A new study of cockroaches collected from an Iranian hospitals sheds light on how these insects can carry and spread resistant microbes.
Cockroaches. The mere use of the word elicits shudders and retches, even more so when you consider how these critters are often associated with disease and a lack of cleanliness. These insects have an affinity for human excrement and trash, which leads many of us to hit the panic button when we see them.
They’re gross when found in a home, but imagine if you stumbled across a cockroach within a hospital…
Not only is it a huge patient and staff dissatisfier to see one of these insects scuttling across the floor during medical treatment, but it presents a major issue for hospital administration, which can’t easily exterminate an entire hospital with insect spray. And unfortunately, the concern over cockroaches in hospitals goes beyond just the “ick” factor; the bugs can also put patient safety at risk from an infection control perspective.
Urban pests are a big enough concern that the World Health Organization (WHO) put together a report regarding the public health significance of pests in 2008.
Guess which pest landed first in the table of contents? That’s right—the cockroach.
The WHO noted that cockroaches are the “most significant pest found in apartments, homes, food-handling establishments, hospitals, and health care facilities worldwide.” Within the report, there is an entire table of pathogenic microbes isolated from cockroaches. This list ranges from Campylobacter jejuni, Klebsiella penumoniae, Salmonella Newport, Yersinia pestis, and includes a considerable amount of fungi and molds, not to mention poliomyelitis.
In addition to the WHO report, a recent study published in the journal of Antimicrobial Resistance & Infection Control identified resistant bacteria on hospital cockroaches in Iran.
From an infection prevention standpoint, this is pretty close to our worst nightmare. The investigators studied the phenotypic and genotypic characterization of the antibiotic resistance in the Methicillin-resistant Staphylococcus aureus (MRSA) strains that they isolated from cockroaches collected at the tertiary hospitals of the Tehran Province in Iran from 2016-2017. To capture the insect, they used sticky traps, vacuum cleaners, and hand-catch methods from human dwellings (that team of researchers deserves an extra round of applause). Traps were placed on the floors, under patient beds, in cupboards, wood racks, and under benches for 2 consecutive days. Following capture, the insects were placed in a sterile test tube and immobilized via freezing.
The study team tested 530 cockroaches via their gut content and external washing samples to isolate bacteria. From there, investigators divided out the MRSA strains via disk diffusion and polymerase chain reaction amplification of the resistance genes.
Following the laboratory work, the team found that the prevalence of MRSA varied a bit between the 2 kinds of cockroaches that were captured. These 2 different kinds are the most common in domestic, industrial, and residential areas. The Periplanets americana cockroaches had a MRSA prevalence of 52.77%, while the Blattella germanica cockroaches had a prevalence of 43.33%.
According to the study report, the external washing samples of P americana cockroaches had the highest prevalence of MRSA strains with 59.57% prevalence.
“MRSA isolates of external washing samples harbored the highest prevalence of resistance against penicillin (100%), ceftaroline (100%), tetracycline (100%), gentamicin (83.33%), and trimethoprim-sulfamethoxazole (80.55%),” the investigators concluded. “MRSA strains isolated from gut content samples harbored the highest prevalence of resistance against penicillin (100%), ceftaroline (100%), tetracycline (100%), trimethoprim-sulfamethoxazole (80%), and gentamicin (73.33%). BlaZ, aacA-D, tetK, msrA, dfrA, ermA, gyrA, grlA, and rpoB were the most commonly detected antibiotic resistance genes amongst the MRSA strains.”
This study reveals that not only are cockroaches a potential vector for resistant organisms, like MRSA, but they are also likely to carry resistant genes in their gut and externally. These findings also reinforce the need to be vigilant in health care setting in both environmental disinfection and pest remediation.