In vitro antimicrobial susceptibility to isepamicin of 6,296 Enterobacteriaceae clinical isolates collected at a tertiary care university hospital in Greece

Antimicrobial susceptibility analysis of isepamicin combination treatments in Mycobacterium abscessus species

This study evaluated the antimicrobial potency of the combination of isepamicin (ISP) for Mycobacterium abscessus species (MABS). 34 clinical MABS strains were isolated from clinical samples. Of them, 11 (32.4 %) were M. abscessus subsp. abscessus (Mab), 22 (64.7 %) were M. abscessus subsp. massiliense (Mma), and one (2.9 %) was M. abscessus subsp. bolletii (Mbo). We compared susceptibility to sitafloxacin (STFX)-ISP and clarithromycin (CLR)-ISP combinations with those of the antimicrobial agents alone, and synergistic effects were observed in 41.2 % and 17.6 % when treated with STFX-ISP and CLR-ISP. By hierarchical cluster analysis, the isolates divided into treatment-sensitive and treatment-resistant groups. Non-Mma or rough colony isolates were significantly likely to belong to the treatment-sensitive group (p = 0.024, p < 0.001, respectively). These results suggest that the ISP-containing combination could be a new therapeutic strategy for MABS, especially in cases of non-Mma: treatment-refractory subspecies, and rough morphotypes: high-virulence morphotypes.

In-vitro Activity of Isepamicin against Gram-negative Bacteria in Comparison to Other Aminoglycosides Routinely used at a Teaching Hospital in Northern India

Background  Isepamicin is a 1-N-S-a-hydroxy-b-aminopropionyl derivative of gentamicin B and the spectrum of pathogenic microorganisms covered by it and its effectiveness is similar to that of amikacin except the action of aminoglycoside inhibitor enzymes is ineffectual on it. Material and Methods  We performed a prospective study in the Bacteriology section of the Department of Microbiology at a 1,600-bedded hospital in Northern India from Jan 2022 to March 2022. Isepamicin was tested for susceptibility against gram-negative bacteria, identified by routine biochemicals and matrix-assisted-desorption/ionization -time of flight-mass spectrometry (MALDI-TOF-MS) assay. The antibiotic susceptibility testing for each of the isolates was performed by Kirby Bauer's disc diffusion method, according to the CLSI 2019 guidelines. Results  The majority of isolates were obtained from blood samples (50, 39.1%). Among the non-inducible Enterobacteriaceae , Escherichia coli was least susceptible to amikacin (8/27, 29.63%) and most susceptible to isepamicin (18/27, 66.67%). Klebsiella pneumoniae followed the same pattern of susceptibility as E. coli and was least susceptible to Amikacin (20/46, 43.48%) and most susceptible to isepamicin (24/46, 52.17%). Enterobacter cloacae (6/7, 85.71%) was most susceptible to both amikacin and isepamicin, followed by 71.43% (5/7, 71.43%) susceptibility to gentamicin and tobramycin each. Enterobacter aerogenes was equally 53.33% (8/15) susceptible to all antibiotics. Pseudomonas aeruginosa was the most susceptible isolate to all antibiotics (18/21, 85.71%). Conclusion  Isepamicin is a potential antimicrobial agent for treating an array of gram-negative bacteria-associated infections and shows better in vitro activity than older aminoglycoside agents.

Detection of Carbapenem Resistance of Proteus mirabilis Strains Isolated from Foxes, Raccoons and Minks in China

Proteus mirabilis, an opportunistic pathogen, is found to be an emerging threat to both animals and humans for a variety of infections. However, the characteristics of P. mirabilis infections from foxes, raccoons and minks remain unclear. In this context, we identified the antibiotic resistance genes and virulence genes of P. mirabilis isolates from foxes, raccoons and minks in China. Most isolates showed resistance to florfenicol (90.57%), trimethoprim-sulfamethoxazole (73.58%), and imipenem (71.70%). A total of 73.58% of isolates were resistant to antibiotics from at least three or more classes, and were categorized as multi-drug resistant. A total of 33.33% of the isolates were resistant to antibiotics from seven classes. The most prevalent resistant were sul1 (94.34%), followed by floR, blaTEM, aac(6’)Ib-cr and blaOXA-1 with the detection rate of 88.68%, 83.02%, 71.70% and 60.38%, respectively. Among the 51 P. mirabilis isolates that were resistant to beta-lactam antibiotics, all isolates carried at least one beta-lactam gene. In addition, blaNDM and blaOXA-24 genes were firstly reported in carbapenem-resistant P. mirabilis isolates from foxes, raccoons and minks. All isolates exhibited the virulence genes ureC, zapA, pmfA, atfA and mrpA. P. mirabilis isolates carrying all detected 10 virulence genes from different animal species showed different lethal abilities in a G. mellonella larvae model. More importantly, the profiles of antibiotic resistance genes of isolates from fur animals and the environment were generally similar, and phylogenetic analysis showed that the P. mirabilis isolates from farm environment samples may have close relatedness with that from animals.

