidate as an adjuvant therapy to reduce antimicrobial resistance.

Comparison of Carbapenem-Resistant Microbial Pathogens in Combat and Non-combat Wounds of Military and Civilian Patients Seen at a Tertiary Military Hospital, Philippines (2013-2017)

INTRODUCTION

Bacterial wound infections are a danger to both military and civilian populations. The nature of injury and infection associated with combat related wounds are important in guiding antibiotic prophylaxis and empiric treatment guidelines.

MATERIALS AND METHODS

The isolates were screened for drug-resistance by the MicroScan Walkaway Plus System using either the Negative Breakpoint Combo Panel (NBCP) 30 or 34 or Positive Breakpoint Combo Panel (PBPC) 20 or 23. Isolates with a minimum inhibitory concentration (MIC) of ≥8 μg/mL to imipenem and/or meropenem were tested for both carbapenemase production using the CarbaNP test and real-time PCR to determine molecular resistance mechanisms. Plasmid conjugation analysis was performed to define potential for horizontal gene transfer.

RESULTS

We characterized 634 bacterial wound isolates collected from September 2013 to December 2017 from patients seen at a Philippine military tertiary hospital presenting with combat or non-combat injuries [354 (military) and 280 (civilians)]. Staphylococcus aureus was the most predominant bacterial species isolated from wounds in both populations (104/634, 16%). A variety of Gram-negative bacterial species comprised 442/634 (70%) of the isolates identified, with the most prevalent shown to be Pseudomonas aeruginosa, Enterobacter cloacae, Klebsiella pneumoniae, Escherichia coli, and Acinetobacter sp. Carbapenemase production was detected in 34/442 (8%) Gram-negative isolates. Testing for molecular resistance mechanisms showed 32/34 (17 military, 15 civilian) wound isolates were blaNDM positive and 2 were blaVIM positive, with the two blaVIM isolates found in the civilian population. Plasmid conjugation of 14 blaNDM and 2 blaVIM positive wound isolates representatives showed 2/16 (13%) produced E. coli J53 transconjugants (E. coli from a civilian; E. cloacae from a military).

CONCLUSION

We describe in this study the wound bacterial and antibiotic resistance profile in the military (combat vs non-combat associated) and civilian population. We observed that, with the exception of Acinetobacter sp., resistance of prevalent Gram-negative bacterial species to imipenem or meropenem were not significantly different between the military and civilian populations. We also presented data on the prevalent bacterial species isolated from both combat and non-combat wounds in a military tertiary care hospital setting as well as the carbapenemase-encoding gene primarily responsible for carbapenem resistance as well as evidence of horizontal transfer via mobile genetic elements. Clinicians may use this information to guide empiric antibiotic coverage for the predominant organisms if wound culture results are not readily available.A prospective, longitudinal evaluation of the wound bacterial profile documenting the changing bacterial flora using higher resolution molecular strategies can provide a more comprehensive understanding of the diversity, composition, and abundance of bacterial composition of the wound microbial community from the time of injury, during the course of evacuation from the field to higher level of care facilities, and up to wound resolution.

Metagenomic insights into the antibiotic resistome of mangrove sediments and their association to socioeconomic status

Mangrove sediments are prone to anthropogenic activities that could enrich antibiotics resistance genes (ARGs). The emergence and dissemination of ARGs are of serious concern to public health worldwide. Therefore, a comprehensive resistome analysis of global mangrove sediment is of paramount importance. In this study, we have implemented a deep machine learning approach to analyze the resistome of mangrove sediments from Brazil, China, Saudi Arabia, India, and Malaysia. Geography (R_ANOSIM = 39.26%; p < 0.005) as well as human intervention (R_ANOSIM = 16.92%; p < 0.005) influenced the ARG diversity. ARG diversity was also inversely correlated to the human development index (HDI) of the host country (R = -0.53; p < 0.05) rather than antibiotics consumption (p > 0.05). Several genes including multidrug efflux pumps were significantly (p < 0.05) enriched in the sites with human intervention. Resistome was consistently dominated by rpoB2 (19.26 ± 0.01%), multidrug ABC transporter (10.40 ± 0.23%), macB (8.84 ± 0.36n%), tetA (4.13 ± 0.35%), mexF (3.26 ± 0.19%), CpxR (2.93 ± 0.2%), bcrA (2.38 ± 0.24%), acrB (2.37 ± 0.18%), mexW (2.19 ± 0.17%), and vanR (1.99 ± 0.11%). Besides, mobile ARGs such as vanA, tet(48), mcr, and tetX were also detected in the mangrove sediments. Comparative analysis against terrestrial and ocean resistomes showed that the ocean ecosystem harbored the lowest ARG diversity (Chao1 = 71.12) followed by mangroves (Chao1 = 258.07) and terrestrial ecosystem (Chao1 = 294.07). ARG subtypes such as abeS and qacG were detected exclusively in ocean datasets. Likewise, rpoB2, multidrug ABC transporter, and macB, detected in mangrove and terrestrial datasets, were not detected in the ocean datasets. This study shows that the socioeconomic factors strongly determine the antibiotic resistome in the mangrove. Direct anthropogenic intervention in the mangrove environment also enriches antibiotic resistome.

Low-temperature laminar flow ward for the treatment of multidrug resistance Acinetobacter baumannii pneumonia

This study was designed to investigate the effect of low-temperature laminar flow ward (LTLFW) on the Acinetobacter baumannii pneumonia (MDR-ABP) in neurosurgical intensive care unit (NICU) patients. We evaluated whether patients in a LTLFW had significantly improved clinical outcomes as compared to those in nonconstant-temperature NICU (room temperature). The association of temperature with the prevalence of ABP and A. baumannii isolates (ABI) found in NICU patients was specifically investigated. In vitro microbiological experiments were conducted to measure the proliferation, antibiotic sensitivity, and genomic profiles of A. baumannii (AB) that grew in variable temperatures. MDR-ABP patients in LTLFW had significantly improved outcomes than those in the room temperature NICU. In addition, the numbers of ABI were positively associated with mean ambient outdoor temperatures (P = 0.002), with the incidence of ABP and average numbers of ABI among NICU patients being substantially lower in the winter as compared to other seasons. However, there were no significant seasonal variations in the other strains of the top five bacteria. Consistent with these clinical observations, AB growing at 20°C and 25°C had significantly reduced viability and antibiotic resistance compared to those growing at 35°C. The expression of genes related to AB survival ability, drug resistance, and virulence also differed between AB growing at 20°C and those at 35°C. LTLFW is effective in promoting the recovery of MDR-ABP patients because low temperatures reduced the density and virulence of AB and enhanced the efficacy of antibiotics, likely at the genetic level.

