Chapter 4 - Bacteria Flashcards
What % of cardiac output reaches the skin?
4%
Which classes of antibiotics better penetrate fibrotic tissue?
Fluoroquinolones, lincosamides, chloramphenicol
Name two underlying conditions that can be associated with bullous impetigo in adult dogs?
Hyperadrenocorticism, hypothyroidism, diabetes mellitus, other debilitating disease
With a tuberculoid response to mycobacterial infection, do you see caseous necrosis with few bacteria or solid sheets of foamy macrophages with numerous bacteria?
Tuberculoid = caseous necrosis with few bacteria Lepromatous = solid sheets of foamy macrophages with numerous bacteria
Which domestic animals can be affected by Yersinia pestis?
Rodents and cats > dogs (other domestic animals are resistant)
Which bacteria are in the tuberculosis complex group?
M. bovis, M. tuberculosis, M. microti
Which of the TB complex group are cats most susceptible to?
M. microti and M. bovis (M. tuberculosis is rare in cats)
Which breeds of dog are most often affected by canine leproid granuloma?
Boxers, SBTs, Foxhounds, Dobermans (and other short coated dogs)
What can be seen on cytology of canine leproid granuloma?
Variable numbers of medium length acid-fast bacilli, either intracellularly (within macrophages or giant cells) or extracellularly
Which mycobacteria are associated with feline leprosy syndrome?
M. lepraemurium, M. visibile, M. sp. strain Tarwin and a novel species found in New Zealand and the East coast of Australia
Name the rapidly growing / atypical mycobacteria?
M. fortuitum group including M. fortuitum, M. perigrinum, and the third biovariant complex
M. chelonae/abscessus group including M. chelonae and M. abscessus
M. smegmatis group including M. smegmatis sensu stricto, M. goodii, M. wolinskyi
A variety of other species, including M. phlei and M. thermoresistibile
How readily are organisms found on histopathology of rapidly growing / atypical mycobacterial infections?
Organisms are characteristically rare and difficult to find but are usually located in small clumps within the clear vacuoles.
Which breeds of dog and cat may have a genetic predisposition to non-tuberculoid, slow growing mycobacterial infection?
Miniature schnauzers, Basset Hounds, Somali, Abyssinian, Siamese
What is the difference between lepromatous leprosy and tuberculoid leprosy?
In lepromatous leprosy, there is nodular-to diffuse dermal to subcutaneous granulomatous inflammation without necrosis and with large numbers of intracellular acid-fast bacilli.
In tuberculoid leprosy, there are dermal to subcutaneous granulomas with central caseous necrosis surrounded by a zone of lymphocytes. Few to moderate numbers of acid-fast bacilli are generally limited to the areas of necrosis.
Staph. pseud. carriage is most often found at which body site?
SP found on sampling of buccal mucosa (upper lip) most commonly
>64% sensitive at this site
> 90% if include nares and two additional sites
Which are the most widespread MRSP strain types?
ST45, ST68, ST71
Which are the (up to now) known exfoliative toxins of S. pseudintermedius?
SIET
SPETA
EXPA
EXPB
Which S. pseud. toxin is known to digest canine desmoglein-1? In which disease this is reported?
EXPA, EXPB (previously reported as EXI)
Ιmpetigo
Mycobacterium spp. have been classified as belonging to the Mycobacterium tuberculosis complex, non-tuberculous mycobacteria (NTM) including rapid- and slow-growing species, and lepromatous mycobacteria/feline leprosy syndrome. Name the rapidly growing, non-tuberculoid mycobacteria?
Mycobacterium fortuitum, Mycobacterium abscessus, and Mycobacterium smegmatis
What type of mycobacteria are the Mycobacterium avium complex (MAC)?
Slow-growing, non-tuberculoid mycobacteria
What are the clinical signs of feline leprosy syndrome?
It is primarily a cutaneous disease presenting as alopecic or ulcerated, non-painful and freely mobile single or multiple nodules, often on the head, limbs and occasionally trunk. Rare cases affect the tongue, lips, nose or conjunctivae. Regional lymphadenopathy can occur. Systemic disease is rare, but can be progressive and aggressive.
What does MALDI-TOF stand for?
Matrix-assisted laser desorption ionisation - time of flight mass spectrometry
Urine culture in dogs with inactive urine sediments can be positive in 3.4-6% of samples; is growth associated with proteinuria?
No statistically significant difference was noted between the low and high protein groups. Prior studies have also failed to show correlation between increased UPC and bacteriuria.
What is biofilm?
A biofilm is an aggregate of microorganisms that adhere to each other on a living or non-living surface, and are embedded within a self-produced matrix of extracellular polymeric substances (EPSs), including exopolysaccharides, proteins, metabolites and extracellular DNA (eDNA).
What are the mechanisms of biofilm-mediated resistance?
- Prevention of antibiotic penetration
- Altered microenvironment inducing slow growth of biofilm cells
- Induction of an adaptive stress response
- Persister cell differentiation (phenotypic variants that are not genetically resistant to antibiotics but are tolerant to high concentrations of antibiotics)
What is quorum sensing?
Quorum sensing is a mechanism that allows bacteria to control gene expression in a cell density-dependent manner
What is the mechanism of action of S. aureus alpha toxin?
It activates metalloproteinase domain-containing 10 ADAM10; cleaves E-cadherin; breaks adherens junction and compromises actin cytoskeleton
Which Staphylococcal toxins act as superantigenic toxins?
