Parasites, Molds, and Food Spoilage

Acinetobacter

• Unable to move, gram-negative bacteria with an affinity to Neisseriaceae.
• Formerly known as Achromobacters and Moracellae.
• Strict aerobes that are oxidase negative.
• Young cells are rod-shaped, while older cells are coccoid-shaped.
• Mol% G+C content is 39-47.

Aeromonas

• Gas-producing aquatic gram-negative bacteria found in fermented sugars.
• Formerly in the Vibrionaceae family, now in Aeromonadaceae.
• Found in intestines of fish and can be fish pathogens.
• Mol% G+C content is 57-65.

Alcaligenes

• Alkali producers that are gram-negative, sometimes gram-positive.
• Rod-shaped and produce alkaline reactions, found in litmus milk.
• Non-pigmented, widely distributed in nature as decomposers.
• Found in raw milk, poultry products, and fecal matter.
• Mol% G+C content is 58-70.

Alteromonas

• Marine and coastal water inhabitants found in seafood.
• Require seawater salinity for growth.
• Gram-negative, motile rods, aerobe.

Arcobacter

• Campylobacter, Helicobacter, and Wolinella were all once classified as Campylobacter.
• Gram-negative, curved or s-shaped rods that can grow at 15°C.
• Aerotolerant and found in poultry, raw milk, shellfish, water, cattle, and swine products.
• Oxidase positive, catalase positive.
• Causes abortion and enteritis in some animals and humans caused by Arcobacter butzleri.

Bacillus

• Gram-positive, spore-forming, aerobes.
• Mostly mesophiles, although psychrotrophs and thermophiles exist.
• Bacillus anthracis and Bacillus cereus are the only two pathogens in the bacillus family.
• Most strains don't cause diseases, but some cause foodborne gastroenteritis.

Brevibacillus

• Found in soil, water, plants, air, and dust.
• Nine species.

Brochothrix

• Gram-positive, non-spore forming rods related to Lactobacillus and Listeria.
• Not true coryneforms.
• Exponential phase cells are rods, other cells are coccoids.
• Shares features with Microbacterium.
• Common on processed meats, both fresh and stored in gas-impermeable packages.
• Only two species are recognized: Brochothrix thermosphacta, Brochothrix campestris.
• Mol% G+C content is 36.

Burkholderia

• Gram-negative rods found on plants.
• Can be found in raw milk, and can cause vegetable spoilage.
• Raw cow's milk in Northern Ireland has isolates of Burkholderia cepacia
• Found in cystic fibrosis patients.
• Formerly classified in the genus Pseudomonas.

Campylobacter

• Gram-negative, spirally curved rods, previously classified as Vibrio.
• Microaerophilic to anaerobic.
• Mol% G+C content is 30-35.
• Campylobacter nitrofigilis and Campylobacter cryaerophila are now under Arcobacter.
• Campylobacter cinnaedi and Campylobacter fenneliae and Wolinella carva → C. curvus and Wolinela recta → C.rectus all now under Helicobacter.

Carnobacterium

• Gram-positive, catalase-negative rods.
• Differ from lactobacilli because they are unable to grow on acetate.

Citrobacter

• Enteric bacteria, slow lactose-fermenting, gram-negative rods.
• Produce yellow colonies on PCA.
• All members uses citrate as the sole carbon source.
• Mol% G+C content is 50-52.
• Citrobacter freundii is the most prevalent species in foods, not uncommon on vegetables and fresh meats.

Clostridium

• Anaerobic, spore-forming rods, widely distributed in nature.
• Many species, some cause disease in humans.
• Mesotrophic, psychrotrophic, thermophilic strains.

Corynebacterium

• True coryneform genera of gram-positive, rod shaped.
• Involved in the spoilage of vegetable and meat products.
• Mesotrophs, some are psychrotrophs.
• Corynebacterium diphtheriae causes diphtheria in humans.
• Mol% G+C content is 51-63.

Enterobacter

• Enteric gram-negative bacteria are typical of other Enterobacteriaceae.
• Relative to typical growth requirements.
• They are not adapted to life in the gastrointestinal tract.
• Enterobacter agglomerans has been transferred to Pantoea.

Enterococcus

• Made to accommodate some of the Lancefield serologic group D cocci.
• Expanded to more than 16 species of gram-positive ovoid cells, occur singly, pairs, or short chains.
• Was once in the genus Streptococcus.
• Some species do not react with group D antisera.

