Extended-spectrum β-lactamases (ESBLs) are a group of plasmid-mediated, diverse, complex and rapidly evolving enzymes that are posing a major therapeutic challenge today in the treatment of hospitalized and community-based patients. Infections due to ESBL producers range from uncomplicated urinary tract infections to life-threatening sepsis. Derived from the older TEM is derived from Temoniera, a patient from whom the strain was first isolated in Greece. β-lactamases, these enzymes share the ability to hydrolyze third-generation cephalosporins and aztreonam and yet are inhibited by clavulanic acid. In addition, ESBL-producing organisms exhibit co-resistance to many other classes of antibiotics, resulting in limitation of therapeutic option. Because of inoculum effect and substrate specificity, their detection is also a major challenge. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in Klebsiella pneumoniae, K. oxytoca, Escherichia coli and Proteus mirabilis. In common to all ESBL-detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic-resistance mechanisms in the face of the introduction of new antimicrobial agents. Thus there is need for efficient infection-control practices for containment of outbreaks; and intervention strategies, e.g., antibiotic rotation to reduce further selection and spread of these increasingly resistant pathogens.

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%) in Group A, 17 (51.4%) in Group B and 1 (1.6%) in Group C. The most common organisms isolated were Escherichia coli (11, 29.7%), Klebsiella pneumoniae (10, 27%), Citrobacter freundii (3, 8.1%), Salmonella enterica serovar Typhi (3, 8.1%), 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%) patients in Group A and 1 (16%) 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.

Enteric fever is a major public health problem in developing countries. Ciprofloxacin resistance has now become a norm in the Indian subcontinent. Novel molecular substitutions may become frequent in future owing to selective pressures exerted by the irrational use of ciprofloxacin in human and veterinary therapeutics, in a population endemic with nalidixic acid-resistant strains. The therapeutics of ciprofloxacin-resistant enteric fever narrows down to third- and fourth-generation cephalosporins, azithromycin, tigecycline and penems. The first-line antimicrobials ampicillin, chloramphenicol and co-trimoxazole need to be rolled back. Antimicrobial surveillance coupled with molecular analysis of fluoroquinolone resistance is warranted for reconfirming novel and established molecular patterns for therapeutic reappraisal and for novel-drug targets. This review explores the antimicrobial resistance and its molecular mechanisms, as well as novel drugs in the therapy of enteric fever.

Fourteen strains of S. Typhi (n=13) and S. Paratyphi A (n=1) resistant to ciprofloxacin were compared with 30 ciprofloxacin decreased-susceptibility strains on the basis of qnr plasmid analysis, and nucleotide substitutions at gyrA, gyrB, parC and parE. In ciprofloxacin-resistant strains, five S. Typhi and a single S. Paratyphi A showed triple mutations in gyrA (Ser83-->Phe, Asp87-->Asn, Glu133-->Gly) and a novel mutation outside the quinolone resistance determining region (QRDR) (Met52-->Leu). Novel mutations were also discovered in an isolate (minimum inhibitory concentration 8 microg/ml) in gyrA gene Asp76-->Asn and outside the QRDR Leu44-->Ile. Out of 30 isolates with reduced susceptibility, single mutation was found in 12 strains only. Genes encoding qnr plasmid (qnr A, qnr B, AAC1-F) were not detected in ciprofloxacin-resistant or decreased-susceptibility strains. Antimicrobial surveillance coupled with molecular analysis of fluoroquinolone resistance is warranted for reconfirming novel and established molecular patterns of resistance, which is quintessential for reappraisal of enteric fever therapeutics.

The therapeutic alternatives available for use against ciprofloxacin-resistant enteric fever isolates in an endemic area are limited. The antibiotics currently available are the quinolones, thirdgeneration cephalosporins and conventional first-line drugs. In this study, the MICs of various newer drugs were determined for 31 ciprofloxacin-resistant enteric fever isolates (26 Salmonella enterica serovar Typhi and 5 S. enterica serovar Paratyphi A). MICs for ciprofloxacin, ofloxacin, gatifloxacin, levofloxacin, cefotaxime, cefixime, cefepime and azithromycin were determined using Etest strips and the agar dilution method. By Etest, all of the ciprofloxacin-resistant isolates had ciprofloxacin MICs ¢32 mg ml with the other quinolones (92-100 %) in S. Typhi. The rise in MIC levels of these antimicrobials is a matter for serious concern.

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%) Staphylococcus aureus (23.5%), Klebsiella pneumoniae (20.5%) and Haemophilus influenzae (8.8%). 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.

Antimicrobial resistance in Salmonella spp. is of grave concern, more so in quinolone-resistant and extended-spectrum b-lactamase (ESBL)-producing isolates that cause complicated infections. The MIC of azithromycin, ciprofloxacin, cefixime, cefepime, ceftriaxone, gatifloxacin, imipenem, levofloxacin, meropenem and ofloxacin (E-test strip) and tigecycline and faropenem (agar dilution) against 210 Salmonella spp. was determined. MIC 90 (defined as the antimicrobial concentration that inhibited growth of 90 % of the strains) of the carbapenems (imipenem and meropenem) for Salmonella Typhi and Salmonella Paratyphi A was 0.064 mg ml "1 . MIC 90 of faropenem was 0.25 mg ml "1 for S. Typhi, S. Paratyphi A and Salmonella Typhimurium. The MIC 90 of azithromycin for all Salmonella spp. ranged from 8 to 16 mg ml "1. Tigecycline showed an MIC 90 of 2 mg ml "1 for S. Typhi, 1 mg ml "1 for S. Paratyphi A and 4 mg ml "1 for S.Typhimurium. We concluded that tigecycline and the carbapenems are likely to have roles in the final stage of treatment of quinolone-resistant and ESBL-producing multidrug-resistant salmonellae.

BackgroundThe aim of this multicentric prospective study in India was to assess the value of several microbiological tools that contribute to the diagnosis of tuberculosis (TB) according to HIV status.MethodsStandard microbiological tools on individual specimens were analyzed.ResultsAmong the 807 patients with active TB, 131 were HIV-infected, 316 HIV-uninfected and 360 had HIV-unknown status. Among the 980 non-active TB subjects, 559 were at low risk and 421 were at high risk of M. tuberculosis (Mtb) exposure. Sensitivity of smear microscopy (SM) was significantly lower in HIV-infected (42.2%) than HIV-uninfected (75.9%) (p = 0.0001) and HIV-unknown pulmonary TB patients (61.4%) (p = 0.004). Specificity was 94.5% in non-TB patients and 100% in health care workers (HCW) and healthy family contacts. Automated liquid culture has significantly higher diagnostic performances than solid culture, measured by sensitivity (74.7% vs. 55.9%) (p = 0.0001) and shorter median time to detection (TTD) (12.0 vs. 34.0 days) (p = 0.0001). Specificity was 100% in HCW and cured-TB patients, but was lower in non-TB patients (89%) due to isolation of Mycobacteria other than tuberculosis (MOTT). TTD by both methods was related to AFB score. Contamination rate was low (1.4%). AccuProbe hybridization technique detected Mtb in almost all culture-positive specimens, but MOTT were found in 4.7% with a significantly higher frequency in HIV-infected (15%) than HIV-uninfected TB patients (0.5%) (p = 0.0007). Pre-test classification significantly increased the diagnostic value of all microbiological tests in pulmonary TB patients (p<0.0001) but to a lesser degree in extrapulmonary TB patients.ConclusionsConventional microbiological tools led to results similar to those already described in India special features for HIV-infected TB patients included lower detection by SM and culture. New microbiological assays, such as the automated liquid culture system, showed increased accuracy and speed of detection.