Clinical Bacteriology: Non-Fermentative Gram-Negative Bacilli

Comprehensive review flashcards covering non-fermentative gram-negative bacilli, their general characteristics, biochemical profiles, identifying features, virulence factors, and associated clinical infections.

How are non-fermentative gram-negative bacilli defined in terms of atmospheric requirements and carbohydrate utilization?

They are aerobic microorganisms that are non-fermentative, meaning they cannot ferment carbohydrates anaerobically and instead utilize sugars oxidatively (producing tiny amounts of acid) or are asaccharolytic.

What are the microscopic and structural characteristics of non-fermentative gram-negative bacilli?

They are aerobic, non-spore-forming, straight, slender gram-negative bacilli or thin coccobacilli.

What slant and butt reaction is characteristically produced by non-fermentative gram-negative bacilli on TSIA or KIA?

$K/K$ (alkaline slant / alkaline butt, with no acid production) because they are incapable of fermenting carbohydrates anaerobically.

What is the general cytochrome oxidase reaction of most non-fermentative gram-negative bacilli?

Most are oxidase-positive, in contrast to members of Enterobacteriaceae which are typically oxidase-negative.

Which common hospital chemical disinfectants and antiseptics are non-fermentative gram-negative bacilli notably able to withstand?

Chlorhexidine and quaternary ammonium compounds.

What are the three common primary screening tests used to classify non-fermentative gram-negative bacilli?

1. Growth on MacConkey (MAC) Agar
2. Oxidase reaction
3. Glucose Oxidative-Fermentative (O-F) test.

Which advanced methods are preferred in reference laboratories for the accurate identification of non-fermenting gram-negative bacilli?

Molecular techniques such as nucleic acid sequencing or mass spectrometry.

What are the peptone and carbohydrate concentrations in Hugh and Leifson Oxidative-Fermentative (OF) medium?

Low peptone ($0.2\%$\text{) and }$1\%$\text{ carbohydrate (CHO).}

What substances can be used to create an oxygen barrier overlay in the Oxidative-Fermentative (OF) test?

Mineral oil, petrolatum, or vaspar.

Which pH indicators are utilized in Hugh and Leifson Oxidative-Fermentative (OF) media?

Andrade's acid fuchsin, bromcresol purple, bromthymol blue, or phenol red.

What are the general motility and oxygen requirements of the genus Pseudomonas?

They are strictly aerobic, motile bacilli possessing flagella (often polar or monotrichous).

Which bacterial species are included within the Pseudomonas Fluorescent Group?

Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas putida, Pseudomonas veronii, Pseudomonas mosselii, and Pseudomonas monteilii.

What flagellar arrangement and incubation temperature tolerance are characteristic of Pseudomonas aeruginosa?

It is motile with a monotrichous flagellum and exhibits growth at $42^\circ\text{C}$.

What is the primary hospital-acquired infection associated with Pseudomonas aeruginosa?

It is the leading cause of nosocomial respiratory tract (RT) infections.

What substance is responsible for the mucoid colonies of Pseudomonas aeruginosa characteristically recovered from cystic fibrosis patients?

Alginate (a polysaccharide polymer).

What is the mode of action of Exotoxin A produced by Pseudomonas aeruginosa?

It blocks protein synthesis and causes tissue necrosis.

Which two distinct hemolysins are produced by Pseudomonas aeruginosa as virulence factors?

Heat-labile phospholipase C and heat-stable glycolipid.

Which three classic skin and external ear conditions are caused by Pseudomonas aeruginosa?

Ecthyma Gangrenosum, Swimmer's Ear (otitis externa), and Jacuzzi or Hot Tub Syndrome (necrotizing skin rash).

Which specific patient population is particularly predisposed to severe eye infections caused by Pseudomonas aeruginosa?

Contact lens wearers.

What are the physical and optical properties of the pyoverdin (fluorescein) pigment produced by Pseudomonas aeruginosa?

It is a water-soluble yellow-green or yellow-brown pigment that fluoresces under short-wavelength ultraviolet (UV) light.

What are the solubility characteristics of pyocyanin, and which organism produces it?

It is a blue, water-soluble, chloroform-extractable pigment produced exclusively by Pseudomonas aeruginosa.

What combination of pigments produces the characteristic blue-green or green colony color of Pseudomonas aeruginosa?

Pyocyanin (blue) combined with pyoverdin (yellow-green).

What water-soluble pigments, besides pyoverdin and pyocyanin, can be produced by Pseudomonas aeruginosa?

