Antimicrobial Susceptibility of Some Natural Oils against Acinetobacter Species
Received Date: Nov 02, 2017 / Accepted Date: Nov 14, 2017 / Published Date: Nov 22, 2017
The in vitro activities of 18 natural oils and 14 antimicrobial agents against 72 Acinetobacter isolates isolated from 1000 patients in Aswan University hospital over 18 months obtained from urine cultures, burn swabs, sputum, wound swabs and endotracheal swabs were studied. MICs were determined by an Agar dilution method. The antimicrobial activity of plant oils has been recognized for many years. However, few investigations have compared large numbers of oils using methods that are directly comparable. In the present study, 18 plant oils were investigated for activity against Acinetobacter isolates, using an agar dilution method. Cinnamon, thyme, tea tree, rosemerry, peppermint, clove and lavender, inhibited all organisms at concentrations of ≤ 6 mg/ml. Four oils did not inhibit any organisms at the highest concentration, which was 6 mg/ml oil for tea, camphor, caraway and Nigella staive. Variable activity was recorded for the remaining oils. These results support the notion that plant essential oils and extracts may have a role as pharmaceuticals and preservatives.
Good activity against Acinetobacter isolates was demonstrated for imipenem, amikacin, and ciprofloxacin. Most of isolates were susceptible to imipenem, ciprofloxacin, expanded-spectrum cephalosporins, amoxicillin-clavulanate, and the aminoglycosides but were resistant to ampicillin and older cephalosporins.
Keywords: Acinetobacter, MIC, Antimicrobial activity, Natural plant oils
Acinetobacter is a genus of Gram-negative bacteria belonging to the wider class of Gammaproteobacteria. Acinetobacter species are not motile and oxidase-negative, and occur in pairs under magnification. Acinetobacter species are a key source of infection in debilitated patients in the hospital, in particular the species Acinetobacter baumannii. Species of the genus Acinetobacter are strictly aerobic, nonfermentative, Gram-negative bacilli. They show preponderantly coccobacillary morphology on nonselective agar. Rods predominate in fluid media, especially during early growth .The morphology of Acinetobacter species can be quite variable in Gram-stained human clinical specimens, and cannot be used to differentiate Acinetobacter from other common causes of infection. They are oxidase-negative, nonmotile, and usually nitrate-negative . Acinetobacter species are widely distributed in nature, and commonly occur in soil. They can survive on moist and dry surfaces, including in a hospital environment. Some strains have been isolated from foodstuffs. In drinking water, they have been shown to aggregate bacteria that otherwise do not form aggregates . Acinetobacter is frequently isolated in nosocomial infections, and is especially prevalent in intensive care units, where both sporadic cases and epidemic and endemic occurrences are common. A. baumannii is a frequent cause of nosocomial pneumonia, especially of 'late-onset' ventilator-associated pneumonia. It can cause various other infections, including skin and wound infections, bacteremia, and meningitis, but A. lwoffi is mostly responsible for the latter. A. baumannii can survive on the human skin or dry surfaces for weeks. Epidemiologic evidence indicates Acinetobacter biofilms play a role in infectious diseases such as periodontitis, bloodstream infections, and urinary tract infections, because of the bacteria's ability to colonize indwelling medical devices (such as catheters). Antibiotic resistance markers are often plasmid-borne, and plasmids present in Acinetobacter strains can be transferred to other pathogenic bacteria by horizontal gene transfer. The ability of Acinetobacter species to adhere to surfaces, to form biofilms, and to display antibiotic resistance and gene transfer motivates research into the factors responsible for their spread .
