MAS1 and nosocomial infection: The causal graph also highlighted several opportunistic pathogens, such as Veilonella parvula (mprF, mphA and blaOXY.2.1), Staphylococcus epidermidis (mecA, dfrC, mgrA and aadD2) and Citrobacter freundii (blaCMY alleles); these three species are well-known aetiological agents of hospital-acquired infections that can lead to pulmonary infections, meningitis and sepsis in neonates [108–110].