REVIEW ARTICLE Pseudomonas aeruginosa Resistance in Southeast Asia

Introduction : The increasing number of multidrug-resistant Pseudomonas aeruginosa worldwide need to be continuously monitored to prevent its transmission. This study reviewed multidrug-resistant Pseudomonas aeruginosa in Southeast Asia. Methods : Pubmed database was searched (January 2013-March 2018) for relevant articles using specific names of all eleven Southeast Asian countries. The articles retrieved were screened and analyzed to meet the inclusion criteria. Results : A total of 17 articles met the inclusion criteria. Vietnam had the most published data included in this study, East Timor, Cambodia, and Laos had none. There are variations among Pseudomonas aeruginosa resistance in Southeast Asia. Thailand had complete data on antibiotic resistance and had the highest resistance rate of almost all antibiotics. Colistin had the lowest resistance rate among all antibiotics. Conclusions : Colistin had the lowest resistance rate among all antibiotics. Another study with more extensive data should be done to validate this study. Future research should be explicitly providing detail data results for antimicrobial resistance analyses.


INTRODUCTION
Healthcare-associated infections (HAIs) or previously known as nosocomial infections are an infection that happens within 48 hours after admission in a health care facility. In surgery, the timing can extend up to 30 days (Haque et al., 2018). Surgical site infection (SSI), ventilator-associated pneumonia (VAP), catheterassociated urinary tract infection (CAUTI), and central line-associated bloodstream infection (CLABSI) are examples of HAIs (Al-Tawfiq and Tambyah, 2014). HAIs is major problem due to its high morbidity, mortality, and healthcare cost. The case fatality rate (CFR) for SSI, VAP, CAUTI, and CLABSI are 2.8%, 14.4%, 2.3%, and 12.3%, respectively (Al-Tawfiq and Tambyah, 2014). Most HAIs are caused by multi-drug resistance organisms (MDRO) (Haque et al., 2018). Pseudomonas aeruginosa is one of the most common MDRO that can cause HAIs (Nathwani et al., 2014, Treepong et al., 2018. Infectious Diseases Society of America (IDSA) even classify P. aeruginosa along with Enterococcus
Selection criteria and article quality assessment Inclusion criteria were articles written in English or Indonesian. The articles retrieved were screened by abstract reading by author and co-author independently. Any discrepancy found was being discussed. Scoring systems are used to assess article quality: valid and reliable identification methods, such as using Phoenix® (Becton Dickinson), Vitek® (bioMérieux), internationally standardized biochemical test, molecular (0 = no, 1 = yes); antibiotic susceptibility testing (AST) using an internationally standardized system, e.g., Clinical & Laboratory Standards Institute (CLSI) (0 = no, 1 = yes). Only articles value 2 were analyzed further. Data representing a mix of strains from several countries were excluded.

Data analysis
Data extracted included article information (first author's name, year of publication), study design (location, source of data, source of infection, type of infection, age group, antibacterial resistance), identification and AST method used. Data were analyzed using IBM® SPSS® Statistic 24. (SPSS, Inc, an IBM Company, Chicago, Illinois)

Study characteristic Population
Of the 17 articles included, 2013 was the year that has the most publications (Table 1). Vietnam and Thailand had most of the data (59%), Singapore, Malaysia, and Indonesia accounting for 35%, and there was one multinational study. Most of the articles had cross-sectional as their study design. Isolates were most commonly cultured from hospital-acquired infections of persons of all ages than solely from children or adults.

Laboratory methods
Method for identification used in the study from the highest number, respectively, were molecular, MALDI-TOF, API, and biochemically (Table 1). Disk diffusion was the most common method for AST used. Several studies did not mention their method of identification. They were a multicentre study that had followed the PPS methodology developed by ECDC and a review study. A study that did not mention their AST method was also a multicentre study and a molecular-based study. The multicentre study was following criteria from the Clinical and Laboratory Standards Institute guidelines (CLSI) and was enrolled in an external quality assurance program for microbiology.