Prevalence and Outcomes of Infection Among Patients in Intensive Care Units in 2017

IMPORTANCE

Infection is frequent among patients in the intensive care unit (ICU). Contemporary information about the types of infections, causative pathogens, and outcomes can aid the development of policies for prevention, diagnosis, treatment, and resource allocation and may assist in the design of interventional studies.

OBJECTIVE

To provide information about the prevalence and outcomes of infection and the available resources in ICUs worldwide.

DESIGN, SETTING, AND PARTICIPANTS

Observational 24-hour point prevalence study with longitudinal follow-up at 1150 centers in 88 countries. All adult patients (aged ≥18 years) treated at a participating ICU during a 24-hour period commencing at 08:00 on September 13, 2017, were included. The final follow-up date was November 13, 2017.

EXPOSURES

Infection diagnosis and receipt of antibiotics.

MAIN OUTCOMES AND MEASURES

Prevalence of infection and antibiotic exposure (cross-sectional design) and all-cause in-hospital mortality (longitudinal design).

RESULTS

Among 15 202 included patients (mean age, 61.1 years [SD, 17.3 years]; 9181 were men [60.4%]), infection data were available for 15 165 (99.8%); 8135 (54%) had suspected or proven infection, including 1760 (22%) with ICU-acquired infection. A total of 10 640 patients (70%) received at least 1 antibiotic. The proportion of patients with suspected or proven infection ranged from 43% (141/328) in Australasia to 60% (1892/3150) in Asia and the Middle East. Among the 8135 patients with suspected or proven infection, 5259 (65%) had at least 1 positive microbiological culture; gram-negative microorganisms were identified in 67% of these patients (n = 3540), gram-positive microorganisms in 37% (n = 1946), and fungal microorganisms in 16% (n = 864). The in-hospital mortality rate was 30% (2404/7936) in patients with suspected or proven infection. In a multilevel analysis, ICU-acquired infection was independently associated with higher risk of mortality compared with community-acquired infection (odds ratio [OR], 1.32 [95% CI, 1.10-1.60]; P = .003). Among antibiotic-resistant microorganisms, infection with vancomycin-resistant Enterococcus (OR, 2.41 [95% CI, 1.43-4.06]; P = .001), Klebsiella resistant to β-lactam antibiotics, including third-generation cephalosporins and carbapenems (OR, 1.29 [95% CI, 1.02-1.63]; P = .03), or carbapenem-resistant Acinetobacter species (OR, 1.40 [95% CI, 1.08-1.81]; P = .01) was independently associated with a higher risk of death vs infection with another microorganism.

CONCLUSIONS AND RELEVANCE

In a worldwide sample of patients admitted to ICUs in September 2017, the prevalence of suspected or proven infection was high, with a substantial risk of in-hospital mortality.

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

BACKGROUND

Several observational studies suggest that gloves of health care workers are major routes of multidrug-resistant Acinetobacter baumannii transmission. However, limited experimental data are available assessing Acinetobacter transmission from gloves to environmental surfaces. This study determined whether A baumannii was easily transferred from nitrile gloves to polypropylene plastic compared with other gram-negative bacteria that cause health care-associated infections in laboratory-controlled experiments.

METHODS

Gloved fingerpad-to-fomite transfer efficiency was determined for drug-resistant and -sensitive strains of A baumannii, Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa.

RESULTS

Only A baumannii transferred from gloves to fomites 3 minutes after the bacterial transfer event. Transfer efficiency of A baumannii was 0.1%-33% at that time point.

DISCUSSION

Bacterial transfer from contaminated gloves to the hospital environment may be related to the type of contaminating bacteria, inoculated bacterial level, fomites, and glove materials. Therefore, it is important to need a comprehensive assessment of the transfer efficiency.

CONCLUSIONS

A baumannii can transfer easily from nitrile gloves to fomite compared with other gram-negative bacteria that cause health care-associated infections. These findings support data from previous observational studies that gloves of health care workers can be major routes of A baumannii transmission in clinical settings.

Economic burden of antibiotic resistance in ESKAPE organisms: a systematic review

Background

Antibiotic resistance (ABR) is one of the biggest threats to global health. Infections by ESKAPE (Enterococcus, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, and E. coli) organisms are the leading cause of healthcare-acquired infections worldwide. ABR in ESKAPE organisms is usually associated with significant higher morbidity, mortality, as well as economic burden. Directing attention towards the ESKAPE organisms can help us to better combat the wide challenge of ABR, especially multi-drug resistance (MDR).

Objective

This study aims to systematically review and evaluate the evidence of the economic consequences of ABR or MDR ESKAPE organisms compared with susceptible cases or control patients without infection/colonization in order to determine the impact of ABR on economic burden.

Methods

Both English-language databases and Chinese-language databases up to 16 January, 2019 were searched to identify relevant studies assessing the economic burden of ABR. Studies reported hospital costs (charges) or antibiotic cost during the entire hospitalization and during the period before/after culture among patients with ABR or MDR ESKAPE organisms were included. The costs were converted into 2015 United States Dollars. Disagreements were resolved by a third reviewer.

