Molecular characterization and antibiotic resistance of Acinetobacter baumannii in cerebrospinal fluid and blood

Predominance of extensively-drug resistant Acinetobacter baumannii carrying bla OXA-23 in Jordanian patients admitted to the intensive care units

BACKGROUND AND AIM

The global emergence of Acinetobacter baumannii is of great concern, especially inside intensive care units (ICUs). This study investigated the prevalence, antibiotic resistance, biofilm formation and genetic relatedness of A. baumannii recovered from ICU patients in three major hospitals in Jordan.

METHODS

The A. baumannii isolates included in this study were identified by the detection of the blaOXA-51 gene, and a multiplex PCR assay. Antibiotic susceptibility testing was performed using the disk diffusion and broth microdilution methods, and the ability of the isolates to form biofilms was tested using the 96-well plate assay. All isolates were tested for the presence of carbapenemases-encoding genes by PCR. Clonal relatedness was assessed by Rep-PCR and dendrogram analysis.

RESULTS

Overall, 148 A. baumannii isolates were identified, with 96.7% of the isolates recognized as carbapenem resistant A. baumannii. Based on their resistance patterns, 90% of the isolates were extensively resistant (XDR). The highest prevalence of carbapenemases-encoding genes was for blaOXA-23-like (96.7%), followed by blaADC (93.9.2%), blaVIM (56.8%) and blaNDM-1 (7.4%). Almost 80% of the isolates were able to form biofilms, with 63.2% classified as strong biofilm former. Rep-PCR and clustering analysis revealed 26 different clusters and the circulation of hospital-specific clones.

CONCLUSIONS

Our study revealed an alarming high prevalence of XDR, blaOXA-23-carrying and strong biofilm-producing A. baumannii among ICU patients. These findings call for continuous epidemiological surveillance and implementation of prevention strategies to reduce infections and dissemination of such a problematic pathogen inside the ICUs.

Establishment and validation of a dual qPCR method for the detection of carbapenem-resistant Acinetobacter baumannii in bloodstream infections

Objective

Bloodstream infections(BSIs) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) have a high mortality rate due to the high levels of drug resistance. There is an urgent need to establish a sensitive and accurate detection method to rapidly detect CRAB in BSIs.

Methods

A new method was developed based on fluorescence quantitative PCR (qPCR) targeting the specific region of 16sRNA and OXA-23 gene from CRAB. The parameters were evaluated and optimized. This qPCR method was further applied in the detection of AB from 30 clinical specimens.

Results

The qPCR method established in this study showed high specificity. The method successfully differentiated Acinetobacter baumannii(A. baumanii) from 26 other common pathogens in BSIs and identify the carbapenem resistance gene. The qPCR method shows a limit of detection (LOD) of 3×10-3 ng/μL, and displays good linear relationship between 16sRNA and OXA-23 and excellent repeatability (CV ≤2%). The results for the detection of 30 clinical specimens using this new qPCR method are in complete agreement with those using blood culture and drug susceptibility test.

Conclusion

The qPCR method established in this study has strong specificity, wide linear range, good repeatability, and a lower LOD than PCR (Non-fluorescence quantification). The method provides new technical support for the early clinical diagnosis of CRAB in BSIs.

Overall status of carbapenem resistance among clinical isolates of Acinetobacter baumannii: a systematic review and meta-analysis

BACKGROUND

Resistance to carbapenems, the first-line treatment for infections caused by Acinetobacter baumannii, is increasing throughout the world. The aim of the present study was to determine the global status of resistance to carbapenems in clinical isolates of this pathogen, worldwide.

METHODS

Electronic databases were searched using the appropriate keywords, including: 'Acinetobacter' 'baumannii', 'Acinetobacter baumannii' and 'A. baumannii', 'resistance', 'antibiotic resistance', 'antibiotic susceptibility', 'antimicrobial resistance', 'antimicrobial susceptibility', 'carbapenem', 'carbapenems', 'imipenem', 'meropenem' and 'doripenem'. Finally, following some exclusions, 177 studies from various countries were included in this study. The data were then subjected to a meta-analysis.

