Bacterial diseases

The vast majority of non-traumatic diseases in cats are caused by bacteria or their secondary involvement in the disease process.

Three broad groups of bacteria exist, defined by their ability to uptake Gram stain. Gram positive bacteria stain a crystal violet color due to the presence of a peptidoglycan cell wall. Gram negative bacteria fail to take up the Gram stain and normally take up the counterstain (safranin or fuchsine), and usually have a red or pink color under the microscope.

This is important, primarily, with choice of antimicrobial therapy.

• Gram-positive bacteria - peptidoglycan cell wall
• Gram-negative bacteria - lipopolysaccharide membrane
• Proteobacteria - are all Gram-negative, with an outer membrane mainly composed of lipopolysaccharides. Many move about using flagella, but some are nonmotile or rely on bacterial gliding. The last include the myxobacteria, a unique group of bacteria that can aggregate to form multicellular fruiting bodies. There is also a wide variety in the types of metabolism. Most members are facultatively or obligately anaerobic, chemoautotrophs, and heterotrophic, but there are numerous exceptions.
• Alphaproteobacteria - includes Wolbachia spp, Bartonella spp, Rickettsia spp, Brucella spp, Ehrlichia spp and Anaplasma spp. These are obligate intracellular endosymbionts living within host cells.

Bacteria, in general, can cause varying ranges of illness in cats from mild dermatitis to sepsis and death. Cats can also transmit bacterial diseases to humans (zoonoses).

Appropriate antimicrobial therapy should be based on isolation and culture and sensitivity of causative bacteria.

Bacterial resistance, especially to pathogenic Salmonella spp, methicillin-resistant Staphylococcus aureus and extended spectrum β-lactamase-producing E. coli mirrors the growing bacterial resistance in human microbiology.

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Significant bacteria associated with cat health and disease include:

