This is a prospective observational study done over a period of one year from 2018 March to 2019 April. The study was conducted at the department of Microbiology, Rajarajeswari medical college.

A total of 400 Gram negative bacilli isolated from various clinical specimens were included. Among them 134 isolates were from pus samples, 16 from Ear swab,10 from vaginal swab, 02 from pleural fluid,92from sputum, 26 from blood and from 120 urine samples. Distribution of various clinical specimens are as shown in (Table 1)

The organisms isolated are Klebsiella spp. 133 (33.25%), Escherichia coli 118 (29.5%), Pseudomonas spp 109(27.25%), Enterobacter spp 25 (6.25%), Citrobacter spp 5 (1.25%), and Acinetobacter spp 10 (2.5%). Isolates from various clinical specimens are as shown in (Table 2)

Pseudomonas was isolated frequently from pus samples of burn wounds, ear swabs, Enterobacter from blood while Klebsiella spp from pus and respiratory tract, Escherichia coli from urine specimens. Distribution of various isolates in different clinical samples are as shown in (Table 3)

The susceptibility pattern of various isolates are shown in Table 4. All isolates showed good susceptibility to ciprofloxacin except Acinetobacter spp which was sensitive to cefepime.

Among 400 isolates, 34 isolates were ESBL producers and 18 isolates were AmpC producers out of which 15(44%) ESBL and 7(38%) of AmpC producers were ciprofloxacin susceptible.

Resistance to third and fourth generation cephalosporins along against nosocomial gram negative bacteria poses a great threat to clinical outcome of the patients. 14 This could be because of unwarrented use of such antimicrobial agents both in the hospital settings also by itself prescribing practices of patients. Thus, changes in antimicrobial drug–prescribing patterns through formulary modification and continuous education of prescribers along with good infection control practices helps to combat this resistance. 15 Such resistance patterns always pushes a need for reevaluation of the susceptibility testing.

In a study done by Archibald L, et al in united states, Enterobacter cloacae showed 40% resistance to ceftazidime. In our study all Entrobacter spp (100) were resistant to ceftazidime (Table 4). This is probably related to production of stably derepressed chromosomal class-1 β-lactamase, which hydrolyzes β-lactam antibiotics other than carbapenems. Studies done by Verbist L.et al an JarlierV showed that lowest resistance to ciprofloxacin. Similarly In our study 64% of Enterobacter spp. was sensitive to ciprofloxacin. 16, 17 In our study Klebsiellaspp showed 22% sensitivity to ceftazidime. Similar results were seen in studies done by Livermore DM et al and Philippon A et al, where Klebsiella pneumoniae showed 36% and 26% of susceptibility to ceftazidime respectivily. This could be because of the production of extended-spectrum β-lactamases. 18, 19 Reports show that there is a substantial increase in resistance from 3.6% in 1990 to 14.4% in 1993 to ceftazidime among K pneumoniae in ICU isolates increased. 20

In our study Gram negative bacilli susceptibility ranged from 25-60% to cefepime and 29-80% for ciprofloxacin. Thus ciprofloxacin was more effective compared to cefepime. A worrisome trend during the last two decades has been the development of resistance to extended-spectrum cephalosporins, e.g., cefotaxime, ceftazidime, and ceftriaxone. Such resistance is most often due to the breakdown of the extended-spectrum cephalosporin by extended-spectrum β-lactamases (ESBLs), but it may also be due to plasmid-mediated or chromosomally hyperproduced Amp C. 21 Thus detection of ESβL- and AmpC beta lactum producing strains plays a pivotal role to prevent uncontrolled spread and also therapeutic failures.  Early detection of the resistance patterns helps to formulate appropriate usage of antibiotics and helps in the effective implementation of containment measures. In our study 44% isolates were ESBL producers and 38% were AmpC producers. Though molecular methods are the gold standard for the detection of ESBL nad Amp C producers, because of unavailability of facilities at all centres in developing countries,various phenotypic methods are recommended for routine use to detect ESβL production in Gram-negative bacilli. 22

In our study 20-80% of the isolates were susceptible to ciprofloxacin when compared to other class of antibiotics, especially third and fourth generation cephalosporins. Even among ESBL and Amp C produces high susceptibility was seen to ciprofloxacin. As there is growing resistance to third and fourth generation cephalosporins, it is a prerequisite to reevaluate the susceptibility of these isolates.Kaye et al.reported a protective effect of fluoroquinolone use against the emergence of resistance to third-generation cephalosporins in nosocomial isolates of Enterobacter. ²³ Though our study does not generalize the use of fluroquinolones over cephalosporins, similar to Kaye et al. study, our study suggests that substitution of fluroquinolones for certain types of β-lactam antimicrobial drugs could be considered. The potential advantages of adding fluoroquinolones over third-generation cephalosporin resistance are: they can be administered orally; they are relatively nontoxic and inexpensive. 24

In summary, there is a decrease in the percentage of antibiotic susceptibility across all isolates to cefuroxime, cefotaxime and ceftazidime. The most of the isolates were susceptible to cefepime and ciprofloxacin. Among them ciprofloxacin was more effective than cefepime among all tested organisms except the Acinetobacter spp in which cefepime was more effective. So considering the cost and adverse effects of cephalosporins, we suggest the use of ciprofloxacin, as first line of drug.