The emergence and rapid spread of methicillin-resistant Staphylococcus aureus (MRSA) isolates in the world significantly complicated the treatment and changed the approaches to the diagnosis of staphylococcal infections in children. Staphylococcus aureus is a widespread microorganism dangerous for humans. A wide range of virulence factors the list of which is still being added allows it to quickly enter the body through damaged barriers and cause local and invasive infections, toxin-mediated diseases, as well as persist for a long time. Currently, two fundamentally different variants of MRSA are distinguished: health care-associated and community-acquired. Health care-associated MRSA are resistant to a greater number of antimicrobial agents, while community-acquired MRSA isolates are characterized by recurrent infections and a more severe course of invasive diseases. In addition, MRSA is gradually developing resistance to those antibacterial agents that were the basis of treatment for these infections, primarily clindamycin and vancomycin. All this requires global and regional monito­ring of MRSA spread in different variants of staphylococcal infections and the sensitivity of the isolates found to antibiotics in order to optimize empiric and pathogen-specific antibacterial therapy. The article presents data on the activity of various antimicrobial agents against S.aureus, analyzes the available information on the prevalence of MRSA in Ukraine and the results of local monitoring for antibiotic resistance, which turned out to be unidirectional with global trends. Clinical and laboratory criteria for diagnosis of local staphylococcal infections, invasive and toxin-mediated diseases in childhood were presented. Treatment of S.aureus infections involves the necessary surgical interventions and antibacterial therapy considering current epidemiological situation on the spread of MRSA and their sensitivity to antimicrobial agents. Further studies are needed to determine the prevalence of MRSA in children in Ukraine to develop antibacterial therapy algorithms for various types of staphylococcal infections.

Background. Atypical hemolytic uremic syndrome (aHUS) is an extremely rare but life-threatening di­s­order in children since it may cause acute kidney injury. Patients with aHUS are at risk of recurrence. Hence, in this paper, we present a case of a 9-year-old boy with aHUS relapse. The child was admitted to the emergency department on the fifth day of illness with main complaints of facial puffiness and decreased urine output. Based on the medical history, the patient developed the second episode of aHUS after 6 years of complete recovery from the first episode. There was no preceding diarrheal illness, instead, the clinical manifestation of both aHUS episodes was triggered by a respiratory tract infection. The results of diagnostic studies performed during the first episode of aHUS were as follows: stool tests for Esche­richia coli and Shiga toxins were negative; a complement assay showed no abnormalities; ADAMTS13 activity and anti-complement factor H antibodies were normal. The results of the kidney ultrasonography and biopsy were consistent with the diagnosis. Family history was remarkable for aHUS in a younger sibling confirmed by molecular genetic testing, in particular, a pathogenic variant in the CD46/MCP (membrane cofactor protein) gene in the heterozygous state has been identified. Physical examination revealed paleness, facial swelling, moderate hypertension, and oliguria. Laboratory findings demonstrated hemolytic anemia, thrombocytopenia, significant azotemia, a severe reduction in the glomerular filtration rate, a high level of aspartate aminotransferase, insignificant electrolyte imbalance, and proteinuria. Supportive treatment included fluid and electrolyte management, fresh frozen plasma, furosemide, and dexamethasone. The child commenced acute hemodialysis due to severe acute kidney injury. Conclusions. A recurrence of aHUS is characterized by severe renal failure requiring acute hemodialysis. Viral infections are potential triggers of aHUS. A relapsing course of the disease and a family history of aHUS indicate the importance of genetic screening, as familial aHUS should be considered.