Resistance rate
There were only Vietnam, Thailand, Indonesia, Singapore, and Malaysia that can be analyzed in this study regarding the resistance rate to different classes of antibiotics (Table 2). There were four studies from Vietnam, two studies from Thailand, and only one   study from Malaysia, Singapore, and Indonesia. This study calculated all the isolates numbers found in the articles into one specimen size for each country to be used as a numerator. Vietnam had the biggest isolates numbers, and others had less than 100 isolates. There was no specimen size found in the Indonesian study.
There was a variable P. aeruginosa resistance rate among countries for different classes of antibiotics. Thailand had the complete data of antibiotic resistance and had the highest resistance rate of almost all antibiotics listed (Table 2), except for carbapenem. Overall, Singapore had the highest resistance to carbapenem. But, if we look at individual data, one study from Vietnam had a 71% resistance rate on carbapenem . Colistin had the lowest resistance rate among all antibiotics.

Genetic Analysis
Reports from Malaysia and Thailand showed the possibility of drug-resistant Pseudomonas aeruginosa harboring integron spreading (Kor et al., 2013, Kiddee et al., 2013. Integrons are mostly located on transposon, with class 1 integrons are the most commonly found in antibiotic-resistant Pseudomonas aeruginosa (Kiddee et al., 2013, Kor et al., 2013 Sequence analysis from class 1 integron in Northern Thailand revealed resistance to aminoglycoside (aac, aad and aph), chloramphenicol (cmlA), β-lactams (blaPSE, blaOXA and blaVEB) and rifampicin (arr) (Kiddee et al., 2013) Study in Malaysia also found class 2 integrons from MDR Pseudomonas aeruginosa, although in small number of isolate, and

DISCUSSION
In this study, we found that in Southeast Asia, most P.aeruginosa was still sensitive to colistin. A similar result was found in Germany; from ten year period, researchers found that both MDR and non-MDR P.aeruginosa was still susceptible to colistin (Yayan et al., 2015).
Our study shows that P.aeruginosa resistance to antibiotic were endemic in almost all antibiotics. Class A ESBLs deliver resistance to expanded-spectrum cephalosporins and are inhibited in vitro by β-lactamase combination agents (Potron et al., 2015) Two isolates of blaPER-1, the first ESBL identified, was found in Vietnam (Tada et al., 2016) Class B β-lactamases hydrolyze carbapenems and other-lactams and not inhibited in vitro by β-lactamase combination agents (Potron et al., 2015) Resistance to carbapenems in P.aeruginosa is caused by reduced antibiotic permeability, includes a nontransmissible porin deficiency (reduction of OprD protein expression), efflux pump; and modification of antibiotics by overproducing β-lactamases (AmpC cephalosporinase) and metallo-β-lactamases (primarily IMP and VIM) (Apisarnthanarak et al., 2013, Khuntayaporn et al., 2013 Reduction in oprD transcription, mexAB-oprM mRNA overproduction and mexXY mRNA overproduction are the most prevalent resistance mechanisms, whereas AmpC overexpression is the least prevalent among Thailand carbapenem resistant P. aeruginosa clinical isolates (Khuntayaporn et al., 2013) In Southeast Asia, most carbapenemases-producer P.aeruginosa harbor blaIMP and blaVIM gene (Karuniawati et al., 2013) (Kazmierczak et al., 2016) (Kiddee et al., 2013) the most common gene cassettes were those encoding resistance to trimethoprim (dfr), and aminoglycosides (aad) (Kor et al., 2013) blaNDM-1 producer P.aeruginosa has been found in surgical intensive care unit in Singapore, suggested a transmission event (Teo et al., 2015) The resistance mechanism of Pseudomonas aeruginosa to aminoglycoside are due to enzymatic modification and the methylation of 16S rRNA. Eight plasmid-associated 16sRNA methylase genes are armA, rmtA, rmtB, rmtC, rmtD, rmtE, rmtF and npmA. rmtB was found in hospitals in Vietnam (Tada et al., 2013). Resistance P. aeruginosa to colistin remains unclear, with the linkage between genes PmrAB, PhoPQ, ParRS and CprRS (Bialvaei and Samadi Kafil, 2015).
We only used PubMed as a search engine, and that limits our data. We suggest further study using various search engine that is readily accessible to extend the number of the included articles. Experiencing difficulties in gathering the data, we also suggest researchers focusing on antimicrobial resistance to explicitly provide detail data both in the method and result section.

CONCLUSIONS
Colistin had the lowest resistance rate among all antibiotics. Another study with more extensive data should be done to validate this study. Future research should explicitly provide detail data results for antimicrobial resistance analyses.