A Brief Review on the Principles of Human Cadaver Preservation and Monitoring of Microbial Degradation

Putrefaction and decay of preserved cadaver and body parts is one of the major issues that the faculties of medicines in various third world countries are facing. In this study we focus on the meaning of body preservation, causes of putrefaction and we highlight our personal experiences at the Faculty of Medicine in Prince Sattam bin Abdulaziz University in KSA, in preserving the body cadavers. We studied different physical and chemical methods of preservation of cadavers and body parts at the faculty and their efficiency in preventing bacteria and fungi that cause putrefaction and decay.


Meaning of preservation
It's the art and science of human body to treat it with chemical components for preservation by preventing or intercepting microorganisms such as bacteria and fungi which are classified as main causes of organic decomposition which lead to putrefaction [1].
Embalming is an ancient art established by old Egyptians [2]. It is worth being mentioned here that, this is used in many purposes such as transportation of dead body from place to another, as religious practice in some countries etc.
In this study we will focus on Embalming for anatomy education. Most of faculties of medicine around the world use the body cadaver for teaching anatomy for medical student and for research, and this type of preservation is called (anatomical preservation) [3].

Natural Preservation
This type of preservation occurs by natural factors including freezing and dryness that may occur by dry-heat or dry-cold ( Figure 1) and the soil nature [4]. The body or body parts preserved by this can be called the naturally mummified one.

Mummification
It can be divided according to the causative agents which cause preservation of dead body. They are: A) Natural mummification: This is caused by the Mother Nature which occurs when buried in [5] and climate conditions. B) Artificial mummification or true mummification: This is the type of preservation that had been done by Ancient Egyptian civilization for religious concepts ( Figure 2) [6]. According to Greek historian Herodotus there are three types of artificial mummifications and all of them share the same target of interception of decomposition of the dead body [7]. Different materials had been used in the mummification include materials that desiccate and dehydrate such as natron salt and vegetable materials and those act as anti-bacterial factors such as Mastic, Lichen, Myrrh, Bitumen, Cassia, Onions, Beeswax, Lichen, Coniferous resin, Henna and Gum Arabic [5].

Plastination
This is a method or technique used for the long term preservation of body or part of body [8]. This technique was established by German scientist Gunther von Hagens in 1977 [9] in laboratory of Heidelberg University [10]. The main advantage of this way of preservation that the specimens were dry, durable, odorless, handleable and storable manner [11]. In the process of plastination the fluids and lipids in biological tissues substitute by curable polymers commonly epoxy, silicone and polyester. As a result of this procedure the specimen gets harden and a natural look [9] and the decomposition which lead to putrefaction of biological tissues is intercepted.
As previously described many chemicals can be used to replace the fluid and fat this led to provide different techniques of plastination here we will mention some of this techniques.

a) Silicone plastination
Silicone plastination is one of most common techniques of plastination which can be used for body, organs, part of organ and slices [8] ( Figure 3). The Plastination techniques depend on vacuum of original body or tissue fluid and replace it by special curable polymer of the standard silicone S-10 [9]. The fixative chemical mostly use is formaldehyde. This technique was invented by Gunther von Hagens [12].
Silicone plastination consist of four steps after preparation of specimen and are dehydration, defatting, hardening and formaldehyde embalming or fixation ( Figure 3, Figure 4).

b) Epoxy plastination
This techniques of plastination is usually used for tissue examination especially slices of 2 -4 mm [13]. The techniques of preservation are similar to previous one and it substitutes of all water and most of lipid with curable resin [14].
The result of epoxy plastination is durable sectional slices looking like magnetic resonance Image and computed tomography so it suitable for studying anatomy at gross or macroscopic to the microscopic level ( Figure 5). Forensic Medicine and Anatomy Research      • acetone • methylene chloride (if necessary) • polyester resin.

Embalming
The term of Embalming derived from Latin origin and it define as treatment of body cadavers with special chemicals so as prevent decay or putrefaction, it was an ancient culture and nowadays in modern culture it become substantial science and art due to social and science reason because the preserved body cadaver considered as an ideal teaching tool for anatomy and other branches medical science such as surgery, obstetrics, pathology and radiology [4] [20].

