Available literature fails to provide reports on the presence and concentration of staphylococci and fecal bacteria in very specific environments, such as animal facilities in the zoos. Another difficulty is concerned with the lack of normative values for staphylococci. When we compare the results against values established for mesophilic bacteria recommend by ZECB – 1x105CFU/m3 (TC) and 5x104CFU/m3 (RF) – the concentrations for TC were not exceeded, while the concentration for RF was exceeded by 24% only once. As regards fecal bacteria, existing normative values were not exceeded. Recorded concentrations, as compared with normative values, amounted to approx. 5% for TC and 10% for RF.
The staphylococci concentrations recorded in the course of the study conducted in the zoo in Chorzów ranged from 0 to 6.9x104CFU/m3. The lowest concentrations were noted in winter, while the highest in spring. Staphylococci count obtained by Masclaux et al. (2013) carrying out research on a pig farm in Switzerland fell within the following range: 1.9x103–4x108CFU/m3. However, in summer the concentration ranged from 1.9x103 to 4.7x107CFU/m3, while in winter it increased by one order of magnitude (5.9x104–4x108CFU/m3). In our study the concentrations for staphylococci were higher by at least three orders of magnitude, as compared with the results obtained by Masclaux et al.
Popescu et al. (2011) conducted research in stables in Romania (Brasov County) to evaluate the changes in staphylococci concentrations depending on the time of the day. The values measured in the evening were slightly higher: 5.91x 104CFU/m3 vs. 5.34x104CFU/m3 in the morning – the difference in mean values amounted to approx. 10%. The concentrations for fecal bacteria were also higher in the evening – in that case the difference for mean concentrations reached 44%. The concentration of fecal bacteria in the morning amounted to 1.54x104 CFU/m3, while in the evening to 2.75x104CFU/m3. In our study the daily mean concentration for fecal bacteria was significantly lower. It amounted to 2.4x101CFU/m3,, what means that it was three orders of magnitude lower. It indicates that zoo keepers maintain proper cleanness standards in rooms intended for animals, what is surely associated with much lower stock as compared with large-scale farms.
The application of an Andersen cascade impactor in the experiments enabled us to estimate the potential level of bioaerosol penetration into the human respiratory system based on the bacteria aerodynamic size (Górny et al. 2016). Madsen et al. (2018) used an Andersen cascade impactor to determine which bioaerosol fraction contains staphylococci based on the aerodynamic size of particles/aggregates formed by these bacteria. According to Madsen 70% of bioaerosol contains staphylococci aggregates sized 7–11µm. It indicates that they are deposited in the upper respiratory tract – 22% of bioaerosol in the primary and secondary bronchi and 8% in the terminal bronchi and alveoli. Our study delivered contradictory results – fraction sized 7–11µm constituted only 11.2%, and the largest number of staphylococci was detected in fraction sized 2.1–1.1µm (27%). It means that this part of bioaerosol reaches terminal bronchioles. A significant part of bioaerosol (77.6%) was qualified as FR.
Clauβ (2015) in a review article addressed the topic of the distribution of bioaerosol fractions for fecal bacteria and staphylococci. The data for fecal bacteria presented in that article are consistent with the results generated in this study. However, the results obtained for staphylococci were varying. In the above-cited article the fraction above 4.7µm constituted more than 50%, while in our study as little as 22.4%.
As seen in various research, bioaerosol particles with the diameter lower than 2.5µm pose the most serious threat to the exposed people. This fraction is capable of penetrating into the lower pulmonary tract (to pulmonary alveoli), what often leads to health problems, such as low birth weight, heart and lung diseases, cancer and premature death [Morakinyo et al. 2016]. As claimed by Clauβ (2015), in the case of rooms intended for animals it may depend on many factors like room area, number of animals, animal size and weight, the presence or absence of litter.
The research conducted previously in the same object (Grzyb and Pawlak 2021) revealed that I/O ratio for bacteria reached maximum value of 344 for TC and 785 for RF. In the case of indicator bacteria, ST-POS in particular, I/O ratio reached the value of 11,029 for TC and 8,979 for RF. It means that the difference between staphylococci concentration indoors and in the outside air was high. Staphylococci intoxication inside facilities for zoo animals can be easily explained, as staphylococci constitute natural fur, skin and mucous membrane microflora. This assumption can be supported by data delivered by Chmiel et al. (2019) who reported instances of bacterial intoxication in churches and museums in Kraków. In that case worshipers and visitors were the source of contamination.
As results from the research carried out by Schulz et al. (2004), staphylococci can be used as a reliable and useful indicator for determining safe distance between rooms intended for animals and residential buildings as well as the spread of bioaerosol in the air surrounding animal shelters.
The most burning issue relating to the antibiotic resistance is concerned with viewing staphylococci as a serious threat to humans and animals. The most frequent reports regarding the risks associated with staphylococci concern Staphylococcus aureus, that can show resistance to methicillin (methicillin-resistant SA – MRSA) or vankomycine (vankomycine-resistant SA – VRSA). The information that majority of its strains are saprophytic and occur on human skin, animal fur as well as mucous membranes of the two is less popular. S. aureus can be found in 20–40% of human population. It colonizes nostrils and does not cause any health problems. However, S. aureus can cause opportunistic infections of the skin and soft tissues as well as inflammation of the entire body (sepsis). The incidence rate for staphylococci in the air samples depends on the sampling spot. Messi et al. (2015) carried out experiments in public places in Italy and reported that staphylococci constituted 17% of all isolated bacteria, while S. aureus strains approx. 1.7%. Our study covered 200 staphylococci strains but S. aureus was not detected.
The studies undertaken by Ferguson et al. (2016) confirmed that disinfecting rooms for animals results in killing staphylococci, including MRSA. Thus, when the concentration of staphylococci is high, it is advised to schedule periodic disinfection of animal rooms as an efficient measure reducing the number of undesired germs. It must be remembered that indicator bacteria analyzed in this study are potentially pathogenic. They migrate by means of direct transmission through dirty hands or orally, and as bioaerosol, what poses threat to animal keepers and – to a lesser degree – to zoo visitors (Bos et al. 2016).
In this study Staphylococcus succinus was the most numerous staphylococci species (approx. 33%), followed by S. sciuri (19.1%) and S. vitulinus (12.6%). Schulz et al. (2004) detected Staphylococcus saprophyticus, S. cohnii, S. arlettae and S. lentus on a broiler farm. Similar results were obtained by Popescu et al. (2011), who conducted research in stables. They identified two staphylococci species with more than 20% share in the entire number of isolated strains: S. sciuri and S. xylosus. Comparable species composition with the highest S. sciuri and S. lentus share was shown in Italian stables by DeMartino et al. (2010). Contradictory results were delivered by Popescu et al. (2011), who established that Staphylococcus epidermidis is the most numerous bacteria species with the share amounting to approx. 25%. In our study it constituted 5% of all identified bacterial species. Haas et al. (2020) investigating pig barns also received conflicting results. The greatest share among all isolated staphylococci species was recorded for S. pasteuri (47.9%), S. cohnii subsp. cohnii (24.5%), while the lowest for S. chromogenes (1.06%).
Antibiotic resistance represents key staphylococci characteristics. It results from activating few mechanisms in the staphylococci cells: enzymatic inactivation of antibiotic, active removal of antibiotic from the cell or changing drug affinity to target site in the bacterial cell (Lenart-Boroń et al. 2016). The results of resistance testing for selected antibiotics presented here are in line with the data released by Wolny-Koładka (2018).