Matrix-Assisted Laser Desorption Ionization–Time of Flight and Comparative Genomic Analysis of M-18 Group A Streptococcus Strains Associated with an Acute Rheumatic Fever Outbreak in Northeast Italy in 2012 and 2013

Abstract

f Acute rheumatic fever (ARF) is a postsuppurative sequela caused by Streptococcus pyogenes infections affecting school-age children. We describe here the occurrence of an ARF outbreak that occurred in Bologna province, northeastern Italy, between November 2012 and May 2013. Molecular analysis revealed that ARF-related group A Streptococcus (GAS) strains belonged to the M-18 serotype, including subtypes emm18.29 and emm18.32. All M-18 GAS strains shared the same antigenic profile, including SpeA, SpeB, SpeC, SpeL, SpeM, and SmeZ. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) analysis revealed that M-18 GAS strains grouped separately from other serotypes, suggesting a different S. pyogenes lineage. Single nucleotide polymorphisms and phylogenetic analysis based on whole-genome sequencing showed that emm18.29 and emm18.32 GAS strains clustered in two distinct groups, highlighting genetic variations between these subtypes. Comparative analysis revealed a similar genome architecture between emm18.29 and emm18.32 strains that differed from noninvasive emm18.0 strains. The major sources of differences between M-18 genomes were attributable to the prophage elements. Prophage regions contained several virulence factors that could have contributed to the pathogenic potential of emm18.29 and emm18.32 strains. Notably, phage ⌽SPBO.1 carried erythrogenic toxin A gene (speA1) in six ARF-related M-18 GAS strains but not in emm18.0 strains. In addition, a phage-encoded hyaluronidase gene (hylP.2) presented different variants among M-18 GAS strains by showing internal deletions located in the ␣-helical and TS␤H regions. In conclusion, our study yielded insights into the genome structure of M-18 GAS strains responsible for the ARF outbreak in Italy, thus expanding our knowledge of this serotype. Streptococcus pyogenes, group A streptococcus (GAS), is a Gram-positive bacterium responsible for a wide spectrum of diseases ranging from moderate or mild infections to severe invasive diseases such as necrotizing fasciitis and toxic shock-like syndrome (TSLS). Several GAS infections can cause severe postinfectious sequelae, including acute poststreptococcal glomerulonephritis, acute rheumatic fever (ARF), and rheumatic heart disease (1).ARF is a systemic disorder resulting from an autoimmune disease following a GAS infection that usually occurs in children between 5 and 15 years of age (2). During the last several decades, the incidence of ARF cases has significantly declined in the United States and Western Europe, whereas it remains high in Eastern Europe, Asia, and Australia (3). However, the resurgence of ARF in several geographical areas, including United States, is a matter of concern (4).S. pyogenes possesses different virulence factors such as the M protein and superantigens (SAgs) that contribute to the pathogenesis of GAS infection (1). On the basis of the high variability of the M protein among GAS strains, the 5=-terminal sequence of the emm gene (emm typing) is considered a reliable molecular marke...

Epidemiological and Molecular Characterization of an Invasive Group A Streptococcus emm 32.2 Outbreak

“…Other notable features of GAS epidemiology include the propensity for long-term fluctuations in disease rates, such as the recent substantial increase in scarlet fever in the United Kingdom in 2013/2014 ( 4 ), and the association with outbreaks. GAS outbreaks are strongly associated with long-term-care or institutional facilities ( 5 – 8 ) and occur less often within whole communities ( 9 – 11 ). The introduction of new emm genotypes ( 12 , 13 ) or the acquisition of prophages harboring virulence genes by previously circulating GAS are the primary mechanisms underpinning these outbreaks ( 14 – 16 ).…”

Outbreak of invasive Group A streptococcus disease in a nursing home in Ireland in February 2023 caused by emm type 18

“…pharyngitis outbreaks and the subsequent onset of acute rheumatic fever [28][29][30]. A relatively high prevalence (9%) of emm18 among iGAS was reported one in Italian study, 2003-2005 [28].…”

“…Multilocus sequence typing and SNP-based analysis, though limited, confirmed the relatedness of the three isolates. Further analysis of the three genomes revealed that all three isolates possessed the hasABC operon encoding for the hyaluronic acid capsule and considered to be an important virulence factor of emm 18 strains [ 29 , 34 ]. As reported elsewhere for emm 18 isolates, the three outbreak isolates also harboured the speA gene encoding the SpeA superantigen [ 29 ].…”

“…Further analysis of the three genomes revealed that all three isolates possessed the hasABC operon encoding for the hyaluronic acid capsule and considered to be an important virulence factor of emm 18 strains [ 29 , 34 ]. As reported elsewhere for emm 18 isolates, the three outbreak isolates also harboured the speA gene encoding the SpeA superantigen [ 29 ]. The speA gene, also present in emm 1 and emm 3, has been shown to be positively associated with invasive disease [ 35 ].…”

Toward the Knowledge of the Epidemiological Impact of Acute Rheumatic Fever in Italy

“…GAS M types have been highlighted as an important determinant to clarify the distribution and development of ARF outbreaks. Genetic variation in the emm gene, which encodes the M protein, has been correlated with varying ARF incidence, particularly the occurrence of GAS serotype M18 isolates (20)(21)(22). The association of several outbreaks of ARF with the circulation of mucoid GAS strains in the community has been reported (23).…”