The spread of drug resistant pathogens is one of the most serious threats to successful treatment of microbial diseases. Down the ages essential oils and other extracts of plants have interest as sources of natural products. They have been screened for their potential uses as alternative remedies for the treatment of many infectious diseases . World Health Organization (WHO) noted that majority of the world's population depends on traditional medicine for primary healthcare. Medicinal and aromatic plants which are widely used as medicine and constitute a major source of natural organic compounds. Essential oils have been shown to possess antibacterial, antifungal, antiviral insecticidal and antioxidant properties [5,6]. Some oils have been used in cancer treatment . Some other oils have been used in food preservation , aromatherapy  and fragrance industries . Essential oils are a rich source of biologically active compounds. There has been an increased interest in looking at antimicrobial properties of extracts from aromatic plants particularly essential oils . Therefore, it is reasonable to expect a variety of plant compounds in these oils with specific as well as general antimicrobial activity and antibiotic potential . Essential oils (also called volatile oils) are aromatic oily liquids obtained from plant materials (flowers, buds, seeds, leaves, twigs, bark, herbs, wood, fruits and roots). They can be obtained by expression, fermentation or extraction but the method of steam distillation is most commonly used for commercial production. An estimated 3000 essential oils are known, of which 300 are commercially important in fragrance market . Essential oils are complex mixers comprising many single compounds. Each of these constituents contributes to the beneficial or adverse effects. Essential oils such as aniseed, calamus, camphor, cedar wood, cinnamon, citronella, clove, eucalyptus, geranium, lavender, lemon, lemongrass, lime, mint, nutmeg, orange, palmarosa, rosemary, basil, vetiver and wintergreen have been traditionally used by people for various purposes in different parts of the world. Cinnamon, clove and rosemary oils had shown antibacterial and antifungal activity ; cinnamon oil also possesses antidiabetic property . Anti-inflammatory activity has been found in basil . Lemon and rosemary oils possess antioxidant property [15,16]. Peppermint and orange oils have shown anticancer activity [17,18]. Citronella oil has shown inhibitory effect on biodegrading and storage-contaminating fungi . Lime oil has shown immunomodulatory effect in humans . Lavender oil has shown antibacterial and antifungal activity; it was also found to be effective to treat burns and insect bites .
Materials and Methods
Collection of isolates
Isolates were collected from different departments of Aswan University hospitals and these isolates collected from patients after history taking and complete clinical examination then sample collected from different types of samples according to methods explained in in references that follow the type like urine , burn swabs, wound swabs , sputum  and endotratracheal swabs  from 1000 patients over 18 months. 72 isolates were identified as Acinetobacters isolates by using VITEK 2.
Identification with the VITEK 2 system was performed with ID-GNB cards, according to the manufacturer's instructions. The 64-well plastic ID-GNB cards contain 41 tests, including 18 tests for sugar assimilation, 18 tests for sugar fermentation, 2 decarboxylase tests, and 3 miscellaneous tests (for urease, utilization of malonate, and tryptophane deaminase). With a vacuum device, the cards are inoculated with a 0.5 McFarland suspension of the organism prepared from an 18- to 20-h-old Columbia sheep blood agar plate (bioMérieux) and are then automatically sealed and manually inserted inside the VITEK 2 reader-inoculator module. Fluorescence is measured every 15 min, and the results of identification are determined after 3 h.
The study used 18 natural oil including cinnamon oil, lavander oil, peppermint oil, thyme oil, orange oil, lemon oil, garlic oil, ginger oil, jasmine oil, green tea oil, tea tree oil, parsely oil, carway oil, red rose oil, rosemerry oil, camphor oil, nigella sativa (black seed) all of these oil obtainted from Tanta University medical plants departments which was pursed these oils from sigma company except (tea tree oil ,tea oil ,garlic oil pursed from sigma company) and the oils diluted with DMSO to obtain serials of dilutions and DMSO was used as control for these oils.
Antimicrobial Susceptibility Testing
MIC agar dilution assay
A. Preparation of essential oils containing media
Muller-Hinton agar (MHA) was used as a basal medium. Sterile Mueller-Hinton agar (MHA) was allowed to equilibrate to about 50°C in a water bath. A series of two fold dilution of each oil in DMSO ranging from 0.125 to 6 mg/ml were added to the molten agar prior to inoculation. A plate containing identical amount of the basal medium, but free from essential oil was used as control. Plates were dried at room temperature for 30 min prior to inoculation.
B. Preparation of the inoculum
Two or three discrete representative overnight colonies, of each tested isolate were inoculated into 2 ml sterile saline, homogenized by vortex mixer and diluted to obtain OD values of 0.05 at 600 nm. Aliquot of the prepared suspension of each isolate was transferred by automatic pipette to a certain well in the seed plate of a sterile multiinoculator according to a configuration of a record key. Each well in the seed plate was half filled to avoid the carry over problem.