Enterotoxins (staphylococcal enterotoxin C in SP)
TSST-1 (toxic shock syndrome toxin-1)
How do superantigens work?
- activate T cells in a nonspecific manner
- results in excessive immune response with polyclonal T cell activation and massive cytokine release
- bind to MHC II outside the classical antigen binding region
What are the mechanisms that S.aureus uses to avoid elimination by neutrophils?
- Inhibition of neutrophil extravasation from the bloodstream into tissues, neutrophil activation, chemotaxis
- Inhibition of phagocytosis by aggregation, protective surface structures, biofilm formation
- Inhibition of opsonization
- Inhibition of neutrophil killing mechanism
- Direct elimination of neutrophils by cytolytic toxins or triggering apoptosis
Which cells can Staphylococci survive in?
Neutrophils
Endo-/Epi-thelial cells
Osteoblasts
(escape endosomes and replicate - avoid immune recognition and antimicrobials)
What is the role of Staphylococcal fibronectin?
Proteins anchored to peptidoglycan responsible for attaching to extracellular matrices - cell invasion
(target for slide agglutination testing)
What is the role of Staphylococcal protein A?
Cell-wall associated protein interacting with host IgG, IgA, IgE and platelets - attenuates opsonophagocytosis and modulates platelet aggregation
Sensitises B cells and binds TNF-1
Which gene codes for staphylococcal protein A?
spa
Staphylococcal capsule formation has what advantage?
Increased resistance to opsonophagocytosis (complement still binds to cell wall surface but complement receptors can’t see it).
What are staphylococcal CHIPS?
Chemotaxis inhibitory protein of S. aureus
small secreted protein that represses neutrophil and monocyte chemotaxis induced by activated complement (C5a) and N-formyl peptide (but not chemotaxis mediated by IL-8)
Staphylococcal cytotoxins lyse which cells?
PMN leukocytes
Monocytes
Erythrocytes
What is alpha-haemolysin?
Staphylococcal cytotoxin that forms pores in the cytoplasmic membrane of RBCs, mononuclear WBCs, platelets, endo-/epithelial cells leading to cell lysis
Causes beta (complete) haemolysis on blood agar
What is beta-haemolysin?
Staphylococcal cytotoxin - sphingomyelase that degrades and weakens RBC membranes
Causes alpha (partial) haemolysis on blood agar
Name a staphylococcal leukotoxin
Panton-Valentine leukocidin (PVL)
- associated with severe skin infections
- LUK-1 gene in SP
- acts on PMN leukocytes in SP
What do the icaA/icaD genes in Staphylococci encode for?
Polysaccharide intercellular adhesion (PIA) - biofilm
What are the main types of resistance mechanisms in bacteria?
- Efflux – FQs, aminoglycosides, tetracyclines, beta-lactams, macrolides
- Immunity and bypass (bacteria become able to produce an alternative form of a protein that has a low affinity for the antimicrobial) – tetracyclines, trimethoprim, sulfonamides, vancomycin
- Target modifications – FQs, rifamycins, vancomycin, penicillins, macrolides, amoinoglycosides
- Inactivating enzymes – beta-lactams, aminoglycosides, macrolides, rifamycins
Which antibiotics target 50S inhibitors in protein synthesis?
Erythromycin (macrolides)
Chloramphenicol
Clindamycin
Lincomycin
Which antibiotics target 30S inhibitors in protein synthesis?
Tetracyclines
Streptomycin
Gentamicin
Amikacin
Which antibiotics target DNA-directed RNA polymerase?
Rifampin
Which antibiotics target folic acid metabolism?
Trimethoprim
Sulfonamides
Which antibiotics target DNA gyrase?
FQs
How do beta-lactamases inactive penicillin type antibiotics?
They hydrolyse the beta-lactam ring
Which gene encodes for beta-lactamase?
blaZ - typically resides on a large transposon on a plasmid
Both transglycosylation (attaching repeating units to the peptidoglycan strand) and transpeptidation (cross linking of repeating units) are carried out by which protein?
Penicillin-binding proteins
Transpeptidation is the specific target of β-lactams
Why is PBP2a resistant to beta-lactams?
The active-site serine of PBP2a is less accessible to β-lactams than with susceptible PBPs because of its location in a narrow extended cleft
Which gene encodes PBP2a and on which element?
mecA
Staphylococcal chromosome cassette (SCCmec)
What is the role of ‘J’ (junk) regions of SCCmec?
J regions are now commonly referred to as joining regions because they can encode important functions such as resistance to additional antibiotics and to heavy metals
What mediates excision and integration of SCCmec?
ccr-encoded recombinases located on SCCmec
FQs bind to DNA gyrase - what is it also known as? - and which other enzyme?
Topoisomerase II (DNA gyrase)
Topoisomerase IV
What is the primary target for FQs in G-ve and G+ve bacteria in veterinary species?
G-ve = DNA gyrase G+ve = Topoisomerase IV
FQ resistance occurs via two pathways; mutation of the target Topoisomerase II and IV or which other mechanism?
Efflux pumps
Tetracycline resistance in Staph.
tet (K) and tet(L) genes lead to which type of resistance mechanism?
Efflux pumps
No resistance to minocylcine
Tetracycline resistance in Staph.
tet(M) gene leads to which type of resistance mechanism?