Erwinia

• Gram-negative enteric rods, associated with plants.
• Three species have been transferred to Pantoea, now on Pectobacterium.
• Erwinia carotovora → Pectobacterium carvovorum and Erwinia chrysanthemi → Pectobacterium chrysanthemi.

Escherichia

• Most studied genus of all bacteria
• See chart for virulence and key traits

Flavobacterium

• Gram-negative rods, yellow to red pigments on agar, association with plants.
• Mesotrophs, others are psychrotrophs.
• Participate in the spoilage of refrigerated meats and vegetables.
• Some former flavobacterial species are in five new genera i.e. Empedobacter, Chryseobacterium, Myroides, Sphingomonas and Sphingobacterium.

Hafnia

• Gram-negative enteric rods.
• Spoilage of refrigerated meat and vegetables products.
• Motile, lysine positive, ornithine positive.
• Mol% G+C content of 48-49.
• Hafnia alvei, the only species.

Kocuria

• Genus split off from Micrococcus.
• Oxidase negative, and catalase positive.
• Kocuria rosea, Kocuria varians, Kocuria kristinae.
• Mol% G+C content of 66-75.

Lactobacillus

• Taxonomic techniques widely used since the 1980s have reassigned some members of this genus, with changes reflected in the ninth edition of Bergey's Manual.
• Based on 16S rRNA sequence data, three phylogenetic clusters were identified, with one cluster including Weissella.
• Genus is likely to undergo further reclassification in the future.
• Gram-positive, catalase-negative rods that often form long chains.
• Food-associated strains are typically microaerophilic, but many anaerobic strains exist, especially in the colon and rumen.
• Commonly found on nearly all vegetables and some lactic acid bacteria-associated foods.
• Frequently present in dairy products Lactobacillus suebicus.

Lactococcus

• Lancefield serologic group N cocci once in the Streptococcus.
• Grom positive, nonmotile, catalase-negative, spherica, or ovoid.
• Single, pairs, or in chains.
• Grow at 10C but not at 45C.
• Most strains react with group N antisera.
• I-lactic acid is the predominant end-product of fermentation.

Leuconostoc

• Colorless nostoc, another genera of lactic acid bacteria.
• Gram-positive, catalase-negative cocci, heterofermentative.
• Leuconostoc oenos → Oenococcus oeni, now in Oenococcus.

Listeria

• Gram-positive, non-sporing rods closely related to Brochothrix.
• The six species show 80% similarity by taxonomic studies.

Micrococcus

• Gram-positive, and catalase positive cocci.
• Inhabitants of mammalian skin and grow in the presence of high levels of NaCl.
• Reduced by the creation of new genera: Dermacoccus, Kocuria, Kytococcus, Nesterenkonia, Stomatococcus.
• Micrococcus luteus and Micrococcus lylae are the only two remaining micrococcal species.

Moraxella

• Short gram-negative rods, sometimes classified similar to Acinetobacter.
• Sensitive to penicillin and oxidase positive.
• Current species in the genus Psychrobacter were once in Moraxella.
• Metabolism is oxidative, and acid is not formed from glucose.
• Mol% G+C content of 40-46.

Paenibacillus

• Has organisms formerly in the genera Bacillus and Clostridium.
• Known for their degradation of macromolecules, production of antibacterial and antifungal agents etc.
• Also has the capacity to fix N2.
• Newly species added Paenibacillus lautus, Paenibacillus peoriae.

Pandoraea

• First isolated from sputa of cystic fibrosis patients.
• Organisms are related to some of the pseudomonads.

Pantoea

• Gram-negative, non-capsulated, non-sporing straight rods, and motile by peritrichous flagella.
• Found in plants, seeds, soil, water, and human specimens.
• Mol% G+C content of 49.7 to 60.6.

Pediococcus

• Coccus growing in one plane.
• Homofermentative cocci are lactic acid bacteria.
• Exist in pair or tetrads resulting from division in two planes.
• Can grow in 18% NaCl.
• Mol% G+C content of 34-44.

Proteus

• Enteric gram-negative rods, aerobes, pleomorphism.
• Motile, produce swarming growth on the surface of moist agar plates.
• Typical enteric bacteria in the intestinal tract of humans and animals.

Pseudomonas

• Soil and water bacteria, distributed among fresh foods, especially vegetables, meats, poultry, and seafood products.
• Pseudomonas fluorescens and Pseudomonas aeruginosa, remain in the original genus.

Psychrobacter

• Plump coccobacilli that often occur in pairs.
• They are aerobic, nonmotile, and catalase and oxidase positive, and generally do not ferment glucose.
• Sensitive to penicillin and utilize -aminovalerate, whereas the acinetobacters do not.
• They closely resemble the moraxellae and have been placed in the family Neisseriaceae.

