Microbiology of chronic rhinosinusitis

Most sinus infections are viral and only a small percentage develop bacterial infection. Rhino-, influenza, and para-influenza viruses are the most frequent viral causes of sinusitis. The most common bacterial isolates from children and adult patients with community-acquired acute bacterial sinusitis are Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pyogenes. Staphylococcus aureus and anaerobic organisms (Prevotella and Porphyromonas, Fusobacterium, and Peptostreptococcus spp.) are the commonest isolates in chronic rhinosinusitis (CRS). Aerobic and anaerobic beta lactamase-producing bacteria (BLPB) were recovered from over a third of these patients. Methicillin-resistant S. aureus (MRSA) accounted for over 60 % of S. aureus isolates. Pseudomonas aeruginosa and other aerobic and facultative Gram-negative rods are frequently recovered in nosocomial sinusitis, the immunocompromised host, individuals with human immunodeficiency virus infection, and in cystic fibrosis. The CRS infection evolves the formation of a biofilm that might play a significant role in the pathogenesis and persistence of CRS. The microbiology of sinusitis is influenced by previous antimicrobial therapy, vaccinations, and the presence of normal flora capable of interfering with the growth of pathogens. Recognition of the unique microbiology of CRS and their antimicrobial susceptibility is of great importance when selecting antimicrobial therapy.     

Novel diagnostic ELISA test for discrimination between infections with <Emphasis Type="Italic">Yersinia enterocolitica</Emphasis> and <Emphasis Type="Italic">Yersinia pseudotuberculosis</Emphasis>

Yersiniosis is a foodborne infection caused by Yersinia enterocolitica or Yersinia pseudotuberculosis. Although yersiniosis is most often self-limiting, some patients develop chronic infections, such as reactive arthritis, glomerulonephritis, or myocarditis, which require an antibiotic treatment. Whereas early infections can be diagnosed by direct detection of bacteria, chronic infections can only be identified by serological tests. At this point, a serological method for differentiation between infections with the two Yersinia species is important since antibiotic susceptibility of these bacteria is different. Traditional immunoassays do not distinguish between infections with Y. enterocolitica and Y. pseudotuberculosis. The only test that allows for this differentiation is Mikrogen’s strip test where discrimination between the two types of infection is based on two recombinant bacterial proteins, MyfA and PsaA (specific for Y. enterocolitica and Y. pseudotuberculosis, respectively). Here, we show that Y. enterocolitica and Y. pseudotuberculosis, cultured under the conditions that mimic the natural rout of infection, express surface antigens different from MyfA and PsaA that can also be used in a discrimination test. Further, we describe a new ELISA that is based on the whole bacteria and recombinant MyfA and PsaA as antigens, and that allows the differentiation between infections with Y. enterocolitica and Y. pseudotuberculosis and simultaneous detection of yersiniosis.     

The ArlRS two-component system is a regulator of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>-induced endothelial cell damage

Staphylococcus aureus endovascular infections retain a high morbidity and mortality despite antibiotics and supportive care. The destruction of endothelial cells (ECs) is a critical step in the pathogenesis of S. aureus endovascular infections. In order to better understand S. aureus-induced EC damage, we systematically screened a collection of two-component regulatory system mutants of methicillin-resistant S. aureus (MRSA) USA300 strain JE2 for damage induction in human umbilical vein ECs (HUVECs). This screen revealed that the two-component regulatory system ArlRS is required for maximum damage: arlRS inactivation leads to a > 70% reduction in damage. In a different genetic S. aureus background (RN6390, MSSA strain) arlRS inactivation had a smaller but also significant effect on EC damage. In both strains, the reduction in EC damage was accompanied by a significant reduction in internalization. In conclusion, we determined a novel role of ArlRS in S. aureus-induced EC damage, which will help to better understand the pathogenesis of S. aureus endovascular infection.     

