Colonization and infection due to multi-resistant bacteria in neonates: a single center analysis

BACKGROUND

In the last years the prevalence of multi-resistant pathogens (MRPs) has increased. Systemic infections remain important for neonatal morbidity and mortality.

PATIENTS

Neonates born between January 2011 and December 2012 and admitted to the neonatology before their tenth day of life were included into this retrospective analysis. Vancomycin-resistant Enterococci, Methicillin-resistant Staphylococcus aureus, Gram-negative bacilli with Extend Spectrum Beta Lactamase or AMP-C resistance were defined as multi-resistant pathogens (MRPs). MRP positive and negative patients were analyzed regarding clinical risk factors and the incidence of systemic infections.

RESULTS

635 neonates were admitted during the analysis period. In 31 patients MRPs were detected. 2 patients developed MRP-associated infections. Both were discharged without long term health risks. Low gestational age and need for mechanical ventilation were risk factors for colonization with MRPs in the univariat analysis. The incidence density (per 1 000 patient days) for all MRE increased from 0.76 in 2011 to 3.51 in 2012. In contrast the sepsis rate remained stable (14.9% and 14.2%). 2 MRP colonization clusters were detected by routine microbiology swabs. Both could be controlled by appropriate hygienic measures.

CONCLUSIONS

The prevalence of Gram-negative MRPs increased in neonates. Microbiological screening seems to be helpful for early detection of colonization and thus prevention of nosocomial infections with MRPs. Despite the increased attention towards the problems associated with multiresistant bacteria, there are still major efforts needed for prevention and early treatment of sepsis with non-resistant bacteria.

[Immunosuppressive treatment as a risk factor for the occurrence of clostridium difficile infection (CDI)]

BACKGROUND

Toxigenic Clostridium difficile strains are known as the most common infectious cause of antibiotic-associated intestinal disease and nosocomial diarrhoea. The increased incidence of hypervirulent strains gives rise to worldwide concern. In particular, courses with multiple recurrences are observed in the presence of immunosuppression.

METHODS

In this retrospective controlled observational study we aimed to determine immunosuppression as an independent risk factor for symptomatic CDI and to identify characteristics and differences of immunocompromised patients with respect to disease severity, disease progression, intestinal manifestations, recurrence rates and other factors. We compared symptoms and clinical features of 55 immunosuppressed patients with confirmed CDI with those of 50 patients without immunosuppressive medication (mean age 59.3 years ± 16.2 vs. 69.2 years ± 15.0) who were treated at the Departments of Internal Medicine I and IV of the University Hospital Halle (Saale), Germany, between 2006 and 2009. Multivariate analysis using binary logistic regression was performed for a control group of 105 patients without CDI. In this group, there were 62 patients without evidence of immunosuppression and 43 immunosuppressed patients (mean age 66.9 years ± 12.4 vs. 56.0 years ± 13.7).

RESULTS

The clinical courses of the two groups differed considerably. Immunosuppressed patients were significantly more frequently colonised with Clostridium difficile without clinically detectable manifestation or only mild clinical symptoms not requiring therapy (22 vs. 2 %, p = 0.003), while there were similar numbers of moderate (46 vs. 52 %, p = 0.503) but less severe CDI cases (27 vs. 40 %, p = 0.167). Relapses were observed more frequently in the group of immunosuppressed patients (15 vs. 6 %, p = 0.153). Multivariate analysis using logistic regression identified immunosuppression as an independent risk factor for CDI (OR = 2.75), in addition to prior antibiotic therapy (OR = 10.15) and PPI intake (OR = 2.93).

CONCLUSION

We conclude that immunosuppression has to be regarded as an independent risk factor for CDI. Immunosuppressive treatment increases the risk of colonisation and infection with Clostridium difficile and leads to a higher relapse rate in patients with CDI.

