Spectroscopic investigation of faeces with surface-enhanced Raman scattering: a case study with coeliac patients on gluten-free diet.

Surface-enhanced Raman scattering (SERS) spectra of faecal samples can be obtained by adding AuNP to their methanol extracts according to the reported protocol, and display bands that are due to bilirubin-like species but also to xanthine and hypoxanthine, two metabolic products secreted by gut bacteria. A total of 27 faecal samples from three different groups, i.e. coeliac patients (n = 9), coeliac patients on gluten-free diet (n = 10) and a control group (n = 8), were characterized with both SERS spectroscopy and 16S rRNA sequencing analysis. Significant differences are present between SERS spectra of coeliac patients and those on gluten-free diet, with a marked increase in the relative intensity of both xanthine and hypoxanthine for the latter. Interestingly, these differences do not correlate with bacterial composition as derived from 16S rRNA sequencing.

Bactericidal activity of three different antiseptic ophthalmic preparations as surgical prophylaxis.

PURPOSE: In the era of antibiotic resistance, there is an increased interest in antiseptic solutions that might represent a reliable option for ocular surface disinfection. The objective of this study is to compare for the first time three different antiseptic ophthalmic preparations to assess their in vitro antimicrobial activity. METHODS: The antiseptic activity of three commercial ophthalmic solutions, IODIM (povidone-iodine 0.6% in hyaluronic acid vehicle-Medivis, Catania, Italy), OZODROP (nanoemulsion with ozonated oil-concentration not specified-FBVision, Ophthalmic Pharmaceuticals, Rome, Italy), and DROPSEPT (chlorhexidine 0.02% and vitamin E 0.5% Tocopherol Polyethylene Glycol 1000 Succinate-TPGS, Sooft Italia, Montegiorgio, Italy), was tested in vitro on six reference strains by time-killing assays. Viable cells were evaluated after 1, 15, 30 min; 2, 6, and 24 h exposure by seeding 100 µl of the suspension (or appropriate dilutions) on LB agar or Sabouraud-dextrose agar. All plates were incubated at 37 °C for 24 h and evaluated by manually counting the colonies. RESULTS: IODIM solution showed a very rapid microbicidal activity: the number of viable cells for all the tested strains was under the detection limit (less than 10 CFU/ml) already after 1 min exposure, and this result was maintained at every incubation time. The rapid antimicrobial activity of povidone-iodine was not replicated when testing the other two antiseptics. CONCLUSIONS: The study reports the great efficacy in reducing bacterial load in a very short time of povidone-iodine 0.6% compared with other antiseptic preparations.

Multi-technique microscopy investigation on bacterial biofilm matrices: a study on Klebsiella pneumoniae clinical strains.

Biofilms are communities of bacteria living embedded in a highly hydrated matrix composed of polysaccharides, proteins, and extracellular DNA. This life style confers numerous advantages to bacteria including protection against external threats. However, they also contribute to increase bacterial resistance against antimicrobials, an issue particularly relevant in dangerous infections. Due to the complexity of the matrix, few information is present in the literature on details of its architecture including the spatial distribution of the macromolecular components which might give hints on the way the biofilm scaffold is built up by bacteria. In this study, we investigated the possibility to combine well-established microbiological procedures with advanced microscopies to get information on composition and distribution of the macromolecular components of biofilm matrices. To this, confocal microscopy, diffraction-limited infrared (IR) spectral imaging, and atomic force microscopy (AFM) were used to explore biofilm produced by a clinical strain of Klebsiella pneumoniae. IR imaging permitted to have clues on how the biofilm grows and spreads on surfaces, and the local distribution of the components within it. Through the analysis of the pure component spectra, it was possible to assess the chemical and structural composition of the saccaridic matrix, confirming the data obtained by NMR. It was also possible to follow the time course of biofilm from 6 up to 48 h when the biofilm grew into a 3-dimensional multi-layered structure, characteristic of colonies of bacteria linked together by a complex matrix. In addition, nanoFTIR and AFM investigations allowed the estimation of biofilm growth in the vertical direction and the morphological analysis of bacterial colonies at different time points and the evaluation of the chemical composition at the nanoscale.