Pyorubin (red) and pyomelanin (brown or black).

What chemical compound causes the characteristic fruity, grapelike, or corn-tortilla odor of Pseudomonas aeruginosa?

2-aminoacetophenone.

What active detergent is incorporated into Pseudosel Agar to selectively isolate Pseudomonas aeruginosa and enhance pigment production?

Cetrimide (cetyltrimethylammonium bromide).

Which specialized culture media are used to enhance fluorescent pigment production by Pseudomonas species?

Pseudomonas F Agar, GNF Agar, and Flo Agar.

What are the reactions of Pseudomonas aeruginosa in TSI agar and glucose OF medium?

TSI: $K/K$ with a metallic sheen on the slant surface; OF Media: Open tube positive (acidic, color change) and Closed tube negative (no color change).

What are the arginine dihydrolase (ADH) and lysine decarboxylase (LDC) reactions of Pseudomonas aeruginosa?

Arginine dihydrolase (ADH) positive and lysine decarboxylation negative.

To which classes of antibiotics is Pseudomonas aeruginosa inherently resistant?

Penicillin, ampicillin, first- and second-generation cephalosporins, trimethoprim-sulfamethoxazole (SXT), chloramphenicol, and tetracyclines.

Which antimicrobial classes or agents are typically active against susceptible isolates of Pseudomonas aeruginosa?

Aminoglycosides, semisynthetic penicillins (piperacillin and ticarcillin), third- and fourth-generation cephalosporins (ceftazidime and cefepime), carbapenems (except ertapenem), and fluoroquinolones.

At what low temperature are Pseudomonas fluorescens and Pseudomonas putida capable of growing, distinguishing them from Pseudomonas aeruginosa?

$4^\circ\text{C}$.

How do Pseudomonas fluorescens and Pseudomonas putida differ from Pseudomonas aeruginosa in terms of pigment production?

They produce pyoverdin, but they do not produce pyocyanin.

Which biochemical test differentiates Pseudomonas fluorescens from Pseudomonas putida?

Gelatin hydrolysis: Pseudomonas fluorescens is positive (+), whereas Pseudomonas putida is negative (-).

What clinical condition is specifically associated with Pseudomonas putida, especially in cancer patients?

Catheter-related sepsis.

What severe clinical event has been associated with contamination of blood products by Pseudomonas fluorescens?

Transfusion-associated septicemia (as well as pseudobacteremia).

What are the defining characteristics and clinical association of Pseudomonas mosselii?

First identified in $2002$, it is nonpigmented, nonhemolytic, oxidase (+), catalase (+), ADH (+), grows optimally at $30^\circ\text{C}$, and is associated with prostheses infections (such as prosthetic heart valve endocarditis).

Which non-fluorescent Pseudomonas species produces the wrinkled, leathery, adherent colonies shown on sheep blood agar?

Pseudomonas stutzeri.

What are the starch hydrolysis and arginine dihydrolase (ADH) reactions of Pseudomonas stutzeri?

Starch hydrolysis positive (+) and ADH negative (-).

What are the colony characteristics, motility, and flagellar arrangement of Pseudomonas mendocina?

Nonwrinkled, flat colonies with a smooth buttery appearance and yellowish-brown pigment (no pyoverdin); motile by a single polar flagellum.

How can Pseudomonas pseudoalcaligenes be biochemically differentiated from Pseudomonas alcaligenes?

Pseudomonas pseudoalcaligenes is ADH positive (+) and a weak fructose fermenter, whereas Pseudomonas alcaligenes is negative.

Where is Pseudomonas oryzihabitans naturally encountered, and what unusual animal encounter has it been associated with?

Found in Japanese rice paddies and known to cause infections following octopus bites.

What colony morphology and intracellular pigment are produced by Pseudomonas luteola and Pseudomonas oryzihabitans at 48 hours?

Wrinkled or rough colonies that produce an intracellular, nondiffusible yellow pigment.

Which strictly aerobic, nonmotile, diplococcoid gram-negative coccobacillus is shown in the gram stain smear?

Acinetobacter baumannii.

Which organism produces the purplish colonies shown on MacConkey agar?

Acinetobacter baumannii.

How are Acinetobacter baumannii, Acinetobacter lwoffii, and Acinetobacter haemolyticus differentiated by glucose oxidation and hemolysis?

A. baumannii: glucose-oxidizing (saccharolytic) and nonhemolytic; A. lwoffii: non-glucose oxidizing (asaccharolytic) and nonhemolytic; A. haemolyticus: non-glucose oxidizing (asaccharolytic) and hemolytic.

