Microorganisms in Raw Milk

Incidence of Microorganisms in Raw Milk

• Micrococcus has an incidence of 30-99%.
• Streptococci has an incidence of 0-50%.
• Asporogenous Gram-positive rods, GNRs (including coliforms), Bacillus spores, and miscellaneous organisms (including streptomycetes) each have an incidence of less than 10%.

Types of Aerobic Mesophilic Microorganisms

• Micrococci include Micrococcus and Staphylococcus.
• Streptococci include Enterococcus ("fecal"), Group N, Mastitis streptococci, Streptococcus agalactiae, Streptococcus dysgalactiae, and Streptococcus uberis.
• Asporogenous Gram-Positive Rods include Microbacterium, Corynebacterium, Arthrobacter, and Kurthia.
• Spore-Formers include Bacillus (spores or vegetative cells) .
• GNR Group includes Pseudomonas, Acinetobacter, Flavobacterium, Enterobacter, Klebsiella, Aerobacter, Escherichia, Serratia, and Alcaligenes.
• Miscellaneous Groups include Streptomycetes, Yeasts, and Molds.
• Special media and/or incubation conditions are needed for the isolation and detection of species that belong to Clostridium, Lactobacillus and lactic acid bacteria, Corynebacterium, and certain pathogens.

Thermoduric and Psychrotrophic Microorganisms

• Thermoduric Genera include Microbacterium, Micrococcus, Bacillus spores, Clostridium spores, and Alcaligenes and survive heating at 63°C for 30 minutes
• Psychrotrophic Genera include Acinetobacter-Moraxella, Flavobacterium, Enterobacter, Alcaligenes, Bacillus, and Arthrobacter and exhibit visible growth at 5-7°C in 7-10 days.

Salmonella Species

• Consists of two species: Salmonella enterica and Salmonella bongori.
• S. enterica subspecies I consists of 1367 serotypes, isolated from warm-blooded animals (mammals and birds), and accounts for 99% of clinical isolates.
• The remaining subspecies (II, IIIa, IIIb, IV, VI, and VII) are from cold-blooded animals and are only 1% pathogenic to humans.
• A leading cause of food poisoning worldwide.
• Salmonellosis affects 3,840,000 Americans annually, costing billions in lost productivity and healthcare.
• The most common infectious disease caused by bacteria in the United States.
• Transmitted from animals to humans through food and occasionally from person to person via the fecal-oral route.
• Presents in various forms in humans, resulting in a broad clinical spectrum.

Gastroenteritis

• Incubation period is 6-72 hours.
• Symptoms include abdominal pain, profuse watery diarrhea, sometimes with mucus or blood, nausea, and vomiting.
• Fever of 38-39 °C is common and causes mild to severe discomfort.
• Acute symptoms typically resolve within 48 hours in uncomplicated cases, but can persist with prolonged diarrhea and low-grade fever for 10-14 days.
• Severe cases can lead to dehydration, causing hypotension, cramps, oliguria, and uremia; symptoms tend to be more severe in infants and the elderly (over 60 years).

Bacteremia

• Characterized by prolonged fever and positive blood cultures, with or without gastroenteritis, sweating, anorexia, and weight loss.
• Lacks the typical symptoms of typhoid fever, such as skin rashes, leukopenia, and continuous fever.

Enteric or Paratyphoid Fever

• S. cholerae-suis and S. enterica serotypes paratyphi A and B share symptoms with typhoid fever, including prolonged fever, rashes, splenomegaly, leukopenia, gastrointestinal symptoms, and positive stool/blood cultures.
• milder than S. typhi infections, clinical symptoms aren't reliable for diagnosis.

Local Infections

• Meningitis is a common local infection in infants.
• Polyarthritis can occur.

Escherichia Coli

• In 1945, Bray et al. discovered that E. coli can cause gastroenteritis.
• Classified into five main groups based on virulence mechanisms: enteropathogenic (EPEC), enterotoxigenic (ETEC), enteroinvasive (EIEC), enterohemorrhagic (EHEC), and enteroaggregative (EAEC).
• Diffusely adherent E. Coli (DAEC) is another strain that is less pathogenic.

Enterotoxigenic E. Coli (ETEC)

• Causes watery diarrhea, cramps, and sometimes mild fever.
• Similar to cholera, it results from ingestion of a large number of bacteria that colonize the small intestine and release toxins into the intestinal lumen.

Enteroinvasive E. Coli (EIEC)

• Infection is similar to Shigella infections.
• Characterized by acute, watery diarrhea with fever and abdominal cramps, possibly progressing to bloody and mucoid stools.
• Infection is caused by contaminated food and water and person to person spread.

Enterohemorrhagic E. Coli (EHEC)

• Causes severe bloody diarrhea (hemorrhagic colitis), hemolytic uremic syndrome (HUS), and thrombotic thrombocytopenic purpura.
• Infections can sometimes just cause diarrhea or be asymptomatic.
• The most common cause of acute kidney failure in children in the United States.

Enteroaggregative E. Coli (EAEC)

• Causes acute, persistent, and bloody diarrhea in children and is linked to outbreaks and nosocomial infections globally.
• Recognized as a causative agent of diarrheal disease in HIV-infected adults in developed countries.

Enterobacter Sakazakii

• Belongs to the family Enterobacteriaceae, genus Enterobacter.
• Previously known as Enterobacter cloacae "yellow pigment.".
• Recognized as a unique species in 1980, separate from E. Cloacae and based on DNA, pigment production, and biochemical reactions.
• Mortality rate is 40-80%, often leading to death within days after birth in infants
• Other effects are severe neurological disorders like hydrocephalus and quadriplegia.
• Contaminated powdered infant formula is a transmission source.
• Isolated from insects in a dairy farm.
• Not found in surface water, soil, mud, decaying wood, grain, bird droppings, rodents, pets, cattle, or raw cow's milk.
• Strains are isolated from clinical materials, blood, or cerebrospinal fluid.

Enterobacter spp. (E. Sakazakii) Disease

• Causes nosocomial infections.
• Rarely an opportunistic pathogen causing severe meningitis in neonates and premature infants.
• Commonly causes gastrointestinal disorders in newborns.
• Affects mostly infants, inducing digestive issues; in some instances, the manifestation is strictly septicemia.
• Can breach the digestive barriers, entering the bloodstream and, ultimately, the cerebrospinal fluid.
• Symptoms include ventriculitis, cerebral abscesses, infarcts, and cyst formation.
• Highly susceptible to common antibacterial agents used against other Enterobacteriaceae, with ampicillin/gentamicin as effective treatments in most cases.

Control Measures

• Implementation of a sound production process.
• Focus on preparation, handling, and bottle usage in the preparation of powdered milk.
• Use sterile water and sterilized bottles and nipples.
• Formulas with probiotic bacteria should never be prepared with hot water.