This study substantiates an escalated incidence of carbapenem-resistant, MDR A. baumannii in post-surgical infections in Pakistan, highlighting the exigency for strengthened antimicrobial stewardship and infection control strategies in the hospitals of the region.
Abstract
Background: Acinetobacter baumannii is an important opportunistic pathogen responsible for healthcare-associated infections, particularly among critically ill, intensive care unit (ICU), and post-surgical patients. The emergence of carbapenem-resistant A. baumannii (CRAB) has become a major therapeutic challenge worldwide because of its multidrug-resistant nature and limited treatment options. Despite the increasing prevalence of CRAB in Pakistan, information regarding the molecular characterization of carbapenem resistance genes among isolates recovered from surgical site infections (SSIs) remains limited. Methods: A cross-sectional study was conducted from November 2023 to February 2024 at Khalifa Gul Nawaz Hospital, Bannu, Khyber Pakhtunkhwa, Pakistan. A total of (n = 118) surgical wound specimens were collected from patients with clinically diagnosed SSIs. A. baumannii isolates were identified using standard biochemical tests and confirmed by 16S rRNA gene sequencing. In vitro antimicrobial susceptibility was determined by Kirby–Bauer disk diffusion according to CLSI 2024 guidelines. In addition, the concentration-dependent inhibition-zone response of imipenem and meropenem against carbapenem-resistant isolates was evaluated using an agar well diffusion assay. Molecular detection of blaNDM-1 and blaOXA-23 was performed by polymerase chain reaction (PCR), and representative amplicons were subjected to Sanger sequencing for further analysis. Results: In the current study, the total number of (n = 118) wound specimens from healthcare-associated patients were processed, in which A. baumannii-positive isolates (n = 23, 19.5%) were documented. Its prevalence was higher in males (69.6%) compared to females, and was strongly associated (78.2%) with elderly patients (aged 51–68 years). In vitro susceptibility testing revealed that 91.3% of isolates harbored multidrug-resistant (MDR) attributes. Antimicrobial susceptibility profiling revealed high levels of multidrug resistance, with 82.6% of isolates resistant to imipenem and meropenem, as well as 100% resistance to aztreonam and gentamicin. Colistin showed the highest activity, with 87.0% of isolates remaining susceptible. In the agar well diffusion assay, measurable inhibition of the carbapenem-resistant isolates by imipenem and meropenem occurred only at higher concentrations. Molecular screening of resistance genes identified blaOXA-23 in 60.9% and blaNDM-1 in 30.4% of isolates. Co-expression of both genes was detected in some (n = 4) isolates. Among the selected MDR isolates included in the gene resistance analysis, imipenem and meropenem resistance were recorded in 9/14 blaOXA-23-positive isolates and 5/7 blaNDM-1-positive isolates. Conclusions: This study substantiates an escalated incidence of carbapenem-resistant, MDR A. baumannii in post-surgical infections. blaOXA-23 were documented as the predominant carbapenemase gene, with co-expression of blaNDM-1 in a substantial proportion of isolates. These findings provide an important phenotypic and molecular characterization of selected carbapenemase genes in healthcare-associated infections, highlighting the exigency for strengthened antimicrobial stewardship and infection control strategies in the hospitals of the region.
OBJECTIVE
Klebsiella pneumoniae, a major nosocomial pathogen, is increasingly associated with multidrug resistance and carbapenem production, posing a significant therapeutic challenge on a global scale. The study aimed to determine the distribution, antimicrobial susceptibility pattern, and molecular identification of blaKPC-2 and blaVIM genes among carbapenem-resistant K. pneumoniae isolated from clinical specimens.
METHODS
Between January and June 2024, a hospital-based cross-sectional study was carried out at Kirtipur Hospital in Nepal. Standard microbiological protocols were adopted for the processing of 5002 clinical samples. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method following CLSI guidelines. The modified carbapenem inactivation method (mCIM) and the EDTA-modified carbapenem inactivation method (eCIM) were used to confirm carbapenemase production phenotypically, and the polymerase chain reaction (PCR) was used to detect the blaKPC-2 and blaVIM genes at the molecular level.