Ribosome-protective protein (tet(M) most common in SP)
Resistant to minocycline
What are the intrinsic mechanisms of antibiotic resistance in Pseudomonas aeruginosa?
- Restricted outer membrane permeability (extremely restricted; about 12- to 100-fold lower than that of E. coli)
- Efflux pump systems
- Production of antibiotic-inactivating enzymes
(β-lactamases and aminoglycoside-modifying enzymes)
What is the mechanism of action of polymixins?
They bind to the lipopolysaccharides (LPS) on the outer membrane of Gram negative bacteria, leading to increased cell membrane permeability and enhanced antibiotic uptake.
Antibiotic resistance genes can be carried on which elements?
Plasmids, transposons, integrons and prophages
The main mechanisms of horizontal gene transfer involve which processes?
Conjugation, transformation and transduction
Which resistance gene confers resistance to all three types of macrolide antibiotic?
erm (mostly erm(B) in SP)
Modifies target site on ribosomes
What is the mechanism of action of rifampicin and the resistance gene?
Inhibits bacterial RNA polymerase
rpoB chromosomal mutation
What is the D-test?
Disk testing using erythromycin and clindamycin disks 15mm apart - with inducible resistance you see a flattening of the zone of inhibition nearest the erythromycin disk (‘D’ shape)
Which antibiotics can be used to test for meticillin resistance?
Oxacillin
Cefoxitin
Salt media can be used to select for which bacteria?
Staphylococci
Which element is a limiting factor for bacterial growth in tissue?
Iron (can be released by cell necrosis and utilised by the bacteria)
Conjugation is a method of horizontal gene transfer that is used most often by G+ve or G-ve bacteria?
Gram -ve
Which type of antibiotics are the only antimicrobials that act on ribosomes and cause cell death?
Aminoglycosides (e.g. gentamicin, amikacin, neomycin)
Rapid growing mycobacteria are more like pyogenic organisms and give rise to what type of inflammation?
Pyogranulomatous
With sinuses that drain watery pus
Slow growing mycobacteria may take 2-3 months to culture and produce what type of inflammation?
Granulomatous
Nodules to tumour like masses
Disseminated M. avium infection is seen in which breeds of cat associated with an inherited immune defect?
Abyssinian and Somali
When should you suspect rapidly growing mycobacteria?
- Non-healing wounds
- Atypical cat bite wounds
- “pepper pot” draining tracts
- Thickening or hardening of subcutis
- As a differential for Nocardia infection
Aspirates of purulent debris from intact lesions of suspected mycobacterial infection is most likely to yield a diagnosis through which test?
Culture - inoculate media immediately e.g. BACTEC system
Hard to find on cytology
Using intact lesion minimises growth of contaminants that could out compete
M. smegmatis isolates in Australia typically respond to which antibiotics?
Doxycycline and pradofloxacin
Clarithromycin unreliable for most M. smegmatis strains
M. fortuitum in the USA typically responds to which antibiotics?
Clarithromycin and pradofloxacin
Which antibiotics can be used in refractory cases of mycobacterial infection?
Clofamizine or linezolid
Should consider surgical treatment too
Which mycobacteria does rifampicin not treat?
Rapidly growing mycobacteria - intrinsic resistance
In bullous impetigo, an exfoliatin toxin-producing Staph. pseud. causes cleavage of which desmosomal protein?
Desmoglein-1
According to WAVD guidelines, which three Staphs are of primary importance in small animals?
Staphylococcus pseudintermedius, S. schleiferi (including the coagulase-negative variant) and S. aureus
Should you ask for complete speciation of all types of Staph and an antibiogram?
Yes - regardless of coag +ve or -ve
According to WAVD guidelines, a restriction-of-use policy should apply to which types of antibiotics?
- Glycopeptides (vancomycin, teicoplanin, telavancin)
- Linezolid (oxazolidinon)
- Anti-MRSA cephalosporins
Does strain typing of MRSP impact on patient- or clinic-level management?
Rarely
Used to investigate outbreaks
Are MRS susceptible to commonly used disinfectants?
Yes
When do you call MRS multi-drug resistant?
When it expresses co-resistance to at least two additional antimicrobial classes
Call it extensively drug resistant (XDR) if the strain is non-susceptible to all but two or fewer antimicrobial classes
True or false; feline nasal carriage of staphylococci is consistent with that carried by the humans in their households
True
The mouth and which other body site are nearly equal in sensitivity for identifying longitudinal colonization in dogs?
Perineum
How does coagulase factor help Staph evade the immune system?
It promotes formation of a fibrin clot scaffold for tissue invasion, is associated with abscess formation and protects staphylococcal micro-colonies (in vitro) against neutrophils
Name three major mechanisms/types of Staph virulence factors
- Biofilm formation
- Expression of adhesins by which the bacterium binds to cells and extracellular matrix
- Production of toxins (which may include cytolytic, exfoliative, enterotoxigenic and super-antigenic toxins)
- Expression of factors which assist in evasion of the host’s immune response
What are the subspecies of the coagulase variable S. schleiferi?
- S. schleiferi subsp. coagulans (coagulase-positive)
- S. schleiferi subsp. schleiferi (coagulase-negative)
Recent genotypic and epidemiological studies have shown that these two biotypes are not genotypically distinct enough to be considered true sub-species, nor do they differ in their pathogenic effects
Which CoNS (other than S. schleiferi schleiferi) have been isolated from skin and soft tissue infections in dogs and cats?
