**3. Risk factors of acidifier use**

302 Antimicrobial Agents

experiments. Bacteria are known to develop acid-resistance when exposed to acidic

The beneficial effects of organic acids and their salts on growth performance have been confirmed in several studies. Acidifiers added to pig diets may potentially help improve growth performance (Table 2 & 3) by improving digestive processes through several

a. Improving gut health by promoting the beneficial bacterial growth, while inhibiting growth of pathogenic microbes (through reduction of pH and buffering capacity of diets). A reduced buffering capacity of diets containing organic acids is also expected to slow down the proliferation and/or colonization of undesirable microbes, e.g*. E. coli*, *clostridia* in the gastro-ileal region (jejunum, cecum) (Partanen & Mroz, 1999; Biagi et al*.* 2003). In addition organic acids or their salts could not improve the animal growth performance, but they could indirectly increase cecal pH and cecal ammonia concentrations (Biagi et al. 2007). b. Stimulating - improving pancreatic secretions (Harada et al. 1986), which increase the digestibility, absorption and retention of protein and amino acids (Blank et al 1999, Kemme et al. 1999) and minerals (such as Ca, P, Mg and Zn - particularly Ca and P) (Jongbloed et al. 2000; Valencia, 2002; Omogbenigun et al. 2003) in the diet. Although opposite results have also been reported (Radecki et al. 1988), it is generally considered that dietary organic acids or their salts lower gastric pH, resulting in increased activity

c. Influencing of gut morphology by promoting changes in the digestive function and microbial ecology and fermentation (Piva et al. 2002a; Manzanilla et al. 2004). Some organic acids act positively on microbial growth and ammonia production by pig cecal microflora. Biagi and Piva (2007) noticed that various acids (formic, acetic, propionic, lactic, butyric, sorbic, fumaric, malic, citric, benzoic) can inhibit or enhance cecal bacterial activity and can positively influence pig cecal microflora *in vitro* fermentation reducing ammonia concentrations. It is well known that short-chain fatty acids (acetic, propionic and n-butyric acid) produced by microbial fermentation of carbohydrates stimulate epithelial cell proliferation (Sakata et al. 1995) and the strength of this effect is in the following order: n-butyric>propionic>acetic acid (Sakata, 1987). Increased epithelial cell proliferation has also been observed when short-chain fatty acids are orally given or provided by intravenous or gastrointestinal infusions (Sakata et al. 1995), since dietary organic acids can influence fermentation patterns in the small intestine, and may indirectly influence intestinal morphology. Kirchgessner and Roth (1988) have proposed that organic acids may stimulate intermediary metabolism

The use of some organic acids has been found to reduce the formation of biogenic amines (such as cadaverine and putrescin) that are produced particularly in high protein feeds and in feeds, containing added synthetic amino acids. Biogenic amines have unfavourable effects on growth and feed conversion. The growth stimulation effects of formic, acetic and propionic acids are partly caused by their inhibitory effect on biogenic amines (Eckel et al. 1992). However, a clear mode of action has not been fully described yet and the magnitude and consistency of the response may vary, depending on inclusion rate and other dietary factors.

mechanisms. It is believed that acidifiers can enhance the growth performance by:

environments for some time (Mroz, 2005).

**2.2 Antibacterial activity and growth promoting effects** 

of proteolytic enzymes and gastric retention time.

resulting in improved energy or protein/amino acid utilization.

The use of organic acids in feed appears two main problems:


In order to minimize these effects, the natural buffering capacity of feeds (related to mineral and protein content) should be evaluated to determine the minimum effective amount of acid to use (Best, 2000). Another strategy to extend the effectiveness of acid supplements and reduce corrosion damage to housing materials is the use of a slow-release form of acids. It consists on the use of organic acids with fatty acids and mono- and diglycerides mixed to form microgranules. A study by Cerchiari (2000) showed that use of these granules, as compared to use of free acids, results in greater feed intake and growth.

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#### **4. Conclusion**

Due to consumers' concern about the possibility of drug resistance of pathogenic bacteria, there is an urgent need to search for growth promoters other than antibiotics. Dietary acidifiers can actually become the most common and efficacious alternative solution to antibiotics, in order to improve health status and performance of pigs. The use of organic acids in pig production could be part of a general nutritional strategy focusing on a better gastrointestinal health; the goal is better productivity and better meat quality.

#### **5. References**


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**15** 

**From Synthesis to** 

**Antibacterial Activity of Some** 

*Faculty of Science, University of Kragujevac, Kragujevac,* 

*3Faculty of Agronomy, University of Kragujevac, Čačak,* 

Ivana D. Radojević1, Verica V. Glođović2,

Gordana P. Radić2, Jelena M. Vujić3,

*1Department of Biology and Ecology,* 

*Republic of Serbia* 

**New Palladium(II) and Platinum(IV) Complexes** 

Olgica D. Stefanović1, Ljiljana R. Čomić1 and Srećko R. Trifunović<sup>2</sup>

*2Department of Chemistry, Faculty of Science, University of Kragujevac, Kragujevac,* 

Simultaneously with the rapid development of a wide range of antibacterial agents since the 1940s, bacteria have proved extremely adept at developing resistance to each new employed agent. The rapidly increasing incidence of bacterial resistance to antimicrobial agents has become a serious problem worldwide. Resistance mechanisms have been identified and described for all known antibiotics currently available for clinical use (Fluit et al., 2000).

The synthesis and evaluation of the biological activity of the new metal-based compounds is the field of growing interest. Numerous complexes based on palladium(II) and platina(IV) ion have been synthesized and their different biological activities have been documented (Agarwal, 2007; Mishra et al., 2007a; Mishra & Kaushik, 2007). The impact of different palladium and platinum complexes on the growth and metabolism of various groups of microorganisms has been studied. Garoufis et al. (2009) reviewed numerous scientific papers on anti-viral, antibacterial and antifungal activity of palladium(II) complexes with different types of ligands (sulfur and nitrogen donor ligands, Schiff base ligands and drugs as ligands). There are other papers in the literature showing different intensity of palladium(II) and platina(IV) complexes activity on various species of bacteria and fungi (Kovala-Demertzi et al., 2001; Brudzinska et al., 2004; Coombs et al., 2005; Guerra et al., 2005; Ali et al., 2006; Manav et al., 2006; Aghatabay et al., 2007; Kizilcikli et al., 2007; Mishra et al.,

The aim of this paper is to describe synthesis of some new palladium(II) and platinum(IV) complexes and in vitro research of their antibacterial activities. The second objective is to evaluate the impact these compounds have on probiotic bacteria. Probiotics are used as supplements and they play significant role in protecting and maintaining the balance of

2007b; Biyala et al., 2008; Al-Hazmi et al., 2008; Vieira et al., 2009).

intestinal microflora in antibiotic therapy.

**1. Introduction** 

*Agribiological Research Zeitschrift für Agrarbiologie-Agrikulturchemie-Ökologie,* Vol. 49, No. 4, pp. 307–317, ISSN 0938-0337.