RESULTS

The average resistance rate of A. baumannii to imipenem, meropenem and doripenem was 44.7%, 59.4% and 72.7%, respectively. A high level of heterogeneity (I2 > 50%, P value < 0.05) was detected in the studies representing resistance to imipenem, meropenem and doripenem in A. baumannii isolates. Begg's and Egger's tests did not indicate publication bias (P value > 0.05).

CONCLUSIONS

The findings of the current study indicate that the overall resistance to carbapenems in clinical isolates of A. baumannii is relatively high and prevalent throughout the world. Moreover, time trend analysis showed that the resistance has increased from the year 2000 to 2023. This emphasizes the importance of conducting routine antimicrobial susceptibility testing before selecting a course of treatment, as well as monitoring and controlling antibiotic resistance patterns in A. baumannii strains, and seeking novel treatment options to lessen the emergence and spread of resistant strains and to reduce the treatment failure.

Analysis of risk factors and different treatments for infections caused by carbapenem-resistant Acinetobacter baumannii in Shaanxi, China

BACKGROUND

The global threat of Carbapenem-resistant Acinetobacter baumannii (CRAB) has intensified as resistance to carbapenems continues to rise in recent decades. We aimed to explore risk factors, molecular epidemiology, and antimicrobial therapy of CRAB infection.

METHODS

The clinical data of 110 patients infected with A. baumannii from December 2021 to December 2022 were retrospectively analyzed. Patients were divided into a carbapenem-resistance group (55 patients) and carbapenem-sensitive group (CSAB; 55 patients) based on resistance to carbapenem, and the risk factors of patients infected with CRAB were analyzed. Fifty-five patients with CRAB infection who received antimicrobial therapy were divided into a combination therapy group (45 patients) and a monotherapy group (10 patients), and differences between the two groups were compared. Whole-genome sequencing analysis was performed to assess resistance genes. Phylogenetic analysis was performed to explore the characteristics of CRAB isolates.

RESULTS

Among the total 110 patients, the rate of poor prognosis in the CRAB group was 43.6% (24/55). Mechanical ventilation (odds ratio [OR] = 5.364, 95% confidence interval [CI] 1.462-19.679, P = 0.011) and puncture (OR = 19.935, 95% CI 1.261-315.031, P = 0.012) were independent risk factors for CRAB infection. Of 55 patients in the antimicrobial regimen study, 45 received combination therapy (including dual, triple, or quadruple antibiotic therapy) and 10 received monotherapy. Univariate analysis revealed significant differences between the combination group and monotherapy group for admission to the intensive care unit and wound infection (P < 0.05). The CRAB strains of 26 patients taking carbapenem-based combination therapy were mainly ST208, ST1968, and ST195, among which patients with ST1968 strains had higher 28-day mortality. Furthermore, the blaOXA-23 gene was harbored in ST1968, ST195, and ST208.

CONCLUSIONS

Mortality was significantly higher in patients infected with CRAB than with CSAB. Mechanical ventilation and puncture were independent risk factors in predicting CRAB infections. The distribution of CRAB was dominated by ST208, ST1968, and ST195, among which patients with ST1968 had higher 28-day mortality. The blaOXA-23 gene appears to be widely disseminated.

Antibiotic Resistance and Virulence Factors in Clinical Isolates of Stenotrophomonas maltophilia from Hospitalized Patients in Tehran, Iran