RESULTS
Of the total samples, 18.3% (917) showed bacterial growth, with K. pneumoniae accounting for 7.6% (n = 70) of isolates, predominantly from wound/pus (35.7%), urine (32.8%), and blood (17.1%) specimens. High resistance was observed against imipenem (68.6%), ceftazidime (64.3%), and ceftriaxone (62.9%), whereas tigecycline and doxycycline remained the most effective ones. Twelve (30.8%) of the 39 carbapenem-resistant isolates were determined to be carbapenemases producers, all harboring blaKPC-2 (100%) and three (25%) additionally carrying blaVIM.
CONCLUSION
The dominance of KPC-mediated resistance among the hospitalized patients, underscores the need for rigorous infection control, ongoing molecular surveillance, and prudent antimicrobial stewardship to stop the spread of high-risk K. pneumoniae strains in healthcare environments.
Shashi Gurung, M. Upreti, Agrani Paudel et al.· BMC Microbiology· 0 citations
Background/Aims: Acinetobacter baumannii is an opportunistic gram-negative pathogen and an increasingly important cause of hospital-acquired infections, particularly in intensive care units. Its remarkable ability to rapidly acquire resistance mechanisms, especially against carbapenems, represents a major public health concern. This study aimed to investigate the molecular detection and characterization of OXA-type carbapenemase genes in A. baumannii isolates collected from various clinical sources in Baghdad, Iraq. Methods: Between March and July 2025, 36 non-repetitive A. baumannii isolates were obtained from patients with different infections. Identification was performed using standard biochemical tests, CHROMagar Acinetobacter, and the VITEK 2 system and was confirmed by PCR amplification of the intrinsic blaOXA-51 gene. Antimicrobial susceptibility testing was conducted according to CLSI guidelines. The prevalence of blaOXA-23, blaOXA-24, blaOXA-51, and blaOXA-58 genes was determined by PCR. Selected PCR products were sequenced and subjected to phylogenetic analysis. Results: Extensive antimicrobial resistance was observed among the isolates, particularly to carbapenems, with resistance rates of 83.3% for imipenem and 72.2% for meropenem. High resistance rates were also detected for fluoroquinolones and aminoglycosides, whereas colistin and tigecycline retained comparatively greater activity. PCR screening revealed prevalence rates of 100% for blaOXA-51, 86.1% for blaOXA-23, 69.4% for blaOXA-24, and 47.2% for blaOXA-58. Multiple blaOXA genes were detected in more than half of the isolates, suggesting horizontal gene transfer and local clonal expansion. Phylogenetic analysis demonstrated high similarity between local isolates and international reference strains, supporting the widespread dissemination of resistance determinants. Several nucleotide substitutions were identified within the blaOXA-23 and blaOXA-24 genes. Conclusion: The findings indicate that blaOXA-23 is the predominant contributor to carbapenem resistance among A. baumannii isolates in Baghdad, while blaOXA-24 and blaOXA-58 are also increasingly prevalent. The observed resistance patterns and phylogenetic relationships underscore the importance of continuous molecular surveillance, antimicrobial stewardship, and effective infection control measures to limit the spread of multidrug-resistant A. baumannii. These data contribute valuable regional information to the global understanding of antimicrobial resistance epidemiology.
