Microbial biofilms

BiofilmsAdherent microcolonies bacteria or fungiInherent lack of susceptibility to antimicrobialsDiffers from classical genetic resistance in that its reduced susceptibility disappears when the biofilm is returned to planktonic growth60% of human infections chronic, recurrent and device-related infections

Biofilms in:NatureFood industryHospitals colonization of MRSA in nasal passagesMedical devices healthcare associated infections urinary tract, respiratory tract, surgical sites, bloodstream infections

Tolerance vs. resitsanceTolerance is only demonstrated when the isolate is in the biofilm mode of growth; lost when the culture is returned to planktonic growthTolerance implies that the biofilm is not killed by the antimicrobial

Mechanisms of biofilm toleranceBiofilm structure by TEM/SEM, diffusion barrier renders them resistant to antimicrobial treatmentCHO matrixDNA gene pool for diversity seen w/in the biofilmPenetration fluoroquinolones > aminoglycosidesBiofilm physiologyTargeting one member of the mixed population w/in the biofilm may alter the suseceptibility patterns of other speciesCellular signalling quorum sensing & cyclic deguanylate Plasticity of biofilmsPerister cells pre-exists in the populationSubpopulation of cells - Insurance hypothesis combination of diverse populations in the biofilm that contribute to tolerance

Antibiotic prescribing and stewardship (appropriate use)Victims of their own successESKAPE pathogens E. faecium, S. aureus, K. sp, A. baumannii, P. aeruginosa, ESBL producing organismsAlternatives are more toxic than the first line drugs

Principal goals of a stewardship program:Improve patient outcomesLessen the risk of adverse effectsReduce resistance levels, or at least slow the rate of resistance developmentImprove cost-effectiveness

Components of antimicrobial stewardship programID MDClinical pharmacist w/ Infectious dx trainingMedical microbiologistInfection control professionalHospital epidemiologitsIT specialist

Monitoring of antibiotic resistanceAntibiotic consumption and costs, both in total and by specific drug classCosts associated with prescribing potentially toxic antibioticsRates of resistance to specific antibiotics by problem pathogensPharmacy interventions to advise on inappropriate antibiotic use. The incidence of hospital-acquired infections

Public health microbiology: infection prevention and controlTwo infection control issues:From where (or from whom) has the infection comeHow can we minimize the risk of it spreading to others

HCAI Healthcare associated infections:Wound and soft tissue infectionsBloodstream infectionsUTIRespiratory tract infectionsGI tract infections

Organisms that cause HCAI:1. S. aureus and MRSA2. S. epidermidis3. Gram neg bacteria4. glycopeptide-resistant enterococci5. C. difficile6. Norovirus explosive vomiting & diarrhea

5 opportunities/requirements for hand hygiene:Before touching a patientBefore clean/aseptic proceduresAfter body fluid exposure/riskAfter touching a patientAfter touching patient surroundings

Zero tolerance approach to avoidable infections

SIGHT C. difficileSuspect that a case of diarrhea mabye infectiveIsolate patient and contact ICC teamGloves and apronsHand washing with soapTest stool for C. difficile toxins

BiosafetyEbola virus

VaccinationReinfections (rare):When the infectious agent exhibits antigenic plasticity such as common colds/influenzaIf patient is immunocompromised (due to immunosuppressive therapy or immunological disorders)When a significant amount of time has passed after the first infection.

Spread of InfectionCommon-source Transient source of infection (infected drinking water, contaminated food)Propagated-sourceDirect transmission of an infective agent from a diseased individual to a healthy, susceptible one

Classes of ImmunityPassive (artificially acquired)IgG Provides passive protection to the newbornPreformed antibodiesActive (artificially acquired)AttenuatedNon-living or inactivated vaccine

Types of vaccineLive, infective attenuatedAdvantages:Immunization mimics the course of a natural infection such that a single exposure is required to render an individual immune.Exposure maybe mediated through the natural route of infection (oral)Killed and componentImmunity may not reach optimal levels until the course of immunization is completeDNA vaccines

Microbial spoilage, infection risk and contamination controlSpoilage deterioration of pharmaceuticalsGPMP Good Pharmaceutical Manufacturing practice quality, safety, efficacy, stability, acceptable to patientsConsequences of contamination:Spoiled productThreat of litigationHealth hazard to patients

Pharmaceutical ingredients susceptible to attackTherapeutic agents Less potent/inactive; thalidomideSurface-active agents (anionic surfactant, soap)Non-ionic surfactantsIncreasing chain length and branching decrease ease of attack; Pseudomonas in quaternary ammonium antisepticsOrganic polymersThickening & suspending agent; agar

Pharmaceutical ingredients susceptible to attack

HumectantsGlycerol / sorbitol to reduce water lossFats and oilsHydropobic; fungal attackSweetening, flavouring & coloring agentsPseudomonasPreservatives and disinfectantsGram negative; Pseudomonas in eye drops

Observable effects of microbial attackSmell, sour taste fatty acids and their ketonic oxidation productsDiscoloration by microbial pigmentsLoss of viscosity & sedimentationGaseous metabolites seen as trapped bubbles within viscous formulations

Factors affecting microbial spoilageType / size of contaminant inoculumRaw materials contaminated, lapse in plant-cleaning protocol, biofilm, product was grossly misused during administrationLag period before spoilage beginsNutritional factorsMetabolic adaptability

Factors affecting microbial spoilageMoisture content water activityThe greater the solute concentration, the lower is the water activity. Most ogranisms grow best in dilute solutions (high Aw).Tablet film coating greatly reduces water vapor uptake during storage while allowing ready dissolution in bulk water.

Factors affecting microbial spoilage

Redox potentialAbility of organism to grow in an environmentStorage temperatureSpoilage occurs over -20 to 60 degrees CDeep freeze at -20C for long-term storageShort term storage of dispensed TPNpHBacterial spoilage more likely at neutral pH.

Factors affecting microbial spoilage

Packaging designControl entry during storage and useMedicines rely on their low Aw to prevent spoilage Protection of microbes w/in pharmaceutical productsSurfactants, suspending agents, proteins can increase the resistantce of orgs to preservatives

Hazard to HealthSalmonella in pacreatin and thyroid extractLoss of sight; burn patientsSurfactants increase resistance of microorganisms. Pseudomonas in TPN fluidsHIV infection infection of hemophiliacsCJD from human growth hormoneContaminated IV fluid; moral

Sources of control of contaminationI. In manufactureRaw materials, processing equipment, cleaning equipment, area with filtered air, personal and production hygiene, suitable packagingHospital manufactureWater - > 80C & circulated a flow rate of 1-2 m/s to prevent the build up of bacterial biofilms in the piping. Environment - GMPPackaging & re packagingII. In use (human, environment & equipment sources)

Sources of control of contaminationII. In use cross infection (human, environment & equipment sources) improvements in packaging & changes in nursing practicesHuman- topical products are most at risk Pseudomonasenvironmental airborne; static level of 10^2-10^3/g or per mLEquipment reuse, cosmetic products, humidifier, incubators, ventilators, resuscitators

Extent of microbial contaminationSpecific product / Isolated incidentIn manufacture Thyroid tablets with SalmonellaHydrocortisone eye ointment with PseudomonasIn useHeavy contamination 18 % > 10^4 CFU/g or CFU/mL

Factors determining the outcome of a medicament-borne infectionType and degree of microbial contaminationRoute of administrationepiduralResistance of the patient

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