The Five Years Surveillance and Trends of Antibiotic Resistance in Some Common Gram Negative Bacteria at the Vietnam Military Hospital

The study is to identify trends and levels of antibiotic resistance of some common Gram-negative strains over time. The samples were collected from Vietnam Military Hospital 103 between 2014 and 2019. A total of 405 Acinetobacter baumannii, 528 Pseudomonas aeruginosa, 741 Escherichia coli, and 352 Klebsiella pneumoniae strains were identified and antimicrobial susceptibility was by Vitek system and Etest method. The multi-drug resistance (MDR) was major proportion of four common bacteria. In particular, there is a tendency to shift from MDR to Extended drug resistance (XDR) or possibly Pan drug resistant (pPDR). A. baumannii had the highest level of antibiotic resistance, namely, carbapenem (61.5% - 82.5%) and cephalosporin (72.7% -88.7%). P. aeruginosa resisted most of commonly antibiotics, ranging from 50% to 70%. E. coli had a high resistance with antibiotics like ampicillin (87.2% - 97.6%) and the 3rd generation cephalosporins (up to 79.6%). K. pneumoniae resisted carbapenem from 14.7% to 44.4%, and other antibiotics with the higher rate of 40%. The collected data will be a prerequisite for fur-ther studies on mechanisms and factors related to antibiotic resistant bacteria, in order to find out a rational and effective using strategy of antibiotics.

Advances in Microbiology fectious diseases. However, the widespread use of antibiotics in the past decades has led to the emergence of multi-drug resistant bacteria. It caused a difficulty in infection treatment, influenced on the cost and days of treatment. It is a risk of facing global health sector [1].
Recognizing the importance of antibiotic-resistance of bacteria, global scientists and Vietnamese ones continuously research with a hope of reducing and controlling this problem. In February 2017, the World Health Organization (WHO) released a list of 12 strains of antibiotic-resistant bacteria that should be a top priority in researching and discovering new antibiotics [2]. Gram-negative bacterial strains are primary concern because of their potential to cause hospital infections and drug resistant level. Among the agents of Gram-negative bacteria, four common bacteria A. baumannii, P. aeruginosa, E. coli and K. pneumoniae are the most mentioned species studies. Because they are not only the causes of serious infections such as sepsis, pneumonia, urinary infections and hospital infections but also the agents that are resistant to many common antibiotics [3].
Unsurprisingly, most of the mentioned strains have appeared in Vietnam. The concern is that these strains have resisted many different antibiotics and increased resistant levels over time [4] [5].
Gram-negative bacteria have been always mentioned by many studies, because their antibiotic resistance has changed over time and geographic area [6]. It is necessary to regularly monitor and study the trends as well as the level of resistance of bacteria. The aim for the clinicians has a reasonable and effective strategy in use and store antibiotics in different areas in order to improve treatment quality and limit transmission of multi-resistant strains. In addition, the results also provided extra data to finalize the global report of antibiotic resistant bacteria.
In fact, there is a great difficulty in choosing antibiotics for treatment. So, this study focuses on showing kinds of antibiotics that the common bacteria are increasing their resistance and/or sensitive in recent years.

Statistical Analyses
The data collected during the research period of the project is processed according to medical statistical methods, using WHONET 2019 antibiotic management and analysis software. Comparative testing using EpiCal 2000 software, the p values < 0.05 was considered statistically significant.

Characteristics of Drug Resistant Trends
For all four common Gram-negative bacteria, the rates of multi-drug bacteria were higher than those of resistant bacteria under 3 antibiotic groups (p < 0.05).
In particular, the rate of multi-resistant of A. baumannii tended to increase gradually over the years of research ( Figure 1).
The multi-drug resistant (MDR) strains were major proportion of the 4 species of common bacteria. In particular, there is a tendency to shift from MDR to