A. A. Abdulhassan, Hiba Hazim Hamid, Sara Mahdi Al-Lami et al.· Cellular Physiology and Bioc...· 0 citations
Background Carbapenem-resistant Acinetobacter baumannii (CRAB) is priority pathogen for nosocomial infection control worldwide. This study aimed to elucidate differences in distribution, genotyping and antimicrobial resistance patterns between CRAB and carbapenem-susceptible Acinetobacter baumannii (CSAB) strains isolated from healthcare environments. Materials and methods A total of 1,812 environmental samples were collected from 10 medical institutions in Pudong New Area between June and December 2024 for the identification of A. baumannii. Antimicrobial susceptibility testing, whole-genome sequencing, and bioinformatic analysis were performed to reveal molecular characteristics of A. baumannii. Results A total of 81 A. baumannii strains were detected, with 39.51% CRAB (n = 32) and 60.49% CSAB (n = 49). CRAB strains were highly prevalent in intensive care units (ICUs, accounting for 83.33%) and patient-contact items, whereas CSAB were more evenly distributed. MLST analysis identified ST2 as dominant CRAB clone (78.13%), followed by ST164 (18.75%). CRAB isolates demonstrated 100% resistance to multiple antibiotics such as piperacillin/tazobactam and ciprofloxacin, whereas all CSAB isolates were susceptible to tested antibiotics except one ampicillin/sulbactam-resistant isolate. Carbapenem resistance in CRAB was predominantly mediated by class D carbapenemases, with carriage rate of the blaOXA-23 gene reaching 96.88%. Notably, six ST164 isolates co-harbored class B and class D carbapenemase genes, which may elevate resistance severity. Bioinformatic analysis indicated that 22.20% of resistance plasmids in CRAB were predicted to be conjugative. CRAB exhibited a more diverse and extensive virulence gene profile than CSAB strains. Conclusions The ICU environment was critical for CRAB control. ST2 and ST164 represented clones worthy of attention. CRAB exhibited stronger resistance, harbored more putatively conjugative plasmids and richer virulence-associated genes than CSAB, highlighting the need for targeted disinfection and surveillance of prevalent clones.
Yue Zhang, Yanru Liang, Yuanping Wang et al.· Frontiers in Cellular and In...· 0 citations
INTRODUCTION AND AIMS
Carbapenem-resistant Acinetobacter baumannii (CRAB) poses a serious global threat, prioritized by the WHO for new antibiotic development. The ECDC proposed the integration of genomic sequencing into surveillance. This study characterizes phenotypic and genotypic features of nationwide-collected CRAB isolates from Spanish hospitals (2016-2020).
MATERIALS AND METHODS
A total of 822 CRAB isolates sent to the Spanish reference laboratory were analyzed, and 108 representative isolates were selected from 48 hospitals in 25 Spanish provinces. Antibiotic susceptibility was determined according to EUCAST guidelines, and WGS was performed by Illumina. Resistome, virulome, phylogeny (cgMLST; 2390 genes), insertion sequences and plasmids were analyzed.
RESULTS
Of the 108 representative isolates, 68.5% produced OXA-23, 10.2% OXA-24, 7.4% OXA-58, 1.9% NDM-1 and 2.7% others. 3.7% co-produced two acquired carbapenemases, and six that did not have them showed the ISAba1 upstream of the blaOXA-51 like. The predominant STs were ST2pas (82.4%) and ST218Oxf (61.1%). blaOXA-66 chromosomal carbapenemase allele was present in 75% of the 108 isolates, armA 16s rRNA methyltransferase gene in 61.1% and the kL-7/OCL-18 was present in 59.3% of the isolates. The most active antibiotic was colistin. 65.4% of invasive cases were caused by isolates harboring all 38 virulence genes tested. In the 64.8% of isolates a plasmid type was detected, mainly pS32-1-like (54.6%).
CONCLUSIONS
In Spain, CRAB dissemination is driven by interregional spread of isolates belonging to the ST218Oxf/ST2Pas clones, characterized by the blaOXA-23/blaOXA-66 genotype, the presence of armA, the KL7/OCL18 capsular profile and the presence of pS32-1 plasmid.
