Observations on the bacterial flora of the hen's egg, with a description of new species ofProteusandPseudomonascausing rots in eggs

Abstract

1. Examination of several hundred eggs suggests that a high proportion (98%) of the whites of fresh eggs, and a slightly smaller proportion of the yolks (93%), are sterile.2. The shell of the egg is heavily infected with a heterogeneous flora, includingProteusandPseudomonasbacteria capable of producing rotting.3. The rots found in imported New Zealand and Australian eggs, and in English stored eggs, may be grouped into black rot, red rot, green rot, and a miscellaneous group.4. Black rot is brought about chiefly by strains ofProteus, but some species ofPseudomonascause some blackening. Red and green rots are due to infection with particular strains ofPseudomonas.5. A “fishy” odour is developed during the multiplication of certain atypical coliform organisms in the white, and a strong “cabbage-water” smell is often found after the growth ofPseudomonasspecies.6. Washing eggs under clean conditions has no effect on immediate bacterial penetration. Washing removes a protective coating so that if the eggs are subsequently soaked in a bacterial suspension, much more penetration of bacteria occurs than with untreated controls.7. Detailed descriptions of the coliform andProteusorganisms isolated are given. It is shown that the strains ofProteusfrom the eggs here investigated are antigenically not related toP. melanovogenesfound by Miles and Hainan to be the cause of black rot in South African eggs.8. It does not at present seem possible to assign specific names to the organisms isolated. The utilization of carbon sources by the species ofPseudomonasobtained from eggs, and by certain stock strains, and the possibility of a grouping on that basis, is discussed.

The use of total aerobic and Gram-negative flora for quality assurance in the production chain of consumption eggs

“…The average total count of aerobic and Gram-negative bacteria of the 20 eggs analysed within 2 h after sampling deviated respectively less than 0.01 and 0.04 log cfu/eggshell compared to the other 20 eggs of the same batch analysed after 56 h storage in ambient conditions in the laboratory. Also Haines (1938) reported no significant difference in the bacterial flora on the egg between eggs examined immediately and after keeping for 4 days at room temperature.…”

“…One method concerned removal of the egg content and crushing of the shell and shell membranes in a sterile plastic bag with 10 ml quarter-strength Ringer's solution (Ringer Solution, Oxoid, Hampshire, UK) for 2 times 1 min with an interval of 5 min rest in between (Haines, 1938). Another method considered the washing of intact eggs in a sterile plastic bag with 10 ml diluent.…”

“…External eggshell contamination could be important for the shelf life and the food safety of consumption eggs and egg products. It is hypothesized that bacterial contamination of the internal egg content could be the result of the penetration of the shell by bacteria deposited on the surface of the egg after it has been laid (Haines, 1938;Harry, 1963;Schoeni, Glass, Mcdermott, & Wong, 1995). Smith, Rose, Wells, and Pirgozliev (2000) also reported that high excreta moisture can directly increase the microbial contamination of the eggshell and consequently increase the risk of microbial contamination of the internal contents of ostensibly clean eggs.…”

“…Haines (1938) and Board et al (1964) crushed the shell together with membranes in a sterile plastic bag with diluent after removal of the egg content. Gentry and Quarles (1972) and Pienaar, Coetzee, and Bragg (1995) washed the intact eggs in a sterile plastic bag by rubbing.…”

Bacterial contamination of table eggs and the influence of housing systems

“…It is hypothesised that bacterial contamination of the egg content could result from the penetration of the shell by bacteria deposited on the surface of the egg after it has been laid; this is also called the horizontal infection route (Haines, 1938;Harry, 1963;Quarles et al, 1970;Schoeni et al, 1995). Smith et al (2000), Messens et al (2005;2006;2007) and De Reu et al (2006b;2006f) reported that increasing numbers of micro-organisms on the eggshell consequently increase the risk of microbial eggshell penetration and egg content contamination.…”