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Types of Spoilage, Factors Affecting the Microbial Spoilage of Pharmaceutical Products

Physio-chemical spoilage, Viable growth, Gas production, Biological spoilage, Physical spoilage, Chemical spoilage, Factors- Nutritional factors, pH
Including air, water, and soil, our environment is filled with microbes. These microorganisms are not only said to destroy food but also to ruin medicinal items. Pharmaceutical product deterioration can pose major health risks to users while also causing financial difficulties for producers. Pharmaceutical items are regarded microbiologically ruined when discernible physical or chemical changes have occurred in the product and even low amounts of pathogenic bacteria or harmful microbial metabolites are present. In a nutshell, it is the degradation of medicinal items caused by microbial infection.

Types of microbial spoilage

Infection caused by contaminated pharmaceutical items -
  • Pharmaceutical products can get infected from a variety of sources, including raw materials, manufacture, and storage.
  • When such contaminated items are ingested, they induce illnesses.
  • Cholera, Pseudomonas infections, botulism, and other diseases
  • Table given below summarizes the most frequent illnesses encountered in dose form.

Dosage form 

Contaminating microbes


Eye products 

Pseudomonas aeruginosa 

Eye infections

IV medicines 

Candidia species 


Ointments and creams

Gram negative organisms

Dermal infections

Tablets and capsules 

Samonella species

Salmonella infections

Antiseptic solutions

Pseudomonas species 


Physio-chemical spoilage

There are some changes generated by microbial species in this type of spoiling, and as a result of these changes, the physical characteristics are also affected or deteriorate, which is why it is termed physico-chemical spoilage.

Viable growth - A viable layer of microorganisms grows on the surface of pharmaceutical formulations.
  • This layer, as well as the presence of microbial cells, may be observed with the naked eye.
  • Molds are placed on top of syrups or sugar-containing items.
Gas production - By virtue of their metabolic activity, some microbial contaminants form gas bubbles and foam on top of pharmaceutical formulations.

Yeasts, for example, can be found in carbohydrates-containing formulations such as syrups.

Biological spoilage - The microbial metabolism of items leads to chemical degradation, a way of contaminating items with contaminants.
  • Microbes primarily create two types of compounds,
  • Microbial metabolites
  • Microbial toxins
  • Microbial Toxins: Endotoxins generated by Gram-negative bacteria such as E.coli.
  • Microbial Metabolites: A variety of organic acids and amines.
Physical spoilage - These physical changes are generated by microbial activity in the formulation.
  • The emulsifying ingredient in an emulsion is destroyed by microbes, causing it to become unstable and to separate into phases.
  • Changes in odour: Microbes, as a result of their activity in the medicinal product, contribute odour.
  • Toluene odours, for example, as a result of Penicillium species spoiling Balsam of Tolu.
  • Geosmin odour in water phases caused by Actinomycetes pollution.
Chemical spoilage - This happens as a result of numerous chemical processes mediated by contaminating bacteria.

Table given below lists the formulation constituents that are prone to chemical deterioration due to microbial activity.

Sr no.


Microrganism/ microbial enzyme



Active ingredient 

  1. Atropin 



  1. Aspirin 






Bacterial amylase 



Bacterial cellulase 



Preservatives like hydroxy benzoate ester 

Pseudomonas species 


Factors affecting microbial spoilage in pharmaceutical spoilage

Understanding the many elements that promote microbe development in formulations allows for formulation manipulation and avoidance of microbiological deterioration without harming patient acceptability or medicinal efficacy.

The following are some recognized parameters that influence microbial deterioration of pharmaceutical products:

Nutritional factors

  • Microbial growth is primarily mediated by carbon or nitrogen substrates, which are found in organic and inorganic substances.
  • Many formulations' intricacy provides significant nutritional variation for a diverse spectrum of bacteria.
  • The use of raw vegetable or animal ingredients in a formulation creates a more nutritious environment.
  • A water made using an efficient ion exchange process would generally contain enough nutrients to support the growth of Gram-negative waterborne bacteria such as Pseudomonas.


  • pH extremes protect against microbial assault.
  • Bacterial deterioration is more common around neutrality, with reports of Pseudomonads and Gram-negative bacteria appearing in antacid mixes, flavoured mouthwashes, and distilled or demineralized water.
  • Above pH 8 (for example, with soap-based emulsions), deterioration is uncommon.
  • Mold or yeast attack is more common in goods with low pH levels (e.g., fruit juice-flavored syrups with a pH of 3–4).
  • Yeasts may metabolize organic acids, raising the pH to levels suitable for secondary bacterial development.

Packaging design

  • Packaging can have a significant impact on the microbiological stability of particular formulations by limiting the entrance of contaminants during storage and usage.
  • A substantial amount of attention has been paid to the design of containers to protect medications for parenteral administration from introducing contaminants.
  • To prevent microbiological ingress into multi-dose injectable vials following hypodermic needle withdrawals, self-sealing rubber wads must be utilized.
  • When medications rely on their low Aw to avoid spoiling, packaging like as strip foils must be made of water vapour-proof materials and have totally effective sealing.
  • Under humid circumstances, cardboard exterior packaging and labels can become microbial attack substrates, therefore preservatives are frequently applied to limit the danger of damage.

Size of contaminant inoculum

  • The pace of degradation of a pharmaceutical product is determined by the size of the product's microbial population.
  • When compared to large populations, smaller microbial populations exhibit less degrading changes.
  • However, the amount of the inoculum alone is not necessarily a good indication of the likelihood of spoiling.
  • A low amount of pseudomonas in a poorly maintained solution may indicate a higher danger than tablets having a significant number of fungal and bacterial spores.

Storage temperature

  • Pharmaceutical deterioration might occur at temperatures ranging from -20°C to 60°C.
  • The sort of bacteria involved in spoiling may be determined by the storage temperature.
  • It is standard practice to deep freeze pharmaceutical raw materials and total parenteral nutrition (TPN) feeds produced in hospitals at -20°C or below to preserve them for long-term use.
  • Reconstituted syrups and multi-dose eye-drop packs are occasionally given with the warning to store in a cold environment,' such as a household fridge (8°–12°C), to limit the danger of pollutants introduced accidentally during usage.

Moisture content

  • The water activity (Aw) of a product can be used to assess the fraction of uncomplexed water available in the formulation to promote microbial growth.
  • Most microbes thrive in environments with strong water activity.
  • By reducing their water activity with sugar, polyethylene glycol, or sodium chloride, or perhaps by drying, formulations can be prevented from becoming contaminated by microbes.

Redox potential

  • Microorganisms rely on the oxidation-reduction balance in their environment (redox potential) to thrive, because they require appropriate terminal electron acceptors.
  • Due to fats and oils' high oxygen solubility, even relatively viscous emulsions can have a high redox potential.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of pharmaguideline.com, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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