What are the oxidase, catalase, and nitrate reduction reactions of the genus Acinetobacter?

Oxidase negative (-), catalase positive (+), and nitrate reduction negative (-).

Which antibiotics are typically used to treat carbapenem-resistant Acinetobacter baumannii (CRAB)?

Colistin or tigecycline.

What maximum temperature incubation allows the growth of Acinetobacter baumannii?

$42^\circ\text{C}$.

What does the species name maltophilia mean, and what carbohydrate does Stenotrophomonas maltophilia utilize?

From Greek 'malthum' (malt) and 'philia' (affinity); it produces acid from maltose, not glucose.

What colony coloration, odor, and MacConkey agar appearance are characteristic of Stenotrophomonas maltophilia?

On BAP: lavender-green to light purple pigment with an ammonia-like odor; on MAC: blue colonies.

What is the biochemical profile of Stenotrophomonas maltophilia regarding oxidase, catalase, DNase, esculin hydrolysis, gelatin hydrolysis, and lysine decarboxylase (LDC)?

Oxidase negative (-), catalase positive (+), DNase positive (+), esculin hydrolysis positive (+), gelatin hydrolysis positive (+), and LDC positive (+).

What is the antimicrobial drug of choice for treating infections caused by Stenotrophomonas maltophilia?

Trimethoprim-sulfamethoxazole (SXT).

Which species within the genus Burkholderia is non-motile, serving as the exception to the motile genus?

Burkholderia mallei.

In which immunocompromised patient populations is Burkholderia cepacia notably associated with severe pulmonary disease?

Patients with cystic fibrosis (CF) or chronic granulomatous disease (CGD).

Which organism is shown growing on OFPBL agar (yellow, left) and PC agar (white with pink-red halo, right)?

Burkholderia cepacia.

What are the oxidase, LDC, ONPG, and carbohydrate utilization reactions of Burkholderia cepacia?

Weakly oxidase positive (+), LDC positive (+), ONPG positive (+), and oxidizes glucose, maltose, lactose, and mannitol.

What zoonotic respiratory disease is caused by Burkholderia mallei, and which animals are primary hosts?

Glanders (Farcy Disease), affecting livestock such as horses, mules, and donkeys.

What is the Straus test used in the diagnosis of Glanders?

Intraperitoneal inoculation of a male guinea pig resulting in severe orchitis within $2\text{ to }3\text{ days}$.

What disease is caused by Burkholderia pseudomallei, and what is its latent form historically called?

Melioidosis (Whitmore's disease), also known as the 'Vietnamese Timebomb'.

What microscopic staining characteristic and colony odors are exhibited by Burkholderia pseudomallei?

Demonstrates bipolar staining; exhibits an earthy, putrid odor followed by an aromatic, pungent odor.

What is the appearance of Burkholderia pseudomallei colonies on selective Ashdown medium containing colistin?

Deep pink colonies due to the absorption of neutral red.

What pigment, motility, and biochemical traits characterize Burkholderia gladioli?

Produces yellow pigment after $48\text{ to }72\text{ hours}$, motile by $1\text{ or }2$ polar flagella, catalase and urease positive (+), oxidase negative (-), and decarboxylase negative (-).

What are the general motility, oxidase, carbohydrate utilization, and penicillin susceptibility traits of the genus Moraxella?

Nonmotile, oxidase-positive (+), asaccharolytic, strictly aerobic, and usually susceptible to penicillin.

Which Moraxella species is the second most commonly isolated member of the genus and fails to grow on MacConkey agar?

Moraxella nonliquefaciens.

What anatomical site is Moraxella osloensis normally found in, and what pathogen is it often mistaken for?

Normal biota of the genitourinary tract (GUT); often mistaken for Neisseria gonorrhoeae (differentiated by Cystine Trypticase Agar Glucose medium).

What is the alternative name, clinical manifestation, and sheep blood agar effect of Moraxella lacunata?

Morax-Axenfeld bacillus (Haemophilus duplex); causes blepharoconjunctivitis (angular conjunctivitis); pits or pits/spits the agar on BAP.

What are the morphological, biochemical (PDA), and growth characteristics of the genus Oligella?

Small, paired gram-negative coccoid bacilli isolated from the urinary tract; phenylalanine deaminase (PDA) positive (+), oxidase positive (+), nitrate/nitrite positive (+) with gas, with no growth on MacConkey agar.