S. lugdunensis
S. haemolyticus
S. epidermidis
True or false; coagulase-negative S. schleiferi should generally be considered pathogenic when isolated from inflamed tissue or a pyogenic fluid
True
Name risk factors associated with transmission of MRSA within the community (people):
Crowded living conditions, shared bathing facilities and participation in contact sports
In dogs, both coag +ve and coag -ve S. schleiferi skin and ear infections have been statistically associated with which risk factors?
Prior antimicrobial use or recurrent pyoderma
How common is isolation of S. schleiferi from pyogenic infections of cats?
Very rare
Molecular diagnostic methods based on what type of testing are recommended for accurate species identification of CoPS?
PCR
MALDI-TOF provides a cost-effective alterative provided the database is validated
What are considered the gold standards for MR identification?
- PCR amplification of the MR gene mecA
- Commercial agglutination tests designed to detect its gene product (penicillin-binding protein 2a, PBP 2a or PBP 2’)
When should PCR for mecA or agglutination test for PBP2a be used?
To confirm presumed MRSA, MRSP or MRSS detected by oxacillin or cefoxitin susceptibility testing
Strains that are oxacillin/cefoxitin-resistant and mecA-positive or PBP 2a-producing should be reported as being resistant to which types of antibiotics?
All penicillins, cephalosporins (except anti-MRSA cephalosporins), carbapenems and cephems regardless of the in vitro susceptibility test results
Why do some MRSA strains display in vitro susceptibility to beta-lactams?
Due to poor in vitro expression of mecA in the presence of beta-lactams other than oxacillin and cefoxitin, which are used as surrogate drugs for this reason
According to WAVD, were the MICs for MRSP isolates high or low for common topical treatments such as chlorhexidine, miconazole, fusidic acid, mupirocin and polymyxin B?
Low
MRSA and MRSS strains often show susceptibility to tetracyclines and trimethoprim-potentiated sulfonamides, is the same true for MRSP?
No
Individual susceptibilities are infrequent and unpredictable and molecular studies have shown that the presence of individual resistance genes can vary even on a single mobile genetic element and within the same lineages
Do third generation cephalosporins (e.g. cefovecin, cefpodoxime) have efficacy against MRS?
No
Which test is used to identify inducible clindamycin resistance in MRS?
Erythromycin-clindamycin-D-zone testing
Which tetracycline resistance genes are most common in SP?
Tet(M) > tet(K)
Are amikacin, gentamicin, tobramycin, netilmicin and rifampicin considered highly or critically important for use in human medicine?
Critically important
Are chloramphenicol, doxycycline, minocycline and tetracycline considered highly or critically important for use in human medicine?
Highly important
Treatment outcome of MRS infections in small animals appears to depend on which factors?
Restoring the skin barrier function and removal of implants combined with antibacterial therapy, either by topical, systemic or intralesional route
What % of dogs show genetically identical isolates of MRSP from the pustules and mucosal sites?
80%
How common is environmental contamination with MRSP and what is it associated with once MRSP infection has resolved? (Frosini et al. 2022)
Seen in 43% of households and associated with positive carrier status
How common is MRSP carriage in dogs following infection?
62-67%
Do dogs carry MRSA for prolonged periods of time as they do MRSP?
No - studies suggest that dogs do not support MRSA carriage for long periods, at least in clean environments
Found in 2.6% of dogs sampled in Australia in communities with high levels of MRSA in people
What do WAVD recommend regarding isolation of MRSP infected individuals?
Restrict animals from contact situations until treatment has started and a clinical response is evident
In which situations is MRSP more likely and you should strongly recommend testing for MRSP?
- Animals with previous MRS infection
- Recent antimicrobial exposure
- Recent hospitalisation
- Animals that live with a person or animal with a history of MRS infection
The evidence for potential benefit from screening programs is strongest for which group of patients?
Surgical patients
True or false; veterinary personnel are known to be at elevated risk of MRSA and MRSP carriage in the absence of outbreaks
True
Should clinically normal animals be screened for MRS carriage?
Screening of clinically normal animals for carriage of MRS, regardless of the setting, rarely leads to clear and justifiable actions
Which two non-Staph bacteria can be isolated from dogs with SBF lesions?
Streptococcus canis Pseudomonas aeruginosa (and other Gram-negative bacteria)
Have hypo- and hyperpigmentation been reported with SBF in dogs?
Yes
In cases of SBF, when should cytology be considered mandatory?
- Typical lesions (pustules) are not present or scant and SBF is still suspected
- Typical lesions are present but there is a poor response to empirical antimicrobial therapy
- A bacterial culture is to be performed.
In SBF, inflammatory cells and phagocytosis may be absent in dogs with which underlying diseases/treatments?
Immunosuppressive diseases or those being treated with immunosuppressive agents, such as glucocorticoids
When should bacteriology be more strongly recommended in dogs with SBF?
- < 50% reduction in lesions within 2 weeks of appropriate systemic antimicrobial therapy
- Emergence of new lesions (papules, pustules, collarettes) 2 weeks or more after the initiation of appropriate therapy
- Residual SBF lesions after 6 weeks of appropriate systemic antimicrobial therapy together with the presence of cocci on cytology
- Intracellular rod-shaped bacteria
- Prior history of MDR infection in the dog or in a pet from the same household
In the SBF guidelines (2014), was there evidence that current use of AMDs had a significant effect on isolation of causative bacteria from dogs with persistent SBF, e.g. do you need to withdraw treatment before swabbing?
