Prevalence and antibiogram of coagulase negative Staphylococci in bioaerosols from different indoors of a university in India

Abstract

Background: Staphylococci species are the major constituents of infectious bioaerosols, particularly methicillin-resistant Staphylococci (MRS) have serious health impacts. Here, the bacterial burden was quantified, especially prevalence of MRS in bioaerosols collected from indoors of Dr. B.R. Ambedkar Central Library (DBRACL) and Central Laboratory Animal Resources (CLAR) of Jawaharlal Nehru University, New Delhi, India. Air samplings from DBRACL and CLAR were done using the settle plate method and SKC biosampler, respectively.

Results: This study showed a maximum 6757 CFU/m²/hr of bacterial load in the DBRACL reading room, while unacceptable bacterial loads (> 1000 CFU/m³ of air) at different sites of CLAR. Further, at both the sampling sites the predominance of coagulase negative Staphylococci (CNS) was observed. A total 22 and 35 Staphylococci isolates were isolated from DBRACL and CLAR bioaerosols, respectively. Majority (16/22) of the Staphylococcal isolates from DBRACL belonged to human-associated Staphylococci where S. haemolyticus (5/22) was the most dominating species. However, in CLAR facility centre, animal-associated Staphylococci (19/35) were dominating, where S. xylosus (12/35) was the most dominating species. Further, antibiotic sensitivity tests revealed 41% MRS and 73% multidrug resistant (MDR) among airborne Staphylococci from DBRACL indoor bioaerosols. Similarly, in CLAR facility, approximately, 66% Staphylococci isolates were methicillin resistant, out of which 2 isolates showed high MIC value ≥ 16 μg/mL. Further, we confirmed the presence of 49% multidrug resistant Staphylococci in the indoor air of CLAR facility.

Conclusions: This study suggested that the exposure of workers and students in CLAR to such a high concentration of drug-resistant Staphylococci should not be undermined, as these bacterial concentrations are the direct representative of inhalable particulate matter (PM_2.5) as per collection procedure. Simultaneously, passive sampling from DBRACL assessed the risks due to microbial contamination in particle agglomerates, which may deposit on the crucial surfaces such as wounds/ cuts or on the frequently used items.

Keywords: Bioaerosol; CNS; Infectious bioaerosol; Methicillin-resistance; Multi-drug resistance; Staphylococci.

Fig. 1

Bacterial loads in Dr. B.R. Ambedkar Central Library (DBRACL) Bioaerosols at different season: a Total bacterial load (CFU/m²/hr) in different rooms of the DBRACL; b Total bacteria, Gram positive bacteria, Gram negative bacteria and total Staphylococci in pre-monsoon, monsoon and post-monsoon in DBRACL reading room

Fig. 2

Prevalence of airborne (a) bacterial concentration and; (b) staphylococcal concentration (CFU/m³) in the indoor air of University Central Laboratory Animal Resources (CLAR)

Fig. 3

Prevalence of human-associated Staphylococci and animal-associated staphylococci in the University (a) DBRACL and (b) CLAR bioaerosols samples

Fig. 4

Overall sensitivity pattern of Staphylococci isolated from the bioaerosols collected at University DBRACL and CLAR against different classes of antibiotics