Influence of Bacterial Biofilm Polysaccharide Structure on Interactions with Antimicrobial Peptides: A Study on Klebsiella pneumoniae.

Balneotherapy is a clinically effective complementary approach in the treatment of low-grade inflammation- and stress-related pathologies. The biological mechanisms by which immersion in mineral-medicinal water and the application of mud alleviate symptoms of several pathologies are still not completely understood, but it is known that neuroendocrine and immunological responses­including both humoral and cell-mediated immunity­to balneotherapy are involved in these mechanisms of effectiveness; leading to anti-inflammatory, analgesic, antioxidant, chondroprotective, and anabolic effects together with neuroendocrine-immune regulation in different conditions. Hormesis can play a critical role in all these biological effects and mechanisms of effectiveness. The hormetic effects of balneotherapy can be related to non-specific factors such as heat­which induces the heat shock response, and therefore the synthesis and release of heat shock proteins­and also to specific biochemical components such as hydrogen sulfide (H2S) in sulfurous water and radon in radioactive water. Results from several investigations suggest that the beneficial effects of balneotherapy and hydrotherapy are consistent with the concept of hormesis, and thus support a role for hormesis in hydrothermal treatments.

pKBuS13, a KPC-2-encoding plasmid from Klebsiella pneumoniae sequence type 833, carrying Tn4401b inserted into an Xer site-specific recombination locus.

Here, we report the first detection of a Klebsiella pneumoniae carbapenemase 2 (KPC-2)-producing Klebsiella pneumoniae strain belonging to sequence type 833 (ST833), collected in an Italian hospital from a patient coming from South America. Its bla KPC determinant was carried by a ColE1 plasmid, pKBuS13, that showed the Tn4401b::bla KPC-2 transposon inserted into the regulatory region of an Xer site-specific recombination locus. This interfered with the correct resolution of plasmid multimers into monomers, lowering plasmid stability and leading to overestimation of the number of plasmids harbored by a single host cell. Sequencing of the fragments adjacent to Tn4401b detected a region that did not have significant matches in databases other than the genome of a carbapenem-resistant Escherichia coli strain collected during the same year at a hospital in Boston. This is interesting in an epidemiologic context, as it suggests that despite the absence of tra genes and the instability under nonselective conditions, the circulation of pKBuS13 or of analogous plasmids might be wider than reported.

Role of oxidative stress mediated by glutathione-s-transferase in thiopurines' toxic effects.

Azathioprine (AZA), 6-mercaptopurine (6-MP), and 6-thioguanine (6-TG) are antimetabolite drugs, widely used as immunosuppressants and anticancer agents. Despite their proven efficacy, a high incidence of toxic effects in patients during standard-dose therapy is recorded. The aim of this study is to explain, from a mechanistic point of view, the clinical evidence showing a significant role of glutathione-S-transferase (GST)-M1 genotype on AZA toxicity in inflammatory bowel disease patients. To this aim, the human nontumor IHH and HCEC cell lines were chosen as predictive models of the hepatic and intestinal tissues, respectively. AZA, but not 6-MP and 6-TG, induced a concentration-dependent superoxide anion production that seemed dependent on GSH depletion. N-Acetylcysteine reduced the AZA antiproliferative effect in both cell lines, and GST-M1 overexpression increased both superoxide anion production and cytotoxicity, especially in transfected HCEC cells. In this study, an in vitro model to study thiopurines' metabolism has been set up and helped us to demonstrate, for the first time, a clear role of GST-M1 in modulating AZA cytotoxicity, with a close dependency on superoxide anion production. These results provide the molecular basis to shed light on the clinical evidence suggesting a role of GST-M1 genotype in influencing the toxic effects of AZA treatment.

PACSIN2 as a modulator of autophagy and mercaptopurine cytotoxicity: mechanisms in lymphoid and intestinal cells.