Monitoring of abdominal<Emphasis Type="Italic"> Staphylococcus aureus</Emphasis> infection using magnetic resonance imaging: a murine animal model for hepatic and renal abscesses

To establish a routine workflow for in vivo magnetic resonance imaging (MRI) of mice infected with bacterial biosafety level 2 pathogens and to generate a mouse model for systemic infection with Staphylococcus aureus suitable for monitoring by MRI. A self-contained acrylic glass animal bed complying with biosafety level 2 requirements was constructed. After intravenous infection with 10⁵ colony-forming units (CFU) (n?=?3), 10⁶ CFU (n?=?11) or 10⁷ CFU (n?=?6) of S. aureus strain Newman, female Balb/c mice were whole-body scanned by 7T MRI. Abdominal infections such as abscesses were visualized using a standard T2-weighted scan. Infection monitoring was performed for each animal by measurements at 1, 3, and 7 days after infection. Intravenous pathogen application led to a dose-dependent decrease in survival probability (p?=?0.03). In the group with the highest infectious dose the 7-day survival rate was 33 %. An intermediate S. aureus dose showed a survival rate of 80 %, whereas at the lowest infection dose, none of the animals died. All animals with the highest infection dose exhibited hepatic abscesses 4 days after inoculation, 80 % developed renal abscesses on the 3rd day. Mice obtaining the intermediate S. aureus load reached a plateau at day 4 with 72 % liver and 60 % renal abscess probability. No abscesses were observed in other abdominal organs at any time point. The implemented experimental setup provides a suitable and reliable in vivo MRI method to study murine abdominal infection models using BSL-2 pathogen. Systemic Staphylococcus aureus infection leads to a dose-dependent development of hepatic and renal abscesses.     

The ability of various strains of <Emphasis Type="Italic">Staphylococcus</Emphasis> to create biofilms and their effect on cells of the human body

Research on staphylococci research is important because of their ability to cause such severe infections as soft tissue infections, endocarditis, sepsis, toxic shock syndrome, and food poisoning. Coagulase-positive Staphylococcus aureus is the main infection agent of intrahospital infections. This agent has many factors of pathogenicity, which are well known. Among the coagulase-negative staphylococcus (CNS) strains, S. haemolyticus and S. epidermidis are clinically important, because they cause infections in patients with weakened immune system. The mechanisms of the CNS pathogenicity are understood insufficiently. The goal of this work was to evaluate the potential pathogenicity of clinical CNS strains based on their capacity to form biofilms and their character of interaction with the human cells through an example of HT-29 cell culture. The research was carried out on the laboratory strain S. aureus ATCC 29213 and clinical strains S. haemolyticus SH39 and S. epidermidis SE 36-1, which were isolated from neonatal autopsy materials. The visual tests of biofilm formation by each strain and testing the impact of the strains on HT-29 cell culture were carried out in this work. Two CNS species form biofilms with a higher rate than S. aureus. Upon incubation for 2 h of HT-29 cells with the staphylococcus strains tested in this work, adhesion of bacteria on the cells’ surfaces was observed. The adhesion was most pronounced in the case of S. aureus ATCC 29213 and S. haemolyticus SH39. Upon 3 h of incubation with S. aureus ATCC 29213 and S. haemolyticus SH39, the destruction of a monolayer of HT-29 cells was observed. The incubation for 24 h with three strains tested in this work caused the complete destruction of the monolayer of HT-29 cells. The maximal toxic effect on HT-29 cells was inherent in S. haemolyticus SH39 strain. The cumulative results obtained in this work indicate the presence of the pathogenicity factors in S. haemolyticus SH39 strain, and their molecular nature needs to be researched further.     

Toe web intertrigo in Kaposi’s sarcoma patients: a microbiological study in a large cohort of patients

