Genotypic and phenotypic characteristics of Candida parapsilosis bloodstream isolates: Health Care Associated Infections in a teaching Hospital in Italy

BACKGROUND

Candidemia is the most common healthcare associated invasive fungal infection. Over the last few decades, candidemia caused by Candida species other than Candida albicans, particularly the Candida parapsilosis complex, has emerged worldwide. The aims of this study were: to analyze the genotypic and phenotypic characteristics of C. parapsilosis strains isolated from blood cultures and the environment in a hospital in southern Italy, to study the possible source of infection and to correlate the isolated strains.

METHODS

From April to October 2022, cases of candidemia due to C. parapsilosis in patients admitted to a hospital in the Apulia region were investigated. However, 119 environmental samples from the intensive care unit were collected for identification of the likely environmental reservoir of infection. Routine antifungal (amphotericin B, anidulafungin, fluconazole) susceptibility was performed on all isolates. Whole genome sequencing was performed to study the genotypic correlation of the isolates. Biofilm biomass and metabolic activity were also quantified for all isolates.

RESULTS

A total of 43 C. parapsilosis isolates were cultured from the bloodstream of each patient in different departments, and seven surface samples were positive for C. parapsilosis. Most of the isolated yeasts (41/50; 85 %) were resistant to fluconazole and were genetically related to each other, suggesting an ongoing clonal outbreak of this pathogen. The fluconazole-susceptible isolates produced significantly more biofilm than did the resistant isolates. Metabolic activity was also higher for fluconazole-susceptible than resistant isolates.

CONCLUSION

Cross-transmission of the microorganisms is suggested by the phenotypic similarity and genetic correlation between clinical and environmental strains observed in our study.

Genetic analysis of vancomycin-variable Enterococcus faecium clinical isolates in Italy

PURPOSE

To investigate the occurrence of vancomycin-variable enterococci (VVE) in a hospital in central Italy.

METHODS

vanA positive but vancomycin-susceptible Enterococcus faecium isolates (VVE-S) were characterized by antibiotic susceptibility tests, molecular typing (PFGE and MLST), and WGS approach. The reversion of VVE-S to a resistant phenotype was assessed by exposure to increasing vancomycin concentrations, and the revertant isolates were used in filter mating experiments. qPCR was used to analyze the plasmid copy number.

RESULTS

Eleven putative VVE-S were selected. WGS revealed two categories of vanA cluster plasmid located: the first type showed the lack of vanR, the deletion of vanS, and an intact vanH/vanA/vanX cluster; the second type was devoid of both vanR and vanS and showed a deletion of 544-bp at the 5'-end of the vanH. Strains (n = 7) carrying the first type of vanA cluster were considered VVE-S and were able to regain a resistance phenotype (VVE-R) in the presence of vancomycin, due to a 44-bp deletion in the promoter region of vanH/vanA/vanX, causing its constitutive expression. VVE-R strains were not able to transfer resistance by conjugation, and the resistance phenotype was unstable: after 11 days of growth without selective pressure, the revertants were still resistant but showed a lower vancomycin MIC. A higher plasmid copy number in the revertant strains was probably related to the resistance phenotype.

CONCLUSION

We highlight the importance of VVE transition to VRE under vancomycin therapy resulting in a potential failure treatment. We also report the first-time identification of VVE-S isolates pstS-null belonging to ST1478.

Human Campylobacter spp. infections in Italy

PURPOSE

Campylobacter is a frequent cause of enteric infections with common antimicrobial resistance issues. The most recent reports of campylobacteriosis in Italy include data from 2013 to 2016. We aimed to provide national epidemiological and microbiological data on human Campylobacter infections in Italy during the period 2017-2021.

METHODS

Data was collected from 19 Hospitals in 13 Italian Regions. Bacterial identification was performed by mass spectrometry. Antibiograms were determined with Etest or Kirby-Bauer (EUCAST criteria).

RESULTS

In total, 5419 isolations of Campylobacter spp. were performed. The most common species were C. jejuni (n = 4535, 83.7%), followed by C. coli (n = 732, 13.5%) and C. fetus (n = 34, 0.6%). The mean age of patients was 34.61 years and 57.1% were males. Outpatients accounted for 54% of the cases detected. Campylobacter were isolated from faeces in 97.3% of cases and in 2.7% from blood. C. fetus was mostly isolated from blood (88.2% of cases). We tested for antimicrobial susceptibility 4627 isolates (85.4%). Resistance to ciprofloxacin and tetracyclines was 75.5% and 54.8%, respectively; resistance to erythromycin was 4.8%; clarithromycin 2% and azithromycin 2%. 50% of C. jejuni and C. coli were resistant to ≥ 2 antibiotics. Over the study period, resistance to ciprofloxacin and tetracyclines significantly decreased (p < 0.005), while resistance to macrolides remained stable.

CONCLUSION

Campylobacter resistance to fluoroquinolones and tetracyclines in Italy is decreasing but is still high, while macrolides retain good activity.

Cefiderocol use for the treatment of infections by carbapenem-resistant Gram-negative bacteria: an Italian multicentre real-life experience

BACKGROUND

Cefiderocol is a novel siderophore cephalosporin with promising activity against most carbapenem-resistant Gram-negative bacteria (CRGNB). However, extensive postmarketing experiences are lacking. This study aimed to analyse the early experience on cefiderocol postmarketing use at three tertiary care hospitals in Italy.

METHODS

We retrospectively included patients with infections caused by CRGNB treated with cefiderocol at three Italian tertiary care hospitals from 1 March 2021 to 30 June 2022. A multivariate Cox model was used to identify predictors of 30 day mortality. A propensity score (PS) analysis with inverse probability weighting (IPW) was also performed to compare the treatment effect of cefiderocol monotherapy (CM) versus combination regimens (CCRs).

RESULTS

The cohort included 142 patients (72% male, median age 67 years, with 89 cases of Acinetobacter baumannii infection, 22 cases of Klebsiella pneumoniae, 27 cases of Pseudomonas aeruginosa and 4 of other pathogens). The 30 day all-cause mortality was 37% (52/142). We found no association between bacterial species and mortality. In multivariate analysis, a Charlson Comorbidity Index >3 was an independent predictor of mortality (HR 5.02, 95% CI 2.37-10.66, P < 0.001). In contrast, polymicrobial infection (HR 0.41, 95% CI 0.21-0.82, P < 0.05) was associated with lower mortality. There was no significant difference in mortality between patients receiving CM (n = 70) and those receiving a CCR (n = 72) (33% versus 40%, respectively), even when adjusted for IPW-PS (HR 1.11, 95% CI 0.63-1.96, P = 0.71).

CONCLUSIONS

Real-life data confirm that cefiderocol is a promising option against carbapenem-resistant Gram-negative infections, even as monotherapy.

Genomic Analysis of a Linezolid-Resistant Staphylococcus capitis Causing Bacteremia: Report from a University Hospital in Central Italy

Although coagulase negative staphylococci are rarely associated with complicated diseases, in some cases they cause life-threatening infections. Here we described a clinical case of a bacteremia due to a methicillin- and linezolid-resistant Staphylococcus capitis in a patient previously treated with linezolid. Whole genome sequencing revealed the common mutation G2576T in all rDNA 23S alleles and several acquired resistance genes. Moreover, the isolate was epidemiologically distant from the NRCS-A clade, usually responsible for nosocomial infections in neonatal intensive care units. Our findings further confirm the ability of minor staphylococci to acquire antibiotic resistances and challenge the treatment of these infections.

