ABSTRACT

CORRESPONDING AUTHOR:
Dr. Sana Islahi,
HIG-72, Sector-E,
Aliganj, Lucknow,
U. P, India.
E-mail: islahi.sana@gmail.com

ABSTRACT: BACKGROUND: Acinetobacter species are one of the most frequent nosocomial pathogen causing bacteremia, urinary tract infection, secondary meningitis, skin and soft tissue infections and in particular nosocomial pneumonia with high mortality rate. The infections due to these are often difficult to treat due to their high antibiotic resistance. AIMS: To Study the prevalence and resistance pattern of Acinetobacter species in hospitalized patients of Era’s Lucknow Medical College and Hospital (ELMCH), Lucknow. MATERIALS AND METHODS: Total number of 1850 samples were taken from patients admitted in wards of different Departments of ELMCH from Sep 2012 to Sep 2013. Identification of isolates was done by colony characteristics and biochemical reactions. The resistance patterns of these isolates were studied using various antibiotics by Kirby-Bauer disc diffusion test as per CLSI (Clinical Laboratory Standard Institute) guidelines. RESULTS AND CONCLUSION: 46 isolates were identified as Acinetobacter species. High level of resistance was observed for most of the antibiotics tested. More than 80% of isolates were resistant to amikacin, gentamycin, ceftriaxone, ciprofloxacin and tetracycline. 30.43% of isolates were resistant to cefoperazone/sulbactum and resistance to imipenem and colistin was 23.91% and 19.56% respectively. Acinetobacter species has become a worldwide concern as a cause of serious nosocomial infections. The emergence of increasingly resistant strains causing such infections has become a public health problem. Their early detection is necessary for timely implementation of strict infection control practices and judicious treatment with susceptible antimicrobials.

KEYWORDS: Acinetobacter, prevalence, resistance pattern.

INTRODUCTION: Acinetobacter baumannii is an opportunistic nosocomial pathogen and one of the six most important multidrug-resistant microorganisms in hospitals worldwide. This human pathogen is responsible for a vast array of infections, of which ventilator-associated pneumonia and bloodstream infections are the most common, and mortality rates can reach 35%.¹

Acinetobacter species are ubiquitous aerobic gram negative coccobacilli, emerging as an inevitable potential pathogen to establish its survival in the host environment and among debilitated patients by producing various extracellular virulence factors.² In recent years, Acinetobacter baumanni has become a worldwide concern as a cause of serious nosocomial infections. The majority of clinical isolates involved in the hospital outbreaks belongs to this species.³

                There is increasing incidence of Acinetobacter infections in hospital intensive care units. It is often acquired by cross infection, but can be introduced initially by patients admitted from other hospitals⁴. In a study in the Department of Clinical Microbiology, King Edward Memorial Hospital, India, total 510 of 5391 (9.6%) of isolates were Acinetobacter, responsible for 71.2% (363 of 510) monomicrobial and 28.8% (147 of 510) polymicrobial infections.⁴ The prevalence of these infections currently ranges from 2% to 10% of all gram negative bacterial infections in Europe⁵ and about 2.5% in United States,⁶ causing both sporadic as well as epidemic infections.

Acinetobacter is a group of organism that is ubiquitous, widely distributed in nature eg. soil, water, sewage, food and animals⁷. It is the only group of Gram negative bacteria that may be natural resident of skin, with 42.5% in healthy individuals and as high as 75% in hospitalized patients.⁷

 Acinetobacter baumannii is the most common species of Acinetobacter causing infections in humans. Acinetobacter is commonly found in hospital environment and it can be transmitted to the patients via hospital personnel and contaminated instruments or devices.

 Clinical isolates of Acinetobacter species initially retained at least partial susceptibility against the 3^rd and 4^th generations viz cephalosporins, fluoroquinolones, semisynthetic aminoglycosides, carbapenems and 100% susceptibility to imipenem. However, during late 1980 and 1990s, worldwide emergence and spread of Acinetobacter strains resistant to imipenem further limited therapeutic alternatives.^8,9

 Rational use of antimicrobial agents is critically important to prevent Acinetobacter infections as well as to avoid poor outcomes.¹⁰

Therefore early detection of such organisms is necessary for timely implementation of strict infection control practices and treatment with alternative antimicrobials.

MATERIALS AND METHODS: This cross sectional study included 1850 samples taken from patients admitted in various department of the hospital including all surgical wards, orthopedic ward, medicine wards, obstetrics and gynecology ward, pediatric ward and intensive care units of Era’s Lucknow Medical College & Hospital (ELMCH), Lucknow, Uttar Pradesh, India during September 2012- September 2013. The specimens included respiratory secretions, swab (wound, conjuctive, skin), pus, urine, blood culture, bile culture, cerebro-spinal fluids, body fluids, drain fluids, endotracheal aspirate (ETA) and catheter tips.

 The specimens were collected under aseptic conditions were inoculated on MacConkey agar & Blood agar. The plates were incubated aerobically at 37⁰C for 24-48 hrs. Presumptive identification was done on the basis of colony characteristics, Gram staining, catalase test, oxidase test, nitrate reduction test, oxidative/fermentative test.

All these species of Acinetobacter were then screened for antibiotic sensitivity by Kirby- Bauer disk-diffusion method on Muller Hinton Agar according to CLSI (Clinical Laboratory Standard Institute) guidelines (2013).

Clinical details of all patients whose cultures were positive for Acinetobacter species was collected as given below:

1. Patients admitted in the medical and surgical wards and ICU was enrolled in this study.
2. Information regarding patient’s age, sex and clinical diagnosis of disease was noted.
3. Clinical details at the time of admission of the patient was noted.
4. History of antibiotic intake was noted.
5. Informed consent was taken from each patient.