Results

Of 13,693 studies identified, 83 eligible studies were included in our review. The most studied organism was S. aureus, followed by Enterococcus, A. baumannii, E. coli, E. coli or/and K. pneumoniae, P. aeruginosa, and K. pneumoniae. There were 71 studies on total hospital cost or charge, 12 on antibiotic cost, 11 on hospital cost or charge after culture, 4 on ICU cost, 2 on hospital cost or charge before culture, and 2 on total direct and indirect cost. In general, ABR or MDR ESKAPE organisms are significantly associated with higher economic burden than those with susceptible organisms or those without infection or colonization. Nonetheless, there were no differences in a few studies between the two groups on total hospital cost or charge (16 studies), antibiotic cost (one study), hospital cost before culture (one study), hospital cost after culture (one study). Even, one reported that costs associated with MSSA infection were higher than the costs for similar MRSA cases.

Conclusions

ABR in ESKAPE organisms is not always, but usually, associated with significantly higher economic burden. The results without significant differences may lack statistical power to detect a significant association. In addition, study design which controls for severity of illness and same empirical antibiotic therapy in the two groups would be expected to bias the study towards a similar, even negative result. The review also highlights key areas where further research is needed.

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii isolates reveals the emergence of blaOXA-23 and blaNDM-1 encoding international clones in India

Acinetobacter baumannii is a nosocomial pathogen increasingly affecting the critically ill patients and represents a major public health challenge. Carbapenem-resistant A. baumannii (CRAB) is found to be associated with International Clones (ICs) and different classes of carbapenemases. The objective of the present study was to investigate the prevalence of carbapenem resistance genes, clonal relationship and genetic structure of clinical isolates of A. baumannii. In the present study, multi-locus sequence typing (MLST^OX) and analysis were carried out using Oxford scheme for 86 clinical isolates of CRAB along with 11 carbapenem sensitive A. baumannii (CSAB) collected over a period of two years (2014-2016) from two tertiary care hospitals of North India. We observed a high prevalence of the bla_OXA-23-like (97.7%) among the CRAB followed by bla_NDM-1 (29.1%) and bla_OXA58-like (3.5%). Forty-seven Sequence Types (STs) were represented by all 97 isolates, out of which, 28 (59.6%) were novel STs that were assigned to 41 isolates. STs 451 (13%), 447 (7%), 195 (6%) and 848 (5%) were the most common STs. The majority of CRAB isolates (44.3%) belonged to the CC92, followed by the CC447 (15.1%), CC109 (9.3%) and CC110 (3.4%), which corresponds to the IC2, 8, 1 and 7 respectively. Phylogenetic and recombination analysis suggested two major and one minor lineage in the population. Further linkage disequilibrium analysis suggested clonal nature of the population as recombination was noticed at a low frequency, which was not enough to split the clonal relationship. The knowledge of genetic structure of CRAB from this study will be invaluable to illustrate epidemiology, surveillance and understanding its global diversity.

The Role of Minocycline in the Treatment of Nosocomial Infections Caused by Multidrug, Extensively Drug and Pandrug Resistant Acinetobacter baumannii: A Systematic Review of Clinical Evidence

Treatment options for multidrug resistant Acinetobacter baumannii strains (MDR-AB) are limited. Minocycline has been used alone or in combination in the treatment of infections associated with AB. A systematic review of the clinical use of minocycline in nosocomial infections associated with MDR-AB was performed according to the PRISMA-P guidelines. PubMed-Medline, Scopus and Web of Science ^TM databases were searched from their inception until March 2019. Additional Google Scholar free searches were performed. Out of 2990 articles, 10 clinical studies (9 retrospective case series and 1 prospective single center trial) met the eligibility criteria. In total, 223 out of 268 (83.2%) evaluated patients received a minocycline-based regimen; and 200 out of 218 (91.7%) patients with available data received minocycline as part of a combination antimicrobial regimen (most frequently colistin or carbapenems). Pneumonia was the most common infection type in the 268 cases (80.6% with 50.4% ventilator-associated pneumonia). The clinical and microbiological success rates following minocycline treatment were 72.6% and 60.2%, respectively. Mortality was 20.9% among 167 patients with relevant data. In this systematic review, minocycline demonstrated promising activity against MDR-AB isolates. This review sets the ground for further studies exploring the role of minocycline in the treatment of MDR-AB associated infections.

Treatment of infections caused by multidrug-resistant Gram-negative bacteria: report of the British Society for Antimicrobial Chemotherapy/Healthcare Infection Society/British Infection Association Joint Working Party

The Working Party makes more than 100 tabulated recommendations in antimicrobial prescribing for the treatment of infections caused by multidrug-resistant (MDR) Gram-negative bacteria (GNB) and suggest further research, and algorithms for hospital and community antimicrobial usage in urinary infection. The international definition of MDR is complex, unsatisfactory and hinders the setting and monitoring of improvement programmes. We give a new definition of multiresistance. The background information on the mechanisms, global spread and UK prevalence of antibiotic prescribing and resistance has been systematically reviewed. The treatment options available in hospitals using intravenous antibiotics and in primary care using oral agents have been reviewed, ending with a consideration of antibiotic stewardship and recommendations. The guidance has been derived from current peer-reviewed publications and expert opinion with open consultation. Methods for systematic review were NICE compliant and in accordance with the SIGN 50 Handbook; critical appraisal was applied using AGREE II. Published guidelines were used as part of the evidence base and to support expert consensus. The guidance includes recommendations for stakeholders (including prescribers) and antibiotic-specific recommendations. The clinical efficacy of different agents is critically reviewed. We found there are very few good-quality comparative randomized clinical trials to support treatment regimens, particularly for licensed older agents. Susceptibility testing of MDR GNB causing infection to guide treatment needs critical enhancements. Meropenem- or imipenem-resistant Enterobacteriaceae should have their carbapenem MICs tested urgently, and any carbapenemase class should be identified: mandatory reporting of these isolates from all anatomical sites and specimens would improve risk assessments. Broth microdilution methods should be adopted for colistin susceptibility testing. Antimicrobial stewardship programmes should be instituted in all care settings, based on resistance rates and audit of compliance with guidelines, but should be augmented by improved surveillance of outcome in Gram-negative bacteraemia, and feedback to prescribers. Local and national surveillance of antibiotic use, resistance and outcomes should be supported and antibiotic prescribing guidelines should be informed by these data. The diagnosis and treatment of both presumptive and confirmed cases of infection by GNB should be improved. This guidance, with infection control to arrest increases in MDR, should be used to improve the outcome of infections with such strains. Anticipated users include medical, scientific, nursing, antimicrobial pharmacy and paramedical staff where they can be adapted for local use.