Side effects of antibiotics and perturbations of mitochondria functions

Antibiotics are one of the greatest discoveries of medicine of the past century. Despite their invaluable contribution to infectious disease, their administration could lead to side effects that in some cases are serious. The toxicity of some antibiotics is in part due to their interaction with mitochondria: these organelles derive from a bacterial ancestor and possess specific translation machinery that shares similarities with the bacterial counterpart. In other cases, the antibiotics could interfere with mitochondrial functions even if their main bacterial targets are not shared with the eukaryotic cells. The purpose of this review is to summarize the effects of antibiotics administration on mitochondrial homeostasis and the opportunity that some of these molecules could represent in cancer treatment. The importance of antimicrobial therapy is unquestionable, but the identification of interaction with eukaryotic cells and in particular with mitochondria is crucial to reduce the toxicity of these drugs and to explore other useful medical applications.

The Emerging Nosocomial Pathogen Klebsiella michiganensis: Genetic Analysis of a KPC-3 Producing Strain Isolated from Venus Clam

The recovery and characterization of a multidrug-resistant, KPC-3-producing Klebsiella michiganensis that was obtained from Venus clam samples is reported in this study. A whole-genome sequencing (WGS) analysis using Illumina and Nanopore technologies of the K. michiganensis 23999A2 isolate revealed that the strain belonged to the new sequence type 382 (ST382) and carried seven plasmid replicon sequences, including four IncF type plasmids (FII, FIIY, FIIk, and FIB), one IncHI1 plasmid, and two Col plasmids. The FIB and FIIk plasmids showed high homology to each other and to multireplicon pKpQIL-like plasmids that are found in epidemic KPC-K. pneumoniae clones worldwide. The strain carried multiple β-lactamase genes on the IncF plasmids: blaOXA-9 and blaTEM-1A on FIB, blaKPC-3 inserted in a Tn4401a on FIIK, and blaSHV-12 on FIIY. The IncHI1-ST11 harbored no resistance gene. The curing of the strain caused the loss of all of the bla genes and a rearrangement of the IncF plasmids. Conjugal transfer of the blaOXA-9, blaTEM-1A and blaKPC-3 genes occurred at a frequency of 5 × 10-7, using K. quasipneumoniae as a recipient, and all of the bla genes were transferred through a pKpQIL that originated from the recombination of the FIB and FIIk plasmids of the donor. A comparison with 31 K. michiganensis genomes that are available in the NCBI database showed that the closest phylogenetic relatives of K. michiganensis 23999A2 are an environmental isolate from soil in South Korea and a clinical isolate from human sputum in Japan. Finally, a pan-genome analysis showed a large accessory genome of the strain as well as the great genomic plasticity of the K. michiganensis species. IMPORTANCE Klebsiella michiganensis is an emerging nosocomial pathogen, and, so far, few studies describe isolates of clinical origin in the environment. This study contributes to the understanding of how the dissemination of carbapenem-resistance outside the hospital setting may be related to the circulation of pKpQIL-like plasmids that are derived from epidemic Klebsiella pneumoniae strains. The recovery of a carbapenem-resistant isolate in clams is of great concern, as bivalves could represent vehicles of transmission of pathogens and resistance genes to humans via the food chain. The study demonstrates the plasticity of K. michiganensis genome, which is probably useful to multiple environment adaptation and to the evolution of the species.

Detection of an Enterococcus faecium Carrying a Double Copy of the PoxtA Gene from Freshwater River, Italy

Oxazolidinones are valuable antimicrobials that are used to treat severe infections due to multidrug-resistant (MDR) Gram-positive bacteria. However, in recent years, a significant spread of clinically relevant linezolid-resistant human bacteria that is also present in animal and environmental settings has been detected and is a cause for concern. This study aimed to investigate the presence, genetic environments, and transferability of oxazolidinone resistance genes in enterococci from freshwater samples. A total of 10 samples were collected from a river in Central Italy. Florfenicol-resistant enterococci were screened for the presence of oxazolidinone resistance genes by PCR. Enterococcus faecium M1 was positive for the poxtA gene. The poxtA transfer (filter mating and aquaria microcosm assays), localization (S1-PFGE/hybridization), genetic context, and clonality of the isolate (WGS) were analyzed. Two poxtA copies were located on the 30,877-bp pEfM1, showing high-level identity and synteny to the pEfm-Ef3 from an E. faecium collected from an Italian coastal area. The isolate was able to transfer the poxtA to enterococcal recipients both in filter mating and aquaria microcosm assays. This is-to the best of our knowledge-the first detection of an enterococcus carrying a linezolid resistance gene from freshwater in Italy.

Antifungal Combinations against Candida Species: From Bench to Bedside

Candida spp. is the major causative agent of fungal infections in hospitalized patients and the fourth most common cause of nosocomial bloodstream infection (BSI). The availability of standardized methods for testing the in vitro activity of antifungals along with the expanding of antifungal armamentarium, the rising of drug-resistance and the persistence of a high mortality rate in systemic candidiasis have led to an increased interest in combination therapy. Therefore, we aimed to review the scientific literature concerning the antifungal combinations against Candida. A literature search performed in PubMed yielded 92 studies published from 2000 to 2021: 29 articles referring to in vitro studies, six articles referring to either in vitro and in vivo (i.e., animal models) studies and 57 clinical articles. Pre-clinical studies involved 735 isolates of Candida species and 12 unique types of antifungal combination approaches including azoles plus echinocandins (19%), polyenes plus echinocandins (16%), polyenes plus azoles (13%), polyenes plus 5-flucytosine ([5-FC], 13%), azoles plus 5-FC (11%) and other types of combinations (28%). Results varied greatly, often being species-, drug- and methodology-dependent. Some combinatorial regimens exerted a synergistic effect against difficult-to-treat Candida species (i.e., azoles plus echinocandins; polyenes plus 5-FC) or they were more effective than monotherapy in prevent or reducing biofilm formation and in speeding the clearance of infected tissues (i.e., polyenes plus echinocandins). In 283 patients with documented Candida infections (>90% systemic candidiasis/BSI), an antifungal combination approach could be evaluated. Combinations included: azoles plus echinocandins (36%), 5-FC-combination therapies (24%), polyenes plus azoles (18%), polyenes plus echinocandins (16%) and other types of combination therapy (6%). Case reports describing combination therapies yielded favorable response in most cases, including difficult-to-treat fungal infections (i.e., endocarditis, osteoarticular infections, CNS infections) or difficult-to-treat fungal pathogens. The only randomized trial comparing amphotericin-B deoxycholate (AMB) plus FLU vs. AMB alone for treatment of BSI in nonneutropenic patients showed that the combination trended toward improved success and more-rapid clearance from the bloodstream. In summary, antifungal combinations against Candida have produced great interest in the past two decades. To establish whether this approach can become a reliable treatment option, additional in vitro and clinical data are warranted.

Oxazolidinones: mechanisms of resistance and mobile genetic elements involved

The oxazolidinones (linezolid and tedizolid) are last-resort antimicrobial agents used for the treatment of severe infections in humans caused by MDR Gram-positive bacteria. They bind to the peptidyl transferase centre of the bacterial ribosome inhibiting protein synthesis. Even if the majority of Gram-positive bacteria remain susceptible to oxazolidinones, resistant isolates have been reported worldwide. Apart from mutations, affecting mostly the 23S rDNA genes and selected ribosomal proteins, acquisition of resistance genes (cfr and cfr-like, optrA and poxtA), often associated with mobile genetic elements [such as non-conjugative and conjugative plasmids, transposons, integrative and conjugative elements (ICEs), prophages and translocatable units], plays a critical role in oxazolidinone resistance. In this review, we briefly summarize the current knowledge on oxazolidinone resistance mechanisms and provide an overview on the diversity of the mobile genetic elements carrying oxazolidinone resistance genes in Gram-positive and Gram-negative bacteria.