[Antibiotic treatment of enterococcal infections in gastroenterology with daptomycin - first experiences from the EU-CORE registry study (European Cubicin® Outcomes Registry and Experience)]

Enterococci are a frequent cause of nosocomial infections in gastroenterology. The increase of Enterococcus faecium infections with development of resistance to gentamicin and vancomycin as well as possible linezolid resistance require alternative antibiotic therapies. Study data show that daptomycin, a highly bactericidal antibiotic is effective in enterococcal infections. However, in Germany daptomycin is so far only approved for the treatment of complicated skin and soft tissue infections, bacteremia and infective endocarditis caused by Staphylococcus aureus. In the Department of Internal Medicine I, University Hospital Halle (Saale) from May 2 009 to April 2 010 all gastroenterological patients with evidence of invasive enterococcal infection received intravenous daptomycin treatment at inclusion in the European Cubicin® Outcomes Registry and Experience (EU-CORE). Gastroenterological diseases treated were necrotising pancreatitis, infected pancreatic pseudocysts, abscesses, obstructive cholangitis and sepsis. The clinical outcome was retrospectively detected by protocol-defined criteria. A total of 13 patients (8 male, 5 female, median age 59 years) with microbiologically assured enterococcal infections (10 × E. faecium, including 1 × VRE, 6 × E. faecalis, including double infections) were treated with intravenous daptomycin (6 mg per kg body weight). In the presence of polymicrobial infections (10 of 13 patients), an additional anti-infective therapy was initiated according to sensitivity testing. Concomitantly a direct focus approach with stenting, puncture or drainage was performed. The clinical cure rate was 92 % (12 of 13 patients). One patient died from a non-surgically uncontrollable malignancy (Klatskin tumour Bismuth IIIb). There were no adverse events. These results allow us to conclude that antibiotic therapy with daptomycin in invasive or bacteraemic enterococcal infections leads to high cure rates (up to 90 % and more) when concomitant and adequate focus relief is performed. Larger clinical studies to obtain an extended drug approval are desirable.

Effects of amoxicillin, gentamicin, and moxifloxacin on the hemolytic activity of Staphylococcus aureus in vitro and in vivo

In Staphylococcus aureus infection hemolysis caused by the extracellular protein alpha-toxin encoded by hla is thought to contribute significantly to its multifactorial virulence. In vitro, subinhibitory concentrations of beta-lactam antibiotics and fluoroquinolones increase the levels of hla and alpha-toxin expression, whereas aminoglycosides decrease the levels of hla and alpha-toxin expression. In the present study we investigated the effects of subinhibitory concentrations of amoxicillin, gentamicin, and moxifloxacin on hla and alpha-toxin expression and total hemolysis of S. aureus strain 8325-4, a high-level alpha-toxin producer, and its alpha-toxin-negative mutant, DU 1090, in vitro and in a rat model of chronic S. aureus infection. The levels of expression of hla and alpha-toxin and total hemolysis did not differ significantly when amoxicillin, gentamicin, or moxifloxacin was added to cultures of S. aureus strain 8325-4. In vivo, strain 8325-4 induced a significantly increased level of hemolysis in infected pouches compared to that in uninfected control pouches, but the hemolysis was reduced to control levels by treatment with doses of amoxicillin, gentamicin, or moxifloxacin that reduced bacterial numbers by 2 orders of magnitude. Additionally, the effects of subinhibitory concentrations of the three antibiotics on total hemolysis of four methicillin-resistant S. aureus and three methicillin-sensitive S. aureus (MSSA) clinical isolates were assessed in vitro. A significant increase in total hemolysis was observed for only one MSSA strain when it was treated with amoxicillin but not when it was treated with moxifloxacin or gentamicin. When purified alpha-toxin was incubated with purified human neutrophil elastase, alpha-toxin was cleaved nearly completely. The results suggest that the penicillin-induced increases in S. aureus alpha-toxin expression are strain dependent, that reduction of bacterial numbers in vivo counteracts this phenomenon effectively, and finally, that in localized S. aureus infections alpha-toxin activity is controlled by neutrophil elastase.

Inflammation in cystic fibrosis and its management

Pulmonary complications are by far the most serious complications in cystic fibrosis (CF). In response to endobronchial bacterial infections, the long-term consequences of chronically activated polymorphonuclear leukocytes (neutrophils) are thought to cause loss of lung function and premature death. Effective anti-inflammatory therapy implies that we understand the complex networks of the immune response with its myriads of mediators on effector cells. We have many steps to go in this context, but science has already shed some light on inflammatory mechanisms in CF airways, and anti-inflammatory treatment strategies have been applied clinically with some success. The aim of this chapter is to review our present knowledge, and we will focus on early inflammation, bacterial persistence mechanisms, neutrophil activation, cytokines and nitric oxide together with anti-inflammatory treatment strategies in CF patients.

