Extended Spectrum Beta-lactamase Detection in Gram-negative Bacilli of Nosocomial Origin

Prevalence of multi-drug resistant <em>Pseudomonas aeruginosa</em> isolated from selected residential sewages in Dutsin-Ma, Katsina State, Nigeria

The global surge in Multidrug resistant (MDR) bacteria is an issue of great concern. Pseudomonas aeruginosa has been impli- cated in several nosocomial infections, where it has caused grave complications in immunocompromised patients. This is the first study to report the prevalence of MDR P. aeruginosa isolated from residential sewage in Dutsin-Ma, Katsina State, Nigeria. Pseudomonads count, isolation, biochemical characterization and antibiogram were carried out using standard microbiological pro- cedures. This study examined sixty (60) samples from selected res- idential sewage in the study site collected at different intervals between July and September 2021. A total of 40 (66.7%) P. aeruginosa were isolated from the analyzed sewage samples. The high- est (2.84x104) pseudomonad count was recorded from sewage samples collected from Kadangaru. Pseudomonas aeruginosa isolates from this sample site showed the highest (100%) resistance to cephalosporins (cefuroxime) and nitrofurantoin. Similarly, isolates from Miami area also demonstrated the highest (95%) resistance to a cephalosporin (ceftazidime). All (100%) isolates used in this study showed MDR resistance to tested antibiotics. The occurrence of MDR P. aeruginosa from a residential sewage site that may con- taminate drinking water sources in the study area is of public health threat to the inhabitants. Surveillance and molecular epi- demiology of antibiotics resistant bacteria are urgently needed in the study area.

Biotyping, Virulotyping and Biofilm Formation Ability of ESBL-Klebsiella pneumoniae Isolates from Nosocomial Infections

The aim of this study was to investigate the frequency, molecular characterization, virulence genes, resistance genes and antimicrobial profile of nosocomial extended spectrum beta lactamase producing Klebsiella species. A total of 22 (12.2%) K. pneumoniae strains were isolated from 180 clinical samples collected from hospitalized patients in Egypt. K. pneumoniae biotypes were B1 (72.8%), B3 (13.6%) and B4 (13.6%). The isolates were classified for the capsular serotypes, 86.4% (20/22) were of K1 serotype, while only two isolates (13.64%) were of K2 serotype. Hypermucoviscous K. pneumoniae isolates accounted for 68.2%. Biofilm formation ability of K. pneumoniae was determined by microtitre plate method. The majority of the isolates (40.9%) were moderate biofilm producers, while 27.3% were strong biofilm producers. All K. pneumoniae strains were positive for fimH and traT genes, while magA was identified in only 63.6% of the isolates. The antibiotic susceptibility profile of the isolates (n=22) was determined by the disc diffusion technique using 23 different antibiotics. Streptomycin and imipenem are the most effective antibiotics against 22 tested K. pneumoniae isolates with sensitivity rates of 63.64% and 54.54%, respectively. All tested K. pneumoniae isolates showed high resistance to amoxicillin∕clavulanate (100%), cefuroxime (100%) and ceftazidime (95.45%). Extended spectrum beta lactamases (ESBL) production and the presence of ESBL related genes were tested in the isolates. All the isolates tested positive for blaVIM, NDM1, and blaTEM, while only 81.8 percent tested positive for the blaSHV gene. Increasing antimicrobial resistance in K. pneumoniae causing nosocomial infections limits the use of antimicrobial agents for treatment. Furthermore, the spread of biofilm, multiple drug resistant and ESBL-producing K. pneumoniae isolates is a public threat for hospitalized patients.

Genetic relatedness in extended-spectrum beta-lactamase-producing Escherichia coli from clinical isolates using enterobacterial repetitive intergenic consensus polymerase chain reaction

OBJECTIVES

The aim of this study is to determine the genetic relatedness of extended-spectrum beta-lactamases (ESBL)-producing Escherichia coli using the enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) technique.

METHODS

Suspected Gram-negative bacteria with their identities from the clinical samples were confirmed using Microgen GN-A-ID Kit. The double-disc synergy test was used to confirm for ESBL-producing E. coli. The susceptibility of the organisms was tested against eleven antimicrobial agents. A singleplex PCR assay was carried out targeting TEM, SHV, CTX-M, and OXA. ERIC-PCR performed, and band patterns obtained were visually evaluated. A dendrogram of the ERIC-PCR fingerprint pattern was done with the aid of DendroUPGMA using the cluster method.