Kaposi ‘s sarcoma (KS) is a rare multifocal angioproliferative disease associated with human herpes virus 8 (HHV-8) infection, characterized by cutaneous nodules or plaques especially on the lower limbs. Some skin modifications, such as chronic lymphedema, plantar hyperkeratosis and interdigital desquamation, may be associated with consequent impairment of the local immunosurveillance and increased risk of some bacterial or mycotic infections. With the objective of evaluating if bacterial or mycotic infections in KS patients are supported by different microorganisms compared to control patients, we performed an observational retrospective study, comparing positive cultural swabs of interdigital intertrigo of KS patients with positive cultural swabs of interdigital intertrigo of patients admitted to our dermatologic unit during the last 10 years. One hundred KS patients and 84 control patients were admitted to this study. Some of the skin swabs from interdigital spaces were positive for more than one microorganism, and therefore we found 187 microorganisms among the KS group and 182 microorganisms in the control group. The most common microrganisms among KS patients were T. mentagrophytes (16%), S. aureus (14.9%), P. aeruginosa (13.9%), S. marcescens (5,9%), while among non-KS patients were S. aureus (26,9%), C. albicans (22%), S. agalactiae (7.7%) and E. coli (9.9%). These differences are statistically significant (p < 0.01). KS patients may be more affected by toe web intertrigo due to other bacteria and dermatophytes than the general population. During clinical examination, a careful inspection is necessary for an early diagnosis of toe web intertrigo, in order to prevent serious complications, such as cellulitis and sepsis. Consequently, a cultural examination with antibiogram is required to identify the causative agent of intertrigo and guide antimicrobial therapy.     

Chronic and Invasive Fungal Infections in a Family with CARD9 Deficiency

Chronic mucocutaneous or invasive fungal infections are generally the result of primary or secondary immune dysfunction. Patients with autosomal recessive CARD9 mutations are also predisposed to recurrent mucocutaneous and invasive fungal infections with Candida spp., dermatophytes (e.g. Trichophyton spp.) and phaeohyphomycetes (Exophiala spp., Phialophora verrucosa). We study a consanguineous family of Turkish origin in which three members present with distinct clinical phenotypes of chronic mucocutaneous and invasive fungal infections, ranging from chronic mucocutaneous candidiasis (CMC) in one patient, treatment-resistant cutaneous dermatophytosis and deep dermatophytosis in a second patient, to CMC with Candida encephalitis and endocrinopathy in a third patient. Two patients consented to genetic testing and were found to have a previously reported homozygous R70W CARD9 mutation. Circulating IL-17 and IL-22 producing T cells were decreased as was IL-6 and granulocyte/macrophage colony–stimulating factor (GM-CSF) secretion upon stimulation with Candida albicans. Patients with recurrent fungal infections in the absence of known immunodeficiencies should be analyzed for CARD9 gene mutations as the cause of fungal infection predisposition.     

The nasopharyngeal microbiota in patients with viral respiratory tract infections is enriched in bacterial pathogens

The nasopharynx is the primary site of colonization by respiratory pathogen that constitutes the port of entrance in the respiratory tract. The role of mucosal respiratory microbiota in infection has been recently emphasized; therefore, we aimed to assess if a specific respiratory microbiota profile was associated with symptomatic infection and/or with presence of respiratory viruses. We performed a case-control study to characterize the healthy respiratory microbiota and its alteration during acute viral infections. Next-generation sequencing of the 16S rRNA gene was applied to 225 nasopharyngeal samples from 177 patients with viral respiratory infection and 48 matched healthy controls. We evidenced an important decrease of bacterial alpha-diversity in patients with symptomatic respiratory infection and a loss of the healthy core microbiota, specifically anaerobes and Prevotella spp. Moreover, eight respiratory pathogens were enriched in these patients, including Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Dol osigranulum pigrum and Corynebacterium propinquum/pseudodiphtheriticum, whose role in respiratory infection is unclear. The asymptomatic carrier of influenza harbors a microbiota similar to healthy subjects, suggesting a critical role of microbiota in the clinical expression of viruses. These data suggest that the commensal microbiota plays a significant role in susceptibility to viral infection. The frequent co-detection of virus and bacteria raises the question of a strategy to prevent bacterial disease, focusing on the prevention of nasopharyngeal colonization through effective antibiotic treatment. In addition to antibiotics, further studies should test preventive or therapeutic interventions for maintaining or restoring a healthy nasopharyngeal microbiota.     