The Level of Antibiotic Resistance of Some Gram-Negative Bacteria Isolated
A. baumannii was resistant with almost common antibiotics and tended to increase over time. Between 2017 and 2019, the antibiotic resistant rates of A. baumannii were over 80% ( Figure 3).
The rate of resistance with imipenem and meropenem in 2014 was 61.5% and 70.8%. In 2019, both of rates increased to 81.8%. Amikacin and co-trimoxazole were still susceptible with A. baumannii. The level of resistance tended to decrease over time, but the overall resistant rates with these were quite high, at 30.0% and 37.4% respectively. Figure 4 indicated that the typical level of antibiotic resistance in P. aeruginosa was high (>50%) and tended to increase over time (p < 0.05). This bacterium was resistant with quinolones at a very high rate:   generation cephalosporins and quinolones (norfloxacin and ciprofloxacin) (p < 0.05). However cefepim, there was a slight decrease in the resistant rates but the difference between annual rates was not significant (p > 0.05) ( Figure 5).
Klebsiella pneumoniae was resistant to many antibiotics such as cephalosporins, quinolones, aminoglycosides, and co-trimoxazole with the ratios from 25.8% to 60.7%. The level of resistance to many antibiotics increased in 2015 and H. T. T. Van  fosfomycin, amikacin, amoxicillin/calvulanic acid ( Figure 6).

Discussion
In the short time the antibiotic was discovered and put into treating infections, the bacteria was able to resist them. It was found that the more antibiotics used, the faster they became resistant. In the race between finding a new antibiotic and the speed of increasing antibiotic resistance of bacteria, it seemed that bacteria always took the initiative. The natural selection pressure and the struggle for survival among bacteria have helped them an antibiotic resistant ability. Moreover, the combination of antibiotics in treatment led to multidrug resistance of bacteria [12].
During the study, we found that the percentage of more than 3-antibiotic group resistant bacteria was higher than the rate of less than 3-antibiotic group resistant bacteria in all four bacterial species. In partially, the rate of multi-resistant bacteria has increased over time. It led to a difficulty in selecting antibiotics for infection treatment in our hospital. Comparing with Japanese data in the 2018 annual monitoring report, the proportion of antibiotic resistant bacteria in 103 military hospital of Vietnam was much higher than the Japanese hospital (Table 1) [13].
The research and classify MDR, XDR and PDR strains were followed to the standards of the European Center for Disease Control and Prevention (ECDC) [12]. In this study, it was really worried that in all four common gram-negative bacilli, the rates of multi-drug resistant bacteria were more than 50% and this percentage had been increasing during the study period. For example, the mul- It can be said that A. baumannii was one of the most mentioned bacteria in the last 15 -20 years, because it was the most serious nosocomial infection agent and resisted many different kinds of antibiotics. Therefore, WHO has been prioritized in research new antibiotics [2]. The results showed that the antibiotic resistant rates of A. baumannii were large with all most antibiotic groups such as cephalosporins, aminoglycosides, and fluoroquinolones. Even with carbapenem, which is a strong antibiotic, A. baumannii was not only resistant more than 50% but also increased over time. However, A. baumannii resisted amikacin and co-trimoxazole with low rates and decreased slowly every year. It is a good sign in selection of antibiotics for treatment A. baumanni (Figure 3). Other studies were shown the similar results in study A. baumannii from different areas [4] [5] [14] [16] [17] [18]. However, in a report from 2013 to 2017 of Malaysia were showed a difference. For example, A. baumannii was lower resistant imipenem, meropenem, and ceftazidime than our results with ranging from 55% -62%, and it also resisted amikacin with the higher rates from 42% to 50% [19]. In another research from Mexico between 2005 and 2012 showed that the resistant percentage of A. baumannii to meropenem was from 17.7% to 33.0%, was not as high as the figure in this research [6]. In significant, in different time and regions the antibiotic resistant level of A. baumannii was different. Therefore, the monitoring of drug resistance should be conducted regularly and continuously.
Similar to A. baumannii, P. aeruginosa had a high level of resistance and increasing tendency with many antibiotics over time. This is a challenge in treating these strains in the near future. Here results were quite the same as the results from other studies [4] [20]. According to this research, E. coli were generally resistant rate lower than that of A. baumannii and P. aeruginosa. The rate of resistance increased over time such as cefotaxim, ciprofloxacin, and co-trimoxazole.  [25]. The carbapenem resistant rate increased significantly from 10% to 45%. Fortunately, K. pneumoniae still tended to significantly reduce the resistance with some antibiotics like ertapenem, fosfomycin, amikacin, and amoxicillin/calvulanic acid. It can be said that selecting antibiotics for treatment of A. baumannii and P. aeruginosa strains are more difficult than choosing drug in treatment for E. coli and K. pneumoniae strains.

Conclusions
Although the study was conducted in only a hospital, it is a military central hos-