In Vitro Activity of Novel Lipopeptides against Triazole-Resistant Aspergillus fumigatus

Aspergillosis, which is mainly sustained by Aspergillus fumigatus, includes a broad spectrum of diseases. They are usually severe in patients with co-morbidities. The first-line therapy includes triazoles, for which an increasing incidence of drug resistance has been lately described. As a consequence of this, the need for new and alternative antifungal molecules is absolutely necessary. As peptides represent promising antimicrobial molecules, two lipopeptides (C14-NleRR-NH₂, C14-WRR-NH₂) were tested to assess the antifungal activity against azole-resistant A. fumigatus. Antifungal activity was evaluated by determination of minimum inhibitory concentrations (MICs), time–kill curves, XTT assay, optical microscopy, and checkerboard combination with isavuconazole. Both lipopeptides showed antifungal activity, with MICs ranging from 8 mg/L to 16 mg/L, and a dose-dependent effect was confirmed by both time–kill curves and XTT assays. Microscopy showed that hyphae growth was hampered at concentrations equal to or higher than MICs. The rising antifungal resistance highlights the usefulness of novel compounds to treat severe fungal infections. Although further studies assessing the activity of lipopeptides are necessary, these molecules could be effective antifungal alternatives that overcome the current resistances.

Clinical and microbiological features of ceftolozane/tazobactam resistant Pseudomonas aeruginosa isolates in a university hospital in central Italy

OBJECTIVES

Ceftolozane/tazobactam (C/T) is a novel cephalosporin and β-lactamase inhibitor combination with great activity against Pseudomonas aeruginosa. To assess the Pseudomonas aeruginosa susceptibility to C/T, a surveillance study was conducted from October 2018 to March 2019 at the University Hospital "Ospedali Riuniti" of Ancona (Italy).

MATERIALS AND METHODS

MICs to C/T were determined by Etest strip. Resistant isolates were characterized by phenotypic (broth microdilution antimicrobial susceptibility testing and mCIM) and genotypic (PCR, PFGE and WGS) methods. Clinical variables of patients infected by C/T resistant P. aeruginosa were collected from medical records.

RESULTS

fifteen out of 317 P. aeruginosa collected showed resistance to C/T (4.7%). Ten strains demonstrated a carbapenemase activity by mCIM method, and PCR confirmed eight of them harbored a bla_VIM gene, while the other two were positive for bla_IMP. Additionally, three isolates carried acquired extended spectrum β-lactamase genes (2 bla_PER and 1 bla_GES). Eight strains were strictly related by PFGE and WGS analysis confirmed that they belonged to ST111. The other STs found were ST175 (2 isolates), ST235 (2 isolates), ST70 (1 isolate), ST621 (1 isolate) and the new ST3354 (1 isolate). Most of the patients received previous antibiotic therapies, carried invasive devices and had a prolonged hospitalization.

CONCLUSION

This study demonstrated the presence of C/T resistant P. aeruginosa isolates also in a regional hospital, carrying a number of resistance mechanisms acquired by different high-risk clones.

Anaerobic bloodstream infections in Italy (ITANAEROBY): A 5-year retrospective nationwide survey

INTRODUCTION

A lack of updated data on the burden and profile of anaerobic bloodstream infections (ABIs) exists. We assessed the incidence of ABIs and trends in antimicrobial resistance in anaerobes isolated from blood in Italy.

MATERIAL AND METHODS

We conducted a retrospective study on 17 Italian hospitals (2016-2020). Anaerobes isolated from blood culture and their in vitro susceptibility profiles (EUCAST-interpreted) were registered and analyzed.

RESULTS

A total of 1960 ABIs were identified. The mean age of ABIs patients was 68.6 ± 18.5 years, 57.6% were males. The overall incidence rate of ABIs was 1.01 per 10.000 patient-days. Forty-seven% of ABIs occurred in medical wards, 17% in ICUs, 14% in surgical wards, 7% in hemato-oncology, 14% in outpatients. The three most common anti-anaerobic tested drugs were metronidazole (92%), clindamycin (89%) and amoxicillin/clavulanate (83%). The three most common isolated anaerobes were Bacteroides fragilis (n = 529), Cutibacterium acnes (n = 262) and Clostridium perfringens (n = 134). The lowest resistance rate (1.5%) was to carbapenems, whereas the highest rate (51%) was to penicillin. Clindamycin resistance was >20% for Bacteroides spp., Prevotella spp. and Clostridium spp. Metronidazole resistance was 9.2% after excluding C. acnes and Actinomyces spp. Bacteroides spp. showed an increased prevalence of clindamycin resistance through the study period: 19% in 2016, 33% in 2020 (p ≤ 0.001).

CONCLUSIONS

Our data provide a comprehensive overview of the epidemiology of ABIs in Italy, filling a gap that has existed since 1995. Caution is needed when clindamycin is used as empirical anti-anaerobic drug.

Correction: Morroni et al. Antimicrobial Activity of Aztreonam in Combination with Old and New β-Lactamase Inhibitors against MBL and ESBL Co-Producing Gram-Negative Clinical Isolates: Possible Options for the Treatment of Complicated Infections. Antibiotics 2021, 10, 1341

Results have been implemented with additional data, which have been commented in the following paragraphs [...]

Candidemia in Internal Medicine: Facing the New Challenge

Candidemia is an alarming problem in critically ill patients including those admitted in Internal Medicine Wards (IMWs). Here, we analyzed all cases of candidemia in adult patients hospitalized over nine years (2010–2018) in IMWs of a 980-bedded University Hospital of Ancona, Italy. During the study period, 218/505 (43%) episodes of candidemia occurred in IMWs patients. The cumulative incidence was 2.5/1000 hospital admission and increased significantly over time (p = 0.013). Patients were predominantly male, with a median age of 68 years. Cardiovascular diseases and solid tumors were the most frequent comorbidities. Candida albicans accounted for 51% of the cases, followed by C. parapsilosis (25%), C. tropicalis (9%) and C. glabrata (7%). Thirty-day mortality was 28% and did not increased significantly over time. By multivariate logistic regression analysis, the presence of neutropenia (OR 7.247 [CI95% 1,368–38,400; p = 0.020]), pneumonia (OR 2.323 [CI95% 1,105–4,884; p = 0.026]), and being infected with C. albicans (OR 2.642 [95% CI 1,223–5,708; p = 0.013) emerged as independent predictors of mortality. The type of antifungal therapy did not influence the outcome. Overall, these data indicate that patients admitted to IMWs are increasingly at higher risk of developing candidemia. Mortality rate remains high and significantly associated with both microbiologic- and host-related factors.

Linezolid-resistant Enterococcus gallinarum isolate of swine origin carrying cfr, optrA and poxtA genes

OBJECTIVES

To characterize a linezolid-resistant Enterococcus gallinarum isolate of porcine origin co-carrying cfr, optrA and poxtA genes.

METHODS

The genome was sequenced using the Illumina and Nanopore platforms. The presence of circular intermediates was examined by inverse PCR. Transferability of oxazolidinone resistance genes was investigated by transformation and conjugation.