Species	Classification	Location in cats	Disease
Acinetobacter baumannii	Gram -ve, aerobic proteobacteria	GI tract	FLUTD, Vaginitis, zoonotic
Actinobacillus spp	Gram -ve, anaerobic	oropharynx	gingivitis
Actinomyces spp	Gram +ve, aerobic/anaerobic	GI tract	systemic infections
Aggregatibacter actinomycetemcomitans	Gram -ve, anaerobic	oropharynx	gingivitis, bite wounds
Alcaligenes faecalis	Gram -ve, aerobic proteobacteria	reproductive/urinary tracts	otitis externa, cystitis, nosocomial infections
Anaerobiospirillum spp	Gram -ve, anaerobic	GI tract	ulcerative colitis
Anaplasma spp	Gram -ve, proteobacteria	blood	anemia, tick-borne fever
Arcanobacterium spp	Gram +ve, aerobic	skin	otitis externa
Arcobacter spp	Gram -ve, microaerophilic	GI tract	nonpathogenic, zoonotic
Bacteroides spp	Gram -ve, aerobic	GI tract	bacteremia
Bartonella spp	Gram -ve, anaerobic proteobacteria	blood	systemic disease
Bifidobacterium spp	Gram +ve, anaerobic	GI tract	preventative probiotic
Bordetella bronchiseptica	Gram -ve, proteobacteria	respiratory tract	cat flu
Borrelia burgdorferi	Gram -ve, spirochaete	blood	anemia, tick-borne fever
Burkholderia pseudomellei	Gram -ve proteobacteria	skin, GI & respiratory tract	melioidosis
Campylobacter spp	Gram -ve, microaerophilic	GI tract	secondary diarrhea
Capnocytophaga canimorsus	Gram -ve, anaerobic	oropharynx	zoonotic (bite wounds to humans)
Chlamydophila spp	Gram -ve, aerobic	skin, respiratory tract	conjunctivitis and, rarely, pneumonia
Citrobacter spp	Gram -ve, aerobic	GI tract, reproductive tract	cystitis
Clostridium spp	Gram +ve, anaerobic	GI tract, skin	diarrhea, tetanus
Corynebacterium spp	Gram +ve, aerobic/anaerobic	skin, GI, urinary and reproductive tracts	cystitis, abscess
Coxiella burnetti	Gram -ve, anaerobic	respiratory tract	zoonotic (Q fever)
Desulfovibrio spp	Gram -ve, anaerobic proteobacteria	gastrointestinal biotome	IBD
Ehrlichia spp	Gram -ve proteobacteria	blood	anemia
Enterobacter spp	Gram -ve, anaerobic proteobacteria	respiratory & urinary tract	cystitis
Enterococcus spp	Gram +ve, anaerobic	gastrointestinal tract	diarrhea, periodontitis, peritonitis, cystitis
Escherichia spp	Gram -ve, anaerobic	GI, reproductive, urinary tracts	diarrhea, pyometra, peritonitis, pneumonia
Flexispira spp	Gram -ve, microaerophilic spirochaete	GI tract	gastritis
Francisella tularensis	Gram -ve, aerobic	oropharynx	tularemia
Fusobacterium spp	Gram -ve, anaerobic	skin, GI tract	periodontitis, cellulitis and pyothorax
Haemophilus spp	Gram -ve, aerobic/anaerobic proteobacteria	GI & respiratory tract	cystitis, meningitis
Helicobacter spp	Gram -ve, microaerophilic proteobacteria	GI tract	gastritis
Klebsiella spp	Gram -ve proteobacteria	respiratory tract	pneumonia
Lactobacillus spp	Gram +ve anaerobic	gastrointestinal tract	part of healthy gut biotome
Leptospira spp	Gram -ve, aerobic spirochaete	GI & urinary tract, blood	leptospirosis, cystitis
Listeria monocytogenes	Gram +ve, anaerobic	GI tract	tonsillitis, diarrhea
Mycobacterium spp	Gram +ve, aerobic	skin, GI & respiratory tract	leprosy and TB
Mycoplasma spp	Gram -ve, aerobic	respiratory tract	pneumonia, pyothorax
Neisseriaceae spp	Gram -ve, aerobic proteobacteria	respiratory tract	pneumonia, zoonotic bite wounds
Nocardia spp	Gram +ve, aerobic	oropharynx, wounds, respiratory tract	granuloma, pneumonia, pyothorax
Pasteurella multocida	Gram -ve, anaerobic	skin	zoonotic bite wounds
Peptostreptococcus spp	Gram +ve, anaerobic	skin, GI and genitourinary tracts	pyothorax
Porphyromonas gingivalis	Gram -ve, anaerobic	GI tract	periodontitis
Prevotella melaninogenicus	Gram -ve, anaerobic	GI tract	bite-wound related osteomyelitis, gingivitis
Propionibacterium spp	Gram +ve anaerobic	skin	pyothorax, anal sacculitis
Proteus spp	Gram -ve, anaerobic proteobacteria	skin,	cystitis, paronychia and various other skin diseases
Pseudomonas spp	Gram -ve, aerobic proteobacteria	skin, GI and respiratory tracts	pneumonia
Rhodococcus spp	Gram +ve, aerobic	skin, respiratory tract	pyothorax, cellulitis and pyogranulomas
Rickettsia spp	Gram -ve, anaerobic proteobacteria	blood	tick-borne fever
Salmonella spp	Gram -ve, anaerobic proteobacteria	GI tract	food spoilage diarrhoea
Serratia marcescens	Gram -ve, aerobic	skin	endocarditis, nosocomial infection
Shigella spp	Gram -ve, anaerobic proteobacteria	GI tract	rare cause of diarrhoea
Simonsiella spp	Gram -ve, aerobic proteobacteria	respiratory tract	pneumonia, zoonotic bite wounds
Staphylococcus spp	Gram +ve, aerobic	skin, GI & respiratory tract	superficial and systemic infections
Streptococcus spp	Gram +ve, aerobic	skin, GI & respiratory tract	superficial and systemic diseases
Streptomyces spp	Gram +ve, aerobic	skin, GIT	cellulitis, lymphadenitis
Stenotrophomonas maltophilia	Gram -ve, aerobic proteobacteria	skin, GI tract	nosocomial infection, cystitis, chronic lung disease
Tannerella forsythia	Gram -ve, anaerobic	oropharynx	periodontitis, bite wounds
Treponema denticola	Gram -ve, aerobic spirochaete	GI tract	periodontitis, zoonotic bite wounds
Wolbachia spp	Gram -ve anaerobic proteobacteria	endosymbiont within D. immitis	nonpathogenic
Yersinia pestis	Gram -ve, anaerobic	GI tract	plague