Anti-Microbial Susceptibility Patterns of Enterobacteriaceae Isolated From A Tertiary Care Unit In Gujarat
J Patel, J Bhatt, V Javiya, K Patel
antimicrobial susceptibility, carbapenem sensitivity, combination antibiotics, disk diffusion technique, enterobacteriaceae
J Patel, J Bhatt, V Javiya, K Patel. Anti-Microbial Susceptibility Patterns of Enterobacteriaceae Isolated From A Tertiary Care Unit In Gujarat. The Internet Journal of Microbiology. 2008 Volume 6 Number 1.
The development of antibiotic resistance can be viewed as a global problem in microbial genetic ecology. It is a very complex problem to contemplate, let alone solve, due to the geographic scale, the variety of environmental factors, and the enormous number and diversity of microbial participants. Extended spectrum β-lactamases (ESbLs) continue to be a major problem in clinical setups worldwide, conferring resistance against extended spectrum cephalosporins. Increasing resistance to third and fourth generation cephalosporins has become a cause of concern especially amongst
Bacterial infection is the most common cause for hospital visits. In almost all cases of nosocomial infection, there is a need to start treatment before the final microbiological results are available. Area-specific monitoring studies aimed to gain knowledge about the type of pathogens responsible for specific infection and their resistance patterns may help the clinicians to choose the correct empirical treatment. Hence, this study was undertaken to find out the antibiotic susceptibility pattern of the isolated pathogenic
Materials and methods
Our study group comprised of patients who were clinical suspects of bacterial infection or who had undergone various surgical procedures. Project was undertaken at Rajasthan Hospitals, Ahmedabad, Gujarat, India. A protocol was designed and all the information pertaining to the patient's name, age, sex and culture susceptibility etc. were recorded on individual basis. Collected specimen comprised of urine, pus, sputum, endotracheal secretion (ET), blood, bile, broncho-alveolar lavage (BAL), semen, body tissues and various body fluids. All the samples were collected by standard procedures in aseptic closed containers and extensive care was taken to avoid contamination such as in case of urine sample, standard “clean-catch” method was adopted. Specimen was sent to laboratory as early as possible. If there was a delay of more that two hours, it was refrigerated except in suspected cases of infection with
Results were interpreted as sensitive (S), intermediate resistant (I) or resistant (R) based on CLSI guidelines ( 6 ). The category “susceptible” was defined as identification of a strain as susceptible by the disk diffusion method. Quality control strain of
572 samples were studied, out of which, 276 (48.35%) were culture positive samples. From this culture positive samples, 154 samples (55.80%) were from patients infected with
Urine (44.16%) was the specimen source for majority of isolates, followed by pus (22.73%) and sputum (15.58%) (Figure 2).
Frequency of isolation of pathogenic organisms from various specimens is depicted in Table–1. It can be observed that with urine as the specimen source, highest infective organism isolated was
All antibiotics used in the present study as monotherapy, did not demonstrate statistically significant susceptibility patterns (P>0.05) with the exception of imipenem and meropenem. Although aztreonam has been reported to have strong activity against gram-negative bacteria, the study revealed high levels of resistance (30% to 100%). Table 2 and figures 3-7 show the overall results of susceptibility pattern of
We observed that
All enterobacter species (n=10) isolates were 100% susceptible to imipenem and meropenem. While susceptibility rates to amikacin, netilmycin and gatifloxacin were 60%, 60% and 80% respectively. Susceptibility to cephalosporin was only 20% due to ESbLs production in 80% specimens. However, enterobacter sp. were 100% susceptible to cephalosporins-sulbactum combinations (p<0.001). (Figure 5)
M. morganii and P. vulgaris
Out of 154 cultures positive specimen isolates, 44.16% (68 specimens) were urine samples indicating that urinary tract infection (UTI) is the most common hospital acquired infection. A high isolation rate of pathogens from urine samples of clinically suspected UTI show a good correlation between clinical findings and microbiological methods. UTI is one of the most important causes of morbidity in general population and is the second most common cause of hospital visits.