C. Inoculation and incubation of the plates
The plates were inoculated as follows; the head with sterile inoculating rods was gently lowered into the well in the seed plate, gently raised and gently lowered onto the surface of the agar medium.
D. Recording the results
After 24 hrs of incubation at 37°C for bacteria, MIC was determined as the lowest concentration of essential oil inhibited visible growth of the microorganism compared with the growth in the control plate. The presence of one or two colonies was not taken into account for final assessment of MIC [25,26].
Susceptibility of Tested Isolates to Different Antimicrobial Agents
MICs of antimicrobial agents against all bacterial isolates were determined using the agar dilution method according to the procedure previously described but instead of essential oil, membrane filtered stock solution of each tested antimicrobial agent was prepared. Serial dilutions of the tested antimicrobial agent solutions ranged from 0.125 to 6 mg/ml were added to the molten agar prior to inoculation. There are 14 antibacterial agents tested in this study the break points for these antibiotics were used according to CLSI (2017) guidelines .
Table 1 shows the incidence of Acinetobacter infection in ICU and burn unit. Table 2 and Figure 1 shows the incidence of Acinetobacter isolates in relation to other organisms in this study. Table 3 shows the relation between frequency of Acinetobacter infection and underlying disease in ICU of the studied cases. Table 4 shows the invasive procedures in respiratory tract Acinetobacter infection as a risk factor. Table 5 shows the Invasive procedures in urinary tract Acinetobacter infections as a risk factor.
|Sites||Burn unit||ICU||Other unit|
|Acinetobacter isolates (n=63)||n||%||n||%||N||%|
|It shows that Acinetobacter isolated from burn unit were (52.8%) and from ICU were (34.7%) among the nosocomial isolates.|
Table 1: Incidence of Acinetobacter infection in ICU and burn unit.
|Total number of||Acinetobacter||Other organisms|
|It shows that the incidence of Acinetobacters was 17.8% among the total isolates.|
Table 2: Incidence of Acinetobacter isolates in relation to other organisms in this study.
Table 3: Relation between frequency of Acinetobacter infection and underlying disease in ICU of the studied cases.
|Acinetobacter Nis||Invasive procedure|
|Acinetobacter RTIs (n=52 ) isolates||Ventilated patients||Non Ventilated patients|
|It shows that the rate of Acinetobacter respiratory tract infections was higher in ventilated patients.|
Table 4: Invasive procedures in respiratory tract Acinetobacter infection as a risk factor.
|Acinetobacter Nis||Invasive procedure|
|Acinetobacter RTIs (n=52 ) isolates||Catheterized Patients||Non Catheterized Patients|
|It shows that Acinetobacters UTIs were higher in catheterized patents.|
Table 5: Invasive procedures in urinary tract Acinetobacter infections as a risk factor.
This study were done to obtain detailed study about antimicrobial activity of 18 essential oil against Acinetobacter isolates that have considerable degree of resistance to a wide range of recommended antibiotics. All of the Acinetobacter included in this survey were isolated from clinical specimens and were considered to be significant by the referring laboratory.
One of the most important nosocomial pathogen are Acinetobacters as they are often resistant to numerous antimicrobial agents and cause life-threating infections in patients with altered host-defense mechanisms. In addition, they have a tendency toward cross-transmission, especially in ICUs, where numerous outbreaks have occurred .
As a little is known about Acinetobacters infection in our hospital, the current study aimed to identify the prevalence of Acinetobacters, in Aswan University Hospital as nosocomial pathogen. The present study also aimed to detect the resistance rate of Acinetobacters to different antimicrobial agents and different natural oils. For this purpose, 1000 samples were collected randomly from ICU of Anaesthesia Department and Internal Medicine Department as well as Burn Unit, Aswan University Hospital. Out of these 1000 samples 72 samples were detected as Acinetobacters. Several automated systems are available for the identification and susceptibility testing of the clinically most important bacteria . The VITEK system (bioMérieux-Vitek, Hazelwood, Mo.) was originally designed as an onboard system for the detection and identification of Acinetobacter pathogens. It was first introduced in clinical laboratories in 1979 and has since been evaluated extensively . More recently, the new VITEK 2 system (bioMérieux-Vitek) was introduced. The VITEK 2 system detects metabolic changes by fluorescence-based methods which facilitate the identification of gram-negative bacteria within 3 h. This system monitors the kinetics of bacterial growth and calculates MICs using a unique algorithm. In addition, the VITEK 2 system incorporates several technical improvements which automate many procedures that were performed manually with the previous VITEK system (Gayral et al., Clin. Microbiol. Infect. abstr. P254) and for this Evilo J Perea use VITEK 2 to identify Acinetobacters with high correct limits .