MEKC of desmosine and isodesmosine in urine of chronic destructive lung disease patients

Degradation of extracellular matrix components is central to many pathological features of chronic destructive lung disorders. Desmosine and isodesmosine are elastin-derived cross-linked amino acids whose urine levels are considered representative of elastin breakdown. The aim of this study was to apply a novel methodology, based on high-performance capillary electrophoresis, to the quantification of desmosine and isodesmosine in 11 patients with stable chronic obstructive pulmonary disease (COPD), 10 with an exacerbation of COPD, nine with alpha1-antitrypsin deficiency, 13 with bronchiectasis, and 11 adults with cystic fibrosis, in comparison to 24 controls. It was found that, in patients with stable COPD, urinary desmosine levels were higher than in controls (p=0.03), but lower than in COPD subjects with an exacerbation (p< or =0.05). The highest desmosine levels were found in subjects with alpha1-antitrypsin deficiency, bronchiectasis and cystic fibrosis (p<0.001 versus stable COPD). In a short-term longitudinal study, five stable COPD patients showed a constant rate of desmosine excretion (mean coefficient of variation <8% over three consecutive days). In conclusion, the present method is simple and suitable for the determination of elastin-derived cross-linked amino acid excretion in urine, giving results similar to those obtained using other separation methods. In addition, evidence is presented that urinary desmosine excretion is increased in conditions characterized by airway inflammation, such as exacerbations of chronic obstructive pulmonary disease, bronchiectasis and cystic fibrosis. Results obtained in subjects with alphal-antitrypsin deficiency suggest that this method might be used to evaluate the putative efficacy of replacement therapy.

Simultaneous determination of Pseudomonas aeruginosa elastase, human leukocyte elastase and cathepsin G activities by micellar electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) is a new method for analysing proteolytic activities simultaneously present in incubation mixtures. Here we demonstrate that MEKC differentiates between the enzymatic activities of Pseudomonas aeruginosa elastase (PsE) and human leukocyte elastase (HLE) or cathepsin G (Cat G) in assays using the chromogenic peptide substrates Suc-Ala-Ala-Ala-NA or Suc-Ala-Ala-Pro-Phe-NA, respectively (where Suc = succinyl and NA = 4-nitroaniline/u-nitroanilide). When PsE and Cat G were incubated at equimolar ratio with Suc-Ala-Ala-Pro-Phe-NA, the PsE-specific cleavage products PheNA and Suc-Ala-Ala-Pro were detected whereas inhibition of the metalloproteinase PsE with EDTA resulted in detection of NA and Suc-Ala-Ala-Pro-Phe only. Similarly, when PsE and HLE were incubated at equimolar ratio with Suc-Ala-Ala-Ala-NA, the PsE-specific cleavage products Suc-Ala and Ala-Ala-NA were detected whereas at an PsE-HLE ratio 1:50, both the PsE-specific and the HLE-specific cleavage products NA and Suc-Ala-Ala-Ala were separated. MEKC also allowed determination of the kinetic constants for the interactions of PsE, Cat G and HLE with the substrates considered.

Catalase, myeloperoxidase and hydrogen peroxide in cystic fibrosis

An oxidant-antioxidant imbalance with damaging consequences for the bronchial epithelium has been hypothesized in the airways of patients with cystic fibrosis (CF). It is based on the assumption that neutrophils entering the lumen of the infected airways undergo activation and release toxic oxygen metabolites and myeloperoxidase (MPO), an enzyme which transforms hydrogen peroxide (H2O2) into highly toxic oxygen metabolites. Our aims were to substantiate this hypothesis. H2O2 levels were measured in breath condensates of 63 CF patients and 51 normal subjects. In CF sputum samples, activities and concentrations of MPO and catalase (CAT) were determined. MPO/H2O2-mediated cytotoxicity of CF sputum was measured in cell culture assays. H2O2 levels were similar in CF patients and normal subjects (mean +/-SD) 0.97 +/- 0.69 versus 1.11+/-0.78 microM; p=0.427). Concentrations and activities of CAT (0.31+/-0.18 microM; 105+/-69 units) and MPO (5.93+/-4.8 microM; 87.8+/-75 units) were detectable in 38 CF sputa. Addition of H2O2 to in vitro cells preincubated with CF sputum did not induce cytotoxicity even when CAT was removed from sputum. Sputum MPO together with H2O2 did not inactivate alpha-proteinase inhibitor. Preincubation of MPO with sulphated glycoconjugates or deoxyribonucleic acid (DNA) totally inhibited its cytotoxic effect. In conclusion, catalase, sulphated glycoconjugates and deoxyribonucleic acid may prevent myeolperoxidase-mediated oxygen radical generation in cystic fibrosis sputum.