RESULTS:

Table 1 Shows that Out of 1850 samples collected 1090 (58.92%) came to be culture positive. Of the 1090 culture positive specimens 46 (4.22%) grew Acinetobacter species. Maximum number were from pus sample 17 (36.95%) followed by blood 11 (23.91%) and urine 7 (15.21%).

Table 2 Shows Acinetobacter isolates according to wards and ICU from where they were isolated. Highest percentage of Acinetobacter were from ICU (26.09%) followed by pediatric ward (21.73%) followed by surgery ward (19.56%).

Table 3 Shows age wise distribution of Acinetobacter species, having maximum infection in the age group of 1-15 years.

Table 4 shows that infection with Acinetobacter species is more in males (76.08%) than in females (23.91%).

Figures within parenthesis indicate percentage.

Table 5 Shows the antibiotic susceptibility pattern of Acinetobacter strains (n=46) for different antibiotics. >80% of isolates were resistant to amikacin, gentamycin, ceftriaxone, ciprofloxacin and tetracycline. 30.43% of isolates were resistant to cefoperazone/sulbactum and resistant to impenem and colistin was 23.91% and 19.56% respectively.

DISCUSSION: Until 1970, Acinetobacter spp. were considered rare cause of nosocomial infections but in recent years, the incidence of nosocomial infections has reached a point of concern and possess a threat to hospitalized populations around the world.^{11, 12, 13} Acinetobacter species has emerged as an important nosocomial pathogen that is often multidrug resistant and associated with life-threatening infections.¹⁴

Multidrug resistant (MDR) Acinetobacter is of great concern because of its intrinsic and acquired resistance mechanisms, limiting the treatment options.¹⁵ Carbapenems are the drug of choice for Acinetobacter infections and are often used as last resort.¹⁶

In the present study, we have demonstrated the prevalence of Acinetobacter species and its antibiotic susceptibility pattern in a tertiary care setup. In this study of 1090 culture positive samples from indoor patients, Acinetobacter was isolated in 46 (4.22%) samples while in the study of Sakata et al ¹⁷ the incidence of Acinetobacter was 15.52%. In India study by Oberoi et al¹⁸ and Sinha et al¹⁹ in tertiary care hospital incidence of Acinetobacter was 8.4% and 4.8% respectively indicating importance as nosocomial pathogen.

In the present study maximum number of Acinetobacter isolates were from pus 36.95% (17/46) followed by blood 23.91% (11) and urine 15.21% (7). Almost similar result was observed in a study by Mishra et al.²⁰ While in a study by Sinha et al¹⁹ and Padersen et al²¹ maximum number of Acinetobacter were isolated from urine.

In the present study highest number of isolates were from ICU 12/46 (26.09%). From this ward, in one patient, Acinetobacter was grown in repeated cultures from different samples of same patient. Acinetobacter baumanni, a clinically important species, has a tendency towards cross-transmission, particularly in ICUs where numerous outbreaks are encountered.¹⁴

In this study there was higher incidence of Acinetobacter infection among males 76.08% (35/46) which is in tandem with other studies in India.^{19, 22} It is widely recognized that in many Asian communities, lower incidence in women is statistical artifact related to lower reporting to hospital and care seeking for women from traditional practitioners who do not report to public surveillance system.

Susceptibility of Acinetobacter against various antimicrobials being considerably different among countries, centres and even different wards of the same hospital, therefore, warranted need for local surveillance studies in deciding the most appropriate therapy.²²

Resistance pattern of Acinetobacter revealed that more than 80% of isolates were resistant to third generation cephalosporins, aminoglycosides and quinolones, indicating high prevalence of multidrug resistance. Thirty percent of these isolates were resistant to cefoperazone/sulbactum. However, another study^{22, 23} showed 46% resistance to cefoperazone/sulbactum.

In this study 80% of Acinetobacter were found to be sensitive to colistin but other study by Lopez-Hernandez etal²⁴ found 100% susceptibility of Acinetobacter to colistin. Colistin is relatively more sensitive than carbapenems for MDR Acinetobacter as it is newly used drug for MDR Acinetobacter in our setting.

CONCLUSION: After analyzing the findings of the present study it was concluded that Acinetobacter isolates constitute only 4.22% of all the culture positive specimens. Maximum percentage of Acinetobacter were from pus samples 17/46 followed by blood. Urine in spite of maximum in sample input, the isolation of Acinetobacter is quite low. Maximum number of Acinetobacter isolates were from ICU (26.09%) followed by pediatric ward (21.73%). It can be concluded from the study that Acinetobacter occurs as colonizer and contaminant in clinical samples of hospitalized patients.

Amikacin and ceftriaxone were the most common used antibiotics in patients. Acinetobacter infection were more common in male patients. No significant difference is seen in distribution of Acinetobacter isolates in different age groups. Acinetobacter isolates from clinical samples were showing high level of resistance to all groups of antibiotics viz 84.78% to amikacin, 86.95% to gentamycin, 89.13% to ceftriaxone and 86.43% to ciprofloxacin. Most Acinetobacter isolates were found to be MDR strain i.e. resistant to more than or equal to 3 antibiotics.

It can be concluded from this study that overall incidence of Acinetobacter as nosocomial pathogen in our setup is low but predominantly multidrug resistant. The increasing trends towards resistance towards antibiotic resistance reflects the extensive usage of antibiotics in hospitals which in turn exerts selective pressure on Acinetobacter in hospital environment.

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