BackgroundWhile recognizing the etiology of community-acquired pneumonia is necessary for formulating local antimicrobial guidelines, limited data is published about this etiology in Egyptian pediatric patients.ObjectivesTo determine the frequency of bacterial and viral pathogens causing community-acquired pneumonia (CAP) among immunocompetent Egyptian infants and preschool children.MethodsNinety infants and preschool-age children admitted to our hospital with CAP were prospectively included in the study. Etiological agents were identified using conventional bacteriological identification methods and IgM antibodies detection against common atypical respiratory bacteria and viruses.ResultsAn etiology was identified in 59 patients (65.5%). Bacterial pathogens were detected in 43 (47.8%) of the cases while viral pathogens were detected in 23 (25.5%). Coinfection with more than one etiologic agent was evident in seven patients (7.8%). The most common typical bacterial cause of pneumonia was Staphylococcus aureus (n = 12, 13.3%), followed by Streptococcus pneumoniae and Klebsiella pneumoniae (n = 7, 7.8%, each). The commonest atypical bacterium was Mycoplasma pneumoniae (n = 10, 11.1%), whereas the commonest viral etiology was influenza viruses (n = 11, 12.2%).ConclusionAlthough we could not determine the causative agent in some studied cases, this study provides preliminary data regarding the spectrum and frequency of microorganisms causing CAP in Egyptian infants and preschool children.

95 cases itself. A number of significant discrepancies emerged between the re-analysis and the findings reported in the paper both in terms of means and standard deviations of key outcome variables across the trial. These involved very substantial differences that we judged to be extremely unlikely to have arisen due to variations in composition of the original and re-analysed samples. We also discovered previously unidentified/reported problems with missing data and recording irregularities regarding changes in treatment regimen and subject identifiers.

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Among 50 strains of Pseudomonas aeruginosa tested for the resistance to antibiotics, strain ryn32 was selected for this study based on its resistance level. It showed complete resistance toward aztreonam and almost complete resistance (96%) against kanamycin. Iron nanoparticles (FeNPs) were then prepared and found with diameters 30-50 nm. The threshold level of FeNPs for pyoverdines (PVDs) production by P. aeruginosa ryn32 was found at 25 μM concentration. PVDs production was optimal with pH 7.5, 35 C, succinate as carbon source, ammonium sulfate as nitrogen source at 60 hr fermentation time. Interestingly, when used the PVDs as conjugates with FeNPs they showed antibacterial action against the producing strain and some other gram-negative bacteria. This suggests that the conjugates enter the bacterial cell via the ferriPVDs uptake pathway, which triggers the accumulation of FeNPs inside the cell, which is crucial on bacterial viability. Growth stimulation with the same concentrations of FeNPs and PVDs in separate treatments supported this view. K E Y W O R D S antimicrobials, iron nanoparticles, Pseudomonas aeruginosa, pyoverdine, siderophore 1 | INTRODUCTION Pseudomonas aeruginosa is one of the most known bacterial pathogens in human history. As an inhabitant of soil, it is frequently found in air from which it may gain access to humans and animals. It is well established as a potential opportunistic pathogen, especially in hospitals. The problem is much complicated by their resistance to most antibiotics and many disinfectants with the subsequent emergence of new resistant strains. 1 The treatment of these resistant strains becomes a challenge. The resistance of P. aeruginosa may due to the presence of alginate biofilm, the low permeability of the outer membrane, the active export of low molecular weight drugs and the production of β-lactamases. 2The pathogenicity of P. aeruginosa is linked with its ability to produce siderophores to attain Fe 3+ ions from the human body. 3 Iron is the most required trace element in the metabolism of bacteria making it a crucial basis of environmental struggle. To manage irondeficient conditions, bacteria secrete siderophores into the environment. These low molecular mass (usually lower than 2 kD) molecules chelate the insoluble iron present in the surrounding. Iron is then set free by the metallo-reductases at the periplasmic space and be taken up via siderophore receptors located on the bacterial cell membrane. 4

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