Induction of clindamycin resistance in erythromycin-resistant, clindamycin susceptible and methicillin-resistant clinical Staphylococcal isolates

To demonstrate the in vitro ability of erythromycin to induce clindamycin in erythromycin resistant and clindamycin susceptible clinical isolates of Staphylococci. We studied 291 clinical isolates of erythromycin-resistant [ER-R] clindamycin-susceptible Staphylococci [CL-S] at Almana General Hospitals, Al-Khobar, Dammam, Saudi Arabia during the period from June 2004 to May 2005. The isolates included 70 Staphylococcus aureus, 81 Methicillin Resistant Staphylococcus aureus [MRSA] and 140 coagulase-negative Staphylococci [CNS]. We examined these isolates for inducible clindamycin resistance [ICR] by erythromycin induction test using double disc susceptibility test [D-test]. Strains producing ICR show flattening of the clindamycin disc zone adjacent to the erythromycin disc. Of the 291 ER Staphylococci studied, 82 [28%] demonstrated constitutive clindamycin resistance [2 [2.9%] S. aureus, 43 [53%] MRSA and 37 [26%] CNS]. Inducible clindamycin resistance was demonstrated in 113 [38.8%] of Staphylococcal isolates, including 84 [28.9%] from adult patients and 29 [10%] from pediatric patients. The incidence of ICR was 49 [70%] for S. aureus, 35 [43%] for MRSA and 29 [20.7]% for CNS. Overall, 96 [33%] of the isolates remained susceptible to clindamycin and were negative for clindamycin induction [19 [27%] S. aureus, 3 [3.7%] MRSA and 74 [52.8%] CNS]. We conclude that a significant number of ER-R CL-S staphylococcal isolates studied were positive for ICR. These isolates should be reported as clindamycin resistant. Given the high rate of inducible resistance to clindamycin in the staphylococcal isolates, we recommend that microbiology laboratories perform erythromycin induction test on all ER-R CL-S staphylococcal isolates prior to reporting clindamycin susceptibility

Prevalence of extended spectrum beta lactamase among multidrug resistant gram-negative isolates from a general hospital in Saudi Arabia

To determine the prevalence of extended spectrum b-lactamase [ESBL] among multidrug resistant isolates of enterobacteriaceae and non-fermenting gram-negative bacilli. This study was carried out at the Almana General Hospital, Eastern Province, Kingdom of Saudi Arabia, during the period March 2002 through to June 2003. Multidrug resistant gram-negative isolates from patients admitted to the surgical, medical, pediatric, long-term care and intensive care units were studied for the presence of the ESBL enzyme. A total of 3231 gram-negative organisms were studied for the presence of multidrug resistance and ESBLs. Of these, 197 [6%] isolates were multidrug resistant [MDR], and 156 [4.8%] were positive for ESBL. Seventy nine percent of the MDR strains were positive for ESBL. The most frequent isolates were Escherichia coli [1116] and Klebsiella pneumoniae [687] and ESBL was detected in 72 [6.5%] and 37 [5.4%] of these isolates. The MDR strains that produced ESBL were most commonly isolated from surgical care patients with diabetic fascitis [83%] and patients with indwelling Foley's catheter [79%]. Extended spectrm b-lactamase producing strains showed the highest susceptibility to imipenem and meropenem [86%]. The non-b-lactam antibiotics with greatest activity against these ESBL strains in vitro were ciprofloxacin [72%], amikacin [70%], tobramycin [67%] and gentamicin [56%]. The majority [79%] of the MDR enterobacteriaceae and non-fermenting gram-negative bacilli tested over 15-months were positive for ESBL. Imipenem, meropenem, ciprofloxacin and amikacin showed the highest activity against these ESBL-producing organisms. Due to the growing problem of infection with ESBL-producing bacteria, which are frequently resistant to many classes of antibiotics resulting in difficult-to-treat infections, clinicians need to be familiar with the clinical significance of these enzymes and potential strategies for dealing with them

Costs and benefits of varicella screening and vaccination for healthcare workers at a general hospital

To demonstrate the costs and benefits of screening and vaccinating varicella-susceptible healthcare personnel at a general hospital with live attenuated varicella-zoster virus vaccine. Screening of healthcare workers at Almana General Hospital, Al-Khobar, Dammam for varicella-zoster antibody by indirect fluorescent antibody. Out of 757 healthcare workers, 511 [62.5%] had a definite history of varicella-zoster virus infection in the past. Of 161 healthcare workers with no history of varicella-zoster virus infection, 129 [80%] were positive for varicella-zoster antibody when tested by indirect fluorescent antibody. There were 28 cases of chickenpox among hospital staff in one year, and they were excluded from contact with patients for 5-7 days each. Adopting varicella screening and vaccination of susceptible healthcare workers in a general hospital would be cost-effective and will result in improved patient care