Introduction
Antimicrobial resistance is a natural evolutionary phenomenon that bacteria have developed as a defence mechanism in the presence of an antimicrobial. In recent years, alarm and concern has been generated by the large spread of carbapenem-resistant enterobacteria in which the mechanism involved is the production of β-lactamases called carbapenemases, which spread efficiently by colonising skin, mucous membranes and the environment through contact 1. Carbapenemases are transferred to other bacteria via mobile genetic elements 2 3, causing a large number of infections, with limited therapeutic options inhibiting virtually the last therapeutic link against multidrug-resistant gram-negative microorganisms 345. This has taken on great importance worldwide due to the increase in morbidity and mortality rates and hospital costs.
Numerous studies have shown that the gastrointestinal tract is the main reservoir for this type of multidrug-resistant microorganisms 67289.
Patients in intensive care units are at high risk of developing a hospital-acquired infection, as they are frequently exposed to invasive devices and have associated comorbidities 10.
One of the primary strategies to prevent the spread of CLD (carbapenemase-producing Enterobacteriaceae) is active epidemiological surveillance. This is done by timely detection of these CLDs through anal swabs from patients. In the event of a positive finding, strict contact isolation measures 811 are measures to prevent their spread and possible outbreaks 6712.
Detection of these CLDs is a very important task of microbiology laboratories in hospitals. As their prevalence is increasing worldwide, the implementation of phenotypic screening methods, as well as their subsequent confirmation, represent a challenge for microbiologists 13146.
Materials and methods
A retrospective descriptive study was conducted, analysing anal carriage studies for CLD in the polyvalent intensive care unit (ICU) and modular COVID (COVID-ICU) services of the Hospital Dr. J. C. Perrando between January and August 2021 15.
Anal swabs were performed fortnightly on all patients admitted to the Hospital for more than 7 days, patients referred from other institutions and infected/colonised patients after 3 months, according to the active surveillance protocol provided by the Hospital's Infection Prevention and Control Committee 15.
The primary culture was performed on CHROMAGARTM KPC selective medium. Strains growing on this medium were typed to identify the microorganism involved. Carbapenemases were detected by means of the BLUE CARBA and DCMBRIT (Britania) methods using the Kirby-Bauer technique (agar disc diffusion antibiogram) and following the carbapenemase search algorithm provided by the Antimicrobial Service, National Antimicrobial Reference Laboratory, INEI-ANLIS "Dr. Carlos G. Malbrán", in agreement with the National Antimicrobial Reference Laboratory, INEI-ANLIS "Dr. Carlos G. Malbrán". Carlos G. Malbrán, agreed upon for the Latin American Network for Antimicrobial Resistance Surveillance (RELAVRA), (Protocolos |antimicrobianos.com.arantimicrobianos.com.ar). The algorithm proposes the strategic placement of discs, in order to detect the different types of carbapenemases (KPC, MBL, OXA, or double carbapenemases if present) by observing synergies between different antibiotics.
Once the positive portions were detected, it was observed whether these patients developed a subsequent infection involving the same enzyme.
Results
379 anal swabs were performed, 26% (n=98) were positive for CLD.
K. pneumoniae was the most frequent CLD with 69% (35/51) of isolates coming from COVID-UTI and 90% (42/47) from UTI. The remaining carbapenemases were K. aerogenes isolates in 15% (8/51), E. cloacae in 10% (5/51), P. mirabilis, K. oxytoca and C. freundii in 2% (1/51) from COVID-UTI, as well as K. oxytoca, P. mirabilis in 4% (2/47) and C. freundii in 2% (1/47) from UTI.
Figure 1 2 3 shows the variation in the number of positive portions in both services in the period under study.
Of the total number of patients presenting with UTI and COVID-UTI carbapenemase infection in the period studied, only 15% had a previous carriage study involving the same enzyme.
Discussion
Consistent with the literature, K. pneumoniae was the most frequent CLD 161718, although it was found in other species in lower percentages.
In graph 1, a gradual increase in positive carriage was observed in both services, reaching a peak in August. The increase in CLD observed in this period coincided with the increase in patients hospitalised for COVID-19 during the second wave in the province (March-August 2021). Despite all the measures implemented to try to control the spread of infections, closely linked to the cleanliness of the environment in general, hand washing, proper use of personal protective equipment, they have been on the rise.
The observed increase in the number of positive portions was more significant in patients who were in COVID-ICU than in polyvalent ICU, coinciding with the findings of Fernandez et al 19. This may be due, at least in part, to the seriousness with which these patients are admitted and the longer hospital stay, a factor that predisposes to colonisation by multidrug-resistant microorganisms 120.
Recent national studies show that more than 70-80% of patients diagnosed with SARS-COV-2 received antibiotic treatment. This may cause a significant increase in the selection of resistant bacterial pathogens, along with the emergence of other associated infections 24.
Between 2017 and 2019, in Argentina the most frequent carbapenemase type was KPC, which was gradually displaced by MBL types. In our study we were able to observe that the most frequently isolated carbapenemases from carriage studies have been MBLs.
Currently, cases of co-production of MBL + KPC carbapenemases have been reported 2122. The Antimicrobial Service of the INEI-ANLIS "Dr. Carlos G. Malbrán" (National Reference Laboratory, LNR) has alerted during the first wave of the COVID-19 pandemic, the emergence and spread of colonisation/infection by carbapenemase combination-producing Enterobacteriaceae in Argentina 23, which put the health system on alert for the abuse or misuse of antibiotics in general and during the context of COVID-19 infection 24. In March 2021, the Microbiology Service of Hospital Perrando referred a strain with carbapenemase to the National Reference Laboratory for confirmation, which was typed as K. pneumoniae with double carbapenemase KPC + MBL (NDM) (unpublished data).
Faecalcolonisation prior to the development of infection in our study was 15%. This is a warning regarding the ability of the mobile genetic elements containing carbapenemases to spread between genera and species, as they were found in different species. This is important to know not only from an infection control point of view, but also for the choice of empirical treatment of these patients 25. Factors involved in the rapid spread of carbapenemase-producing strains include poor hand and environmental hygiene, indiscriminate use of broad-spectrum antibiotics, poor adherence to infection control measures and overcrowding of the healthcare system.
Conclusions
Colonisation by CLD is one of the main routes for the spread of these resistance mechanisms, which is why it is a priority to carry out systematic active surveillance studies. The institutional protocol for rectal screening is an epidemiological surveillance strategy aimed at preventing outbreaks in the different services, mainly in critical care units, which allows the identification of possible patients colonised by multidrug-resistant microorganisms, thus allowing them to be isolated and the patient to be managed in order to avoid future complications.
We warn about the emergence of multi-resistant micro-organisms in closed areas such as intensive care units, where the use of broad-spectrum antibiotics has a strong impact on the flora of the patients assisted, presenting an ideal scenario for the selection of these multi-resistant strains and their consequent dissemination.