In this work the rate of NIs was 40.5% this result was smaller than that of Ozer  and his colleagues study who aimed to determine the types and risk factors for NIs in the ICU of Turkey University Hospital. They found that the rate of NIs was 68%which higher than that found in current study.
While  who stated that the rate of NIs in their study was 20% and  detected lower incidence of NIs 12.2%, these results were lower than the current one. NIs varies between different studies in different countries according to the establishment of preventive measures and developmental status and between the hospitals according to the spectrum of their patients and between the wards of the hospitals according to treatment and intervention .
In the present study, the incidence of Acinetobacter among the nosocomial isolates was 17.8% these results correlate with Radwa Essa result who reported that Acinetobacters account for 13.9% of NIs and  who reported that Acinetobacters 11% of NIs which was explained by previous exposure of the patients to various risk factors as ventilation, urinary catheterization and surgical operations. Also the results were similar to those of , who found that Acinetobacters represented 9% of bacteriologically positive samples collected from teaching hospital in India. This can be explained by previous report made by  which had shown that there is a relatively high frequency of Acinetobacter infection in hot countries as hot climate and humidity favors Acinetobacter infection. However, these finding were higher than those of  who stated that Acinetobacters represent 1.43% of all nosocomial isolates over a six year period. This may be attributed to the antimicrobial therapy received by his patients before Acinetobacters isolation. On the other hand,  found that Acinetobacter isolates among nosocomial infections represent 32.8% which was higher than the current study. This was attributed to exposure of all his patients to several risk factors especially prolonged stay in ICU for more than 15 days before Acinetobacters isolation. In this work Acinetobacters were isolated from urine, sputum, tracheal aspirates, surgical wounds and burn samples. Acinetobacters were most commonly isolated from urine samples 29.6% followed by respiratory tract samples including sputum and tracheal aspirates 26.9% and surgical wound samples 23.5% and lastly from the burn samples in which Acinetobacter isolates represent 17.8% these results are in line with that of , who isolated Acinetobacters most commonly from urine samples 31% followed by respiratory tract and wound samples which represent 26.7% and 17.8% respectively. On contrary to our results  stated that Acinetobacters is most commonly isolated from respiratory tract samples 38.5%. Also  estimated that Acinetobacter respiratory tract represented by 54% followed by wound infection 22%. This variation is explained by Bergogne-Berezin  who stated that the predominant sites of Acinetobacter nosocomial infection have varied with time. In early observations, UTIs predominated in ICUs. Recently the incidence of UTIs has decreased, possibly in relation to better care of urinary catheters, whereas the incidence of nosocomial pneumonia has increased significantly as reported in several recent surveys.
The incidence of Acinetobacter infection is high in ICU patients who always exposed to various risk factors as prolonged hospital stay, medical devices especially central venous catheters, heavy exposure to broad- spectrum antimicrobial drugs especially cephalosporins, surgical operations and severe illness. So in the current study, ICU admission may be considered as a risk factor for Acinetobacters acquisition. This runs in parallel with both  who reported that Acinetobacters are common pathogen particularly in ICUs where risk factors of colonization and infection with Acinetobacters are present and  who stated that ICU admission was associated with MDR A. baumannii acquisition while  who found that Acinetobacters are an important cause of clinical infection especially in patients hospitalized in ICUs. Also Blot and his colleagues observed that patients with A. baumannii had longer ICU stay . This was also accepted by  who reported that outbreaks of HAIs caused by Acinetobacters are recognized particularly in ICUs. Medical device insertion play an important role in Acinetobacter infection, in the present work the incidence of Acinetobacter infection in ventilated patients is higher than in nonventilated patients, also in case of urinary catheterization the incidence of Acinetobacter infection in catheterized patients is higher than in non-catheterized patients. This is coordinated with the finding of  who stated that mechanical ventilation and urinary catheterization are risk factors for Acinetobacter NI.
