Giammarco Raponi

Risk factors for acute kidney injury in critically ill patients receiving high intravenous doses of colistin methanesulfonate and/or other nephrotoxic antibiotics: a retrospective cohort study

IntroductionUse of colistin methanesulfonate (CMS) was abandoned in the 1970s because of excessive nephrotoxicity, but it has been reintroduced as a last-resort treatment for extensively drug-resistant infections caused by gram-negative bacteria (Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumonia). We conducted a retrospective cohort study to evaluate risk factors for new-onset acute kidney injury (AKI) in critically ill patients receiving high intravenous doses of colistin methanesulfonate and/or other nephrotoxic antibiotics.MethodsThe cohort consisted of 279 adults admitted to two general ICUs in teaching hospitals between 1 April 2009 and 30 June 2011 with 1) no evidence on admission of acute or chronic kidney disease; and 2) treatment for more than seven days with CMS and/or other nephrotoxic antimicrobials (NAs, that is, aminoglycosides, glycopeptides). Logistic regression analysis was used to identify risk factors associated with this outcome.ResultsThe 279 cases that met the inclusion criteria included 147 patients treated with CMS, alone (n = 90) or with NAs (n = 57), and 132 treated with NAs alone. The 111 (40%) who developed AKI were significantly older and had significantly higher Simplified Acute Physiology Score II (SAPS II) scores than those who did not develop AKI, but rates of hypertension, diabetes mellitus and congestive heart failure were similar in the two groups. The final logistic regression model showed that in the 147 patients who received CMS alone or with NAs, onset of AKI during the ICU stay was associated with septic shock and with SAPS II scores ≥43. Similar results were obtained in the 222 patients treated with CMS alone or NAs alone.ConclusionsIn severely ill ICU patients without pre-existing renal disease who receive CMS high-dose for more than seven days, CMS therapy does not appear to be a risk factor for this outcome. Instead, the development of AKI was strongly correlated with the presence of septic shock and with the severity of the patients as reflected by the SAPS II score.

Serum-Mediated Enhancement of TNF-α Release by Human Monocytes Stimulated with the Yeast Form of Candida albicans

The role of serum in the production of tumor necrosis factor-alpha (TNF-alpha) by human monocytes stimulated with yeast-form Candida albicans was studied. Pre-exposure of C. albicans to human pooled serum enhanced both TNF-alpha mRNA and cytokine secretion compared with C. albicans preincubated with medium only. Serum factors involved were >30 kDa, were efficiently inhibited by D-mannose, and recognized both Ca++-dependent and -independent pathways. Preincubation of yeasts with rabbit mannose-binding protein (MBP) resulted in dose-related enhancement of TNF-alpha secretion, through a Ca++-dependent pathway inhibited by D-mannose. TNF-alpha levels were similarly induced in C. albicans preincubated with vitronectin and with serum. Ca++ depletion did not affect cytokine release, while D-mannose supplementation displayed inhibition. The latter effect was abolished after Ca++ depletion. These data call for an involvement of both MBP and vitronectin in the serum-mediated enhancement of TNF-alpha release upon stimulation of monocytes with yeast forms of C. albicans.

Antimicrobial Susceptibility, Biochemical and Genetic Profiles of Staphylococcus haemolyticus Strains Isolated from the Bloodstream of Patients Hospitalized in Critical Care Units

Abstract Staphylococcus haemolyticus strains (n=20), responsible of blood stream infections, were consecutively isolated from patients hospitalized in two different wards at high risk of infection. Strains displayed high rate of resistance to oxacillin (90%). All strains but two with decreased susceptibility (MIC = 4 μg/mL), were sensitive to vancomycin. Ten strains were resistant to teicoplanin. Among the strains susceptible to glycopeptides, three displayed heteroresistance to vancomycin and seven to teicoplanin, when tested by Etest technique with 2 x McFarland inoculum. Biochemical reactions allowed to assign strains to eight biotypes, with 11 strains clustering under two main biotype A and biotype B. Pulsed-field-gel-electrophoresis (PFGE) identified 11 different PFGE-types. Seven strains grouping under the major PFGE-type 1 and three strains clustering in PFGE-type 2, closely correlated to biotype A and biotype B respectively. Seven teicoplanin-resistant isolates clustered in the PFGE-type 1, two in the PFGE-type 2 and one in PFGE-type 5. Therefore, teicoplanin-resistant strains were biochemically and genetically related and clonally distributed, despite different clones of S. haemolyticus circulated in the units during the study period.

Clostridium difficile Infection and Candida Colonization of the Gut: Is There a Correlation?