No
What % of MRSP isolates show MDR to three or more antibiotics routinely used in veterinary medicine?
97.8%
How often is SP isolated from canine pyoderma?
(74-)92%
Name three adhesion molecules/factors for Staph.
MSCRAMMS (adhesion proteins) e.g.: - Teichoic acid - Lipoteichoic acid - Fibronectin binding proteins - Fibrinogen binding proteins - Iron-regulated surface protein A - Collagen binding proteins Slime coating
Name an enzyme that allows Staph. to move through the epidermis and dermis
Protease
Hyaluronidase
Lipase
The __________-rich structure of Staph. Gram-positive cell wall renders the bacterium resistant to MAC formation
Peptidoglycan
Another major serum protein with anti-bacterial effects is __________, an iron binding protein that can deprive bacteria of an important cofactor for growth and reproduction
Transferrin
Of all the known human TLRs(1–10), ____ has been the most implicated in host defence against S. aureus
TLR2
Which intracellular cytoplasmic receptor can recognize the S. aureus peptidoglycan breakdown product muramyldipeptide?
NOD-2
Keratinocytes release which cytokine after interaction with Staph.?
IL-1
Staphylococci can inhibit neutrophil recruitment to sites of infection by secreting various molecules such as staphylococcal superantigen-like protein-5 and protein-11. How do they work?
These proteins block the interaction between P-selectin glycoprotein ligand 1 (PSG-1) on the neutrophil surface and P-selectin on the endothelial lining - blocking neutrophil rolling.
How does staphylococcal extracellular adherence protein block leukocyte adhesion?
Inhibits the binding between ICAM-1 and Mac-1 or LFA-1
IL-17 is a key cytokine in the defence against S. aureus as it stimulates _______ recruitment to the site of infection and promotes abscess formation
Neutrophil
What three major effects do antibodies have on Staph. infections?
- Act as neutralising antibodies, binding to the pathogen to prevent its attachment to host target surfaces
- Act as opsonizing antibodies
- Bind to pathogens and activate the classical complement pathway
Why do you not see acantholytic cells in exfoliative superficial pyoderma?
SIET and SPETA were detected and these toxins do not cleave desmoglein-1
Name three options for Staph. strain typing
- Pulse field gel electrophoresis (good for outbreak investigation; discriminatory but not repeatable between labs)
- MLST (7 house-keeping genes; evolution not outbreak, costly)
- Spa typing (cost-effective, rapid)
- SCC mec typing (can’t detect new variants)
- Microarray (DNA probes; highly accurate but expensive and time consuming)
- Whole genome sequencing (gold standard if available)
Name risk factors for MRSP in dogs
Previous antibiotic therapy, hospitalisation, repeated veterinary visits, chronic skin and ear disease (including chronic allergic disease)
Should you use MRSP to make bacterin treatment?
No - persistence of mecA in MRSP bacterins suggests that dispersal of this important resistance mediator through therapy may be possible
Does bathing in carbonated water help treat SBF in dogs?
Yes - significant improvement in the clinical scores and reduced skin pH compared to bathing in tap water
What % of Staph. isolates from veterinary staff, dogs and cats within a veterinary hospital from nasal swabs were meticillin resistant? Thomson et al. (2022)
48.7% of the humans, 26.5% of the dogs and 57.1% of the cats
Is cold atmospheric microwave plasma (CAMP) effective against bacteria associated with canine skin and ear infections?
- Gram-negative bacteria (P. aeruginosa and E. coli) were more susceptible than Gram-positive bacteria (S. aureus and S. pseudintermedius)
- Only the Gram-negative bacteria were completely killed after 60 s exposure.
- CAMP exposure had similar antibacterial effects regardless of antibiotic resistance in SP
It works through the action of reactive oxygen species and reactive nitrogen species released during plasma generation
In the study by Bierowiec et al. (2021), were cats more or less frequently colonised with SP if they lived with dogs?
More frequently SP colonised
What kind of light is used for phototherapy?
Narrow-band UVB light at a 308-nm wavelength
What effect does phototherapy have on atopic skin disease in dogs?
- Significantly increased the relative abundance of the phyla Actinobacteria and Cyanobacteria.
- Significantly alleviated the clinical signs of canine atopic dermatitis without serious adverse effects.
- Transepidermal water loss significantly decreased after phototherapy.
- Increased microbial diversity and decreased relative abundance of Staphylococcus pseudintermedius
Is there evidence of antimicrobial peptide production from bacteria that can inhibit growth of SP and SA?
Yes - from CoNS in people and S. felis in cats
In the study by Nocera et al. (2021), were CoPS or CoNS most prevalent in cats with skin and ear infections?
CoNS
In the paper by Papic et al. (2021), what was highlighted as an important factor in spread of MRSP in veterinary clinics?
MRSP positive dogs
In the study by Ferrer et al. (2021), how did SP isolates differ from healthy dogs and those with pyoderma?
Pyoderma isolates contained a higher number of antimicrobial resistance genes
The total number of virulence factors genes did not differ between healthy dogs and dogs with pyoderma
Did the use of Ophytrium and chlorhexidine digluconate 3% pads (Douxo Pyo) daily for 14 days improve lesions/microbial counts in dogs with localised dysbiosis (bacteria and/or Malassezia)?