The essential oils tested in the present study were found to inhibit Acinetobacter isolates. The MIC value does not depend on the level of bacterial resistance. Parkasm et al.  report that clove, peppermint possess antibacterial activity against Acinetobacter isolates obtained from variable clinical specimens as endotracheal aspirates, urine, burn swabs and sputum . This study has demonstrated that seven natural oil inhibit Acinetobacter isolates at high concentrations which is cinnamon, thyme, rosemerry, clove, tea tree, peppermint and lavender, inhibited all organisms at high concentrations of ≤ 1024 µg/ml. Four oils did not inhibit any organisms at the highest concentration, which was 1024 µg/ml oil for tea, camphor, parsely and Nigella staive. However, the present finding suggest that while oils should be used in diluted form, especially when directly applied to skin, their antimicrobial properties are effective as those of chemical antibacterial agents. In addition, it is important that the microorganisms do not acquire resistance to the natural oils or to their components . The lowest concentration of oils that inhibited the growth of Acinetobacter isolates were considered as MIC. The essential oils tested in the present study were found to inhibit Acinetobacter isolates from patients. The MIC value does not depend on the level of bacterial resistance  proved high antibacterial activity of essential oil from Cinnamon oil against gram negative bacteria in this study MIC of cinnamon oil at concentration ranging from 0.25 to 4 mg/ml and MIC of lavender at concentration ranging from 0,5 to 4 mg/ml and MIC of thyme ranging from 0.5 to 2 mg/ml which is similar to result proved by  and MIC of tea tree oil at concentration 0.5 to 1mg/ml which is proved in paper by name Tea tree oil–natures miracle in fighting infections and other problems. MIC of rosemerry at concentrations 3 to 5 mg/ ml. MIC of peppermint at concentration 0.5 mg/ ml and MIC of clove at concentration 0.5 to 3 mg/ml, and all of these oils inhibit all isolates at high concentration. MIC of lemon oil at concentration 2 to 5 mg/ml which is similar to result proved by Edeltrudes de Oliveira Lima and orange oil have similar results. MIC of Red rose oil at concentration 1 to 4 mgl/ml which similar to result in paper by name The Antimicrobial effect of Aqueous extract of garlic against resistant Enterococci and MIC of ginger is like garlic oil and this indicate that they are weak against Acinetobacter isolates which and this result similar to result e in paper by name antimicrobial active herbal compound against A. baunmanni and other pathogen. other natural oil not have any activity against acinetobacter like nigella sative (black seed oil), caraway, camphor, parsely and tea oil .and that result of nigella sative oil obtained from seed and leaves have no activity confirmed in Antibiotic Resistance: Mechanisms and New Antimicrobial Approaches edited by Kateryna Kon, Mahendra Ral in chapter 12. Hammer et al. determined the antimicrobial activity of 53 essential oils, including oil of thyme, against various bacterial species with the use of serial dilution technique, both agar and broth. The minimum inhibitory concentrations with thyme oil to the reference strain NTCT 7844 of A. baumannii was 0.12 µL/mL and P. aeruginosa NTCT 10662-over 2 µL/mL). In this study the most powerful oils were cinnamon, thyme, lavender, clove and tee tree oils with MIC range from 0.125 to 1 mg\ml and this very useful in the treatment of Acinetobacter nosocomial infection which is a big problem this result is similar to results  and oils with moderate effect like lemon and orange, which their MIC >2 mg\ml which also similar to results given by . Also peppermint oil also has powerful antimicrobial activity with MIC range 0.5 to 3 mg\ml and this results similar to that given by  with MIC range 0.5 to 1 mg\ml and red rose oil have moderate effect with MIC 1 to 4 mg\ml which similar to results of  whose results was MIC from 2 to 4 mg\ml. and ginger give moderate antimicrobial effect with MIC from 1 to 4 mg\ml which is similar to results given by . And this author has similar result in the MIC of tee tree oil, His MIC from 1 to 2 mg\ml which similar to the results in our study. And support our results also which is similar to MIC for clove and cinnamon oils also and Nigla sativa oil seeds (black seed oil) has no antimicrobial activity and this is similar to results in a book by name Antibiotic resistance.