TO THE EDITOR—We read with interest the article of Manian and Bryant about the possible protective role of gut colonization by Candida species against Clostridium difficile infection (CDI) [1]. Although Candida has been involved as part of the normal intestinal microbiota [2], no recent data seem to confirm the authors’ results. Conversely, an opposite role for non-albicans Candida (NAC) colonization was suggested by Nerandzic et al in a trial on 548 patients with CDI [3]. Recent observations conducted in our 1300-bed teaching hospital Policlinico “Umberto I” in Rome showed that patients treated for severe CDI developed at least 1 episode of candidemia, thus hypothesizing a link between CDI and candidemia [4]. We designed a prospective casecontrol study in diarrheic patients with suspected CDI from November 2013 until June 2014 to investigate whether Candida colonization of the gut and CDI may be linked. Stool specimens (n = 140; Bristol stool chart 5–7 [5]) from consecutive patients were evaluated for glutamate dehydrogenase and CD toxin A/B by immunochromatography tests (C-Diff Quick Check Complete, Techlab); positive samples were screened for the C. difficile Pa-Loc gene and for 027 ribotype by reverse transcription polymerase chain reaction (RT-PCR) (GeneXpert, Cepheid, Sweden). Candida was revealed by plating 10 μL of all samples on Sabouraudchloramphenicol agar (Liofilchem, Italy), incubated for 24–48 hours at 37°C. Candida colonization was defined as the growth of ≥10 colony-forming units per milliliter of stool sample. The yeasts were typed through their biochemical profiles (Api ID 32 C, bioMérieux). Mantel-Haenszel test and Stata 11 software were used for statistical analysis; an α error <.05 was accepted. The 140 patients averaged 65 ± 22.98 years of age, and 52% were male. One hundred patients had negative results and 40 positive results for CDI, as revealed by both the immunochromatography reactivity and by the RT-PCR for the Pa-Loc gene presence, which showed that 10 patients were infected by the 027 ribotype. CDI was significantly associated with Candida colonization (83% CDI positive vs 67% CDI negative; χ = 3.91; P < .05). Candida albicans was the species more often implicated ( χ = 4.82; P = .02; Table 1). All except 1 of the ten 027 ribotype–infected patients were colonized by the yeast, 7 of which were C. albicans (χ = 0.37; P = .5). Our data provided evidence that Candida colonization and CDI are linked, thus suggesting a role for the yeast during CDI. The prevalence of yeasts observed in our study was higher than that reported by others [1, 3], probably due to differences in the cultural and typing methods, or to different study populations. Indeed, Manian and Bryant evoked a protective role for Candida in competing with C. difficile, as they observed a lower prevalence of Candida colonization in only 16.7% of the CDIpositive patients. Unfortunately, the authors did not perform any quantitative assessment of Candida growth, referring only to the overgrowth of the yeast covering >50% of an agar plate [1]. Similarly, the higher prevalence of NAC observed in Nerandzic et al’s study (68% NAC vs 32% of C. albicans) can be affected by the storage conditions used in their study [3]. Further studies are in progress to find out a correlation between CDI and candidemia and to reveal the pathogenic mechanisms underlying this association.

Analysis of methods commonly used for glycopeptide and oxazolidinone susceptibility testing in Enterococcus faecium isolates

The susceptibility to teicoplanin, vancomycin and linezolid of 30 clinical isolates of Enterococcus faecium was tested by Vitek 2, Phoenix, Etest, broth microdilution and disc diffusion tests. The vanA and vanB resistance genes and the 23S rRNA gene G2576T mutation were detected by PCR and PCR-RFLP, respectively. Resistance rates to teicoplanin ranged from 3% for Vitek 2 to 57.6% for the Phoenix test, and those to vancomycin ranged from 56.7% for Vitek 2 to 86.7% for the Phoenix test. Only two out of 25 strains carrying the vanA gene were univocally recognized as the VanA phenotype. The only strain with the G2576T mutation did not carry the vanA gene and showed resistance to linezolid by the disc diffusion, Vitek 2 and broth dilution methods (MIC>8 microg ml(-1)), but was susceptible when tested with the Phoenix test and Etest (MIC<or=4 microg ml(-1)). Therefore, the resistance to glycopeptides and linezolid was not univocally detected by the susceptibility testing methods used in this study.

Voriconazole treatment of Candida tropicalis meningitis: persistence of (1,3)-β-D-glucan in the cerebrospinal fluid is a marker of clinical and microbiological failure

Introduction: Infections are still the most common complications of cerebral shunt procedures. Even though fungal etiologies are considered to be rare, they are associated with significant morbidity and mortality. Due to their uncommonness, diagnostic procedures and optimal therapy are poorly defined. We report a case of Candida tropicalis infection of ventriculo-peritoneal cerebrospinal fluid (CSF) shunt in a 49-year-old immune competent male treated with voriconazole (VOR). Methods: Microbiological and CSF markers (1,3-b-D-glucan-BDG) of fungal infection, biofilm production capacity, sensitivity of serial isolates of the pathogen, and the concentration of the antifungal drug have been monitored and related to the clinical course of this infection. Results: Despite appropriate treatment with VOR, in terms of adequate achieved CSF drug concentrations and initial effective therapeutic response, loss of VOR susceptibility of the C tropicalis and treatment failure were observed. Conclusion: Biofilm production of the C. tropicalis isolate might have had a significant role in treatment failure. Of interest, clinical and microbiological unfavorable outcome was anticipated by persistence of BDG in CSF. Rising titers of this marker were associated with relapse of fungal infection.

