Fighting Operating Room Staphylococcus aureus Transmission—What Are We Missing?


A new study sheds light on sources of Staphylococcus aureus transmission in the operating room.

Investigators on a new study have found that high-risk pathogenic sequence types of Staphylococcus aureus are highly transmissible between patient procedures in the operating room, prompting a call for improved hand hygiene and patient decolonization compliance.

The operating room is a tough area to maintain sterility and cleanliness. The operating theater is large, filled with items, and inherently poses a unique risk for surgical site infections. Furthermore, frequent traffic in and out, gross spillage, attire inconsistency, the race to clean and prep the room for the next case upon operating completion, and more, are all things that facilitate germ transmission and complicate infection prevention within this environment.

Investigators from the University of Iowa sought to evaluate high-risk Staphylococcus aureus transmission in the operating rooms of academic medical centers across the United States. S aureus have evolved to not only acquire antibiotic resistance, but also increased virulence and ease of transmission. These very characteristics make it critical to assess how S aureus travels throughout the operating room.

The team of investigators randomly selected 274 case pairs (first and second case of the day in each of 274 operating room environments) from 3 academic medical centers. The team collected 8184 environmental and hand samples from the centers over the span of a year. They found 178 S aureus isolates, 173 of which were implicated in possible transmission, defined as “at least 2 S aureus isolates identified from 2 distinct reservoirs within or between cases in an intraoperative case pair,” according to the study authors. “An additional 5 isolates were identified in postoperative patient infection cultures without a possible intraoperative link.”

During this time, the investigators also monitored and tracked the institutions’ infection prevention policies, such as routine and terminal cleaning of the operating room and perioperative areas. To collect the samples, they considered workflow during a surgical case (ie, the anesthesia provider’s hands before, during, and after patient care; patient skin sites; pressure valves, etc). The investigators also tested for biofilms as these can be a place for organisms to proliferate and can reduce cleaning efficacy.

After anesthesia was administered to a patient, the investigators sampled the patient’s nasopharynx and axilla, as well as providers’ hands at the end of the case. They also tested for antibiotic susceptibility to identify if their isolates were resistant (tested against several antibiotics such as methicillin, cefazolin, ciprofloxacin, etc). The patients were tracked for 30 days postoperation to monitor for infection.

The anesthesia providers were deemed a source for in-case transmission if the transmitted isolate was clonally related to the isolate from the hands of 1 or more providers who were sampled on room entry prior to patient care. The environment was deemed the source for in-case transmission if the transmitted isolate from case 1 was clonally related to 1 or more isolates from case 2 (ie, the organism was transmitted from case 1 to case 2).

Of the 22 S aureus sequence types (STs) isolated from intraoperative reservoirs, there were 5 that accounted for a majority (71%) of the isolates. STs 5, 8, and 15, were associated with an increased risk of transmission (after adjusting for confounding variables). ST 5 was especially found to be a persistent germ; it was associated with an increased biofilm absorbance and multidrug resistance.

When the investigators evaluated post-operative infections associated with the organism cultured from intraoperative reservoirs at the time of the surgery, they found that the hands of anesthesia providers and patient skin surfaces were implicated as the intraoperative source.

Patient and provider hands are frequently a clonal source of infection and so this is not an entirely shocking finding. In 2 cases, environmental surfaces were identified as the clonal transmission location; however, of all the observed transmission stories, these occurred during the surgical case.

Overall, the investigators stressed the importance of understanding S aureus transmission and the epidemiological characteristics of ST 5 as an indicator for the modes of transmission during surgical cases. In fact, 2 of the ST 5 transmission events they observed were directly linked to infection. The importance of provider hand hygiene, environmental disinfection, and proper pre-operative bathing and use of disinfecting wipes cannot be stressed enough for preventing surgical site infections.

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