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Cockroaches are known as mechanical vectors of some pathogens that can infect humans. The present study aims to rapidly identify Periplaneta americana fungal pathogens from sewer systems of public hospitals in Esfahan using the polymerase chain reaction (PCR) technique. A total of 55 P. americana cockroaches were randomly collected by direct trapping from sewer systems of seven hospitals and screened for fungal infectious agents using standard morphological methods and the PCR sequencing. From the American cockroach, we isolated 62 yeasts and 31 molds from the surface, hemocoel, and digestive tract of P. americana. Based on DNA sequence comparisons and other taxonomic characteristics, they were identified as more than four species of yeast and four species of mold. Yeast species including Pichia kudriavzevii, Candida glabrata, Pichia kluyveri, and Candida viswanathii, and molds such as Aspergillus niger, Penicillium italicum, Mucor plumbeus, and Rhizopus oryzae were isolated repeatedly from the surface, hemocoel, and digestive tract of P. americana. Our results show that the use of a combination of morphological, molecular techniques, and phylogenetic analysis can lead to the identification of pathogenic fungal agents in American cockroaches and also knowledge of fungal pathogens-arthropod host relationships.

Cockroaches are significant pests worldwide, being important in medical, veterinary, and public health fields. Control of cockroaches is difficult because they have robust reproductive ability and high adaptability and are resistant to many insecticides. Wolbachia is an endosymbiont bacterium that infects the reproductive organs of approximately 70% of insect species and has become a promising biological agent for controlling insect pests. However, limited data on the presence or strain typing of Wolbachia in cockroaches are available. PCR amplification and sequencing of the wsp and gltA genes were used to study the presence, prevalence and molecular typing of Wolbachia in two main cockroach species, Blattella germanica (German cockroach) and Periplaneta americana (American cockroach), from different geographical locations of Iran. The Wolbachia endosymbiont was found only in 20.6% of German cockroaches while it was absent in American cockroach samples. Blast search and phylogenetic analysis revealed that the Wolbachia strain found in the German cockroach belongs to Wolbachia supergroup F. Further studies should investigate the symbiotic role of Wolbachia in cockroaches and determine whether lack of Wolbachia infection may increase this insect's ability to tolerate or acquire various pathogens. Results of our study provide a foundation for continued work on interactions between cockroaches, bacterial endosymbionts, and pathogens., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Choubdar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Although it has been difficult to prove the direct involvement of cockroaches (i.e. insects of the order Blattaria) in the transmission of pathogenic agents to humans, such insects often carry microorganisms that are important in nosocomial infections, and their medical importance in the spread of bacteria cannot be ruled out. In houses and institutions with poor standards of hygiene, heavy infestations with cockroaches, such as the peridomestic American cockroach (Periplaneta americana L.) and the domestic German cockroach (Blattella germanica L.), can occur. In the present study, cockroaches (126 B. germanica and 69 P. americana) were collected from four buildings (three public training hospitals and one house) in central Tehran, Iran. Each insect was processed, under sterile conditions, so that the bacteria on its external surfaces and in its alimentary tract and faecal pellets could be isolated and identified. The oldest and largest of the three hospitals sampled (a 1400-bed unit built 80 years ago) appeared to be the one most heavily infested with cockroaches, and cockroaches from this hospital accounted for most (65.4%) of the isolates of medically important bacteria made during the study. No significant difference was found between the percentages of P. americana and B. germanica carrying medically important bacteria (96.8% v. 93.6%; P>0.05). At least 25 different species of medically important bacteria were isolated and identified, and at least 22 were Gramnegative. The genus of enteric bacteria most frequently isolated from both cockroach species, at all four collection sites, was Klebsiella. The cockroaches from each hospital were much more likely to be found contaminated with medically important bacteria than those from the house. The hospital cockroaches were also more likely to be carrying medically important bacteria internally than externally (84.3% v. 64.1%; P<0.05). The implications of these and other recent results, for the control of cockroaches and nosocomial infections, are discussed.

We examined the diversity of a marker gene for homoacetogens in two cockroach gut microbial communities. Formyltetrahydrofolate synthetase (FTHFS or fhs) libraries prepared from a wood-feeding cockroach, Cryptocercus punctulatus, were dominated by sequences that affiliated with termite gut treponemes. No spirochete-like sequences were recovered from the omnivorous roach Periplaneta americana, which was dominated by Firmicutes-like sequences.

Blattabacteria are intracellular endosymbionts of cockroaches and primitive termites that belong to the class Flavobacteria and live only in specialized cells in the abdominal fat body of their hosts. In the present study we determined genome sizes as well as genome copy numbers for the endosymbionts of three cockroach species, Blattella germanica, Periplaneta americana and Blatta orientalis. The sole presence of blattabacteria in the fat body was demonstrated by rRNA-targeting techniques. The genome sizes of the three blattabacteria were determined by pulsed field gel electrophoresis. The resulting total genome sizes for the three symbionts were all approximately 650 +/- 15 kb. Comparison of the genome sizes with those of free-living Bacteroidetes shows extended reduction, as occurs in other obligatory insect endosymbionts. Genome copy numbers were determined based on cell counts and determination of DNA amounts via quantitative PCR. Values between 10.2 and 18.3 and between 323 and 353 were found for the symbionts of P. americana and B. orientalis respectively. Polyploidy in intracellular bacteria may play a significant role in the genome reduction process.

A total of 221 cockroaches (Blatta and Periplaneta spp.), collected in hospitals, houses, animal sheds, grocery stores and restaurants, in various parts of South Kanara District, a south-west coastal region of India, were studied bacteriologically for the presence of various salmonellas. Salmonellas were isolated from 4.1% of these cockroaches. Nine strains of salmonellas were recovered, belonging to five serotypes--Salmonella bovismorbificans, S. oslo, S. typhimurium, S. mbandaka and S. braenderup, the former two being the commonest serotypes. All salmonellas were resistant to one or other of 11 antibacterial drugs used in the susceptibility test. Isolation of salmonellas from cockroaches collected from the livestock premises and human dwellings suggested that they may act as significant reservoirs of salmonella in nature. Recovery of serotypes, phage types and R-types that were commonly isolated from humans and animals of this locality, suggested a transmission role for cockroaches. By harbouring potentially pathogenic, drug-resistant salmonellas, these wandering arthropods may pose dangerous infective hazards to humans and animals.

An immunolatex reagent was developed from antiserum to Fusobacterium varium, an obligate anaerobe isolated from the colon of the cockroach, Periplaneta americana L. A new technique that enabled the preparation of a highly efficient immunolatex conjugate was used to localize the bacterium with scanning electron microscopy, in situ, in the mixed gut contents.

A morphological study employing scanning and transmission electron microscopy was made by the alimentary tract of the American cockroach, Periplaneta americana L. A. complex microbiota of diverse morphology, which could not be readily dislodged, was observed and found to be restricted to the hindgut, particularly the colon. Numerous filamentous forms were noted, and some are described, including the morphologically distinct Methanospirillum. Flora was noted attached to the cuticular lining and cuticular filaments of the colon, and several spiral forms were observed in the luminal contents from the colon.

In Cairo's waste disposal sites various germs could be isolated from cockroaches and flies; antibiotic resistance was determined.