E.coli identification process, what is the purpose of elevated temperature 42-44 C?

• During microbial limit testing Macconkey broth and Macconkey agar are two media used for E.coli identification.
• Macconkey broth  is incubated at 42-44⁰C for 24 to 48 hrs.
• Macconkey agar  is incubated at 30-35⁰C for 18 to 72 hrs.
• The purpose of the elevated temperature 42-44⁰C is to allow for selective condition for fecal E.coli.
• The selected temperature is usually a compromise between sensitivity and specificity as not all E.coli stains will grow, or grow and produce gas, at these higher incubation temperature.
• So initially, 42-44⁰C incubation is provided for identification of fecal E.coli.
• But other strains of E.coli could not grow at this higher temperature.
• Once the enrichment of fecal E.coli has been performed in macconkey broth sample is streaked on Macconkey agar media, then incubate at 30-35⁰C.
• Which is suitable temperature for growth of E.coli strains and enriched fecal E.coli strains.
• Fecal E.coli identification is necessary because  different strains of E.coli present in the environment. E.coli is gram negative rod shaped pathogenic bacteria is an indicator of fecal contamination.
• Such contamination could arise from poor hygiene operation and low quality water supply ..etc.
• E.coli is capable of causing diarrhea and sickness also.