10. klebsiella, proteus, and moraxella

klebsiella gram stain

gram negative rods

what is the most clinically relevant species of klebsiella?

k. pneumoniae

what is klebsiella’s key virulence factor?

capsule

• protects from phagocytosis

• avoid complement and antimicrobial peptides

• block opsonization with antibodies

where is klebsiella normally found?

• GI and urogenital tract (humans, domestic animals, and wildlife)

• ubiquitous in soil and water

• non-motile

general predisposing factors to klebsiella infection

• breach of barrier

• dysbiosis of the microbiota

• immunosuppression state

what is an important factor to consider when treating klebsiella?

multi-drug antibiotic resistance → antibiotic sensitivity test essential!

what types of infections can klebsiella cause in domestic species?

• equine pneumonia

• equine endometritis

• bovine mastitis

• canine UTIs

• often associated with nosocomial infections

sources of infection for klebsiella equine pneumonia

• inhalation during prolonged transport (when horse’s head is immobilized): shipping pneumonia

• inhalation during strenuous exercise

• mechanical ventilation (during anesthesia)

  • moist environment of tubing is favorable for colonization

klebsiella equine pneumonia clinical signs

• fever

• tachypnea

• bloody nasal discharge*

• laminitis* — shifting lameness, warm feet

**note: evidence of bloody nasal discharge and/or laminitis worsens prognosis

klebsiella equine pneumonia pathogenesis

profound systemic inflammation caused by lack of clearance (capsule protection) and high levels of endotoxemia (LPS) lead to vascular dysfunction and tissue damage

klebsiella equine pneumonia diagnosis & prevention

diagnosis

• culture

• antibiotic sensitivity (multi-drug resistance!)

prevention

• sterilize anesthesia equipment & strict hygiene protocols

• avoid halter-tying horses during transport

equine endometritis transmission (klebsiella)

most likely an ascending infection from colonized mares, but often seen as transmitted during breeding or cervical examination (evidence is lacking)

equine endometritis clinical signs/consequences (klebsiella)

clinical signs

• vaginitis, cervicitis, endometritis

• may or may not be clinically evident

consequences

• reproductive failure caused by inflammation that interferes with implantation of conceptus

equine endometritis diagnosis (klebsiella)

• culture

• cytology (with signs of inflammation)

• antibiotic sensitivity

equine endometritis prevention & treatment (klebsiella)

• screen stallions and mares before breeding season

• separation of infected mares

• treat with antibiotics; keep in mind resistance is frequent

sources of klebsiella in bovine mastitis

• bedding materials → moist wood shavings

• milking equipment

• fecal contamination

• calf oral cavity

clinical signs/consequences of bovine mastitis (klebsiella)

clinical signs

• subclinical to local acute (hot, hard, or swollen quarter)

• can be severe with systemic illness, potentially progressing to recumbency and death

consequences

• can develop chronic mastitis; milk may appear normal but has high somatic cells

• recurrent mastitis and milk production loss

bovine mastitis treatment/prevention

treatment

• systemic antibiotics

• intramammary antimicrobials

• cure rates are low (approx. 50%)

prevention

• store bedding in clean, dry place

• milking hygiene

• keep alleyways and holding pens clean

• segregate contaminated cows

klebsiella associated diseases in companion animals

• prostatitis/UTIs

• can also have:

  • pyometra

  • pneumonia

  • bloodstream infections

  • nosocomial infections in hospitalized animals

predisposing factors to klebsiella in companion animals

• compromised innate immunity

• long-term antibiotic therapy

proteus gram staining

gram negative rods

what are the most clinically relevant species of proteus?

p. mirabilis and p. vulgaris

where is proteus normally found?

• part of normal GI microbiota of humans and animals

  • ascending infections

• present in soil and water (elevated in polluted environments)

what types of infections can proteus cause in companion animals?

• otitis externa

• urinary tract infections

proteus UTI diagnosis

culture and sensitivity testing (less antibiotic resistance than klebsiella)

risk factors for UTIs

• loss of normal microbiota within the lower urogenital tract

• mechanical disruption of the barrier

• any anatomic or functional defect that prevents complete voiding or urine

• changes in urine composition that support bacterial growth

what are potential complications of proteus UTIs?

• struvite stones

• pyelonephritis

what are the key virulence factors for proteus?

• peritrichous flagella → allows movement on medical equipment and in tissues; more invasive infections

• high production of urease

• proteases like ZapA

• LPS → induce inflammation

how does urease contribute to proteus pathogenesis?

increases pH of urine → crystal formation

struvite stones

magnesium, ammonium, and phosphate = nutrient-rich and protective environment for bacteria

how do proteases contribute to proteus pathogenesis?

• degrade IgA

• can also cleave complement, cell-matrix proteins, and some antimicrobial peptides

moraxella gram stain

gram negative coccobacilli

what is the most clinically relevant species of moraxella?

m. bovis

where is moraxella normally found?

• inhabitant of mucosal surfaces (upper respiratory tract, ocular conjunctiva, genital mucosa)

• can be part of the normal microbiota

what disease is moraxella commonly associated with in domestic species?

infectious bovine keratoconjunctivitis (IBK); very costly and common ocular infection

how is moraxella transmitted?

• can be directly from animal to animal or indirectly via insects or fomites (animal handlers)

• highly contagious

moraxella diagnosis

• identification of gram-negative rods in corneal exudates and culture

• PCR

• MALDI-TOF

clinical signs of IBK

• excessive tearing

• conjunctivitis

• photophobia

• corneal edema

• cloudiness usually develops within 24-48 hours, with central corneal ulceration

consequences of IBK

• high morbidity, with debilitating pain and potential blindness

• animals go off feed → production loss

predisposing factors of IBK

• anything that disrupts innate defenses of the eye

  • foreign bodies, flies, dust, pollen, UV radiation, woody pasture plants

• co-infections (infectious bovine rhinotracheitis virus, adenovirus, mycoplasma spp., listeria, nematodes)

what are key virulence factors for moraxella?

• pili (Q and I)

• exotoxin Mbx

• lipooligosaccharide (LOS)

how do pili contribute to moraxella pathogenesis?

mediate adhesion to damaged conjunctival and corneal epithelial cells

exotoxin Mbx (moraxella)

hemolytic cytotoxin that forms pores on epithelial cells and neutrophils → trigger inflammatory response

lipooligosaccharide (moraxella)

• similar to LPS but lacks O-antigen

• induces inflammation but gives higher serum resistance

IBK treatment/prevention

treatment

• essential to treat early with antimicrobials (IM/IO/systemic)

• use of eye patch is beneficial

prevention

• fly control and environmental control (e.g. mowing pastures) → prevention is important!

• several commercial vaccines available (poor evidence of efficacy)