Acta microbiologica et immunologica Hungarica最新文献

Stenotrophomonas maltophilia is an opportunistic pathogen that can cause infections especially in hospital settings and in immunocompromised individuals. Due to its resistance to many broad-spectrum antibiotics, treatment options that can be used in clinical practice are limited. This study aims to evaluate the susceptibility profiles of S. maltophilia isolates to antimicrobial agents commonly used in treatment and to investigate the presence of different classes of integrons and sul genes responsible for resistance. The study included 100 S. maltophilia isolates from various clinical samples sent to Balıkesir University Health Practice and Research Hospital Medical Microbiology Laboratory between 2017 and 2023. The BD Phoenix™ M50 Automated System was used for bacterial identification and antibiotic sensitivity testing. The susceptibility of isolates to trimethoprim-sulfamethoxazole was also studied by disk diffusion method. All isolates were investigated for sul1, sul2 genes and integron-associated integrase genes by polymerase chain reaction. The susceptibility rates of isolates to trimethoprim-sulfamethoxazole, levofloxacin and ceftazidime were determined as 96%, 66% and 38%, respectively. Polymerase chain reaction results showed, intI1 and sul1 genes were found to be positive together in two isolates resistant to trimethoprim-sulfamethoxazole, while sul1 and sul2 genes were found in two separate isolates sensitive to trimethoprim-sulfamethoxazole. The intI2 gene was not detected in any isolate. This study addresses the clinically important problems of S. maltophilia infections, which are increasingly difficult to treat due to intrinsic and acquired resistance mechanisms. By providing valuable information on antimicrobial susceptibility and resistance profiles of S. maltophilia isolates, it contributes to national data and guides efforts to control resistance and promote rational antibiotic use.

Stenotrophomonas maltophilia has emerged as an opportunistic pathogen originating from the environments, causing nosocomial infections, particularly in immunocompromised individuals and patients with cystic fibrosis. Although this microorganism exhibits low virulence, its infections are associated with high morbidity and mortality rates. S. maltophilia is intrinsically resistant to many antimicrobial agents used in clinical practices, therefore, posing significant treatment challenges. The multidrug resistance in S. maltophilia results from a combination of intrinsic, adaptive, and acquired mechanisms. S. maltophilia genome carries an array of genes encoding multidrug efflux pumps, which are key contributors to its broad-spectrum antibiotic resistance by expelling a wide range of drugs and reducing their intracellular concentrations to nontoxic levels. The majority of these efflux pumps belong to the resistance-nodulation-cell division (RND) family, while a lesser fraction is classified under the major facilitator superfamily (MFS) and the adenosine triphosphate binding cassette (ABC) family. In terms of function, substrate specificity, and complex gene regulation, these multidrug efflux pumps contribute not only to the survival of S. maltophilia under antibiotic stress but also to its resilience against other chemical challenges, including oxidative stress-generating substances and biocides. The roles of certain efflux pump systems in acquired and adaptive antibiotic resistance, as well as their potential applications as drug targets to enhance the efficacy of routinely used antibiotics through the use of small molecules capable of functioning as efflux pump inhibitors, are also discussed. A deeper understanding of these mechanisms can contribute to the more effective management against antibiotic-resistant S. maltophilia.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is one of the major Gram-negative bacteria in human infections, which can cause pneumonia, sepsis, meningitis, and abscess. However, the current therapy for CRKP infection is polymyxin and tigecycline. The aim of this study is to analyze the in vitro antibacterial effects of cefoperazone/sulbactam (SCF) combined with ceftazidime (CAZ), imipenem/cilastatin (IMI), and meropenem (MEM) against CRKP harbouring different antibiotic resistance genes. In this study, fifteen clinical isolates of CRKP from January to December 2023 were taken from our hospital for bacterial identification and confirmation of carbapenemase genotypes, and the minimum inhibitory concentration (MIC) of SCF, CAZ, IMI, and MEM were determined by broth microdilution method. The results of combined drug sensitivity test were determined by checkerboard method and characterized with fractional inhibitory concentration (FIC). The combined antibacterial activity was determined by time-kill curve. The results showed that among the 15 CRKP strains, 9 carried blaKPC gene, 3 carried blaNDM gene and 3 carried blaOXA-48-like gene. The MIC values determined by broth microdilution method showed better sensitivity of KPC-producing CRKP to four antimicrobial drugs including SCF. However, blaNDM as well as blaOXA-48-like genotypes showed strong resistance to all four antimicrobial drugs. The FIC values of SCF combined with CAZ, IMI and MEM showed that all tested antibacterial agents had the best effect on KPC-producing CRKP, and had no obvious additive effect on other CRKP. The results of time-kill curve showed that SCF combined with IMI had good antibacterial effect. This study found that SCF combined with IMI has a synergistic antibacterial effect on KPC producing carbapenem-resistant K. pneumoniae, which could provide reference for clinical practice.

