Antimicrobial resistance of bacterial pathogens in a Neonatal Intensive Care Unit

The aim of this study was to identify the antimicrobial susceptibility pattern and relevant treatment options in a neonatal intensive care unit from January 2012 and June 2016. Out of the total 78 culture positive samples, Gram positive and Gram negative microorganisms were 26% and 74% respectively. Acinetobacter remained the predominant isolate (32.1%) followed by Klebsiella species (18.0%). Most of the Gram positive isolates exhibited higher resistance to penicillin, cephalosporin, macrolides, gentamycin and quinolones. Gram positive isolates had sensitivity of 100% to linezolid, vancomycin, chloramphenicol followed by rifampicin (84%). In comparison to other commonly used antibiotics, sensitivity to these four medicines was statistically significant (p<0.05). Similarly, most of the Gram negative bacteria showed resistance to cephalosporin, aminoglycosides. About two-third cases showed resistant to meropenum, quinolones and combination preparation of piperacillin and tazobactam. Overall sensitivity among the Gram negative isolates was to polymixin B (100%) and minocycline (97%), followed by colistin (83%). In comparison to other commonly used antibiotics, sensitivity to these three medicines was statistically significant (p<0.05).


Introduction
With the improvement of health care facilities and development of public awareness, neonatal mortality rate decreased significantly in Bangladesh from 36.8/1,000 live birth in year 2004 to 20/1,000 live birth in year 2015. 1 However, neonatal sepsis is, still, responsible for 30-50% of total neonatal deaths each year. 2 Globally, around 20% of neonates suffer from sepsis. 3 Since the aim of empirical therapy is to target the infectious microorganism(s), it is essential for every neonatal unit to survey the profile of causative microorganism and their susceptibility in order to ensure effective antimicrobial treatment. 3,4  pathogens causing neonatal sepsis varies overtime and places.

Results
Out of these 78 bacterial isolates, 74% were Gram negative microorganisms, 26% were Gram positive microorganisms.
Table I shows overall sensitivity pattern of Gram positive microorganisms.Most of the Gram positive isolates exhibited higher resistance to penicillin, cephalosporin, macrolides, gentamicin and quinolones.Susceptibility to commonly used was found to vancomycin (100%), chloramphenicol (100%), rifampicin (84%) and linezolid (100%).In comparison to other commonly used antibiotics, sensitivity to these four medicines was statistically significant (p<0.05).
Table II showing overall sensitivity pattern of Gram negative organism, Acinetobacter spp.(32.1%) are the commonest microorganisms responsible for infection in neonate followed by Klebsiella species (n=14, 18.0%).Most of the Gram negative bacteria showed resistance to cephalosporin, aminoglycosides; about two-third showed resistant to meropenem, quinolones and combination preparation of piperacillin and tazobactam.Best overall sensitivity among Gram negative isolates was to polymixin B (100%) and minocycline (97%), followed by colistin (83%).In comparison to other commonly used antibiotics, sensitivity to these three medicines was statistically significant (p<0.05).Surprisingly, sensitivity pattern for Acinetobacter spp.have not been changed significantly over the last four and half years (Figure 1).

Discussion
In the present study, Gram negative organisms were responsible for majority cases of neonatal sepsis about 74% and only 26% septic cases were by  We found coagulase negative Staphylococcus were 100% sensitive to linezolid, vancomycin and chloramphenicol.
The present study shows that most of the Gram negative organisms were resistant to commonly used antibiotics like aminoglycosides and cephalosporin.About two-third cases showed resistant to meropenem, quinolones and combination preparation of piperacillin and tazobactam.][24] According to Pitout et al. (1998) 25 Gram negative organisms can produce extended spectrum betalactamases which is responsible for this multidrug resistance pattern. 25 this study, among the Gram negative isolates, maximum sensitivity was observed to polymixin B (100%) and minocycline (97%), followed by colistin (83%).In comparison to other commonly used antibiotics, sensitivity to these three medicines was statistically significant (p<0.05).Mustafa and Ahmed (2014) reported higher sensitivity to imipenem and linezolid which were statistically significant (p<0.05),but they recommended not to use these medicines indiscriminately to prevent resistance to these drugs may develop. 26though multidrug resistance is a burning issue now-a-day and its severity is increasing day by day. 26Surprisingly, in this study it was found that antibiotic sensitivity pattern for Acinetobacter spp.
have not been changed significantly over the last four and half years.

Conclusion
Gram negative organisms specially Acinetobacter and Klebsiella were commonly responsible for the neonatal sepsis.Organisms were resistant to most of the commonly used antibiotics.Gram negative organisms were commonly sensitive to polymixin B, minocycline and colistin.Gram positive organisms were commonly sensitive to vancomycin, chloramphenicol, rifampicin and linezolid.

Figure 1 :P
Figure 1: Percentage of antibiotic sensitivity pattern for Acinetibacter spp.over four and half years

3, 4
Group B Streptococcus and E. coli still contribute to 70-75% of cases of neonatal septicemia in the North America and Europe.

4, 5
Whereas, Gram negative microorganisms remain the major cause of neonatal sepsis, particularly early onset sepsis in most of the developing countries.

Table II Antibiotic sensitivity pattern for Gram negative microorganisms (n=58)
Sharma et al. (2013) 21 and Shah et al. (2012) 22 reported coagulase negative Staphylococcus mainly responsible for neonatal sepsis and were sensitive to vancomycin only. 20-22 20am positive organisms.A recent study conducted byMuley et al. (2015)16in India reported 70.8% neonatal septicemia cases caused by Gram negative isolates.Almost similar results were reported byPooja et al. (2015)where Gram negative and Gram positive organisms were isolated in 79.9% and 18.2% cases respectively.17Karlowiczetal.(2000)reported that Gram positive organisms caused 73% of bacterial sepsis but highest mortality rate was observed in Gram negative septic cases.18Geographicalvariationsareobservedamong the pathogens causing neonatal sepsis.Recently, Gram negative organisms like Acinetobacter, Klebsiella, Escherichia coli and Pseudomonas are commonly isolated.19OftheGrampositive organisms, Staphylococcus aureus, coagulase negative Staphylococcus, Streptococcus pneumonia and S. pyogenes are most commonly isolated.20Inthis study, we found Acinetobacter remained the predominant isolate (32.1%) followed by Klebsiella species (18.0%) implycated in neonatal sepsis.