The widespread use of antimicrobials has increased the occurrence of multidrug resistant microbes. The commonest mechanism of antimicrobial resistance in Enterobacteriaceae is production of β-lactamases such as metallo-β-lactamases (MBL) and extended spectrum β-lactamases (ESBL). Few studies have used a molecular approach to characterize the prevalence of β-lactamases. Here, the prevalence of different β-lactamases was characterized by performing three multiplex PCRs targeting genes similar to those described in earlier publications. Antimicrobial susceptibility tests for all isolates were performed using the agar dilution method. β-lactamase was detected in 72% of the isolates, the detection rate being 64% in 2011 and 75% in 2012. The isolates were highly resistant to carbapenems such as meropenem and imipenem and susceptible to colistin and tigecycline. In this study, 22% of isolates contained both MBL and ESBL. ESBL was detected more frequently in Escherichia coli isolates, whereas carbapenemase was detected more frequently in Klebsiella pneumoniae isolates. These findings suggest the spread of multi-resistant ESBL and MBL producers in the community. Our results have implications for patient treatment and also indicate the need for increased surveillance and molecular characterization of isolates.

BackgroundCo production of 16S rRNA methylases gene and β-Lactamase gene among Enterobacteriaceae isolates conferring resistance to both therapeutic options has serious implications for clinicians worldwide.MethodsTo study co existence of 16S rRNA methylases (armA, rmtA, rmtB, rmtC, rmtD, and npmA) and β-Lactamase (blaTEM-1, blaSHV-12, blaCTX-M-14) genes, we screened all phenotypic positive β-Lactamase producing enterobacteriaceae by polymerase chain reaction (PCR) targeting above genes. A total of 330 enterobacteriaceae strains were collected during study period out of that 218 isolates were identified phenotypically as β-Lactamase producers, which include 50 (22.9%) Escherichia coli; 92 (42.2%) Klebsiella pneumoniae, 44 (20.2%), Citrobactor freundii and 32 (14.7%) Enterobacter spp.ResultsAmong this 218, only 188 isolates harbored the resistant gene for β-Lactamase production. Major β-Lactamase producing isolates were bla TEM-1 type. 122 (56 %) isolates were found to produce any one of the 16S rRNA methylase genes. A total of 116 isolates co produced β-Lactamase and at least one 16S rRNA methylases gene Co production of armA gene was found in 26 isolates with rmtB and in 4 isolates with rmtC. The rmtA and rmtD genes were not detected in any of the tested isolates. Six isolates were positive for a 16S rRNA methylase gene alone.Conclusionβ-Lactamase producing isolates appears to coexist with 16S rRNA methylase predominantly armA and rmtB genes in the same isolate. We conclude the major β-Lactamase and 16S rRNA methylases co-producer was K. pneumoniae followed by E. coli. We suggest further work on evaluating other β-lactamases types and novel antibiotic resistance mechanisms among Enterobacteriaceae.

The present study evaluates the synergistic effect of sulbactam/tazobactam in combination with meropenem or colistin against multidrug resistant (MDR) Acinetobacter baumannii isolated from hospitalized patients from a tertiary care hospital in Saudi Arabia. During the study period, 54 multidrug and carbapenem-resistant isolates of A. baumannii isolates were collected from blood and respiratory samples of patients with ventilator-associated pneumonia or bacteremia. Microbroth checkerboard assay (CBA) and E-test were performed to look for synergistic interface of sulbactam and tazobactam with meropenem or colistin. All 54 MDR isolates of A. baumannii were resistant to carbapenem. Minimum inhibitory concentration [50/90] value against sulbactam, tazobactam, meropenem, colistin was found to be 64/128, 64/128, 64/256, and 0.5/1.0 respectively. Synergy was detected in more isolates with CBA compared to E-test. All four combinations showed significant synergistic bactericidal activity. However, the combination with colistin showed greater synergistic effect than combination with meropenem. Antagonism was not detected with any of the combinations and any method, but indifference was seen in tazobactam and colistin combination alone. A significant bactericidal effect was seen with sulbactam combination with meropenem or colistin in both methods. A combination therapy can be a choice of treatment. As colistin is known to exhibit nephrotoxicity, the combination of sulbactam and meropenem might be considered as an alternative antibiotic treatment for such multi- and extremely resistant bacteria. Yet, sample size is small in our study, so further well-designed in vitro and clinical studies on large scale should confirm our findings.

In this prospective study, consecutive isolates of Klebsiella pneumoniae were tested for different mechanisms of carbapenem resistance using the modified Hodge test (MHT), Rosco Neo-Sensitabs (ROSCO). Phenylalanine arginine beta-naphthylamide assay (PABN) inhibitor-based test was done on isolates in which the mechanism of resistance was not identifiable by the ROSCO. Among 105 selected isolates, carbapenemase production was noted in 100 (95%) by MHT and ROSCO showed 97 (92·4%) inhibition with dipicolinic acid signifying the production of MBL. PCR amplification was positive in 90 (86%) isolates for bla(NDM-1) and 46 (44%) isolates for bla(OXA-48). 54 (51%) isolates were positive for bla(CTX-M) and all belonged to bla(CTX-M) group 1. Isolates co produced bla(OXA-48) (31/105, 30%) and bla(CTX-M) (40/105, 38%) in combination with the carbapenemase (bla(NDM-1)) gene. Five colistin-resistant isolates were positive for bla(OXA-48). Eight isolates did not show inhibition with any of the inhibitor containing disks and found to be positive for bla(OXA-48). Isolates were tested for colistin-meropenem synergy and detection rate was higher by the checkerboard (48%) than E-test method (35%). Our study necessitates continuous surveillance to recognize the predominant machinery of resistance in a particular geographical region to formulate effective control measures.

Streptococcus pneumoniae causes life threatening infections and necessitate for impediment and controlling disease; to conquer this, information is needed about serotype distribution and patterns of antibiotic resistance. The present study was to determine the serotype distribution of S. pneumoniae isolated from the entire age group individual and to correlate this distribution with susceptibility. Cases of pneumococcal infections have been reviewed for serotyping and antibiotic susceptibility. Out of 117 pneumococcal isolates 45 (39%) were penicillin-resistant, 84 (72%) were erythromycin-resistant and 100% were co-trimoxazole resistant. The most frequently isolated serotypes were 23F, 19F, 14, 6B, 5, 6A, 19A and 9V. PCV7, PCV10 and PCV13 coverage was 68%, 79%, 87%, respectively. Similarly, there was similarity in PCV7 coverage for non invasive isolates (64.5%) and invasive isolates (72.2%). The study state that common pneumococcal serotypes were present in similar ways as reported in literature. A continuous survey of pneumococcal infected population is requirement and necessity for success of vaccination.