RESULTS

Two plasmids, the cfr- and optrA-carrying pEgFS4-1 (35 kb) and the poxtA-harbouring pEgFS4-2 (38 kb), were identified. pEgFS4-1 disclosed a distinctive mosaic structure with two cargo regions bounded by identical IS1216 elements interpolated into a backbone related to that of Enterococcus faecium vanA-containing pVEF2. The first cargo region included the cfr and optrA contexts, whereas the second one carried a Tn554 remnant and the lnu(A) gene. Both regions were able to excise in circular form as a unique translocable unit. pEgFS4-2 plasmid was 99% identical to a not fully described E. faecium pSBC1 plasmid. The poxtA environment, flanked by IS1216, was proved to be unstable. pEgFS4-2 also exhibited another cargo region containing the tet(M)-tet(L) genes arranged in tandem and its circular form was detected. Transformation and conjugation experiments failed to demonstrate the transferability of both plasmids to enterococcal recipients. Both plasmids persisted in the absence of selective pressure.

CONCLUSIONS

To the best of our knowledge, this is the first description of a linezolid-resistant E. gallinarum isolate of swine origin carrying cfr, optrA and poxtA genes. The co-presence of three linezolid resistance determinants in an intrinsically vancomycin-resistant enterococcal species is cause of concern.

New insight into old and new antimicrobial molecules targeting quorum sensing for MRSA wound infection

MRSA represents one of the largest problems in wound healing as a result of its increasing incidence and the complex therapeutic approach required to treat it. The need for new solutions to overcome antibiotic resistance led to the development of antimicrobial molecules that are effective at blocking quorum sensing. This special report provides an up-to-date review, based on the latest evidence in the literature, of old and new molecules that can positively influence the process of wound healing via their action on MRSA quorum sensing. Quorum sensing-inhibiting molecules, applied topically or injected in situ, have excellent potential to improve both MRSA eradication and quality of wound healing, especially when combined with conventional systemic MRSA therapy. Further human studies are needed to evaluate the efficacy of these molecules.

Candidemia: Evolution of Drug Resistance and Novel Therapeutic Approaches

Candidemia and invasive candidiasis are the most common healthcare-associated invasive fungal infections, with a crude mortality rate of 25–50%. Candida albicans remains the most frequent etiology, followed by C. glabrata, C. parapsilosis and C. tropicalis. With the exception of a limited number of species (ie: C. krusei, C. glabrata and rare Candida species), resistance to fluconazole and other triazoles are quite uncommon. However, recently fluconazole-resistant C. parapsilosis, echinocandin-resistant C. glabrata and the multidrug resistant C. auris have emerged. Resistance to amphotericin B is even more rare due to the reduced fitness of resistant isolates. The mechanisms of antifungal resistance in Candida (altered drug-target interactions, reduced cellular drug concentrations, and physical barriers associated with biofilms) are analyzed. The choice of the antifungal therapy for candidemia must take into account several factors such as type of patient, presence of devices, severity of illness, recent exposure to antifungals, local epidemiology, organs involvement, and Candida species. The first-line therapy in non-neutropenic critical patient is an echinocandin switching to fluconazole in clinically stable patients with negative blood cultures and azole susceptible isolate. Similarly, an echinocandin is the drug of choice also in neutropenic patients. The treatment duration is 14 days after the first negative blood culture or longer in cases of organ involvement. An early removal of vascular catheter improves the outcome. The promising results of new antifungal molecules, such as the terpenoid derivative ibrexafungerp, the novel echinocandin with an enhanced half-life rezafungin, oteseconazole and fosmanogepix, representative of new classes of antifungals, are discussed.

Occurrence of a plasmid co-carrying cfr(D) and poxtA2 linezolid resistance genes in Enterococcus faecalis and Enterococcus casseliflavus from porcine manure, Italy

OBJECTIVES

To investigate the genetic elements and the transferability of linezolid resistance genes in three enterococci co-carrying cfr(D) and poxtA2 isolates from manure of a swine farm in central Italy.

METHODS

Two Enterococcus faecalis isolates and one Enterococcus casseliflavus isolate carrying both cfr(D) and poxtA genes were tested for their susceptibility to florfenicol, chloramphenicol, linezolid, tedizolid, tetracycline and vancomycin. Linezolid resistance genes transfer (filter mating), localization (S1-PFGE/hybridization), genetic elements and relatedness between isolates (WGS) were analysed.

RESULTS

Two E. faecalis isolates and one E. casseliflavus isolate carried the cfr(D) gene and the recently described poxtA2 variant. In the three enterococci, cfr(D) and poxtA2 were co-located on a 33 480 bp plasmid, pV386, 95%-100% identical (coverage 84%) to the Tn6349 transposon of Staphylococcus aureus AOUC-0915. In all isolates, both genes also showed a chromosomal location. Same sequence identities were found from the comparison with currently known poxtA2 genetic elements. In the plasmid pV386, poxtA2 gene was not bounded by two IS1216, as described in pIB-BOL, but closely associated to the cfr(D) and fexA genes. pV386 was always transferred by filter mating to Enterococcus faecium 64/3 recipient.

CONCLUSIONS

The occurrence of the pV386 plasmid in E. faecalis and E. casseliflavus from swine manure is of great concern and highlights the need for control measures to contain its spread to other enterococcal species.

Antimicrobial Activity of Aztreonam in Combination with Old and New β-Lactamase Inhibitors against MBL and ESBL Co-Producing Gram-Negative Clinical Isolates: Possible Options for the Treatment of Complicated Infections

Metallo-β-lactamases (MBLs) are among the most challenging bacterial enzymes to overcome. Aztreonam (ATM) is the only β-lactam not hydrolyzed by MBLs but is often inactivated by co-produced extended-spectrum β-lactamases (ESBL). We assessed the activity of the combination of ATM with old and new β-lactamases inhibitors (BLIs) against MBL and ESBL co-producing Gram-negative clinical isolates. Six Enterobacterales and three non-fermenting bacilli co-producing MBL and ESBL determinants were selected as difficult-to-treat pathogens. ESBLs and MBLs genes were characterized by PCR and sequencing. The activity of ATM in combination with seven different BLIs (clavulanate, sulbactam, tazobactam, vaborbactam, avibactam, relebactam, zidebactam) was assessed by microdilution assay and time–kill curve. ATM plus avibactam was the most effective combination, able to restore ATM susceptibility in four out of nine tested isolates, reaching in some cases a 128-fold reduction of the MIC of ATM. In addition, relebactam and zidebactam showed to be effective, but with lesser reduction of the MIC of ATM. E. meningoseptica and C. indologenes were not inhibited by any ATM–BLI combination. ATM–BLI combinations demonstrated to be promising against MBL and ESBL co-producers, hence providing multiple options for treatment of related infections. However, no effective combination was found for some non-fermentative bacilli, suggesting the presence of additional resistance mechanisms that complicate the choice of an active therapy.

Control of host mitochondria by bacterial pathogens

Mitochondria control various processes that are integral to cellular and organismal homeostasis, including Ca²⁺ fluxes, bioenergetic metabolism, and cell death. Perhaps not surprisingly, multiple pathogenic bacteria have evolved strategies to subvert mitochondrial functions in support of their survival and dissemination. Here, we discuss nonimmunological pathogenic mechanisms that converge on the ability of bacteria to control the mitochondrial compartment of host cells.

Use of Dalbavancin in Skin, Bone and Joint Infections: A Real-Life Experience in an Italian Center

Dalbavancin is a lipoglycopeptide approved for the treatment of acute bacterial skin and skin structure infections (ABSSSI). The aim of the study was to evaluate the efficacy and safety in all patients who received at least one administration of dalbavancin.