Investigation of isepamicin in vitro efficiency in Gram negative bacteria efficacy of isepamicin

CONTEXT

Isepamicin is a new semisynthetic aminoglycoside derived from gentamicin B and it is effective against Gram negative bacteria. Antibiotic resistance is an emerging problem and new options need for the treatment of infections caused by Gram negative bacteria.

AIMS

In this study we aimed to investigate the in vitro efficiency in carbapenem susceptible and nonsusceptible Enterobacterales and Pseudomonas aeruginosa.

METHODS AND MATERIAL

A total of 214 isolates of Gram-negative bacteria (Enterobacterales n = 129 and P. aeruginosa n = 85). Identification of the bacteria was tested in Vitek MS (Biomeriux, France). Susceptibility of isepamicin, amikacin, gentamicin, tobramycin and netilmicin was determined by Kirby Bauer disc diffusion method. The breakpoints for susceptibility to isepamicin, amikacin, gentamicin, streptomycin, tobramycin and netilmicin were evaluated according to the Comité de l'Antibiogramme dela Société Française de Microbiologie (CA-SFM) and EUCAST, respectively. Aminoglycoside modifying enzyme (AME) genes were investigated by multiplex PCR method.

RESULTS

Isepamicin susceptibility was determined as 92.3% for Enterobacterales and 67% for P. aeruginosa and 94.4% for carbapenem resistant Enterobacterales. The most common AME gene was aac (6')-Ib in both Enterobacterales (76%) and P. aeruginosa (14.1%). Seven of the isepamicin intermediate or resistant isolates were positive aac (6')-Ib in Enterobacterales and P. aeruginosa.

CONCLUSIONS

In this study, isepamicin showed good efficiency against both susceptible and carbapenem nonsusceptible Enterobacterales. But amikacin was prior to isepamicin P. aeruginosa isolates. Isepamicin could be a therapeutic option for the infections caused by Enterobacterales.

Structure-Activity Relationship of Flavin Analogues That Target the Flavin Mononucleotide Riboswitch

The flavin mononucleotide (FMN) riboswitch is an emerging target for the development of novel RNA-targeting antibiotics. We previously discovered an FMN derivative, 5FDQD, that protects mice against diarrhea-causing Clostridium difficile bacteria. Here, we present the structure-based drug design strategy that led to the discovery of this fluoro-phenyl derivative with antibacterial properties. This approach involved the following stages: (1) structural analysis of all available free and bound FMN riboswitch structures; (2) design, synthesis, and purification of derivatives; (3) in vitro testing for productive binding using two chemical probing methods; (4) in vitro transcription termination assays; and (5) resolution of the crystal structures of the FMN riboswitch in complex with the most mature candidates. In the process, we delineated principles for productive binding to this riboswitch, thereby demonstrating the effectiveness of a coordinated structure-guided approach to designing drugs against RNA.

In vitro susceptibility and resistance phenotypes in contemporary Enterobacter isolates in a university hospital in Crete, Greece

Aim: To study the evolution in the susceptibility of Enterobacter spp. in Crete, Greece from 2010 to 2015. Methods: Non-duplicate isolates were studied using automated systems. Phenotypic confirmatory tests were applied. Results: A total of 939 Enterobacter isolates were included. Colistin was the most active antibiotic (97.9%) followed by imipenem (96.1%), gentamicin (95.7%), tigecycline (91.8%), cefepime (89.4%), chloramphenicol (85.8%), fosfomycin (85.5%), trimethoprim/sulfamethoxazole (83.3%) and piperacillin/tazobactam (73.3%). Antibiotic resistance did not increase during the study period for most antibiotics. Lower susceptibility was observed among multidrug-resistant strains and carbapenem-nonsusceptible isolates. AmpC was the most common resistant mechanism (21%); carbapenemases (3.7%) and aminoglycoside-modifying enzymes (6.5%) were also detected. Conclusion: A significant proportion of Enterobacter spp. was resistant to several antibiotics, most notably β-lactams.

In vitro susceptibility and resistance phenotypes in contemporary Citrobacter isolates in a University Hospital in Crete, Greece

BACKGROUND

Data on Citrobacter spp. susceptibility are scarce. We sought to study the evolution in the susceptibility of 385 Citrobacter spp. at the University Hospital of Heraklion, Crete, Greece during a six-year period (2010-2015).

METHODS

Non-duplicate strains isolated from inpatients (intensive care unit, oncology, surgery, internal medicine, paediatrics) and outpatients were studied using Vitek 2. Phenotypic confirmatory tests were applied for detection of β-lactamases and aminoglycoside modifying enzymes.