RESULTS

Of the 576 clinical samples collected, 23 isolates were confirmed E. coli, and all (100%) are ESBL producers. The highest antibiotic resistance rate was recorded in cefixime (95.6%), and the least was amikacin (17.4%). The predominant ESBL gene is blaTEM genes (95.6%). Gel analysis of ERIC-PCR revealed 1-6 bands. The profiles of the ERIC-PCR differentiated the 23 E. coli isolates into four ERIC cluster types.

CONCLUSION

More than 80% of the isolates are sensitive to amikacin, with greater than 95% harboring blaTEM genes. Overall, ERIC obtained from the clinical specimens indicated some evidence in the genetic relatedness of the ESBL genes among E. coli isolates.

Uncovering Differences in Virulence Markers Associated with Achromobacter Species of CF and Non-CF Origin

Achromobacter spp. are recognized as emerging pathogens in hospitalized as well as in cystic fibrosis (CF) patients. From 2012 to 2015, we collected 69 clinical isolates (41 patient) of Achromobacter spp. from 13 patients with CF (CF isolates, n = 32) and 28 patients receiving care for other health conditions (non-CF isolates, n = 37). Molecular epidemiology and virulence potential of isolates were examined. Antimicrobial susceptibility, motility, ability to form biofilms and binding affinity to mucin, collagen, and fibronectin were tested to assess their virulence traits. The nrdA gene sequencing showed that A. xylosoxidans was the most prevalent species in both CF and non-CF patients. CF patients were also colonized with A. dolens/A. ruhlandii, A. insuavis, and A. spiritinus strains while non-CF group was somewhat less heterogenous, although A. insuavis, A. insolitus, and A. piechaudii strains were detected beside A. xylosoxidans. Three strains displayed clonal distribution, one among patients from the CF group and two among non-CF patients. No significant differences in susceptibility to antimicrobials were observed between CF and non-CF patients. About one third of the isolates were classified as strong biofilm producers, and the proportion of CF and non-CF isolates with the ability to form biofilm was almost identical. CF isolates were less motile compared to the non-CF group and no correlation was found between swimming phenotype and biofilm formation. On the other hand, CF isolates exhibited higher affinity to bind mucin, collagen, and fibronectin. In generall, CF isolates from our study exhibited in vitro properties that could be of importance for the colonization of CF patients.

Environmental waters and blaNDM-1 in Belgrade, Serbia: endemicity questioned

New Delhi metallo-beta-lactamase-1 (NDM-1) will soon become the most commonly isolated and distributed metallo-beta-lactamase worldwide due to its rapid international dissemination and its ability to be expressed by numerous Gram-negative pathogens. NDM-positive bacteria pose a significant public health threat in the Indian subcontinent and the Balkans, which have been designated as endemic regions. Our study was focused on urban rivers, a lake and springheads as a potential source of NDM-1-producing strains in Serbia, but also as a source of other metallo-beta-lactamases and extended-spectrum beta-lactamase (ESBL) producing bacteria. A total of 69 beta-lactam resistant isolates, belonging to 12 bacterial genera, were collected from 8 out of 10 different locations in Belgrade, of which the most were from a popular recreational site, Ada Ciganlija Lake. Phenotypic tests revealed 7 (10.14%) ESBL-producing isolates and 39 (56.52%) isolates resistant to imipenem, of which 32 were positive for metallo-beta-lactamase (MBL) production. PCR and sequencing revealed the presence of genetic determinants for SHV (3 isolates), DHA-1 (1 isolate) and CMY-2 (1 isolate) beta-lactamases. However, we did not detect any NDM-1-producing strains (previously described cases of NDM-1 from Serbia were limited to Belgrade), so we propose that Serbian NDM-1 is in fact a transplant and a nosocomial, rather than an environmental, issue and that Serbia is not an endemic region for NDM-1.

Antibiotic sensitivity pattern of bacterial pathogens in the intensive care unit of Fatmawati Hospital, Indonesia

OBJECTIVE

To evaluate the sensitivity pattern of bacterial pathogens in the intensive care unit (ICU) of a tertiary care of Fatmawati Hospital Jakarta Indonesia.

METHODS

A cross sectional retrospective study of bacterial pathogen was carried out on a total of 722 patients that were admitted to the ICU of Fatmawati Hospital Jakarta Indonesia during January 2009 to March 2010. All bacteria were identified by standard microbiologic methods, and their antibiotic susceptibility testing was performed using disk diffusion method.