Risk factors for acquisition and mortality of multidrug-resistant Acinetobacter baumannii bacteremia: A retrospective study from a Chinese hospital

Bloodstream infection caused by Acinetobacter baumannii has become a major clinical concern, especially multidrug-resistant A baumannii (MDRAB). The aim of this study was to identify the risk factors of nosocomial acquired MDRAB bacteremia and to determine the risk factors related to the mortality of patients with MDRAB bacteremia. Patients with nosocomial acquired A baumannii bacteremia were enrolled between January, 2013 and December, 2017 at the First Affiliated Hospital, School of Medicine, Zhejiang University. Medical records were reviewed, and the clinical and microbial characteristics were collected. Among the 338 patients suffering from A baumannii bacteremia, 274 patients were infected with MDRAB bacteremia. Bacteremia-related mortality was 46.4% for the overall sample; 56.2% for MDRAB bacteremia patients, 4.7% for non-MDRAB bacteremia patients. The identified risk factors for developing MDRAB bacteremia were previous exposure to carbapenems [odds ratio (OR) 5.78, P = .005] and penicillins+β-lactamase inhibitors (OR 4.29, P = .009). Primary bacteremia tended to develop non-MDR bacteremia (OR 0.10, P = .002). The risk factors for MDRAB bacteremia-related mortality were old age (OR 1.02, P = .036), a high Pitt bacteremia score (OR 1.32, P < .001), bacteremia occurring after severe pneumonia (OR 8.66, P < .001), while catheter-related infection (OR 0.47, P = .049) and operations for treating infection (OR 0.51, P = .043) may have a better outcome. Patients with MDRAB had a higher mortality rate. Patients with previous carbapenems and penicillins+β-lactamase inhibitor exposure are at an increased risk of MDRAB bacteremia, whereas patients with primary bacteremia tended to develop non-MDR bacteremia. The risk factors for MDRAB bacteremia-related mortality were old age, a high Pitt bacteremia score, and bacteremia occurring after severe pneumonia, whereas catheter-related infection and operations for the treatment of infection may have a better outcome.

Epidemiology and treatment of antimicrobialresistant gram-negative bacteria in Korea

Antimicrobial resistance is becoming one of the greatest challenges to public health worldwide. Infections by antimicrobial-resistant organisms could result in the failure of treatment, increased medical costs, prolonged hospital stays, and an increased socioeconomic burden. Antimicrobial usage in Korea remains heavy, even after much effort to reduce their use. According to the Korean antimicrobial resistance surveillance system, the resistance rates of many bacteria are increasing. The resistance rate of Acinetobacter baumannii to imipenem in Korea increased to 85% in 2015, representing a major public threat. The reports of increased carbapenem resistance in Enterobacteriaceae are worrisome. More importantly, some carbapenem-resistant Enterobacteriaceae may result from the production of carbapenemases, which break down carbapenems. There are relatively few treatment options for extensively drug-resistant A. baumannii and carbapenem-resistant Enterobacteriaceae. Most reports are retrospective observational studies. Because there are little published data from randomized controlled trials, more data assessing antimicrobial treatment for extensively drug-resistant A. baumannii and carbapenem-resistant Enterobacteriaceae are needed to make treatment recommendations.

Fungi as Part of the Microbiota and Interactions with Intestinal Bacteria

The human microbiota consists of bacteria, archaea, viruses, and fungi that build a highly complex network of interactions between each other and the host. While there are many examples for commensal bacterial influence on host health and immune modulation, little is known about the role of commensal fungi inside the gut community. Up until now, fungal research was concentrating on opportunistic diseases caused by fungal species, leaving the possible role of fungi as part of the microbiota largely unclear. Interestingly, fungal and bacterial abundance in the gut appear to be negatively correlated and disruption of the bacterial microbiota is a prerequisite for fungal overgrowth. The mechanisms behind bacterial colonization resistance are likely diverse, including direct antagonism as well as bacterial stimulation of host defense mechanisms. In this work, we will review the current knowledge of the development of the intestinal bacterial and fungal community, the influence of the microbiota on human health and disease, and the role of the opportunistic yeast C. albicans. We will furthermore discuss the possible benefits of commensal fungal colonization. Finally, we will summarize the recent findings on bacterial-fungal interactions.

High excess costs of infections caused by carbapenem-resistant Gram-negative bacilli in an endemic region

The financial burden of antibiotic resistance is a serious concern worldwide. The aim of this study was to describe the excess costs associated with pneumonia, bacteraemia, surgical site infections and intra-abdominal infections (IAIs) caused by carbapenem-resistant Gram-negative bacilli in Medellín, Colombia, an endemic region for carbapenem resistance. A cohort study was conducted in a third-level hospital from 2014-2015. All patients with carbapenem-resistant and carbapenem-susceptible Gram-negative bacterial infections were included. Pharmaceutical, medical and surgical direct costs were described from the health system perspective. Excess costs were estimated from generalised linear models with gamma distribution and adjusted for variables that could affect the cost difference. A total of 218 patients were enrolled, 48 (22.0%) of whom were infected with carbapenem-resistant bacteria. IAIs were the most frequent. The adjusted total excess cost was US$3966 [95% confidence interval (CI) US$1684-6249], with a significantly higher cost for antibiotics, followed by hospital stay, laboratory tests and interconsultation. The highest excess cost was attributed mainly to the use of broad-spectrum antibiotics (US$1827, 95% CI US$1005-2648), followed by length of hospital stay (US$1015, 95% CI US$163-1867). The results of this study highlight the importance of designing antimicrobial stewardship programmes and infection control strategies in endemic regions to reduce the financial threat of antimicrobial resistance to health systems.