Yes - improved the skin condition and pruritus of dogs with local dysbiosis; 88.9% of dogs achieved a ≥70% microbial decrease
Is a prednisolone plus pomegranate otic suspension as effective as a prednisolone plus antibiotic and antifungal suspension to treat non-purulent OE in dogs?
Yes - increased fungal diversity (Shannon index) and composition was the most significant change observed after both treatments. Both groups showed significant clinical improvement
Is olanexidine gluconate (a broad-spectrum bactericidal solution) as effective as chlorhexidine against SP?
Yes - daily spray of olanexidine vs weekly bath with chlorhexidine
What are bacteriophages?
Viruses that specifically infect bacterial cells and enter either a lytic or a lysogenic cycle. Lytic phages use the host machinery for their replication and dissemination of genetic material, leading to cell disruption.
What effect can fluorescent light energy therapy have on treatment of deep pyoderma with systemic antibiotics in dogs?
It is a blue light-emitting diode(LED) device and a topical photoconverter gel, which when illuminated by the LED device, emits low-energy light in the form of fluorescence
It can accelerate time to clinical resolution
Seen with CPIF too
What dose of rifampicin did Hicks et al. (2021) recommend to minimise the risk of rifampicin resistance developing in MRSP infections?
> 6 mg/kg total daily dose
Did García-Fonticoba et al. (2020) find evidence of microbes in the dermis and subcutis of healthy dogs?
No - they found the dermis and subcutaneous tissue of dogs are sterile
Which MRS have been isolated from grooming salons in the US?
Meticillin-resistant S. pseudintermedius, S. aureus and S. schleiferi
Which risk factor was associated with high levels of clindamycin resistance in MSSP (37.7%) in dogs in the Netherlands?
Prior antimicrobial treatment
Specific IgE and total IgG against M. pachydermatis and S. pseudintermedius were significantly increased in atopic dogs of all age; did this correlate with CADLI score?
No
No significant relationships were found between the CADLI and any specific immunoglobulin levels for both microbe types
Tang et al. (2020); compared to healthy samples, 78.3% of clinically affected ear samples had microbial overgrowth; 69.8% bacterial overgrowth, 16.3% fungal overgrowth, and 7.0% had both bacterial and fungal overgrowth. Which fungi/bacteria were most abudant?
Malassezia pachydermatis, Staphylococcus pseudintermedius, Staphylococcus schleiferi
Plus few anaerobic bacteria such as Finegoldia magna, Peptostreptococcus canis, and Porphyromonas cangingivalis
de Jong et al. (2020); the main species isolated from dogs with skin/ear/wound infections were Staphylococcus pseudintermedius, followed by Streptococcus spp., Pseudomonas aeruginosa and Escherichia coli. Which species were most common in cats?
Pasteurella multocida, coagulase-negative staphylococci (CoNS) and Staphylococcus aureus
Lim et al. (2020); what % of SP isolates from dogs with pyoderma or OE were resistant to fusidic acid?
27%
All showed low-level resistance.
W16P576, which is a Water Extract of Complex Mix of Edible Plants (WEC-MEP), has previously has been tested in vitro against MSSP and MRSP isolates and can inhibit bacterial growth. Did it affect clinical lesions of pyoderma in a canine model?
Treatment with W16P576 significantly reduced lesion development and hastened resolution of lesions, compared to placebo.
Has a sodium hypochlorite and salicylic acid shampoo been shown to be effective at treating MRSP superficial pyoderma in dogs?
Yes
In the study by Meroni et al. (2019), what % of SP isolates could produce biofilm and what did this correlate with?
95% (98% in NAVDF abstract Volk 2021)
A clear correlation was found between antibiotic-resistance and the ability to produce biofilm
Chlorhexidine and azole containing mousses had residual activity in inhibiting S. pseudintermedius growth in vitro for how many days?
Up to 10 days
Frosini et al. (2019); was fucidic acid and chlorhexidine resistance detected in MSSP, MRSP, MSSA and MRSA from dogs?
Increased FA MICs were frequently associated with fusA mutations and fusC, and this is the first account of fusB in SP; mutations correlated with ‘low level’ resistance.
Despite novel description of qacA/B in SP, gene presence did not correlate with CHX MIC.
Rafferty et al. (2019), what effect did chlorhexidine and acetic acid/boric acid (AABA) wipes have on bacterial growth?
CHX but not AABA showed in vitro efficacy against MSSP, MRSP, E. coli and Malassezia. ESBL-EC were less susceptible and there was no activity against Pseudomons aeruginosa. There was no residual activity on hair taken from treated dogs.
Has alpha-mangostin in mangosteen crude extract been shown to be effective in inhibiting growth of MRSP and MSSP in vitro?
alpha-mangostin induces a rapid, concentration-dependent, membrane disruption that has a bactericidal effect
Yes
Have autogenous bacterin vaccines been shown to reduce systemic antibiotic therapy in dogs over a 12 month period?
Yes
Has pyoderma gangrenosum been reported in dogs?
Yes - very rare
Neutrophilic dermatosis with ulcerative lesions with an undermined, violaceous edge
What are the minor criteria for pyoderma gangrenosum in people?
- history suggestive of pathergy (new lesions forming in response to minor trauma) OR cribriform scarring
- systemic diseases associated with PG
- consistent histopathological findings (sterile dermal neutrophilia)
- rapid response to systemic steroid treatment
Are AMP secretion levels different in atopic and non-atopic dogs?
