A SHORT NOTE ON Gardnerella vaginalis

 

MORGANELLA            

                                                                       

Compiled by: Zenisha Acharya 

                       Rashmi Shrestha

Central Department of Microbiology

Tribhuvan University

Kirtipur, Kathamndu

 History

•       Morganella morganii is named after Morgan (1906) who isolated it from the feces of infants with diarrhea.

•       Rauss (1936) suggested it was closely related to Proteus because, it produces indole, degraded urea, and exhibited spreading growth on media with reduced agar concentrations at 20-28˚C .

•       The observation by Henriksen and Closs (1938) that both Proteus and Morgan’s bacillus degraded phenylalanine to phenyl pyruvic acid gave additional support to the suggestion and for many years the organism was known as Proteus morganii.

•       The proposal of Kauffmann (1956) that it should be placed in a separate genus, Morganella did not at first receive general acceptance, but the evidence in its favor is now overwhelming: the G+C content of the DNA of Morganella is considerably higher than that of Proteus.

•       DNA-DNA hybridization studies show less than 20 percent genetic homology between the two genera and other members of the Proteae (Brenner et al. 1978); there are differences in the properties of enzymes common to Morganella and other members of the tribe.

Classification

•       Domain: Bacteria

•       Phylum: Proteobacteria

•       Class:  Gammaproteobacteria

•       Order:  Enterobacteriales

•       Family: Enterobacteriaceae

•       Tribe:  Proteae

•       Genus: Morganella

•       Species:  M. morganii

•       The genus has one species M. morganii with two subspecies based largely on the ability of strains to form lysine or ornithine decarboxylase or both or neither. 

Ø  Morganella morganii subspecies  morganii

      trehalose non-fermenter

      Biogroups: A,B,C ,D

Ø  Morganella morganii subspecies sibonii

      trehalose fermenter

      Biogroups : E,F,G

 

Habitat

•       M. morganii is commonly found in the environment and in the intestinal tracts of humans, mammals, and reptiles as normal flora. 

•       Although M. morganii has a wide distribution, it is considered an uncommon cause of community-acquired infection and it is most often encountered in postoperative and other nosocomial infections such as urinary tract infections.

Epidemiology

•       Morganella species are infrequent causes of disease in healthy individuals. M. morganii was originally thought to be a cause of summer diarrhea. The organism has been isolated along with Proteus mirabilis more frequently in patients with diarrhea than in healthy controls . 

•       M. morganii  is found in the environment and in the intestinal tracts of humans, mammals, and reptiles as part of the normal flora.Therefore, most M. morganii bacteremia cases were opportunistic community-acquired infections.

Morphology

•       These are straight, non-spore forming , non-capsulated gram negative rods measuring  0.6-0.7 µm in diameter and 1.0-1.7 µm in length.

•       They are motile by means of peritrichous flagella, but some strains do not form flagella above 30˚C.

•       After 48 hrs on 1% agar media at 22˚C growth may spread to form a surface film. 

•       Swarming does not occur.

•       G +C content of the DNA is 50 mol%.

Cultural characteristics

•       They are facultative anaerobe require both niacin and   pantothenic acid for growth.

•       They grow readily on most culture media as convex colonies 2-3 mm in diameter after overnight incubation at 37˚C.

Ø  Nutrient broth

•       Cultures have an unpleasant smell

Ø  Blood agar                                                        

Approximately 30 percent of strains are hemolytic on blood agar through the production of a calcium dependent hemolysin

Ø  Selective media: Mac Conkey

•       They form colorless colonies on Mac Conkey, eosin-methylene blue, xylose-lysine-deoxycholate, and Salmonella-Shigella agars.

Biochemical characteristics

•       Oxidase:          negative

•       Catalase:         positive

•       Urease:              positive

•       Indole:   positive

•       Methyl Red:  positive

•       Voges Proskauer: positive

•       Citrate:            negative

•       H 2 S:  negative

•       Phenylalanine deaminase:   positive

•       Ornithine-decarboxylase:         positive

•       Ferment glucose and mannose only

•       Gelatin not liquefied

Virulence factors

Ø  Hemolysin:

•       It is calcium-dependent hemolysin

•       It is serologically and functionally identical to E. coli hemolysin  HlyA

Ø  MR/K hemagglutinin:

•       that enhances adherence to urinary catheters

Ø  Urease:

•       High affinity for urea and the potential to cause alkalinization of urine and stone formation, this rarely happens in vivo in man

•       Bifunctional urease which is activated at acid pH .