The difference in medical costs between carbapenem-resistant Acinetobacter baumannii and non-resistant groups: a case study from a hospital in Zhejiang province, China

This retrospective study aims to compare differences in the medical costs between inpatients infected/colonised with carbapenem-resistant (CRAB) and carbapenem-susceptible (CSAB) Acinetobacter baumannii in a hospital in Zhejiang province, China. Because the patient population was large, we randomly selected 60% of all inpatients with clinical specimens between 2013 and 2015. We classified the A. baumannii cases as CRAB or CSAB based on antibiotic susceptibility testing. Univariate and multivariate analyses were used to identify factors associated with the total medical cost (TMC). Those included in the study totalled 2980 inpatients, 71.3% of whom had CRAB infection/colonisation. Differences in the TMC between the CRAB and CSAB groups were lower by multivariate analyses than the differences obtained by univariate analyses. Carbapenem resistance was significantly associated with an approximately 1.5-fold increase in the TMC after accounting for confounding factors. Our study highlights the heavy financial burden imposed by A. baumannii and carbapenem resistance on the Chinese healthcare system.

Factors Leading to Transmission Risk of Acinetobacter baumannii

OBJECTIVES

To identify patient and healthcare worker factors associated with transmission risk of Acinetobacter baumannii during patient care.

DESIGN

Prospective cohort study.

SETTING

ICUs at a tertiary care medical center.

PATIENTS

Adult ICU patients known to be infected or colonized with A. baumannii.

MEASUREMENTS AND MAIN RESULTS

Cultures of skin, respiratory tract, and the perianal area were obtained from participants and evaluated for the presence of A. baumannii. Healthcare worker-patient interactions were observed (up to five interactions/patient) and activities were recorded. Healthcare worker hands/gloves were sampled at room exit (prior to hand hygiene or glove removal) and then evaluated for the presence of A. baumannii. Two hundred fifty-four healthcare worker-patient interactions were observed among 52 patients; A. baumannii was identified from healthcare worker hands or gloves in 77 (30%) interactions. In multivariate analysis, multidrug-resistant A. baumannii (odds ratio, 4.78; 95% CI, 2.14-18.45) and specific healthcare worker activities (touching the bed rail [odds ratio, 2.19; 95% CI, 1.00-4.82], performing a wound dressing [odds ratio, 8.35; 95% CI, 2.07-33.63] and interacting with the endotracheal tube or tracheotomy site [odds ratio, 5.15; 95% CI, 2.10-12.60]), were associated with hand/glove contamination.

CONCLUSIONS

Healthcare worker hands/gloves are frequently contaminated with A. baumannii after patient care. Patient-level factors were not associated with an increased transmission risk; however, having multidrug-resistant-A. baumannii and specific healthcare worker activities led to an increased contamination risk. Our findings reveal a potential selective advantage possessed by multidrug-resistant-A. baumannii in this environment and suggest possible areas for future research.

Risk Factors, Clinical Presentation, and Outcome of Acinetobacter baumannii Bacteremia

Infections caused by Acinetobacter baumannii (AB), an increasingly prevalent nosocomial pathogen, have been associated with high morbidity and mortality. We conducted this study to analyze the clinical features, outcomes, and factors influencing the survival of patients with AB bacteremia. We retrospectively examined the medical records of all patients developing AB bacteremia during their hospital stay at a tertiary care hospital in Beirut between 2010 and 2015. Ninety episodes of AB bacteremia were documented in eighty-five patients. Univariate analysis showed that prior exposure to high dose steroids, diabetes mellitus, mechanical ventilation, prior use of colistin and tigecycline, presence of septic shock, and critical care unit stay were associated with a poor outcome. High dose steroids and presence of septic shock were significant on multivariate analysis. Crude mortality rate was 63.5%. 70.3% of the deaths were attributed to the bacteremia. On acquisition, 39 patients had septicemia. Despite high index of suspicion and initiation of colistin and/or tigecycline in 18/39 patients, a grim outcome could not be averted and 37 patients died within 2.16 days. Seven patients had transient benign bacteremia; three of which were treated with removal of the line. The remaining four did not receive any antibiotics due to withdrawal of care and died within 26.25 days of acquiring the bacteremia, with no signs of persistent infection on follow up. A prolonged hospital stay is frequently associated with loss of functionality, and steroid and antibiotic exposure. These factors seem to impact the mortality of AB bacteremia, a disease with high mortality rate and limited therapeutic options.

Increased Costs Associated with Bloodstream Infections Caused by Multidrug-Resistant Gram-Negative Bacteria Are Due Primarily to Patients with Hospital-Acquired Infections

The clinical and economic impacts of bloodstream infections (BSI) due to multidrug-resistant (MDR) Gram-negative bacteria are incompletely understood. From 2009 to 2015, all adult inpatients with Gram-negative BSI at our institution were prospectively enrolled. MDR status was defined as resistance to ≥3 antibiotic classes. Clinical outcomes and inpatient costs associated with the MDR phenotype were identified. Among 891 unique patients with Gram-negative BSI, 292 (33%) were infected with MDR bacteria. In an adjusted analysis, only history of Gram-negative infection was associated with MDR BSI versus non-MDR BSI (odds ratio, 1.60; 95% confidence interval [CI], 1.19 to 2.16; P = 0.002). Patients with MDR BSI had increased BSI recurrence (1.7% [5/292] versus 0.2% [1/599]; P = 0.02) and longer hospital stay (median, 10.0 versus 8.0 days; P = 0.0005). Unadjusted rates of in-hospital mortality did not significantly differ between MDR (26.4% [77/292]) and non-MDR (21.7% [130/599]) groups (P = 0.12). Unadjusted mean costs were 1.62 times higher in MDR than in non-MDR BSI ($59,266 versus $36,452; P = 0.003). This finding persisted after adjustment for patient factors and appropriate empirical antibiotic therapy (means ratio, 1.18; 95% CI, 1.03 to 1.36; P = 0.01). Adjusted analysis of patient subpopulations revealed that the increased cost of MDR BSI occurred primarily among patients with hospital-acquired infections (MDR means ratio, 1.41; 95% CI, 1.10 to 1.82; P = 0.008). MDR Gram-negative BSI are associated with recurrent BSI, longer hospital stays, and increased mean inpatient costs. MDR BSI in patients with hospital-acquired infections primarily account for the increased cost.