And rosemerry oil have also moderate antimicrobial effect with MIC range from 0.5 to 4 mg\ml which close to results given by Widad Jumaa that made investigation in Iraq 2015  that gave MIC range from 0.312 to 5 mg\ml. and green tee oil has very weak effect that kill only 4 isolates at 6 mg\ml and this results supported by results that gave MIC is 15.6 mg\ml that given by  and this study was made at Isfahan University.
This study presents 14 antimicrobial agents against 72 Acinetobacter clinical isolates. The activity of different agents against Acinetobacter isolates are shown in the (table 6) shows the percentage of resistant isolates at CISI breakpoints . In terms of MICs for 90% of isolates, the most active agent against Acinetobacter isolates was imipenem. Few resistant strains for imipenem  isolates 4% of the total isolates was found which was very small according to the total number 72, others have reported moderate activity like Amoxicillin-clavulanate, Whereas ampicillin, broad-spectrum penicillins, cephalosporins, aminoglycosides, and ciprofloxacin were less active. The trend towards resistance to expanded-spectrum cephalosporins was demonstrated by and seemed to be related to the presence of cephalosporinases. Recently, the presence of an extended broad-spectrum beta-lactamase was reported (Others have also found increasing resistance of Acinetobacter isolates to modern quinolones as well as to amikacin and tobramycin. Resistance to amikacin was shown to be due to the presence of aminoglycoside phosphotransferase. Excellent activity against Acinetobacter isolates was shown for imipenem, amikacin, ciprofloxacin, Amoxicillin clavulanate. Of the other beta-lactamase tested, only Ceftazidine showed moderate in vitro activity, some isolates show greater susceptibility to ciprofloxacin and aminoglycosides .
|Antibiotic||MIC (S –R )||Number of resistant isolates||Percent of resistance|
Table 6: In vitro activities of 14 antimicrobial agents against 72 of Acinetobacter isolates.
This study presents 14 antimicrobial agents against 72 Acinetobacter clinical isolates. The activity of different agents against Acinetobacter isolates shows the percentage of resistant isolates at ClSI breakpoints (2017). In terms of MICs for 90% of isolates, the most active agent against Acientobacter isolates was imipenem. Few resistant strains for imipenem  isolates of the total isolates was found which was very small according to the total number 72 and this results are in consistence with  who stated that most of his Acinetobacter isolates were susceptible to imipenem (Table 7). Also  mentioned the same result. In line with these results , who reported that 93% of his Acinetobacter isolates were susceptible to imipenem, also  reported that most of his Acinetobacter nosocomial isolates sensitive to imipenem. Coming to aminoglycoside,  stated that Acinetobacter resistant to gentamycin was 70%. Also Spence and his colleagues reported that Acinetobacter were found resistant to 4 or more aminoglycoside. On the other hand,  reported an outbreak of infections due to Acinetobacter resistant to carbapenems that occurred in a New York hospital after increased use of imipenem. The prolonged use of carbapenems for the treatment of nosocomial infections can favor the development of resistance to these antimicrobial agents. The spread of these strains within the hospital environment is a serious problem that could contribute to poor patient outcome .
|Natural oil||MIC (mg/ml)|
Table 7: MIC distribution of tested essential oils against clinical isolates of Acinetobacters (n=72).