RESULTS

Specimens were collected from 385 patients who were given antimicrobial treatment, of which 249 (64.68%) were cultured positive and 136 (35.32%) were negative. The most predominant isolate was Pseudomonas aeruginosa (P. aeruginosa) (26.5%) followed by Klebsiella pneumoniae (K. pneumoniae) (15.3%) and Staphylococcus epidermidis (14.9%). P. aeruginosa isolates showed high rate of resistance to cephalexin (95.3%), cefotaxime (64.1%), and ceftriaxone (60.9%). Amikacin was the most effective (84.4%) antibiotic against P. aeruginosa followed by imipenem (81.2%), and meropenem (75.0%). K. pneumoniae showed resistance to cephalexin (86.5%), ceftriaxone (75.7%), ceftazidime (73.0%), cefpirome (73.0%) and cefotaxime (67.9%), respectively.

CONCLUSIONS

Most bacteria isolated from ICU of Fatmawati Hospital Jakarta Indonesia were resistant to the third generation of cephalosporins, and quinolone antibiotics. Regular surveillance of antibiotic susceptibility patterns is very important for setting orders to guide the clinician in choosing empirical or directed therapy of infected patients.

Detection of Ambler class A, B and D ß-lactamases among Pseudomonas aeruginosa and Acinetobacter baumannii clinical isolates from burn patients

In this study, we evaluated the existence of classes A, B and D ß-lactamases among Pseudomonas aeruginosa (P.aeruginosa) and Acinetobacter baumannii (A.baumannii) strains isolated from burn patients in Tehran during the years 2012 and 2013. From these strains, the frequency of MBL (metallo-beta-lactamase) and ESBL (extended-spectrum beta-lactamase) producers were evaluated using CDDT (Combined Disk Diffusion Tests). The prevalence of some related genes, including blaIMP, blaVIM, blaSPM, blaKPC, blaGIM, blaDIM, blaBIC, blaOXA-48, blaCTX-M-15 and blaNDM genes, was evaluated using PCR and sequencing methods. Of the 75 non-fermenter isolates, 47 P.aeruginosa and 28 A.baumannii were isolated and identified. A high rate of resistance to common antibiotics was detected among A.baumannii isolates in particular, showing 100% resistance to 9 tested antibiotics. CDDT showed that 21 (28%) and 25 (34.25%) of the non-fermenter isolates were ESBL and MBL producers respectively. The prevalence of blaCTX-M-15 and blaIMP genes among the 75 non-fermenter isolates was 7 (9.3%) and 1 (1.3%), respectively. Fortunately, no other genes were detected in either of the non-fermenters. The mortality rate due to MBL-producing isolates was 5 (20%). This study showed specific resistance genes exist among some MBL and ESBL gram-negative non-fermenters which were isolated from burn patients in Tehran.

Prevalence and Genotypic Characterization of Extended-Spectrum Beta-Lactamases Produced by Gram Negative Bacilli at a Tertiary Care Hospital in Rural South Western Uganda

AIM

To determine the prevalence and genotypic characterisation of extended spectrum beta-lactamases produced by gram negative bacilli isolated at Mbarara Regional Referral Hospital (MRRH).

SAMPLES

Gram negative clinical isolates.

STUDY DESIGN

Laboratory-based descriptive cross-sectional study.

PLACE AND DURATION OF THE STUDY

MRRH, June and August 2012.

METHODS

Gram negative clinical isolates were sub cultured, and identified using biochemical tests. They were screened for ESBL by using oxyimino-cephalosporins and confirmed by double disc synergy Genotyping was performed using the PCR for TEM, SHV and CTX-M. Susceptibility pattern for the extended spectrum beta-lactamases, (ESBL) - positive isolates to other antibiotic classes was performed by the Kirby Bauer Technique.