Predictors of mortality in bloodstream infections caused by multidrug-resistant gram-negative bacteria: 4 years of collection

The study was undertaken to describe the profile of patients and the characteristics of all multidrug-resistant gram-negative bacteria (MDR-GNB) and to assess mortality. We examined 138 patients with bloodstream infections (BSIs) caused by MDR-GNB. Clinical characteristics, antibiotic therapy, and in-hospital mortality were analyzed. Survivor and nonsurvivor subgroups were compared to identify predictors of mortality. The in-hospital mortality rate was 25.4%. Univariate analysis revealed that comorbidities and inadequate initial antimicrobial treatment could increase risk of death. In Cox regression analysis, mortality was independently associated with the age (P = .034), hospitalization in an intensive care unit (ICU) (P = .04), invasive procedures (P < .001), and Acute Physiology and Chronic Health Evaluation II scores (P < .001), whereas combination therapy or monotherapy was not associated with mortality (P = .829). Postantibiogram therapy was associated with hospitalization in an ICU (P = .006), Charlson comorbidity index score (P = .003), and inadequate initial antimicrobial treatment (P < .001). MDR-GNB strains and antimicrobial regimens were not the major risk factors of mortality. Inadequate initial antimicrobial treatment, invasive procedures, high Acute Physiology And Chronic Health Evaluation II scores, hospitalization in an ICU, and comorbidities were the important factors responsible for mortality. Although there was no difference between combination therapy and monotherapy in mortality, combined treatment may be more effective than monotherapy for patients in an ICU, with a Charlson comorbidity index score < 4, or inadequate initial antimicrobial treatment.

Application of Bacteriophage-containing Aerosol against Nosocomial Transmission of Carbapenem-Resistant Acinetobacter baumannii in an Intensive Care Unit

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii (CRAB) is associated with nosocomial infections worldwide. Here, we used phage as a potential agent to evaluate the efficacy of daily cleaning practices combined with a bacteriophage-containing aerosol against CRAB.

METHODS

A two-phase prospective intervention study was performed at a 945-bed public teaching hospital. From March to December 2013, we performed terminal cleaning using standard procedures plus an aerosol with active bacteriophage in the intensive care units to evaluate the impact on nosocomial incidence density, carbapenem-resistance rates and antimicrobial drug consumption amounts. Patients with culture proven CRAB infection were transferred to the isolation room when the phage aerosol cleaning had been completed.

RESULTS

A total of 264 new acquisitions of CRAB were identified in the intensive care units (191 in the pre-intervention period and 73 in the intervention period). The rates of new acquisitions of CRAB in the intensive care units decreased from 8.57 per 1000 patient-days in the pre-intervention period to 5.11 per 1000 patient-days in the intervention period (p = 0.0029). The mean percentage of resistant isolates CRAB decreased from 87.76% to 46.07% in the intensive care units (p = 0.001). All of the antimicrobials showed a significant reduction in consumption except imipenem.

CONCLUSIONS

The bacteriophage was successful in decreasing the rates of infection caused by CRAB across intensive care units in a large teaching hospital.

In vivo protein interaction network analysis reveals porin-localized antibiotic inactivation in Acinetobacter baumannii strain AB5075

The nosocomial pathogen Acinetobacter baumannii is a frequent cause of hospital-acquired infections worldwide and is a challenge for treatment due to its evolved resistance to antibiotics, including carbapenems. Here, to gain insight on A. baumannii antibiotic resistance mechanisms, we analyse the protein interaction network of a multidrug-resistant A. baumannii clinical strain (AB5075). Using in vivo chemical cross-linking and mass spectrometry, we identify 2,068 non-redundant cross-linked peptide pairs containing 245 intra- and 398 inter-molecular interactions. Outer membrane proteins OmpA and YiaD, and carbapenemase Oxa-23 are hubs of the identified interaction network. Eighteen novel interactors of Oxa-23 are identified. Interactions of Oxa-23 with outer membrane porins OmpA and CarO are verified with co-immunoprecipitation analysis. Furthermore, transposon mutagenesis of oxa-23 or interactors of Oxa-23 demonstrates changes in meropenem or imipenem sensitivity in strain AB5075. These results provide a view of porin-localized antibiotic inactivation and increase understanding of bacterial antibiotic resistance mechanisms.

Cost-Effectiveness of a Model Infection Control Program for Preventing Multi-Drug-Resistant Organism Infections in Critically Ill Surgical Patients

BACKGROUND

Interventions to contain two multi-drug-resistant Acinetobacter (MDRA) outbreaks reduced the incidence of multi-drug-resistant (MDR) organisms, specifically methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, and Clostridium difficile in the general surgery intensive care unit (ICU) of our hospital. We therefore conducted a cost-effective analysis of a proactive model infection-control program to reduce transmission of MDR organisms based on the practices used to control the MDRA outbreak.

METHODS

We created a model of a proactive infection control program based on the 2011 MDRA outbreak response. We built a decision analysis model and performed univariable and probabilistic sensitivity analyses to evaluate the cost-effectiveness of the proposed program compared with standard infection control practices to reduce transmission of these MDR organisms.

RESULTS

The cost of a proactive infection control program would be $68,509 per year. The incremental cost-effectiveness ratio (ICER) was calculated to be $3,804 per aversion of transmission of MDR organisms in a one-year period compared with standard infection control. On the basis of probabilistic sensitivity analysis, a willingness-to-pay (WTP) threshold of $14,000 per transmission averted would have a 42% probability of being cost-effective, rising to 100% at $22,000 per transmission averted.

CONCLUSIONS

This analysis gives an estimated ICER for implementing a proactive program to prevent transmission of MDR organisms in the general surgery ICU. To better understand the causal relations between the critical steps in the program and the rate reductions, a randomized study of a package of interventions to prevent healthcare-associated infections should be considered.