METHODS

We carried out a retrospective study of the use of dalbavancin in 55 patients at the Azienda Ospedaliera Ospedali Riuniti Umberto I (Ancona, Italy) from February 2017 to May 2020 and compared "on label" and "off label" use of dalbavancin in ABSSSI and non-ABSSSI.

RESULTS

A total of 55 patients were included in the study. The median age was 61 years; 51% had ABSSSI; 24% had prosthetic joint infections, and 14% had osteomyelitis. A total of 53% received a single 1500 mg infusion of dalbavancin, and 18% received a second dose 14 days later; 24% of patients received further doses at 14-day intervals. In 91% of cases, patients achieved clinical objectives with dalbavancin: 96% of patients with ABSSSI and 69% of those with prosthetic joint infections.

CONCLUSIONS

Dalbavancin was shown to have an excellent tolerability profile and to be a highly successful therapeutic approach even in those cases treated "off-label".

Antifungal Combinations in Dermatophytes

Dermatophytes are the most common cause of fungal infections worldwide, affecting millions of people annually. The emergence of resistance among dermatophytes along with the availability of antifungal susceptibility procedures suitable for testing antifungal agents against this group of fungi make the combinatorial approach particularly interesting to be investigated. Therefore, we reviewed the scientific literature concerning the antifungal combinations against dermatophytes. A literature search on the subject performed in PubMed yielded 68 publications: 37 articles referring to in vitro studies and 31 articles referring to case reports or clinical studies. In vitro studies involved over 400 clinical isolates of dermatophytes (69% Trichophyton spp., 29% Microsporum spp., and 2% Epidermophyton floccosum). Combinations included two antifungal agents or an antifungal agent plus another chemical compound including plant extracts or essential oils, calcineurin inhibitors, peptides, disinfectant agents, and others. In general, drug combinations yielded variable results spanning from synergism to indifference. Antagonism was rarely seen. In over 700 patients with documented dermatophyte infections, an antifungal combination approach could be evaluated. The most frequent combination included a systemic antifungal agent administered orally (i.e., terbinafine, griseofulvin, or azole-mainly itraconazole) plus a topical medication (i.e., azole, terbinafine, ciclopirox, amorolfine) for several weeks. Clinical results indicate that association of antifungal agents is effective, and it might be useful to accelerate the clinical and microbiological healing of a superficial infection. Antifungal combinations in dermatophytes have gained considerable scientific interest over the years and, in consideration of the interesting results available so far, it is desirable to continue the research in this field.

Characterization and Clonal Diffusion of Ceftaroline Non-Susceptible MRSA in Two Hospitals in Central Italy

Background: Ceftaroline represents a novel fifth-generation cephalosporin to treat infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Methods: Ceftaroline susceptibility of 239 MRSA isolates was assessed by disk diffusion and a MIC test strip following both EUCAST and CLSI guidelines. Non-susceptible isolates were epidemiologically characterized by pulsed-field gel electrophoresis, spa typing, and multilocus sequence typing, and further investigated by PCR and whole genome sequencing to detect penicillin-binding protein (PBP) mutations as well as antibiotic resistance and virulence genes. Results: Fourteen isolates out of two hundred and thirty-nine (5.8%) were non-susceptible to ceftaroline (MIC > 1 mg/L), with differences between the EUCAST and CLSI interpretations. The characterized isolates belonged to seven different pulsotypes and three different clones (ST228/CC5-t041-SCCmecI, ST22/CC22-t18014-SCCmecIV, and ST22/CC22-t022-SCCmecIV), confirming a clonal diffusion of ceftaroline non-susceptible strains. Mutations in PBPs involved PBP2a for ST228-t041-SCCmecI strains and all the other PBPs for ST22-t18014-SCCmecIV and ST22-t022-SCCmecIV clones. All isolates harbored antibiotic resistance and virulence genes with a clonal distribution. Conclusion: Our study demonstrated that ceftaroline non-susceptibile isolates belonged not only to ST228 strains (the most widespread clone in Italy) but also to ST22, confirming the increasing role of these clones in hospital infections.

High prevalence of carbapenem-resistant Klebsiella pneumoniae ST307 recovered from fecal samples in an Italian hospital

Aim: This study reports the characterization of carbapenem-resistant colonizing strains of K. pneumoniae. Methods: 650 stool samples were screened for carbapenem-resistant K. pneumoniae (CR-Kp). All strains were characterized for antibiotic susceptibility, typing features, main carbapenemases and extended-spectrum ß-lactamases. The carbapenemase transferability was assessed by interspecific conjugation. Results: Eighteen CR-Kp were multidrug resistant, five were KPC producing. A predominance of ST307 isolates, constituting the predominant cluster by PFGE analysis, was identified (50% were KPC-2 producers). Conjugation data showed the co-transfer of blaKPC-2, blaTEM-1, blaOXA-1, blaCTX-M-15 in a single large pKPN3-like plasmid. Conclusion: Our data pointed out the diversity of colonizing K. pneumoniae strains compared with clinical ones. The predominance of ST307 strains suggested an increased spreading, even in our area, of this high-risk clone.

Candidemia in intensive care units over nine years at a large Italian university hospital: Comparison with other wards

Purpose

Candidemia is an alarming problem in critically ill patients including those admitted in intensive care units (ICUs). We aimed to describe the clinical and microbiological characteristics of bloodstream infections (BSIs) due to Candida spp. in patients admitted to ICUs of an italian tertiary referral university hospital over nine years.

Methods

A retrospective observational study of all cases of candidemia in adult patients was carried out from January 1, 2010 to December 31, 2018 at a 980-bedded University Hospital in Ancona, Italy, counting five ICUs. The incidence, demographics, clinical and microbiologic characteristics, therapeutic approaches and outcomes of ICU-patients with candidemia were collected. Non-ICU patients with candidemia hospitalized during the same time period were considered for comparison purposes. Early (7 days from the occurrence of the episode of Candida BSI) and late (30 days) mortality rates were calculated.

Results

During the study period, 188/505 (36%) episodes of candidemia occurred in ICU patients. Cumulative incidence was 9.9/1000 ICU admission and it showed to be stable over time. Candida albicans accounted for 52% of the cases, followed by C. parapsilosis (24%), and C. glabrata (14%). There was not a significant difference in species distribution between ICU and non-ICU patients. With the exception of isolates of C. tropicalis which showed to be fluconazole resistant in 25% of the cases, resistance to antifungals was not of concern in our patients. Early and late mortality rates, were 19% and 41% respectively, the latter being significantly higher than that observed in non-ICU patients. At multivariate analysis, factors associated with increased risk of death were septic shock, acute kidney failure, pulmonary embolism and lack of antifungal therapy. The type of antifungal therapy did not influence the outcome. Mortality did not increased significantly over time.

Conclusion

Neither cumulative incidence nor crude mortality of candidemia in ICU patients increased over time at our institution. However, mortality rate remained high and significantly associated with specific host-related factors in the majority of cases.