RESULTS

C. freundii (172, 44.7%) and C. koseri (166, 43.1%) were the most commonly isolated species. C. braakii (34), C. amalonaticus (6), C. youngae (6) and C. sedlakii (1) were the remaining isolates. Colistin and fosfomycin were the most active antibiotics (both 99.2%) followed by carbapenems (99%) aminoglycosides (96.6-98.4%), tigecycline (96.1%), cefepime (94.8%), ciprofloxacin (94.3%), tetracycline (92.7%), trimethoprim/sulphamethoxazole (91.4%), chloramphenicol (88.1%), piperacillin/tazobactam (86.5%) and 3rd generation cephalosporins (85.7%). C. freundii were more resistant than C. koseri. Antibiotic resistance did not increase during the study period for most antibiotics. Lower susceptibility to all antibiotics was observed among multi-drug resistant (MDR) strains. AmpC was the most common resistant mechanism (10.9%); carbapenemases (1.3%) and aminoglycoside modifying enzymes (2.9%) were also detected. All AmpC producers were resistant to cephalosporins but not to carbapenems. In all but one isolates aminoglycoside resistance was accompanied by acquired β-lactamases.

CONCLUSIONS

Although Citrobacter species in general were susceptible, antibiotic susceptibility testing is required for the detection of resistant isolates.

Mechanisms of Resistance to Aminoglycoside Antibiotics: Overview and Perspectives

Aminoglycoside (AG) antibiotics are used to treat many Gram-negative and some Gram-positive infections and, importantly, multidrug-resistant tuberculosis. Among various bacterial species, resistance to AGs arises through a variety of intrinsic and acquired mechanisms. The bacterial cell wall serves as a natural barrier for small molecules such as AGs and may be further fortified via acquired mutations. Efflux pumps work to expel AGs from bacterial cells, and modifications here too may cause further resistance to AGs. Mutations in the ribosomal target of AGs, while rare, also contribute to resistance. Of growing clinical prominence is resistance caused by ribosome methyltransferases. By far the most widespread mechanism of resistance to AGs is the inactivation of these antibiotics by AG-modifying enzymes. We provide here an overview of these mechanisms by which bacteria become resistant to AGs and discuss their prevalence and potential for clinical relevance.

Trends of mortality due to septicemia in Greece: an 8-year analysis

BACKGROUND

Infectious diseases are among the major causes of death worldwide. We evaluated the trends of mortality due to septicemia in Greece and compared it with mortality due to other infections.

METHODS

Data on mortality stratified by cause of death during 2003-2010 was obtained from the Hellenic Statistical Authority. Deaths caused by infectious diseases were grouped by site of infection and analyzed using SPSS 17.0 software.

RESULTS

45,451 deaths due to infections were recorded in Greece during the 8-year period of time, among which 12.2% were due to septicemia, 69.7% pneumonia, 1.5% pulmonary tuberculosis, 0.2% influenza, 0.5% other infections of the respiratory tract, 7.9% intra-abdominal infections (IAIs), 2.5% urinary tract infections (UTIs), 2.2% endocarditis or pericarditis or myocarditis, 1.6% hepatitis, 1% infections of the central nervous system, and 0.7% other infections. A percentage of 99.4% of deaths due to septicemia were caused by bacteria that were not reported on the death certificate (noted as indeterminate septicemia). More deaths due to indeterminate septicemia were observed during 2007-2010 compared to 2003-2006 (3,558 versus 1,966; p<0.05).

CONCLUSION

Despite the limitations related to the quality of death certificates, this study shows that the mortality rate due to septicemia has almost doubled after 2007 in Greece. Proportionally, septicemia accounted for a greater increase in the mortality rate within the infectious causes of death for the same period of time. The emergence of resistance could partially explain this alarming phenomenon. Therefore, stricter infection control measures should be urgently applied in all Greek healthcare facilities.

Genetic characterization of tigecycline resistance in clinical isolates of Enterobacter cloacae and Enterobacter aerogenes

OBJECTIVES

The intrinsically encoded ramA gene has been linked to tigecycline resistance through the up-regulation of efflux pump AcrAB in Enterobacter cloacae. The molecular basis for increased ramA expression in E. cloacae and Enterobacter aerogenes, as well as the role of AraC regulator rarA, has not yet been shown. To ascertain the intrinsic molecular mechanism(s) involved in tigecycline resistance in Enterobacter spp., we analysed the expression levels of ramA and rarA and corresponding efflux pump genes acrAB and oqxAB in Enterobacter spp. clinical isolates.

METHODS

The expression levels of ramA, rarA, oqxA and acrA were tested by quantitative real-time RT-PCR. The ramR open reading frames of the ramA-overexpressing strains were sequenced; strains harbouring mutations were transformed with wild-type ramR to study altered ramA expression and tigecycline susceptibility.