Biofilm Formation and Motility Depend on the Nature of the Acinetobacter baumannii Clinical Isolates

Acinetobacter baumannii is a nosocomial pathogen involved in various infections ranging from minor soft-tissue infections to more severe infections such as ventilator-associated pneumonia and bacteremia. The severity and the type of infections depend on the genetic and phenotypic variations of the strains. In this study, we compared the extent of biofilm formation and motility displayed by 60 multidrug-resistant A. baumannii clinical strains isolated from blood and sputum samples from patients from Southern India. Our results showed that isolates from the sputum samples formed significantly more robust biofilm compared to the blood isolates. On the other hand, we observed that the blood isolates were more motile than the sputum isolates. To the best of our knowledge, this is the first study that systematically evaluated the correlation between these two phenotypic traits and the nature of the isolates.

Nascent regional system for alerting infection preventionists about patients with multidrug-resistant gram-negative bacteria: implementation and initial results

OBJECTIVE

To build and to begin evaluating a regional automated system to notify infection preventionists (IPs) when a patient with a history of gram-negative rod multidrug-resistant organism (GNRMDRO) is admitted to an emergency department (ED) or inpatient setting.

DESIGN

Observational, retrospective study.

SETTING

Twenty-seven hospitals, mostly in the Indianapolis metropolitan area, in a health information exchange (HIE).

PATIENTS

During testing of the new system: 80,180 patients with microbiology cultures between October 1, 2013, and December 31, 2013; 573 had a GNRMDRO. METHODS/INTERVENTION: A Health Level Seven (HL7) data feed from the HIE was obtained, corrected, enhanced, and used for decision support (secure e-mail notification to the IPs). Retrospective analysis of patients with microbiology data (October 1, 2013, through December 31, 2013) and subsequent healthcare encounters (through February 6, 2014).

RESULTS

The 573 patients (median age, 66 years; 68% women) had extended-spectrum β-lactamase-producing Enterobacteriaceae (78%), carbapenem-resistant Enterobacteriaceae (7%), Pseudomonas aeruginosa (9%), Acinetobacter baumannii (3%), or other GNR (3%). Body sources were urine (68%), sputum/trachea/bronchoalveolar lavage (13%), wound/skin (6%), blood (6%), or other/unidentified (7%). Between October 1, 2013, and February 6, 2014, 252 (44%) of 573 had an ED or inpatient encounter after the GNRMDRO culture, 47 (19% of 252) at an institution different from where the culture was drawn. During the first 7 weeks of actual alerts (January 29, 2014, through March 19, 2014), alerts were generated regarding 67 patients (19 of 67 admitted elsewhere from where the culture was drawn).

CONCLUSIONS

It proved challenging but ultimately feasible to create a regional microbiology-based alert system. Even in a few months, we observed substantial crossover between institutions. This system, if it contributes to timely isolation, may help reduce the spread of GNRMDROs.

Impact of empirical antimicrobial therapy on the outcome of critically ill patients with Acinetobacter bacteremia

RATIONALE:

Empirical antimicrobial therapy (EAT) for Acinetobacter infections may not be appropriate as it tends to be multidrug-resistant. This study evaluated the relationship between appropriate EAT and the outcomes of Intensive Care Unit (ICU) patients with Acinetobacter bacteremia.

METHODS:

This is a retrospective study of patients admitted to a medical-surgical ICU (2005-2010) and developed Acinetobacter bacteremia during the stay. Patients were categorized according to EAT appropriateness, defined as administration of at least one antimicrobial agent to which the Acinetobacter was susceptible before susceptibility results were known. The relation between EAT appropriateness and outcomes was evaluated.

RESULTS:

Sixty patients developed Acinetobacter bacteremia in the 6-year period (age = 50 ± 19 years; 62% males; Acute Physiology and Chronic Health Evaluation II score = 28 ± 9; 98.3% with central lines; 67% in shock and 59% mechanically ventilated) on average on day 23 of ICU and day 38 of hospital stay. All isolates were resistant to at least three of the tested antimicrobials. Appropriate EAT was administered to 60% of patients, mostly as intravenous colistin. Appropriate EAT was associated with lower ICU mortality risk (odds ratio: 0.15; 95% confidence interval: 0.03-0.96) on multivariate analysis.

CONCLUSIONS:

In this 6-year cohort, Acinetobacter bacteremia was related to multidrug-resistant strains. Appropriate EAT was associated with decreased ICU mortality risk.

Differential impact of infection control strategies on rates of resistant hospital-acquired pathogens in critically ill surgical patients

BACKGROUND

There were two major outbreaks of multi-drug resistant Acinetobacter baumannii (MDRA) in our general surgery and trauma intensive care units (ICUs) in 2004 and 2011. Both required aggressive multi-faceted interventions to control. We hypothesized that the infection control response may have had a secondary benefit of reducing rates of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and Clostridium difficile (C. diff).

METHODS

We analyzed data retrospectively from a prospective infection control database at a major university hospital and calculated the incidence rates of nosocomial MRSA, VRE, and C. diff before and after the two MDRA outbreaks (2004 and 2011) in the general surgery and trauma ICUs, and two unaffected control ICUs: thoracic surgery ICU and medical ICU. We tracked incidence rates in 6 mos segments for 24 mos per outbreak and created a composite variable of "any resistant pathogen" for comparison.

RESULTS

The incidence rates of "any resistant pathogen" were significantly lower in the general surgery ICU after both outbreaks (24 to 11 cases per 1000 patient days in 2004, p=0.045 and 7.7 ->4.0 cases per 1000 patient days in 2011, p=0.04). This did not persist after 6 mos. The trauma ICU's rate of "any resistant pathogen" did not change after either outbreak (16 ->16.5 cases per 1000 patient days in 2004, p=0.44 and 4.6 ->1.9 cases per 1000 patient days in 2011, p=0.41). The rates in the control ICUs were unchanged during the study periods.