PACSIN2 variants are associated with gastrointestinal effects of thiopurines and thiopurine methyltransferase activity through an uncharacterized mechanism that is postulated to involve autophagy. This study aims to clarify the role of PACSIN2 in autophagy and in thiopurine cytotoxicity in leukemic and intestinal models. Higher autophagy and lower PACSIN2 levels were observed in inflamed compared with non-inflamed colon biopsies of inflammatory bowel disease pediatric patients at diagnosis. PACSIN2 was identified as an inhibitor of autophagy, putatively through inhibition of autophagosome formation by a protein-protein interaction with LC3-II, mediated by a LIR motif. Moreover, PACSIN2 resulted a modulator of mercaptopurine-induced cytotoxicity in intestinal cells, suggesting that PACSIN2-regulated autophagy levels might influence thiopurine sensitivity. However, PACSIN2 modulates cellular thiopurine methyltransferase activity via mechanisms distinct from its modulation of autophagy.

In Vitro and In Vivo Studies of Oritavancin and Fosfomycin Synergism against Vancomycin-Resistant Enterococcus faecium.

Therapeutic options for infections caused by vancomycin-resistant enterococci are currently suboptimal. Combination regimens where fosfomycin is used alongside existing treatments are emerging given the proven synergistic potential and PK/PD properties. In the studies presented here, we tested five vanA and five vanB clinical isolates of Enterococcus faecium using a combination of oritavancin + fosfomycin both in vitro (checkerboard, time killing) and in vivo (Galleria mellonella). The combination of oritavancin and fosfomycin increased drug susceptibility, showing a synergistic effect in 80% of isolates and an additive effect in the remaining isolates. The combination restored fosfomycin susceptibility in 85% of fosfomycin-resistant isolates. Time killing on four selected isolates demonstrated that the combination of oritavancin and fosfomycin provided a CFU/mL reduction > 2 log10 compared with the most effective drug alone and prevented the bacterial regrowth seen after 8−24 h at sub-inhibitory drug concentrations. In addition, the combination was also tested in a biofilm assay with two isolates, and a strong synergistic effect was observed in one isolate and an additive effect in the other. Finally, we demonstrated in vivo (Galleria mellonella) a higher survival rate of the larvae treated with the combination therapy compared to monotherapy (fosfomycin or oritavancin alone). Our study provides preclinical evidence to support trials combining oritavancin and fosfomycin for VRE BSI in humans, even when biofilm is involved.

Correction: Morroni et al. Antimicrobial Activity of Aztreonam in Combination with Old and New ß-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 [...].

Aspirin and Infection: A Narrative Review.

Acetylsalicylic acid (ASA) is one of the most commonly used drugs in the world. It derives from the extract of white willow bark, whose therapeutic potential was known in Egypt since 1534 BC. ASA's pharmacological effects are historically considered secondary to its anti-inflammatory, platelet-inhibiting properties; however, human studies demonstrating a pro-inflammatory effect of ASA exist. It is likely that we are aware of only part of ASA's mechanisms of action; moreover, the clinical effect is largely dependent on dosages. During the past few decades, evidence of the anti-infective properties of ASA has emerged. We performed a review of such research in order to provide a comprehensive overview of ASA and viral, bacterial, fungal and parasitic infections, as well as ASA's antibiofilm properties.

Synergistic activity of fosfomycin and chloramphenicol against vancomycin-resistant Enterococcus faecium (VREfm) isolates from bloodstream infections.

Vancomycin-resistant Enterococcus faecium (VREfm) infections are increasing. Current anti-VREfm options (linezolid and daptomycin) are suboptimal. Fosfomycin maintains good efficacy against VREfm and chloramphenicol is active against ≥ 90% of VREfm. We tested chloramphenicol + fosfomycin (CAF+FOS) against 10 VREfm isolated from blood. MICs were 64 to 512 µg/mL for fosfomycin and 8 to 16 µg/mL for chloramphenicol. The combination decreased both MICs, with a synergic effect in 50% of the isolates and an additive effect in the remaining 50%. Time-kill assays performed on fractional inhibitory concentration index ≤ 0.5 strains confirmed the synergism. The antibiotic combination at » of minimum inhibitory concentrations (MICs) caused a ≥ 2 log10 reduction compared to the two antibiotics alone. Finally, we provided a proof of concept of the in vitro efficacy of CAF+FOS in G. mellonella. The survival of G. mellonella larvae treated with the combination was significantly higher. The activity of fosfomycin and chloramphenicol against VREfm increases when they are used in combination.