Synergistic effect of antimicrobial peptide LL-37 and colistin combination against multidrug-resistant Escherichia coli isolates

Overview: The global spread of antibiotic resistance represents a serious threat for public health. Aim: We evaluated the efficacy of the antimicrobial peptide LL-37 as antimicrobial agent against multidrug-resistant Escherichia coli. Results: LL-37 showed good activity against mcr-1 carrying, extended spectrum β-lactamase- and carbapenemase-producing E. coli (minimum inhibitory concentration, MIC, from 16 to 64 mg/l). Checkerboard assays demonstrated synergistic effect of LL-37/colistin combination against all tested strains, further confirmed by time-kill and post antibiotic effect assays. MIC and sub-MIC concentrations of LL-37 were able to reduce biofilm formation. Conclusion: Our preliminary data indicated that LL-37/colistin combination was effective against multidrug-resistant E. coli strains and suggested a new possible clinical application.

Human leptospirosis in the Marche region: Over 10 years of surveillance

We conducted a 10 years' retrospective study in 347 symptomatic individuals to assess the regional distribution of leptospirosis. A total of 173 individuals were diagnosed positive (49.8%): 11.5% were found positive to Leptospira by microscopic agglutination test positive, whereas 38.3% were found positive by microscopy analysis. The maximum peak of leptospirosis was reached in 2017 (n = 32). The most common serovars were Icterohaemorrhagiae and Poi.

Detection of Oxazolidinone Resistance Genes and Characterization of Genetic Environments in Enterococci of Swine Origin, Italy

One hundred forty-five florfenicol-resistant enterococci, isolated from swine fecal samples collected from 76 pig farms, were investigated for the presence of optrA, cfr, and poxtA genes by PCR. Thirty florfenicol-resistant Enterococcus isolates had at least one linezolid resistance gene. optrA was found to be the most widespread linezolid resistance gene (23/30), while cfr and poxtA were detected in 6/30 and 7/30 enterococcal isolates, respectively. WGS analysis also showed the presence of the cfr(D) gene in Enterococcus faecalis (n = 2 isolates) and in Enterococcus avium (n = 1 isolate). The linezolid resistance genes hybridized both on chromosome and plasmids ranging from ~25 to ~240 kb. Twelve isolates were able to transfer linezolid resistance genes to enterococci recipient. WGS analysis displayed a great variability of optrA genetic contexts identical or related to transposons (Tn6628 and Tn6674), plasmids (pE035 and pWo27-9), and chromosomal regions. cfr environments showed identities with Tn6644-like transposon and a region from p12-2300 plasmid; cfr(D) genetic contexts were related to the corresponding region of the plasmid 4 of Enterococcus faecium E8014; poxtA was always found on Tn6657. Circular forms were obtained only for optrA- and poxtA-carrying genetic contexts. Clonality analysis revealed the presence of E. faecalis (ST16, ST27, ST476, and ST585) and E. faecium (ST21) clones previously isolated from humans. These results demonstrate a dissemination of linezolid resistance genes in enterococci of swine origin in Central Italy and confirm the spread of linezolid resistance in animal settings.

Trend of clinical vancomycin-resistant enterococci isolated in a regional Italian hospital from 2001 to 2018

A retrospective study of the epidemiology of vancomycin-resistant enterococci (VRE) in a regional hospital of central Italy in 2001-2018 demonstrated an increased VRE prevalence since 2016. A total of 113 VRE isolates, 89 E. faecium (VREfm) and 24 E. faecalis (VREfs), were collected in the study period. All strains showed high-level resistance to vancomycin; 107 also showed teicoplanin resistance. Altogether, 84 VREfm and 20 VREfs carried vanA, whereas 5 VREfm and 1 VREfs carried vanB. MLST analysis documented that 89 VREfm isolates mainly belonged to ST78, ST80, and ST117. Most strains were isolated from 2001 to 2007, ST78 being the predominant clone. VREfm re-emerged in 2016 with a prevalence of the ST80 lineage. Most VREfs were isolated from 2001 to 2006; although they belonged to 7 different STs, there was a prevalence of ST88 and ST6. Notably, ST88 was sporadically recovered throughout the study period. The increasing rate of VREfm isolation from 2016 to 2018 may be related to the influx of new successful clones and to the renewed and widespread use of vancomycin. Improved infection control measures in hospital wards should be adopted to limit the spread of new epidemic VRE strains.

Characterization of Tn6349, a novel mosaic transposon carrying poxtA, cfr and other resistance determinants, inserted in the chromosome of an ST5-MRSA-II strain of clinical origin

OBJECTIVES

To characterize the genetic element carrying the poxtA oxazolidinone resistance gene found in the poxtA index strain Staphylococcus aureus AOUC-0915 isolated from a cystic fibrosis patient.

METHODS

The genetic context of poxtA was investigated by bioinformatics analysis of WGS data of strain AOUC-0915, followed by PCR and confirmatory Sanger sequencing for repetitive regions. Conjugation and electrotransformation experiments were carried out to assess horizontal transferability using S. aureus and Enterococcus faecalis recipients. Production of phage particles was evaluated by PCR using DNA preparations obtained after phage induction. Excision of the transposon carrying poxtA was evaluated by inverse PCR experiments for detection of circular intermediates.

RESULTS

poxtA was found to be associated with a 48 kb composite transposon of original structure, named Tn6349, inserted into a φN315-like prophage. The transposon was bounded by two IS1216 insertion sequences, carried several resistance genes [erm(B), cfr, poxtA and fexB] and exhibited a mosaic structure made by a derivative of plasmid pE35048-oc (previously described in an Enterococcus faecium clinical isolate) and Tn6657, a novel composite transposon carrying the poxtA and fexB genes. Excision ability of Tn6349 as a circular intermediate was demonstrated. Transferability of Tn6349 or modules thereof to S. aureus or E. faecalis by either conjugation or electrotransformation was not detected. Induction of the φN315-like prophage carrying Tn6349 was not observed.

CONCLUSIONS

This study describes the structure of Tn6349, a novel composite transposon carrying several resistance determinants to anti-ribosomal drugs, including cfr and poxtA, from an oxazolidinone-resistant MRSA strain. Analysis of Tn6349 revealed a modular structure that could favour the mobilization of its resistance determinants.

Species distribution and antifungal susceptibilities of bloodstream Candida isolates: a nine-years single center survey

This study analyzed the epidemiology of bloodstream infections due to Candida spp. in a tertiary referral hospital of Ancona, Italy, and their susceptibility to antifungals. The retrospective observational study from January 2010 to December 2018 identified 504 episodes of candidemia in 461 patients. Although Candida albicans remained the species most frequently isolated, Candida spp. other than C. albicans caused 49% of the overall episodes of candidemia. According to CLSI interpretation, most of the isolates resulted susceptible to antifungals. Azoles vs Candida tropicalis represented an exception. Echinocandin non-susceptibility was rare across the species. In conclusion, with the exception of C. tropicalis, the isolation of a non-susceptible Candida strains against azoles, echinocandins and amphotericin B was a rare event.

Zinc Chelators as Carbapenem Adjuvants for Metallo-β-Lactamase-Producing Bacteria: In Vitro and In Vivo Evaluation

Infections caused by metallo-β-lactamase (MBL)-producing bacteria are emerging and carry a significant impact on patients' outcome. MBL producers are spread worldwide, both in community and hospital setting, with increasingly reported epidemic clusters and the search for MBL inhibitors is an important topic for public health. MBLs are zinc-dependent enzymes whose functioning can be hampered by zinc chelators. We evaluated the potential of six zinc chelators (disulfiram, nitroxoline, 5-amino-8-hydroxyquinoline, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid [DOTA], cyclam, and N,N,N',N'-tetrakis (2-pyridymethyl) ethylenediamine [TPEN]) in restoring carbapenem activity against MBL producers. Zinc chelators alone or in combination with meropenem against MBL-producing Klebsiella pneumoniae, Chryseobacterium indologenes, Elizabethkingia meningoseptica, and Stenotrophomonas maltophilia isolates were tested in vitro and in vivo (Galleria mellonella). In vitro experiments showed a synergistic activity between TPEN and meropenem toward all the strains. Nitroxoline alone retained activity against S. maltophilia, C. indologenes, and E. meningoseptica. In vivo experiments showed that TPEN or nitroxoline in combination with meropenem increased survival in larvae infected with E. meningoseptica, S. maltophilia, and K. pneumoniae. Based on our data, zinc chelators are potential carbapenem adjuvants molecules (restoring carbapenem activity) against MBL-sustained infections and could represent an interesting option for infections induced by these microorganisms.