Population-based epidemiology of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> bloodstream infection: clonal complex 30 genotype is associated with mortality

Staphylococcus aureus bloodstream infections (SABSI) are associated with a high burden of morbidity and mortality. The impact of specific S. aureus genotypes on outcome is unclear. The aim of this study was to evaluate the epidemiology and outcome of SABSI, with a special emphasis on the impact of bacterial clonal lineage on mortality. We conducted a 3-year population-based prospective study between 2011 and 2014, including 303 consecutive adult patients. Clinical data were obtained from interviews and medical records. S. aureus isolates were genotyped using DNA microarrays. The incidence rate of SABSI was 27.6 per 100,000 inhabitants [95 % confidence interval (CI) 24.6–31.0]. The median age of the patients was 71 years (interquartile range 56–81 years) and 61.4 % were male. Most SABSI (70.6 %) occurred in hospitals or associated to healthcare, and 34.1 % of these were associated with intravascular catheters. Only five (1.6 %) SABSI were caused by methicillin-resistant S. aureus (MRSA). The 30-day case fatality rate was 20.8 % (95 % CI 16.6–25.7). S. aureus clonal complex 30 [hazard ratio (HR) 3.9; 95 % CI 1.8–8.5, p?=?0.001], unknown focus of infection (HR 4.5; 95 % CI 1.9–10.8, p?=?0.001) and respiratory tract infection (HR 12.7; 95 % CI 4.6–34.6, p?<?0.001) were independent predictors of mortality in a Cox regression analysis after adjusting for age, sex and underlying conditions. A high proportion of potential preventable SABSI calls for effective infection control measures. S. aureus clonal complex 30 genotype was associated with mortality in patients with bloodstream infections. The genetic basis underlying this association remains to be demonstrated.     

Household aggregation of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by clonal complex and methicillin resistance profiles in Starr County,Texas

Staphylococcus aureus is one of the most common causes of skin and soft tissue infections in health-care and community settings, but transmission of S. aureus in community-based populations is incompletely understood. S. aureus carriage phenotypes (persistent, intermittent, and non-carriers) were determined for households from Starr County, TX. Nasal swabs were collected from a cohort of 901 residents and screened for the presence of S. aureus. Isolated strains were spa-typed and assigned to clonal complexes. Of the 901 participants there were 134 pairs, 28 trios, 11 quartets, 3 quintets and 1 septet residing in the same household. There was a significant increase in “ever” carriers (persistent and intermittent carriers combined) in these households over that expected based on population frequencies (p = 0.029). There were 42 ever carrier pairs of individuals with 21 concordant for clonal complex type whereas only 4.7 were expected to be so (p = 6.9E-11). These results demonstrated clear aggregation of S. aureus carriage and concordance for strain types within households. As antibiotic-resistant S. aureus strains increase in community settings, it is important to better understand risk factors for colonization, mechanisms of transmission, clonal complexes present, and the role of household concordance/transmission.     

Etiologies,risk factors,and outcomes of bacterial cholangitis after living donor liver transplantation

The interpretation of bacterial cholangitis after liver transplantation (LT) remains vague, because the presence of bacteria in bile, namely bacteriobilia, does not necessarily indicate an active infection. We investigated the association between post-LT bacterial cholangitis and a variety of short- and long-term outcomes. Two-hundred-seventy-four primary adult-to-adult living donor LT recipients from 2008 to 2016 were divided into three groups according the presence or absence of bacteriobilia and clinical symptoms: (1) no bacteriobilia (N group), (2) asymptomatic bacteriobilia (B group), and (3) cholangitis (C group). The number of patients was by group: N, 161; B, 64; and C, 49. Donor age ≥?45 years (p?=?0.012), choledochojejunostomy (p?<?0.001), and post-LT portal hypertension (p?=?0.023) were independent risk factors for developing cholangitis. Survival analysis revealed that the C group had significantly worse short- and long-term graft survival. The C group was associated with an increased incidence of early graft loss (EGL) (p?<?0.001). While the frequency of readmission for recurrent cholangitis was significantly higher in both the B and C groups (p?<?0.001), late graft loss (LGL) due to chronic cholangitis was only commonly observed in the C group (p?=?0.002). Post-LT cholangitis could result in not only EGL but also chronic cholangitis and associated LGL.     