Stenotrophomonas maltophilia causes challenging infections in immunocompromised patients, exhibiting increasing resistance to multiple antimicrobials and possessing various virulence genes, including emerging resistance to trimethoprim-sulfamethoxazole. A total of 80 clinical isolates of S. maltophilia were collected from multiple hospitals in Tehran, Iran. This study conducted an analysis of antibiotic susceptibility by disc diffusion method and E-test assay, resistance and virulence gene frequencies were examined by PCR-sequencing, and multilocus sequencing typing (MLST) was performed for strain typing. Across the tested isolates, we observed notably high resistance rates for imipenem 80 (100%), meropenem 78(97.5%), and ceftazidime 72 (90%), while trimethoprim-sulfamethoxazole (SXT) showed a lower resistance rate of 2 (2.5%). Minocycline and levofloxacin demonstrated the highest susceptibility rates, with 70 (87.5%) and 80 (100%), respectively. The prevalence of antibiotic resistance genes bla L1, and bla L2 was 71 (88.75%) and 76 (95%), respectively. Additionally, the PCR analysis revealed that the frequency of virulence genes (fliC, virB, papD, pilU, hlyIII, stmPr1, and stmPr2) was 78 (97.5%), 77 (96.25%), 58 (72.5%), 77 (96.2%), 76 (95%), 31 (38.75%), and 80 (100%), respectively. Resistance to SXT isolate belong to the sequence type (ST15) and exhibits allelic profiles of (10, 29, 21, 21, 32, 32, and 10). The data obtained from our investigation have indicated that SXT remains an efficacious antibiotic and also highlighted the importance of effective management, identification of resistant isolates, and typing methods to address the global prevalence of antibiotic resistance in S. maltophilia.

Sequential Immune Acquisition of Monoclonal Antibodies Enhances Phagocytosis of Acinetobacter baumannii by Recognizing ATP Synthase

Objectives: The aim of this study was to prepare monoclonal antibodies (mAbs) that broadly target Acinetobacter baumannii and protect against infection by multi-drug-resistant (MDR) A. baumannii from different sources. Methods: mAb 8E6 and mAb 1B5 were prepared by sequentially immunizing mice with a sublethal inoculation of three heterogeneous serotypes of pan-drug-resistant (PDR) A. baumannii, ST-208, ST-195, and ST-229. Results: The cross-recognition of heterogeneous bacteria (n = 13) by two mAbs and potential targets was verified, and the in vitro antibacterial efficacy of mAbs was assessed. The median killing rate of mAb 8E6 against A. baumannii in the presence of complement and dHL-60 cells was found to be 61.51%, while that of mAb 1B5 was 41.96%. When only dHL-60 cells were present, the killing rate of mAb 8E6 was 65.73%, while that of mAb 1B5 was 69.93%. We found that mAb 8E6 and mAb 1B5 broadly targeted MDR A. baumannii on the ATP synthase complex and were equipped with an antibacterial killing ability by enhancing the innate immune bacteriolytic effect of ST-208 and ST-195 strains. Both monoclonal antibodies were validated to protect against respiratory infection at 4 and 24 h via enhancing the release of innate immune substances and inflammatory cytokines, effectively shortening the disease period in mice. Conclusions: mAb 8E6 and mAb 1B5 significantly enhanced the opsonization process of phagocytosis against A. baumannii strains prevalent in southern China by targeting ATP synthase antigens thereof, resulting in protective effects in mice.

Factors associated with antibiotic resistance and survival analysis of severe pneumonia patients infected with Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa: A retrospective cohort study in Jakarta, Indonesia

Background

Antimicrobial resistance is one of the most significant challenges to global public health and the risk factors in severe pneumonia are constantly growing. Therefore, this study aimed to identify factors associated with antimicrobial resistance and conduct survival analysis of severe pneumonia patients with single and multiple pathogens in the National Referral Hospital, Jakarta, Indonesia.

Methods

A retrospective method was used, and secondary data were collected from severe pneumonia patients admitted to the intensive care unit at Cipto Mangunkusumo National Referral Hospital, Jakarta, Indonesia, from January 2016 to December 2022. Respiratory specimens were collected through bronchial washing. Furthermore, univariate and multivariate analyses were performed to analyze factors associated with antimicrobial resistance. Kaplan‒Meier survival curves were generated with the log-rank test to compare 30-day mortality between patients infected with single, dual, and multiple pathogens.

Results

The results showed that a total of 333 patients from 415 enrolled were analyzed. Klebsiella pneumoniae (35.4%), Acinetobacter baumannii (29.3%), and Pseudomonas aeruginosa (15.4%) were the most frequently isolated Gram-negative pathogens. Factors associated with resistance to aminoglycoside, carbapenem, and quinolone were sepsis, cerebrovascular disease, and ventilator-associated pneumonia, as indicated by p < 0.05. In addition, the Kaplan-Meier curves showed that multiple pathogens influenced the survival rate of severe pneumonia patients (p < 0.05).