•       The  role of the urease to promote colonization of the intestinal tract by protecting the organism against the acidity of the stomach

Virulence factors of M. morganii

•       Category Genes

•       Fimbrial adhesins Three MR/P(mannose-resistant/Proteus-like fimbria) operons, 13 mrpJ paralogous, one fimbrial chaperone, two

•       UCA(uroepithelial cell adhesin) operons, one PMF(P. mirabilis fimbria) operon, and two other operons; six putative type IV pili

•       genes hofCB and ppdABCD; two putative trimeric auto transporter secretion genes MM2011 and MM2042

•       Motility/flagellum-related cheA, cheW, cheD, tap, cheR, cheB, cheY, cheZ, umoABCD, rssBA, rcsBCD

•       T3SS Type III secretion system needle complex (20 genes), and effectors, ipaCBD operon

•       Iron acquisition system hmuSTUV, afuABC, feoAB, ireA, btuCD, btuB, and yfeDCBA, 18 other related genes (fecR, ABC transporters, TonB-dep. receptors)

•       IgA protease zapABCD

•       Toxin hmpBA, tccB, tccA, tcdB2, xptA1, xptC1, tcdA4, tcaC, tccB3, and tcaC

•       rtxA, xaxAB, intimin/invasion, HlyD toxin secretion, toxin transporter

•       Two-component systems 19 potential TCSs were identified. qseBC, yedWV, BarA/UhpA, phoP/phoQ.

•       LPS and the cell capsule wzzE, rffC, rffA, wzxE, pagP, arnT, msbA, lpxK, kdsB, kdsC, fepE/wzz, htrB/waaM, rfaD/waaD, rfaF/waaF, rfaC/waaC, wabH, wabG,

•       waaQ/rfaQ, waaA, waaE, coaD, rfaL, hldE/rfaE, lpxD, lpxA, lpxB, msbB, kdsA, rfaB, lpxH, pgi, galU, lpxC, gale, wecA, rffE, wecC, rffG, rffH,

•       rffT, wzyE, rffMrcsB, rcsC, rcsD and rcsF.

•       Ureases ureABCEFGD

Clinical manifestation

Ø  Diarhhoea:

They are normal faecal flora that often causes infection in patients whose normal flora have been disturbed by antibiotic therapy.

Ø  UTI:

Urinary tract infection is the most common clinical infection site. Most often these occur in elderly patients in nursing homes with long-term indwelling catheters. Morganella is the fifth leading cause of UTIs in nursing home patients.

•       skin and soft tissue infections

•       intra-abdominal infections

•       biliary infection, liver abscess and peritonitis

•       bacteremia

•       diabetic foot infections

•       septic arthritis

•       meningitis

•       otitis media

•       gastroenteritis

•       neonatal sepsis

•       Pericarditis

•       Chorioaminonitis 

•       Histamine food poisoning

Laboratory diagnosis

Ø  Specimen:

      According to site of infection

•       Faeces

•       Urine

•       Wound swab

•       ear swab

•       blood                                                        

Direct microscopy:                                                                    

Ø  These are straight

Ø  gram negative rods

Ø  measuring  0.6-0.7 µm in diameter and 1.0-1.7 µm in length

Culture:

•       They grow readily on most culture media as convex colonies 2-3 mm in diameter after overnight incubation at 37˚C.

Ø  Nutrient broth:

•       cultures have an unpleasant smell

Ø  Blood agar

Approximately 30 percent of strains are hemolytic on blood agar through the production of a calcium dependent hemolysin

They form colorless colonies on Mac Conkey, eosin-methylene blue, xylose-lysine-deoxycholate, and Salmonella-Shigella agars

Ø  Biochemical tests:

Ø  Oxidase:          negative

Ø  Catalase:         positive

Ø  Urease:            positive

Ø  Indole: positive

Ø  Methyl Red: positive

Ø  Voges Proskauer:        positive

Ø  Citrate:            negative

Ø  H 2 S:  negative

Ø  Phenylalanine deaminase: positive

Ø  Ornithine-decarboxylase:       positive

Ø  Ferment glucose and mannose only

Ø  Gelatin not liquefied        

Tests	Proteus	Morganella	Providencia
Swarming	+ve	-ve	-ve
Urea hydrolysis	+ve	+ve	v
Citrate utilization test	v	-ve	+ve
Gelatin liquefication	+ve	-ve	-ve
Ornithine decarboxylase test	v	+ve

     Others

Ø  PCR

Ø  Serotyping

Ø  Biotyping

Ø  Phenotyping

 

       Treatment

•       M. morganii strains are usually sensitive to quinolones, such as nalidixic acid and ciprofloxacin, to aminoglycosides such as gentamicin and tobramycin, to trimethoprim, cotrimoxazole, chloramphenicol, and aztreonam, and the carbapenems imipenem and meropenem.

        Prevention

•       Hand washing practices

•       Use of contact isolation for infected or colonized patients.

•       If there are multiple different clones of ESBL producing organisms in a hospital, changes in antibiotic use policy in the hospital may have a role in decreasing the number of these organisms

         References

Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology , 9^th edition Williams & Wilkins, Baltimore, MD.

3. W.W.C Topley, Topley & Wilson's principles of bacteriology, virology and immunity, London 

4. www.hardlink.com /Bacterial Database Search,

5. www.researhgate.com

6. Mackie, T. J., Collee, J. G.McCartney, J. E. (1996). Mackie & McCartney practical medical microbiology. New York ; Churchill Livingstone