Interplay of OpdP Porin and Chromosomal Carbapenemases in the Determination of Carbapenem Resistance/Susceptibility in Pseudomonas aeruginosa.

Carbapenem resistance in Pseudomonas aeruginosa strains responsible for chronic lung infections in cystic fibrosis (CF) patients is mainly due to loss of the OprD protein and, limited to meropenem and doripenem, to overexpression of efflux pumps. However, recent reports of isolates showing inconsistent genotype-phenotype combinations (e.g., susceptibility in the presence of resistance determinants and vice versa) suggest the involvement of additional factors whose role is not yet fully elucidated. Among them, the OpdP porin as an alternative route of entry for carbapenems other than OprD and the overexpression of two chromosomal carbapenemases, the Pseudomonas-derived cephalosporinase (PDC) and the PoxB oxacillinase, have recently been reconsidered and studied in specific model strains. Here, the contribution of these factors was investigated by comparing different phenotypic variants of three strains collected from the sputum of colonized CF patients. Carbapenem uptake through OpdP was investigated both at the functional level, by assessing the competition exerted by glycine-glutamate, the OpdP's natural substrate, against imipenem uptake, and at the molecular level, by comparing the expression levels of opdP genes by quantitative real-time PCR (qRT-PCR). Moreover, overexpression of the chromosomal carbapenemases in some of the isolates was also investigated by qRT-PCR. The results showed that, even if OprD inactivation remains the most important determinant of carbapenem resistance in strains infecting the CF lung, the interplay of other determinants might have a nonnegligible impact on bacterial susceptibility, being able to modify the phenotype of part of the population and consequently complicating the choice of an appropriate therapy. IMPORTANCE This study examines the interplay of multiple factors in determining a pattern of resistance or susceptibility to carbapenems in clinical isolates of Pseudomonas aeruginosa, focusing on the role of previously poorly understood determinants. In particular, the impact of carbapenem permeability through OprD and OpdP porins was analyzed, as well as the activity of the chromosomal carbapenemases AmpC and PoxB, going beyond the simple identification of resistance determinants encoded by each isolate. Indeed, analysis of the expression levels of these determinants provides a new approach to determine the contribution of each factor, both individually and in coexistence with the other factors. The study contributes to understanding some phenotype-genotype discordances closely related to the heteroresistance frequently detected in P. aeruginosa isolates responsible for pulmonary infections in cystic fibrosis patients, which complicates the choice of an appropriate patient-specific therapy.

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

Metallo-ß-lactamases (MBLs) are among the most challenging bacterial enzymes to overcome. Aztreonam (ATM) is the only ß-lactam not hydrolyzed by MBLs but is often inactivated by co-produced extended-spectrum ß-lactamases (ESBL). We assessed the activity of the combination of ATM with old and new ß-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.

Zidovudine in synergistic combination with fosfomycin: an in vitro and in vivo evaluation against multidrug-resistant Enterobacterales.

Multidrug-resistant (MDR) Enterobacterales are a priority health issue with few treatment options. Recently, fosfomycin has been reconsidered for MDR bacterial infections. Zidovudine, licensed for the treatment of human immunodeficiency virus (HIV), has unexploited antibacterial properties and has been considered for drug repurposing. The aim of this study was to assess the effect of the combination of fosfomycin plus zidovudine against clinical MDR Enterobacterales isolates. Minimum inhibitory concentration (MIC) determination and checkerboard assays for 36 MDR Enterobacterales strains were performed. In addition, fosfomycin-resistant strains were evaluated using time-kill assay and in an in vivo Galleria mellonella infection model. Zidovudine and fosfomycin MICs ranged between 0.06 to >64 mg/L and 0.125 to >512 mg/L, respectively. A synergistic effect [fractional inhibitory concentration index (FICI) ≤0.5] was observed in 25 isolates and no antagonistic effect was observed in the remaining isolates. For 7 of 8 fosfomycin-resistant strains (MIC > 32 mg/L), zidovudine combination was able to restore fosfomycin susceptibility. These results were confirmed by time-kill assays. Fosfomycin + zidovudine presented greater larval survival (20-50%) than monotherapy. Synergistic activity was observed for fosfomycin + zidovudine in 69.4% of the tested strains. In vivo experiments confirmed the enhanced effectiveness of the combination. The zidovudine concentrations tested here can be reached in human serum using the actual licensed dosage, therefore this combination deserves further clinical investigation.