No
Lesions of SBF may harbour multiple (up to 4) S. pseudintermedius strains with distinct antimicrobial resistance profiles. Which lesions are the best target for bacteriology?
Pustules are the best target for bacterial culture.
Narasin, a polyether ionophore conventionally used as a rumen modifier and anticoccidial agent in production animals, was effective against which types of isolates from canine OE?
Gram +ve bacteria and at high concentrations, Malassezia
Not effective against Gram -ves
Which bacteria were reported to be associated with malodour in bloodhounds?
Psychrobacter and Pseudomonas spp.
In dogs with atopic dermatitis, have similar changes to the microbiota of the skin been reported in the ear canal?
Yes - increased abundance of Staphylococcus spp. and Ralstonia spp.
Were serum levels of CRP higher in normal dogs, dogs with superficial pyoderma or with PF?
CRP levels are increased in dogs with PF and exceed levels found in most dogs with SP
Dogs with CRP >10.6lg/mL were 5.5 times more likely to have PF than SP
Has honey been shown to be effective in vitro at treating SP and Malassezia?
Yes
VIM-2-producing P. aeruginosa have been reported in dogs, what is VIM-2?
VIM-2 = metallo-beta-lactamases (MBLs) = carbapenemases
Has honey been shown to improve clinical signs and cytological scores in dogs with nasal intertrigo?
No - only pruritus improved compared to placebo
What % of dogs receiving rifampicin show GI signs (vomiting, anorexia etc.)?
15-16%
True or false; increased ALT and ALP levels with rifampicin treatment are significantly associated with length of treatment course
True (mild increases likely associated with liver enzyme induction rather than hepatotoxicity)
Monitor as hepatoxicosis has been reported
How quickly can you see as response with rifampicin therapy for MRS pyoderma?
1-2 weeks
Which is most effective at reducing clinical scores and bacterial counts in dogs with superficial pyoderma, 3% chlorhexidine or benzyl peroxide shampoo?
3% chlorhexidine
Are MICs for MRSP and MSSP of combined chlorhexidine/miconazole higher or lower than either drug used alone?
Lower
Kloos et al. (2013), found which types of shampoo lead to the greatest zones of inhibition of SP growth on agar plates using treated hair?
Hair shafts treated with shampoos containing 2 and 3% chlorhexidine and the combination of shampoo and conditioner inhibited bacterial growth significantly
Is topical chlorhexidine therapy with 4% chlorhexidine digluconate shampoo (twice weekly) and solution (once daily) for 4 weeks as effective at treating superficial pyoderma as systemic amoxyclav?
Yes - also successfully resolved MRSP pyoderma
Binding to __________ represents the major mechanism involved in the adhesion and uptake of S. aureus into keratinocytes
Integrin alpha-5-beta-1 of epithelial cells via fibronectin
Which gene is responsible for vancomycin resistance in S. aureus?
vanA - plasmid
What are the three types of vancomycin resistant S. aureus?
- vancomycin-intermediate Staphylococcus aureus (VISA)
- vancomycin-resistant Staphylococcus
aureus (VRSA) - heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) - precursor to VISA
In the UK, which animal is considered the reservoir host for Mycobacterium microti?
Field vole
The_______ - release assay is showing promise for detecting members of the tuberculosis complex in cats
Interferon-gamma
Are MNGCs typically seen with M. microti infection in cats?
No
How long should you treat cats for tuberculosis?
The initial phase usually requires at least three drugs (e.g. rifampicin–fluoroquinolone–clarithromycin / azithromycin) and lasts for 2 months, while the continuation phase requires two drugs and lasts for perhaps a further 4 months, depending on the extent of the disease
M. avium induces _____ immune response and avoids apoptosis in infected canine cells
Th17
True or false; among the nontuberculous mycobacteria, Mycobacterium avium complex (MAC) is the leading cause of pulmonary disease in humans
True
Which dog breeds are predisposed to MAC infection?
Miniature Schnauzer and Basset Hound
True or false; mycobacteriosis is caused by opportunistic pathogenic nontuberculous mycobacteria that are ubiquitous, e.g. in soil and water
True
MAC infection has been associated with a mutation in which gene in Miniature schnauzers?
CARD9 - a multi-functional signaling protein and is essential in autonomous innate host defense
Can tuberculin skin tests be used to diagnose mycobacterial infection in dogs or cats?
No
In canine leproid granuloma, can the mycobacteria involved by cultured?
No - this prevents full chemotaxonomic analyses and susceptibility testing
Do cats with mycobacteriosis typically test positive for FIV/FeLV?
No
PCR for mycobacteria is most sensitive on which type of tissue sample?
Fresh»_space; FFPE
What type of mycobacterium is M. kansasii?
Slow-growing non-tuberculous mycobacteria
Has Mycobacterium nebraskense been reported in cats and dogs
Yes - rarely
Tuberculous cats have low serum __________ concentrations, which influences macrophage function
Vitamin D
Mycobacterial infection in cats; where cell mediated immune response is poor, ____________ change is typical, with large numbers of AFB and if cell mediated immunity is more robust, a __________ response is likely, with few AFB
Lepromatous
Tuberculous
M. Tarwinense typically affects which body sites in feline leprosy?
Ocular and face/nose
M. lepraemurium typically causes lesions at which body sites in feline leprosy?
Lip, face, limbs
Hunting rodents
M. lepraefelis (feline leprosy) have lesions at which body sites?
Generalised including internal organs
M. lepraefelis as a cause of feline leprosy is seen in old or young cats?
Older, immunocompromised cats
Other types are seen in young, hunting cats
What are the clinical signs of dermatophilosis in cats?