Salmonella

• Gram-negative enteric bacteria, considered to be human pathogens.
• The bacteria in the genus Salmonella are divided into two main species, i.e. Salmonella enterica and Salmonella bongori.
• Majority of Salmonella strains that cause illness in humans belong to Salmonella enterica.

Serratia

• Gram-negative rods that belong to ther family Enterobacteriaceae are aerobic and proteolytic
• The mol% G + C content of DNA is 53-59

Shewanella

• The bacterium once classified as Pseudomonas putrefaciens Mol% G + C content of DNA is 44-47

Shigella

• All members of this genus are presumed to be human enteropathogens
• All are Gram-negative, non-motile rods
• Shigella can be classified into four major serological groups i.e. Group A: Shigella dysenteriae, Group B: Shigella flexneri, Group C: Shigella boydii, Group D: Shigella sonnei

Sphingomonas

• Gram-negative bacteria that commonly produce a yellow pigment, formerly in the Flavobacterium family
• Mol% G + C content of DNA is 63-70

Staphylococcus

• Gram-positive, catalase-positive cocci
• Staphylococcus aureus; which causes several disease syndromes in humans, including foodborne gastroenteritis
• Staphylococcus caseolyticus → Macrococcus caseolyticus

Stenotrophomonas

• Stenotrophomonas is a Genus of Gram-negative rods
• Stenotrophomonas maltophilia

Vibrio

• A Gram-Negative bacteria of straight, curved rods
• Found on fish, in feces, and in water, other foods

Weissella

• This genus of lactic acid bacteria was established in 1993 in part to accommodate the "Leuconostoc branch" of the lactobacilli.
• The seven species are closely related to the Leuconostoc

Foodborne Molds

Alternaria

• Separate mycelia with conidiophores and large brown conidia
• They cause black rots of fruit
• Some produce Mycotoxins

Aspergillus

Produce chains of conidia

• produce yellow cleistothecia
• Some species cause Spoilage of oils,
• Involved in shoyu fermentation

Aureobasidium

• Aureobasidium pullulans is yeast-like colonies produced initially, later spreads and produce black patches
• Also cause “black spot” on meats
• Mol% G + C content of DNA is 53-63

Botrytis

• Long slender, pigmented conidiophores are produced
• Often causes grey mould rot of apples, pears, raspberries, strawberries, grapes

Byssochlamys

• Byssochlamys are known for Heat resistance
• often spoils some high-acid canned foods

Cladosporium

• Causes Black Spot & are Field Fungi
• Some are lemon shaped & produces "black spot” on beef and frozen mutton

Colletotrichum

• Belong to class Coelomycetes and perform conidia inside acervuli
• Species are found on foods, it produces anthracnose

Fusarium

• Fusarium causes Brown rot of citrus fruits & soft rot of figs + some cause zearalenone, fumonisins, and trichothecenes.

Geotrichum

• Once known as Oidium lactis and Oospora lactis.
• These yeast-like fungi are usually white and reproduce by formation of arthroconidia.

Monilia

• pink, gray, or tan conidia, commonly produce brown rot of stone fruits such as peaches.

Mucor

• Nonseptate hyphae are produced that give rise to sporangiophores that bear columella with a sporangium at the apex
• No rhizoids or stolons are.

Penicillium

• When conidiophores and conidia, they produce a bluey or green mould rot

Rhizopus

• Nonseptate hyphae that give rise to stolons and rhizoids + Stolonifer produced can be be referred to bread moulds that produces watery soft rot

Thamnidium

• Only species: Thamnidium elegans

Trichothecium

produces a pink rot of fruit with a Pink colour

Wallenia

• Produces deep-brown colonies on culture media and on foods

Xeromyces

– Has the lowest H2O for growth, needs <0.61 Aw

Foodborne Protozoa

Cryptosporidium parvum

• Highly resistant to chlorine in water so its hard to remove completely from water
• causes cryptosporidiosis, leading to watery diarrhea, stomach cramps, nausea, vomiting, fever, and dehydration.

Cyclospora cayetanensis

• responsible for cyclosporiasis; can ingest water

Entamoeba histolytica

• Causes amoebiasis (amoebic dysentery

Giardia lamblia

– Is highly resistant to cold temperatures, causing diarrhea/ fatigue.

Test your knowledge of common parasites, food spoilage molds like Aspergillus glaucus, and the impact they have on health and food safety. Questions cover transmission routes, symptoms, and characteristics of each.