Reduced pro-inflammatory responses to <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> bloodstream infection and low prevalence of enterotoxin genes in isolates from patients on haemodialysis

Patients with end-stage renal failure undergo regular haemodialysis (HD) and often develop episodes of Staphylococcus aureus bloodstream infection (BSI), which can re-occur. However, clinically, patients on HD, with S. aureus BSI, respond well to treatment, rarely developing overt signs of sepsis. We investigated the contributions of bacterial virulence and cytokine responses to the clinical course of S. aureus BSI in HD and non-HD patients. Seventy patients were recruited, including 27 (38.6 %) patients on HD. Isolates were spa-typed and virulence and antimicrobial resistance gene carriage was investigated using DNA microarray analysis. Four inflammatory cytokines, IL-6, RANTES, GROγ and leptin, were measured in patient plasma on the day of diagnosis and after 7 days. There was no significant difference in the prevalence of genotypes or antimicrobial resistance genes in S. aureus isolates from HD compared to non-HD patients. The enterotoxin gene cluster (containing staphylococcal enterotoxins seg, sei, sem, sen, seo and seu) was significantly less prevalent among BSI isolates from HD patients compared to non-HD patients. Comparing inflammatory cytokine response to S. aureus BSI in HD patients to non-HD patients, IL-6 and GROγ were significantly lower (p?=?0.021 and p?=?0.001, respectively) in HD patients compared to other patients on the day of diagnosis and RANTES levels were significantly lower (p?=?0.025) in HD patients on day 7 following diagnosis. Lowered cytokine responses in HD patients and a reduced potential for super-antigen production by infecting isolates may partly explain the favourable clinical responses to episodes of S. aureus BSI in HD patients that we noted clinically.     

Molecular aspects of <Emphasis Type="Italic">Brucella</Emphasis> persistence

Brucellosis is an extremely dangerous zoonotic infectious disease of animals and human beings. It is caused by bacteria of the genus Brucella capable of surviving, reproducing, and persisting in host cells. The present review deals with the persistence of Brucella, with a focus on the molecular mechanisms that underlie the avoidance of innate and adaptive immunity systems of the host by the bacteria and the active interference of type IV effector proteins secreted by Brucella with host cell functions. Understanding of the molecular mechanisms of Brucella persistence may assist the search for new approaches to the development of effective means for the prevention and treatment of chronic brucellosis.     

<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> colonization related to severity of hand eczema

Knowledge on Staphylococcus aureus colonization rates and epidemiology in hand eczema is limited. The aim of this study was to clarify some of these issues. Samples were collected by the “glove juice” method from the hands of 59 patients with chronic hand eczema and 24 healthy individuals. Swab samples were taken from anterior nares and throat from 43 of the 59 patients and all healthy individuals. S. aureus were spa typed and analysed by DNA-microarray-based genotyping. The extent of the eczema was evaluated by the hand eczema extent score (HEES). The colonization rate was higher on the hands of hand eczema patients (69 %) compared to healthy individuals (21 %, p?<?0.001). This was also seen for bacterial density (p?=?0.002). Patients with severe hand eczema (HEES?≥?13) had a significantly higher S. aureus density on their hands compared to those with milder eczema (HEES?=?1 to 12, p?=?0.004). There was no difference between patients and healthy individuals regarding colonization rates in anterior nares or throat. spa typing and DNA-microarray-based genotyping indicated certain types more prone to colonize eczematous skin. Simultaneous colonization, in one individual, with S. aureus of different types, was identified in 60–85 % of the study subjects. The colonization rate and density indicate a need for effective treatment of eczema and may have an impact on infection control in healthcare.     

Association of diverse bacterial communities in human bile samples with biliary tract disorders: a survey using culture and polymerase chain reaction-denaturing gradient gel electrophoresis methods

Bacterial infection is considered a predisposing factor for disorders of the biliary tract. This study aimed to determine the diversity of bacterial communities in bile samples and their involvement in the occurrence of biliary tract diseases. A total of 102 bile samples were collected during endoscopic retrograde cholangiopancreatography (ERCP). Characterization of bacteria was done using culture and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) methods. Antimicrobial susceptibility of the isolates was determined based on the Clinical and Laboratory Standards Institute (CLSI) guidelines and identity of the nucleotide sequences of differentiated bands from the DGGE gels was determined based on GenBank data. In total, 41.2 % (42/102) of the patients showed bacterial infection in their bile samples. This infection was detected in 21 % (4/19), 45.4 % (5/11), 53.5 % (15/28), and 54.5 % (24/44) of patients with common bile duct stone, microlithiasis, malignancy, and gallbladder stone, respectively. Escherichia coli showed a significant association with gallstones. Polymicrobial infection was detected in 48 % of the patients. While results of the culture method established coexistence of biofilm-forming bacteria (Pseudomonas aeruginosa, E. coli, Klebsiella pneumoniae, Enterococcus spp., and Acinetobacter spp.) in different combinations, the presence of Capnocytophaga spp., Lactococcus spp., Bacillus spp., Staphylococcus haemolyticus, Enterobacter or Citrobacter spp., Morganella spp., Salmonella spp., and Helicobacter pylori was also characterized in these samples by the PCR-DGGE method. Multidrug resistance phenotypes (87.5 %) and resistance to third- and fourth-generation cephalosporins and quinolones were common in these strains, which could evolve through their selection by bile components. Ability for biofilm formation seems to be a need for polymicrobial infection in this organ.     