RESULTS

Tigecycline resistance was mediated primarily by increased ramA expression in E. cloacae and E. aerogenes. Only the ramA-overexpressing E. cloacae isolates showed increased rarA and oqxA expression. Upon complementation with wild-type ramR, all Enterobacter spp. containing ramR mutations exhibited decreased ramA and acrA expression and increased tigecycline susceptibility. Exceptions were one E. cloacae strain and one E. aerogenes strain, where a decrease in ramA levels was not accompanied by lower acrA expression.

CONCLUSIONS

Increased ramA expression due to ramR deregulation is the primary mediator of tigecycline resistance in clinical isolates of E. cloacae and E. aerogenes. However, some ramA-overexpressing isolates do not show changes in ramR, suggesting alternate pathways of ramA regulation; the rarA regulator and the oqxAB efflux pump may also play a role in tigecycline resistance in E. cloacae.

Escherichia coli and Klebsiella pneumoniae bacteremia in patients with neutropenic fever: factors associated with extended-spectrum β-lactamase production and its impact on outcome

Escherichia coli and Klebsiella pneumoniae are main pathogens in neutropenic fever even if the proportion of Gram-positive cocci is increasing. Extended-spectrum β-lactamases (ESBL)-producing organisms are an emerging problem in nosocomial infection. Nevertheless, until now, information about risk factors for the acquisition and clinical outcomes of bacteremia due to ESBL-producing organisms is limited in neutropenic patients. From medical records collected between January 2007 and December 2008, we identified a total of 101 consecutive patients who developed bacteremia due to E. coli (n = 87) or K. pneumoniae (n = 14). Twenty-six (26 %) cases of bacteremia were caused by ESBL-producing organisms. A hospital stay of >2 weeks during the 3 months preceding bacteremia [adjusted odds ratio (OR), 5.887; 95 % confidence interval (CI), 1.572-22.041] and the use of broad-spectrum cephalosporins in the 4 weeks prior to bacteremia (adjusted OR, 6.186; 95 % CI, 1.616-23.683) were significantly related to the acquisition of ESBL. Twenty-four (92 %) of the ESBL-producing organisms were susceptible to either piperacillin-tazobactam or amikacin. Aminoglycosides (amikacin or isepamicin) were the main appropriate antimicrobial agents used against the ESBL-producing isolates during the initial empirical treatment (16/22, 73 %). However, the 30-day mortality rates for ESBL bacteremia and non-ESBL bacteremia were not significantly different (15 vs 5 %; p = 0.199). As alternatives to carbapenem, piperacillin-tazobactam plus amikacin or isepamicin combinations may be effective empirical therapeutic options for patients with neutropenic fever who are at high risk of developing bacteremia with ESBL-producing pathogens.

Epidemiology and antimicrobial sensitivities of 536 multi-drug-resistant gram-negative bacilli isolated from patients treated on surgical wards

BACKGROUND

In this era of increasing antimicrobial resistance, infections caused by multi-drug-resistant (MDR) gram-negative bacilli (GNB) are becoming more common and pose a challenge to all clinicians, including surgeons.

METHODS

We evaluated the epidemiology and antimicrobial sensitivities of GNB isolated from patients treated on surgical wards at the University Hospital of Heraklion, Crete, Greece, from 2004 to 2009. The MDR isolates were defined according to an international expert proposal supported by the U.S. Centers for Disease Control and Prevention and the European Centre for Disease Prevention and Control.

RESULTS

A total of 1,153 GNB were isolated; 536 (46.5%) were MDR. The most common isolates were Escherichia coli (312 [27.8%]; MDR rate 50.2%), Pseudomonas aeruginosa (298 [25.8%]; MDR rate 39.6%), Acinetobacter baumannii (137 [11.9%]; MDR rate 83.9%), and Klebsiella pneumoniae (112 [9.7%]; MDR rate 44.6%). Most pathogens were isolated from patients hospitalized in the Departments of Surgical Oncology (32.3%), Orthopedic and Trauma Surgery (31.8%), General Surgery (18.1%), and Pediatric Surgery (15.5%). The clinical specimens comprised pus (45.1%), normally sterile fluids (22.5%), urine (16.8%), blood (6.3%), and other body fluids. Most effective in vitro against all MDR pathogens were colistin (83%), meropenem (57%), and imipenem-cilastatin (56%). The MDR P. aeruginosa was susceptible most often to colistin (94%) and aminoglycosides (tobramycin 56%, amikacin 55%), MDR A. baumannii only to colistin (94%), and MDR K. pneumoniae to meropenem (92%) and aminoglycosides (amikacin 76%, gentamicin 74%).

CONCLUSION

In a region with a high prevalence of antibiotic resistance, almost one-half of GNB isolated from surgical patients were MDR. Surgeons may consider these developments to guide empiric antibiotic therapy for infections caused by gram-negative pathogens.