Conclusions

Sepsis, cerebrovascular disease, and ventilator-associated pneumonia were associated with antimicrobial resistance in severe pneumonia patients. The survival rate of patients infected with multiple pathogens was low. This suggests the importance of further awareness regarding empirical antibiotic stewardship and mortality assessment in severe pneumonia patients.

Phage therapy combats pan drug-resistant Acinetobacter baumannii infection safely and efficiently

Phage therapy offers a promising approach to combat the growing threat of antimicrobial resistance. Yet, key questions remain regarding dosage, administration routes, combination therapy, and the causes of therapeutic failure. In this study, we focused on a novel lytic phage, ФAb4B, which specifically targeted the Acinetobacter baumannii strains with KL160 capsular polysaccharide, including the pan-drug resistant A. baumannii YQ4. ФAb4B exhibited the ability to effectively inhibit biofilm formation and eradicate mature biofilms independently of dosage. Additionally, it demonstrated a wide spectrum of antibiotic-phage synergy and did not show any cytotoxic or haemolytic effects. Continuous phage injections, both intraperitoneally and intravenously over 7 d, showed no acute toxicity in vivo. Importantly, phage therapy significantly improved neutrophil counts, outperforming ciprofloxacin. However, excessive phage injections suppressed neutrophil levels. The combinatorial treatment of phage-ciprofloxacin rescued 91% of the mice, a superior outcome compared to phage alone (67%). The efficacy of the combinatorial treatment was independent of phage dosage. Notably, prophylactic administration of the combinatorial regimen provided no protection, but even when combined with a delayed therapeutic regimen, it saved all the mice. Bacterial resistance to the phage was not a contributing factor to treatment failure. Our preclinical study systematically describes the lytic phage's effectiveness in both in vitro and in vivo settings, filling in crucial details about phage treatment against bacteriemia caused by A. baumannii, which will provide a robust foundation for the future of phage therapy.

Molecular epidemiology of Acinetobacter baumannii during COVID-19 at a hospital in northern China

BACKGROUND

The wide spread of carbapenem-resistance clones of Acinetobacter baumannii has made it a global public problem. Some studies have shown that the prevalence of Acinetobacter baumannii clones can change over time. However, few studies with respect to the change of epidemiological clones in Acinetobacter baumannii during Corona Virus Disease 2019 (COVID-19) were reported. This study aims to investigate the molecular epidemiology and resistance mechanisms of Acinetobacter baumannii during COVID-19.

RESULTS

A total of 95 non-replicated Acinetobacter baumannii isolates were enrolled in this study, of which 60.0% (n = 57) were identified as carbapenem-resistant Acinetobacter baumannii (CRAB). The positive rate of the blaOXA-23 gene in CRAB isolates was 100%. A total of 28 Oxford sequence types (STs) were identified, of which the most prevalent STs were ST540 (n = 13, 13.7%), ST469 (n = 13, 13.7%), ST373 (n = 8, 8.4%), ST938 (n = 7, 7.4%) and ST208 (n = 6, 6.3%). Differently, the most widespread clone of Acinetobacter baumannii in China during COVID-19 was ST208 (22.1%). Further study of multidrug-resistant ST540 showed that all of them were carrying blaOXA-23, blaOXA-66, blaADC-25 and blaTEM-1D, simultaneously, and first detected Tn2009 in ST540. The blaOXA-23 gene was located on transposons Tn2006 or Tn2009. In addition, the ST540 strain also contains a drug-resistant plasmid with msr(E), armA, sul1 and mph(E) genes.

CONCLUSION

The prevalent clones of Acinetobacter baumannii in our organization have changed during COVID-19, which was different from that of China. ST540 strains which carried multiple drug-resistant mobile elements was spreading, indicating that it is essential to strengthen the molecular epidemiology of Acinetobacter baumannii.