a) Embalming in the ancient cultures
Many ancient cultures including Egyptian culture practiced embalming as they believed that decayed dead of the body would preclude it from life after death [21]. The basic steps of ancient embalming are: 1) Washing surface and body cavity with palm wine.
2) Removal of brain and internal organs (viscera) and keep it in jars except the heart.
3) Left the internal organ to dry. As the relevance of body cadavers in anatomical studies cannot be ruled out, the embalming for preservation became more important. The process of embalming consists of four steps can be summarized as the following: • Arterial embalming: it is the injection of embalming fluid through the blood vessels usually the common carotid artery. This is to replace the body fluid by embalming solution. • Cavity embalming: this refers to substitute gas and fluid in the organ and inner side of the body with embalming fluid using a trocar.
• Hypodermic embalming: this is a complementary step to ensure that concentrated embalming fluid reach all parts of the body, especially to those sites of body where the arterial fluids might not reached. This is done by using hypodermic needle and is a case-by-case basis step.
• Surface embalming and washing: this is a (as needed step) remedy or treatment in damaged area in the surface which may occur due to a lot of causes such as skin diseases, cancer, decomposition or other epidermal injury.
Erich Brenner [4] in his great review article mention and compare between different types of modern anatomical embalming techniques in term of long-term storage, advantages and disadvantages and Possibilities of usage in anatomical teaching (Table 1).

Embalming Chemicals
The chemical components of embalming fluid used in modern embalming are variety which includes sterilization and disinfectant agents, preservatives, modifying agents (buffers, anticoagulants, and wetting agents) and dyes [4].

Meaning of Body Putrefaction
The biodegradation is the breakdown of complex organic materials into simpler chemicals by biochemical process [22]. Actually, the oxidative breakdown of synthetic or natural substances is taken place by microbial activity [23]. Biodegradation of body is the final process of the biological destruction of body and is commonly termed as decomposition or putrefaction [24].
The putrefaction is the destruction of the soft tissues of the body and is it done by two different groups of organisms, i.e., the scavengers and the true decomposers like (bacteria fungi protozoa) [25], and both of them are complimentary to each other in function.
After the death of the human being, foul odour from the decomposing body attracts the houseflies and blow flies [27], and usually these flies arrive the dead body within 2 -4 hours and put their egg in natural orifice or damaged skin [27].   softening the skin and make the way easy into interior of the body [28].
The bacteria are the principal agents which ultimately bring about the final reduction of the biological refuse [29].
Systemic study of the cadaveric bacteriology was undertaken by Burn [30] and he found two groups of bacteria on cadavers. The first group includes anaerobic spore-bearing bacilli (e.g. CI. Welhii), coliforms, micrococci, diptheroids and proteus bacteria which are normally present in the respiratory or. Intestinal tracts and they penetrate the mucosa and rapidly invade the tissue shortly after death. The second group of bacteria includes variety pathogenic and non-pathogenic strains [31]. The marked increase in hydrogen ion concentration and the rapid loss of oxygen in the tissue after death favours the growth of anaerobic organisms. The blood is the most natural nutrient medium for microbial growth [30].
The first visible sign of putrefaction is a greenish discoloration of the skin due to the formation of sulfhaemoglobin in settled blood. The process progresses into distension of tissues due to the formation of various gases (hydrogen sulfide, carbon dioxide, methane, ammonia, sulfur dioxide and hydrogen), especially in the bowels [32]. During putrefaction a number of gases are formed in the tissues e.g. hydrogen sulphide, marsh, methane, carbon-dioxide, ammonia and hydrogen phosphide [33] [34].
There are other factors which affect the putrefaction like the weather. Putrefaction is increased in warm rather than in cold [35].
Some studies [36]  The evaluation of preservation factors in department of anatomy in Faculty of Medicine in Salman Bin Abdulaziz University will take place as the following:

Evaluation of Physical Characteristics of Body Cadavers after Embalming
The assessment of physical characteristics according to Benkhadra [39] depends on the softness and flexibility of body cadaver, and actually we get a positive result because the body cadavers maintained its softness and flexibility, that may be explained by the large amount of muscles proteins fragmentation [39]. The second part of the evaluation depends on the biomechanical testing which can be considered as acceptable in our case, taking the fact in consideration that keeping cadaver in formalin will cause a 50% stenography in energy absorption and raise the rate of bone crispness [40] and also the mechanical integrity will decrease after embalming due to bone demineralization [41].

Sampling for Microbes
a) Sampling from cadaver for possible bacterial and fungal population The samples were collected using standard swabbing procedures from different body parts of the 1) cadaver stored in 10% formalin, 2) cadaver stored in refrigerator at (0˚C -1˚C), and 3) plastinated body parts stored at room temperature.
The swabs were taken from oral cavities, nasal cavities, upper limbs, abdomen,   Agar plates were incubated at room temperature for 7 days.

Identification of the Bacteria/Fungi
Bacterial isolates were subjected to various morphological and biochemical characterization tests to determine the identity of the bacterial population using standard method [42].

Results and Discussion
Neither Nutrient Agar plates nor Muller Hinton Agar plates incubated with samples from different sites of plastination, refrigerated and preserved in forma-Forensic Medicine and Anatomy Research