Reduction in fecal microbiota diversity and short-chain fatty acid producers in Methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> infected individuals as revealed by PacBio single molecule,real-time sequencing technology

Methicillin-resistant Staphylococcus aureus (MRSA) may cause potentially lethal infections. Increasing evidence suggests that the gut microbiota is associated with human health. Yet, whether patients with MRSA infections carry specific signatures in their fecal microbiota composition has not been determined. Thus, this study aimed to compare the fecal microbiota profile of MRSA-positive patients (n=15) with individuals without MRSA infection (n=15) by using the PacBio single molecule, real-time (SMRT) DNA sequencing system and real-time quantitative polymerase chain reaction (qPCR). Mann-Whitney tests and unweighted UniFrac principal coordinate analysis (PCoA) showed that the profile of fecal microbiota was apparently different between the two populations. Both the community richness and diversity were reduced in the MRSA-positive group (p<0.050). The genera Acinetobacter and Enterococcus were highly enriched in the MRSA-positive group, whereas less short-chain fatty acid (SCFA)-producing bacteria, including Butyricimonas, Faecalibacterium, Roseburia, Ruminococcus, Megamonas and Phascolarctobacterium, were detected in the MRSA-positive group. At species level, the species Acinetobacter baumannii and Bacteroides thetaiotaomicron were prevalent in the MRSA-positive group, whereas opposite trends were observed in 17 other species, such as Faecalibacterium prausnitzii, Lactobacillus rogosae, Megamonas rupellensis and Phascolarctobacterium faecium. Positive correlations were observed between Acinetobacter baumannii and erythrocyte sedimentation rate (ESR) (R=0.554, p=0.001), as well as hypersensitive C reactive protein (hsCRP) (R=0.406, p=0.026). Faecalibacterium prausnitzii was negatively associated with ESR (R=-0.545, p=0.002), hsCRP (R=-0.401, p=0.028) and total bile acids (TBA) (R=-0.364, p=0.048). In conclusion, the fecal microbiota structure was different between MRSA-positive and -negative patients. The increase in potential pathogens with the reduction of beneficial populations, such as SCFA-producing bacteria, in MRSA-positive patients may affect prognosis.     

Initial Host Response to Bacteria in the Murine Lung Differs Between <Emphasis Type="BoldItalic">Pseudomonas aeruginosa</Emphasis>, <Emphasis Type="BoldItalic">Staphylococcus aureus</Emphasis> and <Emphasis Type="BoldItalic">Streptococcus pneumoniae</Emphasis>

Phagocytosis of bacteria is an important process during early host defence. It has been directly observed only ex vivo or in vitro. Here, we report on the observation of phagocytosis under in vivo conditions by using intravital microscopy in the murine lung. Suspensions of fluorescently labelled Streptococcus pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa cells were each instilled intratracheally to anaesthetized mice. After thoracotomy, the alveolar surface was observed for 30 min. Alveolar phagocytes exhibiting ingested bacteria could be detected and counted. The highest numbers were found after the infection with P. aeruginosa. By using intravital microscopy, cellular host defence could be observed in living mice lungs. The initial phagocytic reaction crucially depends on the species of applied bacteria invading the lung.     

DNA microarray analysis of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> causing bloodstream infection: bacterial genes associated with mortality?