Emerging Insights on the Interaction Between Anticancer and Immunosuppressant Drugs and Intestinal Microbiota in Pediatric Patients.

Diseases affecting the immune system, such as inflammatory bowel disease (IBD), juvenile idiopathic arthritis (JIA), and acute lymphoblastic leukemia (ALL), are pathological conditions affecting the pediatric population and are often associated with alterations in the intestinal microbiota, such as a decrease in bacterial diversity. Growing evidence suggests that gut microbiota can interfere with chemotherapeutic and immunosuppressant drugs, used in the treatment of these diseases, reducing or facilitating drug efficacy. In particular, the effect of intestinal microflora through translocation, immunomodulation, metabolism, enzymatic degradation, and reduction of bacterial diversity seems to be one of the reasons of interindividual variability in the therapeutic response. Although the extent of the role of intestinal microflora in chemotherapy and immunosuppression remains still unresolved, current evidence on bacterial compositional shifts will be taken in consideration together with clinical response to drugs for a better and personalized therapy. This review is focused on the effect of the intestinal microbiota on the efficacy of pharmacological therapy of agents used to treat IBD, JIA, and ALL.

Determination of the capsular polysaccharide structure of the Klebsiella pneumoniae ST512 representative strain KPB-1 and assignments of the glycosyltransferases functions.

Klebsiella pneumoniae strain KPB-1 was isolated in early 2011 from the pleural fluid of an inpatient admitted at an Italian hospital. It was characterized to produce the KPC-3 carbapenemase and to belong to sequence type 512, a derivative of sequence type 258 clade II characterized by the cps-2 gene cluster. The K-antigen of K. pneumoniae KPB-1 was purified and its structure determined by using GLC-MS of appropriate carbohydrate derivatives and 1D and 2D NMR spectroscopy of the native polysaccharide. All the collected data demonstrated the following repeating unit for the K. pneumoniae KPB-1 capsular polysaccharide: The reactions catalysed by each glycosyltransferase in the cps-2 gene cluster were assigned on the basis of structural homology with other Klebsiella K antigens.

Colonization of the tip of a thoracic catheter by Enterococcus faecalis resistant to vancomycin and linezolid.

We report the isolation of Enterococcus faecalis resistant to vancomycin and linezolid from the tip of a thoracic drainage catheter in an elderly patient. He was treated with vancomycin for a pleural empyema due to a meticillin-resistant Staphylococcus aureus but never received linezolid. A surveillance rectal swab yielded both linezolid-susceptible and -resistant strains, and the two isolates were not genotypically related. Careful monitoring for linezolid-resistance is critical to avoid potential therapy failure and transmission of resistant E. faecalis.

Sub-MIC effects of a proline-rich antibacterial peptide on clinical isolates of Acinetobacter baumannii.

