Cockroaches (Blattodea: Blattidae): A Reservoir of Pathogenic Microbes in Human-Dwelling Localities in Lahore

Abstract

This study focuses on isolation of pathogenic bacteria from external and internal surfaces of cockroaches collected from houses and hospitals in Lahore. In total, 240 adult cockroaches were collected from houses and hospitals by hand or using sticky traps and food-bait traps. Cockroach species were identified, and microbial screening was done for external surfaces and gut tracts of cockroaches. Jaccard's index of similarity, Bray-Curtis' index of dissimilarity, and Shannon-Wiener's diversity index were used to measure the bacterial community diversity (all species of bacteria) in each habitat. Relative abundance and frequency were measured for each bacterial species on external and internal surfaces of cockroaches. Among human habitations, two major species of cockroaches were isolated, i.e., Periplaneta americana (P. americana) and Blattella germanica (B. germanica). Out of 240 cockroaches collected, 167 were P. americana and 73 were B. germanica. In total, 11 bacterial species were isolated, but no different bacterial load in each habitat was observed. The most common diagnostic bacterium isolated from the external surface of cockroaches was found to be Escherichia coli (10.31%). In contrast, the most common isolate from the internal gut tract of cockroaches was found to be Pseudomonas aeruginosa, with relative frequency of 19.96%. Jaccard's index of similarity of bacterial species found on cockroaches was highest (0.3125) in houses, whereas Bray-Curtis' index of dissimilarity was highest for hospitals (0.2174). The highest Shannon-Wiener's diversity index value was found in bacteria on cockroaches collected from the Punjab Institute of Cardiology (2.610632). No Salmonella typhi, Staphylococcus epidermidis, Enterobacter aerogenes, and Streptococcus pneumonia were found in the digestive tract of any cockroach.

Keywords: Blattella germanica; Periplaneta americana; hospital; house; pathogenic bacterium.