Drug‑resistant Acinetobacter baumannii: From molecular mechanisms to potential therapeutics (Review)

Bacterial drug resistance is increasingly becoming an important problem that needs to be solved urgently in modern clinical practices. Infection caused by Acinetobacter baumannii is a serious threat to the life and health of patients. The drug resistance rate of Acinetobacter baumannii strains is increasing, thus research on the drug resistance of Acinetobacter baumannii has also seen an increase. When patients are infected with drug-resistant Acinetobacter baumannii, the availability of suitable antibiotics commonly used in clinical practices is becoming increasingly limited and the prognosis of patients is worsening. Studying the molecular mechanism of the drug resistance of Acinetobacter baumannii is fundamental to solving the problem of drug-resistant Acinetobacter baumannii and potentially other 'super bacteria'. Drug resistance mechanisms primarily include enzymes, membrane proteins, efflux pumps and beneficial mutations. Research on the underlying mechanisms provides a theoretical basis for the use and development of antibiotics and the development of novel treatment methods.

Antimicrobial Resistance in Romania: Updates on Gram-Negative ESCAPE Pathogens in the Clinical, Veterinary, and Aquatic Sectors

Multidrug-resistant Gram-negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, and members of the Enterobacterales order are a challenging multi-sectorial and global threat, being listed by the WHO in the priority list of pathogens requiring the urgent discovery and development of therapeutic strategies. We present here an overview of the antibiotic resistance profiles and epidemiology of Gram-negative pathogens listed in the ESCAPE group circulating in Romania. The review starts with a discussion of the mechanisms and clinical significance of Gram-negative bacteria, the most frequent genetic determinants of resistance, and then summarizes and discusses the epidemiological studies reported for A. baumannii, P. aeruginosa, and Enterobacterales-resistant strains circulating in Romania, both in hospital and veterinary settings and mirrored in the aquatic environment. The Romanian landscape of Gram-negative pathogens included in the ESCAPE list reveals that all significant, clinically relevant, globally spread antibiotic resistance genes and carrying platforms are well established in different geographical areas of Romania and have already been disseminated beyond clinical settings.

Bacterial Resistance in Hospital-Acquired Infections Acquired in the Intensive Care Unit: A Systematic Review

PURPOSE

In this review we present the status of the prevalence of bacteria resistant to antibiotics and the main antibiotic resistance genes that are reported in infections acquired in intensive care units (ICU) around the world.

METHODS

A systematic review based on the PRISMA guide was carried out, from the Science Direct, Redalyc, Scopus, Hinari, Scielo, Dialnet, PLOS, ProQuest, Taylor, Lilacs and PubMed/Medline databases. Inclusion criteria of this review were original research study published in a scientific journal in a 10-year time span from 1 January 2017 and 30 April 2022.

RESULTS

A total of 1686 studies were identified, but only 114 studies were considered eligible for inclusion. Klebsiella pneumoniae and Escherichia coli resistant to carbapenems and producers of extended-spectrum β-lactamases (ESBL) are the most frequently isolated pathogens in ICUs in Asia, Africa and Latin America. The blaOXA and blaCTX were antibiotic resistance genes (ARG) most commonly reported in different geographic regions (in 30 and 28 studies, respectively). Moreover, multidrug-resistant (MDR) strains were reported in higher frequency in hospital-acquired infections. Reports of MDR strains vary between continents, with the majority of publications being in Asia and between countries, with Egypt and Iran being highlighted. There is a predominance of few bacterial clones with MDR phenotype, for example, clonal complex 5 Methicillin-Resistant Staphylococcus aureus (CC5-MRSA) circulates frequently in hospitals in the United States, clone ST23-K. pneumoniae is reported in India and Iran, and clone ST260 carbapenemase-producing P. aeruginosa in the United States and Estonia.

CONCLUSION

Our systematic review reveals that ESBL- and carbapenemase-producing K. pneumoniae and E. coli are the most problematic bacteria that are reported, mainly in tertiary hospitals in Asia, Africa, and Latin America. We have also found propagation of dominant clones with a high degree of MDR, becoming a problem due to its high capacity to cause morbidity, mortality and additional hospital costs.

Characterization of carbapenem resistant Acinetobacter baumannii ST540 and Klebsiella pneumoniae ST2237 isolates in a pneumonia case from China

AIMS

This study aimed to characterize the chromosome and plasmid sequences, and determine the transferability of plasmids in carbapenem-resistance Acinetobacter baumannii (A. baumannii) DD520 and Klebsiella pneumoniae (K. pneumoniae) DD521 isolates from the same patient who was co-infected in a hospital in China.