Providing evidence for microbial genetic determinants’ impact on outcome in Staphylococcus aureus bloodstream infections (SABSI) is challenging due to the complex and dynamic microbe–host interaction. Our recent population-based prospective study reported an association between the S. aureus clonal complex (CC) 30 genotype and mortality in SABSI patients. This follow-up investigation aimed to examine the genetic profiles of the SABSI isolates and test the hypothesis that specific genetic characteristics in S. aureus are associated with mortality. SABSI isolates (n?=?305) and S. aureus CC30 isolates from asymptomatic nasal carriers (n?=?38) were characterised by DNA microarray analysis and spa typing. Fisher’s exact test, least absolute shrinkage and selection operator (LASSO) and elastic net regressions were performed to discern within four groups defined by patient outcome and characteristics. No specific S. aureus genetic determinants were found to be associated with mortality in SABSI patients. By applying LASSO and elastic net regressions, we found evidence suggesting that agrIII and cna were positively and setC (=selX) and seh were negatively associated with S. aureus CC30 versus non-CC30 isolates. The genes chp and sak, encoding immune evasion molecules, were found in higher frequencies in CC30 SABSI isolates compared to CC30 carrier isolates, indicating a higher virulence potential. In conclusion, no specific S. aureus genes were found to be associated with mortality by DNA microarray analysis and state-of-the-art statistical analyses. The next natural step is to test the hypothesis in larger samples with higher resolution methods, like whole genome sequencing.     

In vitro antibacterial effects of statins against bacterial pathogens causing skin infections

With financial considerations impeding research and development of new antibiotics, drug repurposing (finding new indications for old drugs) emerges as a feasible alternative. Statins are extensively prescribed around the world to lower cholesterol, but they also possess inherent antimicrobial properties. This study identifies statins with the greatest potential to be repurposed as topical antibiotics and postulates a mechanism of action for statins’ antibacterial activity. Using broth microdilution, the direct antibacterial effects of all seven parent statins currently registered for human use and three selected statin metabolites were tested against bacterial skin pathogens Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Serratia marcescens. Simvastatin and pitavastatin lactone exerted the greatest antibacterial effects (minimum inhibitory concentrations of 64 and 128 μg/mL, respectively) against S. aureus. None of the statins tested were effective against E. coli, P. aeruginosa, or S. marcescens, but simvastatin hydroxy acid acid might be active against S. aureus, E. coli, and S. marcescens at drug concentrations >?256 μg/mL. It was found that S. aureus may exhibit a paradoxical growth effect when exposed to simvastatin; thus, treatment failure at high drug concentrations is theoretically probable. Through structure-activity relationship analysis, we postulate that statins’ antibacterial action may involve disrupting the teichoic acid structures or decreasing the number of alanine residues present on Gram-positive bacterial cell surfaces, which could reduce biofilm formation, diminish bacterial adhesion to environmental surfaces, or impede S. aureus cell division.     

Differences in humoral immune response between patients with or without nasal carriage of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

The humoral immune response against 43 staphylococcal antigens was compared among hospitalized patients where none of them had any staphylococcal infection on the day of admission with or without nasal Staphylococcus aureus carriage. Fifty-nine carriers and 59 matched non-carriers were studied. The carriers harbored S. aureus of 35 different spa types, including three t037/ST239 methicillin-resistant S. aureus (MRSA) (5.1%). Among the 118 patients, 31 acquired S. aureus during hospitalization. In colonized and non-colonized patients, unique patterns of S. aureus-specific immune responses were observed. The mean fluorescence indices (MFIs) of antibodies against 36/43 (83.7%) antigens were seen to be elevated among carriers. The MFI among carriers with acquisition was significantly higher for staphylococcal superantigen-like protein 5 (SSL5, p?=?0.028) when compared to carriers without acquisition. High antibody levels against staphylococcal enterotoxin A (SEA) among carriers illustrate its role as a superantigen in both infection and colonization. We also report a dynamic immune response in S. aureus-carrying patients against the recently reported formyl peptide receptor-like inhibitory (FLIPr)-like protein. In the current study, the dynamics of antibodies against staphylococcal antigens among carrier patients seem quite similar to non-carrier patients. To better understand the dynamic immunogenicity during S. aureus infection and colonization, artificial colonization studies and investigation of the changes in the levels of antibodies against other staphylococcal antigens are recommended.