Standardization of first and second-line antitubercular susceptibility testing using BacT Alert 3D system: a report from a tertiary care centre in India

Resurgence of multidrug resistant tuberculosis has lead to demand for rapid susceptibility testing. Conventional methods take > 3 weeks and are tedious. Automated methods have superseded them for first line drug susceptibility testing. An attempt was made to standardize first and second line susceptibility testing using the BacT Alert 3D system (Biomerieux). And compare results with Lowenstein Jensen's (LJ) method. 121 isolates of Mycobacterium tuberculosis, 67 pulmonary and 54 extra pulmonary were subjected to sensitivity to first and second line drugs. Multidrug resistance was detected equally by both methods at 15.7 percent. 100 percent agreement was observed between the two methods for aminoglycosides, rifampicin, ethionamide and ciprofloxacin. 91.5 percent agreement was observed for isoniazid, 85 percent for pyrazinamide and 72.4 percent for ethambutol. The time taken by LJ method was 18-32 days and BacT Alert 3D system took 4-12 days. In the lesser developed nations where tuberculosis is rampant a rapid effective method for confirming multidrug resistant tuberculosis is definitely desirable and the BacT Alert 3D system was found an effective method when compared to the 'gold standard' LJ proportion.

In vitro evaluation of a new cefixime-clavulanic acid combination for gram-negative bacteria.

The study was conducted to evaluate a new cefixime-clavulanic acid combination for in vitro susceptibility towards gram-negative bacteria. A total of 220 isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeroginosa, Acinetobacter spp, Salmonella enterica serovar Typhi and Salmonella enterica serovar Typhimurium were included in the study. The isolates were tested for susceptibility towards the new combination antimicrobial molecule cefixime with clavulanic acid by disk diffusion and Epsilometer strip (E-strip) Minimum Inhibitary Concentration (MIC) method. Of the 101 E. coli and K. pneumoniae isolates, 62.4% were found to be extended spectrum beta-lactamase (ESBL) producers. Almost half of these were from the community and 55.6% were hospital isolates. Of the ESBL isolates, 19% were AmpC (cephalosporinases that are poorly inhibited by beta lactamase inhibitor) producers while the remaining 81% were non AmpC ESBL producers. The AmpC producers were resistant to both cefixime and the combination, while the non-AmpC producers were sensitive to the combination. The addition of clavulanate to cefixime did not improve the sensitivities of P. aeruginosa and Acinetobacter isolates. There were no ESBL isolates among the S. Typhi isolates, all of which were sensitive to cefixime. Of the S. Typhimurium, 88.9% were ESBL producers and all of these were resistant to cefixime but sensitive to the combination. The combination of cefixime with clavulanic acid offers the advantage of oral administration and appears to be a viable option for the treatment of uncomplicated community acquired infections caused by non-AmpC ESBL producing gram-negative bacteria.

Microflora of bile aspirates in patients with acute cholecystitis With or without cholelithiasis: a tropical experience

The current study determined the spectrum of biliary microflora with special emphasis on enteric fever organisms in patients with acute cholangitis with and without cholelithiasis or other biliary diseases. The patients were divided into three groups: Group A consisted of patients with acute cholecystitis with cholelithiasis; Group B consisted of patients with acute cholecystitis with gastrointestinal ailments requiring biliary drainage and group C consisted of patients with gallbladder carcinoma. Gallbladder, bile and gallstones were subjected to complete microbiological and histopathological examination. Antimicrobial susceptibility of the isolates was performed as per CLSI guidelines. Bacteria were recovered from 17 samples (32 percent) in Group A, 17 (51.4 percent) in Group B and 1 (1.6 percent) in Group C. The most common organisms isolated were Escherichia coli (11, 29.7 percent), Klebsiella pneumoniae (10, 27 percent), Citrobacter freundii (3, 8.1 percent), Salmonella enterica serovar Typhi (3, 8.1 percent), etc. The majority of Enterobacteriaceae isolates were susceptible to piperacillin-tazobactam and meropenem. As regards Salmonella spp., S. Typhi was isolated from 2 (3.8 percent) patients in Group A and 1 (16 percent) in Group C. Antimicrobial susceptibility of potential causative organisms, the severity of the cholecystitis, and the local susceptibility pattern must be taken into consideration when prescribing drugs. A protocol regarding the management of such cases should be formulated based on observations of similar studies.