Acinetobacter is resistant to most β-lactam antibiotics, particularly penicillins and cephalosporins, especially in ICU patients [65-68]. Ceftazidine, Piperacillin and carbapenems are among the β-lactam antibiotics most active against A. baumannii. The main mechanism of resistance to β-lactam antibiotics in Acinetobacter spp. is the production of β-lactamases encoded either by the chromosome or by plasmids . In a study from Germany in the early 1990s, imipenem was found to be the most active agent against A. baumannii. All 180 Acinetobacter spp. isolates tested were fully susceptible to imipenem. Amoxycillin-clavulanate showed moderate activity, whereas ampicillin, broad-spectrum penicillins and cephalosporins were less active. Similarly, in another report dating from 1991, 23 Acinetobacter spp. isolates were obtained from ICU patients in ten German hospitals. Ceftazidine and imipenem were the most active β-. lactam antibiotics, with 96% of the isolates remaining susceptible. Susceptibilities to Piperacillin and Cefotaxime were 65% and 61%, respectively . All 11 Acinetobacter spp. strains isolated in 1990 from patients in eight Dutch hospitals were susceptible to imipenem, and ten (91%) of the strains were susceptible to ceftazidine, ceftriaxone and amoxycillin-clavulanate . In a study from Germany in the early 1990s, imipenem was found to be the most active agent against A. baumannii. All 180 Acinetobacter spp. isolates tested were fully susceptible to imipenem. Amoxycillin-clavulanate showed moderate activity, whereas ampicillin, broad-spectrum penicillins and cephalosporins were less active. Similarly, in another report dating from 1991, 23 Acinetobacter spp. isolates were obtained from ICU patients in ten German hospitals. Ceftazidime and imipenem were the most active β-lactam antibiotics, with 96% of the isolates remaining susceptible. Susceptibilities to Piperacillin and Cefotaxime were 65% and 61%, respectively . All 11 Acinetobacter spp. strains isolated in 1990 from patients in eight Dutch hospitals were susceptible to imipenem, and ten (91%) of the strains were susceptible to ceftazidime, ceftriaxone and amoxycillin-clavulanate . Resistance of A. baumannii to the fluoroquinolones has been attributed to changes in the structure of DNA gyrase or topoisomerase IV as mutations. In Germany, 96% of Acinetobacter spp. isolates from ICU patients were susceptible to ciprofloxacin , and all 11 Acinetobacter spp. isolated in 1990 from patients of eight Dutch hospitals were susceptible to ciprofloxacin . In 1994–1995, susceptibilities to ciprofloxacin in isolates from ICU patients were 82% in Belgium, 22% in France, 25% in Portugal, 19% in Spain and 81% in Sweden [74,75]. In Belgium, 51% of the 70 Acinetobacter spp. isolates from ICU patients in 1990 were susceptible to ciprofloxacin , while 76% of the 41 Acinetobacter spp. isolated in 1997 from Belgian ICUs were susceptible to ciprofloxacin, compared with 56% of the 11 isolates in 1999 . Of the 268 A. baumannii isolated from the ICUs of 39 French teaching hospitals in 1991, were 18% were susceptible to ciprofloxacin . In Spain,  found ciprofloxacin (70%) and ofloxacin (72%) to be more active against clinical isolates of A. baumannii than norfloxacin (18%), but in a separate study, ciprofloxacin resistance in clinical isolates of Acinetobacter increased in Spain from 54.4% in 1991 to 90.4% in 1996 . Of the 279 clinical Acinetobacter spp. isolates from 20 European university hospitals participating in the 1997-1998 SENTRY study, 45.2%, 46.6% and 47.3% were susceptible to ciprofloxacin, ofloxacin and levofloxacin, respectively. Gatifloxacin and trovafloxacin showed the best in-vitro activities against Acinetobacter spp. . Quinolones showed poor activity against Acinetobacter spp. from blood cultures. Only 50.6%, 52.6% and 54.7% of the 247 isolates showed in-vitro susceptibility to ciprofloxacin, ofloxacin and levofloxacin, respectively. Similar resistance rates were seen throughout the different European centers . Of the 41 Acinetobacter spp. isolates associated with skin and soft tissue infections, 41.5%, 46.3% and 48.8% were susceptible to ciprofloxacin, ofloxacin and levofloxacin, respectively . Different publications have reported excellent activity of doxycycline or minocycline, but not tetracycline, against Acinetobacter spp. Shown in Figure 2 [67,82]. This may result from the fact that Tetra, the major tetracycline resistance determinant, confers resistance to tetracycline, but not to minocycline. In a Spanish study of the early 1990s, 98% of 54 A. baumannii isolates tested were susceptible to doxycycline . Of 109 A. baumannii isolates tested in Spain between 1997 and 1999, 85% were resistant to tetracycline .
Cinnamon oil, thyme, clove, tee tree oils have very powerful antimicrobial activity against Acinetobacter isolates so it can be used as alteranative to antibiotics which is very useful in the treatment of Acinetobacter nosocomial infections which was a very big problem in the recent years.
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Citation: Sonbol F, El- Banna T, Abd El-Aziz A, Gouda N (2017) Antimicrobial Susceptibility of Some Natural Oils against Acinetobacter Species. J Clin Chem Lab Med 1:103
Copyright: © 2017 Sonbol F, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.