INTRODUCTION: Acinetobacter baumannii is one of the most important nosocomial pathogens, mainly due to its ability to accumulate antibiotic-resistances and to persist in the hospital environment - characteristics related to biofilm production. It is well-known that A. baumannii is inhibited by the proline-rich peptide Bac7(1-35), but its putative effects at sub-MICs were never considered. AIMS: We examined the sub-MIC effect of Bac7(1-35) on the growth rate, resistance induction and some A. baumannii features linked to virulence. METHODOLOGY: Growth kinetics in the presence of sub-MICs of Bac7(1-35) were evaluated spectrophotometrically. Peptide uptake was quantified by cytometric analysis. The ability of Bac7(1-35) to interfere with biofilm production was investigated by the crystal violet method and confocal microscopy. Bacterial motility was observed at the interphase between a layer of a semi-solid medium and the polystyrene bottom of a Petri dish. The induction of resistance was evaluated after serial passages with sub-MICs of the peptide. RESULTS: Although the MIC of Bac7(1-35) was between 2-4 µM for all tested strains, its effect on the growth rate at sub-MICs was strain-dependent and correlated with the amount of peptide internalized by each strain. Sub-MICs of Bac7(1-35) induced a strongly strain-dependent effect on biofilm formation and reduced motility in almost all strains, but interestingly the peptide did not induce resistance. CONCLUSION: Bac7(1-35) is internalized into A. baumannii and is able to inhibit biofilm formation and bacterial motility, without inducing resistance. This study stresses the importance of considering possible effects that antimicrobials could have at sub-MICs, mimicking a common condition during antibiotic treatment.

Aspergillus fumigatus biofilm formation on different bone substitutes used in maxillary sinus augmentation: an in vitro analysis.

BACKGROUND: Fungus ball (FB) typically affects healthy adults, and Aspergillus fumigatus is the most frequent etiologic agent: iatrogenic factors represent an important issue in FB pathogenesis. Moreover, a recent study suggested a significant association between the use of anorganic bovine bone as sinus grafting material and subsequent development of FB. The aim of the present investigation is to evaluate in vitro eventual differences in the ability of Aspergillus fumigatus to colonize different bone grafting materials and grow on them as biofilm. FINDINGS: Five different bone substitutes (demineralized bone matrix, anorganic bovine bone, ß-tricalcium phosphate, synthetic nano-hydroxyapatite, and synthetic hydroxyapatite), commonly used in sinus floor augmentation procedures, were inoculated with conidia suspensions of A. fumigatus and incubated at 37 °C for 4 and 8 h, in standardized conditions. Biofilm bound to the different materials underwent quantitative and qualitative analysis by confocal and scanning electron microscopy. A. fumigatus proved to be able to adhere and form biofilm on all the tested bone substitutes. The surface plot representation of the samples displayed some differences in the density of the superficial layer, due to the physical characteristics of the biomaterials. Nevertheless, Kruskal-Wallis test showed no significant differences in biomass amount among the five bone substitutes (p = 0.236 and p = 0.55 after 4 and 8 h adhesion, respectively). CONCLUSIONS: All the bone substitutes normally used in sinus floor augmentation represent a favorable substrate for fungal growth, due to their physical and chemical characteristics. During sinus floor elevation procedures, Schneiderian membrane integrity should be maintained in order to avoid the exposure of the grafting material at the respiratory environment, with potential risks of fungal colonization.

Structure of the capsular polysaccharide of the KPC-2-producing Klebsiella pneumoniae strain KK207-2 and assignment of the glycosyltransferases functions.

Klebsiella pneumoniae strain KK207-2 was isolated in 2010 from a bloodstream infection of an inpatient at an Italian hospital. It was previously found to produce the KPC-2 carbapenemase and to belong to clade 1 of sequence type 258. Genotyping of the conserved wzi and wzc genes from strain KK207-2 yielded contrasting results: the wzc-based method assigned the cps207-2 to a new K-type, while the wzi-based method assigned it to the known K41 K-type. In order to resolve this contradiction, the capsular polysaccharide of K. pneumoniae KK207-2 was purified and its structure determined by using GLC-MS of appropriate carbohydrate derivatives, ESI-MS of both partial hydrolysis and Smith degradation derived oligosaccharides, and NMR spectroscopy of oligosaccharides, and the lithium degraded, native and de-O-acetylated polysaccharide. All the collected data demonstrated the following repeating unit for the K. pneumoniae KK207-2 capsular polysaccharide: The polysaccharide contains about 0.60 acetyl groups per repeating unit on C6 of the Gal residue. The reactions catalyzed by each glycosyltransferase in the cpsKK207-2 gene cluster were assigned on the basis of structural homology with other Klebsiella K antigens.