[Regulation of Staphylococcus aureus capsular polysaccharide type 5: in vitro and in vivo inhibition by CO2]

Staphylococcus aureus capsular polysaccharide type 5 (CP5) expression was investigated in lung tissue and nasal polyps of two cystic fibrosis (CF) patients, in rats and in vitro using ELISA and immunofluorescence. In CF tissues, S. aureus expressed protein A and teichoic acid but only 1-5% of cells expressed CP5. When rats were challenged with CP5-positive S. aureus in the granuloma pouch model, only 1-5% CP5-positive cells were detectable in pouch exsudates. CF and pouch isolates, however, re-expressed CP5 (70-90% of cells) when grown in vitro with air. Addition of 1% CO2 or more to air or to O2/N2 gas mixtures reduced CP5 expression significantly (p < 0.001) in a dose-dependent manner (1-6% CP5-positive cells). The results show that S. aureus does not produce CP5 in CF airways and in rat granuloma pouches and that CO2 is an environmental signal which regulates CP5 expression.

Regulation of Staphylococcus aureus capsular polysaccharide type 5: CO2 inhibition in vitro and in vivo

Staphylococcus aureus capsular polysaccharide type 5 (CP5) expression was investigated in lung tissue and nasal polyps of two cystic fibrosis (CF) patients, in rats, and in vitro using ELISA and IFA. In CF tissues, S. aureus expressed protein A and teichoic acid but only 1%-5% of cells expressed CP5. When rats were challenged with CP5-positive S. aureus in the granuloma pouch model, only 1%-5% of CP5-positive cells were detectable in pouch exudates. CF and pouch isolates, however, reexpressed CP5 (70%-90% of cells) when grown in vitro with air. Addition of > or = 1% CO2 to air or to O2/N2 gas mixtures reduced CP5 expression significantly (P < .001) in a dose-dependent manner (6%-1% CP5-positive cells). The results show that S. aureus does not produce CP5 in CF airways and in rat granuloma pouches and that CO2 is an environmental signal that regulates CP5 expression.

[Reactive oxygen species and arachidonic acid metabolites of polymorphonuclear leukocytes]

The activation of polymorphonuclear leukocytes by stimulants from host or parasites leads to various metabolic processes and to enhanced oxygen uptake. Oxygen is enzymatically processed to from reactive oxygen compounds and metabolites of arachidonic acid which are involved in killing of microbial pathogens and influence many processes in inflammation. Their activities are regulated intracellularly by antioxidants. A lack or exhaustion of these systems may lead to cell and organ damage in which DNA, proteins, lipids and sugars may be involved. Antioxidants and inhibitors of the arachidonic acid metabolism are applied to reduce these pathological changes. An essential aspect of microbial pathogenicity is the multifold modification of the formation of reactive oxygen compounds and arachidonic acid metabolites.

Molecular epidemiology of Pseudomonas aeruginosa--urinary tract infections in paraplegic patients

84 Pseudomonas aeruginosa strains from 29 paraplegic patients with urinary tract infections (UTI) and from the water reservoirs of specialized wards in two German hospitals were typed using a P. aeruginosa-specific DNA probe. P. aeruginosa strains were present in 51% of all accessible water reservoirs, including sinks of wash-basins and toilets in the wards. 14 of the 29 patients with UTI (48%) were infected by P. aeruginosa strains which were also isolated from these sources. Groups of up to four patients were infected by single strains. Some of the strains persisted in the wards and were isolated from the water reservoirs five to eight months after causing UTI. 89.5% of the investigated water samples yielded P. aeruginosa strains which were identical with strains from up to nine other sites. The wide distribution of single P. aeruginosa genotypes in the ward, the isolation of strains causing UTI from rooms inaccessible to the patients, and the outbreak of UTI caused by single, identical P. aeruginosa strains in groups of patients within short time periods, suggest that the strains are distributed by the personnel rather than by the patients who for the most part are immobile.