ABSTRACT
Hypervirulent Klebsiella pneumoniae (hvKp) can cause infections in clinically healthy people, such as young and immunocompetent patients. Genes involved in the capsule synthesis or those encoding the siderophores have been adopted as predictors of hvKp. Certain sequence types, such as ST23 and ST86, have been associated with hvKp strains, too. The aim of this study was to investigate the presence of hvKp among 354 K. pneumoniae strains isolated from clinical samples of patients admitted to an Italian 900-bed hospital between 21 May 2021 and April 2022. All the isolates were screened by PCR for the amplification of virulence loci. Whole genome sequencing was performed in strains tested positive for at least one target gene. Thirteen out of 354 (3.7%) were hvKp. Five were wild type and belonged to the hypervirulent clones ST23, ST86, ST5, and ST375 and to the new clone ST6310. Six strains carried the blaKPC gene: three belonged to ST101, two to ST512, and one to ST395. Two isolates were ST147 and carried the blaNDM gene. Although hvKp isolation is not frequent, their presence should be systematically investigated to avoid the spreading of both virulent strains and strains with combined increase in virulence and resistance to antibiotics. PCR-based protocols are essential for surveillance of these strains, which do not always show a recognizable phenotype. Moreover, hvKp strains were isolated also from patients without history of recent foreign travels, indicating an increased spreading of these strains as well as an underestimated of their circulation so far.IMPORTANCEKlebsiella pneumoniae is a healthcare-associated pathogen frequently resistant to antibiotics. Hypervirulent strains of pneumoniae (hvKp) can spread from the primary site of infection to multiple sites causing life-threatening infections also in young otherwise healthy individuals. This study described the isolation of 13 isolates of K. pneumoniae with increased virulence in a large tertiary hospital over a 1-year period. Among them, eight strains were multidrug resistant and hypervirulent. Although these hypervirulent strains are still rare in Italy, their presence is particularly concerning since they can cause difficult-to-treat life-threatening infections. Moreover, not all the hypervirulent isolates were positive by the string test, so hvKp isolates were not always phenotypically detectable. Molecular biology techniques such as PCR amplification and next generation sequencing are therefore necessary for the detection of hvKp isolates, and surveillance programs exploiting molecular techniques are highly desirable.
ABSTRACT
OBJECTIVES: This study aimed to characterize livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) strains isolated from patients admitted to Policlinico San Matteo in Pavia, located in an Italian region with high livestock density. METHODS: The starting dataset was composed by 353 MRSA strains isolated from blood cultures between 2011 and 2019 and in 954 MRSA isolated from nasal swabs, wound swabs, skin swabs, ulcer swabs, conjunctival swabs, urine and respiratory samples collected between 2018 and 2019. LA-MRSA was identified based on being MRSA resistant to tetracycline and negative for the PCR amplification of scn locus. Whole genome sequencing of the selected strains was performed, and virulence and resistance genes searched. RESULTS: Five out of 353 MRSA isolates from blood cultures (1.4%) and nine out of 904 MRSA isolates obtained from other materials (1%) were resistant to tetracycline and negative for the scn locus. The 14 strains were also negative for the lukS-pv, tsst, eta and etb loci. Nine of the 14 strains belonged to ST398, the most common ST of LA-MRSA in Europe. ST398 isolates belonged to four spa-types, of which the prevalent was t899. Eight genomes had the cassette SCCmec type V, five genomes had SCCmec type IV and one genome lacked SCCmec, mecA and mecC. CONCLUSION: The frequency of LA-MRSA in the patients of this study (1.4% in blood cultures, 1% in other samples) is low but relatively constant over time prevalence and comparable to that found in the few studies performed on patients to date.