RESULTS

A total of 484 isolates were included in the study. The commonest ESBL producers were Escherichia coli (34%), followed by unidentified coliforms (19.3%) and Klebsiella spp. (12.7%). Phenotypically, 88/484 were ESBL producers while genotypically 213/ 484 possessed ESBL genes. The ESBL genes were bla_CTX-M (146; 70%), bla_SHV (72; 34%) and bla_TEM (100; 47%). 87of 213 isolates expressed more than one ESBL gene. Of these 36 (7.4%) produced bla_CTX-M/bla_SHV, 28 (5.8%) blaCTX-M /blaTEM, 4 (0.8%) blaSHV/ blaTEM and 19 (3.9%) blaCTX-M/blaSHV/blaTEM. Sixty two (16%) were phenotypically and genotypically positive, 12 (3%) of the isolates were phenotypically positive but genotypically negative and 140 (37%) isolates were phenotypically negative but genotypically positive. The ESBL producers were highly susceptible to imipenem (95%), nitrofurantoin (66%) but less susceptible to ampicillin (4%) and ticarcillin (7%).

CONCLUSION

ESBL production among the Gram-negative clinical isolates at MRRH is very high with several isolates possessing multiple genes. The ESBL producers are highly susceptible to imipenem, but very resistant to ciprofloxacin.

Phenotypic characterization of ESBL producing Enterobacter cloacae among children

Objective: The emergence of ESBL producing Enterobacter cloacae in clinical isolates is posing a serious threat for treating nosocomial infections. The aim of the study was to determine the frequency of extended spectrum β-lactamase (ESBL) producing Enterobacter cloacae and to compare the phenotypic methods used for the characterization of ESBL producing strains.

Methodology: This cross sectional observational study was conducted during April 2011 to March 2012 at Microbiology department of The Children’s Hospital and Institute of Child Health, Lahore. A total number of 20,257 various clinical samples were analyzed during the study period. Enterobacter cloacae were identified using API 20E system and ESBL detection was carried out using double-disk synergy test (DDST) and CLSI confirmatory test.

Results:Enterobacter cloacae were isolated from 221 samples, out of which 33 (14.93%) were ESBL producers and 188 (85.07%) were non-ESBL producers. The gender distribution of ESBL producing Enterobacter cloacae was 21 (63.6%) in males and 12 (36.4%) in females. Highest frequency (63%) of ESBL producing Enterobacter cloacae was detected in blood samples. Comparison of DDST and CLSI confirmatory test showed that 25 (75.75%) isolates were characterized by DDST and 33 (100%) using CLSI confirmatory test.

Conclusion: The present study shows moderately high frequency of ESBL producing Enterobacter cloacae among children. DDST was found to be less efficient in ESBL detection as compared to CLSI confirmatory test.

Profile of infective microorganisms causing ventilator-associated pneumonia: A clinical study from resource limited intensive care unit

Background:

Ventilator-associated pneumonia (VAP) is the most common cause of hospital acquired infection and death among patients admitted in ICU. Microorganisms responsible for VAP vary from place to place. Gram-negative bacteria (GNB) have emerged as a major group of pathogen causing VAP and over the years carbapenem group of antibiotics has emerged as one of the important antibiotics used in the critically ill patients. There have been reports of increased occurrence of infection by carbapenem-resistant bacteria in health care settings in recent times.

Aim:

The aim of the study was to assess the incidence of VAP, their microbiological profile with reference to carbapenemase producing GNB in the intensive care unit of a tertiary care hospital, their relation to initial emperical antibiotic therapy, sensitivity patterns, and outcome.

Materials and Methods:

This prospective study was carried out over the period of 1 year (July 2010-June 2011) on 100 randomly selected patients above the age of 18 years admitted in the emergency/ICU and requiring intubation and mechanical ventilation for more than 72 hours. The diagnosis of VAP was established on the basis of clinical and radiological parameters as per Centre of Disease Centres (CDC) guidelines. A baseline sample was obtained after initial endotracheal intubation. Thereafter, the culture sent on the first day of occurrence of clinical sign of VAP. Culture was done on blood agar and MacConkey agar. All imipenem-resistant strains were further confirmed by Modified Hodge test and combined disc for confirmation of respective carbapenemase.

Results:

Incidence of VAP was found to be 51%. GNB mainly Citrobacter 28 (52.83%) and Klebsiella pneumoniae 7 (13.21%), were the most commonly isolated pathogens. The prevalence of carbapenemase-producing GNB was alarmingly high 24/50 (48%). The entire carbapenemase producers showed high degree of cross resistance to antibiotics with some sensitivity to Polymyxin B (94 %) and Tigecycline (96%)

Conclusion:

High incidence of VAP and the potential carbapenemase-producing GNB are real threat in our ICU. The emergence of microorganisms known for its inherent resistance among most of the common first-line antibiotics calls for a alarm in all upcoming tertiary care hospitals.

