The effect of the air sampling method on the recovery of Mycoplasma gallisepticum from experimentally produced aerosols

Figures & data

Figure 1. The image depicts the impiger used in the present study for the recovery of M. gallisepticum and E. faecalis from experimentally produced aerosols. Arrows indicate the direction of the airflow through the impinger.

Table 1. Recovery of M. gallisepticum (Mg) and E. faecalis (Ef) strain 6085.94 from experimentally produced aerosols. Aerosol samples were simultaneously taken with gelatine filters (GF) coupled to a MD8 Airscan and by impinger (IMP) connected to a membrane vacuum pump. The aerosol doses and the titres of aerosols were assessed by culture and are expressed as log₁₀ colony forming units per m³ of air.

		Aerosol titre
			t = 0 min^1		Initial loss^2		t = 25 min		Half-life time (min)^3
Exp.	Aerosol fluid	Dose	GF	IMP	GF	IMP	GF	IMP	GF	IMP
1	Mg field strain in PBS^4	7.5	5.1	<5.4^5	2.4	>2.1	4.6	<5.4	15	–^6
2	Mg field strain in PBS + BPW^7	7.5	6.3	<5.4	1.2	>2.1	<4.6^5	<5.4	<4	–
3	Mg field strain in ME broth^8 + BPW	7.5	6.4	6.3	1.1	1.2	5.8	<5.4	13	<8
4	Mg vaccine strain in PBS	8.0	<4.6	<5.4	>3.4	>2.6	<4.6	<5.4	–	–
5	Mg vaccine strain in PBS + BPW	8.1	<4.6	<5.4	>3.5	>2.7	<4.6	<5.4	–	–
6	Ef in PBS + BPW	8.1	7.1	7.1	1.0	1.0	6.4	6.8	11	25
7	Ef in PBS + BPW	8.3	7.4	7.1^9	0.9	1.2^9	6.3	6.5^9	7	13

¹t = 0 min is the end of aerosol generation.

²Difference between log₁₀ dose and log₁₀ aerosol titre at t = 0 min.

³Half-life time is calculated based on titres at t = 0 and t = 25 min.

⁴PBS is phosphate-buffered saline.

⁵Value below detection limit.

⁶Calculation of half-life time is not possible.

⁷BPW is buffered peptone water.

⁸ME broth is Mycoplasma Experience broth.

⁹Impinger used without glass beads.

Table 2. Moisture content of gelatin and cellulose nitrate filters assessed by drying¹ and gravimetrics. Both unused filters and filters through which air had been aspirated were examined.

		Air aspirated through filters
Filter type	n	Yes/no	Volume (l)	Duration (min)	T (°C)	RH (%)	Mean moisture content (% wt/wt) ± SD^2 (range)
Gelatin	10	No	–^3	–	–	–	12.2 ± 1.0 (10.4–13.5)^4
	5	Yes	67	2	20–23	52–62	12.2 ± 1.3 (9.8–12.8)^4
	5	Yes	67	2	24–27	20–26	11.9 ± 0.9 (11.4–13.6)^4
	5	Yes	670	20	24–27	20–26	9.9 ± 1.1 (8.8–11.2)^5
Cellulose nitrate	5	No	–	–	–	–	3.0 ± 0.8 (1.9–3.7)^4
	5	Yes	50	2	20–23	52–62	2.7 ± 0.1 (2.7–2.8)^4

¹Drying was performed in air of 102–104°C during 2 h.

²Standard deviation.

³Irrelevant.

^4,5Values of the same filter type with different superscript differ significantly (P < 0.05).