Jared Sotelo, B. Aracil, J. Arca-Suárez et al.· International Journal of Ant...· 0 citations
Klebsiella pneumoniae, a leading cause of health care-associated infections, increasingly exhibits multidrug-resistant phenotypes, including resistance to carbapenems, the last-resort antimicrobials, and thus compromises treatment options. However, there is a paucity of data on antimicrobial profiles and carbapenemase gene distribution in K. pneumoniae in Rwanda. A cross-sectional study was conducted from February 1 to June 30, 2025, at the University Teaching Hospital of Butare. One-hundred-fifty isolates were analyzed using traditional bacteriological identification with the API 20E system. Antimicrobial susceptibility was assessed by the modified Kirby-Bauer disk diffusion method following Clinical and Laboratory Standards Institute 2024 guidelines, and carbapenemase genes were detected through conventional polymerase chain reaction. Data were analyzed using descriptive and inferential statistical methods, and a P-value less than 0.05 was considered statistically significant. As a result, Klebsiella isolates exhibited high resistance rates to trimethoprim-sulfamethoxazole (78%), cefuroxime (71.3%), cefixime (72%), and ceftriaxone (66.7%). Moderate resistance to ciprofloxacin (30%) and amoxicillin-clavulanate (42.7%) was observed. In contrast, lower resistance to amikacin (9.3%), imipenem (12%), meropenem (13.3%), and ertapenem (14%) was observed. Of the Carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates, 8 (38.1%) tested positive for the blaNDM gene, whereas none harbored the blaKPC gene. This study found a high resistance rate in K. pneumoniae to a widely used antibiotic and confirms the presence of blaNDM, highlighting the need for antimicrobial stewardship and strengthened local surveillance.
I. Nzabanterura, Samson Adewale Oyebadejo, Djibril Mbarushimana et al.· American Journal of Tropical...· 0 citations
Background Carbapenem−resistant Acinetobacter baumannii (CRAB) is a major threat to hospitalised patients, particularly in intensive care units and orthopaedic wards where implant−associated infections are common. However, the genomic and biofilm characteristics of CRAB in orthopaedic specialty hospitals remain poorly understood. Methods A total of 97 non-duplicate CRAB isolates collected between 2024 and 2025 were included. Antimicrobial susceptibility testing was performed using the VITEK-2 system, and biofilm formation was quantitatively assessed by the crystal violet method. Whole-genome sequencing (WGS) was carried out on the Illumina platform to analyse multilocus sequence typing (MLST), capsular types, resistance genes and virulence genes. A phylogenetic tree was constructed based on single-nucleotide polymorphisms (SNPs). Results ST2 was the dominant clone (95.88%) among the 97 isolates, and KL3 was the most prevalent capsular type (83.51%). All isolates carried intrinsic blaOXA-51-like genes, predominantly blaOXA-66 (95.88%). The most common acquired carbapenemase gene was blaOXA-23 (98.97%), and two isolates carried metallo-β-lactamase (MBL) genes (blaNDM-1 and blaNDM-5, respectively). All isolates exhibited a multidrug-resistant phenotype, with low resistance rates to tigecycline (6.19%) and minocycline (7.22%), and all remained susceptible to colistin. Strong biofilm formers accounted for 91.75% of isolates, and the carriage rates of biofilm-associated genes (bap, csuABCDE, pgaABCD) exceeded 90%. Phylogenetic analysis grouped the isolates into three clonal clades, with the majority (88.66%) falling into Clade C (ST2/KL3). This clade had been circulating in China as an outbreak lineage since 2018, gradually replacing Clade B (ST2/KL2), and became the dominant clone in 2024–2025. Conclusion CRAB isolates in this orthopaedic specialty hospital are dominated by the ST2/KL3 clone, which carries multiple resistance and virulence genes, exhibits a remarkably strong biofilm-forming ability, and shows a capsular switch trend from KL2 to KL3. Enhanced molecular surveillance of this dominant clone and increased attention to anti-biofilm strategies for orthopaedic implant-related infections are strongly recommended.
Tengfei Shi, Shaohan Xu, Xuexin Zheng et al.· Frontiers in Cellular and In...· 0 citations