The Beta Lactam Antibiotics as an Empirical Therapy in a Developing Country: An Update on Their Current Status and Recommendations to Counter the Resistance against Them

In a developing country like India, where the patients have to bear the cost of their healthcare, the microbiological culture and the sensitivity testing of each and every infection is not feasible. Moreover, there are lacunae in the data storage, management and the sharing of knowledge with respect to the microorganisms which are prevalent in the local geographical area and with respect to the antibiotics which are effective against them. Thus, an empirical therapy for treating infections is imperative in such a setting. The beta lactam antibiotics have been widely used for the empirical treatment of infections since the the discovery of penicillin. Many generations of beta lactams have been launched with, the claims of a higher sensitivity and less resistance, but their sensitivity has drastically decreased over time. Thus, the preference for beta lactams, especially the cephalosporins, as an empirical therapy, among the prescribers was justified initially, but the current sensitivity patterns do not support their empirical use in hospital and community acquired infections. There is a need for increasing the awareness and the attitudinal change among the prescribers, screening of the antibiotic prescriptions, the strict implementation of antibiotic policies in hospital settings, restricting the hospital supplies and avoiding the prescriptions of beta lactams, a regular census of the local sensitivity patterns to formulate and update the antibiotic policies, upgradation of the laboratory facilities for a better and faster detection of the isolates, proper collection, analyses and sharing of the data and the encouragement of the research and development of newer antibiotics with novel mechanisms of action.

Epidemiological expansion, structural studies, and clinical challenges of new β-lactamases from gram-negative bacteria

β-Lactamase evolution presents to the infectious disease community a major challenge in the treatment of infections caused by multidrug-resistant gram-negative bacteria. Because over 1,000 of these naturally occurring β-lactamases exist, attempts to correlate structure and function have become daunting. Although new enzymes in the extended-spectrum β-lactamase (ESBL) families are frequently identified, the older CTX-M-14 and CTX-M-15 enzymes have become the most prevalent ESBLs in global surveillance. Carbapenemases with either serine-based or zinc-facilitated hydrolysis mechanisms are posing some of the most critical problems. Most geographical regions now report KPC serine carbapenemases and the metallo-β-lactamases VIM, IMP, and NDM-1, even though NDM-1 was only recently identified. The rapid emergence of these newer enzymes, with multiple β-lactamases appearing in a single organism, makes the design of new β-lactamase inactivators or β-lactamase-stable β-lactams all the more difficult. Combination therapy will likely be required to counteract the continuing evolution of these insidious enzymes in multidrug-resistant pathogens.

Extended-spectrum Beta-lactamase Orthopedic Wound Infections in Nigeria

Background:

Extended-spectrum beta-lactamase (ESBL)-producing Gram-negative bacteria are emerging and impacting significantly on the management of patients and hospital costs. Besides, they are not being routinely sought after in diagnostic laboratories thus contributing to treatment failure.

Materials and Methods:

Bacterial isolates from wounds of 45 patients were identified using commercial identification kits and antibiotic susceptibility was evaluated by the Bauer-Kirby method. Screening and phenotypic confirmation of ESBL production were done as prescribed by the Clinical and Laboratory Standards Institute. The conjugation experiment was performed by the mating assay in broth between the ESBL producers and E. coli ATCC 25922 as the recipient.

Results:

Out of 102 Gram-negative bacteria isolated, 36 were positive for ESBL mainly of the Enterobacteriaceae family (33) and the rest were oxidase-positive bacilli (3). The predominant bacteria were Klebsiella spp. and E. coli. Others were Serratia rubidae, Citrobacter freundii, Morganella morgannii, Proteus spp., Providencia stuartii, and Enterobacter spp. There was a significant association between treatment with third-generation cephalosporins (3GCs) and isolation of ESBLs (P=0.0020). The ESBL producers were multiply resistant and moderately sensitive to colistin. The conjugation experiment showed that the ESBL gene was transferred horizontally and tetracycline, cotrimoxazole, nitrofurantoin, gentamicin, and aztreonam resistance genes were co-transferred. No mortality was recorded but the mean length of stay in the hospital was 82 days.

Conclusion:

The development and spread of ESBL among Gram-negative bacteria and possible horizontal transfer calls for concern, especially in view of treatment failure, high treatment cost, and consequent discomfort to patients.