Candidaemia after heart valve replacement surgery: recurrence as prosthetic valve endocarditis is an expected over one-year complication

Sir, We read with interest the article on risk factors for late recurrent candidaemia by Munoz et al. [1]. The authors conclude that episodes of recurrent candidaemia within the first 3 months could be attributable to an intravascular source of infection as opposed to an intra-abdominal origin for those occurring later. We noted that the clinical course of patient no. 4 included in Munoz series refers to a late-onset prosthetic valve endocarditis (PVE) due to Candida parapsilosis diagnosed 1-year after prosthetic valve implantation. In particular, the patient was initially treated with 3 weeks of amphotericin B and fluconazole for two episodes of post-operative C. parapsilosis candidaemia, and was then discharged without evidence of endocarditis at trans-oesophageal echocardiography. The patient was readmitted 1 year later with signs and symptoms of septic shock due to a C. parapsilosis PVE and died 1 week after admission; importantly, the isolates belonged to the same genotype [1]. In 1974 Seelig et al. [2] reported the clinical features of two patients who presented Candida bloodstream infection within 1 month from prosthesis implantation and developed a Candida PVE, due to the same species, after 13 and 15 months. Interestingly, during recent years we have observed four patients

Protective features of monoclonal antibodies to Escherichia coli during experimental infection of mice with homologous and heterologous serotypes of E. coli

Murine monoclonal antibodies (MAbs) MT1F and ARM1-4, recognising proteins on the surface of untreated Escherichia coli O6:K-, protected 100% of mice challenged intraperitoneally with 2 x LD50 of the same strain. MAb MT1F protected 70% of animals challenged with 2 x LD50 of E. coli O111:B4, whereas ARM1-4 gave complete protection. Lower survival was observed in mice given either MAb and challenged with E. coli O128:K-, with values ranging from 30 to 42%. However, the protection afforded against E. coli O111:B4 and E. coli O128:K- was significantly improved when the mice were pre-treated with a mixture of the two MAbs. Control mice, pre-treated with unrelated ascitic fluid and challenged with any of the E. coli serotypes, showed 100% mortality and organ histological lesions resembling those of the early stages of septic shock. The mice had high levels of circulating endotoxin and tumour necrosis factor-alpha (TNF-alpha) at 90 min after challenge. In contrast, mice treated with MAbs and surviving the infection displayed moderate histological lesions, enhanced bacterial clearance and lower serum levels of TNF-alpha, despite circulating endotoxin levels that were higher than in the control group. Protection by the MAbs was probably due to the prevention of the bacterial spread to organs and of the cascade of events leading to septic shock. This occurred in spite of the presence of high levels of circulating endotoxin.

Murine monoclonal antibody elicited with antibiotic-exposed Escherichia coli exerts protective capacity in experimental bacterial infections

Escherichia coli pre-exposed to a sub-minimal inhibitory concentration (sub-MIC) of several antibiotics elicits an enhanced humoral response which is protective against challenges with untreated homologous and heterologous bacteria. To characterise the specificity of this response we produced murine monoclonal antibodies (MAbs) to aztreonam-treated E. coli O6:K-. This resulted in the identification of MAb MT 1F, of isotype IgG1, that recognised a 12-kDa protein component of the untreated bacterial cells. After passive transfer, the MAb displayed protective activity in mice infected with lethal doses of live E. coli O6:K- and E. coli O111:B4. In ELISA experiments the MAb cross-reacted with structures located on whole cells of E. coli O6:K-, E. coli O111:B4, E. coli J5 and Salmonella minnesota Re595 and it also exerted a bactericidal activity against live E. coli O6:K-. The modifications induced by antibiotic treatment may unmask bacterial epitopes that may elicit the production of MAbs endowed with protective capacity.

Opsonic activity of intravenous immune globulin on Gram-negative bacteria exposed to a monobactam antibiotic

Abstract Sub-inhibitory concentrations of antibiotics can alter the morphology and structure of the bacterial surface leading to better opsonization and therefore enhanced phagocytosis. The opsonic activity of a standard intravenous immune gamma globulin (IVIG) was tested for control bacteria and bacteria grown in the presence of sub-minimal inhibitory concentration (sub-MIC) of aztreonam, and β-lactam antibiotic. IVIG enhanced uptake by polymorphonuclear leucocytes of five Gram-negative bacteria. This enhancement was further increased when bacteria were exposed to sub-MIC of aztreonam.