Invasive aspergillosis primarily affects individuals with compromised immune systems. This study endeavors to suggest the importance of early diagnosis and treatment related to central nervous system (CNS) aspergillosis. Recognizing the typical and atypical imaging characteristics of CNS aspergillosis enables the early and aggressive treatment of an otherwise rapidly fatal infection. We reported a case of an elderly patient with a history of non-Hodgkin lymphoma and prostate cancer who underwent repeated chemotherapy and subsequently experienced a sudden disturbance of consciousness. The diagnosis was affirmed through metagenomic next-generation sequencing (mNGS) of sputum and cerebrospinal fluid. The treatment encompassed systemic antifungal agents and intrathecal injection of amphotericin B. Metagenomic sequencing of sputum and cerebrospinal fluid detected Aspergillus fumigatus and Aspergillus flavus, leading to a diagnosis of invasive pulmonary and CNS aspergillosis. Although the patient actively received combined systemic antifungal drugs (voriconazole and amphoteric B liposome) and intrathecal injection of amphotericin B, he ultimately succumbed to the infection. A review of similar cases from PubMed and Medline from 2014 to 2024, encompassing 64 patients, showed that while early diagnosis and combination therapy have improved survival rates, outcomes remain suboptimal. Invasive aspergillosis has a high mortality rate and requires early diagnosis and treatment. Metagenomic sequencing of pathogenic microorganisms constitutes a convenient approach to facilitate the early diagnosis of aspergillosis. Voriconazole is the preferred treatment for invasive aspergillosis. When CNS aspergillosis emerges, it might be necessary to combine other systemic antifungal agents with intrathecal injection of amphotericin B.

Listeria monocytogenes is a foodborne opportunistic pathogen, that causes outbreaks and fatal cases worldwide. However, only few studies have been published in Mexico reporting the prevalence of this pathogen in food. Therefore, the objective of this current study is to evaluate the prevalence of L. monocytogenes in cheese sold in Tamaulipas, Mexico, and its potential risk to the population. For this purpose, samples were taken in 100 stores during the months of February, June and October 2023, and a total of 300 cheese products in 10 municipalities of Tamaulipas, Mexico were collected. Identification was performed by culture and PCR. Ten virulence factors were also analyzed and susceptibility testing to 14 antibiotics was performed. As a result, a prevalence of L. monocytogenes was detected in 12%. The most frequently detected virulence factors were actA (83.3%, 30/36) and hly (83.3%, 30/36). The strains were resistant to only 9 of the 14 antibiotics tested. The strains showed resistance in higher percentage to sulfamethoxazole/trimethoprim (STX/TMP: 38.8%, 14/36), penicillin (PE: 16.6%, 6/36), tetracycline (TE: 13.8%, 5/36) and amoxicillin/clavulanic acid (AMC: 13.8%, 5/36). The results of the current study show the presence of L. monocytogenes in cheese products sold in Tamaulipas, Mexico. The low prevalence of L. monocytogenes and low resistance to antibiotics could imply a low risk for public health. However, it is necessary to implement monitoring of L. monocytogenes in food, to monitor its potential risk for the consumer.

The emergence of carbapenemase-producing Klebsiella pneumoniae poses a significant global health threat, particularly in hospital settings. This study reports on the first detection of a pandrug-resistant (PDR) high-risk ST15 K. pneumoniae strain co-producing NDM-1 and VIM-1 in Greece. The isolate was recovered from a blood culture of a male patient admitted to the Intensive Care Unit (ICU) of Volos Hospital in July 2024. Next generation Sequencing (NGS) confirmed the presence of blaNDM-1 and blaVIM-1 genes. Other beta-lactamase type (CTX-M-15) was detected in association with NDM and VIM enzymes. Furthermore, this isolate was resistant to other antimicrobial agents, including aminoglycosides [aac(3)-II, aac(3)-IIe, aac(6')-Ib, aadA1, aph(3″)-Ib, aph(6)-Id, aph(3')-Ia), chloramphenicol (catB3), fluoroquinolones (qnrS1) and sulfonamides (sul1 and sul2). The Multilocus Sequence Typing revealed that the strain belonged to ST15. According to Kaptive the strain belonged to KL48. Our study provides new data about MBL producing K. pneumoniae in Greece. Thus, we report for the first time the co-expression of blaNDM-1 and blaVIM-1 in our country in ST15 K. pneumoniae. This study provides crucial epidemiological data on MBL-producing K. pneumoniae in Greece and highlights the urgent need for enhanced surveillance, infection control strategies, and access to last-resort antibiotics such as aztreonam-avibactam.