Viscoelastic behaviour of hyaluronic acid formulations containing carvacrol prodrugs with antibacterial properties

In this paper, we report the development and viscoelastic properties of hyaluronic acid formulations (HA₅, HA₃₀, and HA₆₀, containing 0.5, 3, and 6% HA, respectively) loaded with carvacrol prodrugs (WSCP_S) with antibacterial properties. Notably, antimicrobial studies revealed that WSCP1-2 in both HA₅ and HA₃₀ formulations showed the best minimum inhibitory concentration (MIC) values against Enterococcus faecium (128 mg/L) and Enterococcus faecalis (256 mg/L) compared to those of carvacrol alone or in formulations with HA. Moreover, rheological analyses showed that HA₃₀ composites exhibited a semi-solid consistency, while HA₅ formulations possessed a fluid consistency. Considering these data, HA₃₀ is a useful formulation which guarantees a good percentage of prodrug release (e.g., 30 and 60% for WSCP1 and 2, respectively) as well as a texture suitable for topical administration to treat wounds and/or skin infections.

Synergistic combinations of antimicrobial peptides against biofilms of methicillin-resistant Staphylococcus aureus (MRSA) on polystyrene and medical devices

OBJECTIVES

Antimicrobial research is being focused to look for more effective therapeutics against antibiotic-resistant infections such as those caused by methicillin-resistant Staphylococcus aureus (MRSA). In this regard, antimicrobial peptides (AMPs) appear to be a promising solution. The aim of the present study was to investigate the potential activity of temporin A, citropin 1.1, CA(1-7)M(2-9)NH₂ and Pal-KGK-NH₂ in synergistic activity against MRSA biofilms developed on polystyrene surface (PSS) and central venous catheter (CVC).

METHODS

The study was subdivided into distinct phases to assess the ability of AMPs to inhibit biofilm formation, to identify possible synergy between AMPs, and to eradicate preformed biofilms on PSS and CVC using AMPs alone or in combination.

RESULTS

Activity of the AMPs was particularly evident in the inhibition of biofilm formation on PSS and CVC, whilst the eradication of preformed biofilms was more difficult and was reached only after 24h of contact. The synergistic activity of AMP combinations, selected by their fractional inhibitory concentration index (FICI), led to an improvement in the performance of all of the molecules in the removal of different biofilms.

CONCLUSION

Overall, AMPs could represent the next generation of antimicrobial agents for a prophylactic or therapeutic tool to control biofilms of antibiotic-resistant bacteria and/or biofilm-associated infections on different medical devices.

Characterisation of candidemia in patients with recent surgery: A 7-year experience

Candidemia can complicate major surgical procedures. However, literature data are scanty on this topic. In this study, we evaluated the epidemiology, clinical and microbiologic characteristics and outcome of candidemia in adult patients with recent surgery hospitalised in a single University Hospital in Central Italy from 2010 to 2016. Of the 304 episodes of candidemia, 160 (53%) occurred in surgical patients (SPs) while the remaining 144 (47%) in patients without history of recent surgery (non-SPs). Although either underlying chronic comorbidities (ie haematological malignancies, neurological and gastrointestinal diseases) or acute complications (ie pneumonia and septic shock) were less likely to occur in SPs than in non-SPs, 30-day mortality did not differ between groups being 38% and 42%, respectively. The specific risk factors significantly more common in SPs who died within 30 days were as follows: male gender, older age, being hospitalised in ICU rather than in other wards, having a higher Charlson's score, undergoing previous invasive procedures, haemodialysis, the presence of pneumonia, septic shock, acute kidney failure and the type of surgery. In particular, either gastrointestinal or cardiovascular surgeries were characterised by the highest mortality rates. Multivariate analysis showed that the occurrence of septic shock (HR 10.3131 [CI95% 1.176-90.466; P = .035] and ICU stay (HR 2.016 [CI95% 1.178-3.448; P = .011] was independently associated with higher mortality in SPs. Overall, these data show that candidemia in SPs is characterised by significant mortality and distinctive features.

Increase and diversity of carbapenemase-producing Escherichia coli isolates, Italy

Aim: This study reports on a surveillance in an Italian hospital focused on carbapenemase-producing Escherichia coli (CP-Ec). Materials & methods: Eighteen isolates (nine from clinical specimens and nine from rectal swab) were characterized for antibiotic susceptibilities, typing features, main carbapenemase, extended-spectrum ß-lactamases (ESBLs) and other bla genes, and their transferability by conjugation and transformation. Results: An increase in CP-Ec isolates was observed during 3-year surveillance period. Compared with the clinical isolates, all belonging to one sequence type (ST), ST131, those from rectal swab were very heterogeneous and belonged to eight STs. Transfer data confirmed the role of conjugative plasmids in the spreading of carbapenemase genes. Conclusion: The prevalence of CP-Ec in Italy has risen, with a substantial increase over the last year.

Clinical and epidemiological characteristics of KPC-producing Klebsiella pneumoniae from bloodstream infections in a tertiary referral center in Italy

Background

Bloodstream infections (BSI) due to Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-Kp) have become an important problem and they are associated with a high mortality rate. The aim of our study was to evaluate the clinical and epidemiological characteristics of KPC-Kp from BSIs.

Methods

In this retrospective cohort study, conducted in a tertiary referral center in Italy, 112 patients with KPC-Kp BSIs diagnosed between February 2011 and December 2015 were identified. We evaluated the mortality at 30 days from the first positive blood culture. Survivor and non-survivor subgroups were compared to identify predictors of mortality.

Results

The overall crude mortality was 35%. APACHE II score ≥ 15, septic shock at BSI onset, immunosuppressive therapy during the 30 days before the BSI onset, and the lack of a combination therapy with at least 2 active drugs emerged as independent predictors of mortality. Excluding patients with inadequate therapy, the mortality decreased to 25% while an APACHE II score ≥ 15 and the presence of septic shock remained independently associated with a negative outcome.

Two different pulsotypes were identified: pulsotype A belonged to ST512 and carried KPC-3 and pulsotype B belonged to ST307 and carried KPC-2.

Conclusions

This study confirmed a high mortality rate of KPC-Kp BSIs. The outcome is heavily influenced by the patient’s clinical conditions. A therapeutic approach including a combination with at least two active drugs in vitro can improve the prognosis, unless patients received an appropriate therapy.