How can Oligella urethralis be differentiated from Oligella ureolytica?

Oligella urethralis is nonmotile and urease negative (-); Oligella ureolytica is motile (peritrichous flagella) and urease positive (+).

What is the optimal growth temperature and distinct odor of Psychrobacter immobilis?

Optimal growth occurs at $20^\circ\text{C}$ (grows between $5\text{--}25^\circ\text{C}$, rarely at $35^\circ\text{C}$) and produces an odor of roses resembling phenylethyl alcohol.

What clinical specimens yield Psychrobacter phenylpyruvicus, and what are its key biochemical reactions?

Isolated from urine, blood, CSF, and the genitourinary tract; urease positive (+) and phenylalanine deaminase (PDA) positive (+).

What colony edge, odor, and carbohydrate reactivity characterize Alcaligenes faecalis?

Feather-edged, nonpigmented, ahemolytic colonies on BAP with a fruity odor of apples or strawberries; asaccharolytic, producing alkaline reactions in carbohydrate media.

Which asaccharolytic Achromobacter species cause ear infections in diabetic patients?

Achromobacter piechaudii and Achromobacter denitrificans.

Which Achromobacter species is saccharolytic, produces acid from glucose and xylose, and frequently colonizes cystic fibrosis patients?

Achromobacter xylosoxidans.

Which opportunistic pathogen produces the dark violet colonies shown on DNase agar?

Chromobacterium violaceum (producing the ethanol-soluble, water-insoluble pigment violacein).

What are the general motility and indole characteristics of the family Flavobacteriaceae?

They are generally nonmotile (except Balneatrix alpaca, which has polar flagella) and indole positive (+) (except Myroides and Sphingobacterium).

Which neonatal pathogen is shown producing yellow pigment on sheep blood agar while failing to grow on MacConkey agar?

Elizabethkingia meningoseptica.

What are the microscopic morphology, pigment, and SBA appearance of Elizabethkingia meningoseptica?

Long thin bacilli with bulbous ends; produces a yellow pigment (flavin) surrounded by lavender-green discoloration due to proteolytic enzymes.

What clinical condition is specifically associated with Empedobacter brevis?

Endophthalmitis following cataract surgery.

What animal exposures are linked to Bergeyella zoohelicum, and what colony characteristic does it exhibit on rabbit blood agar?

Associated with dog and cat bite wounds (causing cellulitis, tenosynovitis, etc.); produces sticky colonies on rabbit blood agar.

What unique lipid component is present in the cell wall of the genus Sphingobacterium?

Sphingophospholipids.

How is Sphingobacterium spiritivorum differentiated from Sphingobacterium multivorum?

Sphingobacterium spiritivorum produces acid from mannitol, ethanol, and rhamnose.

What carbon source, pigment, and growth rate are characteristic of Methylobacterium species?

Can utilize methanol as a sole carbon source; produces pink to coral colonies; slow growers requiring $4\text{ to }5\text{ days}$ to reach $1\,\text{mm}$.

Which organism produces the pink, mucoid, runny colonies shown on sheep blood agar and is capable of growing on MacConkey agar?

Roseomonas mucosa.

How can Roseomonas mucosa be differentiated from Methylobacterium regarding growth on MacConkey agar and methanol oxidation?

Roseomonas mucosa grows on MacConkey agar and cannot oxidize methanol, whereas Methylobacterium oxidizes methanol and does not grow on MacConkey agar.

What unique TSIA reaction and SBA appearance are characteristic of Shewanella species?

$H_2S$\text{ production positive (+)} on TSIA and mucoid colonies with greenish discoloration on sheep blood agar.

How can Shewanella putrefaciens be differentiated from Shewanella algae?

Shewanella putrefaciens produces a tan to brown pigment, is non-halophilic, and is saccharolytic; Shewanella algae is halophilic and asaccharolytic.

What flagellar motility and growth rate characterize Ralstonia pickettii?

Slow grower requiring $>72\text{ hours}$ and motile by a single polar flagellum.

At what temperatures is Sphingomonas paucimobilis motile, and does it grow on MacConkey agar?

Motile at $18^\circ\text{C}\text{ to }22^\circ\text{C}$, nonmotile at $37^\circ\text{C}$, and does not grow on MacConkey agar.

What ophthalmic infection in soft contact lens wearers is caused by Delftia acidovorans?

Keratitis.

What notable resistance enzyme is carried by Brevundimonas diminuta?

VIM-2 metallo-$\beta$-lactamase.