Acinetobacter baumannii is a significant nosocomial pathogen recognized for its multidrug-resistance (MDR) and capacity to endure in hospital settings. This study aims to investigate the clonal relationships of A. baumannii isolates from diverse clinical samples, identify the sequence types of MDR isolates, and examine biofilm formation activity and biofilm-associated genes that contribute to persistence in hospital settings. A total of 90 A. baumannii isolates were analyzed. Bacterial identification and antibiotic susceptibility testing were conducted with MALDI-TOF MS and Vitek-2. REP-PCR was utilized to evaluate clonal connections, MLST was employed for specific isolates. Biofilm formation activity was assessed using the XTT reduction assay, and biofilm-associated genes were identified by PCR. REP-PCR revealed 29 genotypes, with Genotype A being identified as the endemic clone in 59% of isolates. Two isolates representing this genotype were found to belong to the ST2 clone. The majority of A. baumannii isolates possess biofilm-related genes and exhibit strong biofilm activity. In MDR isolates, ompA and csuE positivity were significantly higher than those non-MDR isolates (P = 0.003, P = 0.001). The csuE positive isolates were found to have significantly stronger biofilm activity than negative ones (P = 0.009). This study emphasizes the prevalence of a hospital-endemic, MDR A. baumannii genotype A, ST2 clone, and the genetic variability across isolates. No direct correlation was noted between MDR status and biofilm formation; however, some biofilm-related genes, notably csuE, were linked to stronger biofilm activity. These findings underscore the necessity for ongoing molecular surveillance and infection control measures to avert the dissemination of MDR A. baumannii in healthcare environments.

Infections caused by colistin resistant Klebsiella pneumoniae are a major global health challenge linked to high mortality rates worldwide. Increased incidence of hypervirulent and drug-resistant Klebsiella causing life-threatening infections in young healthy individuals and asymptomatic carriage in the community has been largely reported in the Asian-Pacific Rim. This study conducted a molecular analysis of two morphologically distinct variants of K. pneumoniae that caused bacteremia and sepsis in a patient. Colony morphology of the isolates was characterized in various growth media, and the morphological variants differed in their mucoviscosity. The isolates were found to be serotype K2 (highly associated with hypervirulent Klebsiella) by molecular serotyping using specific PCR primers. The multidrug-resistant nature of the colony variants was evaluated by antibiotic susceptibility testing and it was found to have a similar antibiogram pattern in in vitro. An increased minimum inhibitory concentration (MIC) of colistin (>64 μg mL-1) was detected in both isolates using broth microdilution, and they were found to be highly resistant to colistin. Molecular analysis revealed that the isolates possessed a chromosomal mutation in mgrB, which causes colistin resistance. The increased incidence of infection caused by colistin-resistant K. pneumoniae requires continuous monitoring, and appropriate measures are necessary to control its adaptive evolution in healthcare settings.

In this study, we evaluated the performance of modified rapid antimicrobial susceptibility test (mRAST) with 150 mm Mueller Hinton Agar (MHA) plates which was earlier standardized for 90 mm MHA by EUCAST. Blood culture bottles spiked with ATCC quality control strains were prepared. For quality control Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, and Enterococcus faecalis ATCC 29212 strains were used. By calculating and proportioning the surface areas of the plates comparing with 90 mm plates, 350 ± 50 µL undiluted blood culture samples were inoculated in 150 mm MHA, and 12 disks were placed. This process was repeated independently for three days and three times on each day for reproducibility. The mRAST test was performed on 50 samples with positive signals and gram-negative bacilli on Gram-stained samples (20 Klebsiella pneumoniae, 15 E. coli, 10 Acinetobacter baumannii, and five P. aeruginosa).Comparison of 90 mm MHA and 150 mm MHA showed that the categorical agreement of ATCC strains and 50 gram negative isolates was 100% and >95%, respectively, for all antibiotics. For K. pneumoniae, only 0.4 major error (ME) was detected at 4 h. For E. coli, 3.2, 1.6, and 1.5 ME were detected at 4, 8, and 20 h, respectively, whereas 1.6 very major error (VME) was detected at 4 h and 1.0 VME was detected at both 8, and 20 h, respectively. No errors were detected for P. aeruginosa or A. baumannii.These results indicated that 350 ± 50 µL of undiluted blood culture in 150 mm MHA was suitable for the mRAST test in vitro.

Often dismissed as contaminants in blood cultures, Corynebacterium species can also cause infective endocarditis, a severe condition. We report an unusual case of Corynebacterium propinquum endocarditis in a non-immunocompromised individual on a native valve. Conflicting clinical and microbiological data led to 16S ribosomal sequencing to confirm the causative agent. Our case illustrates C. propinquum as a cause of infective endocarditis, and it demonstrates the utility of ancillary molecular diagnostic techniques to identify etiologic agents in difficult cases of infective endocarditis. C. propinquum should be recognized as a potential cause of infective endocarditis even on a native valve.