METHODS AND RESULTS

Both isolates DD520 and DD521 exhibited multi-drug resistance phenotype, especially the former isolate which was resistant to 9 classes of antimicrobials including carbapenems, quinolones, penicillins, cephalosporins, tetracyclines, phenicols, fosfomycins, sulfanilamides, and aminoglycosides. Carbapenem resistance genes of bla_OXA-23 and bla_OXA-66 were identified on the chromosome of A. baumannii DD520, and bla_KPC-2 was found in the plasmid pDD521.2 from K. pneumoniae DD521. Phylogenetic analysis revealed that A. baumannii DD520 belonged to the ST540 clone, and K. pneumoniae DD521 belonged to the ST2237 clone. Plasmid analysis suggested that bla_KPC-2 was embedded into plasmid pDD521.2, which might be resulted from IS26- and Tn1721-mediated transposition. Plasmid pDD521.2 carrying bla_KPC-2 successfully transferred from K. pneumoniae DD521 into Escherichia coli C600, and carbapenems resistance also transferred in the conjugation.

CONCLUSIONS

To our knowledge, it was the first report of A. baumannii ST540 and K. pneumoniae ST2237 in the same patient in China. Both these two isolates exhibited resistance to carbapenem, which was likely to be resulted from carbapenem resistance genes bla_OXA-23 -bla_OXA-66 on the chromosome of A. baumannii ST540, and bla_KPC-2 in the plasmid of K. pneumoniae ST2237.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study highlighted that effective measures were urgent to prevent and control the co-infection caused by two or more carbapenem-resistance pathogens in the same patient.

Antimicrobial resistance profiles and associated factors of Acinetobacter and Pseudomonas aeruginosa nosocomial infection among patients admitted at Dessie comprehensive specialized Hospital, North-East Ethiopia. A cross-sectional study

Introduction

Hospital admitted patients are at increased risk of nosocomial infections (NIs) with multi-drug resistant (MDR) pathogens which are prevalent in the hospital environment. Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii) are common causes of NIs worldwide. The objective of this study is to determine antimicrobial resistance profiles and associated factors of Acinetobacter spp and P. aeruginosa NIs among hospitalized patients.

Methods

A cross-sectional study was conducted at Dessie comprehensive specialized hospital, North-East Ethiopia, from February 1 to April 30, 2020. A total of 254 patients who were suspected of the bloodstream, urinary tract, or surgical site nosocomial infections were enrolled consecutively. Socio-demographic and other variables of interest were collected using a structured questionnaire. Specimens were collected and processed following standard microbiological procedures. Antimicrobial susceptibility was determined using the Kirby-Bauer disk diffusion method following Clinical and Laboratory Standards Institute guidelines. Data were analyzed with SPSS version 23 and p-value < 0.05 was considered statistically significant.

Results

Overall, 13% of patients had nosocomial Acinetobacter spp and/or P. aeruginosa infections. The culture positivity rate was 16(6.3%) for Acinetobacter spp and 18(7.1%) for P. aeruginosa. Patients admitted in the surgical ward (Adjusted odds ratio (AOR):10.66;95% confidence interval (CI):1.22–93.23), pediatric ward (AOR:14.37;95%CI:1.4–148.5), intensive care unit (AOR:41.93;95%CI:4.7–374.7) and orthopedics (AOR:52.21;95%CI:7.5–365) were significantly at risk to develop NIs compared to patients admitted in the medical ward. Patients who took more than two antimicrobial types at admission were 94% (AOR:0.06; 95% CI:0.004–0.84) times more protected from NIs compared to those who did not take any antimicrobial. About 81% of Acinetobacter spp and 83% of P. aeruginosa isolates were MDR. Amikacin and meropenem showed promising activity against Acinetobacter spp and P. aeruginosa isolates.

Conclusion

The high prevalence of MDR Acinetobacter spp and P. aeruginosa nosocomial isolates enforce treating of patients with NIs based on antimicrobial susceptibility testing results.