In vitro activity of Protegrin-1, alone and in combination with clinically useful antibiotics, against Acinetobacter baumannii strains isolated from surgical wounds

In the past few years the increasing incidence of hospital infections with Acinetobacter baumannii, especially in immunocompromised patients, and its proneness to develop multidrug resistance have been raising considerable concern. This study examines the antimicrobial and antibiofilm activity of protegrin 1 (PG-1), an antimicrobial peptide from porcine leukocytes, against A. baumannii strains isolated from surgical wounds. PG-1 was tested both alone and combined with the antibiotics commonly used in clinical settings. Its antimicrobial activity was evaluated by determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), checkerboard assays, and time-kill experiments. Its effects on biofilm inhibition/eradication were tested with crystal violet staining. The strains were grown in subinhibitory or increasing PG-1 concentrations to test the development of resistance. Mammalian cell toxicity was tested by XTT assays. PG-1 MICs and MBCs ranged from 2 to 8 µg/ml. PG-1 was most active and demonstrated a synergistic interaction with colistin, a last resort antibiotic. Interestingly, antagonism was never observed. In time-kill experiments, incubation with 2 × MIC for 30 min suppressed all viable cells. PG-1 did not select resistant strains and showed a limited effect on cell viability, but it did exert a strong activity against multidrug-resistant A. baumannii. In contrast, in our experimental conditions it had no effect on biofilm inhibition/eradication. PG-1 thus seems to be a promising antimicrobial agent against multidrug-resistant Gram-negative infections.

Antimicrobial Activity of Different Antimicrobial Peptides (AMPs) Against Clinical Methicillin-resistant Staphylococcus aureus (MRSA)

BACKGROUND

Antimicrobial research is being focused to look for more effective therapeutics against antibiotic-resistant infections caused by methicillin-resistant Staphylococcus aureus (MRSA). In this direction, antimicrobial peptides (AMP) appear as promising tool.

OBJECTIVES

This study evaluated the antimicrobial activity of different AMPs (Citropin 1.1, Temporin A, Pexiganan, CA(1-7)M(2-9)NH2, Pal-KGK-NH2, Pal-KKKK-NH2, LL-37) against human MRSA clinical isolates.

METHODS

The Minimum Inhibitory Concentration (MIC) was assessed for each AMP; then, the most active ones (Citropin 1.1, Temporin A, CA(1-7)M(2-9)NH2 and Pal-KGK-NH2) were tested against selected MRSA strains by time-kill studies.

RESULTS

The lowest MIC value was observed for Pal-KGK-NH2 (1 µg/ml), followed by Temporin A (4- 16 µg/ml), CA(1-7)M(2-9)NH2 (8-16 µg/ml) and Citropin 1.1 (16-64 µg/ml), while higher MICs were evidenced for LL-37, Pexiganan and Pal-KKKK-NH2 (> 128 µg/ml). In time-kill experiments, Citropin 1.1 and CA(1-7)M(2-9)NH2 showed a relatively high percentage of growth inhibition (>30 %) for all the tested MRSA clinical isolates, with a dose-dependent activity resulting in the highest percentage of bacterial growth inhibition (89.39%) at 2MIC concentration.

CONCLUSION

Overall, our data demonstrated the potential of some AMPs against MRSA isolates, such as Citropin 1.1 and CA(1-7)M(2-9)NH2, that represents a promising area of development for different clinical applications.

Efficacy of Pexiganan Combination with Tigecycline in a Mouse Model of Pseudomonas aeruginosa Sepsis

BACKGROUND

Pseudomonas aeruginosa is a gram-negative pathogen, associated with a severe mortality rate. It is also difficult to treat due to numerous resistance mechanisms to a wide range of antibiotics.

OBJECTIVE

Evaluate the activity of pexiganan, an antimicrobial peptide, in combination with two clinical antibiotics (azithromycin and tigecycline) that are not active against P. aeruginosa.

METHODS

Ten clinical P. aeruginosa were isolated from urinary tract infections, blood culture, skin infections and respiratory tract infections. Minimum inhibitory concentrations (MICs) and synergies were evaluated by broth microdilution, checkerboard assays and time-kill studies. In vitro synergy was confirmed with an in vivo experiment using a murine model of sepsis.

RESULTS

Pexiganan MICs were included between 2 and 16 mg/L. Tigecycline and azithromycin MICs were high as expected (4-64 mg/L and 32-256 mg/L, respectively). Pexiganan and azithromycin combination resulted to be additive or indifferent while tigecycline and pexiganan combination was synergic against seven out of ten P. aeruginosa and additive against the other strains. In vivo experiment confirmed the in vitro synergy, denoting a significative reduction of bacteria in mice treated with pexiganan and tigecycline combination.

CONCLUSION

Antimicrobial peptides are molecules that could be useful in the fight against infections and pexiganan seems to be one of the most promising. Our results demonstrated that, in association with tigecycline, pexiganan administration could overcome antibiotic resistance and increase the effectiveness of treatment against P. aeruginosa sepsis.

Characterization of a Multiresistance Plasmid Carrying the optrA and cfr Resistance Genes From an Enterococcus faecium Clinical Isolate

Enterococcus faecium E35048, a bloodstream isolate from Italy, was the first strain where the oxazolidinone resistance gene optrA was detected outside China. The strain was also positive for the oxazolidinone resistance gene cfr. WGS analysis revealed that the two genes were linked (23.1 kb apart), being co-carried by a 41,816-bp plasmid that was named pE35048-oc. This plasmid also carried the macrolide resistance gene erm(B) and a backbone related to that of the well-known Enterococcus faecalis plasmid pRE25 (identity 96%, coverage 65%). The optrA gene context was original, optrA being part of a composite transposon, named Tn6628, which was integrated into the gene encoding for the ζ toxin protein (orf19 of pRE25). The cfr gene was flanked by two ISEnfa5 insertion sequences and the element was inserted into an lnu(E) gene. Both optrA and cfr contexts were excisable. pE35048-oc could not be transferred to enterococcal recipients by conjugation or transformation. A plasmid-cured derivative of E. faecium E35048 was obtained following growth at 42°C, and the complete loss of pE35048-oc was confirmed by WGS. pE35048-oc exhibited some similarity but also notable differences from pEF12-0805, a recently described enterococcal plasmid from human E. faecium also co-carrying optrA and cfr; conversely it was completely unrelated to other optrA- and cfr-carrying plasmids from Staphylococcus sciuri. The optrA-cfr linkage is a matter of concern since it could herald the possibility of a co-spread of the two genes, both involved in resistance to last resort agents such as the oxazolidinones.

Comparison of the Antimicrobial Activities of Four Honeys From Three Countries (New Zealand, Cuba, and Kenya)

Skin and chronic wound infections are an increasing and urgent health problem worldwide. Their management is difficult and the development of antibiotic resistance by both planktonic and biofilm-associated bacteria necessitates the use of alternative treatments. The purpose of this study was to compare the antimicrobial activity of four honeys from different floral and geographical origins: Melipona beecheii honey (Cuba) and three Apis mellifera honeys [Manuka honey (New Zealand), A. mellifera honey (Cuba), and African honey (Kenya)]. The physicochemical parameters were within the ranges reported for these honeys and M. beecheii honey stood out due to its acidic character. An agar incorporation technique was used to determine the minimum active dilution of each honey against 52 clinical isolates (34 Gram-positive, 17 Gram-negative, and 1 Candida albicans). The antibiofilm activity of honeys was tested by assessing their ability to inhibit biofilm formation and to disrupt preformed biofilms. Overall, M. beecheii honey had the highest antimicrobial and antibiofilm activity, although a marked disruption in preformed biofilms was shared by all tested honeys. Structural changes induced by M. beecheii honey on Staphylococcus aureus and Pseudomonas aeruginosa cells were observed by transmission electron microscopy suggesting that this honey has a potent antimicrobial action and may be an excellent candidate for the development of topical preparations for the treatment of infected wounds.