<unk>  species are enteric gram-negative bacilli. They are normal human gut flora. They are mostly a nosocomial pathogen found in compromised hosts, patients over 60 years of age, and in neonates. Common infections are of the urinary tract, line infections, pneumonia, and in neonates CNS infections.
Citrobacter
Escherichia coli
Klebsiella
Salmonella
Enterobius
Proteus mirabilis
Clostridium
Bacteroides fragilis