In cats, the subcutaneous tissues, muscle and lymph nodes are more commonly affected.The popliteal lymph node area has been reported as a typical area of infection for cats.
Necrotising fasciItis is most often associated with which bacteria?
Streptococcus canis
Less commonly SP, E. coli and Acinetobacter baumannii
What are the clinical signs of necrotising fasciitis?
Acute, markedly painful inflammation and oedema which can involve a limb or the trunk or neck; skin is discolored/devitalized and drains serohemorrhagic fluid
What are the systemic signs of necrotising fasciitis?
Affected animals are systemically ill, febrile, weak, hypotensive (canine streptococcal toxic shock syndrome)
What type of therapy is critical for necrotising fasciitis?
Surgical debridement
What are the histopath findings in necrotising fasciitis?
Coagulation necrosis of the fascia and subcutaneous fat, neutrophilic infiltration of the dermis and fascia, and thrombosis of the adjacent vessels
Which antibiotics should you use to treat necrotising fasciitis (while bacteriology results are pending)?
Clindamycin
Beta-lactams
Gentamycin
Avoid NSAIDs and fluoroquinolones, as they have been associated with poorer outcomes!
Which treatments are associated with a good outcome in necrotising fasciitis?
- Early and repeated surgical debridement inclusive of negative pressure wound therapy (NPWT) was associated with a good outcome
- Hypobaric oxygen therapy may also be helpful
Name Strep. virulence factors
- Fibronectin binding proteins (bind to fibronectin on host cells as Staph)
- Streptococcal M protein (major antiphagocytic factor - inhibits opsonization)
- Streptolysin O
What are the clinical signs of nocardiosis?
- Chronically draining wounds/abscesses or ulcerated pyogranulomatous nodules that often occur on ventral abdomen in cats or on the limbs
- Lymphadenopathy common and pyothorax can occur.
- Small tissue granules may be present.
- Pulmonary or cutaneous disease can progress to disseminated disease.
- Underlying immunosuppressive disease often present.
How do you diagnose nocardiosis?
Cytology of FNA, aerobic culture (slow-growing) and biopsy
What do nocardia look like?
Gram‐positive, partially‐ acid‐fast, and filamentous with right angle branching bacteria (may look like Chinese letters)
How do you treat norcadiosis?
Surgical debridement and systemic antibiotics (e.g. TMPS, tetracyclines, erythromycin, cephalosporins)
What are the clinical signs of actinomycosis?
- Firm and fibrous masses, chronic abscesses, draining tracts, and osteomyelitis.
- Pyothorax or peritonitis can occur.
- Purulent exudate may be odorous and may contain yellow tissue granules.
How do you diagnose actinomycosis?
Cytology, biopsy and anaerobic culture (cf nocardia which is aerobic - slow growing)
How do you treat actinomycosis?
Surgical debridement and systemic penicillins
What is bacterial pseudomycetoma?
- Chronic, suppurative, granulomatous lesions caused by non-branching bacteria (most commonly CoPS)
- Firm nodules with draining tracts and small white granules (like grains of sand)
What is the best type of sample for cytology and culture of acral lick lesions?
Biopsy
Cytology can be performed on exudate if the skin is cleaned before exudate is expressed (painful!)
Acral lesions typically affect small or large breed dogs?
Large breed dogs
Doberman pinscher, Great Dane, Labrador retriever, golden retriever, German shepherd, boxer, Weimaraner, and Irish setter as reported predisposed dog breeds.
What are the perpetuating factors of acral lick dermatitis?
Secondary bacterial infections, keratin foreign bodies as a result of licking and furunculosis, bony changes such as osteomyelitis or periostitis, and development of a secondary compulsive disorder/learned behaviour
Conventional therapy for ALD includes systemic antibiotics for the deep bacterial infection and a systemic behaviour-modifying medication (i.e. fluoxetine, clomipramine). Is low light laser therapy beneficial for dogs with acral lick dermatitis?
No -
Pseudomonas aeruginosa contamination of grooming products was present in what % of products and was associated with which risk factor?
12%
Dilution with water
Post grooming furunculosis occurs how long after bathing?
Median 2 days
Pseudomonas aeruginosa is the most common isolate from post grooming furunculosis; what are the histopath findings and which other bacteria has been reported?
Acute follicular rupture in the superficial dermis with suppurative inflammation and dermal haemorrhage.
Serratia marcescens
What is the typical presentation of pyotraumatic dermatitis in dogs?
- Males > females
- More common in dogs < 4 years
- Cheek, neck and lateral thigh
- All rottweilers had lesions on the head (cheek, neck) and all GSDs showed lesions of the rump
- Rottweiler, GSD and golden retriever most common
What are the histopathology findings in pyotraumatic dermatitis in dogs?
- Necrosis or ulceration of the epidermis with superficial dermal oedema and neutrophilic (+/- eosinophilic) infiltrates
- 45% showed superficial and/or deep folliculitis
Which phylum do Staphylococci belong to?
Firmicutes
How was the microbiota of healthy horses affected by season?
Alpha diversity was higher in the winter and summer than spring and autumn although this was not statistically significant