CONCLUSIONS

Rates of resistant pathogens were lower in the general surgery ICU after response to MDRA outbreaks in both 2004 and 2011 although the rates increased again with time. There were no changes in rates of resistant pathogens in the trauma ICU after MDRA outbreaks in 2004 and 2011. Outbreak responses may have a differential impact in general surgery ICU versus trauma ICUs.

Appropriate initial antibiotic therapy in hospitalized patients with gram-negative infections: systematic review and meta-analysis

Background

The rapid global spread of multi-resistant bacteria and loss of antibiotic effectiveness increases the risk of initial inappropriate antibiotic therapy (IAT) and poses a serious threat to patient safety. We conducted a systematic review and meta-analysis of published studies to summarize the effect of appropriate antibiotic therapy (AAT) or IAT against gram-negative bacterial infections in the hospital setting.

Methods

MEDLINE, EMBASE, and Cochrane CENTRAL databases were searched until May 2014 to identify English-language studies examining use of AAT or IAT in hospitalized patients with Gram-negative pathogens. Outcomes of interest included mortality, clinical cure, cost, and length of stay. Citations and eligible full-text articles were screened in duplicate. Random effect models meta-analysis was used.

Results

Fifty-seven studies in 60 publications were eligible. AAT was associated with lower risk of mortality (unadjusted summary odds ratio [OR] 0.38, 95 % confidence interval [CI] 0.30-0.47, 39 studies, 5809 patients) and treatment failure (OR 0.22, 95 % CI 0.14–0.35; 3 studies, 283 patients). Conversely, IAT increased risk of mortality (unadjusted summary OR 2.66, 95 % CI 2.12–3.35; 39 studies, 5809 patients). In meta-analyses of adjusted data, AAT was associated with lower risk of mortality (adjusted summary OR 0.43, 95 % CI 0.23–0.83; 6 studies, 1409 patients). Conversely, IAT increased risk of mortality (adjusted summary OR 3.30, 95 % CI 2.42–4.49; 16 studies, 2493 patients). A limited number of studies suggested higher cost and longer hospital stay with IAT. There was considerable heterogeneity in the definition of AAT or IAT, pathogens studied, and outcomes assessed.

Discussion

Using a large set of studies we found that IAT is associated with a number of serious consequences,including an increased risk of hospital mortality. Infections caused by drug-resistant, Gram-negative organisms represent a considerable financial burden to healthcare systems due to the increased costs associated with the resources required to manage the infection, particularly longer hospital stays. However, there were insufficient data that evaluated AAT for the outcome of costs among patients with nosocomialGram-negative infections.

Conclusions

IAT in hospitalized patients with Gram-negative infections is associated with adverse outcomes. Technological advances for rapid diagnostics to facilitate AAT along with antimicrobial stewardship, surveillance, infection control, and prevention is needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1123-5) contains supplementary material, which is available to authorized users.

Contamination of health care workers' coats at the University Teaching Hospital in Lusaka, Zambia: the nosocomial risk

Background

Health care Associated Infections (HAIs) are a major public health problem in both developed and developing countries. They pose a severe impact in resource-poor settings, where the rate of infection is estimated to be relatively high. Therefore, this study was conducted to establish empirical evidence related to HAIs in Zambia.

Method

This was a prospective cross-sectional study conducted from October, 2013 to May 2014 at the University Teaching Hospital (UTH) in Lusaka. A total of 107 white coats worn by health care-workers at UTH were sampled for possible bacteriological contamination.

Results

Of the 107 white coats screened, 94 (72.8 %) were contaminated with bacteria. There was no difference in the contamination levels between white coats worn for more than 60 min (47.8 %) compared to those worn for 30–60 min (46.7 %) (p = 0.612). Further, the antibiotic sensitivity tests indicated that the bacterial isolates were resistant to some of the antibiotics assessed. Isolates of Staphylococcus aureus and Klebsiella pnumoniae exhibited the highest resistance to most of the antibiotics assessed.

Conclusion

This study has shown that white coats worn by health care-workers at the University Teaching Hospital generally have high microbial contaminations and hence pose a nosocomial risk. It is therefore, recommended that white coats be regularly sanitized, and health care workers also be sensitized on public health risk of HAIs associated with contaminated coats.

Acinetobacter baumannii Extracellular OXA-58 Is Primarily and Selectively Released via Outer Membrane Vesicles after Sec-Dependent Periplasmic Translocation

Carbapenem-resistant Acinetobacter baumannii (CRAb) shelter cohabiting carbapenem-susceptible bacteria from carbapenem killing via extracellular release of carbapenem-hydrolyzing class D β-lactamases, including OXA-58. However, the mechanism of the extracellular release of OXA-58 has not been elucidated. In silico analysis predicted OXA-58 to be translocated to the periplasm via the Sec system. Using cell fractionation and Western blotting, OXA-58 with the signal peptide and C terminus deleted was not detected in the periplasmic and extracellular fractions. Overexpression of enhanced green fluorescent protein fused to the OXA-58 signal peptide led to its periplasmic translocation but not extracellular release, suggesting that OXA-58 is selectively released. The majority of the extracellular OXA-58 was associated with outer membrane vesicles (OMVs). The OMV-associated OXA-58 was detected only in a strain overexpressing OXA-58. The presence of OXA-58 in OMVs was confirmed by a carbapenem inactivation bioassay, proteomic analysis, and transmission electron microscopy. Imipenem treatment increased OMV formation and caused cell lysis, resulting in an increase in the OMV-associated and OMV-independent release of extracellular OXA-58. OMV-independent OXA-58 hydrolyzed nitrocefin more rapidly than OMV-associated OXA-58 but was more susceptible to proteinase K degradation. Rose bengal, an SecA inhibitor, inhibited the periplasmic translocation and OMV-associated release of OXA-58 and abolished the sheltering effect of CRAb. This study demonstrated that the majority of the extracellular OXA-58 is selectively released via OMVs after Sec-dependent periplasmic translocation. Addition of imipenem increased both OMV-associated and OMV-independent OXA-58, which may have different biological roles. SecA inhibitor could abolish the carbapenem-sheltering effect of CRAb.