It should be noted that, at least 66.89% of samples in the current study were from clinically significant sources (urinary tract and pus). On the other hand, 21.42% of the samples were from the respiratory tract. The frequency and percentage of specimen distribution in our study closely reflects the prevalence of gram negative bacteria in similar settings reported elsewhere ( 12,13,14 ).
Penicillin group of antibiotics are drugs of choice for a wide variety of infectious diseases. Unfortunately these drugs are readily hydrolyzed by broad spectrum β-lactamases that are found with increasing frequency in clinical isolates of these gram negative bacteria. Many reports in the literature suggest an increased resistance to ampicillin (80-100%). A study from western Nepal reported high prevalence of resistance to ampicillin, nalidixic acid and norfloxacin ( 12 , 13 ). However, concurrent administration of a β-lactamase inhibitor such as clavulanate or sulbactum markedly expands the spectrum of activity of these drugs. The susceptibility of all gram negative bacteria significantly increased and ranged from 50% to 80% (Table 2 and Figures 3-7). Thus it is evident that β-lactamase producing gram negative organisms are resistant to monotherapy of penicillin.
Our results with cephalosporins are in corroboration with the one reported by other workers ( 14,15,16,17 ) that the overall resistance to various generations of Cephalosporins was high on account of the production of ESbLs by the bacteria involved. Hence, addition of sulbactum to cefoperazone, cefotaxime and ceftraixone monotherapy significantly reduced the percentage resistance and increased the percentage susceptibility against all the organisms (Table 2 and Figure 3-7). Carbapenems, the antibiotics class resistant to most of the β-lactamases, have a broader spectrum of activity then do other β-lactam antibiotics. It is resistant to hydrolysis by most β-lactamases. Activity is excellent against Enterobacteriaceae including organisms resistant to cephalosporins by virtue of expression of chromosomal or plasmid extended spectrum β-lactamases. Most of the strains of Pseudomonas and Acinetobacter are inhibited by carbapenems. Hence, it would be prudent to use imipenem or meropenem for empirical treatment of serious infections in hospitalized patients.
Aztreonam binds the penicillin-binding proteins of gram-positive and anaerobic bacteria very poorly and is largely ineffective against them. It is known to be effective against a wide range of gram-negative bacteria, however in the present study all organisms were resistant to aztreonam, with
From present investigation, we can say that there are increasing instances where the resistance to antimicrobials acquired by previously susceptible organisms is the cause of treatment failure, or requires administration of larger doses or more expensive and toxic agents. Irrational and inappropriate use of antibiotics has been a major cause in development of drug resistance. Therapeutic decisions in infections involve consideration of susceptibility-resistance patterns, pharmacokinetic profile, prophylactic/combined antibiotic therapy, host-defense mechanisms, local factors and adverse reactions of the drug etc. There is a need to emphasize the rational use of antimicrobials and strictly adhere to the concept of “reserve drugs” to minimize the misuse of available antimicrobials. In addition, regular antimicrobial susceptibility surveillance is essential for area wise monitoring of the resistance patterns. An effective national and state level antibiotic policy and draft guidelines should be introduced to preserve antibiotic effectiveness, and for better patient management. Industry and government should boost basic research for identifying new and effective molecules to combat the resistant micro-organisms. Physicians and pharmacists should avoid the misuse of potent molecules and reserve such molecules for severely resistant cases only.
Based on our observations of the present study we recommend use of antimicrobials like ampicillin, amoxicillin and third generation cephalosporins (cefoperazone, cefotaxime and ceftriaxone) in combination with α-Lactamase inhibitors (clavulanate or sulbactum) for the treatment of
The authors wish to thank Dr. Mitesh Patel, M.D. (Microbiology) Assistant Professor, B.J. Medical College and Civil Hospital, Ahmedabad, India and Dr. Atit Shah, M.D. (Microbiology), Assistant Professor, Smt. NHL Municipal Medical College and V. S. Hospital, Ahmedabad, India for extending their help and guidance in conducting the microbiological analysis for the present study.