Salmonella enterica serovar typhi: molecular analysis of strains with decreased susceptibility and resistant to ciprofloxacin in india from 2001-2003

Chromosomally-mediated reduced susceptibility to ciprofloxacin narrows the therapeutic options in enteric fever. We made a molecular comparison of clinical isolates of fluoroquinolone-resistant strains of Salmonella enterica serotype Typhi from January 2001 to May 2003; 178 isolates were subjected to antimicrobial susceptibility testing by the Kirby-Bauer method of disk diffusion, and agar dilution was used to determine the minimum inhibitory concentration (MIC) to ciprofloxacin. Nalidixic-acid resistant strains (NARST) were observed in 51 percent of the isolates, of which 98.9 percent had decreased susceptibility (MIC>0.125-1mug/mL) to ciprofloxacin. A single strain (4 mug/mL) was resistant to ciprofloxacin and double mutations were found in the gyrA gene (76 Asp->Asn, 44 leu->Ileu). Among seven NARST strains with reduced susceptibility, a single mutation was found in five strains, one of which had 76 Asp->Asn and two each had mutations at 87 Asp->Asn and 72 Phe->Tyr, respectively); no mutations could be detected in two isolates. Routine antimicrobial surveillance, coupled with molecular analysis of fluoroquinolone resistance, is crucial for revision of enteric fever therapeutics.

Typhoid fever: narrowing therapeutic options in India.

Typhoid fever remains an important public health problem in India. One thousand four hundred fifty-eight blood cultures were screened, 178 grew out Salmonella enterica serovar Typhi. On agar dilution minimum inhibitory concentration (MIC) testing, 0.6% of the isolates were resistant to ciprofloxacin, 2% to cefotaxime and 1% to cefepime. Nalidixic acid resistance was observed in 51% isolates, of which 98.9% had decreased susceptibility (MIC > or = 0.125-4 microg/ml) to ciprofloxacin. One strain of nalidixic acid sensitive S. Typhi (NASST) also had a decreased MIC (0.125 microg/ml) to ciprofloxacin. Resistance to third and fourth generation cephalosporins is emerging in India and will gain significance in the coming decade. The molecular basis of resistance to cephalosporinsand ciprofloxacin resistance in NASST strains need to be further evaluated for S. Typhi.

Rapid diagnosis of community-acquired pneumonia using the Bac T/ alert 3D system

We compared BacT/Alert 3D with conventional culture for the diagnosis of community-acquired pneumonia (CAP). Antimicrobial susceptibility testing of the isolates was performed with the disk diffusion method, and the minimum inhibitory concentration (MIC) was calculated. Automation was superior in terms of recovery and time to detect pathogens. The bacterial spectrum in CAP was Streptococcus pneumoniae (35.3 percent) Staphylococcus aureus (23.5 percent), Klebsiella pneumoniae (20.5 percent) and Haemophilus influenzae (8.8 percent). Three of the 12 S. pneumoniae isolates showed penicillin resistance on MIC and two showed erythromycin resistance. There were two H. influenzae strains resistant to penicillin; these were beta lactamase producers. One-fourth of the S. aureus were oxacillin resistant. All isolates were sensitive to cefepime by disc diffusion and MIC methods. In the treatment of CAP, cefotaxime and cefepime are useful drugs when given as empirical therapy against multidrug resistant strains. The use of automation is vital in CAP, as rapid diagnosis and effective therapy can reduce mortality.